CLIMA 2022 conference

Performance analysis of water-to-water CO2 heat pump in different compressor rotational speed

Yantong Li — 2022-05-18

Ozone layer depletion can be weakened when carbon dioxide (CO2) replaces hydrochlorofluorocarbons and chlorofluorocarbons as the refrigerant in heat pumps. Performance investigations on water-to-water CO2 heat pumps are still insufficient, especially in real life and experimental conditions. Seldom studies have reported that the compressor frequency may affect the performance of CO2 heat pumps in some degree. However, the influence of compressor frequency on the performance of the water-to-water CO2 heat pumps is still unknown. Hence, this study presented the experimental investigations on the water-towater CO2 heat pumps in different compressor frequency. The investigated CO2 heat pump is located in the Energy and Indoor Environment Laboratory in the Department of Energy and Process Engineering at Norwegian University of Science and Technology. It is mainly composed of evaporator, compressor, gas cooler, liquid separator, internal heat exchanger, and expansion valve. The compressor was produced by the Officine Mario Dorin Spa. The plate heat exchangers were applied as evaporator, gas cooler, and internal heat exchanger. The PI controller controlled the discharge pressure by adjusting the expansion valve opening. Experimental cases in which the compressor rotational speed of 1,100 rev/min and 1,300 rev/min were conducted. The coefficient of performance (COP) was calculated by measuring the compressor power and heating capacity in the gas cooler. The analysis on the water to-water CO2 heat pump COP in different measured cases was depicted. This study therefore fills the research gap on the performance of the water-to-water CO2 heat pump in different compressor rotational speed.

A study of the sensible and latent heat flux of a ceiling radiant cooling panel with superhydrophobic treatment

Ziwen Zhong — 2022-05-17

Condensation is one of the major factors that limit the application of radiant cooling systems in hot and humid areas. The need for condensation control restricts the temperature difference between a panel surface and indoor spaces, limiting the cooling capacity of the panel. Previous studies indicated that condensation risks of a ceiling radiant cooling panel can be greatly mitigated by applying superhydrophobic surface materials, making a panel usable with a lower temperature even below air dew point. We performed a case study to show how the total heat flux of a ceiling radiant cooling panel with latent heat transfer can be enhanced compared with a panel with only sensible cooling. Based on empirical methods and heat and mass analogy, as indicated by a series of natural convection condensation heat transfer experiments for a ceiling positioning superhydrophobic aluminum surface showing the condensation heat transfer of a superhydrophobic surface can be well predicted by the method, we investigated both the sensible and latent heat flux of a panel placed in the air with a temperature of 25oC and relative humidity between 40% and 70%. The case study shows an increment between 4% and 300% for the total heat flux of the panel compared with only sensible cooling under different humidity conditions.

Digital Erasmus – a pan-European approach to teaching building performance and resilient design

Christina J. Hopfe — 2022-05-17

The global COVID-19 pandemic in 2020 has forced universities to completely re-think their teaching concepts to provide safe, remote teaching of students off-campus. One of the challenges of this rapid transition is ensuring that the quality of the learning experience remains high and that students are able to engage and thrive in this new and predominantly digital environment. This project, entitled ‘Digital Erasmus - a roadmap to using building performance simulation to achieve resilient design’, responds to this context by seeking to transform the learning experience of students in built environment disciplines using a continuous digital learning cycle. This paper outlines the concept of the program and the learning objectives that it responds to, as well as some initial results highlighting the programs opportunity for students to work collaboratively and transnationally. The program is still in its infancy but it is hoped that it can serve as a template for similar future online courses that will promote safe, interdisciplinary and engaging collaboration amongst students from different universities.

‘Power gap’ in Heat Load calculations – EN12831-1 versus monitoring and simulation results

Paul Van den Bossche — 2022-05-17

For a long time, research and policy has focussed on reducing energy demand and increasing energy efficiency. However, with increasing renewable energy production, also the profile of this energy demand and the potential for demand side management needs to be assessed. Moreover, due to energy distribution restrictions, simultaneous power peaks on the grid need to be reduced or shifted. Regarding dwellings, for which heating still determines the bulk of the energy use in most of the EU, this means that reducing, or at least better characterizing and managing the heat load becomes more important. The current method for the calculation of the design heat load, according to the EN12831-1, is a static method and tends to overestimate the heat load. This research based on 50 in-situ measurement cases suggest indeed an oversizing between 25% and 100%! Further linear regression analysis and a parametric study based on dynamic building simulation was used to pinpoint possible physical causes for this ‘power gap’. Following possible causes could be identified: The standard assumes a 100% simultaneous occurrence of all worst case boundary conditions (low design outdoor temperature – relatively high wind speeds and pressures leading to high infiltration losses – no solar gains – no internal heat gains) which does not occur in reality. Furthermore, the heat load for the heat generator (at building level) is defined as a simple sum of the heat load of each individual space. This might also lead to oversizing, as infiltration or ventilation are not at their maximum in all spaces at the same time. Finally, the difference between monitoring and simulation results suggests that users adapt their behaviour below 0 °C, by reducing their comfort expectations (e.g. less window opening) or other heat loss reducing actions (e.g. keep inner doors closed so that less heat is transferred to unheated zones). Formal conclusions could be used for eventual future standard improvements.

Design of highly compact indirect evaporative coolers

Francisco Comino — 2022-05-17

Evaporative cooling units are an effective alternative to conventional air conditioning technologies, due to their high efficiency and reduced primary energy consumption. There are two main types of evaporative cooling systems: the direct evaporative cooling (DEC) system, and the indirect evaporative cooling (IEC) system. DEC is based on direct contact between air and water, while IEC is based on heat and mass transfer between two flows of air, separated by a heat transfer surface with a dry side, where only air is cooled, and a wet side, where water is evaporated into air. The main objective of the present work was to design and manufacture a highly compact indirect evaporative cooler. Firstly, a mathematical model based on ε-NTU numerical method to determine the optimal geometrical and operating parameters of an IEC system was developed. The mathematical model allowed to obtain the temperature, enthalpy and humidity distributions of the air inside the exchanger. Then, the air-cooling system was manufactured. The device consisted of a compact heat and mass exchanger, a water distributing system and an outer casing. Finally, the IEC system was studied experimentally. An experimental facility was designed to study these air-cooling systems. The cooling unit performance indicators were the cooling capacity per unit volume and per unit airflow rate. The experimental results showed that the cooling capacity per unit volume of the device was 177 kW/m3, and the cooling capacity per unit airflow rate was 10.9 kW/(m3/s). These results suggested that highly compact indirect evaporative coolers can achieve air-cooling processes with a low energy consumption and a low environmental impact.

Phase change materials in facades of buildings for solar heating and cooling

Martin Tenpierik — 2022-05-17

Phase change materials (PCMs) have already been used in buildings and building services for several decades, mostly integrated into walls or ceilings to passively increase the building’s thermal inertia, or integrated into the HVAC system for (pre-)heating or (pre-)cooling fresh air. More recently, the use of PCMs in facades is being explored for solar heating. This paper presents the results of a several years of research into the use of PCMs in rotatable Trombe walls and sun-shading for passive heating and cooling purposes. Simulations used a custom-made model of a room in Matlab/Simulink, in which all relevant heat transfer paths and mass components are accounted for. Once the behaviour of PCM was modelled, the model was connected with the optimisation platform modeFRONTIER to study the (best) performances under different scenarios. The results show that a significant reduction in the energy demand for heating and cooling can be achieved in different climates. The results also show that the shading and insulating effect of the solar wall have the highest impact on the reduction of the cooling respectively heating demand, followed by the thermal mass effect. The paper ends with the development of a prototype of a Trombe wall which was installed in an office at the Green Village (a living lab in Delft).

From Diesel to Eletric to NZEB, an Energy Performance Contract in a Hotel

João Raposo — 2022-04-21

How could a 1975 4* 220# bedroom beach hotel evolve from an old system with Diesel Boiler and cooling only chiller to become a NZEB building. An Energy Performance Contract, funded by Innovation funds, an hotel in south Portugal obtained 60% Energy reduction, a new Chiller and integrated Heat Recoveries results on eliminating diesel consumption with almost free Sanitary Hot Water in the summer and next steps to achieve a NZEB Building. Energy Performance Certificate came from D to B which is already considered NZEB in Portugal.

Ecological Refrigerant Cascade Systems Replacement in Accordance with the EU Regulations.

Tarlea Gratiela — 2022-04-23

The paper analyses ecological refrigeration cascade systems in accordance with Regulation (EU) no. 517/2014 of the European Parliament and Council of 16 April 2014. In present the cascade refrigeration plants work with refrigerants R23/ R404A. In accordance with the Regulation F-gas we will replace R23(GWP=14800) refrigerant with the new refrigerant gas R472A with the lowest GWP value (GWP=353) and R404A refrigerant with R448A. The refrigerant R472A is perfectly compatible with the commercial elements used in cascade refrigeration plants charged with R23. R472A [CO2/R32/134A] refrigerant can be used for ULT (Ultra Low Temperature) applications must reach a temperature lower than or equal to -70°C. The determination of the thermodynamic properties was performed with the help of the Refprop program. The TEWI factor analysis was performed for a cascade refrigeration installation which is located in the Laboratory of the Technical University of Civil Engineering Bucharest, Thermodynamics, Heat and Mass Transfer Department.

Study of Using R290 Refrigerant Replacement in a Heat Pump Application

Tarlea Gratiela — 2022-04-23

The study represents a new approach in the research of the advantages obtained by the water-to-water heat pumps. This original system can use a renewable energy resource, respectively groundwater, rivers or sea water and can achieve both the heating and cooling requirements of a location. The study represents also a research in the field of energy efficiency and environmental optimization of heat pumps by changing the refrigerant R407C to R290.
For testing, an open circuit water-to-water heat pump was used, with capillary evaporators in an original spiral shape able to avoid clogging, by continuous self-washing effect.
The simulations showed that the heat pump ensures a reduction of the electricity consumption and Total Equivalent warming Impact by up to 50% compared to an ordinary air conditioning system.

Energy demand with natural ventilation in unheated bedrooms, combined with balanced ventilation

Vegard Heide — 2022-04-23

In Norway, many detached houses are renovated without mechanical ventilation being installed. Many occupants prefer or accept low temperatures in bedrooms and ventilate with regular window openings all year round. In this context, a hybrid ventilation strategy combining ordinary balanced ventilation in warm zones, and natural ventilation in cooler bedrooms, could be appropriate Such a hybrid ventilation strategy might be most relevant for renovation projects where introducing ventilation ducts can be complicated and costly. The aim of this work is to investigate the energy performance using this hybrid strategy when implemented in a detached Norwegian wooden house. Detailed dynamic simulations of a case house are performed using the simulation software IDA-ICE for 2 insulation levels, and 6 different occupant behaviours. In order to reduce the uncertainty of airflow rates through open windows, simulations are done in 3 different simulation modes. Three natural ventilation strategies for bedrooms are compared to the reference with standard balanced mechanical ventilation with heat recovery. Results show that the energy performance of the investigated hybrid ventilation strategies is strongly influenced by occupant behaviour. Given an energy-conscious occupant behaviour (e.g., regarding thermal zoning), it seems possible to achieve a low energy use with natural ventilation in bedrooms. Low temperatures are frequently applied in Norwegian bedrooms so the proposed hybrid ventilation strategies could be applied to a significant share of the renovation market. However, temperature in bedrooms is strongly related to habits and culture. Therefore, the potential of hybrid ventilation can be different for other countries. With the proposed hybrid ventilation strategy, it is possible to create a night setback in the unoccupied zones with mechanical ventilation. This is a technically cheap and simple way to decrease energy use and could be investigated in further research.

Overview and assessment of radiant systems in three administrative buildings.

Emília Madarasova — 2022-04-24

Administrative buildings should provide an acceptable environment for people's work where is no excess heat, draught, noise, or low internal air temperatures. It is necessary to provide thermal well-being in each administrative building, but especially in those where the facade is of the prevailing glazed window structures.
The aim is to eliminate thermal gains and to ensure the required conditions for residence and work in administrative buildings. It is necessary to propose appropriate systems of building environment techniques. Radiant systems, low-temperature heating and high-temperature cooling, can suitably ensure an optimal environment throughout the year.
In this contribution, three applications of radiant systems in three different administrative buildings are described. In the first administrative building is the dry application system - suspension radiant covers; in the second administrative building the capillary mats are applied. The concrete core activation system has been applied in the last administrative object. The parameters of the inner environment were examined: air temperature, operating temperature, relative humidity, and airflow rate. The CO2 concentration was measured for further measurement to assess the quality of the internal air. These objective measurements and subsequently subjective evaluations of people located in the measured space were compared with the requirements of international standards for the evaluation of the internal environment.
From the measurement overview, we can say that in most measured offices, the parameters of the internal environment meet the normal values of the comfortable environment, suitable for work and residence in the workplace. During the summer season, objective evaluations corresponded to the requirements of the standard, in terms of subjective evaluation, the results were evaluated at the upper range of acceptability. For the winter period, the internal air temperature was slightly increased compared to the standards requirements, but in terms of subjective perception, the space was perceived as favorable.

Air/water heat pumps

Carola Lingua — 2022-04-24

The improvement of buildings energy efficiency represents one of the key objectives of current European policy actions, in order to guide the transition towards a low-carbon society. Indeed, nowadays, it is known that the building sector is responsible for 40% of total energy consumption and that heating is recognised as the main cause of this impact. In this context, heat pumps are recognized as promising solutions both for new constructions and for the renovation of existing buildings. For supporting the transition of the building sector, in Italy, within the “Recovery Decree” (D.L. 34/2020), which has introduced diverse social policies and financial support schemes to face the economic crisis following the COVID-19 pandemic, it is worth mentioning the current Superbonus incentive mechanism, accessible also for the installation of heat pumps. In this context, the paper aims to investigate the effectiveness of the use of air-to-water heat pumps as an alternative to traditional condensing gas boilers in residential buildings, either new or existing. Focusing on single-family houses, different models, differing in building size, envelope characteristics and heating systems were simulated, considering three different climatic zones of Italy. In detail, the energy simulations concerned two main application fields, the former considering the installation of heat pumps in new constructions, characterized by envelopes with high performances, while the latter analysing the use of heat pumps in existing buildings, without intervening on their envelopes with poor performances. The work aims to demonstrate the potential energy and environmental benefits associated with the use of heat pump solutions for space heating and domestic hot water production in both cases. The results allow stressing on the goodness of heat pump technologies in terms of energy savings (expressed in total non-renewable primary energy index) and CO2 emissions reduction, as well as their capability in improving the energy efficiency classes of the analysed buildings, only with system upgrading intervention.

Design and energy consumption assessment for a modular hospital in Romania

Ioan Silviu Doboși — 2022-04-24

The European Commission has set the goal of making Europe CO2-neutral by 2050, which requires decarbonising the building sector. Clear steps in this direction were made with the 2010 Energy Performance of Buildings Directive (EPBD), when the concept of nearly zeroenergy building (NZEB) was introduced. Currently, NZEB is a mandatory requirement for all new building in the European Union. In Romania, the authorities have established maximum values of total primary energy consumption for NZEB’s, out of which at least 30% must be covered form renewable energy sources. Achieving these requirements can be a great challenge, especially in certain building categories such as hospitals. This paper presents a study regarding the NZEB design and the energy performance assessment of a hospital building in Romania. The building in discussion is an infectious diseases hospital, whose aim is supporting potential sanitary system crisis generated by situations such as COVID-19 pandemic. The energy conservation design aimed the minimization of energy need through high thermal insulation, energy efficient windows, ventilation with heat recovery and LED lighting. Also, a renewable energy system consisting in PV panels was proposed. The energy consumption and on-site energy production was assessed
by means of monthly method. The aim is to verify if the proposed design solutions assure the achievement of the NZEB standard as it is defined in Romania.

Study regarding the impact of the new EPB standards on the energy performance evaluation

Ioan Silviu Doboși — 2022-04-24

Energy Performance of Buildings (EPB) set of standards offer an accurate methodology for calculating the energy performance of buildings, thus supporting the implementation of the EPBD. In recent years, the Romanian authorities have started the process of updating the national methodology for calculating the energy performance of buildings to align with the set of European EPB standards. At present, the energy certification of buildings in Romania is based on the Methodology for Calculating the Energy Performance of Buildings (Mc001-2006) but the new methodology has been approved and is about to enter into force. This paper proposes a comparison between the calculated energy consumption with the existing and upgraded calculation procedure. For this purpose, a residential building in Romania was investigated in terms of energy need for space heating, domestic hot water and artificial lighting. This study aims at enhancing the main differences between the two calculation procedures in terms of input data
and results.

Are bedroom air temperatures affected by temperature boosts in adjacent rooms?

Louise Christensen — 2022-04-24

Recent research has indicated that economic model predictive control (E-MPC) of residential space heating can be a significant demand response (DR) asset in district heating systems. Typical E-MPC formulation for this purpose relies on acceptance of occasionally increased indoor temperatures and the DR potential is thus limited by thermal comfort constraints. This paper reports on a field experiment on whether bedroom air temperatures are affected by temperature boosts in adjacent rooms in three case buildings. The measured bedroom air temperature was increased slightly but interviews with the residents indicate that they did not notice the increase. E-MPC in rooms adjacent to the bedroom in these or similar houses can therefore be utilised for providing DR to district heating systems.

Design of Renewable Energy Production in District Heating System

Martina Mudrá — 2022-04-24

One way to decarbonise the heat supply in buildings by using environmentally friendly and highly energy-efficient equipment and technologies that save primary energy is through existing district heating systems (DHS´s) that supply several buildings at once. Many heat sources and equipment on the heat production and distribution side of these DHS´s are beyond their service life or use fossil fuels as an energy source. It is therefore necessary to modernize such systems through highly efficient and renewable energy sources (RES´s). As the Slovak Republic has a number of DHS´s, we have designed streamlining the existing heat source operation for the DHS of the West housing estate in the town of Brezno through a cogeneration unit (CU) and water - to - water heat pumps (HP´s). The existing heat source consists of three hot water boilers burning natural gas. In addition to the existing equipment, we designed a CU and HP´s, which would be used to prepare hot water. The flow of the heating heat transfer medium passes first through the HP´s and then through the CU. If the temperature of the working medium is not sufficient, the flow of heat transfer medium will also pass through the boilers. The operation of the CU and HP´s is designed in island mode, i. e. without external connection to the electricity grid. The proposal is based on real operational data provided to us by heat supplier for the period 2016 - 2018. We have assessed the proposal from the point of view of energy and economics. From the point of view of energy, we focused on energy consumption before the design of new equipment and the expected energy consumption after the design of new equipment. From the point of view of economics, we examined the return on investment. The aim of the proposal is to point out the importance of modernizing DHS´s, as they are an ideal place for the application of high-efficiency technological equipment and equipment using renewable energy.

Experimental study on a liquid desiccant dehumidifier with a solution atomization

Soo-Jin Lee — 2022-04-24

The purpose of this study is to improve a dehumidification performance of the liquid desiccant system. The centrifugal atomization technology for spraying the solution was applied to enhance the dehumidification performance by increasing the heat and mass transfer area between the air and solution at low solution flow rate. The experimental study was performed to investigate the effect of the solution atomization for dehumidification performance of the proposed system. The measurement parameters for the test were the inlet air temperature and relative humidity, outlet air temperature and relative humidity, air volume flow rate, inlet solution temperature and density, outlet solution temperature and density, and solution mass flow rate. The dehumidification effectiveness was selected to assess the mass transfer performance of the dehumidifier with the solution atomization using the centrifugal atomizer. To compare the dehumidification performance of the proposed system and conventional packed-bed liquid desiccant system, the simulation was also conducted to estimate the dehumidification effectiveness of the reference system. The thermal load was also estimated of each system to evaluate the energy saving potential of the proposed liquid desiccant system under the conditions that show the same dehumidification performance. The experimental and simulation results indicated that the proposed system required approximately 0.012 liquid-to-gas (L/G) ratio while the reference system needed 0.5 L/G ratio for the same dehumidification effectiveness of 0.58. The most important finding of this result was that the proposed dehumidifier with the solution atomization has improved dehumidification performance at 97.6% lower L/G ratio than the conventional packed-bed type dehumidifier and the proposed system could save 72% cooling load than the reference system.

Dynamic modeling and simulation of a centrifugal chiller based on MBSE

Yoonjei Hwang — 2022-04-24

Product design by a virtual concept has always been a major subject of many of engineers and manufacturers. Issues should be how close to simulate to the real world by virtual ways. Model Based Systems Engineering (MBSE) in a digital modeling environment provides a methodology to make a virtual mock up easily. In the study, 1D/3D co-simulation was performed on a centrifugal cooling system to check how much accuracy was improved. A specific part of the fields which require to be solved in detail was modeled in 3D for co-simulation while the rest of system remained 1D model. The 1D and 3D solvers run at their respective field domains in parallel and share information. The study considered the multi physics for the components of compressor to refrect the effects of interaction between different physics. An electro magnetics, refrigerant flow & fluid dynamics, heat transfers, power electrics be calculated together to simulate them simultaneously. All 3D models converted to meta model to match time scale with 1D model. This paper shows a case study where a virtual design is successfully applied to the centrifugal chiller system, and dynamic behavior of start up at different cooling loads was simulated and investigated. It can be concluded that the approach by co-simulation as a process of MBSE be able to use to the imposed dynamic behavior on the system. The simulation results under a various load conditions showed that it maintained less than 5% compared with experimental data during from start up to the steady state, moreover, co-simulation showed
effective to get a better accuracy.

Nearly zero energy buildings with air-source heat pumps across Europe

László Zsolt Gergely — 2022-04-24

Buildings are one of the most significant energy consumers and carbon emitters. As a result, their energy efficiency is a focal subject of European legislation, including the regulation of nearly zero energy building (NZEB) constructions. NZEB definition, however, differs significantly when it comes to the national level. Consequently, residential NZEBs can be characterised with altering building physical characteristics and various energy demands, according to the location of the buildings. More than that, not only the construction, but also heating, ventilation and air conditioning (HVAC) systems can be highly dependent on the geographic, especially weather conditions. With the help of dynamic building energy performance simulation (BEPS), this study reveals how the location of a single-family house affects the operational energy consumption of heating and cooling, once from the perspective of the different national NZEB regulations and also as a result of diverse climatic conditions influencing the performance of the technical building system. For the latter, we focus on one of the most expanding heat supply solution, the air-source heat pumps. To adequately address the reduction of the environmental impacts of the building sector, besides energy consumption the study analyses operational carbon emissions as well. Results highlight that though there are differences in the requirements of the specific NZEBs, some remain to produce similar indicators in all aspects, while other Member States (MS) are appealing from certain indicators, yet much worse in carbon emission. Conclusions of the paper can be considered to improve operational energy or emission management through the legislation of the building stock, MS specifically.

Mine water geothermal energy

Lukas Oppelt — 2022-05-05

Abandoned mines offer an opportunity to provide renewable energy. Due to almost constant temperatures all year round and the large rock surfacing as heat-transferring surfaces, mine water is ideal for heating and cooling. At sites where water still has to be pumped upwards after mining has ended this water can still be used for heating or cooling supply of industry or districts e.g. in the German Ruhr area. This offers a positive additional effect of the eternal task for old mining areas. In North America and Europe in particular, a number of pilot plants have already been commissioned. These existing and planned mine water geothermal plants worldwide were studied as part of a literature search. The five largest ones have a maximum heating load of about 0.9 to 11 MW. The construction of further plants often stumbles due to the fact that mine water competes with fossil fuels e.g. natural gas or fuel oil. This is compared under economic and ecological criteria within this paper. As a result, mine water geothermal energy is cheaper to operate than fossil fuels such as oil or gas and labour costs below 6ct/kWh are possible. From an ecological point of view, CO2 emissions are reduced by at least 56 % compared to fossil fuels. One important technical risk for mine water plants is the fouling which must be taken into account: impurities in the mine water can reduce the heat transfer in the heat exchanger, which reduces the efficiency of the plant.

Designed vs. Actual Occupant Behaviour in Buildings

Zsófia Deme Bélafi — 2022-05-05

Energy efficiency and actual energy use in buildings depend on various factors. As building technology, construction quality, climate representation, advanced design tools and other non-human-related aspects are under scientific investigation and development for many decades, energy consumption in buildings started to decrease and reached a certain level. However, the desired net zero or even net positive energy consumption levels are far from reality yet in many cases. It was found that there is an essential component which is still underestimated and little researched: humans. Without understanding and appropriately representing building occupants and their needs in the design process, it seems impossible to estimate real, in-use energy consumption levels. In the 2nd half of the 20th century, occupant needs and behaviour were in the centre of many design cases. For example, prefabricated concrete block apartment buildings that were mass-produced in the Soviet era in Eastern Europe. These residential units were designed to fit the era’s occupants in all aspects. The purpose of the rigorous design process was to make sure that the mass-produced buildings will fit well the families moving in. Somewhat differently, today our goal in occupant-centric design is to improve energy efficiency and to make sure that occupants have a comfortable and easy-to-use space to live or work. However, the results and methods applied by our ancestors should be examined and from many aspects their rigorous occupant-investigations can teach us a lot and can improve our practices today. This paper analyses the process of module-design of the 50-60’s and their resulting apartment and occupant type “templates” using documents of the era and interviews with designers and other participants of that process and highlights the parts that are adaptable to today’s design practices.

Study on the efficiency of large shallow GSHP Systems

Razvan Silviu Stefana — 2022-05-06

This paper is an overview of the performances of the Shallow Ground Source Heat Pump HVAC system from ELI-NP after one year of operation. It approaches the system performances in terms of energy consumption, stability of the indoor comfort parameters and prospective of optimal control. The use of a research facility is different from a classic non- residential building. The large equipment and the large built area of the clean rooms, the high stability of the required comfort parameters imply a high consumption of energy for heating, ventilation and air conditioning. The final goal is to achieve a viable model with replication potential for general use applications (air conditioning of non-residential objectives or district centralized air conditioning). Databases resulting from the continuous real-time monitoring of the system, during 2020, have been analyzed. Deviations of data from the reference values have been interpreted to find solutions for the long-term keeping of indoor microclimate parameters at the required values. The data analysis shows that the system covers the building load / the building energy needs at a high parameters stability. The Energy Intensity Use of the ELI-NP facility (436.13 kWh/ m2/yr) is less than half of the median EUI for Technology/Science laboratories in the US (1004 kWh/ m2/yr), as published on the platform Energy Star. The use of the shallow Ground Source Heat Pump HVAC system instead of a traditional fossil fuel one, comes with estimated savings of 60% in the cost of energy consumption of buildings. The next step to follow is a higher accuracy separation of the Ground Source Heat Pump HVAC system electricity consumption. Then an optimization strategy to supply the indoor comfort parameters at the lowest possible energy consumption follows.

Analyze the energy-saving benefits of Taiwan’s existing advanced energy-saving strategies through energy simulation

Lin Feng Yi — 2022-05-06

Building energy consumption accounts for more than 30% of global energy consumption. Nearly zero energy building (nZEB) is an important strategy for energy saving and carbon reduction in the building sector. nZEB design could be separated into two key strategies: "Advanced energy-saving design", which requires highly efficient envelop components and mechanical systems, and "Renewable energy", which requires renewable generations to offset building energy uses.
Taiwan's green building evaluation system provides various advanced energy-saving design strategies to achieve energy-saving beyond the codes. The purpose of this study is to explore the energy saving benefits of Taiwan's existing advanced energy-saving design strategies, especially strategies that were typically used in green buildings. This study first established two reference building energy models, a school building and an apartment, by EnergyPlus. Additionally, we formulated a series of step-by-step advanced energy-saving strategies and determined the maximal energy-saving strategy packages, which could help the two types of buildings achieve the highest rating score in the energy-saving category in Taiwan’s green building evaluation system. Following, inputting the strategies into the two models, and simulating their energy efficiencies. The results show that: a school building, which implemented the maximal energy-saving strategy package that achieves the highest energy-saving score in green building evaluation system, could save about 56.2% energy when comparing with a typical school building that complies with the building codes. Regarding apartment building, applying the maximal energy-saving strategy package could reduce 51.3-54.2% apartment energy use when comparing with a typical apartment that complies with the building codes. Moreover, we found out that shading design affects the energy-saving benefits of using efficient building materials. School buildings are generally constructed with side corridors, and the shading effect of the side corridor would reduce the energy saving benefits of using efficient building materials.

Variation in Indoor Thermal Environmental Parameters in an Open Space Office

Arnab Chatterjee — 2022-05-06

Building energy modelling is an indispensable component of today’s design method. However, as per research findings, real-life buildings could utilize almost twice the amount of their ideal energy performance. Thus, it is important to understand the variation in the thermal environmental and thermal sensation parameters in the office buildings during real-life operation. Currently, the design of the indoor environment in buildings is performed based on the appropriate national and international standards. Based on thermal comfort requirements for mechanically conditioned buildings, the temperatures are held within narrow limits, and it is expected that the new and existing buildings adhere to them very strictly. Naturally, the question arises, instead of keeping indoor thermal conditions constant, could it be healthier to make it dynamic. A more dynamic thermal environment that goes beyond the boundaries of comfort zones may be able to provide occupants with thermal comfort, along with instances of thermal delight and positive stimulation.
To this objective, physical measurements were carried out in open office space in Lausanne, Switzerland. Data showing the overall variation of the thermal comfort parameters in space and in time have been presented. The ranges of thermal environment parameters, i.e., operative temperature, relative humidity, air speed, and local discomfort factors consisting of horizontal and vertical radiant temperature asymmetries, vertical temperature differences are discussed. Also, thermal sensation indicators, i.e., PMV and PPD are calculated from the measured values. These values are then compared with the limits specified in the standard ISO 17772. The thermal environmental parameters, particularly operative temperature, mostly lay in the Category II and III. Local discomfort factors did not exceed the limits of Category I. Thermal sensation calculation showed that the conditions were more on the cooler side since PMV was in the range of -0.2 to -1 and, the PPD was between 10-20%.

Design and optimal integration of seasonal borehole thermal energy storage in district heating and cooling networks

Massimo Fiorentini — 2022-05-06

Technologies that can close the seasonal gap between summer renewable generation and winter heating demand are crucial in reducing CO2 emissions of energy systems. Borehole thermal energy storage (BTES) systems offer an attractive solution, and their correct sizing is important for their techno-economic success. Most of the BTES design studies either employ detailed modelling and simulation techniques, which are not suitable for numerical optimization, or use significantly simplified models that do not consider the effects of operational variables. This paper proposes a BTES modelling approach and a mixed-integer bilinear programming formulation that can consider the influence of the seasonal BTES temperature swing on its capacity, thermal losses, maximum heat transfer rate and on the efficiency of connected heat pumps or chillers. This enables an accurate assessment of its integration performance in different district heating and cooling networks operated at different temperatures and with different operating modes (e.g. direct discharge of the BTES or via a heat pump). Considering a case study utilizing air sourced heat pumps under seasonally varying CO2 intensity of the electricity, the optimal design and operation of an energy system integrating a BTES and solar thermal collectors were studied. The optimization, aiming at minimizing the annual cost and CO2 emissions of the energy system, was applied to two heating network temperatures and five representative carbon prices. Results show that the optimal BTES design changed in terms of both size and operational conditions, and reductions in emissions up to 43% could be achieved compared to a standard air-source heat pumps based system.

Improving Roofs to Reduce Energy and Protect Occupants from Climate Change

Delia D’Agostino — 2022-05-05

Refurbishing existing buildings to reduce energy use is a priority worldwide to reduce greenhouse gas emissions. Millions of buildings have poorly insulated old roofs with large roof surface areas. Covered by photovoltaic (PV) arrays, these roofs could potentially provide significant renewable energy generation. Uninsulated, they increase needs for heating and cooling, while also posing health risks for top-floor occupants during summer heat waves. Such heat waves look to become increasingly common with future climate change. Suspended air conditioning from power interruptions are likely due to excessive system electric demand, earthquake or storm. We analyze an uninsulated apartment building in Milan for several scenarios to save energy while improving occupant comfort in top floor apartments. We evaluate three strategies: added roof insulation, increased roof solar reflectance and covering PV arrays above the roof. We estimate heating and cooling energy savings as well daily temperatures of a roof-adjacent top floor flat under peak summer conditions. We evaluate using current weather TMY 2018 files as well as another morphed to anticipated 2060 weather for the 90% IPCC scenario which represents extreme warming.

Development of a building thermal solution using solar renewable energy production

Eusébio Conceição — 2022-05-05

This paper presents a numerical study of the development of a thermal solution in buildings using solar renewable energy production in winter cold conditions. The Building Thermal Modelling numerical model, using solar sources through a DSF (Double Skin Facade) system, in a virtual small building, calculates the energy distribution, the internal variables and the thermal comfort level. The study considers a virtual small building equipped with two DSF systems, installed in south-facing windows, equipped with a duct system connected to an internal ventilation system, based on a mixing ventilation system. Each DSF is used to heat two or more spaces. The DSF systems are built with two transparent surfaces, forming an internal canal used to transport the warm air and to produce thermal energy, and are equipped with a set of internal lamella. The Building Thermal Modelling numerical model uses energy and mass balance integral equations for the opaque bodies, transparent bodies, internal bodies and internal air and contaminants. The study, made in winter cold conditions, in Mediterranean environment, evaluates the internal temperature and thermal comfort level evolution that the occupants are subjected. Without DSF system, the spaces equipped with windows turned south are thermally uncomfortable by positive PMV values, while the spaces equipped with windows turned North and East are thermally uncomfortable by negative PMV values. With DSF system, in general, all spaces are thermally comfortable. When the spaces with east and south facing windows are occupied the acceptable thermal comfort is verified by negative PMV values. When the north facing space is occupied the acceptable thermal comfort is verified in the noon by positive PMV values and in the final of the afternoon by negative PMV values.

Heat Pump Solutions in Renovations of Multi-Storey Buildings

Georgios Dermentzis — 2022-05-07

EU set the target for deep renovation and for phasing out gas or oil-based heating systems to reach the ambitious climate goals. Although technical solutions for the renovation of multi-story residential buildings (i.e. window replacement, thermal insulation) and boiler replacement in central energy supply concepts already exist since several years, the renovation rate has been stagnating at a low level for years (well below 1% of the stock). This means that the ambitious climate protection goals in the building sector cannot be nearly achieved. Heat pump is a key technology also for building renovations to get rid of fossil fuel based technologies such as oil and gas boilers. In this study, a method is proposed targeting serial renovations of multi-apartment buildings. Simulations are performed deriving a guide to support decision-making considering both active and passive measures. Three energy renovation levels are applied in a building, located in Innsbruck, and several heating variants are implemented, which are categorised in central (one system per building), decentral (one system per apartment) and mixed. The calculated electricity consumption of the system to supply space heating and domestic hot water as well as the auxiliaries is used to rank the different solutions, resulting in a range between 19.7 kWh/(m2 a) and 44.8 kWh/(m2 a).

Energy performance contracting as an innovative tool for financing the building renovation in Slovakia, Central Europe

Veronika Gombošová — 2022-05-07

The possibilities of using Energy Performance Contracting (EPC) are presented for Slovakia, Central Europe, including a case study performed for a building in Bratislava. The case study contained an inspection of the building, an energy audit with a proposal of energy efficiency measures, and profitability calculations for the measures. A package of suitable measures was created, and its suitability for financing by EPC was evaluated. The net present value quotient (NPVQ) was used to indicate the profitability of energy-saving measures. However, for EPC projects, the number of years in which the investment is returned is the most important. Therefore, payback was considered to be a more relevant indicator of profitability for EPC projects. With an adequate combination of energy efficiency measures, a payback period of 15 years was reached. This was acceptable considering that the building belonged to a municipality. The potential drawback of EPC is that it may not be feasible for complex renovations.

Measurement and statistical evaluation of hot water tapping profiles in (non-)residential buildings

Jonas Keuler — 2022-05-07

For a good design of water heaters, an exact knowledge of the hot water demand and its temporal distribution is required. According to DIN EN 12831-3, cumulative demand profiles must be determined that represent the daily tapping behavior in the building. In addition, knowledge of the simultaneity of tapping events and thus of the maximum tapping capacity is crucial for the use of central instantaneous water heaters (IWH), which offer advantages for the integration of regenerative heat generators. The following article presents the results of two measurement campaigns to record the domestic hot water demand in residential and non-residential buildings. In 19 water heaters of multi-family houses and 10 water heaters of non-residential buildings, data on temperature and volume of the domestic hot water and, if available, of the circulation are determined. The applied measurement technology for this purpose is presented. The recorded data is analyzed with the help of a Python tool. At first the focus is put on the necessary measuring period and the measuring interval. It is recommended to measure for at least four weeks and with a measurement interval of 5 s or less to be able to make reliable statements about load peaks for the design of IWH. Furthermore, cumulative demand profiles for multi-family houses and hotels are presented, showing that the profiles in the hotel depend on the change of guests checking in to checking out. In addition, the simultaneity of tapping events in non-residential buildings is considered and a good match with formulas for residential buildings from VDI 2072 is achieved.

Analysis of heat storage using Phase change material

Petar Nusev — 2022-05-08

In many cases heat released from some of the renewable energy sources, cannot be directly used at the time of its generation. Therefore, facilities for thermal-energy storage (TES) which would allow delayed use of the harvested heat are very important for increase of the total process efficiency. An approach to thermal-energy storage is based on the use of the latent heat of phase-change materials (PCMs). The use of PCMs as thermal storage has a theoretical advantage over the sensible one because of their high latent heat that is released or accumulated during the phase-change process.
The advantage of PCM in thermal energy storage is in applications that needs narrow temperature range of supplying and storing thermal energy. The focus of the paper is on the analysis of thermal energy storage devices based on macroencapsulated PCM. The aim of this paper is to design a latent heat storage (LHS) system with spherical modules filled with PCM. Several measurements were performed on the experimental system under constant input conditions which shows that PCMs improve the release of heat from thermal storage and can supply heat or cold at a desired temperature level for longer time periods. With the help of the computer simulation program TRNSYS, a validation of the simulation model of the latent heat storage system Type 840 was carried out with the initial and boundary conditions of the experimental system. Finally, a parameter analysis for different diameters of the spherical modules was carried out using the simulation model.

Technical-economic and environmental analysis of DHW systems in Spanish climate zones

Emilio-José Sarabia-Escriva — 2022-05-08

There are many systems on the market for domestic hot water (DHW) production. Spanish legislation requires that 60% of the energy needed to produce DHW be of renewable origin. This work analyses the economic, energy and environmental viability of seven DHW production systems installed in six climatic zones of Spain. The systems combine the equipment: gas boiler, solar collectors, heat pump, photovoltaic and electric heater. The calculation tool used for the simulations has been EnergyPlus. Results show that the system that combines solar collectors with gas boiler is the one with the lowest energy consumption and the lowest amount of emissions in all climatic zones, although in areas with intermediate and cold climates, heat pump with photovoltaic system has a similar consumption and emission level. The system with the highest consumption and emissions is the electric boiler. The total life cost analysis includes the capital cost, the annual maintenance and the energy consumption for a 15-year period. In contrast to energy results, the most economical system for the life cycle is the gas boiler for all climatic zones, due to its low capital and maintenance cost. The heat pump system is the best economic alternative to reduce energy consumption and CO2 equivalent emissions.

Cooling Performance Evaluation of an Independent Modular Air Containment with Row-based Cooling System for Data Centers

Jinkyun Cho — 2022-05-12

Owing to the rapid growth of information technology services over the past decade, data centers have become the core infrastructure for Industry 4.0. Meanwhile, the energy use of data centers has increased rapidly. In this study, a prototype of an independent module containment system that applied the row-level cooling system of a high-density data center was developed to overcome the limitations of the existing room-based cooling system and satisfy the demand for energy efficiency. The main purpose is to evaluate the cooling performance of a new in-row cooling unit package with multiple heat-transfer medium, which is a sequentially water-refrigerant-air heat exchange system in independent row-based air containment. Based on in-situ measurements, the applicability and cooling efficiency of the row-level cooling system were evaluated. While complying with the standard test method and procedure for cooling unit, the cooling performance and efficiency of the row-based cooling system was derived in connection with the actual operation situation of the data center, and the partial energy contribution was analyzed. The row-based cooling system with the multiple heat exchange in-row cooling package was found to be the better efficient in removing heat output of IT equipment based on the observations and experimental results.

Extension of the Air Distribution Network Design Optimization algorithm

Sandy Jorens — 2022-05-12

The number of requirements that heating, ventilation, and air conditioning (HVAC) systems in buildings have to fulfill continues to rise. Design engineers are being challenged to design HVAC systems with high standards of performance considering, comfort and energy efficiency. These conflicting objectives have to be achieved within a limited budget and time. Presently, considerable reliance is still placed on rules of thumb and the designer’s experience, which often results in sub-optimal designs. More than ever, there is a need for practically usable design tools. Especially in the field of centralized air distribution system design, user-friendly tools are needed to support the design engineer. In previous research, an air distribution network design (ADND) optimization algorithm was developed. The ADND algorithm is a heuristic optimization algorithm that automatically generates numerous different air distribution system configurations (i.e., ductwork layout and sizing) for non-residential buildings while minimizing the material costs. Although the ADND algorithm shows promising results, some additions are still required before the algorithm can be used in practice. Currently, the objective function is limited to the minimization of material costs. However, other objectives, e.g., minimization of energy costs or noise levels, are not yet considered. Moreover, the generated configurations are based on the aeraulic performance of only circular and rectangular ducts. Fittings and other ventilation components (e.g. silencers and diffusers) are not yet included. In this research, the ADND optimization algorithm was improved by implementing fittings (i.e., bends, reducers, tees, and cross fittings) in the optimization algorithm. A practical test case demonstrates the extended ADND optimization algorithm.

Impact of integration of electric and gas heat pumps on the final energy consumption of Belgian residential building stock

Essam Elnagar — 2022-05-12

The paper investigates the evolution of electricity-driven and gas-driven heat pumps technologies used for heating in the residential building stock in Belgium in the market. A base and predictive scenarios are considered. The base scenario includes the current share of the existing heat pumps in the Belgian market while the predictive scenario considers the increased share of the studied heating systems based on the evolution of the buildings envelope over the period 2020-2050. Two different types of heat pumps are considered, one driven by electricity which performance indicators are based on the literature, while experimental data is used for natural gas-driven heat pumps. The latter is modeled in an empirical way based on the system operating conditions and weather data. This paper presents the entire housing stock in Belgium which is divided in 752 cases. A tree structure model defining Belgian housing typology was created, characterizing Belgian residential building stock in terms of various parameters like building age, scale, level of insulation and energy vectors. A weighting factor to represent their occurrence in the existing Belgian building stock is associated to each building type. To study the impact on the load profile and the final energy consumption, the penetration of the selected heat pumps is calculated through the base and predictive scenarios. The penetration rates obtained of 67.6% and 42.7% for electricity and gas-driven HPs respectively, will allow to carry out some production planning for energy suppliers, manufacturers, and policymakers. Finally, the evolution of the sizing criteria in the future will have an impact on the penetration rates of the studied systems and must not be neglected.

Renewable energy sources used for a low energy University building

Popescu Razvan — 2022-05-12

Nowadays, the renewable energy sources have to be implemented in every new building. This paper describes the case study, and related simulations, of a university building in Romania, that has to become zero energy. Ground source heat pumps (GSHP) are ideal to be implemented in new buildings, being able to produce either heating and cooling. A good insulation is important too, to reduce the cooling and heating energetic needs. Asides active cooling, the passive cooling should be taken into account because it can lower the cooling consumption. For the domestic hot water (DHW), solar panels are taken into consideration to reduce at least 60-70% of the energy consumption, for DHW only. To be able to accomplish the goal of a near zero energy building, photovoltaic solar panels are taken into consideration, placed on the terrace of the building, the system being off-grid type. For all the dynamic simulations Designbuilder software was used, a powerful simulation tool which is able to model all renewable energy sources above mentioned. Also very detailed yearly energetic consumption is presented for all types of consumers from the building: heating, cooling, lighting, ventilation, heating, cooling and domestic hot water. Concerning ventilation, a recovery heat exchanger is used in simulations, having a 80% efficiency, also to reduce the energy consumption. The energy between building and heat pump is using fan coils in all the occupied areas,. Finally, regarding the results of the simulations, after a good insulation of the building and the implementation of the geothermal heat pump, heat recovery unit, solar thermal and solar photovoltaic solar panels, a zero energy building has been obtained. The simulated building had initially a poor energy efficiency, without proper insulation but also with old heating and cooling systems. For the characteristics of the soil measurements with thermal response test (TRT) method from Bucharest were used. Dynamical simulation is one of the best methods to simulate as accurate as possible energy consumption for several case studies, varying insulation type and thickness and different heating/cooling systems.

Integration of an innovative dual day-night technique for air conditioning of public spaces

Daniel Castro Medina — 2022-05-12

The citizen has lost his place in the streets. Also, streets have become hostile and unlivable due to climate change and unsustainable urbanization. CartujaQanat project was born to mitigate the problems discussed. CartujaQanat is an innovative urban transformation project through which the use of the street as a social activator will be promoted, improving it and involving the city's entire ecosystem in this transformation. This new model of urban governance will serve as a facilitator for introducing these models in their expansion throughout the city to gradually change the appearance and functionality of the street concept and its future evolution in the next 15 years. So, this paper shows a set of solution for climatic control of outdoor conditions for two open public spaces in Seville. These techniques guarantee thermal comfort by the implementation of passive and adaptive bioclimatic solutions. The natural element of thermal dissipation is water, which will allow the air conditioning of spaces by cooling the air. One of the keys to the project is the cooling of water using the natural technique "falling-film". The water is driven from accumulation volumes by fan nozzles on the photovoltaic panels arranged on the installation roof, forming a falling film on them. This innovative technique allows the water to be cooled through a convective-radiant effect during the night thanks to the low temperature of the sky, obtaining promising results of thermal dissipation, whose dissipation heat varies depending on the flow width and length of the film travel. The duality of the system allows the cooling of water at night and the production of electricity during the day in order to guarantee a zero-energy balance in the installation.

Experimental assessment of radiant panel for thermal conditioning of open spaces

Daniel Castro Medina — 2022-05-12

Climate change resulting from the high emission of greenhouse gases has caused a continuous increase in the Earth's temperature, leading to an increase in the demand for refrigeration in the residential sector. Added to this is the heat island effect that generates even worse microclimatic conditions. Based on this idea, the CartujaQanat project was born, which seeks to recover life on the street by providing up-to-date solutions to combine the knowledge obtained from experience, tradition, innovation, and research. These solutions include reducing solar radiation, lowering the temperature of surrounding surfaces, and lowering the air temperature. Furthermore, this study explores a new concept of radiant solution adapted to outdoor spaces to improve thermal comfort and determine the radiant effect it provides since only radiant heat flux is relevant in open spaces with a low level of confinement of air. For this, the proposed solution is evaluated in a test cell to obtain its thermal behaviour under different operating conditions. Thanks to the experimentation carried out, it has been possible to obtain an inverse model to analyze the thermal behaviour of the solution. The inverse model obtained achieves high precision in its estimates and the possibility of fractioning the radiant and convective heat flux rate, allowing to evaluate the system's different operating conditions and know the solution's impact in open spaces. Thanks to this control of surface temperatures, an increase in thermal comfort by 40% is guaranteed. In addition, it prolongs the time of use of the open space, allowing attendees to be in comfort conditions for a longer period.

SunHorizon advanced control system and proactive maintenance tool

Alejandro Martín-Crespo — 2022-05-12

Currently, buildings represent a large percentage of the energy consumption in the European Union. Increasing the introduction of renewable energy sources is becoming necessary to achieve an effective reduction of greenhouse gas emissions. SunHorizon project demonstrates the potential of combining solar appliances and heat pumps in buildings for meeting heating and cooling (H&C) demands in Europe. The energy systems are managed by an advanced Python-based control system. Using the forecast of the demand and occupancy of the building, a predictive controller calculates the optimal exploitation of resources and storage use in order to maximize the renewable energy use and cost performance. Furthermore, the control system operates in combination with a proactive maintenance tool that includes fault detection and maintenance surveillance capabilities. This tool is based on the Reliability-Centred Maintenance (RCM) strategy, which focuses on understanding the equipment failure modes, applying all the different possible maintenance strategies and considering consequences and cost of failures. To achieve this goal, several key performance indicators (KPIs) are defined, calculated in real-time operation and compared with simulation data to detect faults. When any failure is obtained, the system triggers specific alarms via web and email, hence notifying house operators or final users. KPIs are also evaluated to calculate their remaining useful life (RUL) and therefore predict future faults. The solution is applied in a building in Riga (Latvia) and the methodology beneath these tools is explained in this paper. The use of prediction for control and maintenance will allow the system to avoid wasting energy, increase self-consumption as well as to save costs on the energy bills.

Theoretical analysis on active radiant heat reflector integrated phase change material wall

Gyu-Bae Lee — 2022-05-12

Recently, as interest in increasing energy efficiency of buildings increases, a method of reducin g indoo r hea t gain and los s b y integrating phas e change material s (PCM ) into building wal ls is bein g studie d. Th e PC M is a typ e of he at storag e materi al th at ca n redu ce energy consumption o f the cooling and heating devices o f the building by absorbing o r releasing heat from outside . However , th e PCM which i s integrate d int o th e wal l o f th e buildin g canno t fully achieve thermal performance because it absorbs or releases heat according to the temperature change of the surrounding members in the wall. To solve the problem, this study proposed a new system that improves the thermal performance of the PCM integrated wall by controlling radiant heat transfer inside of the wall. The proposed system adjusts the radiant heat transfer in the wall through a n activ e radian t hea t reflecto r, which control s surface emissivit y o f th e PC M i n the design conditions. To evaluate the proposed system, a numerical analysis for 1D transient heat transfer was used based on the energy balance equation for the indoor heat gain and loss with the reference systems. The simulation was conducted with Matlab 2021a software, and weather conditions were data from the summer (Jun-August) and winter (December-February) of IWEC2 Seoul. As a result of the simulation, the proposed system confirmed that indoor heat gains and losse s wer e improve d i n al l period s compare d t o th e reference system . Th e propose d system reduced the total indoor heat gain by 33.3%-44.1% in summer and the total indoor heat loss by 14.2-29.3 in winter compared to the reference systems.

Implementation of a shallow geothermal energy system in a multi-source green building

Gavriliuc Robert — 2022-05-12

The building stock is responsible for a large share of greenhouse gas emissions (GHG) in the European Union. Major emission reductions can be achieved through changes in this sector and the building sector is crucial to achieving the EU’s reduction targets. From 2021 all buildings must respect the nZEB standard and must use a certain amount of renewable energy sources. While condensing gas boilers have lower costs these cannot provide cooling and do not use renewable energy. The best alternative is the use of geothermal heat pumps that have high efficiencies and can avoid large amounts of GHG. Currently, geothermal energy sources provide more than 15 GWth for heating and cooling in the European Union, equivalent to more than 4 Mtoe per year, whereby geothermal heat pump systems contribute to the largest part. Shallow geothermal systems are more complex to realize than conventional solutions. Critical aspects include correct design, adequate performance in operation and costs for the installation. The combination with other Renewable Energy Sources (RES) like solar energy could improve the return on investment. The main goal of this paper will be to tackle all the above-mentioned areas by developing and demonstrating the potential of shallow geothermal system to be connected in a precise and efficient way to other renewable sources systems, in particular solar thermal energy. This approach is realized by adapting hybrid solutions to reach nZEB standards through a holistic engineering, construction and controls approach. The demo-site was carried out on an energy-efficient house EFdeN House, an active single-family dwelling that was planned and built in Bucharest for academic and research purposes and it is the first Excellence Research Centre in Romania.

Thermistor ntc sensor inaccuracies impact on the hvac/r compressor performance

Adrian Anastase — 2022-05-12

Electricity consumption for thermal comfort in urban buildings is estimated to an average of 35%. The aim of this article is to evaluate, theoretically, the impact of sensors inaccuracies on the performance and efficiency of HVAC equipment. Different types of temperature and pressure sensors are considered. The measurement tolerance, from manufacturer’s technical data sheet, will be used for the theoretical evaluation of the range in which the operating point of the equipment can vary. Compressor selection software are used for evaluating theoretical COP and electrical energy consumption change in the range of sensor inaccuracies. The study evaluates theoretically the impact on performance of scroll, piston and screw compressors, considering refrigerants used in chillers (R717, R134a, R410A, R32). The operating point of the compressor is considered as normal chiller scenario, with evaporation temperature of +4oC and condensing pressure corresponding to +35oC. The conclusion of the theoretical evaluation is that resistance tolerance bigger than 1% brings a 1% or more variation of compressor’s performance.

Assessment of Use Cases Involving Data from the Energy Performance Certification Process for Buildings - From Individual Buildings to Regional Scale

Gerfried Cebrat — 2022-05-12

The main objective of this paper is to analyse use-cases which are based on data from the Energy Performance Certification (EPC) process. This data, which is often collected for compliance checks by authorities, can be used exploited for multiple purposes. The most basic service is energy consulting by engineers, based on a living document from the EPC process, depicting the buildings thermal characteristics and specification of the HVAC system. But also, the design of regional decarbonization can be data driven, and the drafting of energy policies supported, investigating effect of renovation and decarbonization incentives. When using data from EPC software export files to set up thermal building models for digital twins, peak load shifting at the individual building and district level can be initiated. A high coverage with EPC as source for digital twins can be achieved by marketing for pre-planning decarbonisation of quarters. This paper is originating from the work in the research project EPC4SES which is funded in the ERANet RegSys program and by HORIZON, and develops six use-cases and analyses strengths, weaknesses, opportunities, and threads of services making use of data from the EPC process.

Energetic Impact of Temperature Gradients in Heat Re- covery in Ventilation in Dwellings

Josué Borrajo Bastero — 2022-05-13

The installation of air-to-air heat exchangers in ventilation systems can contribute to reducing the heating demand of the building by recovering the heat from the exhaust air. When there is an active heating demand, the recovered heat becomes useful to reduce that demand. However, as the heat exchanger works independently of the heating needs of the dwelling, the recovered heat may not contribute to the reduction in the heating demand. Furthermore, the in-door temperature gradients in the various rooms/zones of the dwelling can influence the heat recovered by the ventilation system and, consequently, the useful recovered heat. A suitable method to evaluate the effect is based on dynamic multi-zone building energy simulations. In this work, a residential building typology has been modelled with eleven ventilations systems. Some of them work with fixed airflows and others are commercial smart ventilation systems with var-iable flow rates controlled by CO2, VOC and humidity sensors. Various systems do not have a heat exchanger due to their ventilation type. Still, the study was extended to those, considering that the unwasted heat as a consequence of using a smart control would be equivalent to the presence of a heat exchanger. The building was heated with two heating strategies: uniform heating in all the zones except for the attic and non-uniform heating with a specific setpoint for three different types of zones. To evaluate the impact of the heat recovery, the annual heating demand and the recovered heat are compared between scenarios with different effectivenesses for the heat ex-changer and, to evaluate the effect of the temperature gradients, the results are compared be-tween the two different heating strategies: uniform and non-uniform. The results for the case presented in this study show that centralized heat recovery systems perform better in the sce-narios with uniform heating, while distributed ventilation systems perform similarly in both heating scenarios.

Optimal dimensioning power of GSHP with district heating in an educational building

Tianchen Xue — 2022-05-13

European Union (EU) have set great goals to reduce carbon dioxide (CO2) emissions and mitigate global warming trend. In this context, energy performance of buildings should be improved by enhancing the use of renewable energy sources in heating and cooling. For that reason, a hybrid energy system where a ground source heat pump (GSHP) integrated with borehole thermal energy storage (BTES) system is used together with district heating (DH) has become increasingly popular in Finland during the last years. In those hybrid GSHP systems, GSHP is used as a primary energy source and DH is used for supplementing energy during peak heating load period in wintertime. While in summertime, the borehole field is used for free cooling and DH is providing heating energy for domestic hot water. In this study, a large educational building complex in Finland applying a hybrid energy system consisting of a GSHP and DH was modelled in IDA ICE 4.8. Three simulation cases were studied to analyze the effects of the GSHP power ratio on the whole system energy consumption and CO2 emissions. The results show the total CO2 emission obtained the minimum when the GSHP heating power ratio was 50%. However, compared to 100% district heating solution, 25% power ratio of GSHP in the hybrid system can already realize 50% reduction of CO2 emissions as the total cooling demand was fully satisfied by borehole free cooling and 98% DH consumption was reduced.

Total Cost of Ownership of Sensor Faucets in Commercial and Healthcare Construction

Marie Patterson — 2022-05-13

Owners who are pursing the construction of new commercial and healthcare buildings are very interested in the sustainability, energy efficiency, life cycle costs and cleanliness of their proposed projects. Owners are requiring designers and construction companies to develop innovative strategies to lower their utility use and total cost in their projects. One area of opportunity to meet this owner need is the decision to use either battery-powered or hardwired restroom faucets. Several construction projects of various types and locations were analyzed to determine the total cost of ownership of both types of faucets over a 12-year and 25-year timeframe. The results of the unit cost calculation showed that the battery-powered faucets had a lower cost of ownership at 12 years, while hardwired fixtures installed in intervals of six had the lower cost of ownership over 25 years. Although, when researching actual construction projects, where installation of multiple faucets in a row isn't realistic, battery-powered faucets had the lower cost of ownership over the hardwired options in both the 12-year and 25-year timeframes in all building types.

Solar hybrid collectors analysis - Experimental and numerical study

Catalina Tiberiu — 2022-05-13

The resource economy is currently a global priority and the preservation of the planet and its resources are becoming the main international objectives. In this regard, EU states must establish clear lines and long-term strategies. Also, the goal of developed countries must involve reducing emissions by 80-95% by 2050. The global economic context leads to an intense concern in the field of unconventional sources, with solar energy occupying an important place. Solar energy can be collected and transformed either into electricity using photovoltaic or thermal technologies, through the use of different types of solar thermal panels or through the use of hybrid panels (PV/T) Hybrid solar photovoltaic - thermal collectors, often known as PV/T are systems that simultaneously convert solar radiation into electricity and heat - operating in cogeneration. The paper includes experimental measurements and numerical analysis of a hybrid solar panel. A decrease in the surface of the panel was observed, thus an increase in electricity production by up to 6%. The original part is the experimental protocol used and the comparison of two solutions of energy production under the same conditions. The numerical campaign accompanies the experimental study and provide interesting data.

Insights of the DYDAS Project: The Use Case Energy

Ilaria Abbà — 2022-05-13

In the current energy transition, Renewable Energy Sources are identified as key enablers for the achievement of the ambitious European target of climate neutrality by 2050; among them, solar and wind energy play a crucial role. The evolution of production, storage and end users’ technologies goes hand in hand with the rapid development of the information sector, where High Performance Computing (HPC) infrastructures allow the exploitation of Internet of Things devices and Artificial Intelligence techniques. The use of HPCs in the energy field enables the use, processing and sharing of large volumes of energy data. The funded by the CEF TELECOM 2018 DYDAS (Dynamic Data Analytics Services) Project is carried out in the above-mentioned framework, aiming to create a collaborative platform, called DYDAS, that, using high-performing computers, will offer data, algorithms and data analysis services to a wide range of final users, both private and public. More specifically the paper will focus on the Use Case Energy, whose objective is to test and validate the DYDAS platform, by exploiting meteorological forecast techniques and using satellite information to facilitate and boost up the assessment of both energy demand and power production. Considering the strong dependency on resource availability, the localization of the resources and the related infrastructure is essential for an efficient and strategic energy planning. Therefore, the mix of traditional algorithms, climatic variables and remote sensing techniques represents an added value for supporting decision-makers in the energy planning processes at local and national scales, taking advantage of the geomatics instruments to visualize and monitor decision strategies. Given the role of electricity in the energy transition, the current paper deepens the Use Case Energy focusing on power generation from photovoltaic plants and on-shore and off-shore wind farms located in Italy. The aim of the use case is to estimate the potential local power production, by collecting information about technical features and geo-localization of real plants, and integrating them with georeferenced climatic variables, which can influence the electricity production (e.g., air temperature, solar irradiance, etc.).

Performance of a mixed-use ground source heat pump system in Stockholm

Jeffrey D. Spitler — 2022-05-13

The 6300 m2 two-story Studenthuset building at Stockholm University in Stockholm, completed in 2013, was thoroughly instrumented. Space heating and hot water are provided by a ground source heat pump (GSHP) system consisting of five 40 kW off-the-shelf water-to-water heat pumps connected to 20 boreholes of 200 m depth in hard rock. Space cooling is provided by direct cooling from the boreholes. This system has now been monitored for five years. This paper presents the results in the form of a range of performance indicators that describe the short-term and long-term system performance. Performance factors are computed for several boundaries defined by the IEA HPT Annex 52 boundary schema. Seasonal, monthly, daily, and binned performance factors for both heating and cooling operation are presented and discussed. Contrary to expectations based on thermodynamic theory, the performance is better correlated to the quantity of heating or cooling provided than it is to the exiting fluid temperatures from the ground heat exchanger. Despite being in Stockholm, the building rejects about 30% more than it extracts, leading to a minimal temperature increase over the five measured years. The analysis indicates that if operated as is, the GHE will not exceed its temperature constraints for many decades. The five-year seasonal performance factor (SPF) for combined heating and cooling is 5.2±0.2 considering only the heat pump and source-side circulating pump. However, the load-side distribution system and Legionella protection systems result in a significant decrease in the 5-year combined heating and cooling SPF at the outer boundary to 1.8±0.3.

Room-side and Plenum-side Cooling Prediction of Suspended Radiant Ceiling Panels

Jun Shinoda — 2022-05-14

Hydronic radiant ceiling panels use a chilled surface to cool a room, and their cooling capacity is normally measured in a certified test chamber. However, current measurement standards calculate the cooling capacity of a panel based on the heat carried by the circulating water, which is the sum of the heat extraction from the room and plenum. Thus, sizing the radiant system based on the cooling capacity of the panels may result in an undersized system. In this study, a series of test chamber measurements and field measurements were conducted to quantify and empirically predict the proportion of the heat extracted from the room-side to the total heat extracted by the radiant panel. The cooling capacity of suspended radiant ceiling panels was first measured in a certified test chamber, with the temperature difference between the room and plenum as the main parameter. Within the tested temperature range (plenum temperature of 24 – 28 °C, room temperature of 26 °C), the heat extracted from the room side was 77 – 92 % when the panels were insulated and decreased to 46 – 71% when they were not insulated. A simplified, empirical approach for estimating the heat extraction at both sides of the panel was proposed based on the obtained results. A field measurement was then conducted to examine the validity of the proposed methodology. Measurements were conducted in an office building located in Japan, which was equipped with radiant ceiling panels of the same type as the ones tested in the chamber measurements. Heat flux sensors were placed at both the room and plenum sides of a single radiant panel to obtain the proportion of heat extraction from the room-side. The measured room and plenum temperatures were used as input for the prediction of the room-side heat extraction ratio, and the average error of the predicted heat flux was 6%, confirming the validity of the proposed methodology.

Experimental assessment of thermal effectiveness of a regenerative indirect evaporative cooler

María Jesús Romero-Lara — 2022-05-14

Heating, ventilation and air-conditioning, HVAC, systems represent a significant energy use in Europe, around 50% of total energy use in buildings. Conventional HVAC systems are mainly based on direct expansion units, whose use of 100% outdoor air leads to high energy use. Then, different innovative and efficient air-cooling systems could be an interesting alternative to approach Nearly Zero Energy Buildings, nZEB. One of these efficient solutions is the technology of indirect evaporative cooling. This work was based on the experimental evaluation of a regenerative indirect evaporative cooler, RIEC. Several empirical tests were carried out under different inlet conditions: inlet air temperature values between 29 °C and 43 °C, TOA, and inlet air humidity ratio values between 9 g/kg and 13 g/kg,

Heath Recovery from Waste Recreational Pools Water of Thermal Baths and Medical Sanatoriums

Anna Predajnianska — 2022-05-15

In Slovakia we can find 35 thermal baths and 28 thermal healing sanatoriums that use geothermal or thermal healing water for their operation. After the use of water in these facilities, waste pool water with relatively high temperature is drained out of these facilities. This wastewater has considerable energy potential, which is used in any way. There are number of buildings in the premises of recreational and medical facilities, which are used for various purposes. Whether it is a building used by the staff of the recreational facility or by visitors. We have two options for using the energy potential of wastewater. The first option in the summer is to use waste heat to preheat cold water, which is used together with geothermal water to fill and operate of pools. The second option in the winter is to use waste heat to defrost the sidewalks within the recreational facility or use this heat in the system of active thermal protection of buildings that are part of the complex. The aim of the paper is to present more ways of using the energy potential of waste pool water, which is produced by thermal baths and medical sanatoriums and calculation results of geothermal water volume decreasing.

Heat recovery potential from ventilated passive and active facades

Mohammad Rahiminejad — 2022-05-15

A ventilated air-space behind external claddings can potentially affect the thermal performance of the entire building structure. In particular, in the Building Integrated Photovoltaic (BIPV) facades, ventilated cavities are typically present between the PV panels and the walls of the building. The airflow in the cavity can remove the generated heat behind the active external cladding, which could be eventually used as an additional source for heat recovery. In this study, the heat recovery from a ventilated air-space behind passive (wood) and active (BIPV) facades are investigated using transient simulations. The numerical model used in this study is validated against experimental measurements carried out in a building prototype located in the Smart Living Lab in Fribourg (Switzerland). The original façade is made of wooden cladding that is separated from the wall core incorporating a ventilated cavity. To study the impact of façade type on the results, the external cladding is virtually replaced with typical polycrystalline PV panels. The analyses are performed for representative days in the winter and summer of 2021 using recorded weather data on the test building. The results are examined in terms of the temperature distribution of the layers in the wall assembly, heat flux through the indoor space, airspeed in the cavity, and heat flow in the air gap. The potentials for heat recovery per day of interest are also calculated and compared. It was shown that the heat recovery from the cavity behind the BIPV façade could become equal to 5341 kWh on a representative summer day, which is considerably higher compared to the value obtained for a passive cladding. The results highlight the potential for harvesting heat from the ventilated air gaps behind passive and active facades. The outcome of this study highlights the need for the integrated vision for energy-savings at the building scale.

Repeated solar regeneration of a medium-term heat storage for a heat pump

Annemarie Lauffer — 2022-05-15

This paper deals with a heat pump system with two heat sources, a medium-term ground collector heat storage and a façade-integrated massive solar-thermal collector. Aiming at affordable system cost, a medium-term heat storage is applied instead of a seasonal heat storage. During milder phases of the heating period, the heat storage is regenerated by the solar absorber to be used as ambient heat source under frosty weather conditions. Preparing for the design of heat pump systems with multiple heat sources, the energy balance of a medium-term underground heat storage has been investigated, based on physical component models. Yearly and seasonal analyses for different absorber sizes from 7.5 to 37.8 m² lead to the following statements. In general, even for small absorber sizes solar yields during winter are sufficient for continuous operation of the heating system, with increasing average temperature of the storage for larger sizes of the solar system. Higher ground temperatures result in higher seasonal coefficients of performance of the heat pump, and in higher annual heat losses of the storage. The medium-term character of the storage is shown by the in-season heat gain contributed by the solar absorber. Finally, to assure frost-free operation of the storage the absorber size must be at least 15% of the ground collector size.

Impact of the Weather Forecast Quality on a MPCdriven Heat Pump Heating System

Sebastian Hummel — 2022-05-15

Electrically driven heat pumps offer in combination with thermal energy storage systems the potential to response to fluctuating renewable energy sources, e.g. photovoltaics. To fully exploit this flexibility and financial potential, smart predictive control strategies such as Model Predictive Control (MPC) are needed. For such a controller, weather forecast data are mandatory to perform the optimization. Several sources of weather forecast data are available with variable forecasting quality. In this study, the impact of the weather forecast quality on a realistic heat pump heating system is investigated in experiments and simulations. Therefore, the operation of a MPC strategy is carried out for a perfect forecast compared to two imperfect forecast scenarios over a consecutive period of 4 days on a Hardware-in-the-Loop test bench with a geothermal heat pump and a thermal energy storage system. In order to evaluate the benefits in real operation compared to rule-based controllers, a heat-controlled (HC) and a PV self-consumption optimized controller (PVC) are also operated on the test bench. In addition and as a validation process, all scenarios are simulated and compared to the measurement results. Compared to a standard rule-based HC strategy the PV self-consumption can be increased by using a PVC and MPC strategy by 6.2 % and 38.9 %, respectively. The accurately the weather forecasting quality is in general the higher the performance of the HP heating system. Thus, the PV self-consumption is reduced for high-quality and low-quality weather forecasts by 4.6 % and 11.1 %, respectively, compared to a perfect MPC. Even a MPC with low-quality weather forecast data can achieve higher system performance as a simple rule-based HC strategy. For achieving higher system performance by using a MPC instead of a rule-based control strategy like PVC the, forecasting quality has to be as accurate as possible.

Comparison and implementation of MPC and simple predictive control into a heat pump system

Christina Betzold — 2022-05-15

Heat pumps in combination with thermal energy storage systems offer the potential to response to fluctuating renewable energy sources, e.g. photovoltaics. To fully exploit this flexibility and financial potential, predictive control strategies are needed. Since an additional effort due to detailed knowledge and programming skills is required to create the model predictive control (MPC) strategies, a fast and easy implementation is prevented. Therefore, a second model-based approach is developed with a predictive but rule-based control. This simplified approach uses predictive models as well but energy balancing to determine the heat pump operation and the state of charge of thermal storage units throughout the day. In this paper, two predictive approaches were compared with two rule-based controls and evaluated for their potential for PV self-consumption and cost savings in annual simulations. In addition, one rule-based PV optimized control (PVC) and the predictive approaches, MPC and the simple predictive control (SPC), are implemented in the real operation in a plus energy building. In simulation, the best result is achieved by the MPC with a cost saving of 8.3 % due to a high PV energy consumption but mainly to the best efficiency with a SPF of 4.5. Despite the predictive approach of SPC, SPC and PVC achieve very similar results with cost savings of 2.5 % and 0.8 %. Since the costs of PV include taxes, these moderate cost savings are achieved. Excluding these taxes, there are significantly higher cost savings of up to 34 % for MPC. In real operation, differences between simulation results and measured data become apparent. This gap between the set point output of the simulation and the set point input of the real components poses a challenge to the implementation of efficient and cost-effective control like the MPC.

A decision-making methodology of decarbonization for a dwelling stock in France

Tianrui Ouyang — 2022-05-15

Decarbonization is a hot topic in the building sector. In response to the national ambition of carbon neutrality in 2050, a social housing company that manages about 100,000 housings in France, wants to know how to decarbonize its dwellings. This dwelling stock form a heterogeneous dynamic group with new constructions and demolitions every year. Carbon emission is mainly caused by fossil energy consumption in the building exploitation phase, especially in space heating and hot water. There are many instructions to reduce energy consumption in building exploitation phase, like the thermal insulation of building envelope, the update of equipment, the energy transition, and the sobriety of energy...But how to organize these methods to find out an optimum with the restrictions of resources? How to take the initiative in an ever-changing political and technical environment? Inspired by the discipline of “System Dynamics”, we propose a methodology to represent and simulate the intricate system of the dwelling stock, to have a better insight into how the outside impacts, like the changes in policy and technological innovation, influence the inside system of the dwelling stock, and how the inside elements interact. This methodology is composed of two aspects: The typologies of housing type and the simulation of the dwelling stock. The 100,000 housing has been classed several times independently, which is quite distinct from the traditional classification method. The simulation part is carried out in the software “Vensim” and is based on the calculation method 3CL DPE. For each scenario of outside political-technical environment, we test several options to propose a suitable integration of concrete methods to decarbonize the whole dwelling stock.

Characterization of a Constant Air Volume (CAV) Box Based on Measurements

Zakarya Kabbara — 2022-05-15

HVAC engineers are frequently challenged to design and operate ventilation systems with a high standard of performance considering comfort, energy efficiency, and indoor air quality. However, currently, most design, commissioning and control processes of ventilation systems rely on rules of thumb and engineers' experience. A simulation-based framework for informed decision-making could be an effective tool to achieve superior ventilation systems with optimal design and performance. Nevertheless, to develop such a framework, the integration of solid component models that provide insight into the system's aeraulic behavior is vital. In previous research, a simulation framework known as Air Distribution Network Design (ADND) optimization algorithm was developed. The ADND algorithm provides a basic strategy to design centralized air distribution networks. However, the method is missing some features before it can be used in practice. Currently, the method is limited to generating layout by accounting for the ductwork only. Some ventilation system components (e.g., CAV control box) are not yet integrated. This paper presents the development of a new CAV control box model that is typically used in nonresidential buildings, viz., a mechanically controlled damper that maintains airflow to a predefined fixed airflow level. The model aims to predict the aeraulic performance of the control box at any given inlet volumetric flow rate and set airflow rate (i.e., the airflow index at which the CAV box is commissioned to maintain the flow) for diameters between 125 and 250 mm. First, lab setups were built to measure pressure drops for different CAV diameters by varying the inlet airflow rates and set airflow rates. Next, the measurement data was used to develop a model of the CAV control box by training a regression model. Finally, the model was tested and validated on experimental data that was not used in the training set of the regression model. The accuracy of the CAV box model justifies its integration into the ADND algorithm and also its potential to be integrated into common building simulation frameworks. Once integrated, it can be exploited in many applications, including evaluating the performance of designs, automating the iterative balancing process, and optimizing the control strategy of ventilation systems.

Study of bioclimatic shading strategies in Seville

Teresa Rocío Palomo Amores — 2022-05-15

It is necessary to adapt urban areas to climate change through solutions that combine tradition with innovation. This need is more pronounced due to climate change and the heat island effect. This work aims to design a mitigation technique that allows recovery life on the street through an adaptive solar control solution combined with vegetation. This technique will be designed and implemented in a square in the centre of Seville (Spain). The solution is defined as a green structure where the trees are the key part. However, the trees are planted small and are grow-slowly. Urban designs based on tree growth are estimated to reach design conditions 30 years after these trees are planted. That is why an innovative urban solar control prosthesis is required that adapts between winter and summer and that allows modifying its geometry according to the growth of the trees. The design of this solution has been made by studying in detail a real case with real problems. These problems have been characterized by temperature measurements, thermographies, transects for the evaluation of the heat island, level of incident irradiation, and actual use of space. Different alternatives for the rehabilitation of the urban fabric have been studied using computational fluid dynamics (CFD) simulations in ENVI-met. The optimal solution will reduce air temperature by 1ºC and surface temperatures by up to 12ºC, increasing the number of trees reaching close to 100% of the area covered to make them the natural mitigation solution in the future. The coverage developed in this work appears as a temporary solution until the trees reach a reasonable size that generates adequate shade to allow the use of the space during the summer months. The aim is to improve the habitability of cities and regain the prominence of people in them.

Design and integration of innovative rehabilitation technique

Teresa Rocío Palomo Amores — 2022-05-15

The current commitments proposed by the European Union to mitigate the effects of climate change lead to the necessary action on the building sector. Acting on the existing building stock, improving energy efficiency becomes a key point on the road to 2030, where the role of air conditioning will change completely. Unsatisfied basic needs for energy supply characterize the energy-poor social housing districts in Spain. The energy inefficiencies of the dwellings worsen this situation. This situation is aggravated in the south of Spain, presenting a severe overheating problem in cooling, making residents outside the comfort limits a high number of hours. In these cases, conventional strategies to improve the performance of the building envelope are not enough. In this work, an innovative active roof solution of more than 2000m2 is designed and integrated in a district of social housing blocks. Said roof reduces the energy demand for conditioning through the exploitation of thermal inertia and the integration of environmental sinks, enhancing its effect with direct evaporative cooling systems through water micronization. It stands out for being a climate-adaptive design, intelligently controlled based on climate predictions and with different operating modes, which allows it to adapt to the needs of the building. The assessment of the impact of this innovative solution has been analyzed both in the pre-design phase and after the completion of the intervention, thus allowing us to know the actual improvement of the dwellings. Serving as an example of the integration of high-tech components, its objective has been to improve the energy efficiency of the housing stock, allowing it to reduce energy demand, as well as increase comfort levels for residents.

Evaluation of Building Retrofitting Alternatives Towards Zero Energy School Building in Turkey

Ayşe Özlem Dal — 2022-05-15

The building sector plays a vital role in coping with current worldwide challenges: climate change, urbanization, and environmental pollution. Building performance analysis is essential from the energy consumption, comfort, and carbon emission point of view. Different paradigms have been studied for many years, like bioclimatic architecture, sustainable architecture, green architecture, and carbon-neutral architecture. The regenerative paradigm has been a critical topic since 2016 to look toward positive impact architecture for going beyond the neutral impact. The research aims to examine the existing condition of a school building in İstanbul, Turkey, to investigate a strategy for achieving energy-efficient school building towards zero energy. The research method is based on preparing the energy model of the school and making simulations by using Design Builder software and Energy Plus software. The validated simulation is used to examine the retrofit packages for the efficiency of the school building and discuss the alternatives that are categorized as two alternatives for the insulation layer, three types of glazing alternatives, two types of the lighting system, and five alternatives for the HVAC system. By the combination of the alternatives, 111 retrofit packages are analysed. According to the comparison of the packages, the P102 scenario has the lowest results for the primary energy for electricity (P.E.E), primary energy for natural gas (P.E.N.), and the total primary energy (T.P.E) as 1.84 kWh/m², 1.51 kWh/m², and 3.35 kWh/m² thanks the integration of renewable energy systems; while the existing condition of the case study school building has 29.99 kWh/m², 63.05 kWh/m², and 93.05 kWh/m² respectively. Therefore, towards zero energy school building, the retrofit scenarios are significant to reduce the negative impact of a building on the environment by highlighting the combination of the renewable energy system and advanced HVAC system and with the integration of proper insulation thickness, efficient glazing, and lighting type. The alternatives and aspects of the research can provide a strategy for further study steps and related studies to improve the building stock towards zero energy in school buildings.

Design under uncertainty of solar hot water systems for hospitals

Antonio Atienza-Márquez — 2022-05-15

Failed designs are often behind underperforming solar hot water systems and excessive fossil fuel consumption in backup units. This paper proposed a reliable and robust method to design a solar thermal system combined with boilers for hot water preparation in a medium size-hospital hospital building with an average daily demand of 8.69 m3. To start with, the conventional deterministic design, which assumes business-as-usual parameter values and overlooks their uncertainties, gives a required solar caption area of 223.0 m2 to achieve an annual solar fraction of 70%. However, if the uncertainties of input parameters are considered, the reliability of this design solution is barely 22% regarding the solar fraction target set, and a solar caption area of 326 m2 would be required to achieve a reliability of 90%. This work proposes a revised design solution which such high level of trustworthiness but with a lower solar caption area and, therefore, more attractive from an economic perspective. The strategy consists of narrowing the uncertainty bounds of those controllable parameters causing major variance on the system performance. A sensitivity analysis showed that the most significant uncertainties concerning the variance of the solar fraction are the following (in decreasing order of importance): variation of the hot water supplying set-point, insulation defects in the hot water distribution loop, wrong adjustment of thermostatic valves and dust deposition on collectors. According to the improved design proposed rooted in the revision of uncertainties through the installation of high-quality measurement and control equipment and effective maintenance, a design with a solar caption area of 257.3 m2 would be enough to reduce the probability of failure below 10%.

A Practical Application of DC Droop Control with IoT capabilities

Damiën Zuidervliet — 2022-05-15

The application of DC grids is gaining more attention in office applications. Especially since powering an office desk would not require a high power connection to the main AC grid but could be made sustainable using solar power and battery storage. This would result in fewer converters and further advanced grid utilization. In this paper, a sustainable desk power application is described that can be used for powering typical office appliances such as computers, lighting, and telephones. The desk will be powered by a solar panel and has a battery for energy storage. The applied DC grid includes droop control for power management and can either operate stand-alone or connected to other DC-desks to create a meshed-grid system. A dynamic DC nano-grid is made using multiple self-developed half-bridge circuit boards controlled by microcontrollers. This grid is monitored and controlled using a lightweight network protocol, allowing for online integration. Droop control is used to create dynamic power management, allowing automated control for power consumption and production. Digital control is used to regulate the power flow, and drive other applications, including batteries and solar panels. The practical demonstrative setup is a small-sized desktop with applications built into it, such as a lamp, wireless charging pad, and laptop charge point for devices up to 45W. User control is added in the form of an interactive remote wireless touch panel and power consumption is monitored and stored in the cloud. The paper includes a description of technical implementation as well as power consumption measurements.

Laboratory test of commercial smart radiator thermostats when used for load shifting

Virginia Amato — 2022-05-15

The recent development of smart radiator thermostats has made it possible to integrate them in demand response programs. Advanced control strategies for demand response such as Model Predictive control (MPC) can be combined with radiator thermostats in a hierarchical way for the regulation of space heating systems: the MPC controller calculates the optimal set-point temperature to be tracked by the PID controller of the thermostat. Coupling MPC and thermostat-based control gives the possibility to regulate independently each radiator flow and therefore has the advantage of an efficient room temperature control. Currently, several smart thermostats available on the market are programmable, can be controlled remotely and allow to implement advanced control algorithms. In addition, the thermostats used for load shifting should be reliable, fast responding to changes in settings and precise in tracking a room temperature set-point. The purpose of this study was to compare the performance of different commercial smart radiator thermostats by performing laboratory experiments and to evaluate whether they are appropriate for load shifting purposes. The thermostats tested were Danfoss Eco 2, Eurotronic Spirit Z-Wave Plus and MClimate Vicki. The experiments were carried out in a room where the temperatures in strategic locations were measured. The experiments were designed to evaluate how the thermostats reacted to a changed set-point and if they were able to maintain the desired room temperature. Additionally, the experiments assessed how an increasing temperature set-point affected the flow, the radiator cooling and the thermal comfort in proximity to the radiator. The results obtained so far show that the three tested thermostats had different behaviours in terms of temperature control reliability and accuracy. The three products had different advantages and drawbacks and they all require adjustments for successful integration in an MPC system.

Individual EV load profiling and smart charging to flatten total electrical demand

Ward Somers — 2022-05-15

The rapid growth of electric vehicles (EVs) is stimulating their integration into the existing power grid to reduce power peaks and avoid grid congestion using smart charging strategies. Specifically, at commercial buildings, most EVs charge simultaneously in the morning resulting in large power peaks. This uncoordinated EV charging is changing the existing building load profile, which already fluctuates due to HVAC operations and PV fluctuations, significantly with their dominant charging load by amplifying power peaks. The changed building load profile of a single building does not influence the grid significantly, but the cumulative power peaks at commercial buildings can cause grid congestion. Smart charging can solve this problem by regulating power rates of charging sessions to anticipate the electrical building load. Therefore, this research aims to evaluate individual EV charging load profiles, based on real-world data, and the smart charging potential to flatten the total electrical load of a case study. Daily charging load profiles are constituted with k-means data clustering techniques to obtain the general charging profiles of individual EVs for deploying smart charging strategies. Additionally, the HVAC load flexibility potential is explored to complement smart charging with load flattening. The smart charging potential showed promising results with individual power peak reductions up to 37.8% and an average power peak reduction of the total EV load of approximately 60%.

Identifying promising use cases for a novel heat battery in Dutch residential buildings

Shuwei Wang — 2022-05-15

Owing to the recent breakthrough in thermochemical storage technology, a novel closed-loop thermal energy storage (TES) system, the heat battery (HB), has been introduced. With higher energy density and no storage loss, this system is believed to have a greater potential of helping the energy transition in the built environment compared to other conventional TES systems. To identify the most promising use case of the HB, this research proposes a simulation approach to predict and assess how the HB will influence the performance of Dutch residential buildings. Based on a literature review and discussions with developers of the HB, a list of potential use cases is defined and the most important stakeholders are identified (homeowner, distribution system operator, and district heating system operator). Next, the simulation approach was conducted. The results show that the HB has the potential of both reducing the operational energy cost for the homeowner and reducing the peak heating load from the building to the district heating system.

Stratification and draught measurements of ceiling panels, underfloor cooling and fan-assisted radiators

Karl-Villem Võsa — 2022-05-15

This paper reports the results of room conditioning unit measurements carried out in a NZEB test facility in 2021. Ceiling panels, fan-assisted radiators and existing underfloor heating contours were tested in several experimental configurations, operating with relatively high chilled water flow temperatures as these are all non-condensing systems. Time-controlled heating dummies were used to imitate internal heat gains along with the natural solar irradiation to vary the cooling demand. We quantify the vertical temperature gradients due to thermal stratification by measuring air temperatures at various heights. We also present the differences in thermal comfort of the tested systems, as we measure the air velocities and operative temperatures at points of occupancy with a standardised measurement probe. The gradient and operative temperature values affect the cooling emission efficiency which can be compared against an ideal cooling emitter. Measured results can be used to develop a new method for quantification of cooling emission efficiency. The annual emission efficiency can be assessed by applying measured values under different boundary conditions as inputs to simulation models.

Benchmarking the measured energy use of Nordic residential buildings and their Zero Energy-readiness

Andrea Ferrantelli — 2022-05-15

It is well known that buildings are responsible for a nearly 40% share of the total energy consumption; in order to reduce it by improving the energy efficiency of the building stock, it is necessary to first evaluate their performance. Building energy benchmarking provides information to stakeholders and motivates energy retrofits, by evaluating and comparing a building to similar units and/or to a reference building in terms of energy consumption with the minimum amount of data possible. Towards this end, in this paper we analysed nearly 19000 Estonian Energy Performance Certificates (EPCs) of detached houses. By means of a systematic statistical investigation, we determined the time evolution of EPC labels and evaluated the impact of incentives pre/post renovations, drawing a comprehensive and updated picture of the Estonian detached houses. This allowed evaluating their readiness based on recent trends: unfortunately, new or renovated dwellings are not estimated to achieve the zero-energy status by 2050. Although marginally due also to the use of homeworking during the COVID-19 pandemic, we show that this is mostly determined by changes in the regulations. A benchmarking ranking for each construction type was also created by calculating rating tables based on a 0-100 coefficients scale; this allows comparing with the existing stock any building with known EPC, for energy Audit and other investigations aiming at energy efficiency.

Investigation of additively manufactured triply periodic minimal surfaces as an air-to-air heat exchanger

Alper Mete Genç — 2022-05-15

Additive manufacturing provides freedom of production and design of geometries that cannot be produced with traditional methods. Therefore high-efficiency and innovative heat exchanger designs can be produced with 3D printer technology efficaciously. Heat recovery ventilation devices, which meet the indoor air quality requirements with high thermal efficiency, allow heat recovery between the exhaust air and fresh air with the help of the recuperator, which is an air-to-air heat exchanger. In this study, the production processes of triply periodic minimal surfaces (TPMS) with the additive manufacturing method and their performance as an air-to-air heat exchanger are examined. Triply periodic minimal surfaces are three-dimensional and infinite surface geometries that can be expressed with continuous trigonometric functions, forming two separate non-intersecting spaces for fluids. The surface geometry derived from the trigonometric function can be arranged to provide heat transfer between two unmixed fluids at different temperatures. In this study, Schwarz-D, Schwarz-P and Shoen's gyroid geometries are investigated as triply periodic minimal surfaces. During the production of these geometries processes, parameters such as wall and layer thicknesses and printing temperature were changed to achieve the lowest possible wall thickness (0.16mm) with the 3D printer used. The performance of triply periodic minimal surface geometries as air-to-air heat exchangers are determined experimentally in a crossflow experimental setup.

Grid-impact factors of field-tested residential Proton Exchange Membrane Fuel Cell systems

Nicolas Paulus — 2022-05-15

Much needed energy transition currently brings focus on micro-combined heat and power (mCHP) systems for residential uses, especially on low-capacity fuel cells (about 1 kWel) because it has been reported that they allow for increased CO2 savings per kWel compared to engine-based mCHP’s [1]. One of those (already commercialized), is a Proton Exchange Membrane Fuel Cell (PEMFC) system hybridized with a conventional gas condensing boiler. It is fed by natural gas; it is designed to cover all the heat demands of residential houses as well as to participate locally in the electrical production. Thanks to high integration levels, it combines a PEMFC of nominal constant power of 0.75kWel and 1.1kWth, a 220L DHW (Domestic Hot Water) tank and a condensing gas boiler, mainly used for peak heat demands, that designed to provide up to 30.8kWth. The financial incentive representing a major factor in the investor’s decision towards such a technological change, focus will indeed be brought on supply and demand cover factors since they are directly linked to how much the citizens are individually billed and since they constitute actual and future unavoidable keys in the energy transition, as more and more intermittent renewable energies will be integrated to the energetic mix. This study is monitoring two of those installations in residential houses in Belgium, arbitrary chosen, for the whole year 2020. Sampling time of the monitoring hardware is between 2 and 5 minutes but it has been chosen to analyse the grid impacts factors according to average daily values (along with their seasonal trend and yearly figures). This paper has established yearly supply cover factors between 34 and 36%, which are believed to be higher (based upon literature) that what typical photovoltaics (PV) power plants would have allowed. It unfortunately remains lower than the 37.46% “prosumer” limit considered in the tariffication of Wallonia PV installations [2]. On the other hand, this paper has established yearly demand cover factors of 25 and 33%.

Design and experiment study of membrane based isothermal dehumidifier in HVAC system

Cheon Seong-Yong — 2022-05-15

As passive building systems improve, sensible loads decrease and the air conditioning system takes on a greater role in dehumidification. Isothermal dehumidifier with membrane, which utilizes a vacuum pump to create a partial vapor gradient between membranes, has the potential to save significant energy by operating just for latent cooling as a thermally decoupled system. Although research has concentrated on analyzing the dehumidification and energy performance of isothermal dehumidifiers via simulation studies, their design and experimental analysis for dehumidification systems in HVAC systems remain rare. In this study, we constructed a prototype of an isothermal dehumidifier using hollow fiber membrane modules and vacuum pumps for an air conditioning system. Under different air conditions, the constructed prototype was evaluated for dehumidification characteristics (i.e., isothermal process, moisture removal rate, and dehumidification efficacy). Three factors were used to choose the air conditions for testing the dehumidification performance: air temperature, air humidity, and air velocity. The experiment results indicated that the isothermal dehumidifier dried the air without changing the temperature, and the overall dehumidification performance of the prototype system indicated that the humidity ratio difference was between 3.8 and 14 g/kg, the moisture removal rate was between 0.12 and 1.0 kg/h, and the dehumidification effectiveness was between 36% and 81%.

Evaluation of tariff structural changes in Spanish households affected by energy poverty

Mariana Jiménez Martínez — 2022-05-16

A new structure for regulated tariffs affecting consumers with contracted power up to 15 kW was introduced by the Spanish government in June 2021. According to the National Commission for Markets and Competition the new tariff would impact residential consumers differently, depending on previous contracting conditions. In particular, households under old Time-of-Use tariffs are expected to face a significant increase in their electricity bill, which might be exacerbated by the rising generation costs observed in the Spanish market throughout 2021. This situation becomes more relevant for consumers affected by energy poverty, especially when considering that this group needs to be in a regulated tariff to access social benefits. A set of energy poverty affected households are evaluated during a monitoring campaign carried out in Barcelona’s pilot as part of EmpowerMed H2020 project, whose objective is to tackle energy poverty and help improving people’s health in the coastal areas of Mediterranean countries, with a particular focus on women. Hourly consumption data is downloaded from the customers’ smart-meters, which are accessed through their personal account in the distributor’s website. Using this data, the article presents an evaluation of the potential impact that the new tariff structure might have on energy poverty affected households, considering different price scenarios that reflect the observed rising generation costs and the price mitigation measures enacted by the government in an attempt to reduce its impact on domestic consumers.

Energy consumption patterns in a hotel building

Marek Borowski — 2022-05-16

The hospitality industry is one of the most energy-intensive subsectors of the tourism sector. Most of the total energy consumption is due to maintaining an optimal temperature inside the occupied rooms. Conditions inside hotel rooms, hotel infrastructure, including tourist attractions such as swimming pools, restaurants, conference rooms, have a significant impact on the overall energy consumption of this sector. Hotels, unlike other commercial buildings, are characterized by the separation of functional areas. Additionally, the heat loads that change over time are difficult to estimate. The research was carried out in the historic hotel Turówka, which is a reconstruction of the historic salt sales point from 1812. Due to the historical nature of the building (entered in the register of monuments), the thermal modernization of the hotel, adjusting it to the prevailing energy standards, is a big challenge for designers. The work aims to determine the structure of the building's heating and cooling energy demand. Additionally, the factors influencing the building's energy demand in the building during the summer period are determined. The analysis focused on identifying typical patterns of weekly and daily demand and examining the correlation between meteorological parameters and the observed energy consumption. Based on the obtained results, factors that significantly affect the consumption of thermal energy in the building were identified. The article covers the analysis of the energy performance of the building, including the energy demand of three systems in the building: the cooling system, domestic hot water preparation, and the demand of the swimming pool area. Measurements of energy consumption were carried out continuously, using installed heat and cooling energy meters in key places of the installation. An in-depth energy analysis of a building is a necessary element to improve its energy performance and adapt it to the requirements of low-energy buildings. Monitoring the energy consumption of your building system can help you optimize energy use.

TEWI and energy assessment of integrated CO2 refrigeration, heating and cooling technology

Nishant Karve — 2022-05-16

In order to meet with the regulations proposed by the Intergovernmental Panel of Climate Change to control emissions from fluorinated gases, an EU funded project (LIFE) has been engaged in. Through this project, the reduction of CO2 emissions by using an integrated refrigeration, heating and cooling system, in real shops across Europe and the impact of the raw materials used will be investigated. In a theoretical evaluation, the Seasonal Energy Performance Ratio and Total Equivalent Warming Impact of the unit is compared to an R-410A unit using test measurements. Although the CO2 unit has a lower Seasonal Energy Performance Ratio, the Total Equivalent Warming Impact was calculated to be lower in comparison to the R-410A unit over a period of 10 years. These measurements were also used to discuss the importance of heat recovery by comparing the unit to a non-integrated refrigeration, heating and cooling system. The energy assessment of the unit at a real installation in a supermarket in Europe has been presented on a monthly basis. This assessment involves the use of a compressor curve method to estimate mass flow and as a result, the delivered energies in the absence of expensive flow meters. The precision of such a method has been discussed. To conclude, challenges concerning the technology and important results and conclusions have been discussed.

Development of Heat Recovery Radiant Heating System using Dynamic Insulation

Jaeung Hwanga — 2022-05-16

From various studies, it is said that floor heating is a more hygienic and comfortable heating system than air-conditioning heating. However, floor radiant heating does not use all of the energy used for indoor heating, and some of it causes heat loss to the underfloor space. This research proposes a heat recovery type radiant heating system that can recover heat radiation under the floor by applying dynamic insulation to the underfloor space. The purpose of this study is to examine the heat recovery effect and the risk for condensation by using the actual measurement and CFD simulation of the experiment module. To achieve this goal, using 2 m × 5 m × 2.5 m experiment module measurement with and without dynamic insulation during the heating period, the heat load, ventilation rate, and thermal environment were measured. Previously, according to the results of model measurements on a 1/3 scale of the experiment module, when the temperature difference between indoors and outdoors was 20 °C, a dynamic insulated floor radiant heating system was used to reduce the heat load by 23.8%. And, as the real-scale CFD simulation results, the heat load was reduced by up to 49% using the heat recovery radiant heating system. In order to confirm the risk of condensation during the cooling period, the relative humidity of the underfloor space was measured. When air is taken into the room from under the floor, there is a high possibility that condensation will occur during the cooling period. To reduce the risk of condensation, it is necessary to take air out of the room from under floor during the cooling period.

Experimental investigation of the contaminated volume around a person in a clean room

Julia Lange — 2022-05-16

To monitor the particle concentration in a clean room, the measuring position is usually chosen based on a risk analysis and a monitoring plan. The demand zone is the area on the table, where the product is placed and where very clean air must be assured. Measuring the particle concentration in this working area is often difficult, as the measuring probe may obstruct the work flow. A situation that frequently occurs in a clean room is that of a person working at a work table. In this experimental investigation, the radial spread of particles, emitted by a dummy, is investigated. Particles are emitted from the proximity of the mouth region, with a source strength that is much higher than the normal particle emission of a human being when speaking. The aerosol distribution is measured with a laser particle counter at varying measuring positions. In the present case, the demand zone is defined as the area above the table in front of which the dummy is standing, 250 mm deep and 500 mm wide. Hot-wire anemometers are used to measure the velocity profile in the close up range of the dummy. The influence of the distance between table and wall on the velocity and particle field is investigated, at varying inlet airflow velocities between 0.25 - 0.45 m/s. The results show that the table positioning has an influence on the flow velocities in the demand zone and that the table should be positioned in the room if possible.

Adjusting the design of a radiant heating system for office retrofit

Barbora Junasová — 2022-05-16

Installation of low-exergy water-based radiant systems can help alleviate the negative effects of increased energy consumption due to their suitability for combination with low-grade renewable energy sources. Radiant heating and cooling installations in buildings are common, but their application in existing buildings as part of retrofit is relatively rare. The present study investigated some of the aspects of the installation of radiant heating systems in existing buildings. Wall and ceiling systems with pipe underneath the surface were considered because of various potential benefits. These include the possibility of operating as cooling in summer and heating in winter, easy installation in existing buildings, minor space requirements, and no or little need to reduce the height of the storey, especially in the case of walls. It was found that with a thermally conductive core, only a thin insulation layer of 1 cm may suffice if the temperature difference between rooms is relatively small. For an insulating core, no insulation may be needed even at higher temperature differences between rooms. Reducing the pipe spacing to about 5 cm was found to be efficient in terms of increased thermal output per 1 cm of spacing. The location of the insulation had a small effect on the thermal losses, but the output was higher for insulation placed on the outer side of the wall due to a more uniform temperature distribution in the structure. This configuration also allows for considerably higher heat storage capacity.

Heat recovery ventilation solutions for school building renovation

Helena Kuivjõgi — 2022-05-16

School building ventilation solutions have been mainly natural ventilation. Only in a few decades has the renovation of ventilation systems in school buildings started. However, there are still many buildings in Estonia that have natural ventilation or mechanical extract ventilation without heat recovery. Last solution can ensure indoor climate requirements in favourable climate conditions if well designed. However, this can lead to excessive heating energy use resulting in not adequate energy performance. Therefore, there is a need of ventilation system renovation to improve both IAQ and energy performance. Two solutions with different cost are studied in this paper: classroom air handling unit (AHU), and central AHU. The aim of this study is to determine which solution is better in energy efficiency if there is demand to renovate ventilation system in school building. The calculations have been done in standard and real use and climate. Study will show the cost-optimality of these solutions in school buildings. Two school building models were composed and building performance simulations (BPS) with the test reference year climate file were conducted to calculate the building energy use based on EN 16798-1:2019 and real use (where the building model was calibrated with monthly measured real energy consumption from year 2014). Previous studies show, that natural ventilation is an electricity saving solution, but not good for indoor climate. This study found that classroom-based solution is easier to build and the initial cost is lower. However, the energy saving for central ventilation solution will exceed the classroom solution of 29 kWh/m2. Considering energy and cost calculations, the centralized mechanical ventilation with heat exchange will be slightly more cost-optimal solution in this case study as it gained 4 €/m2 lower global cost than classroom-based solution.

Surefit - Sustainable solutions for affordable retrofitting of domestic buildings

Janne Hirvonen — 2022-05-16

To reduce greenhouse gas emissions caused by buildings, the EU has declared the Renovation Wave strategy with the goal of retrofitting existing buildings to be more energy efficient. Long-term emission reductions require both speedy and cost-efficient renovation methods. The Surefit project aims to develop practical means for effective building retrofitting. The aim is to reduce emissions and CO2 emissions by 60%, to reduce installation time by 40% and to demonstrate a payback period of less than 10 years. New modular technologies for improving energy efficiency and indoor conditions will be tested. This study examines three demonstration buildings chosen from three European countries (United Kingdom, Spain and Greece). Each demonstration building was modelled using IDA-ICE and their energy demands simulated to provide the baseline for energy efficiency. Then, various retrofit options were tested using dynamic computer simulations, with the aim of finding out the impact of the different technologies in different climates and under different energy mixes. This study focuses on measures integrated to the building envelope and structure, namely bio-based thermal insulation, solar electric low-energy windows and phase-change materials. Thermal insulation of the building envelope using bio-aerogel reduced CO2 emissions by 41-43% in continuously heated buildings, but only by 15% in an intermittently heated building. The emission impact of PV glazing was only 3-8%. PV glazing resulted in a slight reduction of overheating in Spain and UK, but increased the temperatures in Greece, because it could not replace the external shading device that was removed when PV glazing was installed. The benefits of PCM were low. A smart ventilation control scheme or a different type of PCM material could help in attaining additional benefits.

Experimental investigation on a packaged unit of membrane dehumidification-based ventilation system

Cho Hye-Jin — 2022-05-16

This study purposed to experimentally investigate the seasonal operating performance of the packaged unit of a hollow membrane-based ventilation system. The packaged unit of the proposed ventilation system was fabricated, and the experiments was conducted based on the test standards for the energy recovery ventilator addressed from air-conditioning, heating and refrigeration institute (AHRI). In addition, for achieving the optimal heat and moisture recovery from the ventilation system under various operating conditions, the seasonal operation modes were suggested for the packaged unit of the proposed ventilation system. The measured data showed that the proposed ventilation unit can provide the ventilation air ait nearly neutral air temperature and humidity ratio in each operation mode. In addition, the average sensible effectiveness, the average latent effectiveness, and the average enthalpy effectiveness of the proposed ventilation system are 70.7%, 75.9%, and 75.6% in mode 1; 44.4%, 74.7%, 80.2% in mode 2; 77.6%, 70.4%, 85.6% in mode 3, which exhibited the higher heat and moisture recovery performance compared to the commercial energy recovery ventilator. In conclusions, the measured data demonstrates that the proposed ventilation system has a great application potential for building ventilation unit in terms of energy recovery performance.

Experimental and numerical performance evaluation of building integrated photovoltaic with thermoelectric generator and phase change material

Yong-Kwon Kang — 2022-05-17

Building-integrated photovoltaics (BIPVs) are the most promising systems for achieving zero-energy building in cities. However, BIPV has some shortcomings, such as a lack of solar tracking and a rapid increase in the PV surface temperature. Therefore, resolving these shortcomings requires system solutions to eliminate heat from panels or utilize heat sources to improve system efficiency. Heat dissipation methods using phase change materials (PCMs), heat fins, thermoelectric generators, air cooling, and water cooling have been proposed and studied. Among them, the passive technology PCM and thermoelectric generator are attracting attention. Using PCM can reduce the panel temperature without additional energy consumption. In addition, some studies have been conducted on BIPVs with a thermoelectric generator (TEG) or using a working fluid such as water or air to increase the system efficiency. Methods of heat recovery using fluids for conventional PV panels, owing to the characteristics of BIPVs installed on the exterior of building walls, have also been proposed. Some studies have also explored designs that combine TEGs, generating electric power depending on the temperature difference without additional equipment. However, TEGs also have the disadvantage of an extremely low power generation efficiency if they do not achieve a sufficient temperature difference. In this study, to address the shortcomings of each application, a BIPV combined with a PCM and TEG (BIPV-TEG-PCM) is proposed. Herein, the appropriate phase change temperature of the PCM and heat sink design in the PCM container were analyzed through computational fluid dynamics-based simulations and experiments.

Analysis of the application of ventilative cooling in different regions of Turkey

Asli Birturk — 2022-05-17

Energy efficiency practices have gained momentum in recent years and continue to invest. The main motivation of this study is whether an effect can be achieved with ventilative cooling in terms of energy efficiency in buildings with mechanical ventilation, especially in transition seasons. In this context, the potential of ventilative cooling in different provinces of Turkey, where hourly average temperature values are taken, has been examined. According to the results obtained, ventilative cooling can be considered as an energy efficienct application.

Fastlane – Dynamic approach to low carbon and energy producing real estate portfolios – case Amsterdam Universities

Thomas Verhoeven — 2022-05-18

In The Netherlands Municipalities, Universities and Healthcare organizations all have targeted to meet the Paris agreement targets, ‘Nett Zero Carbon’ namely 95% CO2-emission reductions compared to 1990, long before 2050. To support these organizations on their journey to meet their targets effective and efficient, regarding Carbon emissions as well as costs, a dynamic approach called FastLane is developed. FastLane has already been used for more than 1,000 buildings in more than 75 portfolio roadmap plans to reduce in total 1-3 Mton CO2 emissions by 2050. Implementing all these plans, we can reduce up to 1-3 Mton CO2 by 2050. This approach deals with three important challenges of the energy transition: only limited time and budget available, close the energy gap between calculated and measured Carbon emissions and provide a dynamic insightful tool to monitor and control the energy transition. These challenges require a different approach than traditional energy studies to identify and select measures. In this paper the requirements, demands and benefits of the developed approach, consisting of a methodology, smart tools using databases and strong insightful presentations in dashboards, are explained. The approach is illustrated with the case of University of Amsterdam & Amsterdam University of Applied Sciences with a combined portfolio of 50 buildings. Insights are given how Amsterdam University aims to reach their targets and how they are in control doing so during their journey. A roadmap with the most important renovation measures is presented including the possibilities of dynamic interventions adapting to possible changes in the future. Enabling an optimized timing of applying the measures. This already saved Amsterdam University up to 20% of the costs for the energy transition and optimizing the implementation along the way will guarantee the most effective and efficient energy transition of the real estate portfolio.

Methodology for the development of temporally high-resolved and spatially accurate tapping profiles

Mark Distelhoff — 2022-05-18

Within the framework of a current research project, different types of drinking water installations in flats are analysed and compared in a simulation study with regard to drinking water hygiene criteria. The planned modelling of the temperature, stagnation and flow behaviour of individual pipe sections requires the development of particularly detailed tapping profiles. The paper at hand shows a methodology to derive tapping profiles in the required level of detail. A spatially accurate resolution requires that each of the selected draw-off points - washbasin, kitchen sink, shower, bathtub, WC, dishwasher and washing machine - receives its own tapping profile, separated into hot and cold water. The high temporal resolution is the prerequisite for an adequate recording of short tappings lasting only seconds. The basis of the tapping profiles is a statistical database of tapping quantities and frequencies for three different types of residents (couple, family, retirees). In the next step, the DHWcalc tapping profile generator is configured and used to create spatially accurate tapping profiles. Subsequently, an Excel VBA tool refines the time step from 1 min to 5 s and shortens the tapping time for small tapping quantities. By means of simulations with the software TRNSYS an exemplary compact T-piece installation is set up to account for transient effects, like temperature adjustment processes at the shower. With the pre-sented methodology, tapping profiles can be created for different installations that clearly exceed the level of detail of DWHcalc and are suitable for detailed simulative analyses.

Decision tree for early-stage design of hybridGEOTABS office buildings

Mohsen Sharif — 2022-05-18

Hybrid GEOthermal heat pump system coupled to Thermally Activated Building Systems (hybridGEOTABS) utilises the high thermal capacity of TABS to smooth out the building thermal loads and downsize the production units. Moreover, hybridGEOTABS has achieved remarkable carbon emissions saving. However, the optimal design of hybridGEOTABS is not achieved with current design methodologies. This article provides a decision tree for early-stage design of hybridGEOTABS office typology. To derive the decision tree, a design methodology which has been previously developed and verified was applied on nearly 40,000 office building case studies with variety of parameters such as climate, insulation level, and internal gains. The methodology exploits multi-zone dynamic simulation of building energy performance and optimal control of TABS for peak-shaving to offer an optimal sizing of the HVAC components. To analyse the results of the numerous simulations and to drive the decision tree, supervised machine learning, specifically a classification technique, was deployed. The application of the decision tree is exemplified in this article using three case studies. The decision tree also enables architects to practice the influence of different parameters on the sizing and performance of the HVAC system. Thus, designers may use it to optimise the building physical design to increase the possible share of geothermal system as a sustainable core for providing thermal comfort in buildings.

Upgrade of ice storage system in congress centre

Urška Mlakar — 2022-05-18

Storage of various forms of energy is a relevant topic in last decades. The ability to store energy that is produced at a time when we have a surplus of a particular source and use it at a time when energy needs are greater is crucial. We can store energy as electricity or as thermal energy (heat and cold). In this paper, we will take a closer look at latent cold storage with ice bank technology. Ice bank technology exploits latent heat in the liquid-solid phase change of water. Of all the cold storage technologies available, ice storage is the most popular in recent decades due to its high latent heat, especially when available space is limited. Cold in ice banks is produced at night, when electricity is cheaper, and is used to cover cooling needs especially at peak hours during the day. In Slovenia, the technology of ice banks has already been applied several times. Among other buildings, this technology is also used in buildings such as the Opera and Ballet, the Crystal Palace, and the Congress centre Cankarjev dom. This Congress centre has a system with nine ice banks with a total nominal capacity of 405 kWh per ice bank, for its cooling needs. The transition to ice bank technology has allowed them to cut by 41 % the power of their refrigeration units, while saving money is achieved since ice is produced at night time with lower prices. The article presents the three phases of the system: Energy for cooling of a system without ice banks, a system with ice banks and saved energy with this technology and an analysis of the upgrade of this system with PV modules. The simulations were done with the Trnsys program. Indicative savings with the application of ice banks and additional upgrades with PV modules are presented. The payback periods are also analysed.

Renewables the frontiers towards low carbon resilience

Prachi Ugle Pimpalkhute — 2022-05-18

As we are transitioning towards low carbon economy, renewables have become a compelling investment for foraying ahead in shaping global energy sector landscapes. Upfront higher costs are an impending challenge for the global renewable market. Ways and means to channelize and inflow of capital into renewables is of utmost priority. Innovation, co-creation and bonds are some approaches towards creating an equally accessible and allocable renewable energy portfolio with reduced credits risks. Credit risks and policy risks are the two major constraints that are undermining the mobilization of finance in renewable energy projects. Hedging solutions per se and reducing barriers better facilitate and manage shall need varied tools, instruments, mechanisms and rating models. This paper aims to put forth the valid policies, practices, frameworks and tools –on improving the access and allocation of green energy projects and credit risk management with better solutions for ease of implementation for future trajectories. Varied policies and tools that reduce barriers and mitigate risks include a) Enabling policies and tools which are divided into Financial policies and regulations, Project Preparation Facilities, Project facilitation tools, on-lending facilities, and Hybrid structures b) Financial Risk Mitigation Instruments which include Guarantees, currency hedging instruments, liquidity facilities, Resource risk mitigation tools and c) Structured Finance Mechanisms and Tools which includes Standardization, Aggregation, Securitization, Green bonds and Yieldcos, The policy push for systems integration of renewables and enabling technologies (such as energy storage) should focused primarily on increasing power system flexibility and control, as well as grid resilience. Flexibility, in particular, is an important requirement for systems integration of renewables as the share of VRE (Variable Renewable Energy) generation rises. The key deliverables from the paper include: policies which should advance the integration of both centralized and distributed VRE and increase the flexibility of the power system pertaining to, for example: market design, demand side management, transmission and distribution system enhancements, and grid interconnections. Since, countries have renewable energy support policies, they should now promote renewable portfolio standards (RPS), other quota obligations, incentives, feed-in policies (tariffs and premiums), renewable power tenders and auctions, incentives and community choice aggregation programmes.

Hardware-in-the-loop heat pump model validation for flexibility evaluations

Maarten Evens — 2022-05-19

Heat pumps play a paramount role in carbon emission reductions as they allow the use of sustainable energy. As heat pumps mainly use electricity to provide thermal services, they also enable the provision of energy flexibility services. In this context, new heat pump control strategies are investigated. Though, the comparison of smart and traditional control strategies requires an accurate knowledge of the real heat pump behaviour, both in short- and long-term. Firstly, this paper presents a hardware-in-the-loop set-up which allows a real heat pump behaviour analysis, while the required communication is also shown. Secondly, the test bench was used to validate and further develop a water/water heat pump model. Hence, artificial test cycles were used to distinct and validate the internal control strategies of the heat pump, with the focus on both the short-term behaviour and energy consumption. As the heat pump model started from the manufacturer documentation, comparing the experimental results to the simulations revealed deviated behaviour due to a different modelling approach of the heat pump internal control strategies. Hence, the heat pump model was improved by changing and adding control strategies such as a compressor modulation controller, timing constraints and condenser and evaporator pump control. Although the improved heat pump model reached better profile agreement, deviations remained and indicated a calibration work necessity. Analysis also showed that the real heat pump was not able to quickly recover for the combination of high space heating temperatures and low thermal loads, while increasing the supply temperature for energy flexibility services is common. To conclude, results proved that only using heat pump manufacturer documentation is not sufficient for real heat pump behaviour representation.

Development of occupancy-based multi-scale building archetypes

Divyanshu Sood — 2022-05-19

In the context of the European building stock, more than 50 % of buildings were built before 1960, and it has been estimated that 75 % of the current building stock will still exist in 2050. A typical approach to estimate energy consumption at multiple scales is by using archetypes which are the cohort of representative buildings with similar characteristics. Typically, archetypes are classified based on year of construction, type of dwelling and type of heating system. Since, this classification does not account for the stochastic nature of occupancy, a typical occupant presence pattern from the literature is considered. This study develops a methodology to generate stochastic occupancy profiles using the UK Time Use Survey (TUS) 2014-15 data. The occupancy profiles take into account the affect of the day of the week, the month of the year, the number of residents in the household and the type of dwelling. To test the methodology, we used the Irish residential building archetypes and 5-8% variations in energy use intensity are observed using the developed occupancy profiles for an apartment archetype having one and two occupants. The generated occupancy profiles facilitate the pathway to develop robust archetypes for reliable energy prediction at an urban scale. Furthermore, robust archetypes allow policymakers and urban planners to recommend appropriate energy efficiency measures for the sustainable development of residential building sector.

Optimization of Novel Air‐to‐Refrigerant Heat Exchangers for Lower‐GWP Refrigerants in Air‐ Conditioning Systems

James Tancabel — 2022-05-19

Air-to-refrigerant heat exchangers (HXs) are fundamental components in HVAC&R systems, and considerable research has focused on reducing the airside thermal resistance, which can exceed 70-90% of the overall resistance. Traditional HX design ideology utilizes secondary heat transfer surfaces (fins) to reduce the airside thermal resistance by increasing the airside heat transfer area. However, fins also have inherent deficiencies such as increased airside pressure drop, material costs, and HX fouling/frosting potential. Recent advancements in simulation tools such as Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) and also in optimization algorithms have enabled researchers to apply shape and topology optimization to the primary heat transfer surfaces (e.g., tubes) to design high performance, highly compact HXs which do not require fins. These novel HXs feature reduced size, weight, cost, and refrigerant charge compared to current state-of-the-art HXs while maintaining or improving system-level performance, thereby reducing the overall environmental impact. Such factors are especially important given the recent governmental and industrial shifts to low-GWP flammable and mildly-flammable refrigerants, which have highly regulated charge amounts. In this paper, an HX optimization framework featuring automated CFD and FEA simulations and approximation-assisted optimization is utilized to optimize a residential A/C condenser for three different refrigerants: (i) R410A (industry-standard for US residential A/C units), (ii) R32 (most popular lower-GWP replacement for R410A in the EU), and (iii) R454B (another lower-GWP alternative to R410A). Preliminary findings show that the optimal HXs achieve at least 20% reductions in airside pressure drop and envelope volume, up to 11% reduction in tube material volume, and more than 40% reduction in tube internal volume while delivering similar capacity to the state-of-the-art baseline HX. The differences between the refrigerant-specific optimal HXs are also discussed in detail to shed light on how the refrigerant choice impacts the final HX designs. By using systematic optimization, it is possible to arrive at highly compact and lighter HX designs for any of the new lower-GWP replacement refrigerants.

Monitoring a deep energy renovated building

Matthias Haase — 2022-05-19

A typical residential building from 1937 located near Wurzburg in Germany, was deep retrofitted in 2013. The energy use and costs could be drastically reduced compared to the old building. However, increase in energy costs can thread economic success. Therefore, it is important to monitor also the performance of the different technical systems. A measurement campaign of a real building with energy consumption and production (“prosumer model”) proves the concept of prosumer over time. The total energy costs were 387 € in 2018 and have increased to 839 € in 2021. This is an increase of 217%., changes in energy prices and tariff structures might influence the lifetime energy costs as well as the savings. Electricity use of the compact unit was measured, share of ventilation and heat (heating and DHW) was calculated based on standard models. Electricity use is illustrated and contrasted with electricity production from a 7.95 kW solar PV system.

Experimental Investigation of PCM System Improved with Nighttime Ventilation for Enhanced Solidification

Eva Zavrl — 2022-05-19

It is predicted that in EU-buildings by 2030, the energy used for cooling will increase by 72%. Simultaneously, the energy needed for heating will drop by 30%. Thermally well-insulated lightweight framed buildings prevent heat losses through their envelope and reduce the energy demand over the heating season. However, the heat capacity of the lightweight wall is relatively low, and in summer, the building lacks thermal stability and overheats. Phase change materials (PCM) are broadly investigated for their well-known benefits of improving indoor thermal comfort by decreasing indoor temperatures while reducing the energy needed for space cooling when melting. One of the possible application methods is to encapsulate the material and place it in the 'building's building assemblies, such as walls and ceilings. However, due to a low material density (insulation effect) and high indoor temperatures on summer nights, the material does not completely solidify in the night cycle, and does not fully perform (melt) in the day-cycle. Thus, the nighttime outdoor air ventilation has to accelerate the solidification. The system is investigated in an experimental chamber divided into two units (reference and PCM modified). Each unit represents an office located in a South-Eastern Europe region with an above-average sun hours. Both units are equipped with a ventilation inlet (on the bottom of the wall) and outlet (in the middle of the ceiling). The internal wall and ceiling are entirely covered by macro-encapsulated PCM plates (SP24E) placed in the wooden frame. The original wall and ceiling are forming the airtight ventilation gap. In the nighttime cycle, the plates are being solidified with the linear diffuser (placed at the bottom of the wall), distributing the airflow behind the plates upwards (direction wall-ceiling). The results show that under the current configuration, the active-passive system decreases the indoor cell air temperatures in the hottest daily scenario up to 5 °C. Also, the complete PCM plates solidification may be accomplished within the nighttime cycle (12 h), when the air-gap is ventilated, average inlet air temperatures of 15 °C and 16 °C at a flowrate of 500 m3/h.

Determining the infiltration and exfiltration in Supertall and Mega Tall Buildings

Peter Simmonds — 2022-05-19

Most traditional heating and cooling load calculations are based on weather conditions measured at a height of 10 m. But how appropriate is this in Super-Tall buildings 300m+ and Mega-Tall Buildings 600m+? This paper will present some specifics of evaluating building designs and performance in Tall Buildings. From previous designs and research, we know that outdoor conditions vary with height. and the outside climate can have both a positive and a negative effect on the space conditions within the building. This paper illustrates the fluctuation of pressure differentials on the heating and cooling loads of spaces over the height of the building. Rarely does the design of the upper level of the building capitalize on this phenomenon. Furthermore, wind, temperature, and pressure conditions at the top of a tall building are considerably different, therefore façade leakage rates and the buildings stack effect must be carefully assessed. If sufficient data is known about this difference, it can be incorporated to optimize the overall building design. This novel paper explores the nuances of the ambient climate on tall buildings and the effects on the performance of the building.

Textile-based heat exchanger for humidity recovery between spatially separated air flows

Hannes Rosenbaum — 2022-05-19

Both, sensible heat recovery and the combined heat and humidity recovery are state of the art. Of particular importance is humidity recovery in winter season. The transfer of water vapour from the humidity-laden extract air to the very dry outdoor air is very important for a good room air quality. Enthalpy exchangers potentially reduce the energy requirements of any subsequent air humidification on the supply air side considerably. In the planning phase, the possibility of enthalpy recovery is therefore often used as a weighty argument for dispensing with humidification systems. However, all systems established on the market require a coupling of supply air and extract air by means of recuperation (e.g. plate heat exchanger) or direct regeneration (rotating storage mass). Nevertheless, enthalpy recovery systems for HVAC-Systems with spatially separated supply air and extract air are not available on the market. In order to close this gap in the market, ILK Dresden has developed textile-based heat exchangers, which - integrated in closed loop systems - can transfer humidity as well as sensitive heat between spatially separated air flows (e.g. between supply air and exhaust air). The functional principle is based on a liquid sorption process via semipermeable membranes. This is regardless of whether it is a 2-fluid system (air, brine), in which the heat-transferring fluid and the mass-transferring fluid is the same fluid and only one circuit is utilised, or a 3-fluid system (air, brine, water), in which the fluids involved flow in separated circuits. In general, the developed system can be used all year round - thus also for air dehumidification or indirect evaporative cooling processes. The current state of development is presented. In addition, an outlook is given for which applications the textile heat exchangers could be further developed and which application potentials are offered.

Potential assessment of coupling PV electricity with district heating supply of building

Paul Seidel — 2022-05-19

The energy transition in Germany is leading to an increasing decentralized generation of electrical energy. In Fact, the feed-in of electrical surplus of PV systems causes a higher load on the electrical grid. Increased local use prevents this. Significant potential for the integration of produced electrical power of PV plants for this purpose exists in the heat supply. This paper describes the development and evaluation of a system solution from the cross-sectoral use of surpluses from PV plants and district heating. The latter is often used to supply urban apartment buildings. According to research on the market situation, independently controlled heating rods are available for converting electrical power of PV plants into heat. However, a coordinated operation of these heating rods with district heating is not possible so far. In this paper different approaches for combining these two heat sources with various hydraulic concepts and system controllers will be developed and evaluated. As a potential assessment, a parameter study on influencing factors (e.g. user behaviour, power size of the components, building characteristics) was carried out by numerical simulations. As one result, the highest potentials arise from the use of a forecast-based charging control of a combi-storage tank. The charging control can be realised with different techniques, either through simple if-then decisions or a model predictive control. This can only use slightly more produced electrical power of PV plants, as it is limited due to the time lag between PV surpluses and heat demand. Predictions of future energy flows are necessary for both approaches but these have relatively high errors for individual consumers and PV systems. The results of the paper shows, that more complex forecast approaches (demanding large data sets) do not perform significantly better than simple forecast approaches (which can deal with smaller data sets). Model predictive control requires a higher forecast resolution and is therefore also more error-prone, thus it is not recommended. The desired relief of the electrical grids can be achieved through local consumption. In addition, the economic implementation and the carbon footprint of such a concept are analysed under local and global (whole energy-system) aspects.

Performance Evaluation of Passive Cooling in a Multi- Zone Apartment Building Based on Natural Ventilation

Essam Elnagar — 2022-05-19

In moderate climates, using natural ventilation systems could allow to save up to 60 % of the end energy for ventilation and air conditioning. Natural ventilation systems depend on pressure differences to move fresh air into buildings by wind effect and pressure effect. Night cooling can be achieved either by an increased air change rate. The higher air change rate can be realized by ventilators/ mechanical ventilation systems or by free convection. The main objective of this paper is to reduce the internal summer cooling load by increasing the natural cross ventilation between different zones in apartment buildings. The performance of natural ventilation is highly dependent on the external outdoor temperature. Over the last years, an increase in the outdoor temperature has been noticed and predicted to rise by the end of this century according to IPCC which puts into consideration the uncertainty of the climate. This paper investigates the performance of natural ventilation using building energy simulation tool ‘DesignBuilder” to simulate a multi-zone apartment building in Belgium. The indoor thermal comfort is enhanced by determining an optimum set of input parameters such as the setpoint temperatures, the discharge coefficient of the night ventilation, and the opening areas in the building. Those parameters are optimized using current and future weather data to evaluate the evolution of natural ventilation system performance and indoor thermal comfort. The results show that proper use of natural ventilation can significantly reduce the overheating risk during a typical year and that the benefits of natural ventilation are not expected to vanish with global warming. It can be seen that, without natural ventilation, thermal comfort could be reached on average 53.7% of the time, while it could reach 66.2% of the time using single-sided ventilation and 78.8% with cross ventilation. However, during heatwaves, natural ventilation becomes inefficient and cannot guarantee the thermal comfort of the occupants all the time as the thermal comfort of occupants can only be achieved 51% of the time during heatwaves.

Identification of dynamic U-values for supply-air double windows based on experiments

Yujian Huang — 2022-05-19

The double windows with supply-air are recommended for both new and retrofitted buildings where preheating fresh air is needed especially when dealing with historical and protected buildings. To evaluate their energy saving potentials in buildings and optimize their performance, building energy simulations are necessary. In building energy simulation tools, the thermal transmittance (i.e., U-value) is one of the most important input parameters. The conventional U-value is a static indicator and a number of numerical studies have been proposed to identify U-value with varying window parameters. However, there is still a lack of laboratory experimental studies to get accurate U-value and evaluate numerical modelling results. Moreover, the performances of supply-air windows are related with environmental parameters and thus the use of conventional U-value might lead to a significant deviation between the simulated building energy and the real one. The purpose of this study is to provide dynamic U-values which could be varied according to environmental conditions. Firstly, an adapted guarded hot box is set up and it is calibrated by controlling air velocities and air temperatures in both cold and hot sides. Secondly, the U-values of supply-air windows are measured with varying environmental parameters and window parameters. Thirdly, the regression analysis is applied to describe the correlation between U-values and the influential factors, and thus one can easily evaluate U-value under different environment conditions. A future work is to integrate the regression correlation with energy simulation tools to have a comprehensive exploration of supply-air windows in different climate regions.

Sizing a collective heat pump system in an apartment building

Matthias Criel — 2022-05-20

Current sizing of collective heating systems utilizes conservative methods to size the capacity of the heat production unit, which results in an over sizing of the system. When collective heat pumps (CHP) are considered, an exact sizing would increase their competitiveness on the market. Residential user patterns are often not considered in the sizing strategy, neither is the simultaneity between central heating and domestic hot water (DHW) demand. This paper aims to identify the impact of occupancy patterns on sizing of a collective heat pump in an apartment building. The use of an occupancy-based heat and DHW demand model opens the possibility to reach a more appropriate sizing of the collective heat pump. This occupancy-driven model includes time dependant occupancy, temperature set points and DHW consumption. The impact of the occupancy patterns is analysed by building energy simulations (BES) in Open Studio for a case study apartment building in Belgium. A collective heat pump (CHP) system is considered where the link between consumption (building) and production (CHP) is made through a buffer tank. The production of DHW is individually supported by booster heat pumps heating up a small buffer tank. The simulation results illustrate that only 42% of the summed design capacity for heating and DHW is required to cope with the heat demand. It can be concluded that there is a significant impact of the occupancy profiles on the sizing of the collective heat pump system in this case study.

Predictive and flexible system controller for hybrid power supply systems

Martin Knorr — 2022-05-20

Regarding the overall efficiency of hybrid power supply systems, a system controller as an addition to device controllers was developed to contribute to its increase. An essential premise in the development of such a controller was the modular structure and the implementation as an open source solution. By using the MQTT protocol, the controller can operate within an IoT-network and hence be used universally, e.g. in a Software- (SiL) or in the Hardware-in-the-loop (HiL) environment as well as in field test. In order to make optimal use of the flexibilities provided by thermal or electrical storages, MPC (Modell Predictive Control) functionalities were implemented in the controller, which, however, are supported by rule-based algorithms on a â€œfallback levelâ€. The target values of the control can be adjusted variably and include economical as well as ecological aspects in a weighted way. The open structure of the controller makes it possible to easily include other system components in the control concept and also to operate the controller either locally, in an edge device or in a cloud environment. The performance of the controller was demonstrated by SiL- and HiL-tests. Here, annual characteristic values were determined on the basis of representative days. The representative days were selected using a cluster procedure. Overall, energy and cost savings can be demonstrated by using the controller, which are particularly effective in the optimized use of electricity from photovoltaic systems in combination with heat pumps.

Innovative heating and cooling systems based on caloric effects

Hicham Johra — 2022-05-20

Heat pumps (HPs) are an excellent solution to supply heating and cooling for indoor space conditioning and domestic hot water (DHW) production. Conventional HPs are typically electrically driven and operate with a vapour-compression thermodynamic cycle of refrigerant fluid to transfer heat from a cold source to a warmer sink. This mature technology is cost-effective and achieves appreciable coefficients of performance (COP). The HP market demand is driven up by the urge to improve the energy efficiency of building heating systems coupled with the increase of global cooling needs for air-conditioning. Unfortunately, the refrigerants used in current conventional HPs can have large greenhouse or ozone-depletion effect. Alternative gaseous refrigerants have been identified but they present some issues regarding toxicity, flammability, explosivity, low energy efficiency or high cost. However, several non-vapour-compression HP technologies have been invented and could be promising alternatives to conventional systems, with potential for higher COP and without the aforementioned refrigerant drawbacks. Among those, the systems based on the so-called “caloric effects” of solid-state refrigerants are gaining a lot of attention. The caloric effects are large entropy and adiabatic temperature changes caused by the application or removal of an external field in certain specific solid materials. There are 4 main caloric effects: magnetocaloric, elastocaloric, electrocaloric and barocaloric. Each of them is characterized by the nature of the field and the response that induces the entropy and adiabatic temperature change: variation of the magnetic field, uniaxial mechanical stress, electrical field or hydrostatic pressure, respectively. A HP cycle can be based on these caloric effects and several heating/cooling prototypes were developed and tested over the last few decades. Although not mature technologies yet, some of these caloric systems are well suited to become new efficient and sustainable solutions for indoor space conditioning and DHW production. This paper aims to raise awareness in the building community about these innovative caloric systems. It sheds some light on the recent progress in that field and compares the performance of caloric systems with that of conventional vapour-compression HPs for building applications

A common European EPB Assessment and Certification scheme. U-CERT's proposal

Pablo Carnero — 2022-05-20

Buildings are responsible for great share of the global GHG emissions. Increasing buildingsâ€™ energy efficiency is crucial to decarbonise the EU. For energy performance policies and requirements to have actual impact on buildingsâ€™ direct and indirect emissions is crucial to develop robust, accurate, meaningful and user-friendly assessments and certification schemes. This paper presents a methodology .to calculate building energy performance fully compliant with EPB Standards. Also, it proposes a selection of holistic indicators aiming to overcome shortcomings of national energy performance certificates, while being compliant with the latest version of the Energy Performance in Buildings Directive (EPBD). The results have the ambition of laying the foundation for a common European EPB assessment and certification scheme.

Parameter analysis of air-conditioning systems for high-tech cleanrooms considering climate impact

Wenxuan Zhao — 2022-05-20

The air-conditioning systems for high-tech cleanrooms are usually energy-intensive, due to strict temperature, humidity and particle concentration requirements. Their system performance strongly depends on the operation parameters and climate/weather conditions. But few studies have investigated such impacts for high-tech cleanrooms. Therefore, this study has quantified the impacts of operating parameters on the performance of high-tech cleanroom air-conditioning systems under different climate conditions via parametric and sensitivity analysis. A typical high-tech cleanroom located in Chinese five climate zones is selected to examine each parameterâ€™s impact using Energyplus/Matlab platform. Results indicate that the system annual energy consumption shows nearly linear changing trends when varying the operation parameters. The outdoor air exchange rate and MAU (make-up air handling unit) outlet air temperature are the most sensitive parameters in cold zones. The studied results can help practitioners improve air-conditioning system design and operational performance for high-tech cleanrooms through carefully determining parameters with heavy impacts.

Flexibility deployment of a heating system with heat pump in residential towers

Beatrix Bos — 2022-05-20

The transition from fossil fuel energy sources to renewable energy sources requires flexible use of our energy consumption to prevent congestion in the electricity grid. The heating systems of buildings are large energy consumers and can play an important role in matching electricity generation and demand. This research evaluates the amount and value of the potentially available flexibility from the heat pump in a case study on the heating system of two residential towers in The Netherlands, named Stoker & Brander. The thermal mass of the buildings is used to store energy to prevent heating during moments when grid congestion is likely to occur or when renewable energy production is low while maintaining comfortable indoor temperatures. To assess the potential energy flexibility, a building performance model and a financial model are developed to compare the influence on the energy flexibility when using different thermostat setpoint schedules. The total heat demand, the shifted load, the comfort, and the saved costs when deploying flexibility are selected as key performance indicators. With the model, 9 different thermostat setpoint schedules are tested with varying preheating duration and with varying timing before peak hours. In general, the schedules with a 2-hour preheating duration show the best results in terms of comfort and potential saved costs, while the timing before the peak hours has less effect on the results. The analysis on the saved costs is done with electricity prices of 2019, representing the current market, and with 4 price scenarios for 2030, representing the future market. The savings significantly increase for 2030, showing a large future potential for flexible deployment. However, it remains difficult to make a correct estimation of the predicted future savings as the scenarios show large differences between each other due to large uncertainty about the future prices. Nevertheless, for all scenarios at least 20% of the electricity purchase costs can be saved in 2030.

Energy efficiency and indoor climate benefits of demand-based ventilation in simulated office rooms

Vili Kohtaniemi — 2022-05-20

The demand for high energy efficiency of office buildings with an increasing focus on safety and good indoor air climate has increased the use of demand-based HVAC systems. The varying occupancy of office spaces can lead to unnecessarily high ventilation airflow rates and cooling of the room when there are no occupants. To achieve the same level of indoor climate with a more traditional ventilation system causes high energy consumption and inefficient operation of the HVAC system. A comparison of three active chilled beam systems was made with energy simulation software for finding the best performing room configuration in realistic operating conditions. Office room and meeting room cases) were simulated with 1) traditional CAV (Constant Air Volume) ventilation system, 2) BCV (Boost Controlled Ventilation) system with 2 automatic operating modes and 3) DCV (Demand-Controlled Ventilation) system with 3 automatic operating modes. For BCV and DCV systems same active chilled beam unit was used for office and meeting room cases to highlight the possibility of office layout changes without additional modifications to the ventilation system. CAV ventilation system required change between two different chilled beam units for office and meeting room cases to maintain the same level of indoor climate. Energy consumption, indoor climate conditions, and cooling system operation were simulated. The office building was located in a middle European temperate climate and had generic building materials and energy-efficient window characteristics Operation of demand-based ventilation system control logic for controlling airflow rates was studied between CO2 control and CO2 control with added presence control. The most energy-efficient solution was DCV system having 3 operating modes as the energy savings based on the ventilation airflow rates required at minimum operating mode is large compared to normal or maximum operating mode. With BCV active chilled beam ventilation system having 2 operating modes, energy efficiency can be increased notably compared to CAV active chilled beam ventilation system. BCV ventilation system could have performed with lower energy consumption for office room case if the active chilled beam was designed to be used for only office room operation, and not for meeting room operation as well.

Simplified CFD for pressure drop predictions in ducts

Thijs van Druenen — 2022-05-20

In the design of a ventilation system, the ductwork is generally composed based on analytical equations in combination with loss coefficients. This widely used approach can lead to large deviations in the prediction of the total pressure drop. Poor performance optimization could on its turn lead to a higher energy demand. While the use of computational fluid dynamics (CFD) could improve this prediction, it is often not feasible in practice as the use of CFD requires a high computational demand and a high-level of expertise. An alternative could be the use of simplified CFD. In this study the application of several conventional and simplified CFD methods and analytical prediction methods in the ventilation system design process was assessed. The simplified CFD methods include the use of coarse-grid CFD and voxel-based CFD simulations. Measurements on a single and double elbow configuration were performed and were used for validation purposes. For the investigated configurations the analytical prediction started to deviate from the measurements with increasing complexity of the system. For the conventional and coarse-grid CFD methods the prediction of the pressure drop was highly sensitive to the applied near-wall treatment and roughness parameters. For the voxel-based CFD method an average percentage difference of only 3% with respect to the measurements was found for the single elbow configuration. However, it overestimated the measured pressure drop by 64% on average for the double elbow configuration. A general sufficiently accurate method for predicting the pressure drop, which would also be feasible for use in practice ventilation system design, was not yet found. As this paper is part of a larger study, the assessment of additional simplified CFD methods on more complex duct configurations is the subject of future work.

Self-adaptive dynamic indoor climate control for museums, archives and libraries. Vast energy savings at Hermitage Amsterdam museum

Rick Kramer — 2022-05-20

The indoor climate in museums usually is conditioned strictly to the “golden standard” of 21˚C and 50%RH. It is evident that strict climate control hinders sustainability targets, but also hinders a robust long-term preservation practice. Research at Eindhoven University of Technology (2012-2017) has yielded the concept of dynamic indoor climate control for heritage institutions and its energy saving potential has been validated rigorously. In 2019, the spin-off DYSECO further developed this concept to a control-module that can communicate with any type of Building Management System. The algorithm of the controller calculates optimal adjustments to setpoints for temperature and RH adhering to the boundary conditions set by the user, considering limits and permissible rates of change of temperature and RH. The Hermitage Amsterdam museum has played a vital role in the research and development since 2014 and employs the DYSECO control solution in all exhibition spaces since 2020. Energy data is presented based on 5 years of high-quality data acquisition. The positive effects on collection preservation due to mitigated risk under HVAC failures are demonstrated using state-of-the-art dynamic building simulations with dynamic collection damage models.

Heat Pumps and Renewables in District Heating – Evaluation of Central and Decentral Approaches

Fabian Ochs — 2022-05-20

The decarbonization of the building stock and thus of district heating (DH) systems is one of the main future challenges in the building sector. It is controversial which role district heating will play in the future, i.e. to what extent an expansion of DH is beneficial and necessary, but it is undisputed that DH will take or hold a relevant share. With the increasing decarbonisation of the electricity mix, the use of heat pumps (HP) in buildings will be significantly more competitive than (existing fossil-based) DH systems, at least in terms of CO2 emissions. On the other hand, especially in urban areas and in existing buildings, the use of heat pumps is limited and also technically and economically challenging (source exploitation, space restrictions, architecture, sound emissions, etc.). Decarbonisation of DH might include waste heat, geothermal or solar thermal and heat pumps (in combination with electricity from renewables). Both, decarbonization of DH and electricity mix is challenging and full decarbonization requires electrical and thermal energy storage. Based on the energetic and ecological evaluation of exemplarily DH systems, different variants considering heat pumps integration, i.e. large central HPs central DH or block-wise or decentral i.e. building-wise, or apartment-wise are compared and evaluated. The assessment includes the own-consumption of the Photovoltaic (PV) yield and is then expanded to include various scenarios for the development of the electricity mix and the decarbonisation of DH.

Humidification in healthcare facilities - knowledge base and practice

Marcel Loomans — 2022-05-20

Humidification is not a common procedure in many buildings in the Netherlands. An exception are buildings used for healthcare, especially hospitals. There, e.g. in operating theatres, relative humidity (RH) generally is controlled stringently at levels around 50%. From an energy point-of-view humidification is an energy-intensive activity. Currently, more than 10% of the total energy used in healthcare buildings is spent on humidification. The basis for an RH of around 50%, however, is not clear. Therefore, we pursued a scoping review to find evidence for specific RH thresholds in such facilities. In addition, an inventory was made of the current practice in the Netherlands. After analyzing the title and abstracts, the remaining references were read by two persons and scored on several topics. Guidelines and current practice were analyzed by referring to existing (inter)national guidelines and standards, and by contacting experts from Dutch hospitals through a survey and semi-structured interviews. Outcomes from the literature review were grouped into four different topics: 1) micro-organisms and viruses, 2) medical devices, 3) human physiology and 4) perception. No scientific evidence was found for the currently generally applied RH set-point of ~50%. Some studies suggest a minimum RH of 30% but the evidence is weak, with exception of medical devices if specifications require it. A lack of research that addresses more long-term exposure (a couple of days) and includes frail subjects, is noted. It was found that RH requirements are strictly followed in all hospitals consulted, some only focusing on the hot zones, but in many cases extended to the whole hospital. Steam humidification is mostly applied for hygienic reasons. but is quite energy-intensive. The conclusion t is that there is no solid evidence to support the RH-setpoints as currently applied in the Netherlands. It merely appears a code of practice. Therefore, there appears room for quick and significant energy savings, and CO2 emission reductions, when considering control at lower RH values or refraining from humidification at all, while still fulfilling the indoor environment requirements and not negatively influencing the health risk. This outcome can be applied directly in current practice with the available techniques.

Simulation-based seasonal underground sensible heat storage integrated in a district heating network

Bram ter Meulen — 2022-05-20

This study assesses the role of (seasonal) thermal energy storage in the next generation renewables based central heating systems for the built environment in the Netherlands. Specifically, the neighbourhood "Karwijhof" in the city Nagele which is transitioning to a collective renewable district heating network incorporating 24 users. The study focus on the technology for storing thermal energy and two different heat collection technologies. The storage of heat is done using an underground seasonal thermal energy storage (USTES), in this case an underground sensible heat storage tank using water as storage medium. The system relies on a small scale district heating network (DHN) for the distribution of heat. For this research two heat collection technologies are considered both incorporating the USTES as main system component. The first system relies on heat collection by solar thermal collectors, the second on an air-water heat pump. Both systems are modelled in Matlab-Simulink making use of KNMI weather data. Different system sizes are evaluated. The investigated components include: volume of the USTES, surface area of the solar thermal collectors, and air-water heat pump capacity. Key performance indicators include the levelised cost of heat (LCOH) and the seasonal COP of the system which gives an indication on the autonomy of the system. To increase the autonomy of the systems a photo-voltaic (PV) array is considered for both systems to offset the electricity use. However, the systems are allowed to exchange electricity with the grid translating into the goal of "zero on the meter" autonomy. The results show that both systems can ensure heat throughout the year for the users considered during this study. However, systems cannot compete with traditional natural gas heating systems based on the LCOH. This is partly due to the high cost of the district heating network. The systems including a PV array show a LCOH that can compete with the traditional natural gas HR-boiler but are constraint by the rooftop area available during this study leading to a non-competitive LCOH. When considering the environmental benefits, the systems are already competitive to the traditional natural gas heating systems.

Optimized district heating system for combined operation with seasonal heat storage

Gijs Wolbert — 2022-05-20

This study optimizes the district heating network side of a high temperature community heating system powered by decentralized solar collectors and seasonal thermal energy storage (STES). Six network configurations are considered which have the potential to improve system performance compared to a base scenario. The base scenario consists of a 2-line network with a fixed supply temperature where the decentralised solar collectors feed in over the heating network. All alternative configurations aim to improve system performance by lowering the temperature of consumed and/or produced heat. Lowering the temperature in the heating network reduces heat losses and decreases heat pump utilization. Lowering the operational temperature of the solar collectors increases their efficiency. The strategies explored by the different configurations include variable supply temperatures, a 4-line network (where the solar collectors do not feed into the heating network), and ways to mitigate temperature constraints imposed by domestic hot water production regulations. In the neighbourhood “”Karwijhof” of Nagele, 24 consumers will make the switch to a solar+storage district heating system. In order to assess their performance, all configurations and the base scenario are modelled in Matlab/Simulink. The system performance is measured in terms of levelised cost of heat (LCOH) and seasonal coefficient of performance (SCOP). They are compared to a scenario where the dwellings are fitted with individual high temperature air to water heat pumps. Making the supply temperature variable (dependent on the ambient temperature) reduces pipeline thermal losses and reduces heat pump utilization. The transition from a 2-line network to a 4-line network where the solar collectors are separately connected to the buffer was found to significantly increase solar collector efficiency. The combination of these two measures reduces the LCOH by 4.5 %. Slightly oversizing the buffer volume and solar area significantly increases the SCOP with small impact on LCOH. When comparing the improved community solar heating system with a scenario where every house is heated with an individual heat pump instead, it is found that the community solar system achieve a 15.7 % lower LCOH while having a SCOP of 4.4 compared to just 2.75 for the heat pump scenario.

New forecast control of heat for heating

Tomasz Cholewa — 2022-05-21

In many existing buildings, the reduction in energy consumption has already been made by carrying out the thermal modernization of the building envelope. Therefore, other renovation measures, aimed at further increasing the level of energy efficiency in such a buildings, will focus in particular on improvement of control and automation of the processes of supply, as well as storage and use of energy.
This paper presents the field results of applying forecast control of heating system, which can be easily employed in existing buildings (time of installation in existing buildings: below 2 hours) and may work with existing, widely used weather controller. The new methods (applied in forecast controller) used for the creation of real energy model of the building (energy characteristics of buildings and their heating systems) and for forecast of heat power for heating are presented. The field research was conducted for a multi-family building located in Poland for part of a single heating season. The analyzed multifamily building in the first part of research was regulated only by a traditional weather-based controller, whereas forecast control system was used in the second part of research. The application of the proposed forecast control allowed decreasing the supply temperature of heating medium, lower the heat power supplied and in such a way generate energy savings of above 10%.

Experimental and CFD comparison of driver's thermal plume with classical air diffusers

Amaury Jamin — 2022-05-21

In confined spaces, such as vehicle cabins, airflow is one of the most critical factors affecting thermal comfort and pollutant dispersion. To develop innovative and energy-efficient HVAC systems, a deep understanding of the jet flows' interaction from air diffusers on the thermal plume became essential to improve our knowledge of airflow patterns for optimizing ventilation system design, thermal comfort, and indirectly, energy efficiency. We have developed a 1:1 scale mock-up with transparent walls, replicating a Renault Megane's interior in a climatic chamber and associated complex numerical models. PIV and IR measurements were firstly performed for the pure thermal plume with a thermal manikin in a driver's seat in this 1:1 scale mock-up. The experimental and numerical results showed good agreement regarding ranges and distributions. This paper presents experimental and numerical comparisons performed without and with ventilation systems to evaluate this interaction for classical air diffusers as a part of our larger project. The flow structure in the car cabin is complicated with existing large- and small-scale vortices. With an active ventilation system, the thermal plume is stronger in front of the head, the opposite of what has previously observed back the head. The airflow moves forward along the ceiling. The presence of the steering wheel distorts the flow direction at the thigh level. The additional velocity field on convective upward velocity in the shoulders' region is caused by impinging jets from diffusers. The Coanda effect caused by the central diffuser's flow creates a nonuniform and asymmetrical air distribution in the shoulders' region. A qualitative comparison of the jets' velocity distributions shows that the velocities are more uniform with innovative LAG diffusers than with the classical ones. This shows clearly the benefits of passive flow mixing to improve the thermal sensation.

Evaluation Dutch final nZEB requirements for University buildings

Mike van Osta — 2022-05-21

The need for (nearly) Zero Energy Buildings (nZEBs) in the Netherlands becomes increasingly important due to climate change, increasing energy prices, scarcity of fossil fuels and increasing geopolitical conflicts. In line with the EU EPBD, from January 2021 new buildings, including hospital and university buildings, have to fulfill more strict energy requirements. Besides that, also the energy requirements for existing buildings will become stricter to realize an energy neutral built environment by 2050. On request of the Dutch Universities (WO) and the Dutch Academic Medical Centreâ€™s (UMC), the Netherlands Enterprise Agency (RVO) assigned Royal HaskoningDHV to study the effect of the nZEB requirements on this real estate of the sector. The feasibility of the final nZEB requirements has been assessed for eight representative, recently designed and realized university buildings. The results show that:

· Compared to the provisional nZEB requirements it has become less difficult to fulfil the final nZEB requirements and sometimes even less difficult than using the former method (NEN 7120) and requirements (EPC);

· Five of eight university buildings comply with all nZEB requirements and three buildings do not comply with the nZEB requirement on primary energy (BENG 2);

· Effective and necessary measures in general are: good thermal isolation, energy efficient lighting with daylight and occupancy control, ventilation with heat recovery and CO2/occupancy control, Aquifer Thermal Energy Storage with Heat Pumps and local PV solar panels.

Although the nZEB requirements are feasible, organizations should keep in mind that fulfilling these requirements for only their new buildings is not enough to meet the 95% CO2 emission reduction target in line with the Paris Climate agreement in 2050. A roadmap with all measures to reach this target, including the existing buildings, should prevail when making design and energy transition decisions for the campus energy infrastructure and each building.

Hybrid photovoltaic-thermic system with enhanced cell energy efficiency

Marius Branoaea — 2022-05-21

Interest towards green energy has been increasing over the past decades, due to the increasing effect climate change and unsustainable energy sources pose to the planet. Among the renewable energy sources only solar, hydropower and wind provide substantial potential, while geothermal, wave energy, and biomass provide a local solution.
Solar energy has the potential of being one of the worldâ€™s largest energy providers, due to the fact it is present in every corner of the earth and can be converted with ease into electric energy and thermal energy using photovoltaic(PV) and solar panels.
Hybrid systems generate significant quantities of electricity and also generate heat. Photovoltaic-Thermal(PVT) systems have the potential to reduce the energy consumption in buildings, reducing both thermal and electrical energy, thus reducing the operation costs.
This study aims to design, model, and test the energy efficiency of a PVT system to overcome the main drawbacks of photovoltaic panels.
The main challenge photovoltaic panels face is overheating which leads to a reduction in the cells efficiency and energy production, overcoming this is through cooling and recovering the excess heat with the cooling agent. At the same time using the recovered thermal energy to supply the needs of the building in terms of heating and hot water, either directly or as a preheated primary agent, a further reduction in terms of the building energy requirements is achieved.
This study analyses the performance and efficiency of three original design hybrid photovoltaic systems using water as a cooling agent.
Through cooling a photovoltaic panel with a cooling agent with various flow rates, the efficiency of the photovoltaic cells is maximized, and through keeping their temperature as close to the nominal operating cell temperature (NOCT), the study aims to prevent degradation through overheating and cooling cycles during the day and night.
Through cooling a PV panel with water as a coolant, the efficiency of the photovoltaic cells is increasing from 17.85 in the case of the uncooled panel to over 19% in the case of the water-cooled systems at a flow rate of v = 3 l/min and v = 5 l/min.

Going active

Elli Nikolaidou — 2022-05-21

With several countries having declared a climate emergency and set decarbonisation targets, the built environment is expected to change radically. Several building standards have been developed to reduce carbon dioxide emissions from buildings, but they do not provide a clear pathway to a net zero future. The recently launched Active Building Code (ABCode) offers guidance on minimising the environmental impact of the next generation of buildings termed Active Buildings (ABs). This is achieved through their synergetic relationship with the grid. This paper presents our two-stage investigation into the stakeholder perceptions of ABs. In stage 1, we collected thoughts on the future of the built environment through a series of online focus group discussions with 30 industry experts. In stage 2, we quantified the ideas that arose from stage 1 through an online survey of 30 academics and researchers. Participants answered four questions, namely: (i) what is missing from existing regulations and standards; (ii) what is an AB; (iii) how should the performance of ABs be assessed; and (iv) what are the challenges to the popularisation of ABs. The data that was collected from the focus groups and the survey was analysed visually and statistically using logistic regression to identify the aspects stakeholders find important when envisioning the next generation of buildings. No significant differences were, in general, observed between the two groups, with industry and academia agreeing that whole-life carbon, energy demand, and energy flexibility should be used for the performance assessment of ABs – therefore aligning with the metrics suggested by the ABCode. Both groups interpreted ‘activeness’ as responsiveness, with industry experts highlighting the need to better define the relationship between buildings and the grid. They also regarded people’s mindset as the biggest challenge faced by ABs, due to the general tendency to make decisions based on capital cost. Academics and researchers also worried about the cost of technologies involved, which is however expected to drop over time. Results should be used to inform regulations and standards to make sure these are comprehended by all stakeholders and ultimately drive down carbon on all building projects.

Life cycle analysis of warehouse-type constructions

Ionut Emil Iancu — 2022-05-21

This paper conducts a comparative analysis of the life cycle for industrial warehouse-type buildings, intending to compare the embodied emissions and the embodied energy for the assessed cases and at the same time draw practical conclusions for practitioners. The analysis aims to identify the optimal solutions for the conformation of industrial buildings as well as the sustainability, from components choice and structural solution approach.
Four industrial buildings with different structural solutions, building envelope components, and destination are assessed: 1st case: a steel structure with production and storage as the main activity, having the destination of warehouse construction and energy storage and distribution; 2nd case: a mixed structure made of steel and wood used as a production space, namely glued laminated timber production; 3rd case: a commercial warehouse made of prefabricated concrete elements, intended for storage and sale of construction materials; 4th case: a commercial warehouse made of prefabricated concrete elements with metal roofing, intended for storage and sale of household goods. The analysis was performed using the Athena Impact Estimator software by imputing the description for all the materials describing the components, the locations of the buildings, the destination of each building, and other relevant data. Based on the preliminary results it was concluded that the industrial building made of prefabricated concrete elements (i.e. 3rd case scenario) is the most balanced and sustainable in terms of carbon and embodied energy.

From collective to individual decision-making

Shima Ebrahimigharehbaghi — 2022-05-21

The building sector can contribute considerably to reducing global greenhouse gas (GHG) emissions. In the Netherlands, the GHG emissions must be mitigated by 95% by 2050 relative to the 1990 baseline. Various factors, such as low renovation rates cause uncertainties in reaching these targets. The current study aims for investigating the barriers and opportunities regarding the energy efficiency renovations (EER) and programs offered by the cities in the Netherlands. Homeowners encounter individually and collectively different forms of barriers during their journeys of EERs. By collective decision-making, we mean when an individual
homeowner cannot make the final decision on EER by themselves. Homeowners may have to decide together with other homeowners or even tenants in case of living in a multi-family dwelling. The local authorities sometimes offer the energy efficiency programs at neighbourhood levels and the agreement of most households is essential for the continuation of the energy efficiency programs. The literature review, semi-structured interviews and focus groups are conducted with experts from the largest cities in the Netherlands. The focus groups and interviews are used to examine the barriers and opportunities especially at neighbourhood and street levels. Our main initial findings include the barriers of (a) Individual homeowners: difficulties in making them interested to conduct EER, lack of knowledge for the starting point of renovation, additional barriers of following many steps in conducting EERs for the old dwellings;
(b) Homeowner associations: difficulties in reaching agreement by 70% of homeowners, timeconsuming process for agreement, and not well-organised meetings by all the homeowners' associations; (c) Neighbourhood level: cultural diversities, difficulties in finding solutions for different groups of people, etc.

Development and characterization of thermal insulation materials based on rice straw and natural binder

Yaping Zhou — 2022-05-21

Thermal insulation is an essential factor to reduce energy demand during the stage of building operation. Nowadays, thermal insulation materials are however commonly produced from petrochemicals, causing high energy consumption and detrimental environment impact during production and arising the reuse and recycle issues. Insulation materials derived from local agricultural straws are becoming more attractive due to their availability, cost effectiveness, sustainability and low carbon footprint. Rice straw has the advantage of low density and low thermal conductivity due to its hollow internal structure. Also, the utilization of rice straw in buildings prevents the negative environmental impact of burning straw or mixing them with soil. The aim of this study is to develop an innovative composite insulation material from rice straw. A biobased binder, i.e., sodium alginate, derived from brown algae is used as binder. A modified method is developed to solve the water solubility issue of the composite material. The final product is rigid, lightweight and fully eco-friendly. The effect of fiber size and binder ratio (i.e., 8%, 16% and 24%) on the density, thermal conductivity and water vapor permeability are studied. The composite materials are insulating with thermal conductivity values in the range of 0.039-0.045 W/(m·K) for an average density in the range of 100 to 200 kg/m3.

Study on reproducibility of exhaust diffusion properties of gas water heaters

Saki Nakano — 2022-05-21

When installing a gas water heater in a common corridor, the common way of the installation in Japan, there are restrictions on the installation location and the shape of the corridor in order to avoid the exhaust gas stagnating in the corridor and flowing into the rooms through the vent. Therefore, the standards limit the building planning and require more relaxation. We had been conducting experiments by using full-scale models over the past years, however, as there are many shapes of common corridor, it is difficult to examine all the possibilities. It is necessary to reproduce the exhaust properties on computational fluid dynamics (CFD) so that the examination of reference relaxation can be performed by simulation using CFD. We needed to collect target data to confirm reproducibility by actual measurement. It was ejected without any obstacles to the jet flow, and we measured the velocity, temperature, CO2 concentration, etc. We estimated that the model of the interface on a gas water heater and setting boundary
conditions can be the factors to improve the reproducibility.

Analysis of Internal Leakages of Residential Ventilation Units by various test methods

Marie-Teres Moser — 2022-05-21

Internal leakages of bidirectional residential ventilation units (RVU) have a negative impact on hygiene and energy efficiency. Therefore, internal leakages are an essential part of the European standards and should be a requirement and part of the energy labelling in the revision of Regulation EU 1253/2014. The current test standard defines a static pressure method intended for RVUs with plate heat exchangers. In addition, there is an in-duct method and a chamber method, using tracer gas, for air handling units (AHU) with rotary heat exchangers. The Eurovent Product Group Residential Air Handling Units launched a project to analyse these methods. The project was also supported by the Swiss Federal Office of Energy and GebäudeKlima Schweiz. Two AHUs, one with plate heat exchangers and the other with rotary heat exchanger, were tested with all three methods. The finding was that the results of the different methods were not comparable. A Master's study confirmed this with a third RVU. Hence, a new method was introduced, the so-called Advanced Pressure Method (APM). This approach allows testing without tracer gas, but with comparable results to the in-duct method. The APM is based on a node model of the flow paths within the RVU. All in all, the APM is a reliable approach to determine the internal leakage, even though the measurement uncertainty is higher than with the in-duct method. The accuracy is limited due to the sensitivity of the mathematical model. Therefore, the APM has been proposed for the use of the APM in manufacturers' laboratories. Furthermore, in the EN 13142 standard, the internal leakage is used to correct the temperature efficiency. The current test standard leads to results that depend not only on the quality of an RVU, but also on the test method. In addition, test conditions that are not clearly defined, e.g. rotary speed, have an effect. The project is intended to open the discussion on the three mentioned test standards and their influence on energy labelling.

Thermal performance of a supply-air window with triple heating glazing inserted in building envelope

Salem Zeiny — 2022-05-21

Nowadays, no one ignores that the building envelope plays a major role in terms of energy consumption and greenhouse gas production. Successive regulations have mainly resulted in a reinforcement of thermal insulation and an improvement of the airtightness of the envelopes. But this often results in poor estimations of consumption, condensation problems on the walls and poor air quality.
Our project consists in analyzing the contributions of a glazed, supply air and heating façade component that provides the ventilation, the heating of the building and the recovery of solar and fatal energy. It is based on a supply-air window of type "Paziaud" in which a heating glass has been inserted. A prototype has been installed on the façade of a building and has been extensively instrumented. Measurements of surface temperatures and air temperatures, pressure difference and velocity are completed in an original way by a fluxmetric instrumentation placed in the ventilated air gaps of the window and on the surfaces in contact with the interior and exterior environments.
This paper will allow us to share and discuss the first results obtained in this in-situ configuration. Our experimentation highlights the difficulties that arise in the interpretation of measurements in real sites, more or less disturbed during the day and at night by the variations of meteorological parameters. It is also a question of coming back to the definition of the performance indicators by comparing theoretical formulas and practical results. In particular, it is necessary to take a closer look at the definition of the outside temperature, which is involved in the expression of a surface transmission coefficient adapted to the component and to discuss an efficiency factor for the window which functions as an exchanger. It is also important to take into account the different heat sources (solar radiation, electricity and recovered waste heat), the heat convective exchanges coefficients that take place in the air gaps and the definition of performance indicators.

Numerical analysis of a thermal energy storage tank charged with a flat type solar air collector

Guven Hasret Yilmaz — 2022-05-21

As energy and sustainability issues related to climate change gain importance day by day, the significance of energy storage systems is increasing. Carnot Batteries, where energy can be stored thermally, constitute one of the most outstanding alternatives for the storage of excess electrical energy produced from renewable energy in the concept of smart cities. The energy is stored in the Carnot Batteries during the hours when the electricity demand is lower than the electricity production, the energy stored in the Carnot Batteries is converted into electricity during the hours when the electricity demand is higher than the electricity production. In this respect, Carnot Batteries can offer a good solution to the imbalance between energy demand and production, which is a crucial problem in energy use, and therefore, it is likely that they will be an indispensable part of the future and smart city systems. In this study, a simulation covering the charging and discharging processes of a Thermal Energy Storage tank, which receives its energy from flat type solar thermal collectors, was carried out in MATLAB. In the simulation, a 6 m height tank was divided into 60 cells and discretized, the solar radiation values were calculated locally and a solar path was created. At the time of charging, the Thermal Energy Storage tank received its energy from the solar collectors, depending on the determined solar path. In the simulation, the effects of variables related to the energy storage media such as sphericity, void fraction, charging time were investigated.

An aquifer thermal energy storage model for efficient simulations of district systems

Elisa Scalco — 2022-05-21

Thermal energy storage systems are valuable assets to enable high penetration of renewable energy sources into district heating and cooling (DHC) systems. One of the main benefits of using thermal storage is that it can contribute to matching energy supply and energy demand when they do not coincide in time.
Aquifer thermal energy storage (ATES) is an attractive technology to provide sustainable heating and cooling to buildings through DHC systems. In ATES systems, storage and recovery of thermal energy is achieved by extraction and injection of groundwater using wells. To calculate the energy performance of ATES, most of the studies use detailed simulation models developed using computational fluid dynamics software. However, such programs have limited capability of simulating the integration of ATES into building and district energy systems.
The aim of this research study is to develop a simplified ATES model, which is suitable for coupling with building and district energy simulation programs. The model has been developed using a finite-difference approach in the MATLAB computing platform to solve the transient heat and mass transfer equations in porous media in two dimensions. The aquifer around the wells is modelled as two independent radially symmetric discs with an inner radius and an outer radius. The model has been validated by comparing predicted warm/cold well temperatures with measurements data from literature. Since the model is developed in MATLAB, it can be coupled with building energy software (such as TRNSYS, Modelica, EnergyPlus) via co-simulation.

Optimal design and operation for heat prosumer- based district heating systems

Haoran Li — 2022-05-21

Heat prosumers will become important participants for future district heating (DH) systems. However, the current unidirectional heating price models reduce interest in prosumers and hinder the promotion of prosumers in DH systems, because the prosumers gain no economic benefit from supplying heat to the central DH system. This study aimed to break this economic barrier by introducing water tank thermal energy storage (WTTES) and optimizing the operation of heat prosumers with WTTESs, considering the widely used heating price models in Norway. Firstly, a generalized heating price model was introduced, which could represent the current widely used heating price models in Norway. Secondly, the WTTES was integrated into the heat prosumer to improve the self-utilization rate of the prosumer's heat supply from its distributed heat sources, meanwhile, shave the prosumer's peak load. Afterwards, an optimization framework was formulated to optimize the operation of the prosumer with the WTTES under the generalized heating price model. Finally, a numerical method for solving the proposed nonlinear optimization problem was given. A case study showed that the proposed method could cut the prosumer's annual heating cost by 7%, and the investment of WTTES could be recovered in four years.

Next-Generation Energy Performance Certificates, What novel implementation do we need?

Lina Seduikyte — 2022-05-21

Energy performance certificates are being utilized through the European Union Member States to document and asses the energy performance of the building stock, while they are used as measures to investigate and adopt policies that would lower the final energy consumption and environmental footprint. After several years of implementation, the current EPC schemes have enlighten the domain energy efficiency in the building sector, but at the same time they have been identified with several challenges and deficiencies that deteriorate the quality of the results. This study performed under the H2020 project â€œNext-generation Dynamic Digital EPCs for Enhanced Quality and User Awareness (D^2EPC)â€œ, aims to analyze the quality and weaknesses of the current EPC schemes and aspires to identify the technical challenges that currently exist, setting the grounds for the next generation dynamic EPCs. The present work reveals that current EPCs schemes are based on a cradle-to-gate rationale, completing their mission after the certificate to the building user, overlooking the userâ€™s behavior and the actual energy performance of the building that might change dynamically within time. In this study, the idea of the dynamic EPCs is introduced, a certificate that will allow the monitoring of the actual performance of buildings and the usersâ€™ behavior profiles on a regular basis. The introduction of novel indicators and the integration of BIM and GIS are also discussed.

Economic and Energy Performance of Heating and Ventilation Systems in Energy Retrofitted Norwegian Detached Houses

Vegard Heide — 2022-05-21

The aim of this study is to compare the life cycle costs (LCC) and energy performance of different heating and ventilation systems (HVAC) in deep-energy renovation of Norwegian detached houses. More specifically, the relative performance of nine different HVAC combinations based on heat pumps is compared using two case buildings with four different insulation levels for the building envelope. The case buildings are small wooden dwellings without hydronic heating system, which is representative for existing Norwegian detached houses. The energy performance was simulated using the dynamic software IDA-ICE, in compliance with Norwegian Standards. The standard NS-EN 15459 (2017) was mainly used for the cost performance assessment. HVAC combinations with low investment costs (e.g., EAHP, balanced ventilation and air-to-air heat pump) showed lowest global costs, but the highest delivered energy. Low energy consumption can be achieved with different balances between investments on energy measures for the building envelope versus HVAC systems. Heat pumps can contribute significantly to the reduction of the energy use. In many cases, the cost uncertainty within one HVAC combination is larger than the difference between the combinations. The global cost and delivered energy diagram show a Pareto front relatively flat over a long range of energy use, so that some HVAC combinations can significantly decrease the energy use for a small increase in global costs. The compact heat pump and ground source heat pump fall into this category. For the investigated cases, the current governmental subsidies in Norway do not seem large enough to make investments in deep energy renovation profitable. Finally, results show that the prebound effect should be taken into account to make a realistic analysis of the cost performance of energy retrofit.

Bioclimatic Design and Advanced Strategies' Impacts on Energy Performance of Residential Buildings

Gizem Avgan — 2022-05-21

The construction sector covers a significant percentage of the energy consumption in the world. Human actions on energy use are gradually being identified as the primary cause of climate change, global warming, and significant environmental changes. In response to these problems, the concept of sustainability has become one of the most crucial solutions for reducing the construction sector's high energy demand. Bioclimatic architecture is a sustainability approach that brings forward the strategies of vernacular architecture into the present by adapting the building systems to their climatic and topographic conditions. It is also an option for affecting the building sector in Turkey to prevent energy overconsumption by initiating efficiency improvements. This study examines the design requirements and physical characteristics of a building in the Marmara region (Turkey) and how these features impact its overall energy consumption. The case study building is a 9 storey apartment building in ErenkÃ¶y, Ä°stanbul, located in the humid-temperate climatic region of Turkey. Since that, the design scenarios consisting of different bioclimatic strategy combinations are chosen about this climatic region's features. The software DesignBuilder, empowered with an EnergyPlus simulation engine, is used to test the design scenarios' impacts on final energy consumption. The present condition of the case study building is monitored to calculate its energy consumption to evaluate the difference between the design scenarios. The impact on the primary energy use of different passive strategies, HVAC systems, electricity generation, and a bioclimatic set of standards implemented to the building was then assessed using parametric analysis of various scenarios. The results showed that the combination of passive strategies with earth pipe installation and thermal assisted radiant floors reduced the energy use by approximately 30%. Passive strategies significantly impact the residential building systems' energy efficiency showing how bioclimatic architecture criteria can meet the requirements of high-efficiency standards in the humid-temperate climatic region of Turkey.

Solar Cooling Integrated Façades

Hamza Hamida — 2022-05-21

The global attention to solar cooling systems has increased during the last years as a result of the expected growth in the world cooling demand. Such systems encompass the use of renewable energy as the main driver for mitigating indoor temperatures. Currently, some of these technologies are mature enough for their commercial application in buildings. Building facades present high potential for the integration of such technologies. This is because of their direct effect on the indoor comfort of buildings, and also their ability to provide external surfaces exposed to the sun radiation. However, there are different challenges affecting the widespread application of solar cooling integrated façades. This paper aims to identify and categorize these challenges through conducting a comprehensive literature review. A literature review was conducted on scientific papers published in conference proceeding and scientific journals, through considering two databases, namely Scopus and Web of Science. Then the study suggested three main potential dimensions that should be tackled and integrated when supporting the widespread application of the façade integration a particular solar cooling technology. The dimensions include technical, financial, as well as process and stakeholder related aspects. Such proposed dimensions represent an initial step for identifying important aspects to be considered for supporting the product widespread application in the built environment.

Adaptive Envelopes for Better Energy Efficiency and Enhanced Indoor Thermal Comfort

André Badura — 2022-05-20

The increased use of renewable energy in the built environment is a key objective for sustainable development. While being a key priority for the future of energy use, renewable power generation is affected by local resource fluctuations, such as the amount of incoming solar radiation. Energy storage and increased energy efficiency will continue to gain importance in this context. In cold and moderate climates, heating has traditionally accounted for the predominant part of energy use in buildings. In many parts of the world, heating remains fossil-fuel based to a significant extent. Due to a number of issues, including climate change, the proportion of heating energy has been steadily decreasing, while cooling loads have been on the rise. The use of electricity for heating and cooling has been increasing, partly related to an increased use of different types of heat pump technologies. Growing electricity use for cooling is increasingly seen in highly-insulated, low-infiltration, high energy-performance buildings, but also in other parts of the building stock. High levels of insulation efficiently decrease heat losses during the heating season, but they also impair the removal of excess heat. This study explores how adaptive envelopes can be used to optimize the use of solar radiation during the heating season and enhance the removal of excess heat during the warm part of the year, depending on parameters including outdoor and indoor temperatures and the desired levels of thermal comfort. The IDA-ICE energy and indoor-climate simulation tool is used for exploring different adaptive envelope scenarios. It allows the calculation of heat flows through the walls, currently however without considering the impact of radiation on external walls. To compensate for this, a new approach is presented to simulating heat flows through different types of adaptive envelopes and wall constructions. This allows for a more detailed understanding of how adaptive envelopes allow incoming solar radiation in summer to be stored before it is transmitted to the main wall structure. Conversely, a more detailed analysis becomes possible of how accumulated heat can be released during the night by removing insulating layers of the wall, thus cooling the indoor environment.

Experiment-based testing routine to characterize building energy flexibility for potential aggregators

Vojtěch Zavřel — 2022-05-21

The ultimate goal is to introduce a standardized routine to characterize flexibility of a given building for the purpose of potential flexibility aggregators. The routine should provide the characteristic demand response of the building under various smart-grid control signals (e.g. time-of-use (stage) pricing, real-time pricing etc.). The scope of this paper is limited to the experimental part, that demonstrates measured demand response provoked by testing sequences. The testing sequences were applied via cloud-based service to the building management system (BMS) of a mid-size office building in Prague. The evaluation is not limited only to power metering but also includes indoor environment quality (in terms of room air temperatures and CO2 concentrations), HVAC system and local meteorological data monitoring. The air handling unit (AHU) and cooling system response were investigated using ‘step’ and ‘modular’ testing sequences. The real-life experiments revealed authentic demand response allowing to characterize building flexibility in full details. The key findings are, that the operation of the HVAC system components can be blocked for relatively long period of time (2 to 5 hours in studied case) without any critical consequences to the indoor environment quality. Approximately 30 % of the total power load per the testing event can be considered as flexible. The quality of the power profile was found highly irregular. Due to the power profile fluctuation the ramping/modulation at the single building level was found ineffective. In contrary to the modular control, the multi-stage control led to more detectable power reduction. The stage type of control provoked more observable, reliable, and easier-to-predict demand response.

Energy-saving and IAQ control in hospital patient room by bed-integrated ventilation

Zhiqi Wang — 2022-05-21

The annual energy-saving potential and IAQ improvement by use of a hospital bed-integrated pollution source control, a ventilated mattress (VM) and local bed ventilation (LBV), was studied. The VM is designed to capture in the bed and exhaust human body bio-effluents. The LBV is supplies clean air close to the breathing zone of the patient in bed and exhausts the polluted (might be infected) exhaled air from the patient before it is mixed with the room air. Exhaled air removal efficiency of the LBV were assumed at 40%, 60% and 80%. Thus, the risk of cross-infection was reduced. Energy use simulations were performed by IDA-ICE software. Intake fraction was used to indirectly assess the risk of cross-infection. Three scenarios were simulated to evaluate the energy-saving potential of the source control methods: 1) a double-patient room (none of patients is infected) using the VM and constant air volume ventilation (CAV), 2) a double-patient room (either one or two patients is infected) using the VM and CAV and 3) a double-patient room (either one or two patients is infected) using the VM, the LBV and CAV. The results reveal that using the VM and the LBV at decreased background ventilation rate can be an effective method for reducing the energy costs needed for hospital wards. Depending on the operation of the VM and the LBV, the energy-saving was between 1880 kWh and 67964 kWh. The annual energy-saving was up to 83.6% when the ward with two infected patients using LBV at 80% exhaled air removal efficiency and CAV at a reduced ventilation rate, compared with the reference cases of only CAV operating at 12 air changes per hour (ACH).

Modelling of District Heating Systems

Guokai Chen — 2022-05-21

District heating systems are prevalent in most European countries, and such energy delivery methods can be crucial to decarbonisation objectives. To appropriately size and design the control of such networks, the modelling of district heating networks should have a good representation of the demand-side, which is the set of buildings connected to the network. In-stead of simplified modelling of the demand, whole-building simulation tools can be invoked in this case, like EnergyPlus. More recently, equation-based libraries have been developed in Mod-elica for component-based simulation of HVAC systems. Modelica-based libraries offer easier model composability and are particularly interesting for control fine-tuning; on the downside, the model setup can be more complex, with more validation needed. This paper conducts a comparative study of the Modelica LBNL Buildings library against Ener-gyPlus, based on an archetype-based hypothetical case in the UK with a small-scale district heating system. The methodology resides on models developed in the two tools with the same level of modelling detail. The comparison helps understand software differences in the model-ling procedure, computational time, relative accuracy of energy predictions and heating system variables. The results indicate Modelica Buildings library yields similar accuracy in terms of heat transfer calculation through thermal zones as EnergyPlus, whilst capturing additional en-ergy consumption caused by the dynamic changes at system startup and the realistic controllers used in the Modelica district heating models. Meanwhile, the Modelica Buildings library’s out-puts show the fluctuations of system variables, indicating different operation patterns and con-trol effects against EnergyPlus. This study also proves that the Modelica Buildings library is the better tool for district heating simulation in the context of dynamic performance evaluation and control testing, based on overall capabilities, limitations, and prediction differences.

Numerical investigation of an evacuated tube solar collector in a solar assisted rooftop unit

Tunahan Akış — 2022-05-21

In this study, numerical analysis of an evacuated tube solar collector integrated into the discharge line in a rooftop air conditioner is carried out. The goal in this system is to increase the efficiency of the unit by reducing the compressor energy consumption with the solar collector. The solar collector consists of vacuum tube collectors. Inside the vacuum tube, there is a copper pipe installation through which the R410a refrigerant in the superheated vapor phase, which is compressed by the compressor, passes. The remaining volume from the copper pipes in the tube is filled with a heat transfer fluid to increase the collector efficiency. In this study, the type of heat transfer fluid filled to the collector for the operating condition of the unit in summer and winter conditions are investigated parametrically and numerically. With the findings obtained, the surface temperature of the copper pipe installation in the collector in the compressor discharge line, depending on the type of heat transfer fluid, is presented comparatively.

Numerical analysis of ventilated windows' thermal behaviour under summer condition

Shiva Najaf Khosravi — 2022-05-21

Efforts to develop advanced building envelope components have pursued, among other things, ventilated window constructions. To properly configure ventilated windows, both the operation mode and the climatic context must be taken into consideration. In the framework of a previous research project, an instance of a ventilated window (outdoor air curtain mode) was implemented in a testbed and was subjected to experimental studies under summer conditions. In the present contribution, we numerically evaluate the thermal behavior of this system via computational fluid dynamic (CFD) simulation. Specifically, we compared simulation results with measurement data to evaluate the accuracy of the simulation model. Thereby, the main objective was to explore the fidelity of the CFD model and its potential for supporting the design of ventilated windows. To this end, the utility of the CFD was demonstrated in terms the optimization of the design of a ventilation window (exhaust and outdoor curtain mode). In the course of this study, we numerically analyzed the thermal behavior of the two modes of ventilation window operation (exhaust and outdoor curtain mode) under summer conditions. The results of the CFD-based investigation suggest that the application of low-emissivity glazing as the exterior glass pane can improve the cooling effect in both cases. In addition, the exhaust mode of the ventilated window shows a better performance under summer boundary conditions.

Passive cooling techniques to improve resilience of nZEBs in Belgium

Alanis S. Zeoli — 2022-05-21

Nowadays, buildings are responsible for 40% of energy consumption in the European Union, according to the International Energy Agency (IEA). The urge to build more energy-efficient buildings resulted in the emergence of nearly zero-energy buildings (nZEB). However, the specifications the nZEB design should comply with might not be sufficient to prevent the risk of overheating in summer. To limit the energy consumption rise linked to the upcoming cooling demand increase, passive cooling techniques can be used instead of active ones, that are characterised by a high energy consumption. Passive cooling techniques are investigated through a dynamic simulation of a nearly zero-energy dwelling in Belgium. Their efficiency is assessed based on their ability to improve thermal comfort. The passive cooling techniques can be combined to ensure the resilience of the building to global warming. It was found that the most efficient techniques are the ones relying on ventilative cooling. Solar protections and smart glazing also offer an efficient protection against overheating. The effectiveness of the combined passive cooling techniques is studied over an extreme meteorological event, which is likely to occur by 2100 in Belgium if nothing is done to prevent global warming. Twenty days of intense heat are studied to evaluate the resilience of an nZEB. It was found that the most efficient combination includes night cooling, thermochromic glazing and indirect evaporative cooling. Those techniques allow to decrease the indoor temperature by almost 10 K.

Data-driven statiscal and machine learning modelling of real building stock energy use

Matthias Van Hove — 2022-05-21

One of today’s major challenges is to become climate neutral by 2050. Large potential for energy reduction is found in the building sector (which accounts for 40% of Europe’s total primary energy use). To compare energy reduction strategies, Building-Stock Energy Models are vital instruments. Yet, the regulatory energy performance calculation (which is currently used by EU policy makers) poorly predicts the real building energy use in residential buildings and largely overestimates the potential energy savings. Promising data- driven black-box models are gaining considerable traction in a wide range of applications. This paper evaluates whether data-driven linear regression and gradient boosting machine models provide better predictions of the real total building energy use at large scale as compared to the current regulatory white-box building energy calculation method. Compared to the performance of the regulatory method, both the linear regression models and the gradient boosting regression trees perform better (gradient boosting regression trees slightly worse than multiple linear regression). Yet, a large part of the variance in the linear regression models is left unexplained and also for the gradient boosting trees, there is room for improvement. At individual building level, it is clear that both the linear regression model performance and the gradient boosting regression tree performance is too poor for inference. At stock level, however, both types of models seem promising and can be a useful tool to inform big housing owners (e.g., financial institutions, governments, housing companies etc.) or for policy making.

Performance evaluation of a R-290 dual-source heat pump for heating and cooling

Laura Alonso — 2022-05-21

In this paper, the performance of a 10 kW reversible heat pump using R290 as refrigerant and using a dual source/sink is presented. The heat pump design is oriented for its integration with solar photovoltaic energy in multifamily near Zero Energy Buildings, with the objective to reach a high onsite renewable share. The development is part of TRI-HP project: Trigeneration systems based on heat pumps with natural refrigerants and multiple renewable sources. The heat pump has a specifically designed dual source heat exchanger (DSHX) working as the outdoor unit of the heat pump. This element is able to work as a condenser (cooling mode) or evaporator (heating mode), exchanging heat between the refrigerant and air or water/brine as heat source (in heating mode) or sink (in cooling mode). Both sources can also be simultaneously used as heat source or sink. The design procedure and used correlations for the DSHX are described. The heat pump has been experimentally tested in a climatic chamber in all the possible different working modes (Heating with air, heating with brine, cooling with air, cooling with brine), showing in general a good agreement with the design values. Results for coefficient of performance, heating/cooling capacities and compressor consumption are presented for different air/brine temperatures and different compressor velocities. The experimental campaign has served to validate the developed models for designing the DSHX. Future work includes an improved redesign of the heat pump with a more compact DSHX and a simplified refrigerant circuit, which will be experimentally tested in an analogous experimental campaign.

Energy performance retrofits targeting national strategy development for typical Turkish school building

Hazal Kızıldağ — 2022-05-21

Today, most existing buildings should be retrofitted to reduce the negative impact on the environment. According to the EPBD, Member States should prepare national action plans to increase nZEB. Therefore existing buildings must go under deep refurbishment. Educational facilities are a critical segment of the public sector, and a frequently used building type with high energy needs. In Turkey, more than 17 million students spend the majority of their time in school buildings, hence increasing energy efficiency in existing educational buildings not only contributes to the environment and can create healthy and comfortable indoor conditions for the students, but also creates an awareness of the youth and increases their learning performance. This study focuses on analyzing the effects of various retrofitting applications of the building envelope and HVAC systems on the energy performance of a school building to improve existing energy consumptions. Analysis of the building envelope is an important primary step towards achieving a low energy level, as other energy efficiency measures such as buildings' HVAC systems’ efficiencies. The aim is to reduce the heating and cooling demand of the selected building and to increase its energy performance. The analysis of the case study showed that there is no insulation layer on the outer wall as a result of the measurements. Therefore, the first step is to observe how the appropriate insulation layer affects the energy performance of the building. The methodology consists of energy modeling of the case study building in DesignBuilder and obtaining energy performance results by EnergyPlus software. Various retrofit scenarios were prepared into packages which include alternatives of thermal characteristics of the opaque elements such as external walls and roof, application of different glazing units, and implementation of solar control elements. These variables were combined and compared in terms of their effects on total primary energy consumption, heating and cooling demand. Based on the results, technical suggestions were given according to the best performing scenarios. It is expected that the research outcomes will contribute to the studies to improve the energy performance in educational buildings.

Validation process of energy performance simulation a Turkish school building case

Gökçe Tomrukçu — 2022-05-21

Buildings produce one-third of the world's carbon emissions. It is estimated that the energy needs of buildings will increase by 40% until 2040 unless measures are taken. A significant portion of the energy in Turkey is consumed by non-residential construction sectors such as educational buildings. Therefore, efforts to improve the energy performance of educational buildings are essential to minimize the environmental impacts of the building stock. Building's energy simulation provides the possibility of testing various scenarios to define their pros and cons. However, the difference between the simulation results and the actual energy consumption should be minimized in practice. The study aims to monitor energy consumption and validate the simulation results of typical school buildings in Istanbul, Turkey. The approach consists of creating dynamic energy performance simulation models and validating with onsite measurements, energy bills and climatic data of the measurement period. At the first step, the detailed schedule of the occupants and mechanical systems, the building envelope materials, the lighting system, devices information, capacity, and efficiency values of mechanical systems and electrical equipment were obtained and defined in the DesignBuilder software. The U-values of the exterior walls were obtained through in-site measurements. In the next step, interior temperature, relative humidity, and CO2 in the building was measured based on related standards and regulations (ISO 7726 and ASHRAE Guideline 14). As a result, the validated energy model based on a comparison of simulation and measured data can be applied and tested to achieve a high energy performance level in the school building.

Concise cycle test methods to evaluate heating/cooling systems with multiple renewable sources

Robert Haberl — 2022-05-21

The goal of the project TRI-HP is to develop systems based on electrically-driven natural refrigerant heat pumps coupled with photovoltaics to provide heating, cooling and electricity to multi-family buildings with an on-site renewable share of 80 %. The implementation of different energy sources for such a system often leads to a complex architecture of the overall system. The performance evaluation of such systems is not trivial and cannot be done via steady-state measurements of individual components. Instead, dynamic measurements using the hardware-in-the-loop approach are performed to test the performance of the newly developed systems. A method called concise cycle test (CCT) has been developed for this purpose. This method was adapted to the systems to be tested and applied in different versions. The CCT method is based on the selection of several representative periods of the year, and shows the behaviour of a complete system for heating and cooling under relevant conditions in these periods, enabling then to extrapolate the results for a whole year operation. Two different approaches were used to select the test sequence. For the measurement of a dual source/sink system, the annual weather data were divided into four clusters, from each of which representative days were selected. For the solar-ice-slurry system, a single, contiguous test cycle of typical days from throughout the year was selected. This allows both, to test the functionality of the ice-slurry storage and the advanced energy management strategies by performing experiments only on selected days. For the tests, the complete system including a heat pump and thermal and electrical storages are installed on a test rig. The test rig emulates a building, including the space heating and cooling distribution system, the domestic hot water draw offs, the solar collector field or ground heat exchanger depending on the system tested and the photovoltaic installation. The system tested must act completely autonomously to cover the demand for heating and cooling of the building and the draw-offs during a test cycle. In this work, the methodology has been applied to two different cases of complete systems adapted to different climates (Switzerland and Spain).

Development of an energy analysis tool for data center free cooling technologies modelizzation and comparison in different climate conditions

Mauro Mantovan — 2022-05-21

Data Centers are currently undergoing a great period of change. Developments in business and personal data transfer together with new technologies such as virtualisation and cloud computing are transforming Data centers into dynamic environments with greater power demands unexpectedly. The cooling requirements of the Data Center infrastructure form a large part of the overall power requirements and it is therefore critical to ensure correct optimisation to achieve the desired energy efficiency levels. In Planning data centers for the future, it is imperative that the design matches the infrastructure with greater scalability and integration enabling Data Centrers to evolve to cope with less power demands and lower running costs. This work brings together the main layouts of high efficiency IT cooling systems, highlighting their operation and efficiency in the case of an IT room with a thermal load of 1 MW and three different climatic scenarios. The efficiency of the systems is evaluated through a calculation routine in which all the components of each cooling system are modelled and the regulation logics of the software of these units are implemented. The climatic scenarios for 3 different locations (Palermo, Milan, and Frankfurt) are represented according to the hourly distribution of temperatures and humidity in order to evaluate the seasonal performance of each cooling system. The results give an overview of the consumption referred to each IT cooling technology in relation to the application climate. The calculation routine developed allows to choose the most suitable technology for the climate and the installation considered, also leaving the possibility of a subsequent optimization of the unit design based on the most appropriate technology.

Performance analysis of heat pump assisted desiccant cooling system through experiment

Tae-Ha Leigh — 2022-05-21

The building heat resistance performance and air tightness are more and more developed. According to this, especially in hot and humid climate, the latent load easily increases and occupant comfort decrease. Because of this the importance of dehumidification grow higher and higher. Heat pump assisted desiccant cooling (HPDC) system is one of the systems to control the indoor humidity while using less energy than conventional condensation dehumidification and general desiccant cooling system by using condensation heat as regeneration heat for desiccant. And the disadvantage of HPDC system, which is hard to control the temperature, is supported by using radiant ceiling panel (RCP) to control the room temperature. The object of the paper is analyzing the energy performance and thermal comfort satisfaction of HPDC system and analyze the adaptability of HPDC system combined with RCP (HPDC w/RCP) through experiments. In experiment 1, HPDC system used 55% lower energy consumption compared to packaged air conditioning system (PAC) and can satisfy comfort zone rather than PAC system, especially in humidity comfort range. In experiments 2, HPDC w/RCP system satisfied ASHRAE comfort zone 12% more than HPDC system and used 5% lower energy. The experiment performed in this study can prove that the HPDC system is a possible alternative system of conventional cooling and dehumidification systems and HPDC w/RCP also has possibility to enhance the thermal comfort and energy saving.

Biomass in District Energy Systems

Lorenzo Teso — 2022-05-21

Buildings are one of the major users of energy in the European Union, accounting for almost half of the total consumption. In this scenario, renewable energy sources play a fundamental role in the transition towards a low-carbon society, and promoting their use is vital for the future of Europe. This work focuses on the use of district heating networks supplied with energy from biomass as a form of sustainable development for cities and communities, with attention to the Italian situation. After a first introductory part dealing with the European context of district energy networks, the focus shifts to Italy. It is introduced the diffusion on the national territory of district systems with a description of the most used energy sources that power these systems. To demonstrate how the use of biomasses in district energy networks represents a valid alternative to fossil fuels an analysis of the utilization of forests for wood harvesting in the Italian energy sector is carried out, showing how greenwoods and forests can withstand even greater exploitation for the collection of wood material for energy production. In order to prove the feasibility of the switch, a case study district, representative of the Italian residential building stock, is analysed. The district is firstly studied to evaluate the energy demand for space heating, and subsequently investigated by comparing different strategies for its energy efficiency improvement, all dealing with materials coming from wood processing, and switching from a decentralized energy system based on fossil fuels to a centralized network supplied by biomass. The results of the analysis show interesting results in primary energy consumption savings at least 38%, highlighting the potential of the demonstrated approach. Final remarks explain that, with the correct support of policies and awareness on the status of national forestry ecosystems, benefits are achievable through more intensive use of forests, leading to a higher share of natural feedstock in materials for the energy enhancement and energy production, that will help in reaching European sustainability goals.

The impact of occupants' energy awareness and thermal preferences on buildings' performance

Florian Regnath — 2022-05-22

Recent research efforts in building performance simulation increasingly focus on the representation of people's behaviour (specifically, their interactions with buildings' control systems). In this context, the use of agent-based modelling (ABM) is suggested to be a promising approach, as it can capture, in principle, the complexity and dynamics of the patterns of individual occupants' presence and behaviour in buildings. The present contribution describes a related effort, whereby an agent-based model (generated using the NetLogo application) was coupled with a dynamic building simulation model to examine the impact of occupants' energy-related behaviour on buildings' energy performance. To this end, four user types were defined in the agent-based modelling environment. These occupant types were assumed to correspond to different energy awareness levels as well as different tolerance levels with regard to indoor-environmental conditions that are deemed to be desirable. The behavioural model is linked to the dynamic energy simulation tool EnergyPlus via co-simulation using the Building Control Virtual Test Bed tool and Python programming language. A case study object (specifically, six single-occupancy office spaces in an office building) was selected to simulate the impact of different occupant types on the building energy performance. The simulation results suggest that the awareness level of occupants regarding energy conservation issues can have significant influence on the computed energy performance of the case study building. Moreover, occupants' level of tolerance regarding deviations of indoor-environmental conditions from "optimal" settings, was likewise shown to influence energy use. Finally, the case study highlights existing usability challenges concerning co-simulation processes involving both ABM and performance simulation.

Multi-zone Dynamic Simulations for Investigation of Occupant Behaviour and Building Performance

Elisa Venturi — 2022-05-22

The study aims to investigate the correlation between occupant preferences, occupant thermal comfort and building energy performances by means of dynamic building simulations. Moreover, the design power of a central heating system is studied in correlation with an increasing number of occupants with non-standard behaviour. A building consisting of 24 office rooms and a common traffic zone, distributed on 3 floors is simulated in MATLAB Simulink environment. The heating demand evaluated considering the climate of Stuttgart accounts for 49 kWh/(m2a), which decreases to 17 kWh/(m2a) when the mechanical ventilation heat recovery is implemented, i.e. thermal building quality according to the Passive House standard. Furthermore, the climates of Rome and Stockholm are considered to take into account the effects of different boundary conditions. A floor heating system is implemented in every office room and the hot water is supplied by a central heat pump. Non-standard behaviour (i.e. setpoint temperature, window shading, window opening and a combination of them) in an increasing number of offices is implemented to study the impact on the heating demand, on the thermal comfort (room temperature and floor temperature) and on the design power of a central heating system. Peculiar behaviours of some of the occupants can have a relative influence on the building performance. For example, extensive ventilation in only one office can have the same impact on the building space heating demand as higher setpoint or shading in several offices at the same time. Results of the dynamic simulations address the robustness of a central heat pump compared to an electric system. Moreover, a general correlation between the number of office rooms with non-standard behaviour and increase of space heating demand cannot be found as the correlation depends on climate and quality of the building envelope. Finally, the position of the office with non-standard ventilation has an impact on the required heating power.

Smart thermostatic valves based heat generator control to cut heating bills

Max Boegli — 2022-05-22

The following work aims at demonstrating how a smart thermostatic (radiator) valve network can be used to reduce heating costs by controlling the heat generator (heat-pump, gas boiler, ...) in a more efficient way. Currently, a large proportion of heat generators is controlled by the means of a heating curve, or a similar rule-based logic that mostly rely on outdoor temperature or single point indoor temperature measurements. These simple control laws are in general commissioned to minimize the number of complaints of “cold users”. This results in high forward temperatures, that are energetically non-optimal as they create increased losses in the piping network and also have a negative impact on the heat generator efficiency. In the proposed data driven approach, a controller was developed to ensure that the radiators receive fluid with the lowest temperature possible, while satisfying the heating needs. To achieve this goal, smart thermostatic valves are used to monitor the radiator activity. The monitored information is used by a real-time algorithm to adapt the hot water temperature to continuously ensure user comfort. The solution was deployed in a multi-apartment building located in Neuchâtel (Switzerland). The solution has been running with success during the 2020-2021 heating season. The results point out that an average saving of 15% is obtained with respect to the baseline (i.e. heating curve) controller under similar conditions, without any degradation of comfort (under heating in particular). The system will now be deployed on 6 houses in Denmark and remain active at least until 2023.

Optimal dispatch strategy for building aggregators to fully utilize the energy flexibilities

Hong Tang — 2022-05-22

Well-managed demand-side flexibility can effectively alleviate the pressure on the reliability of the power system and the advanced development of smart grid technologies creates win-win opportunities for the power system operators and demand-side users. The
building sector, as one of the largest consumers of electricity, has great flexibility potential through smart load control and natural thermal mass storage. However, few studies have investigated the potential contribution of buildings in providing multiple flexibility services without sacrificing the occupants’ comforts. Another major hurdle to utilizing the building energy flexibility is that individual buildings usually cannot reach a sufficient size to bid the flexibility services in the electricity market. Therefore, this paper proposes an optimal dispatch strategy for building clusters using mixed-integer non-linear programming (MINLP) to aggregate and utilize full-scale energy flexibilities of variable controllable loads, the passive thermal mass storage and active electrical storage systems. The building cluster consisting of five commercial buildings is selected in the case study to test the proposed strategy and analyze
the practical relevance based on a real-life electricity market. Results show that the proposed dispatch strategy reduces the electricity costs of the building cluster by 11.6% from multiple revenue streams, including energy arbitrage, regulation service and operating reserve service. Active electrical storage systems can increase revenues by 2.3 times and the unlocked flexibility of building thermal and lighting loads can achieve 152 $ daily revenues. This study addresses the issue that the energy flexibility of individual buildings is too small to bid flexibility services, and the findings may stimulate the investment of the distributed storage system at the aggregated level, as the building aggregator is a promising business model in future flexibility markets.

Transparent dynamic insulation

A.J.H. Frijns — 2022-05-22

Greenhouse horticulture cultivates vegetables, fruits, and flowers in protected glass houses. Approximately 65%-85% of the total energy in greenhouses is used for heating. To reach the climate goals energy reduction is needed. Energy savings cannot only be achieved by improving the insulation value of the greenhouse covers since also the relative humidity of indoor air needs to stay below a critical humidity level to avoid fungus growth. Therefore ventilation is required with an average air change rate (ACH) of 2.5/h. This is often realized by (partly) opening and closing the glass greenhouse cover thereby losing part of the heat. In this paper, we focus on a novel method that improves the thermal insulation of transparent top covers and/or walls while ensuring sufficient ventilation: transparent dynamic insulation (TDI). TDI is based on a concept called Dynamic Insulation, also known as a "breathing wall": infiltrating air flows through the multi-layer insulation panel. While doing this, the incoming air takes up part of the heat and uses this for pre-heating. Thereby it reduces the overall heat transfer value (U-value) and provides pre-warmed, fresh air flow into the greenhouse. The main difference compared to “traditional” dynamic insulation is that its design is transparent for solar irradiation and therefore can be used for greenhouses. In this paper, we show experimental results on a TDI prototype panel using a hot box apparatus with an ACH=2.5/h and prescribed temperature differences between indoor and outdoor of ΔT=10OC and ΔT=20OC. It is shown that the measured overall U-value for the TDI panel is about 19% lower than for double glass and more than a factor 2 lower than single-layered Hortiplus glass. Therefore it is concluded that TDI is a promising approach to reducing energy consumption in greenhouse horticulture while ensuring sufficient air refreshment for moisture control.

A comparative study of solar cooling technologies

Beethoven Narváez-Romo — 2022-05-22

The environmental impacts of refrigeration and air conditioning applications include synthetic refrigerant fluids use and the high demand for electrical energy for activation, being critical in places whose energy mix depends on fossil fuels. Brazil has advantages due to hydroelectricity and the high incidence of solar irradiation, enabling solar energy technologies in refrigeration cycles. This work aims to study the technical-economic feasibility of photovoltaic energy to drive the vapor compression refrigeration system, and solar thermal energy for the ammonia-water and water-lithium bromide absorption cycles. It developed thermodynamic models of both vapor compression and absorption cycles using the mass and energy conservation equations under steady-state regime. The systems of linear equations were solved by using the Engineering Equation Solver - EES. One obtained the air conditioning thermal load profile and the characteristics of the thermal collectors and photovoltaic panels from EnergyPlus, from São Paulo-Brazil solar irradiation. Results showed that the monthly energy consumption is reduced from 626 kWh to 196 kWh, achieving a 44% reduction in the value of the electric energy bill for the photovoltaic solar cooling proposed when compared to the conventional one. A 7-years payback time is achieved. For the absorption cycle, the use of a flat thermal collector is unfeasible due to the need for natural gas as a complementary source of energy. It is concluded that solar cooling with photovoltaic has advantages compared to thermal activation, as the overall efficiency has a performance 30% higher than solar cooling by the
thermal collector. Results showed that PREUPV is always higher than PREUST.

Predicting the waterside temperature difference of a cooling coil in part load

Alet van den Brink — 2022-05-22

Chilled water plants must operate in the most energy efficient way possible. One of the threats to a good energy performance in part load is the ‘Low ΔT syndrome’, several causes of which are related to the cooling coils. In order to detect deviation behaviour of the waterside temperature difference (ΔT), one needs to know the normal return water temperature during part load operation of the cooling coils. However, until now it has not been possible to predict and quantify the waterside temperature in part load. This paper provides a mathematical derivation to predict the waterside temperature difference in part load. For a constant air and water flow, the performance is only determined by the nominal water leaving temperature and leaving air temperature. Both temperatures determine if the chilled water temperature decreases or increases in part load and the shape of the heat exchanger characteristic of the cooling coil. The result is tested for two known causes of the Low ΔT syndrome, namely 100% outdoor air handling units and economizers. The results show that placing the cooling coil behind (blow through), instead of in front of (draw through), the fan will result in an increased chilled water temperature difference in part load.

Advanced solutions to improve heat recovery from wastewater in a double heat exchanger

Mihnea Sandu — 2022-05-22

One of the main challenges in the world today is reducing energy consumption and CO2 footprint in existing buildings without major construction work. The main component of energy consumption in buildings is heating, but the demand for the domestic hot water is also very high, especially when daily consumption is high and especially for specific applications. The implementation of technologies using recovery sources for water heating has become very important and one of these technologies involves the recovery of the thermal energy from wastewater. Usually, heat recovery from wastewater is designed to recover residual energy from the hot drainage water and this recovered energy is used to preheat incoming cold water or to heat pumps. The paper presents numerical simulations using a SST k-ω turbulence model in order to compare a regular geometry with a helicoidal one. The second one provides a more turbulent flow that allows an intensification of the outer flow, thus allowing the enhancement of the heat transfer from the inner heated flow to the outer flow.

Decentralized storage in combined heat distribution circuits: how to control?

Stef Jacobs — 2022-05-22

In apartment buildings, collective heating networks have great energetic advantages. One form gaining more attention for the last decades is a combined heat distribution circuit (CHDC), in Belgium called “combilus”. It is a two-pipe system for the distribution of both space heating (SH) and domestic hot water (DHW). The supply temperature is set to the highest needed temperature, which is around 65°C for DHW (considering a temperature difference for enabling heat transfer). However, if decentralised DHW storage tanks in combination with low-temperature emitters for SH are used, the supply temperature could be optimised. In this research, two innovative control strategies were studied for such a CHDC to lower the distribution temperature (to the required temperature for SH) as much as possible by grouping the charging periods of those storage tanks. One control strategy is time-based, with pre-defined charging schemes, while the other is based on two sensors in the storage tanks. In order to test the control strategies, a simulation environment was set up in Matlab that represents the thermal dynamic behaviour of CHDC. However, to fully focus on the evaluation of the control strategies, an idealised central boiler room was assumed, which immediately delivers the desired temperatures. Besides the evaluation of the control strategies, the design of the storage tanks is also optimised by performing sensitivity analyses on the volume, hysteresis and charging flow rates. The results show that larger storage tanks provide better DHW comfort combined with less PE use (for the proposed controls) and that the charging flow rate can significantly reduce the central peak power, while DHW comfort and PE use remain the same. With the time-based control, the charging cycles and volume have a high impact on the performance and comfort. The two-sensor control is always able to reduce PE use and deliver the same or even better comfort than the reference control.

Evaluation of the intrinsic thermal performance of an envelope in hot period

Arnaud Jay — 2022-05-22

Ensuring the proper thermal performance of a building’s envelope upon reception is an important stage in the life cycle of the building. Several methods already exist for this purpose, and continue to be improved, such as co-heating, ISABELE, EPILOG, QUB and SEREINE. All these methods follow the common protocol consisting of heating the measured building with an electrical system. These measurement protocols quantify the dynamic evolution of interior and outdoor temperatures, and the thermal power injected into the building. These data are used in calibration algorithms to determine, by an inverse method, a heat loss value. These methods require a difference of a few degrees between the interior and the exterior which can cause in summer periods a risk of damaging the building, as the outside temperature may already be high. The objective of this work is to explore the possibility of determining the intrinsic thermal performance of a building’s envelope in the summer period using a cooling hydraulic system. Some encouraging experiments have been done on a square meter scale cell in an indoor environment. The focus of this paper is to test a similar method in an outdoor Passys test cell of 40m3 and explore the capacities and limitations of the method at this scale by varying several stress parameters of the enclosure. First, some electrical heating modes are run acting as reference values. Then, a hydraulic system is used to estimate the HLC value and gives comparable results to the electrical mode considering an uncertainty of 2 W/K. Third step is to setup cooling scenario with the hydraulic system. Some of the results are also comparable with the heating mode and some limits are highlighted such as the cooling power limitation to avoid water condensation into the cell. This impact of condensation is then studied and seems to have a limited impact on the results for this experiment.

Intelligent building envelope solutions in Finnish new and old apartment buildings

Azin Velashjerdi Farahani — 2022-05-22

This study investigated the effects of intelligent building envelope solutions (automated blinds, openable windows, and awnings as well as electrochromic windows) in Finnish old and new apartment buildings. Moreover, the results are compared to the passive solutions (manual blinds and solar protection windows). The main goal was to compare the performance of each solution in improving the indoor temperature conditions in Finland’s current climate. Thus, the solutions were simulated with the usage of a mechanical cooling system in the living room to see the effects on both the energy demand of the buildings and indoor temperature conditions in the warmest bedroom. Furthermore, indoor temperature conditions were analyzed in the warmest bedroom of the new
building without an active cooling system, as well. According to the results, electrochromic and solar protection windows are the solutions with the lowest cooling electricity consumption in the old building. However, in the new building, the lowest cooling electricity consumption is for the case with the automated openable windows and the next effective solutions are solar protection and electrochromic windows. Considering the results of indoor temperature conditions, the combination of solar protection windows and manual blinds is the most effective solution in the old building. While automated openable windows have the best performance in the new building with or without the active cooling system. Overall, passive solutions are more effective in both the old and new apartment buildings except for automated openable windows in the new building.

Potential of WASTE WATER HEAT RECOVERY in reducing the EU's energy need

Pavel Sevela — 2022-05-22

After extensive research, Waste-Water Heat-Recovery (WWHR) technology was identified as the most promising technology to unlock the under-addressed potential in reducing the energy need for water heating. Particularly interesting application of WWHR is for showering, which accounts for about 70 to 82 % of the daily residential hot water tapping profile. Shower-wise installed heat-exchangers offer a cost-effective way of utilizing otherwise wasted heat for preheating cold fresh water, thus reducing the temperature span covered by the water heater. The total energy demand savings for hot water heating can be up to 40 %. The unique advantage of WWHR, is achieving high thermal energy savings without compromising on user comfort with low material and monitary needs. The cost-effectiveness of WWHR is best in climates with cold ground temperatures and in cases where showers are used extensively. At European level, the WWHR itself is theoretically capable of surpassing the energy savings targets planned in the "Fit for 55" climate action in the hot water sector, if all buildings are equipped accordingly. If between 2022 and 2030, every second anyways renovated or newly constructed building in Europe were equipped with the WWHR system, 35.7 TWh less energy would have to be generated and 6,6 Megatons of CO2e emissions less emitted. Although WWHR has been a well-proven technology for decades in some countries; it is still unknown in most European regions. Further action, in particular the creation of a European legal framework, the training of professionals and the granting of subsidies, is needed to accelerate the adaptation of this promising, sustainable technology into practice.

Students’ self-reported health and psychosocial status at home before and during COVID-19

Amneh Hamida — 2022-05-17

During the COVID-19 outbreak, university courses were shifted online and students spent the majority of their time inside their homes. However, staying indoors can affect students’ health due to the exposure to several environmental stressors, such as background noise, and/or inefficient ventilation, and/or insufficient lighting. Previous studies showed that the indoor environmental factors may cause health effects on students (physiological and psychological). Therefore, this research aimed at investigating the differences in students’ health and psychosocial status between before and during COVID-19. An online questionnaire survey was completed by first-year undergraduate university students in March 2019, 2020, and 2021. This questionnaire includes questions about time spent at home, psychosocial status, diseases, and home-related symptoms. The mean number of hours that students spent at home during the weekdays and on weekends were calculated, respectively. Besides, occurrence frequencies of psychosocial statuses were calculated for each year. Furthermore, a statistical analysis, including one-way ANOVA and Chi2, were performed to examine the differences between the three groups in terms of time spent at home, psychosocial statuses, diseases, and home-related symptoms. It is worthwhile to note that students spent significantly more time at home, during the COVID-19 pandemic in March 2021. Another notable result is that students’ mood and emotional states changed significantly over the three years; for example, fewer students reported to be active and inspired in 2021. Moreover, the home-related symptoms, such as headache and tiredness, significantly increased in 2021, compared with the other two years.

Towards zero energy hospital buildings – energy saving opportunities in steam and humidification installations

C.T. Ferreira Porto — 2022-05-18

The healthcare sector is highly energy intensive with circa 6% of the total global energy consumption. For this reason, hospitals strive to reduce their energy usage, especially of the most energy intensive systems like steam and humidification installations. Centralized steam plants are widely used by hospital complexes since many hospital functions rely on steam to properly fulfil its purpose (e.g. air humidification, sterilization, space and water heating, kitchen boilers). Central steam plants are not the most energy-efficient method to supply the consumers’ demand due to the high energy and fossil fuel consumption for steam production and the consequent losses inherent to the extensive distribution installations. In general steam losses in steam system can represent over 30%. Total CO2 emissions for steam production can be over 20% of which humidification can represent over 50%. Therefore reducing the steam demand for humidification and implementing decentralized systems is of great importance for Hospital Buildings to fulfil for new buildings the nZEB requirements. In this paper the results of a literature study are presented and a method based on the so-called 5-step method [1] and the Kesselring method is used to select different systems based on their performances on different aspects. Solutions are presented that can save more than 50% of energy use and CO2 emissions used for the steam production.

Special Systems of Foul Water Stacks in High-Rise Buildings

Martin Sokol — 2022-04-23

Due to maximum usage of building lands in cities, the construction of high-rise buildings is currently having the greater importance. High-rise buildings are buildings that, due to their height, must be designed in a different technical, technological and constructional way. In addition to height, the dominant element of high-rise buildings compared to buildings with a smaller number of floors is the usable area, which is an important factor for an investor. The more floors a building has, the more complicated it is to provide requirements of hygiene and quality of sanitary installations. In sanitary technology, the biggest problem is in the design of foul water stacks, which must be given higher attention. The issue of foul water stacks in highrise buildings is a relatively complex and demanding topic, due to the complicated hydraulic conditions in the flow of foul water in drainage pipes. The design must be based mainly on research and knowledge, which is obtained mainly from foreign sources. This topic is not so developed in our country. Stacks must be designed in such a way that the negative pressure and the overpressure created in them do not cause suction of water from traps. When there is no water in the trap, an annoying smell from the drainage occurs in the building. Extraction of water from traps is not the only one problem. Other problems are excessive vibration and noise spreading from stacks through building structures to the interior. This can be caused, for example, by an incorrectly chosen system, piping material, anchoring, or offset of the stack. Special fittings and systems have been designed for high-rise buildings, which eliminates most of disadvantages of conventional solutions. The paper deals with the analysis of modern technical solutions that favourably affect the hydraulic conditions in stacks and thus help to improve the comfort users of building.

Spatiotemporal humidity variation in student housing

Cathrine Hafnor — 2022-05-18

Modern, urban apartments are space-efficient, have bathrooms with no windows, and require energy-efficient ventilation with heat recovery. The requirements for exhaust ventilation rates for the kitchen and bathrooms are independent of dwelling size. In some countries, it is required that the extract air can be increased on demand. There is a need for more knowledge on the effects of these requirements on the resulting moisture level in apartments, and whether these recommendations should be modified. Measurements were done in eight student apartments. Temperature and humidity were measured with 1-minute time resolution at 5 locations in each of the apartments. Median moisture excess was 0.9-1.4 g/m³, indicating a small risk of interstitial condensation. 90th percentiles of relative humidity were 30-35 %, indicating an elevated risk of eye and airway symptoms due to low humidity. The moisture excess was lower in apartments with heat-recovery ventilation than mechanical extract ventilation. The median moisture excess was higher in the living rooms than in bathrooms, indicating that moisture from showering and personal hygiene had little impact on the overall indoor moisture conditions in the dwellings. The average number of showers per day per apartment varied between 0.6 and 3.1. High peak moisture excess values up to 20 g/m³ were recorded in bathrooms, but for brief periods only. Consistently higher moisture peaks in extract vents than in bathroom air demonstrated that ventilation extract above the shower is effective in removing moist air from showering. Calculated moisture load in the extract air from a single shower was estimated to be 0.86 kg. Outdoor temperatures were negatively correlated with moisture excess, as predicted by EN -ISO 13788.

Air change rates during sleep in Danish bedrooms

Xiaojun Fan — 2022-05-17

The ongoing project ‘Bedroom Ventilation and Sleep Quality’ investigates the effects of bedroom ventilation on sleep quality and next-day cognitive performance. As part of the project, 84 bedrooms in the Greater Copenhagen area of Denmark were inspected during the 2020 heating season. In the first week, participants slept under environmental conditions that they typically experienced during sleep; in the second week, they slept with the interventions made by opening/closing either the door, or window, or both. As an essential part of the study, the CO2 concentration in bedrooms was continuously measured. The bedroom window and door status during sleep were obtained the following morning via sleep diary. The air change rates per hour (ACHs) in bedrooms were estimated using the occupant-produced CO2 concentration decay method. Mechanical ventilation was rarely installed in bedrooms; extract ventilation in the bathroom and kitchen was predominant. Participants typically slept with both bedroom window and door closed. The median ACH was 0.40 h-1 during sleep under habitual conditions. Opening either the window or door increased bedroom ACH during sleep, but window opening led to better ventilation than the door opening, which was verified by the intervention. These results suggest that the ventilation in most bedrooms is currently insufficient compared with the ventilation requirements prescribed by limited standards, highlighting the urgency to look at its impact on sleep quality and improve bedroom ventilation.

CO2 monitoring to assess ventilation rate: practical suggestions from a laboratory study

Dadi Zhang — 2022-05-17

Several recent studies have demonstrated that ventilation plays an important role in the transmission of SARS-CoV-2 (the coronavirus that causes COVID-19) in public buildings, such as schools. However, there are no clear rules on how to assess the ventilation performance in classrooms, especially during a pandemic. Therefore, the main objective of this study was to develop guidance to assess the ventilation performance under different ventilation regimes. A full-scale laboratory study was conducted in the Experience room of the SenseLab, where CO2 concentrations were monitored at 19 locations (18 indoors and one outdoors) simultaneously and recorded every 30 seconds by HOBO® CO2 loggers. The experiment was conducted under four different ventilation regimes: ‘600 m3/h mixing’, ‘open windows’, ‘no ventilation’, and ‘open windows and door’. Each regime lasted 50 minutes, which is approximately the duration of one normal lesson at Dutch secondary schools. Six (three males and three females) healthy subjects were invited to participate in this experiment as CO2 sources. Results showed that CO2 concentrations varied significantly between different measurement locations in the same classroom, especially under natural ventilation conditions. This demonstrates the need of monitoring the CO2 concentration, next to outdoors, at more than one location in a classroom. The finding of this study could contribute to a standardized way of monitoring CO2 concentrations and the assessment of ventilation performance of an occupied space.

Kitchen ventilation system design and its effect on restaurant IAQ

Kamal Moumen — 2022-05-18

It is well established that exposure to high level of Particulate Matter (PM), especially smaller particles below 2,5 micron (PM2.5) has a negative impact on health. We also know that cooking is the major contributor to PM levels in dwellings (Jacobs et al, 2016). A recent field study in restaurants (Kulve et al, 2020) also showed elevated levels of PM exposure, exceeding those recommended by World Health Organization (WHO). It is obvious that ventilation systems do not meet the objective of providing good Indoor Air Quality (IAQ) in restaurants with high level of PM exposure. This presentation addresses ventilation system design and its effect on PM level in the commercial kitchen setting. The study was conducte in a ventilation laboratory setting using a charbroiler and gas fryers cooking hamburgers, and French fries. Two types of ventilation hoods were tested as well as two air distribution strategies: mixing and displacement ventilation. The study replicated elevated levels of PM2.5 concentrations with inadequate ventilation design and demonstrated that properly designed ventilation system can protect kitchen personnel from high PM exposure. The study also emphasized the importance of IAQ sensors in restaurants to guarantee adequate performance of ventilation systems.

Cooking habits and usage of kitchen hoods in Norwegian homes

Adele Helene Ninauve Jutulstad — 2022-05-18

Sustainable urban development results in more space and energy-efficient apartments. Open plan solutions are becoming more common, and the market is exploring new configurations and ventilation solutions for the kitchen in direction of the design and minimize space for ductwork. Cooking is an important aspect of human life and is considered one of the major sources of particle emissions. The cooking method, the type of cuisine, and the type of kitchen hood are some of the factors that will influence this. In Norway, the minimum requirement for general kitchen exhaust is 36 m3/h, with a minimum additional forced ventilation by the kitchen hood of 108 m3/h. However, these requirements might not be sufficient to mitigate the exposure from cooking. Electricity is the main heating source, traditionally with hot plate, today mainly induction or ceramic cooktop. In this work, we aim to investigate representative Norwegian cooking habits, typical meals and set up a procedure for cooking in the laboratory to perform intensive exposure studies. A survey has been performed to identify the type and usage of kitchen hoods in different living situations as well as typical Norwegian meals. A total of 336 people responded to the survey, of which 111 provided answers to a few additional questions. More than 60% of the respondents belonged in the age groups 30 – 60 years old and 92% owned their dwelling. Wall-mounted kitchen hoods were found in the majority of the homes, and almost 4% had downdraft. Only 12% of the homes had recirculating hoods. 76% of the respondents used the kitchen hood during cooking. The Norwegians mainly cook or fry their food, while deep-frying is not common. For the question related to what meal is most often cooked, the categories of food that were most mentioned were pasta dishes, taco, meat, fish, boiled potatoes, and chicken. Based on this we developed the cooking procedure for three different test meals suitable for exposure studies.

Cooking emissions from typical Norwegian meals

Adele Jutulstad — 2022-05-18

Sustainable urban dwellings are built space-efficient, and open-plan kitchens have increasingly become the norm. A study of newer building projects has shown that the kitchen space is in the inner area of the apartment with limited options for forced window airing, leaving the job of removing cooking emissions to the kitchen hood or general ventilation. One of the aims of our study is to measure exposure from actual cooking in modern apartments, as preparations for further advanced studies. To achieve this, particle number concentrations (>0.3 μm) are measured for three typical Norwegian meals with different ventilation rates at three locations in the kitchen lab. The kitchen setup is comparable to the EN 61591:2019 standard with an area of approximately 30 m2 and a height of 2.7 m. The measurements show that the meals and cooking procedures developed are reasonably repeatable. Most of the particles are in the range 0.3-2.5 μm. The meal producing the lowest numbers of particles is the vegetarian pasta Bolognese, while taco and fried salmon which required both higher cooking temperature and contained more fat resulted in a much higher number of particles. The peak for particle number concentration was more than 40% lower for the vegetarian meal. Turning on the kitchen hood at medium setting (286 m3/h) drastically reduced the particle number concentrations, however, the Norwegian requirement of 108 m3/h (low) resulted in a 58% reduction for the taco meal.

Experimental analysis of the ventilation rate in an amphitheater operating under the COVID-19 pandemic constraints

Luisa Dias Pereira — 2022-05-18

In the context of the Covid-19 pandemic (officially declared by the WHO on March 11th, 2020), indoor air quality (IAQ) has resurged as a renewed paradigm, demanding enhanced attention, especially in spaces with high occupancy density, as is the case of school buildings. To minimize the risk of contamination indoors, it is needed to assure low concentrations of the biological pollutant load eventually resulting from the exhalation of the microorganism SARSCOV- 2, through the dilution capacity of the ventilation systems. One way of checking the risk reduction is through the spatially comprehensive assessment of the air exchange rate (AER) in the indoor space. The present study was motivated by a request from the Faculty of Sciences and Technology of the University of Coimbra (FCTUC) in Portugal, whose spaces have been used under restrictive conditions derived from the recommendations on the operation of buildings during the pandemic. Two onsite experiments were carried out in an Amphitheater with only the exhaust component on, due to technical issues with the HVAC system in that period. The tests comprised measurements in ten different locations for representative monitoring of the occupied zone of the space. The estimation of the AER in the amphitheater in both tests was based on the analysis of the time evolution of the tracer gas (CO2) concentration measured by each sensor/equipment. The results showed that the analyzed space presented an adequate rate of air renewal to ensure an effective dilution of indoor pollutants, and likewise of the biological pollutant load possibly resulting from the exhalation of microorganisms by an infected occupant.

CO2 levels as an indicator of ventilation performance in me-chanical ventilated buildings

Natalia Lastovets — 2022-05-17

The current COVID-19 pandemic has attracted considerable attention from the general public and researchers. To increase this resilience toward global pandemics, we urgently need a deeper understanding of effective protection strategies. During the COVID-19 pandemic, more evidence confirms that airborne transmission plays an essential role in spreading pathogens. The ventilation systems play an important role in removing pathogens from indoor air. The current paper focuses on examining the air ventilation performance of the existing building stock before Covid 19 pandemic. The study was carried out in mechanical ventilated 440 spaces in four different building types by comparing the obtained individual CO2 concentration data with the maxi-mum concentration values given by official regulations, recommendations and guides. The data was obtained from the property maintenance program for one month at 5-15 minutes intervals. The risk spaces were studied in detail, and the risk analysis was conducted by applying the Wells-Riley approach. The research proposes recommendations for utilising air ventilation systems in different applied cases.

Learning from innovative climate concepts in schools

Stijn van der Horst — 2022-05-17

Newly designed buildings should be energy efficient as well as comfortable. To achieve both, new HVAC concepts are designed. Unfortunately, the introduction of new HVAC concepts is not always successful, leading to discomfort and even health complaints among the occupants. In this paper we describe three cases that we investigated recently: 1) A school with concrete core heating/cooling and natural air supply and mechanical exhaust. 2) A school with an all-air system with VRF units and heat pumps. 3) A monumental school building (secondary school) with pressure regulated ventilation (BaOpt) and ground heat pump. The occupants had the following complaints in the three cases: 1) complains about cold air draught and cold feet in the winter, spring and autumn and heat in the summer season. 2) complaints about air draughts, fluctuating temperatures, bad air quality and unpleasant odours. 3) Complaints concern heat in summer, cold in winter and intermediate season, and stuffy and dry air. The causes found for the indoor climate problems for the three cases: 1) The combination of natural air supply and low temperature heating. A heating pipe was installed in front of the air inlet but was unable to prevent the draught. 2) The central AHU did not have heating or cooling sections. In defrosting mode of the air heat pump, fluctuating air inlet temperatures were measured. When defrosting, the ventilation system switched to recirculation, with implications for the IAQ. Different zoning of the ventilation system and the heating and cooling system exacerbated the problems. 3) Due to the low air tightness of the building envelope, the ventilation system did not perform as intended. Only the classrooms near the air handling unit got fresh air. The ground heat pump did not function due to underground leakages, therefor the school did hardly have heating and no cooling. From these cases we learn that it is crucial to bring together technical / theoretical knowledge, practical expertise and the user perspective when working on innovative solutions. In this way we learn from practical experience which hopefully lead to improved and robust HVAC-systems.

Savings achieved in operating rooms by implementing ventilation air flow regulation strategies, in several climatic zones of spain

F.J. Rey-Martínez — 2022-05-17

Hospitals are critical environments, which are characterized by the health and safety of patients and staff. Hospitals have uninterrupted operation of the facilities, thus requiring air conditioning and ventilation, in order to reduce physical, chemical and biological contaminants, such as the current Covid-19. Hospitals have different indoor environments due to the different comfort and health needs of their occupants. These are defined according to the hospital's own standards for IAQ for each specialized area. Currently, most hospital ventilation studies revolve around specialized areas such as operating rooms and infectious and immunosuppressed wards, etc. However, the best practices for achieving an adequate indoor environment are not yet unanimously recognized. This study focuses on the reduction of energy, economic and environmental costs, all of them obtained when a ventilation flow strategy, ventilation controlled by demand, is installed in the operating rooms in a Hospital in Spain. The ventilation air flow rates required in operating rooms, according to Spanish standard UNE 100713, are very high when they are in operation (with a minimum flow rate of 2400 m3/h or 20 ren/h). However, the regulations also allow reducing the air flow during periods of inactivity of the operating room, as long as the safety, availability and asepsis are guaranteed. In this study, experimental data have been collected by monitoring the operation of the air conditioning and ventilation system, as well as the occupancy of the operating rooms of a 900-bed Spanish hospital. With all these acquired data, it has been possible to model the real operation mode of a standard operating room. Due to the implementation of this proposed model, it has been possible to study different ventilation airflow regulation strategies, with the aim of improving hospital IAQ in Spain, in three different climatic zones. The results obtained in operating rooms, through the implementation of the proposed strategy in ventilation, show that a good IAQ is achieved, reaching energy savings in heating, cooling and electricity consumption, between 20% to 70%. Therefore, the economic costs are drastically reduced, amortizing the investment required for the regulation and control system of the HVAC system in less than a year.

Resilient Cooling in Buildings – A Review of definitions and evaluation methodologies

Shady Attia — 2022-05-17

The concept 'Resilience' has gained wide international attention by experts and is now seen as the future target for the design of buildings. However, before using the word 'resilience’, we must understand the semantics of the word. Resilience is not 'resistance' and is not 'robustness and is not 'sustainability', it is a more complex definition. As part of the International Energy Agency Annex 80 on resilient cooling in buildings, this paper focuses on formulating a definition for resilient cooling. Resilient cooling is used to denoting low energy and low carbon cooling solutions that strengthen the ability of individuals, and our community as a whole to withstand, and also prevent, the thermal and other impacts of changes in global and local climates; particularly concerning increasing ambient temperatures and the increasing frequency and severity of heatwaves. This paper focuses on the review of most of the existing resilient cooling definitions and the various approaches towards possible resiliency evaluation methodologies. It presents and discusses possible answers to the abovementioned issues to facilitate the development of a consistent resilient cooling definition and a robust evaluation methodology. The paper seeks to impact national building codes and international standards, through a clear and consistent definition and a commonly agreed evaluation methodology.

Self-reported health and comfort of outpatient workers in six hospitals

AnneMarie Eijkelenboom — 2022-05-18

As hospital workers are generally less satisfied with comfort than patients and limited information was available on health and comfort in outpatient areas, a PhD study was carried out on staff in outpatient areas. The study design, main conclusions and recommendations of this PhD study are discussed. To gain a more representative view of the occupants’ perceptions, IEQ and social comfort were included. Social comfort was studied as a new construct, based on literature of privacy and crowding. A mixed methods approach was selected to justify the occupants’ reallive experience of the physical environment. First, data were collected with building inspection of six hospitals and a questionnaire responded by 556 outpatient workers. Subsequently, a representative sample of them (17) was interviewed with photo elicitation. The survey was conducted before the COVID-19 pandemic, the interviews during the COVID-19 pandemic. Data were analysed with several techniques to describe comfort and health (descriptive statistics), determine associations of work and building-related aspects with comfort and health (regression analyses), to identify IEQ and social comfort profiles (Two-Step Cluster analysis) and to identify changes in preferences due to the COVID-19 pandemic (content analysis). The different analyses strengthened associations of contextual aspects, such as room types, with health and comfort. Also, the results indicate limited overlap of social comfort and IEQ. Therefore, it is recommended to include room types and social comfort aspects in future studies. Furthermore, as the results show differences in the occupants’ preferences associated with differences in health (IEQ) and activities (social comfort) while their preferences can change in time, it is recommended to develop design strategies for an optimal fit beyond standardized solutions.

Limiting the spread of long-range airborne diseases in Long Term Care Facilities

J.M.A de Kort — 2022-04-24

In the next decades the number of aging people living with dementia and requiring intensive care will increase significantly. With this increasing number, due to their frailty, new challenges arise, including a higher risk of infection due to long-range aerosols that contain pathogens. This study sought an answer to the question of how the risk of (potentially lethal) infection through such transmissions can be limited, and the quality of life improved. The study looked at improving the basic health of residents and at additional measures to reduce the risk of infection in long term care facilities (LTCF). The focus group within this research was demented aging people living in small scale care facilities with 24-hour guidance. By means of an iterative design process and the In2health method, a building design was realised in which additional measures concerning ventilation and air-cleaning were applied. These measures were tested against different future scenarios concerning the spread of viruses in LTCFs. Based on various calculations using the Wells-Riley method, it was concluded that the building design can reduce the risk of infection without affecting the quality of life. This, however, does take a lot of additional devices, services and measures per building. Further research should include measurements in long term care facilities to ensure the specific effectiveness of the measures. Furthermore, specific air quality regulations should be designed for long term care facilities, including calculations based on risk for infection.

Technology concepts for rapid renovation using adaptable lightweight façade systems

Daniel Adamovský — 2022-04-24

H2020 project PLURAL (Plug-and-Use Renovation with Adaptable Lightweight Systems) proposes prefabricated, modular and adaptable lightweight façade systems for rapid renovation of existing buildings providing high-performance, cost-effective and fast renovation solutions. This paper presents the early stage technology concepts of three different core systems representing Plug-and-Use (PnU) building envelope kits. The PnU kits couple the lightweight façade module concept with ecological coating materials, integrated energy systems such as photovoltaics, heating, cooling, and ventilation. The paper describes in detail technical solutions of three innovative core systems and presents real and virtual demonstration buildings. Also shows calculated energy performance for real buildings when one of PnU kits is applied for renovation.

Numerical Analysis of Age of Air and Suspended Particle Distribution in Ventilated Operating Room

Riou Yamada — 2022-04-24

This paper evaluates the indoor-air contamination caused by surgical smoke in the operating room and verifies the improvement caused by installing hanging walls suspended from the ceiling. A Computational Fluid Dynamics (CFD) analysis was performed to analyze the gas contaminant in the operating room with and without the installation of hanging walls suspended from the ceiling. The analysis showed how the downward air-conditioned flow blown from the ceiling surface and the upward flow caused by the hot surgical smoke interacted to form a complex flow field. Due to the close proximity of the source of smoke to the breathing zone, there
was a steep gradient in the concentration of particles near the operating field.

Carbon capture from indoor air as an alternative ventilation technique

Jean Paul Harrouz — 2022-04-24

A polluted indoor space is a serious problem for the occupants especially for office workers who require high attentiveness levels. Indoor pollutants, especially carbon dioxide (CO2), reduce the workers performance by increasing sickness risk and impairing cognitive abilities needed to make informed decisions. Typically, indoor air quality is improved by diluting indoor contaminants with fresh outdoor air. However, the outdoor air should be dehumidified and cooled before it is entrained into the office, especially in hot and humid climates. Nonetheless, this solution is energy intensive since conventional systems use vapor compression-based air-conditioning. This increases the building electricity consumption as well as its carbon footprint. To mitigate the danger of global warming emerging from the increased carbon emissions, sustainable ventilation techniques must be conceived. The use of the recirculated indoor air, characterized by lower temperature and humidity levels than the outdoor air, could reduce the ventilation load. However, the indoor air suffers from increased CO2 levels generated by the occupant. To overcome this problem, adsorption-based CO2 removal from the room air can be a good solution. Recently, this system has become more promising due to the emerging of new generation of solid adsorbents, the metal-organic frameworks (MOF). They can be produced to exhibit high capacity and affinity towards carbon dioxide and can be regenerated at low temperature energy such as solar and waste energy. CO2 capture by adsorption reduces the ventilation load by reducing the outdoor air requirement to modest levels needed to maintain healthy levels of VOCs and O2. A sustainable cooling system is developed using MOF-packed adsorption beds for CO2 capture to treat the indoor air and resupply it to the space. A numerical model simulating the heat and mass transfer in the adsorbent bed is developed and used to size the adsorption system for a case study of a typical office in the hot and humid climate of Beirut, Lebanon. The proposed ventilation system reduced the outdoor air requirements and ventilation load by 72.6 % and 36 %, respectively during the peak load month of August.

A review of thermal comfort modeling of elderly people

Minzhou Chen — 2022-05-05

With the global warming and aging of society, the analysis of thermal comfort of elderly people is becoming more important. One example is during heat wave period, the elderly are exposed to a hot environment for a long time, the probability of health problems (cardiovascular disease, mental confusion, etc.) may increase, and even death may occur. The thermal comfort model can predict the human thermal response and evaluate the ambient thermal environment. Therefore, thermal comfort models have a significant effect to improve the thermal sensation of occupants in a built environment. But models being established with adults’ data may not be accurate enough in predicting the thermal response of the elderly. This paper reviews the existing thermal comfort models for the elderly and summarizes different types of thermal comfort models, including the thermoregulatory model, the thermal comfort model, and the machine learning model. The differences and the applicable conditions of models are summarized. This paper provides evidence from literature for the difference in thermal response between the elderly and young people, and also provides a reference for the establishment of a thermal comfort model for the elderly in the future.

Understanding effects of ventilation on airborne microorganisms in build environments

So Fujiyoshi — 2022-05-06

The indoor air quality is associated with occupant productivity and a host of chronic health problems, including allergies, asthma, and depression. Ventilation is one of the solutions to improve air quality. Qualitative and quantitative characteristics of different ventilation systems, i.e., natural, mechanical and hybrid systems, might have an influence on several aspects of indoor environmental quality. As potential indoor pollutants, there are a great variety of components such as chemical substances and microbes, but our knowledge about the relationship between ventilation and microbes inhabiting the built environment is limited, including SARS-CoV-2. This limitation may partly be caused by the facts that i) methods, especially sampling of low concentration microbes from the air, for investigating indoor microbial community have not yet been established, ii) microbes in the built environment are greatly influenced by the surrounding environment and human lifestyle and behavior, and iii) different ventilation methods also affect the microbial community. The purpose of this study is to summarize the importance of airborne microorganisms in the built environment, focus on very different built environments with natural and mechanical ventilation, respectively, from a microbiological view, and attempt to find the characteristics of microbial communities in each environment. As a result, the possibilities and limitations of the current ventilation systems are highlighted, as well as tools and methods useful for analyzing airborne microbial communities, with preliminary results from our new-generation sequencer.

Indoor Air Quality Evaluation of guests’ rooms in hotel building

Marek Borowski — 2022-05-05

The advancement of civilizations and the development of society increase the amount of time that a person spends indoors. Currently, people spend up to 80-90% of their lives in buildings, which is why it is so important to ensure proper thermal conditions and high indoor air quality. Air exchange in the rooms is a necessary process for comfort due to the concentration of oxygen and carbon dioxide and the removal of heat and pollutants. The presence of users is a source of pollution in the form of carbon dioxide and heat emitted. An insufficient supply of fresh air may lead to the increase of dioxide concentration to levels that disturb the proper functioning of the body. Installations in hotel buildings must be designed and operated in such a way as to ensure high comfort and meet the high requirements of customers in terms of the internal environment, safety, and reliability of the system. The study aimed to analyse air quality and thermal comfort in hotel rooms. The research was conducted in a historic hotel located in southern Poland. The building consists of four above-ground stories and the basement. The building has 50 double rooms, a conference room for 40 people, and a restaurant with 90 seats for guests. Temperature, humidity, and carbon dioxide concentrations were measured in the rooms. The analysis was conducted based on data from the daily and weekly cycles and included the influence of external factors. Measurements in hotel rooms were carried out continuously with a sampling period of 1 minute, both in the presence and absence of guests. The paper presents an analysis of the variability of air parameters in a daily and weekly cycle and the influence of external factors on the measured values. On this basis, it will be possible to assess the air quality inside hotel rooms and propose solutions to improve internal conditions.

Kitchen ventilation system design and its effect on restaurant IAQ

Kamal Moumen — 2022-05-07

It is well established that exposure to high level of Particulate Matter (PM), especially smaller particles below 2,5 micron (PM2.5) has a negative impact on health. We also know that cooking is the major contributor to PM levels in dwellings (Jacobs et al, 2016). A recent field study in restaurants (Kulve et al, 2020) also showed elevated levels of PM exposure, exceeding those recommended by World Health Organization (WHO). It is obvious that ventilation systems do not meet the objective of providing good Indoor Air Quality (IAQ) in restaurants with high level of PM exposure. This presentation addresses ventilation system design and its effect on PM level in the commercial kitchen setting. The study was conducted in a ventilation laboratory setting using a charbroiler and gas fryers
cooking hamburgers, and French fries. Two types of ventilation hoods were tested as well as two air distribution strategies: mixing and displacement ventilation. The study replicated elevated levels of PM2.5 concentrations with inadequate ventilation design and demonstrated that properly designed ventilation system can protect kitchen personnel from high PM exposure. The study also emphasized the importance of IAQ sensors in restaurants to guarantee adequate performance of ventilation systems.

Study on Ventilation Efficiency and Infection Probability in the Outbreak at Restaurant

Nobuhide Ashiki — 2022-05-08

With the spread of the coronavirus infection, ventilation efficiency, new design styles, air conditioning and ventilation operation methods, existing building improvement plans, and other building infection risk reduction methods need to be systematized. This study used computational fluid dynamics (CFD) to recreate a series of cases in which nine out of 89 people were infected at a restaurant in Guangzhou, China. Although the importance of ventilation has been reaffirmed, when making a general ventilation plan, ignore the pollutant concentration distribution in the room and calculate the required ventilation volume assuming complete ventilation in the room. In a real space, the generation of pollution sources are local, and the airflow properties in the room, arrival/distribution of fresh air, and discharge properties of the generated pollutants differ greatly; thus, non-uniform concentration fields, ventilation efficiency distributions, and infection probability distributions also occur. A series of cases infected at a restaurant in Guangzhou was evaluated by Scale for Ventilation Efficiency 3,4 (SVE3, SVE4). SVE3 is corresponding to the traveling time of air from the supply outlet to each point. SVE4 indicates the contribution ratio of a supply opening to air at a point in a room. In addition, the Wells–Riley model (WRM) is a typical model for quantitatively evaluating the risk of airborne infections, and cases of numerical analysis have been reported in various countries worldwide.
However, WRM assumes that the distribution of indoor droplets is uniform and the droplet concentration is stable, and that floating fine particles with a nonuniform concentration field from the active state of the virus, gravity sedimentation, and a non-uniformly distributed pollution source. A diffusion phenomenon is possible, but there is a problem that has not been addressed. Previous studies have excluded diffusion phenomena from their evaluation because gravity sedimentation is significantly less than inactivation, and the cause of local cluster formation is inadequate.This study aims to establish a predictive flow for infection control using
CFD.

Assessment of environmental perception of inhabitants of the municipality of Américo Brasiliense on thermal comfort and climate change

João Forte — 2022-05-08

This research aimed to analyse the environmental perception of climate and the relationship with thermal comfort of adults who have lived in the city of Américo Brasiliense, Brazil. Thus, a questionnaire was created in order to understand the comfort that the participants felt in relation to the environment around them, in addition to the perception of this theme on a global and local scale and how they fit into this context. In this way, it was possible to compare responses and infer the participants' knowledge regarding the concepts of environment and climate comfort in the city. Through the analysis of these aspects in the questionnaire, it was noted that the perception of individuals regarding issues related to the environment, especially in the context of Climate change and the perception of the impact on their comfort and the environment around them, may vary due to the performance of the local government and the involvement of the people in a neighbourhood. It is noticed that respondents related their behaviour and actions in the environment in a different way, when analysed on a global and municipal scale. Therefore, it can be concluded that the sample population can understand the relationship between the environment, thermal comfort and the effect of urban afforestation on local comfort, in addition to the fact that public policies, encouraged by the government, can influence the perception population about the environment in which they live. Another point noticed was the fact that there is an impasse when people think about their roles in relation to the environment and climate change at a local and global level. Part of the interviewees believe that their daily actions in the local environment do not impact the environment when placed on a global scale, which, would be a relevant point that needs to be worked on more deeply.

Impact of Ventilation Air Supply Type on Indoor/Outdoor PM

Kevin Verniers — 2022-05-08

Indoor comfort has been given significant attention to satisfy the occupants’ needs, yet the Covid-19 pandemic accelerated awareness for creating also a healthy atmosphere. Besides infectious aerosols, Particulate Matter (PM) and Volatile Organic Compounds (VOCs) can induce health issues on the short and long term. Commercial ventilation systems are increasingly based on providing a good indoor comfort by monitoring CO2, RH, and/or VOCs while targeting a low as possible energy consumption. Indoor PM is determined by various indoor and outdoor sources ranging from cooking and household activities to outdoor PM transported or infiltrating into the building. Consequently, the indoor PM level varies and potentially affects human health. This research contains in-situ measurements with Renson Senses quantifying indoor and outdoor PM in and near one single dwelling for examining the impact of commercial ventilation systems (Mechanical Extract Ventilation (MEV) and Mechanical Ventilation with Heat Recovery (MVHR)) on indoor PM1, 2.5, 4 and 10. The measurements encompassed four system configurations either without filter (natural or mechanical supply) or mechanical supply equipped with ISO Coarse >90% or ISO ePM1 50% filters to assess the filter efficiency in practice. The extraction flow rate was kept constant and identical to avoid the impact of different air exchange rates on indoor PM. Each configuration was active during two weeks resulting in a two months period (May-June, 2021) during which occupancy and indoor polluting activities were rare, allowing to assess the ventilation and filter impact on indoor PM. The analysis revealed that indoor PM levels are about half the outdoor PM levels without filtering on the air supply, when there was no occupation or activities. Using an ISO Coarse >90% filter showed no clear effect with a similar performance as an MEV system. Next to this, a MVHR system equipped with an ISO ePM1 50% filter significantly impacts the transport of outdoor PM to indoors, with an efficiency, expressed as the Indoor/Outdoor ratio, of about half the laboratory efficiency. Supposing that PM originates 50/50 from indoors and outdoors, the actual fine filter efficiency influencing indoor PM is about 15-25% of the measured lab efficiency.

Assessment of the infection risk distribution of COVID-19 and ventilation energy consumptions in indoor environments

Marco Marigo — 2022-05-08

The energy use for ventilating buildings involves high economic and primary energy consumption costs. Nevertheless, ventilation is essential, especially in public places, to ensure acceptable Indoor Air Quality (IAQ) levels and reduce the risk of airborne virus infection. The latter aspect has recently increased because of the ongoing COVID-19 pandemic. In this paper, a model that couples a zonal ventilation model with infection risk calculation is integrated with an energy consumption model to analyse the energy consumption and infection risk from COVID-19 at different ventilation flow rates for three case studies: an office room, a high school and a university classroom. The main results show that the increase in ventilation flow rate involves reducing risk, but it increases energy consumption. Moreover, the mask-wearing resulted in having a relevant effect, whereas the effect of the relative position difference inside the room was not detected with the proposed discretisation.

Using ASHRAE Standard 55 Adaptive Comfort Method for Practical Applications

Peter Simmonds — 2022-05-08

The question of comfort under a natural conditioning scheme when governed by ASHRAE Standard 55, which describes the use of the adaptive comfort standard, including the elevated speed option, and compares this model to other comfort indices. The analysis requires a combined dynamic heat transfer and bulk airflow analysis method that delivers simultaneous output of expected indoor temperatures and indoor ventilation rates.
To determine if the space is compliant, the designer must demonstrate that the indoor operative temperature conditions stay within the prescribed range during occupied hours. Typically, dynamic thermal simulation software capable of modelling natural ventilation schemes is used to simulate the cooling effects of the natural ventilation airflows and the radiant impacts of the room surface temperatures.
This paper shows a Standard 55 compliance analysis and how the results are presented in an understandable manner.

Improving the indoor / outdoor ratio of (ultra)fine particles in a school

Froukje van Dijken — 2022-05-08

Buildings located close to busy roads, industry or stock farms, are of risk of increased indoor particle concentrations, which negatively impacts the health of the building occupants. In order to reduce the exposure of the building occupants, it is important to take measures to reduce the concentration of particulate matter indoors. Solutions for existing buildings include application of improved filters in the air handling units, using local air cleaners and limit the use of operable windows. However, little is known about the overall effectiveness of these measures in existing buildings that are in use. The aim of our study was to quantify the effectiveness of particle reducing measures in buildings at high traffic locations. We performed a field study in a school in a neighbourhood between highways. In this school the effect of improved filters in the air handling unit, a HEPA filter at room level as well as the combination of both interventions on the particle concentrations indoors were studied. We quantified the effect of the interventions by momentary measurements of PM2,5 and ultrafine particles (≥4 nm). Moreover, PM2.5 was continuously measured outdoors and indoors. The ePM1 85% filters in the AHU seemed effective on the reduction of (ultrafine) particles (nearly 75% reduction of PM2,5). The use of a HEPA filter was not effective in our test situation.

Experiment on Indoor Pollutants Reduction from Duct System Applied with TiO2 Photocatalyst

Seong Eun Kim — 2022-05-08

This study analyzed the indoor pollutants (toluene, formaldehyde) reduction performance of a ventilation duct system using a titanium dioxide photocatalyst(TiO2) to improve indoor air quality. The ventilation duct system has a loop-type closed circuit structure with a diameter of 100 mm and a length of 6.6 m that includes a reaction section to which UV lamps and photocatalysts are applied. The length of the reaction section was 0.6 m, and 0.18 m2 of the photocatalyst was applied. Toluene and formaldehyde were each injected at a concentration of 1 ppm, and the average airflow velocity inside the duct was set to 1 m/s and the experiment was performed. As a result of the experiment, toluene showed 0 ppm in 14 minutes and formaldehyde showed 0 ppm in 12 minutes after the photochemical reaction had started. Therefore, it was confirmed that the indoor pollutant concentration could be reduced when the TiO2 photocatalyst is applied to the ventilation duct system.

Integrating health & comfort into building design

Bas Hasselaar — 2022-05-08

In the current real estate market, sustainability and wellbeing are no longer seen as something extra, but rather as a point of departure. However, there is a plethora of different sustainability labels focussing on the built environment. This can lead to confusion for architects, developers, commissioners, contractors, and users in general: what label should I use, what label is best suited for my project, why use this or that label, what is the difference? This paper discusses the five best known labels in The Netherlands: BREEAM, WELL, GPR, Active House and Passive house. It explores how they are used, how they differ, and how using them at the design stage can help create more sustainable buildings.

Comfort evaluation of a dynamic protective airflow system using human test subjects

Kim Hagström — 2022-05-08

Amount of sick leave days among nurses is in relatively high level compared to many other occupations. One of the risk factors for nurses at work are respiratory infections.
According to recent studies, there is a high risk for nurses to be exposed to microbes exhaled by patients especially, while they are conducting their work close to patient.
Current ventilation solutions that are used in patient environments are not designed to address this challenge. At best, they are able to dilute the microbial concentrations in the room, but they are not able to affect the nurse’s exposure to patients’ outbreath close to patients. These may lead to substantially higher exposure levels compared to room air conditions.
To reduce HCW’s and especially nurses’ exposure and infection risk, a new dynamic protective flow ventilation approach has been developed for patient environments (isolation rooms, intensive care and standard patient rooms). In previous studies, the efficiency of protective flow ventilation as well as thermal comfort has been verified by using breathing thermal manikin and tracer gas experiments.
In this laboratory study done in a simulated patient room, the thermal comfort provided by the protective ventilation solution is studied with human subject experiments. The participants are exposed to indoor environment, both in stable conditions and in a dynamic situation in which patient / nurse interaction is simulated. The thermal comfort is evaluated primarily by questionnaires, which the subjects will complete in different stages of the experiment. Physical measurements are conducted in parallel.
The presentation will outline previous development stages and will especially focus on presenting the results of human subject experiment.

Natural indoor climate in St. Charles Borromeo chapel in Telc

Ondřej Hnilica — 2022-05-12

The memorial chapel of St. Charles Borromeo from 1664 in town Telc includes the fresco-secco mural painting in the dome. The natural indoor climate with a height of 12.1 m is analysed for the preventive conservation of the original mural painting. This hygrothermal analysis in the period 2018 - 2021 shows the average indoor air temperature of 10.2 Â°C and indoor air relative humidity of 75.1 % r.h. This natural indoor climate shows the frequency of Frost risk in 10.72 % days per year, Microbiology risk in 4.85 % days per year, and Dryness effect in 0.01 % days per year. The vertical stratification of indoor climate is obtained for air temperature up to 5.2 K and -24.1 % r.h. for relative humidity. This natural indoor climate in the St. Charles Borromeo chapel is significantly dependent on outdoor weather with time-lag 2 hours.

Evaluation of students' perceptions and thermal comfort in London

Junpeng Lyu — 2022-05-13

A thermal comfort field study was conducted in a lecture room involving 44 participants to investigate occupant perception and thermal comfort, as well as compare it with other 37 lecturer theatres. All buildings are located in a temperature climate region of the UK. Additionally, objective measurements including dry-bulb air temperature, relative humidity, and subjective responses concerning thermal sensation, thermal preference, and air velocity were additionally collected. Through Hobo measurement and a questionnaire survey in the site lecture room, we present the association linking thermal comfort and seating location. A similar tendency can be found through the comparison between the AMV values of all lecture theatres and PMV ones, which could be explained by the fact that occupants have a very limited physical adaption to their surroundings in the lecture room. Furthermore, the level of thermal comfort of the occupant sitting in the back (higher seats) is lower than that of the occupant sitting in the front row (lower seats).Through a statistical contrast of the level of thermal comfort among individuals seated at the back and front in all lecture theatres, it was illustrated that the occupants at the back were warmer compared to those at the front, and the decreased level of thermal comfort of occupants could be found in many lecture theatres. Overall, in the relationship between thermal comfort and seat position, thermal comfort has a close association with the front seat, which comprises greater comfort in contrast to the rear seat.

Personal comfort model for automatic control of personal comfort systems

Dragos-Ioan Bogatu — 2022-05-13

Personal comfort models could be used for the development of automatic controls for personal environmental comfort systems (PECS). These models often use indoor environment and physiological indicators as attributes for estimating the subjective response of occupants. Traditional indoor thermal environment research and standardization recommend 7-point scales for thermal comfort or thermal sensation estimation. However, many studies apply transformations to the response, thus oversimplifying the scales and generating controversy. The aim of this study is to determine the relevance of different indicators for the development of personal comfort models while investigating the implications and resulting model accuracy when using different thermal sensation scale discretization. Two simple machine learning algorithms, namely logistic regression and Naïve Bayes, were used in a multi-class setting to predict the overall thermal sensation of individual subjects when occupying a heated or cooled chair in steady state conditions. Multiple models were generated depending on the variables included in the feature set. Additionally, two response vectors were generated based on the thermal sensation vote, a three class and a seven class one, the latter being generated by further discretizing the hot and cold spectrum of thermal sensation. Both models performed better than a random guess at identifying thermal sensation classes and reached accuracies of up to 72% when predicting the overall thermal sensation of people using PECS. Including information of the PECS operation in the model, i.e. seat temperature, increased the prediction accuracy by up to 5%. The overall accuracy was higher when using three classes for the thermal response, as implementing seven classes led to a decrease of up to 21 percentage points. Nevertheless, the latter provided a finer adjustment without affecting the model’s ability to distinguish between the cold and hot spectrum, which may be an advantage for personal comfort systems that condition the microenvironment of the occupant.

Baby beds’ sleep micro-environment in day care centres

Wim Zeiler — 2022-05-13

Concerns are emerging about potential adverse effects of indoor air pollutants on children's health and development, since young babies are exceptionally more sensitive to chemical exposures than children and adults. Day care centres (DCCs) are the most important place besides their home as babies spend up to 11 hours inside the DCCs, of which half of the time in their beds during the first six months. Especially during the first year their developing lungs are highly sensitive to pollutions. Ventilation within the baby bed themselves is rarely studied however insufficient IAQ conditions at DCCs were unanimously confirmed in t previous studies. Therefore, the main aim of this paper is to state the importance of improving the indoor air quality at day-care centres, especially in sleep micro-environment of the baby beds. The paper presents an overview to emphasize the importance for the health of babies.

Analysis of occupant satisfaction with IEQ in residential buildings

Quinten Carton — 2022-05-13

Multiple studies have shown that occupants’ satisfaction with the indoor environmental quality (IEQ) is not always as high as expected from standards. Furthermore, consensus on methods for quantification of occupant satisfaction is still missing. Therefore, satisfaction assessment and further investigations into the relationships between occupant satisfaction and measured IEQ are needed.
This paper investigated the relationships between satisfaction ratings and IEQ parameters in mechanically ventilated residential buildings. This study used data from Belgian dwellings with a demand-controlled extraction system that was accompanied by a mobile phone application, enabling the users to adapt the ventilation system settings.
In this study, we evaluated the residents’ satisfaction with the IEQ in their main living room. The satisfaction assessment approach consisted of (1) a retrospective survey and (2) the implementation of satisfaction rating scales into the mobile application of the ventilation system, allowing the residents to evaluate their satisfaction with the thermal environment or IAQ. The satisfaction rating option was active for two weeks during winter conditions. Simultaneously, IEQ-related parameters (i.e., air temperature, relative humidity and CO2 concentration), and residents’ interactions with their ventilation system (e.g., changing airflow rates or CO2-thresholds) were monitored. We investigated the relationships between the satisfaction ratings and the IEQ- and interaction-related parameters through mixed-effect model analysis.
130 residents filled in the retrospective survey, and over 800 satisfaction ratings were submitted by approximately 60 different dwellings. Results of the retrospective survey and satisfaction ratings show that the participating residents were in general satisfied with the IEQ in their living room. The mixed-model analysis shows that the indoor temperature was the main parameter affecting residents’ satisfaction with both IAQ and thermal environment. Furthermore, the results illustrate that the satisfaction ratings are mostly related to the specific resident, making it challenging to determine an aggregated model without personal and contextual information

Effects of airing behaviours on bedroom air pollutants during sleep

Chenxi Liao — 2022-05-13

Higher ventilation rates were verified to have a positive impact on indoor air quality and therefore benefit sleep quality. However, how does ventilation influence bedroom air quality if the outdoor air quality is poor? Whilst ventilation helps to reduce indoor pollution it inadvertently brings outdoor pollution indoors, such as NO2, which is from vehicular emission. In this study, we collected the info of window and door status during sleep and measured carbon dioxide (CO2), nitrogen dioxide (NO2), volatile organic compounds (VOCs) and particulate matter (PM2.5 and PM10) among 38 bedrooms while occupants were sleeping during nights. Meanwhile, the air change rate (ACR) was calculated. The experiments were conducted in the heating season (September to December 2020) in the capital region of Denmark. The median values were 981.8 ppm (mean CO2 level during sleep), 0.6 h-1 (ACR), 3.4 ÂµgÂ·mâˆ’3 (NO2), 166.2 ÂµgÂ·mâˆ’3 (VOCs), 11.0 ÂµgÂ·m-3 (PM10) and 2.8 ÂµgÂ·m-3 (PM2.5). CO2 levels were positively correlated with VOCs levels, whereas negatively correlated with NO2 levels in bedrooms. ACR was also negatively correlated with VOCs. CO2 levels were significantly higher whereas NO2 levels were lower with both window and door closed compared to them with either window or door open. With higher ventilation rates, while occupants would be less exposed to indoor pollution of VOCs, they would be increasingly exposed to NO2. Future studies of bedroom ventilation and sleep quality should consider outdoor air quality.

Nearly Zero Energy Buildings as a Standard of 21st Century – Velux RenovActive

Anna Predajnianska — 2022-05-14

Most residential buildings in Slovakia, built in the 20th century, do not meet current requirements for energy efficiency. Therefore, nationwide remedial measures have been taken to improve the energy efficiency of these buildings and reduce their energy consumption. That is why Velux has created a RenovActive project to make this possible. The goal of renovations is to ensure today´s strict conditions for the energy consumption of buildings and thus achieve nearly zero energy buildings. In this article, we focused on the reconstruction of an old family house, which was built in 1960. The family house has been uninhabited for decades and was in a desolated state. We created three different options of reconstruction for the family house, each with different materials and technical equipment. Part of the article is also a comparison of the need for energy in each variant of reconstruction. We also processed a comparison of investment costs required for individual variants. The article also describes the current state of the family house. Currently, the house is inhabited by a young family and measurements of the basic quantities of internal well-being take place in the house. The aim of this project was to turn an old family house into a nearly zero energy building and ensure the required internal well-being at the level of 21st century.

Thermal environment in simulated office rooms generated by active ceiling diffuser with radiant panels

Panu Mustakallio — 2022-05-15

Ventilation airflow rates are typically controlled based on occupancy, air quality and heat load levels in office rooms with variable air volume (VAV) system. Additional water-based cooling is often the most energy efficient to use when cooling by cold ventilation air for occupancy and indoor air quality does not cover heat gains. This can be done by air-water system, by combining ceiling diffusers with radiant panels. The target of operation of these room units is to maintain a good thermal environment for occupants and stable supply air distribution in varying occupancy/heat load levels. This can be challenging especially with non-uniform heat loads. In the earlier study, it was concluded that active ceiling diffusers were able to generate a more uniform thermal environment than static ceiling diffusers. The thrown pattern is not constant with the static diffuser, but with the active diffuser, it is more uniform due to constant supply air velocity. This study was continued by analysing differences between the design of all-air and air-water systems with active diffusers and investigating higher heat load situations enabled by air-water system. The novelty of this research is to confirm the usability of the air-water system with active ceiling diffusers in an office environment. Office room situations were measured earlier in a full-scale test room (27 m2) with partial occupancy for studying differences between air distribution. Now that was done with CFD simulations. The same 3-person office room case (46 W/m2floor) without and with radiant panels was modelled first to validate CFD-simulation in all-air system case (4.3 l/s,m2floor), and then to simulate the performance of the design with air-water system (1.8 l/s,m2floor). Then 10-person meeting room case with air-water system (4.3 l/s,m2floor) was simulated with a higher, design heat load level (81 W/m2floor). The thermal environment in the same office room cases measured in the full-scale test and modelled in the CFD simulation was near to each other. Supply air diffuser was modelled in CFD simulation with detailed geometry and other boundary conditions were similar to in full-scale test situation. RANS simulation method was used with SST turbulence model and with a fine computational grid. CFD simulations with higher heat load levels brought new findings for the air distribution with radiant panels. The increase of heat loads also increased room air velocities, but still local thermal environment remained at a good level. This confirms the usability of air-water system with active ceiling diffusers in variable conditions.

Droplet Concentration Produced during Expiratory Activities and Evaluation of Relative Infection Risk

Arisu Furusawa — 2022-05-15

The outbreaks caused by COVID-19 have prompted researchers to quantitatively assess the risk of infection. Since airborne transmission is caused by inhalation of droplet from infected persons, it is important to understand the droplet concentration and size distribution of aerosols. In this study, we examined the size distribution of droplets produced by various expiratory activities, compared the results with previous studies, and tested the consistency of a simple measurement method. We realized the measurement by conducting the experiment in a clean room with low background concentration, using an optical particle counter and a device that can constantly ventilate the generated droplets. Quanta emission rate is a method of evaluation the risk of infection. Among the variables in the equation to determine it, we measure droplet concentration and inhalation rate, which we can measure, and from the product we get the relative risk of infection for each of the various expiratory activities. In the expiratory activities, in addition to the same cases as in the previous study, we conducted conversations and vocalizations while wearing a mask. In this study, we mainly analysed particles smaller than 1μm, based on the theory that viruses are highly proliferative and pose a high risk of infection. The concentration of droplets generated by exhalation activity is dominated by particles smaller than 1 μm in number concentration, but only a small percentage in mass concentration. In addition, the risk of infection increased in proportion to the volume of voice, and loud vocalizations showed a prominent risk of infection. Furthermore, it was confirmed that the risk of infection was reduced by wearing a mask, and the degree of reduction depended on the method of wearing the mask.

Health and energy assessment of a demand controlled mechanical extraction ventilation system

Janneke Ghijsels — 2022-05-15

Today, the assessment of residential demand controlled ventilation systems only considers the perceived indoor air quality in terms of comfort, with CO2 and humidity as the main parameters to investigate. However, the ventilation system and its controls also have an impact on the health aspect of Indoor Air Quality (IAQ) due to the higher exposure to unhealthy pollutants (Volatile Organic Compounds (VOCs), fine dust particles, e.g. PM2.5). In this paper, two demand controlled mechanical extraction ventilation systems (DCV) and a continuous mechanical extraction ventilation system (MEV) of a typical Belgian apartment are modelled using Modelica. This allows to simulate the combined effect and interaction of temperature, airflow and IAQ. The model includes sources of CO2 humidity, VOCs and PM2.5 to the indoor air. The combined approach using Modelica allows to do an in-depth analysis of the indoor air quality. A two-stage assessment method is performed, resulting in an overall performance (in terms of IAQ and energy use) of a DCV system in relation to the performance of the MEV reference system.

Thermal comfort perception and indoor climate

Arjen Meijer — 2022-05-15

The average energy consumption for heating of dwellings in the Netherlands has been decreasing over the last decades as a result of increasing thermal performance of new and renovated dwellings. However, this decrease is found to be lower than energy performance models predicted. One of the possible reasons is the behaviour of the residents, which is partially determined by the thermal comfort preferences of these residents. In this paper, the relationship between thermal comfort perception, indoor climate and energy consumption is investigated using high-resolution measurement data in 93 dwellings in the Netherlands. In the OPSCHALER project, data about thermal comfort perception, indoor climate and operational energy consumption were collected in 93 dwellings in the Netherlands during periods ranging from two to twelve months over a period of two years. Comfort perception was registered using the Comfort App, an application where users record their comfort data. Indoor climate data were collected per five minutes using sensors for temperature, relative humidity and CO2 concentration in the living room, kitchen and bedrooms of the dwellings. The Comfort App asked the residents for the room they are in, their comfort perception, their activities during the last half hour and the amount of clothing they wear. Significant relationships were found between thermal sensation and thermal preference, clothing level, metabolic activity level, activities related to thermal comfort taken in the last half hour, and indoor air temperature. These data can be used to compare the comfort level registered by the residents with the comfort level predicted by the PMV model, and link this to the indoor climate and the energy consumption for heating. This information can help to understand the relations between user preferences, indoor climate and energy consumption for heating.

New developments in odour testing

Simone Brandt — 2022-05-15

Healthy and energy efficient buildings must be free from disturbing odours. Odour emissions from building materials can be measured with the well-known and accepted standard ISO 16000-28 “Indoor air – Part 28: Determination of odour emissions from building products using test chambers”. For commonly used emission test chambers the sample air is collected in containers (bags) and presented to a group of panel members for the purpose of evaluating the odour. A standard sets requirements for the on-demand presentation in detail. These include the validation procedure for container materials, pre-treatment of bags, details on storage of filled bags and how to carry out the measurements. However, although these measures are proven in practice, incorrect measurements are still possible. Also errors can occur due to a very complex measurement procedure. So, there is a great need for research into how the odour samples are presented. The proposal planned to be presented will introduce a new development in sample provision by using an adapter which enables collection and provision of sample air without storage or transport of bags. The adapter is a sample container which is permanently positioned on the emission test chamber´s outlet and continuously filled with sample air flowing through it. The flow is briefly interrupted at the time when a sample is taken by a panel member for the test. The size of the container is sufficient to provide enough sample air for evaluation by at least one panel member via a funnel. Since sampling and presentation are technically connected, it means you can almost do away with storage or transportation and thus it can be presented almost unchanged to the panelmembers. The aim is to reduce measurement errors in the odour samples provision process and the improvement of measurement reproducibility. The paper presents the construction of the adapter as well as the results of emission and odour tests carried out so far.

Mitigating the high radon concentration in existing homes

MAREȘ Ion-Costinel — 2022-05-15

The article presents the experimental study of the efficiency of mitigating the high level of radon in existing homes using a centralized mechanical ventilation system with heat recovery. The measurements were performed both initially and after the installation of mechanical ventilation systems. The efficiency of reducing the radon level in the house was analysed, calculating the energy saved due to the heat recovery system compared to the conventional one (natural ventilation). The study concludes with a cost-benefit analysis, which shows the payback period of the investment.

Ventilation and COVID-19 transmission risks on board of Dutch governmental ships

Atze Boerstra — 2022-05-15

The Dutch government (specifically the ‘Rijksrederij’, the governmental shipping company) owns a fleet of just under 100 ships that are equipped to service the internal waterways and parts of the North Sea. Think in this context of e.g. Coast Guard ships, ships that help to fight oil accidents or ships that maintain buoys. Just after the COVID-19 pandemic had started the ‘Rijksrederij’ decided that it was necessary to investigate to what extent the fleet might pose a risk for cross contamination of this new disease on board. This was approached with a specific focus on ventilation and the airborne route. The objective was to find out whether the most important spaces on board of the ships were adequately ventilated and to evaluate how ships can be made or kept ‘COVID-resistant’ as far as the airborne route is concerned. A sample of 16 ships of different types, most of them mechanically ventilated, were surveyed. This included a general inspection, an inspection of relevant HVAC system characteristics and measurements of e.g. air supply flows. Also, ships were equipped with monitors that measured CO2 concentration (e.g. in galleys and wheelhouses) that were left on board for at least one week. As reference for the supply flow measurement outcomes we used ISO 7547 guideline values and the Germanischer Lloyd ventilation requirements. On board of 6 of the 16 ships that were investigated we found serious problems with the fresh air supply and/or measured CO2 concentrations. On the positive side, the majority of the ships had ventilation capacities in line with the two reference standards, and almost all did not use central recirculation. We also found that many of the ships had adequate options, at room level, for individual control of both fresh air supply and temperature. The results of the study will be used to further improve ‘COVID safety’ on board of the whole fleet and to ameliorate future, new ships and their HVAC systems.

Assessing Thermal Comfort in Nursing Home Using Heart Rate Measurement

Anne Sørensen — 2022-05-15

The ratio of dementia amongst the residents in nursing homes makes it practically impossible to conduct traditional questionnaire-based comfort analyses. Besides, there are uncertainties in the residents’ cognitive capabilities to respond to a questionnaire, since residents with dementia can be very sensitive to the smallest changes in their everyday life. Therefore, there is a need for alternative investigation methods when conducting comfort studies in nursing homes, such as indirect measurements or observational studies. Based on a pilot study in two Danish nursing homes, this paper demonstrates how thermal comfort can be estimated using the heat balance-based comfort equation of P.O. Fanger, using the metabolic rate of residents calculated from a simple heart rate measurement. This estimate is then compared to the Predicted Mean Vote (PMV), using standard metabolic rates to investigate how well the estimated thermal comfort fits the PMV theory. The proposed method, based on heat rate measurements, has minimum impact on the test persons and requires no cognitive activity. Furthermore, it enables a more dynamic perspective on thermal comfort. The study results indicate that the metabolism of elderly people (+75 years of age) living in nursing homes can be at a lower level than what can be counterbalanced by a lower heat loss, as it is normally assumed. The conclusion is that the proposed method is promising but needs further development and validation concerning the conversion of heart rate to metabolism and how to account for age-related physiological changes.

Safe indoor work-outs during the COVID-19 pandemic

Marije te Kulve — 2022-05-15

Many people go to the gym to work-out or take part in classes to remain in good physical health. During the COVID-19 pandemic, gyms in most countries across the world were obliged to close to prevent the virus from spreading during indoor work-outs. Indeed, the risk of aerosol virus transmission during high intensity exercise is significantly increased due to the increased aerosol production of a potentially infected person and the increased breathing volume of susceptible individuals. However, doing physical workouts is of great importance to stay healthy and enhance the immune system, especially during the pandemic, since it is known that overweight people and people with underlying diseases are at increased risk. Therefore, the objective of this project was to design a ventilation and air cleaning system that significantly reduces the risk of aerosol virus transmission in indoor sport environments. The project aims to contribute to establishing requirements for indoor sport facilities in terms of ventilation and air cleaning such that, during a next lockdown, gyms that fulfil these requirements can remain open. To achieve this objective, a literature survey was conducted to map the current knowledge on the aerosol transmission of COVID-19 and the characteristics of different types of exercise. Based on that, requirements were set for different intensity group classes to maintain the CO₂ concentration below 1200 ppm and the theoretical Wells Riley-infection risk below 5%. In addition, the importance of ventilation efficiency to dilute released contaminated aerosols was well understood in order to apply the Wells Riley-model. A lab- and field study were conducted to test if the model assumptions were met. Also, the possibility to measure aerosols in the field was investigated. Based on these outcomes, a prototype consisting of a ventilation system, air cleaning system and cooling system combined with a smart control algorithm, was designed and installed in a room for group classes. The performance of the systems was tested during exercise classes of yoga, zumba and indoor cycling (spinning).

A Multi-Domain Approach to Explanatory and Predictive Thermal Comfort Modelling in Offices

Eugene Mamulova — 2022-05-15

It is well known that physical variables, such as temperature, exert a significant influence on occupants' thermal comfort in office buildings. Despite this knowledge, models that are currently used to predict thermal comfort fail to do so accurately, resulting in a mismatch between design conditions and actual thermal comfort conditions. The assumption is that exclusive attention to physical variables is insufficient for understanding or predicting thermal comfort. Contextual, social and personal variables may also affect thermal comfort in office buildings and interact with each other. The question arises as to how a multi-domain approach can aid in explaining and predicting thermal comfort in offices. In this study, a unique dataset containing indoor environment, demographic, occupancy and personality related variables is used to construct two types of thermal comfort models. The dataset contains 524 observations, collected during summertime in two office buildings in the Netherlands. Firstly, structural equation modelling (SEM) is used to construct an explanatory model, with the aim to identify significant variables affecting thermal comfort, as well as the interactions between them. Secondly, machine learning is used to train four binary classification models to predict thermal discomfort. For the investigated cases, SEM suggests that thermal discomfort is significantly affected by (i) temperature, (ii) sound pressure level, (iii) the interaction between temperature, sound pressure level and illuminance, and (iv) the interaction between gregariousness and occupancy count. The four predictive models are subsequently trained using only the significant variables. Nevertheless, the weighted F1-score for all four models ranges between 0.55 and 0.59, indicating weak predictive performance. The results show that significant influencers are not necessarily good predictors of thermal discomfort. Future researchers are encouraged to combine explanatory and predictive modelling techniques, in order to test whether variables that are relevant to the domain are useful for prediction.

Development and performance analysis of a novel multi-zone hybrid desiccant cooling system

Shuo Liu — 2022-05-16

This study proposed a novel multi-zone applicable hybrid desiccant cooling system (MHDC) that uses condensing heat from the condenser to regenerate the solid desiccant and applied it as an outdoor air unit (OAU) with demand-controlled ventilation (DCV) in order to control the indoor humidity and air quality (IAQ). Indoor temperature and humidity control effect and system energy use were analysed compared to a conventional packaged terminal air-conditioning (PTAC) system with the heat recovery wheel (HRW) assisted OAU. The simulation result shows that in a typical high-rise building with high air tightness, The CO2 concentration in bedrooms can reach up to 3686 ppm when PTACs operate without fresh air. Without the dehumidification process, the introduction of fresh air will increase the relative humidity most of the occupancy time. The MHDC system adopted DCV can maintain IAQ except for a short period of cooking time and can handle the fresh air latent load while controlling indoor humidity without a separate regeneration heat source. However, due to the air volume limitation of OAU, the instantaneous dehumidification capacity of the MHDC system is not sufficient, resulting in a short time required to process the indoor humidity to 50 % level when the system initially started. Although the operation of the MHDC system increases the energy use of the OAU, the decrease in the latent load of zone level PTACs makes the total energy use is almost equal to the PTAC system with HRW assisted OAU, 606 kWh and 605 kWh respectively, while obtaining better indoor thermal comfort and IAQ. This study can prove that the proposed MHDC system is a possible alternative system to a conventional multi-zone air-conditioning system that can provide energy savings and thermal comfort.

The experimental study of the indoor climate with the micro-environment systems

Weixin Zhao — 2022-05-16

One of the major challenges in modern buildings is to guarantee healthy indoor air quality and excellent thermal comfort in an energy efficient manner. In this study, the performance of two micro-environment systems combined radiant panel and convective flow was designed. In one of micro-environment system of personalized ventilation and radiant panel (PVRP), two local personal air terminal devices supplied clean air directly to occupants. In the other micro-environment system, low velocity unit was installed just over the radiant panels (LVRP) and the air was supplied through those panels. The radiant panels were used to satisfy the required cooling load. The results show that that it is possible to enhance system performance with micro-environment control systems, where users are able to control their own set points for room air temperature and indoor air quality, the satisfaction on indoor climate conditions increased significantly. Furthermore, the air temperature near the workstation can be maintained at designed value with the micro-environment systems. In particularly, the vertical temperature difference did not cause thermal discomfort with the micro environment systems near the workstation.

Investigation of PECS on the basis of a virtual building controller

Katharina Boudier — 2022-05-16

Thermal comfort is one of the key parameters for occupant satisfaction and, accordingly, for the energy performance of buildings. In recent years, decentralized heating and cooling systems, so called personal environmental comfort systems (PECS) are gaining more interest for research and the market. PECS include, for example, office chairs with heating and cooling functions, thermoelectric heating and cooling walls, or even desk fans. Studies have shown that these systems can reduce the heating and cooling demand of the central HVAC systems by improving comfort.
This paper presents a newly developed adaptive building controller that uses a holistic approach in the consideration of central HVAC systems and a heated and cooled office chair, within the framework of the building simulation software Esp-r. The presented building controller can adapt the setpoint temperatures of the central heating and cooling system and also regulate the usage of the office chair’s climate function based on the thermal sensation and comfort values of a virtual thermal manikin with the help of PhySCo a transient “Physiology, Sensation and Comfort Model”. This approach can be used for an analysis of the potential of PECS. In this context, the virtual adaptive building controller with a wide deadband and adaptive setpoints between 18 to 26 °C is compared to a basic controller with a fixed and narrow setpoint range between 21 to 24 °C. The simulations were performed for temperate climate (Mannheim, Germany) that is classified as Cfb climate according to the Köppen-Geiger classification. The results showed that the newly developed adaptive controller with the PECS kept the comfort values at the same level as the basic controller. An office chair with heating/cooling function had been added to the controller and helped to keep comfort while reducing the heating demand (13 % in winter, 4 % in spring) and the cooling demand (10.3 % in spring, 2.6 % in summer).

Individual control of the frequency of intermittent personalized ventilation and its effect on cross-contamination in an office space

Elvire Katramiz — 2022-05-16

The transmission of respiratory diseases is influenced to a great extent by the ventilationin the space, mainly localized ventilation near the infection source (i.e. the infected person): One of the strategies that has been proven efficient in providing occupants with protection indoor are source control strategies. Personalized Ventilation (PV) is such strategy that delivers conditioned clean air towards the breathing zone of the user, thus providing protection while procuring acceptable levels of thermal comfort. In recent studies, PV applications varied the supplied cool clean air intermittently, mimicking natural outdoor conditions in order to enhance occupants’ thermal comfort and improve energy efficiency. Such system operation is referred to as Intermittent PV (I-PV). The highly turbulent oscillatory jet may however promote the dispersion of contaminants, especially when the user is infected. Furthermore, the individual preferences of IPV frequency also affects the contaminants’ transport. To the authors’ knowledge, such effect has not been tackled in literature. Therefore, this work investigates the impact of individually controlling the frequency of an I-PV system on cross-contamination between occupants in an office space. An infected person is considered seated in a tandem (i.e. back-to-face) position with respect to a healthy person, located at a distance of 1.5 m. This seating configuration is usually the most critical when using PV. The contamination source is the breathing of the infected person. The IPV is considered to operate at an average flowrate of 10 l/s, with a minimum of 4 l/s. The IPV users are free to control the frequency of flow delivery in a range of [0.3 Hz – 1 Hz]. A validated computational fluid dynamics (CFD) model of an office space equipped with IPV and background mixing ventilation is used to assess the cross-contamination between the occupants. A comparison between IPV frequencies is conducted to highlight the influence of IPV frequency control on contaminants dispersion and the resulting exposure level of the healthy occupant.

Simulation-Aided Development of a Compact Local Ventilation Unit with the Use of CFD Analysis

Petr Zelenský — 2022-05-16

The current emphasis on the renovation of existing buildings to meet EU energy efficiency targets brings, in addition to energy savings and related CO2 reduction, also some negative issues. One of them can be the lack of fresh air supply caused by increased air tightness of the building envelope after its insulation and renovation or change of windows. The easy solutions are decentralized units for local ventilation, which can be installed during fast renovations in selected rooms without major building modifications. Controlled ventilation then ensures the delivery of a sufficient amount of fresh air to meet current standards and, at the same time, creates a healthy and comfortable environment for occupants. The paper demonstrates the practical use of CFD simulations for the development of a new type of compact small ventilation unit for local ventilation of rooms with heat and humidity recovery. An increase in the device efficiency and a reduction in acoustic power, while maintaining its very compact dimensions, were achieved with the help of the numerical study. The paper shows the possibility of using CFD analysis during the development of new HVAC appliances. It describes the preparation of the numerical model of the device, presents the simulation approach, including the calculation settings, and discusses device optimization based on variant numerical analyses in ANSYS Fluent. The initial prototype design of the unit was optimized following the findings from the numerical analysis, and it was verified by CFD study that the proposed adjustments were appropriate and that the expected results were achieved. In a separate CFD study, the use of different types of diffusers at the air outlet from the supply duct to the room was addressed. It was recommended to use adjustable nozzles, which allow one to direct the air flow into the room according to the user's preference. Consequently, it was verified that the ventilation unit meets the hygienic noise limits, both for day operation and for night operation with reduced power.

Relationship between bioaerosol particle size and ventilation removal for airborne infections

Yuta Muto — 2022-05-16

It is now suggested that COVID-19 can cause airborne infection by fine particles called droplet nuclei and reducing the risk of indoor infection through ventilation is attracting attention as a part of countermeasures against infectious diseases. However, indoor ventilation planning does not take into account the deposition of fine particles on the floor due to gravitational settling or on the wall due to inertia, and thus there is an urgent need to establish appropriate ventilation rate and methods. Therefore, this study aimed to clarify the effect of gravitational settling of suspended particles and ventilation characteristics by natural ventilation using the temperature difference between indoor and outdoor, and evaluated the outflow characteristics and removal efficiency of suspended particles by natural ventilation using CFD analysis. When the outdoor temperature is 5 ºC, particles with a diameter of 80-100 μm are deposited on the floor by gravitational settling in about 20 seconds and are almost completely removed. Particles with diameters of 10 to 70 μm are also deposited by gravitational settling, but some of them are carried by the circulating flow generated in the room by natural ventilation, so the decay of concentration is slow. When the outdoor temperature is 35 ºC, particles with diameters of 30 to 100 μm are almost completely removed from the space in about 30 seconds due to gravitational settling and floor deposition by downward flow generated near the opening. Particles with a diameter of 10 to 20 μm are partially transported by the circulating flow, so that the concentration decay is slow.

Determination of ventilation effectiveness with tracer gas methods under COVID-19 conditions

Beat Frei — 2022-05-16

We report in this paper on the use of tracer gas methods and two tracer gases to determine ventilation effectiveness under COVID-19 conditions in a large concert hall in Lucerne, Switzerland. The occupancy of the concert hall was simulated by using thermal dummies and partial occupancy of people because of the COVID-19 protection regulations. Contaminants are removed very efficiently in the parquet (by factors better than with mixed ventilation). On the stage and balconies, the local ventilation effectiveness with displacement ventilation is partly comparable to mixed ventilation or even lower. The ventilation of balconies and galleries is demanding and must be carefully assessed in the case of pandemic risks. For the assessment of infection risk through aerosol transmission, a characteristic value for the entire room is not sufficient. The ventilation effectiveness and contaminant removal effectiveness depend very strongly on local boundary conditions and the prevailing flow conditions when dosed locally. The investigations show that the tracer gases sulphur hexafluoride (SF6) and 2,3,3,3-tetrafluoropropene (R1234yf) provide comparable results in determining the air exchange rate and ventilation effectiveness. With both tracer methods, it is possible to gain knowledge about the operation of the ventilation system (e.g. volume air flows, heat recovery leakage).

Unsteady Ventilation in a Scaled Room Model with Swirl Ceiling Diffusers

Eva Mesenhöller — 2022-05-16

Mechanical ventilation of buildings is generally based on steadily operating systems. This field is well known and established. But, an approach based on time-varied supply flow rates might improve indoor air quality, comfort, and energy consumption. Typical time-scales of the variation are in the order of seconds or minutes. Until now, the effects of unsteady ventilation scenarios are not fully described and so, reliable dimensioning rules are missing. Hence, with a better understanding of the flow in unsteady ventilation, systems can be calculated and optimised. To understand the effective mechanisms and derive functional relations between the flow field and variation parameters, full-field optical flow measurements are executed with a particle image velocimetry (PIV) system. Experiments are conducted under isothermal conditions in water in a small-scale room model (1.00 m × 0.67 m × 0.46 m) with two swirl ceiling diffusers, Reynolds-scaling assures similarity. In a series of experiments, the effects of different unsteady ventilation strategies on the flow fields are investigated and compared to steady conditions with the same mean exchange rate. Mean exchange rates, signal types, periods, and amplitudes are varied. Time-averaged normalised velocity fields already indicate notable differences between steady and unsteady cases especially for lower exchange rates: the distribution is more homogeneous in unsteady scenarios compared to steady conditions, and low-velocity areas are reduced while the mean velocity of the room increases. So, unsteady ventilation might be beneficial in terms of improved ventilation and energy savings in partial-load operation. Fast Fourier Transformation (FFT) analyses of the mean velocity for each field over the whole series detect the main frequency of the volume flow variation. By dividing the velocity field into smaller areas, this main frequency is still detected especially in the upper part of the room, but side frequencies play a role in the room as well.

A Study on the effect of the Wind Catcher in Apartment Buildings

Kotaro Ishikawa — 2022-05-16

In recent years, there has been growing emphasis on natural ventilation for energy conservation and intellectual productivity. However, in urban areas with a high building density, it is difficult to let in fresh outdoor air into the room, and installing a wind catcher (WC) is considered an effective solution. In this study, we conducted wind tunnel experiments and computational fluid dynamics (CFD) analysis to verify the ventilation-enhancing effects of installing WC in apartment buildings. Two models are used in this study. In the initial stages of wind tunnel testing and CFD analysis, we used a model without adjoining rooms to determine the correspondence of the wind tunnel test values to the CFD analysis values. Subsequently, CFD analysis was performed using the model with an adjacent room, and comparisons were made with the model without an adjacent room. Using the model with an adjacent room, we also studied the difference in the ventilation volume depending on the wind direction and ventilation volume with a single-sided opening. Consequently, we determined the following: 1.The pressure difference between the inlet and outlet openings was smaller in the model with an adjacent room than in the model without an adjacent room, and the ventilation volume was smaller. In other words, installing a WC in an apartment building can create a pressure difference, which is considered effective in promoting ventilation. 2.The WC works effectively for the wind flowing parallel to the opening.

Monitoring (N)ZEB dwellings in the Netherlands Lessons learned from current practices

Olivia Guerra-Santin — 2022-05-16

Monitoring the energy performance of very low and zero energy buildings is fundamental to evaluate the efforts made to transition into an energy neutral built environment. Post occupancy monitoring has been embedded into current practice, supported by the availability of smart meters and affordable sensor technology. However, there is still a lack of standardised monitoring guidance, which complicates the comparison between projects. In this study, we reviewed reports and publicly available documents related to the monitoring of low energy and zero energy projects in the Netherlands. A total of 12 studies reporting on 65 projects containing 4,400 dwellings were analysed. These included both new and renovated housing built in the last decade. This study aims to provide an overview of actual energy performance in energy renovation projects across the Netherlands. It also analyses the difference with predicted energy performance and analyses the perceptions of residents involved in low and zero energy renovations. It answers questions such as: What energy and behavioural data is being gathered through energy monitoring in the residential sector (related to monitoring low and zero energy buildings/dwellings)? How is the data currently being utilized? What does the data tell us about actual energy use and resident perceptions? How can monitoring be improved to help develop better energy models, and help building owners optimize their investments in energy renovation projects? The results indicate that even though monitoring building performance in the Netherlands could be considered common practice, the results are seldomly reported or communicated. Furthermore, very few projects monitor indoor conditions and occupants’ behaviour. As a consequence, the performance gaps found in these projects are not fully understood. These findings are summarised to provide an overview of the main goals for monitoring from a practical point of view. These findings are used to provide recommendations for monitoring setups according to the final goals.

Simulation aided development of a façade-integrated air handling unit with a thermoelectric heat exchanger

Vojtech Zavřel — 2022-05-16

The paper presents a simulation aided development of a new type of a façade-integrated air handling unit for local ventilation of rooms. The unit is developed as a part of the Plug-and-Use (PnU) concept within the H2020 project PLURAL. Unlike conventional local ventilation units designed solely for ventilation, the developed air handling unit has a two-stage heat recovery that combines a passive and an active heat exchanger. The active heat exchanger consists of an array of thermoelectric elements and provides the flexible and energy efficient capability of temperature control of supplied ventilation air. The paper demonstrates the practical use of building energy simulations for the development of the unit. A combined simulation approach was used, while the IDA ICE software addressed the indoor CO2 concentration and related ventilation volume flow rates used for the TRNSYS software, which predicted energy performance and indoor thermal conditions. In the TRNSYS, a numerical representing the initial prototype of the air handling unit was prepared. This sub-model was integrated into the TRNSYS building model of the real installation demo site, namely, the Terrassa building, Barcelona, Spain. A variant numerical analysis was performed with two different compositions of the building envelope (pre- and post-renovation) and several ventilation control strategies and air handling unit operation settings. The performed simulations were capable to predict the performance of the innovative device in the real-case arrangement, under various scenarios, on the scale of the entire building. The simulation analysis demonstrated that the façade integrated air handling unit can clearly improve the IAQ conditions and reduce the overheating in the case when no other cooling system is available. The simulations provided an important navigation for the design team to further develop the innovative device.

Thermal inactivation of the corona virus (SARS-CoV-2) in air volumes

André Schlott — 2022-05-16

To control the spread of viruses (e.g., SARS-CoV-2) and other pathogens in a pandemic situation, slowing down the rate of spread is an essential goal that can be achieved by interrupting transmission chains. According to the current state of knowledge, SARS-CoV-2 is mainly transmitted by droplet infection through virus-containing aerosol clouds in the air. These aerosol clouds are mainly produced by exhalation and can be reduced by wearing medical masks. In closed rooms, there is an increased probability of infection by aerosols. Countermeasures include various recently developed air cleaning technologies. Most of these technologies available on the market are based on filters with a limited lifetime to remove the virus load from the air or different sterilisation methods like UV irradiation. The air cleaning technology presented focuses on the thermal inactivation of viruses beyond their temperature sensitivity by heating the air. In the developed apparatus, the potentially germ-carrying ambient air is sucked in and conditioned in such a way that it is exposed to a certain temperature for a defined period of time. Before the inactivated / hygienised air is returned to the environment, it is cooled down to almost room temperature. The recovered heat remains in the system and is used to heat the intake air. The use and combination of different technologies enable the most efficient air disinfection possible. Four different experiments were conducted. After determining a base line, the air was solely passed through the pump, through the whole »Virus-Grill« pressure free and with an elevated pressure of 1.5 bar. In all experiments (except the baseline) the number of active viruses were reduced below the limit of detection.

Simulated thermal comfort in renovated houses with low temperature heating

Victor Ghering — 2022-05-17

Low Temperature Heating (LTH) of buildings is a key feature when switching to renewable energy. Even when the capacity of LTH is high enough, LTH may adversely affect indoor thermal comfort in case buildings are not suitably insulated. This paper goes deeper into methodological issues when conducting a thermal comfort assessment. Thermal comfort is either quantified by Fanger’s Predicted Mean Vote (PMV) or ranked in building comfort classes in the adaptive model. In both cases, one of the main parameters influencing comfort is the Mean Radiant Temperature (MRT). This study addresses issues with common MRT and PMV calculations in energy simulation software. The case study is TRNSYS 17. Several MRT and PMV calculation methods are compared, showing possible draw-backs and deviations from comfort standards NEN-EN ISO 7726 and 7730. For instance, in the standard heating settings in TRNBuild only the total heating capacity is specified. The radiative part is then distributed area-weighted over opaque surfaces. A more detailed option in TRNBuild is to specify the locations of radiative gains as points. In both cases, the MRT at a comfort sphere is calculated with Gebhardt-factors instead of view-factors. The standard settings may be considered too simplified for detailed comfort studies whereas the detailed model shows deviations from comfort standards NEN-EN ISO 7726 and 7730. Therefore, two additions to these models are proposed to increase accuracy. One addition is an ordinary detailed model with radiative gains as point sources in order to retrieve all surface temperatures during a desired period of time. In the second addition walls with radiators are split-up and planes are added at the locations of radiators to generate a view-factor matrix. This can be done in TRNBuild, but also in other view-factor calculation software. From model 1 all surface temperatures are retrieved. Combined with the view-factors from model 2, the MRT can be calculated.

Learning communities, installation sector, energy transition, professional development

Wouter van Marken Lichtenbelt — 2022-05-18

Even today, comfort and health are still considered as synonyms in the design of the indoor climate. On top of that there is a strong focus on average-person comfort which has resulted in tightly controlled indoor air temperatures. Our studies show that regular exposure to temperatures outside the thermal neutral zone may result in significant health benefits. Exposure to cold, but also to heat, positively affects our metabolism, the cardiovascular system, and, in addition, ‘trains’ our resilience to extreme temperatures (heat waves and cold spells). Importantly, it is not necessary to be exposed to extreme temperatures: mild cold and mild warm environments can already elicit beneficial health effects. Translating these insights to the built environment leads to the concept of dynamic indoor conditions. Here, we show that a dynamic indoor climate is acceptable or even pleasant and will contribute to a healthy indoor environment and, because of less strict climate control, will result in lower building energy consumption.

Productivity prediction via human physiological signals for an optimum thermal environment

Dongwoo Yeom — 2022-05-17

This study aims to understand the relationship between indoor temperature, physiological signals, thermal sensation, and productivity and to estimate the occupant’s productivity. A series of human experiments were conducted with 48 participants, and local skin temperatures, heart rate, and thermal sensation data were collected in 6 temperature conditions. OSPAN (Operation Span Task) was used to measure the occupant’s productivity and the LightGBM algorithm was used to generate a predictive model. The result verified that there is a significant correlation between certain local body skin temperatures and the occupant’s productivity, and the overall thermal sensation between high and low performing groups was significantly different by gender and BMI groups. The result suggested gender, BMI, and two local skin temperatures as effective factors to predict the occupant’s productivity.

Evaluation of “ventilation resilience” in mid-sized office buildings

Douaa Al Assaad — 2022-05-19

In industrialized countries, people spend 80-90% of their times indoors, thus, providing them with clean spaces that preserve their wellbeing and productivity is critical. This can be done by delivering scheduled or demand-driven amounts of clean air that dilute the concentration of generated pollutants to adequate levels. However, the building and its ventilation system might be subjected to unpredictable shocks or disturbances (i.e., sudden failure in system components) that compromise the efficiency of the ventilation design, deteriorate indoor air quality and lead to acute exposure events. The ability of the building and its ventilation system to withstand and absorb the shock and maintain the IAQ design conditions is termed as “ventilation resilience”. In this work, a typical open-plan office equipped with a balanced variable-air-volume mechanical ventilation system, is considered. Its ventilation resilience was assessed against power outage shocks and additional occupancy beyond expected peaks. Two types of pollutants were considered (exhaled CO2 and formaldehyde from exhalation and office surfaces). To conduct this study, a Building simulation model was developed for the office and AHU in Modelica using Dymola. Results showed that for the considered shocks, no VOC violations were noted due to low emission rates. This was not the case for CO2: For power outage shocks, the building/ventilation system were resilient for up to 15 minutes of shock and for 1 additional occupant in the space. Beyond those limits, the building/ventilation system are no longer resilient. For 60 minutes of power outage shock, CO2 violations (>900 ppm) of 2 hours were noted with peaks of 1240 ppm while for 6 additional occupants, CO2 violations of 2 hours were noted with peaks of 1150 ppm. A combined shock of these two cases caused 3 hours of violation and peak concentrations of 1747 ppm.

Development and initial testing of a Personalized Environmental Control System (PECS)

Ongun B. Kazanci — 2022-05-19

Personalized Environmental Control Systems (PECS) condition the immediate surrounding of occupants in contrast to conventional HVAC systems. PECS have several advantages including allowing occupants to adjust their immediate surroundings according to their preferences, which could improve their satisfaction with the indoor environment, which may lead to higher productivity. PECS can also lead to noticeable energy savings, if implemented effectively in buildings. The present study explains the development process and initial testing of a novel PECS. The PECS had heating, cooling, and ventilation functions, together with the possibility of adjusting lighting color and brightness. Ventilation and cooling were provided from a desktop air terminal device, and heating was provided by a curved panel covering the lower body from the thigh to the lower leg of a seated occupant. A thermal manikin was used to quantify the heating and cooling performance of the different versions of the PECS. The most recent prototype was able to provide a cooling effect up to 6 K (calculated by the manikin-based equivalent temperature difference) to the left side of the face, and a heating effect of up to 5 K to the left and right thighs. The cooling and heating effect of the whole body was up to 0.3 K and 1.3 K, respectively. A Peltier element was introduced to lower the supply air temperature from the PECS, but had limited effect on the cooling effect despite the large increase in power use. When implementing a Peltier element in PECS, the generated waste heat must be handled so that it does not interfere with the cooling.

Revisiting radiant cooling systems from a resiliency perspective

Ongun B. Kazanci — 2022-05-19

Radiant heating and cooling systems have been proven to be an energy-efficient and resource-effective heating and cooling solution for buildings. One of the key features of radiant systems is the possibility of activating and controlling the thermal mass. This feature allows spreading the heat removal from indoor spaces over a longer period, compared to more conventional systems e.g., air-conditioning. This feature of radiant systems could be particularly beneficial under heat wave and power outage events. The present study investigated the performance of Thermally Active Building Systems (TABS) and Packaged Terminal Air Conditioners (PTAC) in terms of controlling indoor temperatures under future typical weather files, and under future heat wave and power outage events. The simulations were carried out for Copenhagen, Denmark. For future typical meteorological years, TABS performed better with heavyweight construction, but PTAC had little influence from the construction type. During heat waves, both systems were able to maintain a generally comfortable temperature range but with a slightly overall higher temperature. When a heat wave and power outage occurred at the same time, the cases with heavyweight construction had lower temperatures regardless of the cooling system. With TABS and heavyweight construction, the room temperature was maintained within the comfort range of 26°C for 16 hours after the heat wave and power outage started. After the power outage was over, TABS with heavyweight construction was able to reduce the room temperature to the comfort condition of 26°C faster than PTAC by 18 – 71 hours. Results obtained from this initial set of simulations suggest TABS could be a better solution than PTAC in terms of its resiliency to heat waves and power outages although both systems could have different advantages depending on the operation, building type and building use.

Development of the TAIL rating scheme for indoor environmental quality in schools

Minh-Tien Tran — 2022-05-19

The TAIL rating scheme was developed to assess indoor environmental quality (IEQ) in offices and hotels undergoing deep renovation and was recently extended by the PredicTAIL method allowing prediction of IEQ through modeling. TAIL provides the methodology for rating the quality of the thermal, acoustic, and luminous environments, the indoor air quality, and the overall quality of the indoor environment. The present work is an extension of the use of TAIL rating scheme for school classrooms to provide necessary information for effective actions and mitigation measures to improve classroom IEQ. The TAIL was invented by examining the literature and certification schemes to identify the parameters that characterize IEQ in offices and hotels; 12 parameters were selected. A similarly pragmatic approach is followed when developing the TAIL for schools. The literature published after 2010 was surveyed to identify papers presenting measurements of IEQ in classrooms in Europe, the USA, and Australia; 75 papers were identified. Besides the 12 parameters already included in TAIL, the studies also used other parameters to characterize classroom IEQ. These parameters will be evaluated for their importance for the teaching, learning, and well-being of pupils, as well as measuring complexity, among others. Based on this assessment, the relevant parameters will be selected for inclusion in the TAIL rating for schools. The selection will be assisted using the measurements from the extensive campaign organized by the Indoor Air Quality Observatory in 308 schools and 602 classrooms in France; some of these data will be used to assess the efficacy of the TAIL for schools indicator. The relationships between the newly developed TAIL for schools, the teacher’s perceptions of indoor environmental quality, and detailed building characteristics will be studied.

Effects of humidification process on the thermal behavior of floor heating systems

Tianying Li — 2022-05-19

Since the outbreak of the Covid-19 pandemic, working from home has become the norm for millions of workers in the world. Indoor humidification and heating are essential for health and comfort in a dry and cold climate. In order to investigate the interaction between humidification process using a cool mist humidifier and the heating process using a floor heating system, a total of 4 experimental tests were carried out, which included three experimental groups with humidification process in the conditions of three relative humidity setpoints (45%, 55%, 65%), and one control group without humidification process. In the process of experiments, indoor relative humidity of the control group basically maintained around 30%. Therefore, the heated room would be dehumidified to about 30% before each experiment started. The indoor temperature was maintained at 25 ℃ by the floor heating system. Obtained results showed the floor heating system was stimulated to reheat the room due to the cooling effect of the humidifier and a new balance was established in the process of competition between the evaporative cooling and floor heating. When humidifying air to over 45%, it would lead to floor overheating. Furthermore, the humidification process improves the non- uniformity of air temperature distribution, but at the same time brings more uneven RH distribution. Besides, the energy consumption increases following with the rising of setpoints of RH, and the growth rate is 60%, 87% and 100% respectively for RH 45%, 55% and 65%. In conclusion, the optimal setpoint of the humidifier is RH 45% based on a comprehensive consideration of health, thermal comfort and energy consumption.

Machine Learning Models for Indoor PM2.5 Concentrations in Residential Architecture in Taiwan

Lin Yu Chen — 2022-05-19

People typically spend 80-90% of their time indoors. Therefore, establishing prediction models estimate particulate matter (PM2.5) concentration in indoor environments is of great importance, especially in residential households, in order to allow for accurate assessments of exposure in epidemiological studies. However, installing monitoring instruments to collect indoor PM2.5 data is both labor and budget-intensive. Therefore, indoor PM2.5 concentration prediction models have become critical issues. This study aimed to develop a predictive model for hourly household PM2.5 concentration based on the artificial neural network (ANN) method. From January 2019 to April 2020, PM2.5 concentration and related parameters (e.g., occupants’ behavior information and ventilation settings) were collected in a total of 62 houses and apartments in Tainan, Taiwan (tropical and subtropical region). Overall, 2136 pairs of data and 9 possible variables were used to establish the model. Meteorological data were primarily used to establish the model. Meanwhile, occupants’ behavior and building characteristics were generalized as effective opening areas to describe the importance of ventilation in subtropical areas. We performed five-fold cross-validation to assess prediction model performance. The prediction model achieved promising predictive accuracy, with a coefficient of determination (R2) value of 0.88 and a root mean square error value of 3.35 (μg/m3), respectively. Outdoor PM2.5 concentrations were the most important predictor variable, followed in descending order by temperature, outdoor carbon dioxide concentration, outdoor relative humidity, and opening effective areas. In summary, we developed a prediction model of hourly indoor PM2.5 concentrations and suggest that outdoor meteorological data, building characteristics, and human behavior can be powerful predictors. The results also confirm that the model can be used to predict indoor PM2.5 concentrations across seasons.

Age of Air Measurement in Air-recirculating Systems Applying Dynamic Steady-state Concentration Theory

Haruki Taguchi — 2022-05-19

In open air systems which is rooms with ventilation by fresh air, the evaluation of an indoor air environment based on age of air measurement, such as a stepdown method using tracer gas, is widely applied. However, in a ventilation room with air-recirculating systems such as multiple packaged air conditioning unit systems, the concentration continues to increase endlessly when there is no ventilation with fresh air. Thus, it is not possible to measure the air age using the conventional experimental method, as noted. Therefore, in previous studies, a tracer gas experiment was established by applying a dynamic steady-state concentration theory. The dynamic steady-state concentration is the concentration transition of each single source, assuming that the steady-state concentration is composed of the difference between the room source and the recirculating source. Previous studies have confirmed that the dynamic steady-state concentration agrees with the equivalent steady-state concentration in the ventilation room of an open air system. In addition, simulations by computational fluid dynamics (CFD) analysis and tracer gas experiments in the laboratory showed that the dynamic steady-state concentration of only the recirculating part of the source equals the age of air. With all these methods and studies, we attempted to extend to a real space with air-recirculating systems using the tracer gas experimental method based on dynamic steady concentration. First, we measured the air age in a real space with multiple packaged air-conditioning unit systems. We thereafter confirmed the distribution property of the multiple packaged air conditioning unit systems and verified the validity of the quantitative evaluation using CFD analysis. Our findings were as follows:

1.The age of the air measurement in a room with two or more recirculating parts was clarified by applying the dynamic steady-state concentration theory. 2.The tracer gas experiment of the dynamic steady-state concentration enabled the quantitative evaluation of the air distribution characteristics of the multiple-packaged air-conditioning unit system in real space.

Effects of supply air temperature and pollutant location on concentration characteristics with a night-time ventilation in a school classroom

Sami Lestinen — 2022-05-19

Night-time ventilation is used to remove indoor pollutants before the occupied periods. However, a lack of knowledge exists on how well a minimum level of ventilation can dilute pollutants during the night, and how a location of a polluting source and a supply air temperature affect the concentration levels with a typical mixing ventilation strategy. Therefore, the constant polluting source of 12 mg/h was defined on the floor (60 m2), sidewall (17 m2), and floor-corner (1 m2) describing a low-polluting floor material of 0.2 mg/h,m2 (EN 15251:2007). The objective of the study was to demonstrate a minimum night-time ventilation scenario of 0.15 L/s,m2 with the isothermal supply air, underheated supply air (-4°C), and overheated supply air (4°C) compared to indoor air initial temperature. Furthermore, the temporal and spatial concentration characteristics were considered. The daytime ventilation was 3 L/s,m2 with the underheated supply air temperature. Both the night and the day periods lasted 12 hours. The room air distribution was arranged by using 2 corridor wall supply air grilles and 4 exhaust air valves. However, only 1 grille and 2 valves were used at night. ANSYS CFX tools were used for numerical modelling. The RANS and URANS simulations were carried out with the implicit pressure-based multigrid coupled solver. The second-order discretization schemes were used in space and time and the SST-model was chosen to model turbulence with the automatic wall treatment. The convection diffusion equation was used in scalar transportation. The measured data were used as boundary conditions and the computational grid adaptation was applied to improve accuracy. The results show that the underheated supply air provided the lowest concentration level in the occupied zone because the low-temperature supply air flowed down to the floor and dilute well the occupied zone. The overheated supply air, in turn, provided the largest concentration level in the occupied zone because the heated air was not mixed well in the room. The isothermal supply air provided a circulating airflow pattern increasing the concentrations beyond the supplied airflow region. The daytime ventilation decreased the cumulated night concentrations to one-tenth within an hour.

Application of Adapted Tracer Gas Test for Ventilation Assessment in Two Locations

Sarah L Paralovo — 2022-05-19

In the wake of the current worldwide COVID crisis, the vital role of ventilation in keeping healthy indoor environments has become increasingly clear. But even before that, researchers have been pointing out how crucial ventilation is in avoiding the accumulation of pollutants in indoor spaces and in interpreting indoor air quality (IAQ) data. Given the importance of ventilation, especially in estimating pollutant sources’ strength and proposing remediation actions, it is imperative that IAQ assessments quantify the actual building ventilation rates. However, many IAQ field studies found in the literature do not report ventilation rates adequately. This paper describes the application of an alternative method to passively measure the average ventilation in two different locations. This alternative method consists of an adaptation of the traditional tracer gas test (TGT) used for long term average air change rates (ACH) measurement. This adapted TGT employs an alternative tracer gas (decane-D22) that is more adequate than the currently employed SF6 and perfluorocarbons. The selected tracer can be co-captured and co-analysed with commonly assessed VOCs by commercial passive IAQ-sampling. A passive source design of decane-D22, optimized in lab, provides stable and repeatable emission rates unaffected by varying RH and ACH. The actual source emission rate is determined from the average room temperature via an exponential prediction curve derived in lab. Results from the two field experiments described in this paper show the satisfactory applicability of the proposed adapted TGT in different types of environments and settings. The ultimate research goal is to provide an accessible enough method to quantify ventilation that it may encourage researchers, contractors and building owners to perform appropriate ventilation assessments more often and with a good degree of accurateness.

Ventilation and air conditioning for school buildings

Pavol Štefanič — 2022-05-19

One of the basic problems of school buildings is the unsatisfactory thermal insulation properties of peripheral building structures. Unsatisfactory, especially in terms of the creation and long-term maintenance of microclimatic conditions in the classroom, is the complete absence of mechanical ventilation systems. In almost all schools, ventilation is based on the natural exchange of air through windows. Such a solution is no longer satisfactory today. In the old school buildings, the old ventilation shafts were usually abolished and in the new schools, there are no such shafts at all. In general, in many places, it is also forbidden to open windows during breaks for safety reasons. In addition, the method of window ventilation is based only on the subjective feelings of teachers and students; and since the human factor is unable to determine sufficient air quality with the help of its organs, the result is that the interior is not sufficiently ventilated. This also results in an unacceptable concentration of CO2 in the classroom, a high level of resistance, an increasing level of relative humidity, and dust content in the indoor air. This is an unacceptable situation for teachers 'and students' health. The quality of the indoor environment of school buildings directly impacts the ability to concentrate and the attention of teachers and students. In this article, we will take a closer look at 6-week experimental measurements of the indoor microclimate in kindergarten. The measurement took place in two rooms, a playroom and a bedroom, where there were 22 children plus 1 or 2 adults at the same time. The measurement results for some quantities are acceptable, but in particular, the concentration of carbon dioxide is unacceptable.

The relation between occupant’s mood state and thermal sensation

Cihan Turhan — 2022-05-19

Thermal comfort is mainly evaluated by the Fanger’s Predicted Mean Vote/Predicted Percentage of Dissatisfied (PMV/PPD) method and adaptive thermal comfort approaches. PMV/PPD method takes four environmental (such as indoor air temperature, relative humidity, mean radiant temperature and air velocity) and two personal parameters (basic clothing insulation and metabolic rate) into account for calculations. On the other hand, adaptive approach adds human behaviours to the thermal comfort models. However, none of these models includes the effect of the mood state of the occupants on thermal sensation. To this aim, this study investigates the relationship between occupant’s mood state and thermal sensation as a case study. Pre-test-Post-test Control (PPC) experimental design is conducted on the students in a university study hall in Turkey. Profile of Mood States (POMS) is used to examine the effect of mood state on the thermal sensation while the Actual Mean Vote (AMV) is obtained via developed mobile application. Simultaneously, the PMV is calculated in order to obtain the difference from the AMV. The results showed that there is a strong relationship between the mood state and thermal sensation. The outcome of this study would enlighten the HVAC engineers and specialists in order to understand the gap between PMV and AMV caused by the mood state.

Development of an automatic sliding window system to control adequate ventilation rate

Akane Tsutsumi — 2022-05-19

Under the influence of COVID-19, it is recommended to ventilate to reduce the risk of infection in the room. In an air-conditioned room, window open can increased the ventilation rate that caused by indoor and outdoor temperature difference. However, there is a concern that opening the window in the air-conditioned room will increase the heating and cooling loads due to air leakage. In addition, it is difficult to maintain the appropriate ventilation rate, because the outdoor air temperature changes from time to time. To solve this problem, we have developed an automatic window opening system to control the natural ventilation rate. This system can be controlling the appropriate ventilation rate for the room by adjusting the opening area of window automatically. In this study, actual measurements were conducted to understand the operating performance of the system, and its effect on the indoor thermal environment. The measurements were conducted in summer and winter season, and the results were compared between the developed window opening system and 95 mm width opened ordinary window. As a result, it was confirmed that the ventilation rate could be controlled by this system. In addition, in the case of the developed window opening system, the system controlled the ventilation rate when there was a large difference in indoor and outdoor temperatures, which prevented the deterioration of the indoor thermal environment and reduced the heating load compared to the ordinary window.

Local heating and cooling effectiveness - an evaluation method based on calculated local and overall thermal state

Mohamad Rida — 2022-05-19

The application of Personal Comfort Systems (PCS) in the buildings demonstrated their potential to improve thermal comfort and reduce energy use by the space conditioning HVAC systems. With its personal controllability (on-demand) PCS is a practical solution to tackle the diversity in perceiving thermal comfort between occupants. The differences in thermal perception can be due to several physiological and psychological factors, such as metabolic rate, acclimatization, body composition, gender, and age. In addition to the primary purpose of improving individual thermal comfort, it allows for a wider set point temperature of the HVAC system conditioning the overall space, which may lead to an extensive reduction in energy use. Several PCS device options have already evolved, but incorporating these devices into building conditioning faces lots of restrictions. The PCSs are categorized between movable, portable, and fixed devices, and PCS devices can function with different means of heat exchange. In this study, the capability of local heating and cooling to correct the individual's thermal state toward thermal neutrality when the rest of the body is exposed to cold or heat was evaluated. For this purpose, a detailed physiology model was applied to evaluate the impact of the nonuniform environment from PCS on local skin, heat flux, and thermal comfort. Different locations of the human body (head, hands, feet, legs, thighs, back, and pelvis) have been tested since the heat exchanged at local body parts differs in its effectiveness in improving the overall thermal state. Different temperature relaxations have been tested with a base cooling setpoint of 25°C and heating of 24°C operative temperature. Multiple simulations have been conducted to account for multiple local environmental settings. In this study, we have evaluated the influence of local heating and cooling of different body parts on correcting the whole-body thermal state toward thermal neutrality. Results showed that the thigh could be a promising prominent body part for both cooling and heating, followed by the hands and feet, which are good responders to local heating. The percentage of correction toward thermal neutrality varies with background temperature and local heating or cooling power, and can range from 50–80% for hands and feet to 60–100% for the thigh.

Field study of diffuse ceiling ventilation performance under high air change rate

Gael Tougne — 2022-05-19

Diffuse ceiling ventilation utilizes the entire ceiling surface to distribute airflow to rooms. The air seeps via perforations, often present in acoustic ceilings, from the pressurized plenum to the occupied zone below. In the literature, this concept has proven superior in terms of draught, even for quite high airflow rates and sub-temperatures. However, documentation of practical installations followed by measurements campaigns and in-depth analyses of the concept, are rare. Consequently, we present a study to showcase the performance of the installation under rather extreme conditions: air change rate of 20 h-1 and supply temperature 3- 4°C below room temperature. The corresponding cooling was 56-74 W//m2. The investigated room was 165m² and 2.75m high. Numerous computers and TV screens caused significant heat loads, as well as the large windows on 3 facades of the room (West, North, East). The ventilation, equipped with a cooling coil, supplied 9200 m³/h to maintain the temperature in the room. The airspeeds and temperatures were measured at 7 different heights (from 0.1m to 2.4m) in 26 positions. The results showed an even distribution of the temperature in the room with measurements between 23 and 26˚C and an average temperature gradient of 0.33˚C/m (max 0.8˚C/m) while in the plenum the difference of temperature was 1.5˚C between the inlet and the opposite corner. The airspeeds were on average between 0.11 m/s and 0.17 m/s with the highest values at the ankle level. Half of the logged points had Draught Rate (DR) below 10% and all positions were below 20% except one. The airspeed exceeded 0.2m/s in less than 9% of the measurements. For comparison, we discuss the implications of using ceiling swirl diffusers or displacement ventilation in the same context.

Assessment of the Indoor Environment Quality in UM6P Classrooms

Houda Er-retby — 2022-05-20

The present study is the result of a global study conducted by the students of the Master Program "Green Building Engineering and Energy Efficiency" at the School of Architecture Design and Planning (SAP+D) of Mohammed VI Polytechnic University (UM6P) in Benguerir, Morocco. The study is a hands-on experience that allows the master’s students to learn by doing about the concepts of the indoor environment quality, in addition to the classroom training. The objective of the study is to assess the indoor environment quality of selected classrooms in different buildings of the UM6P campus. To this end, seven classrooms were monitored by means of sensors that measure all the IEQ parameters including thermal, acoustic, and lighting. In addition, the occupants of these classrooms were asked to fill out a survey based on a questionnaire. In this paper, we report a sample of the results of this study relative to one classroom. The analysis of these results reveals that students' thermal perceptions differed because they were divided into three vote categories: neutral, feeling slightly hot, and feeling slightly cold. Based on the survey analysis, the percentage of each category varied during each session. The obtained results were later compared with the thermal comfort model, and the two approaches showed a good match in terms of describing the overall satisfaction of the occupants.

Crossed effects of visual factors on human thermal response

Roberta Jacoby Cureau — 2022-05-20

Recently, the approach for studying human comfort indoors has been changing for a multi-domain framework once some studies have reported cross-effects between different comfort domains (i.e., thermal, visual, acoustic, and air quality). An example of cross-effects between comfort domains is the hue-heat hypothesis (HHH), referring to the possible association between lighting and the human thermal response. This paper presents a new investigation to verify the validity of the HHH. Several experiments were conducted in a test room under a fully controlled setting, combining two thermal (slightly cold and slightly hot) and three lighting conditions (blue, red, and white lights with nearly the same illuminance level). The experiments were divided into two parts, each one dedicated to a thermal setting. After acclimatisation, the participants were submitted to each colour of light for seven minutes under a constant air temperature. A total of 39 people participated twice in the experiment, each time in a different thermal condition, and before changing the colour of light, they answered a survey about their thermal sensation, thermal comfort, visual comfort, overall comfort, and perceived level of productivity. Answers were compared using statistical methods. The results did not allow to confirm the HHH, since no statistically significant differences were observed for thermal comfort and thermal sensation for the different colours of light. The only significant difference observed was for visual comfort in the slightly cold thermal condition, between red and white lights. In fact, the survey responses for visual comfort indicate that people preferred the white light. White light was also associated with better overall comfort assessment and perceived productivity in both thermal conditions, but the differences were not statistically significant. Further investigations should be performed under more thermally stressful environments and should also evaluate the physiological factors of participants as a thermal response instead of only subjective outcomes.

Monitoring the indoor environment for older people with dementia

Chuan Ma — 2022-05-20

Dementia is a syndrome that progressively affects cognitive, behavioural and psychological functions. People with dementia may have difficulties in sensing and expressing indoor environmental changes. Sensor technologies, such as environmental sensors, can be used to evaluate indoor environmental quality by accurately detecting the indicators, including air temperature, relative humidity, illuminance, noise level, CO2, TVOC, and particulate matter. Monitoring these indicators for older people with dementia helps maintain their health and comfort. Moreover, some clues of behaviours and symptoms of older people with dementia could also be shown in the sensor data. This study used a mixed-method approach to find the links between indoor parameter variations and residentsâ€™ activities. In a care home in the Netherlands, we collected quantitative environmental data through a sensor network deployed in bedrooms and central living rooms, and the care professionals filled qualitative data by diaries. Ten residents and two care professionals were recruited to take part in observation and diary recording. During two months monitoring campaign, care professionals selected one week that recorded five-category information on residentsâ€™ daily lives: 1) building facility operation; 2) external factors; 3) details in daily lives; 4) problem behaviours or symptoms; 5) indoor comforts. By comparing the two types of data obtained, residentsâ€™ wandering and sleeping problems have been found that coincide with the data fluctuations to some extent. The timing and process of these behaviours can be presented through data analysis. But more underlying factors in behavioural changes of people with dementia still require long-term observation and validation of future research.

Simulation of the effect of windcatchers on air quality inside courtyards

Hayder M. Khan — 2022-05-19

The courtyard is an essential traditional building element for sustainable construction in hot arid areas. However, there are some limitations in using it for future sustainable buildings. One of these is air quality, where previous research indicates that the courtyard provides thermal comfort to its residents by generating a microclimate that isolates the courtyard from external air, but this can reduce the building's ventilation potential. Traditional houses in the Middle East use windcatchers as a solution to this problem. This paper shows the results of a numerical simulation of a courtyard with windcatchers in traditional houses. The results indicate that windcatchers can provide enough fresh air for ventilation. It can also reduce the outdoor air temperature by using the thermal mass of the windcatcher wall and earth cooling, but will not provide low enough temperatures to maintain the microclimate, which suggests the need for more research in this field.

Evaluation of the ventilation situation in Dutch schools using the QuickScan method

Vinayak Krishnan — 2022-05-20

The COVID19 pandemic has brought especially the health aspect to the forefront and the need to improve ventilation in Dutch schools. To assess the ventilation in schools during the pandemic, the QuickScan method was developed by a large National consortium called ‘Masterplan Ventilatie’. The method contains a list of instructions for users to quickly evaluate the quality of ventilation. As part of this study, 25 TU Eindhoven bachelor students were provided with the QuickScan documentation and children and teacher questionnaires were added to assess the ventilation systems, each in a different Dutch school. These results have been used to identify the possibilities and limitations of the QuickScan method and provide information on the current ventilation status in the investigated schools. Firstly, administrative (i.e., information gathering and reporting) and functional (i.e., measurements and data analysis) groups of steps are distinguished. Secondly, scoring criteria are defined to rate each individual step of the QuickScan performed by the students. The questionnaires pointed at uncomfortable winter conditions, limited possibilities for ventilation control, poor air quality, and inadequate cleanliness for schools. The measurements show that 50% of the schools, which indicated maximum CO2 levels during occupancy, recorded levels above 1200 ppm. About 67% of the studies, which reported the ventilation capacity for the worst or winter operating conditions, recorded insufficient ventilation. The balanced mechanical ventilation system rated better based on the teacher questionnaires while the children questionnaires indicated no preference for a specific ventilation system. The QuickScan evaluation highlighted that 100% of the studies achieved at least 60% completion for the administrative steps and only 52% of the studies achieved at least 60% completion for the functional steps. This study is the first to apply the QuickScan method, report results, and provide an approach to evaluate and suggest improvements to the QuickScan method.

Development of a Non-contact Modular Screening Center (NCMSC) for COVID-19

Jinkyun Cho — 2022-05-20

Under the global landscape of the prolonged COVID-19 pandemic, the number of individuals who need to be tested for COVID-19 through screening centers is increasing. However, there is a risk of cross-infection at each stage of the screening process. To address the risk of cross-infection in the screening center during the COVID-19 testing process, a non-contact modular screening center (NCMSC) was developed that uses biosafety cabinets and negative pressure booths to improve the problems of existing screening centers and enable safe, fast, and convenient COVID-19 testing. The main purpose of this study is to evaluate the effect of the cross-infection prevention of viruses and ventilation performance for rapid virus removal from the indoor space using both numerical analysis and experimental measurements. Computational fluid dynamics (CFD) simulations were used to determine the ventilation rate and pressure difference. We also characterized the airflow dynamics of NCMSCs using the particle image velocimetry (PIV). Moreover, design optimization was performed with three alternatives based on the air change rates and the balance of supply air (SA)/exhaust air (EA) as a ventilation strategy for preventing viral transmission.

The Indoor Air Quality, Ventilation and Energy Nexus in the COVID-19 Context

Talie Tohidi Moghadam — 2022-05-20

In the face of the Covid-19 pandemic and environmental crises, ventilation plays a critical role in the removal of infectious pathogens. A building ventilation paradigm results in excessive energy consumption to ensure indoor air quality. At the time of writing this paper, several studies have been conducted regarding COVID-19 and ventilation; however, the energy challenges of ventilation operation under the pandemic condition has not been fully addressed by previous studies. This paper is based on a literature review of publications, using an internet-based search in different scientific databases. A data-driven keyword analysis on bibliographic data was performed based on English-language textual data of more than 267 publications downloaded from Dimensions website and using VOSviewer, a freely available software tool for analysing bibliographic data. Via analysis of co-occurrence of the specific terms in the field of COVID-19 ventilation, the trends in research publications were illustrated. The study aims to review the scientific literature of the indoor spread of SARS-CoV-2; clarify the effect of ventilation systems on airborne transmission of the virus; identify the impacts of COVID-19 mitigation measures on the energy consumption of mechanical ventilation systems; define the research gaps and future challenges. This investigation reveals a strong need for more scientific studies in reduction of the transmission risks of the SARS-CoV-2 virus through ventilation systems without compromising buildings’ energy performance. The implications of this study will establish a foundation for engineering control strategies and future energy-targeted investigations for virus transmission reduction and the enhancement of indoor air quality.

Impact of night-time ventilation on indoor air quality in kindergartens and schools

Simo Kilpeläinen — 2022-05-20

In Finland, the public sector employs about 30% of the total employment and the building users include just under a million children and students. Therefore, a good indoor climate in public buildings and the proper use of ventilation systems are important. Night ventilation is commonly used to improve indoor air quality in educational buildings before the premises are used. A typical use has been to turn off the ventilation after using the facilities and restart it about 2 hours before reusing those facilities. Another option is to keep night ventilation running at minimum ventilation. The third option is to use night ventilation intermittently. Although current technology allows ventilation systems to be monitored and controlled using air temperature, carbon dioxide, and presence sensors, it is very common to keep ventilation units running continuously, even if it significantly increases the energy consumption of ventilation. In this study, the pre-started, continuous, and intermittent ventilation strategies were compared by assessing indoor air quality in field measurements during different seasons in 2019 and 2020. The daytime ventilation was kept as usual. Each test period lasted for 2 weeks. Indoor air quality was assessed by measuring TVOC with the metal oxide semiconductor method and microbes by using the quantitative PCR method. Also, CO2, pressure over building envelope, and thermal conditions were measured. The results indicate that the average TVOC concentrations were similar during mornings with all the ventilation strategies. TVOC concentrations were higher during the day than at night. This indicates that the use of the facilities had the greatest effect on TVOC concentrations. The microbial concentration was usually only a few percent of the corresponding outdoor air concentration. The used strategy of night ventilation did not have a systematic effect on indoor microbial concentrations. In general, the natural variation of the measured physical quantities was greater during the test periods than could be observed with different night ventilation operating strategies. The working conditions at the measured buildings were at normal levels. The results show that 2 hours of ventilation before the premises are used is sufficient, and thus continuous ventilation at night is not necessary.

Summer comfort in residential buildings and small offices, using sustainable cooling systems

Margot De Pauw — 2022-05-20

Summer comfort gains attention due to climate change and increasing frequency of heat waves, also in small office buildings and even in residential dwellings. Active cooling systems, using an electric compressor and standard refrigerants, are widely used because of the high cooling power and comfort level they can guarantee. However, given the energy use and refrigerants inherent to those cooling systems, other more sustainable cooling systems should be considered in the first place. To accelerate the acceptance of sustainable cooling systems such as evaporative cooling or free geothermal cooling combined with high temperature emitters, and to ensure a large scale rollout of those systems, a more profound insight is needed into their performance and the provided level of comfort. In the framework of the CORNET project SCoolS the performance of different sustainable cooling systems is evaluated for a set of residential buildings and small offices by means of TRNSYS simulations. To do so, a new future climate file for Belgium has been constructed and comfort classes were defined. A parameter study varying insulation, thermal capacity, window percentage and orientation of the building was performed. Furthermore, the impact of adding passive cooling strategies like solar shading and intensive ventilation by window opening were analyzed. The SCoolS project resulted in a decision support tool for sustainable cooling systems. This article presents the preconditions and results with focus on the non-residential cases. Results show that in office buildings the necessary cooling loads are higher than in dwellings due to more concentrated heat gains during the day and often also more solar gains due to larger window surfaces. However, also in office buildings a combination of passive cooling strategies and sustainable cooling systems (coupled to floor or ceiling cooling) proves to be able to deliver excellent summer comfort.

Mostly dry

Salih Berkay Coskuntuna — 2022-05-20

The current Norwegian building code (TEK 17) requires the new residential buildings to have balanced ventilation with heat recovery, in addition to the strict regulations regarding thermal performance and airtightness of the fabric. During the cold winters in the South-East part of the country, the moisture content in the air outdoors is very low and results in a dry climate indoors as well. This study investigates in-situ the moisture excess indoors (Î”v) in a series of urban residential apartments that have been built according to TEK 17. In particular, air temperature and relative humidity have been measured in six locations/rooms in each of the monitored apartments. Variations in moisture production as well as in ventilation rates have resulted in different moisture excess levels. The findings reveal that the current practice limits moisture excess and have led to an overall reduction of Î”v compared to results found in similar studies performed two decades ago. 90th percentiles of Î”v have been calculated as below 2 g/m3 in all types of rooms, while in bathrooms it has been 2.6 g/m3. The relative humidity (RH) has been respectively below 30%, with bathrooms being the only exception with RH just over this level. The results from a survey among the occupants showed that most of them complain about fatigue, difficulty in concentrating and a head that feels heavy. In addition, dust and too high air temperature have been identified as the main problems of the indoor environment.

A Methodology to assess economical impacts of poor IAQ in office buildings from DALY and SBS induced costs

Louis CONY — 2022-05-20

Indoor air quality is a major issue that concerns everyone. Indeed, human being spend more than 70% of time in indoor environment. Indoor pollutants are responsible for many chronic diseases such as lung cancer or leukaemia, but it also has short-term outcomes, it can cause headache, coughing, running nose, etc, it affects daily concentration and productivity of office workers. Considering the numerous consequences of indoor pollution, a will to quantify induced costs seems logical. In 2003 a study conducted in US concluded a global 41 billion € cost, in France, total cost of indoor pollution for the whole nation was estimated around 19 billion € in 2014. Nonetheless, for an individual person or a whole building, the point of view is not the same, and therefore, integrated costs will differ from those for a nation. This work aims at proposing a methodology to estimate IAQ costs in office buildings, with a function that accounts for pollutants concentration and number of workers. This proposed methodology permits calculation of costs for Disability Adjusted Life Years (DALY). A distinction is made for each individual pollutant cost, accounting for healthcare costs, life years lost and productivity loss. An original part of this work consists in also integrating Sick Building Syndrome (SBS) costs. Preliminary results show a higher cost for SBS compared to DALY.

Numerical analysis of germicidal uv-c lamp air disinfection system

Tunahan Akış — 2022-05-20

In this study, four germicidal UV-C lamps that are in a 600x600 square duct are numerically investigated. Also an UV reactor design is investigated for high resistive microorganisms. Air flow in the duct has 3000 m3/h volumetric flow rate. Simulations are conducted with commercial computational fluid dynamics solver ANSYS-FLUENT. In square duct, Lamps has 75 W UV power and their electrical efficiency depends on UV radiation generation, lamp surface temperature, contact air humidity, lamp working hours, lamp surface pollution. The radiation intensity around the lamps in the channel is evaluated by the using discrete ordinates method depending on the location. After that, the air flow on the lamps are modelled and particle motion simulation is carried out with the DPM model. The amount of UV dose received by these particles is calculated at the duct outlet, and the inactivation ratio for the general coronavirus family is examined. As a result, D90 inactivation performance is achieved in the system. The radiation distributions obtained depending on the UV power and the dose map in the duct outlet section depending on UV power are parametrically examined and presented.

Evaluation of preventive measures in mitigating the risk of airborne infection of COVID-19

Yunus Emre Cetin — 2022-05-20

In this study, a systematic approach for estimating the infection probability under different infection control strategies is presented for several indoor cases. Increased airflow rates, ventilation schemes, air cleaning equipment, disinfection systems, and face masks are considered according to existing guidelines and standards. These strategies are implemented to care facilities, schools, and offices with varying scenarios. Infection probability calculations are conducted based on the widely used Wells-Riley model. The possible variation of the input parameters is evaluated by employing the Monte Carlo approach to increase the representativeness of the findings. Results show that the infection risk reduction of 15 to 99% is possible depending on the measure preferred.

Parametric Modelling Using the Operative Temperature Map for Façade Design of Office Buildings

Yu Chen Lin — 2022-05-20

Controlling incoming solar radiation to a building is one of the main targets of sustainable architecture designers because it decreases HVAC energy consumption and maximizes thermal comfort and usable daylight. The introduction of parametric design has allowed designers to expand their approaches to explore possibilities in façade forms and systems. However, most solar shading designs with complex geometries have been rejected by such building performance simulation software as Energyplus when assessing the calculation of thermal loads. To overcome this limitation, this research introduced a new framework using the Rhinoceros platform to simulate radiant discomfort across spaces with various types of parametric façades. The framework was established based on the ASHRAE55 appendix and improved the longwave MRT calculation by using the Radiance-based pre-processing method. The use of an operative temperature (OT) map was then highlighted as a measure of the combined effect of mean radiant and air temperatures considering the conditions of air velocity and relative humidity in office layouts. Designers were able to compare the hourly intensity of solar radiation passing through a façade between different design cases. Furthermore, the metric of Annual Thermal Discomfort Hours (ATDHs) and the Spatial Thermal Comfort Availability (sTCA) index were proposed for assessing the effect of solar radiation throughout a space. These dynamic indexes were adopted to evaluate different scenarios using the local climate thermal comfort statistics. Eventually, the simulation framework was validated by a field experiment which showed a high accuracy by R2=0.91. By the proposed study, designers can involve critical thermal sensation factors in the early design stage regardless of the complexity of the parametric facades.

Comparing Fast Numerical Methods and Conventional CFD for Mixing Ventilation Flows

Eugene Mamulova — 2022-05-20

Computational fluid dynamics (CFD) provides detailed information on the flow inside a room and can thus be used for detailed analyses of the influence of design variables, such as the placement of ventilation openings. As a result, CFD is well-suited to the optimization of ventilation at room level. However, the high computational cost and level of expertise required for implementation constitute bottlenecks in the engineering sector. In this research, a number of fast numerical techniques such as voxel-based CFD (vCFD) and coarse grid CFD (cCFD) are implemented as alternatives to conventional CFD. The methods are used to predict the velocity field for a generic mixing ventilation case and their accuracy and speed are compared. Reynolds-averaged Navier-Stokes simulations using RNG

The value of user feedback to improve the indoor environment in office

Merlijn Huijbers — 2022-05-20

A healthy, stimulating and comfortable office building positively influences health and the productivity of employees. To determine the indoor environmental quality of a building, indoor environmental parameters in buildings are often measured. While measurements are important, they do not give full insight in the indoor environmental quality of a building and often do not provide complete insight in the causes of potential problems. Since the requirements for a good indoor environment depend on the type of activities that take place in the building and on the preferences of individuals, the feedback of the building occupants should be included in the assessment. Moreover, this contributes to the interpretation of indoor environmental data. We have started collecting data on user feedback, in which building characteristics and the approximate location of users is included, in a systematic way. This makes it possible to easily compare the results of different buildings. The results show among others that the motive to apply the survey appears to be, to a certain extent, a predictive factor in the satisfaction rates: buildings that aim for sustainability- or health certification score highest. The lowest satisfaction rates for indoor environmental parameters are observed for temperature and acoustics. For all parameters, respondents were more satisfied when they perceived control over it. Sharing a workplace with an increasing number of people decreases satisfaction with acoustics and people report a negative impact on concentration. This observation calls for re-evaluation of modern office layouts. In case studies, the results of the questionnaire can be combined with the characteristics of the building to obtain insight in possible risk factors and provide solutions to indoor environmental challenges. Overall, all data collected will be used to define a reference value. By expanding the database, more analyses can be performed to better understand the relation between building characteristics, indoor environment and user satisfaction.

Cooling effects on fatigue recovery during summer sleep

Noriko Umemiya — 2022-05-21

Sleep quality has been difficult to maintain recently, particularly for urban residents. This study investigates effects of cooling use on fatigue recovery during sleep for dwellings and residents with various attributes. Measurements of sleeping room thermal environments and questionnaire surveys were conducted for 188 Osaka apartment residents on 765 nights during four summers. Each resident recorded bedside air temperature and humidity and kept a diary reporting occupation of sleeping rooms, sleep, and cooling use at intervals of 30 min for seven days. Subjective sleep quality by the OSA sleep inventory was recorded every morning. Residents evaluated their dwelling environment and constitution and consciousness. Sunshine, sunlight glare, heating efficiency, outside air clearness in items of dwelling environment and heat tolerance, cold tolerance, circulation and stress in items of constitution were related directly to sleep quality. Data were divided into two categories for each item. The mean outdoor temperature during sleep was higher and lower for over and under 27.3Â°C, which was the median value. Results indicate the following for dwellings with high thermal insulation: a) when outdoor temperatures were higher, fatigue recovery scores were higher for 'not sunny', 'not cooling efficient' and 'not clear outside air' dwellings, with 'low heat tolerance' residents using cooling and higher scores for 'sunny' dwellings and 'good circulation' residents without cooling; b) when outdoor temperatures were lower, fatigue recovery scores were higher for 'cooling efficient' dwellings and 'low stress' residents without cooling. For dwellings with less thermal insulation, results showed the following: a) when outdoor temperatures were higher, fatigue recovery scores were higher for 'poor circulation' residents using cooling and were higher for 'high cold tolerance' residents without cooling; b) when outdoor temperatures were lower, fatigue recovery scores were higher for 'not sunny' dwellings without cooling.

A Comparison of Indoor Pollution using Different Ventilation Methods

Salam Al-Samman — 2022-05-21

One of the essential aspects of healthy buildings is the air quality that people breathe indoors, as it directly impacts their comfort, health, and well-being. Achieving an acceptable indoor air quality (IAQ) has become an essential design objective for newly constructed and renovated buildings as well as for the operational system in existing buildings. The COVID-19 pandemic, which began in 2019, highlighted the need for better IAQ. The quality of indoor air space is not only affected by ambient or external pollution but also by indoor sources and inadequate ventilation. For instance, the build-up of pollutants may differ for the same space due to the ventilation method. This paper uses a case study of an open-plan office in Loughborough, UK, simulated under two ventilation schemes, mechanical ventilation (MV) and natural ventilation (NV), for the same weather file to diagnose and examine the difference in the IAQ. The results of the simulations were compared with monitored data using an IAQ sensor located in the centre of the open-plan office. The air parameters measured were indoor temperature (Ta), relative humidity (RH), carbon dioxide (CO2), formaldehyde (CH2O) and particulate matter (PM2.5). It was found that the average CO2 levels were better by 10% under MV than in NV because higher ventilation rates were achieved during occupied hours. The average PM2.5 was twofold better under NV than MV, as well as CH2O was also better under NV than MV by 26% in the simulated scenarios. The open-plan office was ventilated at all times
under NV; unlike in MV, the air handling unit was only operating during the occupied hours, which contributed to better IAQ. The simulation results for this study revealed that both mechanical and natural ventilation could achieve acceptable IAQ for this specific case study and location. The ventilation control strategy is the manipulator of jeopardising the IAQ in the space.

Review of health and well-being aspects in Green Certification Protocols

Cécile Berquand — 2022-05-21

Over the past decades, the world-leading Green Certification Protocols have been paid increasing attention to health-related aspects of buildings. However, the way and the extent to which green certifications currently account for these aspects vary largely. This paper aims to review and compare four certification protocols, namely LEED v4, BREEAM 2018, WELL v2, and MINERGIE-ECO v1.4, and to provide insights on how aspects related to occupants’ health and well-being and their influencing factors are accounted for and assessed. To that scope, indicators used to assess the users' health and well-being are extracted from each certification and compared. Indicators traditionally used to evaluate IEQ in buildings (thermal, indoor air quality, visual and acoustic) based on international or national standards were found in all certifications. However, the analysis highlights that their assessment and verification stage (e.g., pre- vs. postoccupancy) significantly differs from one label to another. More “advanced” indicators, which are
related to mind, promotion of physical activities, and community engagement, have come to light. While a comprehensive approach to the evaluation of well-being might include a combination of objective (e.g., measurement-based evaluations) and subjective components (e.g., people’s subjective evaluation), the review highlighted that only in one protocol (i.e., WELL), direct feedback from occupants is kept in the loop for further optimization of the building management during operation. Otherwise, indicators are mainly verified through quantitative measurements, reports, or implemented policies.

Development of a human body thermo-physiological model considering the effect of gravity on blood

Hiroya Azemachi — 2022-05-21

In general, blood flow in the human body is significantly impacted by gravity; thereby resulting in thermo-physiological effect. In the present study, we modeled and formulated the effect of gravity on blood flow for each body part, depending on the body posture. We added the gravity term to the segmented two-node model; whereby skin temperature was calculated. This value agrees well with the results of the human subject experiment.

Reproduction of Thermal Plume above Commercial Cooking Gas Stove using CFD Analysis

Takao OSAWA — 2022-05-21

In commercial kitchens, the working environment of cooks deteriorates because of the generation of large amounts of heat and vapor. Ventilation is required to improve the environment, and the accompanying increase in air-conditioning energy becomes an issue. Therefore, a proper ventilation design is required to reduce the risk of contaminated air, thereby deteriorating the indoor environment. When planning ventilation and air conditioning for commercial kitchens, the heat generated by cooking products can be efficiently exhausted to reduce the air conditioning load and maintain good air quality in the workspace. Computational fluid dynamics (CFD) analysis was used to predict the air conditioning load and air quality. It is important to accurately evaluate the heat generated from the cooking equipment and the exhaust collection performance of cooking products. At that time, the accuracy of reproducing the thermal updraft is important, but when the capture efficiency is predicted using the simple gradient diffusion hypothesis model, which is widely used for indoor airflow analysis, the capture efficiency is excess owing to insufficient diffusion. Several studies on the thermal plume on gas stoves have been conducted thus far[1]–[4], and previous studies have clarified that there is a problem in the reproducibility of the production term

Impact of future climate on the performances of ground-source cooling system

Abantika Sengupta — 2022-05-21

Newly constructed and renovated dwellings in Belgium are designed for the current climate context. However, due to the effects of global warming, extreme weather conditions like warmer summers and frequent heatwaves are expected in future climate scenarios. Future climate scenarios are nowadays not taken into consideration during the building and HVAC design process. This paper studies a case study dwelling equipped with a ground-water heat pump coupled with a heat exchanger to provide passive floor cooling, derived from two vertical boreholes with a depth of 100 meters. The aim of this study is to evaluate the impact of future climate scenario on the thermal comfort and the performance of radiant floor cooling system in a Belgian dwelling. Monitoring of the case study building (April-October 2020) and Building Energy Simulations (BES) in Open studio and EnergyPlus were conducted. Future weather files (future mid-term-2050s and future long-term-2090s according to the RCP8.5-scenario) were developed in the framework of IEA EBC Annex 80 Resilient Cooling of Buildings. The performance of the floor cooling system was analysed for four different climate scenarios for Melle, Belgium: typical historical-2010s, 2020 including a heatwave (observational data obtained from RMI), typical future mid-term-2050s and long-term 2090s. The evaluation was based on two parameters, (1) thermal comfort and (2) cooling capacity of the ground heat exchanger. Results demonstrate that in the future (long-term)weather scenario, the current design of the building including the floor cooling system is inadequate to provide a good thermal comfort. Due to the rising indoor and ground temperatures, the maximum cooling capacity will decrease 22,5% in future long-term scenario compared to the typical historical weather scenario. Results also confirm that the occupancy has a big impact on the thermal comfort, especially in thebedrooms. This study also indicates the importance of implementing shading as a good solution to obtain a better thermal comfort in future climate scenarios.

Influence of a portable air cleaner location on the exposure to exhaled contaminants in hospital rooms

José Luis Sánchez-Jiménez — 2022-05-21

Indoor environments with a deficient mechanical ventilation, could increase exposure to exhaled contaminants. This situation is critical in hospital environments such as hospital rooms. In this situation, a portable air cleaner system based on high efficiency air filters maybe a solution by itself or combined with mechanical ventilation systems to reduce the concentration of aerosols in hospital room environments. In this study the influence of the location of a portable air cleaner based on high efficiency air filters on the exposure to exhaled contaminants of a health worker close to a patient lying on a bed was investigated. The experimental setup consists of a hospital room (40.84 m3) with two breathing thermal manikins, BTM. One BTM was lying on the bed (patient) and the other BTM was stand up near the bed (health worker). Each BTM has its own independent breathing system with the capability of performing different breathing flows. Both BTM inhale and exhale through the mouth with a respiration frequency of 17.90 min-1 (inhalation) and 16.43 min-1 (exhalation). Both has minute volume 9.46 (l/min) and tidal volume 0.55 l. The BTM lying on a bed, simulated the source of exhaled contaminants and exhales particles sized 0.57-0.76 μm. A total air flow rate of 150 m3/h (3.67 ACH) was used in all experimental tests. The total air flow rate was generated only by the air cleaner, only by the ventilation system or using a combination of the air cleaner and the ventilation system. The concentration of particles was measured in the inhalation of the standing BTM close to bed, and in other points of the room to analyse the influence of air cleaner location on the exposure to airborne contaminants. The results suggest that the air diffusion plays an important role in the exposure to exhaled contaminants in a hospital room. In these indoor environments, low values in the exposure to exhaled contaminants can be obtained using a combination of a portable air cleaner located near the source of contaminants and the ventilation system or using only 100% air flow rate in the ventilation system.

Importance and design of ventilation for an improved sleep quality

Nur Çobanoğlu — 2022-05-21

Sleep quality, which significantly affects daily life, is also affected by indoor air quality as well as comfort aspects such as noise, temperature, and relative humidity in the sleeping environment. Carbon dioxide concentration is commonly considered as an indicator of indoor air quality, and it has been observed that increasing concentrations increase the number of awakenings resulting in lower sleep quality. In this study, ventilation flow rate is investigated specifically for bedroom and dormitory room dimensions as recommended by different countries to ensure that the carbon dioxide concentration in sleeping spaces is below an upper limit value (1000 ppm). The ventilation flow rate is evaluated by comparison to the methods recommended in ASHRAE standards (Ventilation Rate Procedure-VRP, Indoor Air Quality Procedure-IAQP and Natural Ventilation Procedure-NVP). Although VRP is widely used because a constant flow rate is recommended, which is an advantage due to design simplicity, it has been found to be insufficient for smaller sleeping space volumes and it gives higher values for larger volumes compared to the needed ventilation flow rates recommended by IAQP. Moreover, the fact that the flow rates calculated with VRP and IAQP overlap in a very narrow area shows that the use of VRP values for effective designs is limited. Consequently, we suggest that the system design should be operated with the IAQP and with demand-controlled ventilation, and an approach is offered to designers for direct use in practice.

Predicting indoor air temperatures by calibrating building thermal model with coupled airflow networks

Lili Ji — 2022-05-21

Building models that can accurately predict hourly indoor air temperatures in free-running situations are key to understanding overheating conditions and the resilience of passive cooling strategies under a changing climate. To accurately predict indoor temperatures it is necessary to properly model pressure-driven infiltration and natural ventilation. This can be achieved by coupling a building thermal model to an airflow network model. In this paper, the development of coupled building thermal and airflow network models is described to calibrate building models using field measurements of indoor air temperature. Building models of three types of buildings were configured: long-term care building, primary school and multi-unit social housing. The building models were developed in Design BuilderTM and exported for use in an EnergyPlus simulation package. From information obtained from building surveys, site visits and architecture drawings, building parameters and operation schedules were collected. The unknown parameters, which included envelope thermal properties, shading devices, internal heat gains, envelope air leakage, window and door openings, were then calibrated based on measured values of indoor temperature. Reasonable ranges in value of the unknown parameters were first retrieved from applicable building construction practice documents and building energy standards. Two rounds of calibration were conducted through parametric simulations using the Monte-Carlo sampling method. A sensitivity analysis was also conducted for ranking the importance of all building parameters. The values for indoor air temperature as obtained through simulation were compared with measurements and the RMSE (root mean square error) was calculated for all values. The parameter value combinations corresponding to the minimum RMSE were adopted for the building models. The calibration process ended when the value for RMSE was <1.5â„ƒ. Results showed that the detailed building model was capable of predicting room air temperatures with minimum error levels (0.56â„ƒ â‰¤ RMSE â‰¤ 1.50 Â°C) within the limits of applicable building model calibration standards (MBEÂ±10%, CVRMSE<20%).

Holistic operating room hygiene control for air and surface cleanliness

Kim Hagström — 2022-05-21

Surgical site infections pose a severe risk for patients entering in a surgery. Surgical site infections are caused when microbes are entering to operation wound during surgery. Treatment of surgical site infections is very difficult and expensive, and it is expected that this will be even more difficult in the future due increased number of antibiotic resistant bacteria, such as MRSA, in hospitals.

The microbes may penetrate to patient wound principally through two routes: through air in a form of airborne microbes or by physical contact. In the later case the infection may be caused if an operating person touch a contaminated surface before accessing to the wound. Thus, to minimize surgical site infections it is utmost important to ensure that both operating room air and surfaces are maintained clean both during the operation and between consecutive operations.

The air cleanliness may be ensured with an appropriate ventilation system that is able to react according to surgical schedule also between operations. A throughout surface cleaning by cleaning staff is typically applied at the end of the day and additional cleaning takes place between operations. However, mechanical cleaning may leave some surfaces that are not fully cleaned and especially surfaces that are hard to reach or have complicated structures may remain untouched. To ensure better cleaning result it is possible to back up mechanical cleaning with a radiant disinfection. A blue light-based disinfection method can provide a safe to people cleaning both during operating room downtime and also between operations.

A novel, holistic integrated operating room cleaning system is developed to address simultaneously challenge of both air and surface cleaning. This system is managed by an intelligent control system that can automatically manage both air and surface cleaning processes through seamless interfacing with medical operations management system. Coordinated dimensioning is described to provide simultaneously optimal cleaning result of both airborne and surface bacteria. It is also described how the control system is set to provide cleaning cycles, personnel safety and comfort, and energy efficiency according to operational schedule.

Temperature calibration and Annual performance of cooling for ceiling panels

Seyed Shahabaldin Seyed Salehi — 2022-05-21

In this paper, the annual energy usage and emission efficiency of ceiling panels for cooling were assessed with IDA ICE building performance simulation software. The models were calibrated against measurements carried out in the autumn of 2021 at the nZEB test facility in Tallinn University of Technology. Calibrated models were then used to investigate the energy performance of the systems with annual simulations with the Estonian test reference year and energy simulation input data for office buildings in EN 16798-1:2019. The simulations were conducted on a room model with fixed geometry and boundary conditions. The goal of the control strategy was to maintain a specified operative temperature within the room. The annual cooling energy need of the test room was compared with the same value obtained using an ideal cooler with 100% convective heat emission. Additionally, a single-value performance indicator in the form of an air temperature set-point deviation was obtained for the device and each configuration, as the result of this research, to be used in further hourly, monthly, or annual cooling energy usage calculations. The imperfections in air stratification within the room (temperature gradient), the surface temperature of the panels, and additional temperature deviation from the set-point to achieve the desired operative temperature level are the effective parameters on the performance indicator. Further analysis is needed to determine if room temperature set-point deviation can be applied with varying room geometry, boundary conditions, and cooling control principles.

Thermal conditions and occupant satisfaction in energy retrofitted buildings in Finland

Virpi Leivo — 2022-05-21

In this paper different factors effecting into thermal comfort are compared with results of housing diaries. The data was collected in a project which object was to demonstrate the effects of energy retrofits on IEQ and occupant health. Data from existing 46 multi-family buildings (218 apartments) were collected both before and (usually about one year) after energy retrofits, including various thermal condition and indoor air quality (IAQ) measurements combined with occupant surveys. Measurements were performed during two winter months. The relatively high indoor temperatures observed in apartments before the retrofits indicated overheating. After the retrofits, the average temperatures remained unchanged. The temperature even in the coldest spot, i.e. place where coldest inner surface temperature was detected by thermographic camera or IR-thermometer (usually by the balcony door) was quite high, about +20,3 °C. According to 2-week diaries, considering perceived housing satisfaction, the occupants were quite satisfied with the IAQ. In 11-point scale considering daily perceived disturbance, (0 "not at all" and 10 "intolerably") the average was less than 1 considering indoor temperature, humidity, draught and stuffiness/ poor IAQ. The differences before and after were not statistically significant, except considering stuffiness/poor IAQ, which was reported less disturbing after the retrofits (Mann-Whitney U-test, p=0.001). The indoor thermal conditions were quite good and occupant satisfaction were relatively high even before the energy retrofits and remained about the same after the retrofits.

Review on Overheating Evaluation Methods in National Building Codes in Western Europe

Ramin Rahif — 2022-05-21

Due to the current rate of global warming, overheating in buildings is expected to become more intense and frequent. High indoor temperatures affect occupants’ comfort, productivity, and health. In the last twenty years, the “time-integrated overheating evaluation methods” have been introduced in the standards to describe the extent of overheating over some time and prevent the uncomfortable phenomena. In this paper, we critically review those methods found in the national and regional building codes based on the Energy Performance of Building Directive (EPBD) in Belgium, France, Germany, the UK, and the Netherlands. The methods are analysed according to eight measures including, 1) dependency on comfort model, 2) dependency on comfort categories, 3) symmetric or asymmetric, 4) all hours or occupied hours, 5) normalization to occupied hours, 6) short-term or long-term criteria, 7) single-zone or multi-zone, and 8) comfort-based or heat balance-based. We found that the occupant adaptation is largely neglected in the reviewed building codes except for France. We also found that the building codes in Belgium (Wallonia and Flanders), Germany, the UK, and the Netherlands have only or at least one criterion based on the steady-state heat balance equations. The study outcomes also provide practical recommendations for policymakers to improve the regional and national overheating evaluation methods towards climate change-proof residential buildings.

Impact of Climate Change on the Design of Air Handling Units

Christian Fieberg — 2022-05-21

Air Handling units (AHU) are designed to guarantee a high indoor air quality for any time and outdoor condition all over the year. To do so, the AHU removes particle matter like dust or pollen and adapts the thermophysical properties of air to the desired, seasonal indoor comfort conditions. AHU have a robust design and thus operate for more than fifteen years, sometimes even for decades. An AHU designed today must consider and anticipate the change of user needs as well as outdoor air conditions for the next twenty years. To anticipate the outdoor air condition of coming decades, scientific models exist, which allow the design of peak performance and capacities of the air treatment components. It is most likely, that the ongoing climate change will lead to higher temperatures as well as higher humidity, while the comfort zone of human beings will remain at today’s values. Next to the impact of global warming with average rise of mean air temperature local effects will influence the operation of AHU. On effect investigated here is the steep temperature increase in city centres called urban heat islands. Heating and cooling capacities as well as water consumption for humidification are investigated for a reference AHU for fifteen regional locations in Germany. These regions represent all climate zones within the country. Additionally, the urban heat island effect was investigated for Berlin Alexanderplatz compared a rural area close by. The AHU was chosen to operate in an intensive care unit of a hospital. The set-up leads to 24/7 operation with 8760 hours per year. The article presents the modelling of current and future weather data as well as the unit set up. The calculated hourly performance and capacity parameters for current (reference year 2012) and future weather data (reference year 2045) yield energy consumption and peak loads of the unit for heating, cooling and humidification. The results are displayed by relative comparisons of each performance value.

Visualisation of the airflow pattern of exhaled droplets in a classroom

Yat Long Liu — 2022-05-21

The airborne transmission of SARS-CoV-2 in educational buildings has raised concerns during the current COVID-19 pandemic. In this study, a portable fog generator system was designed and assembled to visualise the airflow pattern of exhaled droplets in a classroom. The system consists of five components: medium, fog generator, buffer, pump, and manikin head. The medium was made of glycol and demineralised water, which produced a fog composed of droplets. The fog was produced with the fog generator and passed through a pipe into the buffer for build-up. After accumulation, the fog is pumped through another pipe and is exhaled out of the mouth of the manikin. Experiments were conducted with the portable fog generator system in a simulated classroom under four different ventilation regimes: no ventilation, natural ventilation (open windows and door), mixing ventilation (600 m3/h), and a combination of natural + mixing ventilation. The experiments were recorded with a camera and analysed to determine the horizontal distance of the path taken by the fog and to measure the time it remained visible after exhalation from the mouth. During the experiments, it could be observed with the naked eye that the glycol droplets linger in the air longer than what was captured in the recordings. Not all the droplets were visible with the camera. The recordings showed that with open windows and door (natural ventilation), the droplets travelled the furthest distance (1.8 m) and stayed the longest in the air, while with mixing and natural ventilation, the droplets travelled the shortest (0.5 m) and stayed the least time in the air. These findings confirm that mechanical mixing ventilation increases the removal of aerosols in the air. It is concluded that the portable fog generator system provides a quick method in understanding the duration and distance droplets can travel after being exhaled.

Modeling the impact of indoor relative humidity on the airborne transmission of several respiratory viruses risk using a modified Wells-Riley model

Amar Aganovic — 2022-05-21

There is good evidence supporting the airborne transmission of many respiratory viruses (measles, influenza A, human rhinovirus and the novel SARS-CoV-2). Relative humidity (RH) is an important factor in understanding airborne transmission as it may impact both airborne survival, inactivation by biological decay, and the gravitational settling of the virus-laden droplets. This study aimed to estimate and compare the impact of indoor relative humidity on the airborne infection risk caused by these viruses using a novel modified version of the Wells-Riley model. To gain insights into the mechanisms by which relative humidity might impact airborne transmission infection risk, we modeled the size distribution and dynamics of airborne viruses emitted from a speaking person in a typical residential setting over a relative humidity (RH) range of 20–80% at a temperature of 20-21 °C. Besides the size transformation of virus-containing droplets due to evaporation and then removal by gravitational settling, the modified model also considers the removal mechanism by ventilation. The direction and magnitude of RH impact depended on the respiratory virus. Measles showed a highly significant RH impact that was as strong as the ventilation impact, as the infection risk was roughly the same at RH of 13.5 % and 6 ACH compared to a higher RH of 70 % and 0.5 ACH. For other viruses, ventilation dominated over RH. In the case of SARS-CoV-2, a very high RH of 83.5% was needed to reduce the infection risk. For rhinovirus, however, the high RH of 80% increased the infection risk. Within the acceptable range of RH of 20-50% indoors, our modeling showed that RH had practically no impact for SARS-CoV-2 and rhinovirus, while the upper RH significantly reduced the infection risk of influenza A at the lowest ventilation rate of 0.5 ACH. This relative impact of RH on infection risk became very weak at higher ventilation rates of 2-6 ACH independently of the virus types (except measles). In conclusion, we showed that in well-ventilated rooms, RH range of 20-50% did not affect the airborne risk of influenza A, SARS-CoV-2, and rhinovirus.

Comparison of three residential ventilation systems in practical operation

Heinrich Huber — 2022-05-21

Three mechanical ventilation systems which are widely used in Swiss apartment buildings were investigated experimentally. The first system is the Central Bidirectional ventilation (CBi), where each dwelling is equipped with an AHU, supply air in bedrooms and extract air in wet rooms. In the second one, the Centralized Unidirectional ventilation (CUn), each dwelling is equipped with a unidirectional ventilation unit, extract air in wet rooms and outdoor air transfer devices in bedrooms. In third system bedrooms and living rooms are equipped with non-ducted Decentralized Ventilation Units (DVU), additional the wet rooms are served by independent extract air fans. In two related projects, the three ventilation systems were investigated in a total of 33 flats in 17 apartment buildings, with a total of 98 supply air rooms and 86 extract air rooms. Multiple products were represented in all systems. The cleanliness of the ventilation systems was assessed visually and the frequency of filter changes was queried. With few exceptions, the hygienic condition was good to satisfactory. In 80% of the CBi systems and DVU's, filters were changed at least once a year. In the CUn systems, this was done only half as often. The air flows were measured in all rooms as found. Then the filters were changed and the ventilation components were cleaned. Finally, all airflows were measured again. The values in the as-found and clean condition were compared with the requirements of the Swiss standards and the imbalance was determined. Overall, the CBi systems proved to work quite stable and robust. With the CBi systems, the supply air flow rate was 6% lower in the as-found condition than after cleaning. For the other two systems, significant reductions in supply air flow rates due to clogged filters and devices were observed (reduction in CUn 17%, in DVU 30%) as well as significant imbalances (as-found CUn 62%, DVU 42% / clean CUn 24%, DVU 21%). One conclusion is that CUn and DVU systems would require significantly more filter changes and cleaning to ensure the same reliable operation conditions as the CBi system. For the system CBi, the specific electric power input was determined and compared with measurements in projects carried out 9 and 12 years earlier. In the sample of the new project, the SPI was about one third lower than in the older projects. This effect is mainly interpreted as product improvements.

Estimating Long-Term Indoor PM2.5 of Outdoor and Indoor Origin using Low-Cost Sensors

Tongling Xia — 2022-05-21

To evaluate the separate impacts on human health and establish indoor control strategies, it is crucial to estimate the contribution of outdoor infiltration and indoor emission to indoor PM2.5 in the built environment. This study applied an algorithm to automatically estimate the long-term time-resolved indoor PM2.5 of outdoor and indoor origin in real apartments with natural ventilation. The inputs for the algorithm were only the time-resolved indoor/outdoor PM2.5 concentrations and occupants’ window actions, which were easily obtained from the low-cost sensors. This study first applied the algorithm in an apartment in Tianjin, China. The indoor/outdoor contribution to the gross indoor exposure and time-resolved infiltration factor were automatically estimated using the algorithm. Due to the year-round monitoring, the probabilistic distribution of the time-resolved PM2.5 infiltration factor and indoor PM2.5 emission can be given over a year. The influence of outdoor PM2.5 data source on the estimated results was compared using the data from the low-cost light-scattering sensor and official monitoring station. Besides, the sensitive parameters to the algorithm were analyzed and their effects on the indoor emission contribution and estimated infiltration factor were investigated. Through the analysis, this study identified the practical applications that robust long-term outdoor PM2.5 monitoring for a specific building can use the data from nearest official monitoring station. This study demonstrated an algorithm for estimating long-term time-resolved indoor PM2.5 of outdoor and indoor origin in real naturally ventilated apartments with only the time-resolved indoor/outdoor PM2.5 concentrations and window behaviors.

Research, standards, practice

Christiane Berger — 2022-05-21

The precise definition of appropriate indoor-environmental conditions for human occupancy is not trivial. Practitioners in the building delivery process frequently rely on applicable standards and guidelines to identify the relevant performance variables and their required values. In this context, recent inquiries have pointed out a number of gaps in our knowledge. Certain aspects of these gaps can be explored in terms of the following three basic questions: i) Are current codes/standards compliance processes limited to meeting formal criteria and minimum requirements, thereby losing sight of the essential task of producing high-quality indoor environments? ii) Do currently deployed standards entail a clear, transparent, and evidence-based logic underneath their recommended or mandated quality requirements? In other words, have the results of scientific research on indoor environment been adequately translated into the language of codes and standards? iii) What is the degree of precision and validity of the indoor-environmental research results? In other words, are we asking the right questions and using the right methods to answer them? To address these questions, the present contribution considers a number of common indoor-environmental quality standards pertaining to thermal and visual comfort, as well as indoor air quality. The outcome of this preliminary appraisal point to gaps in the chain of evidence from research to standards. The results also point to a number of areas in which the scientific research on indoor-environmental quality could benefit from a strategic rethinking of a number of its underlying methodological premises.

Ray-tracing MRT and human thermophysiology model combination for local discomfort prediction

Mohamad Rida — 2022-05-21

Thermal comfort and discomfort based on the local sensation of different body parts have been an important development in thermal comfort studies from the past decade. The human thermophysiology model can be a handy tool to predict local skin and core temperatures, which can then be projected into diverse human’s local and overall thermal sensation and comfort. When local environmental parameters are incorporated in the thermophysiology model, the degree of modeling information improves. One of the important input parameters is the mean radiant temperature. Variations in radiant heat fluxes when shortwave radiation is present in the room can be significant. Combining novel scanning and thermography methods together with ray-tracing simulation, we derived a high-resolution thermal model to fully characterize the variations of radiant heat fluxes experienced by different body parts of a human, both longwave (LW) and shortwave (SW). The shortwave heat flux varied in the range of 0-216 W/m2 throughout the day in the experiments conducted in an office room prototype on 23/02/2021 in Fribourg, Switzerland. The radiant temperature experienced by different body parts varied widely, from 24 °C to 58 °C, due to uneven exposure to solar radiation through a window, while the air temperature remained relatively uniform, as it was controlled by a mechanical system. To demonstrate the importance of combining detailed MRT modeling together with the thermophysiology model, we input detailed MRT distribution into the human thermophysiology model, along with the environmental parameters from the experimental measurements. The calculated skin temperatures were compared with the measured ones using iButtons and thermal sensation and comfort values with the survey results collected from the human subject. A combination of these detailed methods can be used as a design tool to assess local (dis)comfort and thermal perception of an occupant exposed to shortwave radiation and for dynamic shading and personalized comfort systems control strategies.

Towards the integration of air chemistry and building simulation models IAQ assessment

Jeroen van ‘t Ende — 2022-05-21

To limit greenhouse gas emissions, energy efficiency measures are applied at a large scale resulting in buildings becoming more airtight. Indoor environmental quality depends strongly on ventilation rates. Whilst controlled ventilation contributes to the reduced use of fossil fuel, too little ventilation increases the risk of health-damaging concentrations of pollutants in the indoor environment. There are three primary sources for pollutants indoors (1) ventilated outside air, (2) emissions from activities such as cooking and cleaning and (3) longitudinally emitted pollutants from people, building components and furnishings. Some accepted primary pollutants to assess indoor air quality are CO2, Volatile Organic Compounds (VOC) and OH. However, indoor chemistry studies indicate the presence of a great amount of complementary secondary pollutants with potentially health-damaging effects. Secondary pollutants indoors are the result of chemical reactions of pollutants with solar radiation as an energy source and ozone/other oxidants. Little is known about the type of resultant secondary pollutants and their effect on human health. One approach to assess the effect of secondary pollutants on indoor environmental quality is to integrate chemical box models with building simulation models, e.g. computational fluid dynamics. In this contribution, the authors provide an overview of the state of the art in integrated simulation models of air chemistry with building performance. A reduced-order case study will be presented comparing methods and identifying key parameters for indoor air quality, including selected secondary pollutants. Additionally, a conceptual framework is presented for assessing the impact of secondary pollutants on human health.

Energy and comfort in spaces equipped with ascendant airflow

Eusébio Conceição — 2022-05-21

This article presents a numerical study on an impinging jet ventilation system applied in a virtual office with the aim of improving indoor air quality (IAQ) and thermal comfort conditions for its occupants. The study was carried out for winter conditions, also evaluating the thermal energy consumption obtained in the acclimatized space by the proposed ventilation system. The numerical model used is based on the coupling of two numerical models, the Computational Fluid Dynamics to simulate the heat and mass turbulent flow, and the Human Thermal Modelling to evaluate the human and clothing thermal response. A third numerical model, the Building Thermal Modelling, was used to provide some input data required for the two aforementioned models. The evaluation of the thermal comfort is done by the Predicted Percentage of Dissatisfied (PPD) people index. The evaluation of the IAQ is done by the dioxide carbon (CO2) concentration in the breathing zone of occupants. The evaluation of the impinging jet ventilation system is done by the Air Distribution Index (ADI). This study was done in a virtual chamber occupied by four virtual manikins seated around a table. The impinging jet ventilation system has an inlet system based on four ducts located in the corners of the chamber, whose air terminal devices are 0.25 m from the floor, and an outlet system, whose air terminal device is located close to the ceiling central area. This numerical study considered different values of the airflow rate for the impinging jet ventilation system. When the airflow rate increases, the level of IAQ, the level of thermal comfort and the ADI improve. Moreover, results obtained for PPD and CO2 show values within acceptable limits accordingly to the international standards.

Using HAIEQ methodology for holistic analysis of IEQ in modern family houses

Zuzana Veverkova — 2022-05-21

The indoor environment of buildings consists of a set of physical, chemical, and social reactions between users and the building, including phenomena that affect the technical, natural, and medical sciences. To describe and quantify the parameters of the indoor environment of buildings, we commonly use a simplified model, describing and evaluating the individual components of the environment separately - thermal comfort, air quality, acoustics, lighting, electromagnetic and other fields that co-create the final state of the environment. Presented methodology is based on a holistic approach to the integration of information about the building-technical design and interior, heating, cooling, ventilation, lighting, acoustics and electromagnetic, ionic, -static fields, and ionizing radiation, information about the real operation of the evaluated building, based on data from measurements, mathematical model, and questionnaire survey. The output is a set of information expressing whether the object under assessment, in terms of each criterion, is solved at the level of the current state of knowledge or has the potential to improve the quality of the indoor environment, or whether there are significant deficiencies in terms of the quality of the indoor environment. The methodology is applied here to the assessment of two similar modern family houses. The output shows not only the evaluation of IEQ in both houses, but also the potential to improve IEQ in these houses with identification of causes of the potential problems and ways of possible solutions. The case study points out, among other things, interesting differences in the perception of the indoor environment by individual occupants and shows user behaviour in connection with ensuring the indoor environment of their homes.

Perceived and measured indoor environment in educational buildings

Tuomo Ojanen — 2022-05-21

In educational buildings there is strong variation of the user-caused loads on indoor air during the working days. The challenge is to energy efficiently maintain comfortable indoor environment allowing good working and learning conditions for the building users. The objective was to define the main factors having effect on the user experience of indoor environment and to evaluate what range of measured factors are found comfortable in different building user groups. Three educational buildings representing different grades and one day care center were studied at least for a one-year period to find the main factors affecting the perceived indoor environment comfort in these spaces. Altogether 30 selected spaces were monitored, and perceived comfort of the users was collected through a novel real-time feedback system. The users could give their feedback concerning the perceived thermal comfort, humidity, air freshness and cleanliness, odours, lighting, noise and capability to work and learn. The feedback was based on the targets presented in the classification of the indoor environment [1] using Likert-scales [2) in questions. Each feedback of the experienced indoor environment condition had the space and time identification for the comparison with the corresponding monitored values. All the four sites had modern building technology systems. Only a weak correlation could be found between measured temperatures and the primary goal, i.e. good learning and working conditions. However, stronger correlation was found with the lighting, noise/acoustics, air freshness and humidity. With the humidity levels, both too low and too high levels affected the comfort. The effect of the total VOC-level on the comfort depended on the case - only in the day care center it had a strong negative effect. One relevant finding was that there was no difference between the user comfort in a case with full time ventilation compared to a case where the ventilation that was shut down during unoccupied hours to save energy. This paper presents the analysed findings for the measured and feedback data for these cases.

Exploring futures of summer comfort in Dutch households

Lenneke Kuijer — 2022-05-21

Due to climate change, the outdoor temperatures, frequencies, and durations of heatwaves and levels of solar gain in the Netherlands are expected to increase. Based on the European Energy Performance of Building Directive (EPBD) new standards are introduced. However, it is still uncertain how Dutch culture might adapt to this change in climate. The qualitative study underlying this paper addressed this question by focusing on the future of summer comfort in Dutch households. It comprised 21 interviews with diverse households and 10 expert interviews. Results show that while summer night ventilation and shading can prevent or reduce overheating through low-energy means, several cultural and practical barriers stand in the way of their full potential. Practices of shading and summer night ventilation require the active involvement of residents, but clash with their historically formed relation with the sun. A cultural shift is needed to better integrate these practices into household responses to hot weather. Moreover, the study identifies potential for technologies, policies and procedures to support acclimatisation of residents to higher temperatures. This could save energy as well as promote healthy living during hot weather.

Impact of Spatial Distributions of Climate Condition on Building Overheating

Chang Shu — 2022-05-21

In this study, the spatial distribution of the urban climate is evaluated and its impact on indoor overheating conditions is assessed. This was done by modelling the near-field climate of Ottawa and Montreal at 1 km resolution for the summer of 2018 during which an extreme heat event occurred causing nearly 100 deaths in this area. The climate data obtained from Weather Research Forecasting simulations were used for assessing the extent of overheating within a prototype model of a single-detached home using EnergyPlus. The overheating conditions were evaluated using the mean temperature, the number of hours with the temperature above 28°C, and the number of hours cooling from a base temperature of 28°C. A workflow for selecting representative locations within the city for building overheating assessments was established by considering five (5) different quantiles, including 0%, 5%, 50%, 95%, and 100%, of the three calculated overheating metrics over the urban and the rural area. The degree of indoor overheating in homes was quantified and differences in overheating of homes in urban and rural settings as well as those arising within different urban areas (intra-urban) were determined. The most significant intra-urban indoor mean temperature differences of buildings at different locations were 1.8°C for Montreal and 1.6°C for Ottawa. For the number of hours with a temperature above 28°C, the intra-urban difference can be up to 829 hours for both cities. It was also found that the overheating conditions between different locations may be affected by the external air temperature and other variables, such as the local wind speed, which greatly varied the natural ventilation air change rate of buildings. The overheating conditions in buildings of different locations were also compared by analyzing the time-series variation in temperature. It was determined that there always exists a difference between the duration and intensity of indoor overheating in single-family homes of different locations.

Aerosol transmission in rotary wheel heat exchangers

Heinrich Huber — 2022-05-21

Transmission by aerosols is considered the main route of COVID-19 infections indoors. Therefore, limiting air transfer between supply and extract air in ventilation systems is critical. Heat recovery components (HRCs) are used as standard in new ventilation systems. Rotary wheels are very efficient, but have a higher exhaust air transfer ratio (EATR) compared to other types. The fact that the surface of rotary wheels is touched by both supply and exhaust air allows humidity recovery, but also carries a risk of transferring undesirable substances. Aerosols can
deposit on the surface if they come into contact with it. The characteristics of rotary wheels raise the question whether a relevant transfer of aerosols can take place and whether this is different from the EATR. Experimental investigations were carried out with two rotary wheels. The aerosol used was a water-glycol mixture whose properties compare well with human lung aerosols. Particle sensors were installed at all four duct connections of the HRC. In parallel, the EATR was determined with tracer gas. In 16 measurement series, the air velocity, rotor speed and air conditions were varied. The determined aerosol transfer ratio was typically 1 to 2 percentage points below the EATR. The results allow the conclusion that rotary wheels designed and operated according to current standards transfer only a non-relevant small amount of aerosols and thus do not pose an infection risk for COVID-19 in applications such as offices where the frequency of highly infectious individuals is low to moderate. However, aerosol transmission in hygienically relevant quantities is conceivable in poorly designed systems with incorrect pressure ratios and inadequate filters at the same time, but this does not only affect rotary wheels. Although first positive results are available, further investigations are planned. The understanding of aerosol absorption and HRCs surface's properties is to be deepened.

Investigation of the group differences in indoor environmental quality

Zheng Li — 2022-05-21

Based on the field measurements and questionnaires surveys carried out in 22 offices in Harbin, China, the group differences (gender, age, BMI, level of education, location groups) in human comfort for different levels of environmental parameters were investigated. It was found that males, elder subjects (above 25 years old) and the subjects with higher academic degrees have higher comfort votes than other groups. The group differences were larger in a warmer thermal environment and the differences in thermal comfort votes could be larger than 0.5 scale units on the comfort scale among gender, age and level of education groups when the temperature was higher than 26°C in summer or higher than 24°C in winter. For indoor air quality, the differences in comfort votes for air freshness were larger when the CO2 concentration was less than 960 ppm and the difference in comfort votes for air pollution was larger when PM2.5 concentration was higher than 25 μg/m3. For sound comfort, it was found that the subjects near doors had higher sensitivity to the change in sound levels than the subjects at other locations. For light comfort, the higher illuminance could cause larger group differences. This study can be used to better develop comfort systems, especially personal comfort systems.

Thermal Comfort in Old Traditional Shophouses in Ho Chi Minh City, Vietnam

Hung Thanh Dang — 2022-05-21

Cooling is the main requirement for occupant thermal satisfaction in buildings in warm to hot climates across much of the year. This is especially true in naturally ventilated housing, for example, in traditional houses of the tropics, which distinctive passive cooling design strategies including shading, natural ventilation, convective cooling, and light structure optimised to respond to the hot climate and retain the comfortable indoor environment. Thus, energy consumption can be reduced. Those effects are also found in traditional dwellings in Vietnam, in particular, traditional vernacular shophouses in Ho Chi Minh City (HCMC). However, due to the accumulative pressures of changing society, economy, and urban environment in the city, getting thermal comfort indoors has become difficult. The interplay between building, people, management, and comfort is usually complex in the towns preserving the values of the urban and architectural heritage of the city. The quality of traditional vernacular buildings has been degraded while local people desire comfortable living conditions and spatial expansion for the family extension. The paper aims to examine the building and urban characteristics of old traditional shophouses and their comfortable environment in Cho Lon town, HCMC, in which, a large number of traditional dwellings are reported. A case study built in the early 1900s on Trieu Quang Phuc street will be selected for analysing architectural features before and after renovation in 2007. Consequently, the indoor environmental impact due to the change of building features will be investigated. The problems of discomfort, renovation, and preservation will be explained. Then, some recommendations in design will be proposed to help designers/stakeholders renovate traditional shophouses toward achieving comfort, preserving vernacular architecture, saving energy, and getting occupant delight. The research techniques included field visits and numerical analyses to understand long-term environmental performances in such case studies and the effect of proposed design solutions.

Low‐temperature radiant cooling panel for hot and humid climate

Gongsheng Huang — 2022-05-21

In this paper, the heat transfer and thermal environment of air‐layer integrated radiant cooling panel (AiCRCP) was studied experimentally. AiCRCP was proposed in 1963, which was characterized by the use of an infrared‐radiation transparent (IRT) membrane to separate the panel’s radiant cooling surface from its external air‐contact surface. Therefore, the panel’s radiant cooling surface temperature can be reduced to increase the cooling capacity, while its external air‐contact surface, due to the thermal resistance provided by the air layer and the IRT membrane, can be easily maintained at a high temperature to reduce condensation risks. The thermal performance of AiCRCP was investigated using a prototype. Several scenarios were tested to analyze the thermal performance of prototype, and the cooling capacity of the AiCRCP was also investigated according to the thermal performance of the prototype. The results demonstrated that this new type of radiant cooling systems could be more preferable to be implemented in hot and humid climates.

Monitoring the change of indoor environmental conditions of refurbished buildings in Milan

Jacopo Vivian — 2022-05-21

The energy performance gap, i.e. the difference between measured and predicted behaviour of buildings, is one of the main challenges for the building simulation community and it is highly relevant due to the increasing number of building renovations fostered by recent European Directives. In fact, occupants have a high influence on the building energy use for space heating and cooling, especially in refurbished buildings. The user behaviour may be indirectly investigated by monitoring the indoor environmental conditions before and after the refurbishment. However, in the literature there is a lack of monitoring studies that study the impact of user habits on the predicted energy savings for retrofitted buildings. This study contributes to filling this gap by analysing the air temperature and relative humidity monitored in twenty apartments in the city of Milan (Italy) during two consecutive years. Among them, eight were refurbished during the spring/summer period between the two monitored heating seasons. The analysis of the measured data shows that there is a slight increase in the average indoor air temperature of refurbished apartments. Moreover, the application of a simple hygrometric balance show that users are likely to increase air change rate in naturally ventilated buildings after their refurbishment. Finally, Energy Plus simulations of two monitored apartments showed that such changes in the indoor environmental conditions lead to significant variation in the energy needs for space heating.

Effects of daytime cool vs warm exposure on evening thermal perception and thermoregulation

Hannah Pallubinsky — 2022-05-22

Thermal conditions experienced during daytime can be different from those experienced after working hours outdoors or at home. Since most dwellings in Central and Western Europe in the temperate climate zone are naturally ventilated (NV), while public spaces and offices are often air conditioned (AC), a substantial gap between daytime and evening thermal exposure can occur. This thermal gap likely reduces acclimation to the more ‘natural’ climate outdoors and in NV spaces, and therefore may affect thermoregulation and thermal perception. Structural information on how thermal conditions experienced during daytime (e.g. in offices) influence thermal perception and physiology in the evening (at people’s private homes). Therefore, the present study seeks to assess the impact of staying in cool vs. warm environments during daytime working hours on thermal perception and thermophysiology in the evening at home. In this hybrid laboratory and field study, 31 participants (41±17 years, BMI: 24±3 kg/m2) were exposed to a simulated workday in either 21 ˚C (cool) or 28 ˚C (warm) at two separate occasions. Thermal sensation, thermal preference and mean skin temperature were measured at eight timepoints throughout the day (lab) and evening (home) until the following morning. Preliminary results suggest that daytime thermal conditions affect people’s thermal perception and thermophysiology after working hours at home. The effect is most pronounced just after arriving at home and decreases over time. Importantly, our results raise the question whether conditioning of work places solely based on on-site productivity and comfort, but without considering the impact on comfort and well-being during leisure and recovery time at home, is the way to go in the future.

The effect of thermal comfort conditions during work hours on social disconnection

Rania Christoforou — 2022-05-22

Studies have focused on people’s physiological reactions to thermal conditions in indoor environments, neglecting the social consequences that could arise from them. Therefore, there is a gap in literature how these thermal comfort conditions could influence psychosocial aspects of our lives, such as how disconnected we feel from other people around us or how connected we feel with them, especially after being exposed to these conditions for many hours within an occupational context. This study attempted to address this gap in literature by exposing participants to two thermal conditions: a warm condition (28 ˚C) and a cool condition (21 ˚C) in a simulated office environment. The purpose of the study was to observe possible social consequences arising from a day at work under either of those conditions by focusing on social distance and empathy levels. 31 participants were recruited and exposed to both conditions, each condition at a different day (gap between days of at least one day for washout), and were asked to remain in the temperature-controlled environment for eight hours (between 9 a.m. and 5 p.m.). Additionally, they were asked to complete a series of questionnaires, investigating their levels of social disconnection and empathy before and after both testing days. The temperature of the room was monitored throughout the process. The difference observed between pre- and post-measures for both conditions was not significantly different with regards to the feelings of social disconnection, despite the difference in responses observed within the raw data for each condition. In contrast, the difference observed in empathy levels between pre- and post-measures was significantly different between conditions. Individuals exposed to the cool condition reported lower levels of empathy after exposure, while participants exposed to the warm condition exhibited higher empathy levels after exposure. The results suggest that thermal conditions could influence people’s levels of empathy, which could have consequences both within a work environment and in private life. Further research is needed to support this. Implications of these outcomes and recommendations for further research are discussed.

The effects of novel personal comfort systems on thermal comfort and thermophysiology

Wei Luo — 2022-05-22

Allowing more indoor temperature variations may stimulate human physiological thermoregulation and benefit (metabolic) health. However, thermal comfort may be compromised. To investigate possible solutions for balancing thermal comfort and health, we evaluated a novel personal comfort system (PCS) in moderately drifting ambient temperatures (17-25˚C). This PCS targets the most sensitive body parts (hands, underarms and feet in cold and the head in warm conditions), leaving the rest of the body exposed to the ambient dynamic temperature. A cross-over, randomized study was conducted in an office-like laboratory. Eighteen participants (nine male and nine female) were enrolled and performed two scenarios on separate days, one with the PCS and another scenario without the PCS in 17-25˚C. Skin temperature, skin blood flow and thermal perception were measured. The skin temperature is used to indicate thermoregulation as it is an important driver for thermoregulation while skin blood flow indicates vasomotion. The results show that the designed PCS significantly affected the skin temperature of targeted body parts while it had no significant effects on the skin temperature of most non-targeted body parts. Moreover, the skin blood flows of the hands and feet were not affected by the designed PCS in 17-21˚C. On the other hand, the designed PCS significantly changed thermal sensation and improved thermal comfort in cold to neutral conditions (17-23˚C). Therefore, the PCS may maintain the effectiveness of the cold temperature drift on vasomotion and thermoregulation, while significantly improving thermal perceptions. These findings imply that the designed PCS, combined with cold ambient conditions, potentially balances thermal comfort and health in office environments.

Simulating indoor air quality in London hospitals

Shih-Che Hsu — 2022-05-22

Healthcare premises are energy-intensive buildings, and their operation and performance are critical to healthcare delivery and the protection of patients. A key step towards ensuring people’s wellbeing and facilitating recovery is establishing the distributions of indoor air pollutants and temperature, and associated exposures in hospitals. Microenvironment pollutant concentrations are determined by the generation of indoor sources of pollution and the penetration of outdoor air to the indoors. In hospitals, the conditions for air pollution are typically highly controlled to deliver clean environments; however, building ventilation systems may still be subject to harsh external environments that impact on indoor environmental conditions. The aim of this study is to enhance understanding of how building operations and energy efficiency improvements will impact indoor hospital environments whilst reducing potential harmful pollutant exposures and energy demand. To achieve this, the ventilation conditions and corresponding PM2.5 penetration of London hospitals were simulated. The baseline data of building stock physics (building types, construction periods, floor levels, room functions, total floor area and energy performance ratings) for hospitals were aggregated from the building typologies and room functions of the London 3DStock model to analyse the effect of built configurations on air ventilation and pollutant transfer using the CONTAM tool. The simulation results show that recently built or retrofitted hospital buildings are more airtight and energyefficient but also need to carefully maintain intentional ventilation and filtration to ensure adequate air quality conditions to prevent the ingress of outdoor-sourced air pollutants. The simulations also show that COVID operating procedures may greatly increase airflow and a corresponding need for additional air filtration to meet guidance on pollution levels.

Numerical and experimental studies on a hybrid panel element for heating, cooling and ventilation

Lars Schinke — 2022-05-22

The use of surface heating systems will become even more important in the future. On the one hand, the systems can be operated at lower system temperatures and thus represent an energy optimisation. On the other hand, such a system is very well recognised by the user in terms of thermal comfort. In addition, due to the hermetic construction of the buildings, a ventilation system is needed to ensure the necessary supply of fresh air. Considering the Covid-19 pandemic and the reduction of the risk of infection, the importance of fresh air supply is even higher. To meet these requirements, a hybrid panel element was designed and prototyped. The area of application includes new construction as well as the modernisation of residential and commercial buildings. The hybrid panel element combines the advantages of surface heating in winter with cooling in summer and all-season ventilation. The prototypes were used to carry out extensive measurement tests. This made it possible to prove the functionality of the hybrid surface system and to make statements regarding the performance parameters (transferable heat flux via the surface to the room and transferable heat flow to the air). In addition, a parameter study on influencing variables (e.g. material selection, arrangement of air channels) was carried out by means of numerical simulation.

Dynamics of metabolic rate in male individuals due to the meal and regular office activities

Dolaana Khovalyg — 2022-05-22

Metabolic rate is one of the main parameters affecting the thermal balance of the human body and perception of thermal comfort. Typically, we consider a constant value for a specific type of activity (sitting quiet, standing, etc.) despite the time of the day and body built of a person. In this study, we challenged this by undertaking minutely metabolic rate measurements of 3 men in a realistic office layout at 23-27°C operative temperature. The type of activity (sitting and standing quiet work) and their timing were standardized, and the meal ingested (breakfast and lunch) by the participants was also the same. We also measured temporal changes in the heart rate and skin temperature to understand the variation of physiological parameters. A whole day session was split into four 1.5-hour-long sessions, two in the morning (08:30-12:00) and two in the afternoon (13:00-16:30). Thermal comfort between sessions varied within ±1 per ASHRAE seven-point thermal sensation scale, based on the surveys. The metabolic rate varied throughout the day, even for the same activity type, with an apparent effect of the activity performed upon arrival in the morning (e.g., commute to the office) and the thermic effect of food. After a standardized normal-protein lunch, the metabolic rate was about 15% higher for the same activity for all three men. The effect of the prior physical activity on the metabolic rate was smaller than the meal effect. These results revealed that people’s metabolic rate is dynamic, and it can be elevated not only because of physical activity but also by diet-induced thermogenesis. All in all, this work is intended to draw attention to the metabolic rate variation in daily life that has been overlooked so far in the field of ergonomics of the indoor environment and to outline possible future perspectives for smart buildings if personalized metabolism could be known.

Numerical investigation of the transmission route of infectious particles produced by human

Wonseok Oh — 2022-05-22

This study aims to investigate the major factors to influence the respiratory transmission occurred by infectious particles from a human in an indoor environment. Identifying the critical factors of respiratory transmission is important for taking a countermeasure to control its spread. However, it is difficult to track large numbers of infectious particles generated by a human and floating in a room by the experimental method. Therefore, the transient jet airflow by human cough was numerically reproduced, and the trajectories of particles were investigated using the Lagrangian method. In the numerical analysis, two persons sitting and facing each other in a small office room were considered assuming that one person produced infectious particles by cough, and another was exposed to the infection. The trajectory of the dispersed infectious particles was calculated to confirm the proportion of particles that were directly inhaled by a person, attached to the human body surface, adhered to the floor, removed by ventilation, and suspended in the air. Also, the size of particles (1, 5, 10, 20, 40, and 80 μm) produced by the infector, the ventilation rate (6 m3 h−1⋅person−1, equivalent to air changes per hour is 0.5 h−1), and the distance between individuals (0.9 m (3 ft) and 1.8 m (6 ft)) were investigated as an influential major factor to affect the spread of transmission. As a result, it was confirmed that the effects of gravity and inertia increased with larger particles, resulting in a greater rate of adhered particles to the floor. On the other hand, when the size of particles was smaller, they were able to be removed more effectively by increasing the ventilation rate. Further, when the individuals were spaced 1.8 m apart, particles larger than 20 μm had no significant effect on droplet transmission. However, the smaller particles less than 10 μm were highly likely to be inhaled directly and cause droplet transmission. Therefore, for smaller particles less than 10 μm, practical measures to avoid infections such as social distancing is necessary.

Control of the bed thermal environment by a ventilated mattress

Ge Song — 2022-05-22

Bioeffluents emitted from person lying down in bed can be removed by ventilated mattress (VM) before mixing with the room air. VM is designed to suck air through an exhaust opening located near the feet and move the sucked air inside the mattress. The air moves through the whole mattress and is removed to the exhaust or cleaned and discharged back to the room. The VM can change the thermal conditions in the bed micro-environment and provide uncomfortable local cooling of the person in the bed. Therefore, the design of the ventilated mattress is further improved by incorporating local heating. The response of people to the bed thermal environment generated by the mattress was studied at three room air temperatures – 19°C, 23°C and 28°C. 30 human subjects (15 males, 15 females) of age 20 - 29 years old and body mass index in the range 18 - 27 were exposed to the bed thermal environment provided by the VM. The subjects were covered with a thin duvet (2.9 clo) at room temperature 19°C, a double cotton sheet at 23°C and a single cotton sheet was used at 28°C. The subjects were dressed with pajama (short-sleeve shirt, shorts) and underwear. Thermal sensation assessment was collected through standardized questionnaires. The subjects answered questions regarding their whole body thermal sensation and local thermal sensation of separate body parts including face, head, neck, chest, back, arms, hands, thighs, lower legs, and feet. The bed thermal micro-environment was adjusted by the exhaust flow rate through the ventilated mattress and the localized heating depending on the acceptability of the subjects’ thermal sensation collected every 7 minutes. The results show that the applied control of the bed thermal environment increased the acceptability of the whole body thermal sensation votes and the risk of local cold discomfort (especially on the feet and hands) decreased over time. Local heating at the feet will be needed to achieve thermal comfort in room temperatures below 23°C. Local heating incorporated in the VM or separate and the airflow through the mattress can be controlled based on physiological signals of the person’s body.

Patterns and Profiles for understanding the indoor environment and its occupants

Philomena Bluyssen — 2022-05-22

Research has shown that, even though the indoor environmental conditions seem to comply with current guidelines and those conditions seem ‘comfortable’ enough, staying indoors is not good for our health. Reasons for this discrepancy might be the fact that these guidelines are based on single-dose response relationships to prevent negative effects, and that the criteria are determined for an average adult person. A more complex model that accounts for all stressors, both positive and negative, interactions, and preferences and needs of the individual for different scenarios and situations was introduced. To validate this 'new' model, several field studies have been executed to determine patterns of stressors and profiles of people for different scenarios (office workers and their workplace; students and their homes; primary children and their classrooms; employees of outpatient areas in hospitals). The outcome shows that it is possible to determine patterns of stressors for different scenario's based on multivariate regression analysis of a survey of the occupants and the buildings they are occupying. Moreover, people differ in their preferences and needs, and it seems possible to distribute them into clusters based on TwoSteps cluster analysis of preferences and needs acquired through a questionnaire. It is concluded that all possible stressors, negative or positive, are important to consider when studying a certain disease or disorder; and that both profiles of IEQ-clusters and profiles of psychosocial clusters are important parts of this 'complex' model. Next steps should focus on interactions at human and environmental level, and how to account for those in the 'New' model.

Influence of temperature and relative humidity on subjective and objective air quality data in shopping centers

Mahmoud El-Mokadem — 2022-05-22

Germany has 493 shopping centers mostly located in urban cities. According to STASTICA, the number of shopping centers was doubled in the last two decades .For consumers, good indoor air quality (IAQ) is a basic requirement for their shopping experience.
This leads to very high air exchange rates for current operation of HVAC systems in shopping centers. Accordingly, achieving good IAQ in combination with increasing energy efficiency is a main issue for operation. Thus, previous studies were done to evaluate the intensity of shopping product emissions. Trained subject panels evaluated the emissions from retail products by using an intensity comparative scale. In this paper, we analyze the IAQ parameters not only by trained human panel, but also by analyzing the volatile organic compounds (VOC) through objective tests. In a first step, we cluster five different product groups: books, clothing, shoes, coffee and perfume. For these groups, we measure the emissions through a multi VOC sensor system and a trained human panel, depending on two main parameters: temperature and relative humidity. The multi VOC sensor system consists of electrochemical sensors which resistivity changes according to the oxidation reactions that happens on the surface of the sensors at high temperatures. We use the results to investigate the correlation between the intensity of VOCs in respect to the two main parameters. Finally, we used the subjective data along with the objective data, to evaluate the perceived odor intensity and correlate the evaluations with the measured VOC concentrations by the multi VOC sensor system. The evaluation and visualization is done in
principle of statistical data analysis methods such as Friedman test. The results show the potential for the metal oxide semiconductor sensors technology for detection of VOCs and for prediction of perceived intensity based on objective data. Moreover, a product specific regression leads to better prediction results, which shows that different limit values are required for different shop types.
Furthermore, the results show an influence of air temperature and humidity on subjective perception. Thus, for all products investigated, the perceived intensity and the percentage of dissatisfied people increases with rising temperature and relative humidity.

Recognition and Analysis of Air‐conditioner Operation Based on Basic IAQ‐monitoring

Yuanchen Wang — 2022-05-22

Building performance simulations are particularly important for the development of various building energy efficiency strategies. However, the accuracy of these building simulations is often greatly influenced by real occupant behaviour, which leads to deviations between expected and measured performance. The occupant behaviour varies greatly from region to region and even within the same region due to the differences in cultural, climatic and socioeconomic contexts and building characteristics. Therefore, typical occupant behaviours and usage patterns in local buildings should be considered to improve the accuracy of the building simulations. To achieve this purpose, sufficient occupant data is needed to derive these typical behaviours. The cost of data collection and analysis as well as privacy concerns, are the main challenges that must be addressed. This study proposed a simple method to recognise the use of individual split-air-conditioning units based on basic environmental parameters (indoor air temperature, humidity and CO2-concentration) collected by IAQ-sensors in residential buildings. This method was used to analyse the air-conditioning (AC) usage patterns of 98 rooms in 49 residential apartments over one year in Hanoi, Vietnam and validated through comprehensive occupant surveys and on-site measurements. While deriving typical behaviours, deviations from measured room temperature and AC set temperature were observed and discussed in detail. The highlights of the proposed method are as follows: a) The data on AC operation can be determined without labour-intensive manual processing; b) The necessary input data can be collected by using standard IAQ-monitoring instruments, which minimises the cost of data collection and the invasion of occupant privacy; c) Missing information about AC usage can be added to data sets of previous studies for further analysis.

Dynamic evaluation method for assessing households’ thermal sensation using parametric statistical analysis

Hasim Altan — 2022-05-22

Climate change is causing a wide range of impacts, including more frequent and brutal climate events, such as long-term heatwaves while compound effects of extreme weather events can dramatically disrupt indoor thermal conditions, causing increased mortality risks, especially for vulnerable populations with health conditions. Comfort standards do not give clear guidelines to determine the minimum or ideal range of continuous measurements, considering the climate change projections to determine neutral thermal comfort thresholds in 2030s, 2050s and 2080s. The aim of this study is to evaluate the predictive skills of existing long-term thermal comfort indices from the ASHRAE RP-884-II database and to propose new indices based on continuous, in-situ physical environmental measurements and subjective evaluations of social householders in naturally ventilated multi-family houses in the South-eastern Mediterranean basin. A metaanalysis of ASHRAE Global Thermal Comfort Database II showed that the acceptable temperatures extend across a wide range of conditions and vary depending on building type and climate. The results revealed that the Predicted Mean Vote (PMV) is the upper limit in ASHRAE standard-55’s 0.5 clothing value (clo) summer comfort zone stretches all the way to 27°C at 50% relative humidity with air speeds below 0.2 m/s. The results prove that the neutral mid-point of the summer comfort zone is at about 25.5°C regardless the neutral temperature was 28.5°C, and the upper limit of the comfort range in warm indoor air temperature conditions was 31.5°C in the South-eastern Mediterranean region. Our analysis reappraises the scope of applicability of the adaptive comfort standard, assess potential regional differences by considering the detrimental impact of climate change in adaptive thermal comfort responses, and propose mitigation strategies to adaptive comfort theory, the adaptive comfort model and standard and sustainable building design. Finally, we suggest that building operations should better regulate occupant’s psychological behaviour to adapt to warmer indoor conditions by implementing adaptive comfort algorithms to optimise occupants’ thermal comfort against the warming climate conditions. This could lead to improving energy performance of naturally ventilated buildings without sacrificing the occupant comfort.

The conceptualization of exhalation in buildings

Sara Dorregaray-Oyaregui — 2022-05-22

Among the sources of urban air pollution, the gases and airborne particles coming out from residential buildings through normal ventilation outlets are often neglected or poorly understood. Yet, it carries the potential to deeply affect urban air quality, given the universal ubiquity and function of dwellings. The climate emergency declaration approved by the European Parliament on November 28th, 2019, calls for urgent science-based action to curtail it. Our research explores the concept of building exhalation, through research aimed at characterizing and quantifying pollutants leaving residential buildings through their ventilation systems, and how such exhalation impacts urban air quality both outside and, through recapture, inside dwellings. We have set an intensive monitoring system in residential buildings in Pamplona (Spain) to obtain hard data about selected pollutants and their exhalation from buildings, thereby helping define the complete impact of buildings as inhabited units in cities. The verification of this main statement lays on the resolution of several future research questions, which are stated in order to set the boundaries and define the path of this text, developing the concept of exhalation of buildings and the factors involved. To confirm the validity of this hypothesis, an experimental campaign is being carrying out in the city of Pamplona (Spain), which has the goal of quantifying the pollutants exhaled by residential buildings through the ventilation systems. This project is included in the global concern about the unknown pollutants sources and the need of defining the complete impact of buildings as inhabited units in cities.

Human Body Cooling Effect of Local Non‐Isothermal Airflow during Natural Ventilation

Yoshihide Yamamoto — 2022-05-22

In recent years, the natural ventilation system has been attracting attention not only as an energy saving method but also as a countermeasure method for COVID-19 in a building with poor ventilation. However, during natural ventilation, the outside air temperature has a large effect on the indoor environment, which causes fluctuations in the indoor thermal environment. In such a situation, it is effective to positively utilize the indoor airflow generated during natural ventilation as a method of utilizing the advantages of natural ventilation while maintaining the thermal comfort of the room. Most of the airflow generated by natural ventilation is non-isothermal airflow lower than room temperature, but there are few previous studies on non-isothermal airflow compared to isothermal airflow. In addition, in the actual measurement survey conducted by the author, it was found that the whole body does not receive the airflow uniformly during natural ventilation, but often receives the airflow locally such as the upper body. Therefore, the purpose of this paper is to clarify the effect of local non-isothermal airflow generated during natural ventilation to cool the human body. To achieve this goal, we conducted experiments with thermal manikin in a climate chamber. The amount of heat loss for each human body segments was measured under 28 conditions with clothes, room temperature, airflow temperature, and airflow velocity as parameters. As a result, the following findings were obtained.

Office workers’ health during the pandemic lockdown in the Netherlands

Marco Ortiz — 2022-05-22

The worldwide spread of the Coronavirus disease 2019 forced governments to enact different measures to mitigate the infections. Employers and workers had to adjust by shifting a substantial number of jobs to a “work from home” configuration (WFH). On average, people used to spend around 90% of their time indoors, however, this number may have increased during the pandemic. This study aims to investigate the health status of office workers after nine months of a WFH format during the lockdown. A questionnaire was developed to assess the self-reported during the lockdown of office workers. A link to the questionnaire was sent to the employees of ten offices across the Netherlands, in November of 2020. A total of 502 employees responded to the questionnaire, which included diseases suffered during the last twelve months (i.e. asthma, wheezing, rhinitis, hay fever, anxiety, migraine, etc.). Data were analyzed by performing descriptive statistics of the general characteristics and the health status. The results show that during the lockdown and WFH, conditions such as eczema, depression and anxiety are higher than the average prevalence during non-lockdown situations. This may be due to lifestyle changes, such as reduced social interactions, increased distractions, and increased uncertainty.

Control of the bed thermal environment by a ventilated mattress

Rinsa Kunnathummal — 2022-05-22

Thermal comfort affects the sleep quality and well-being of people. The effect of a ventilated mattress (VM with integrated localized heating on providing the necessary thermal conditions for comfort in the bed-microenvironment was studied. The VM has an exhaust opening located under the feet of a lying person. Air is sucked and transported inside the mattress by a small fan connected to the mattress. The benefit of using such a mattress is that it sucks and removes body-emitted bio-effluents, which prevents the pollutants to spread in the room. The air movement inside the mattress provides cooling to the body, which makes the bed micro-environment comfortable during the cooling season but may cause discomfort during the heating season. Therefore, the VM was further developed by implementing local heating. Full-scale experiments were performed in a climate chamber furnished with a single bed equipped with the VM. A full-size thermal manikin was used to simulate a person lying in the bed. The performance of the VM with regard to the provided body heating/cooling was studied at room air temperatures of 19, 23, and 28 ℃. The control of the thermal conditions in the bed-microenvironment was tested when the VM was operating at different airflow rates and local heating power. A reference condition at 23 ℃ without the VM in operation was assumed to provide thermal comfort in the bed. The performance of the VM was evaluated based on a comparison of the body dry heat flux from the segments and the whole body of the thermal manikin obtained with the VM in operation and during the reference condition. The results show that it was possible to achieve the same body heat flux at all studied room temperatures using the VM with localized heating as in the reference condition. The use of the VM combined with localized heating with control based on the individual needs of the user can be an efficient method for providing thermal comfort in a bed at a wide range of room air temperature. Energy can be saved by expanded lower and upper room temperature limits recommended in the standards.

Performance evaluation of balanced heating and cooling with hydronic ceilings and floors

Peter Holzer — 2022-05-22

Climate change increases the necessity of cooling demand in European housing. Systematic solutions in building planning and construction level are essential in order to avoid retrofit air conditioning units’ installations. Implementation of Low Temperature Heating and High Temperature Cooling with embedded water-based systems is gaining ground in large scale residentials projects, being already a standardised practise in the tertiary building sector. In all related systems, heat dissipation and absorption at low temperature difference to room temperature, respectively surface systems, plays a central role. Economically motivated, the combination of cooling with underfloor-heating or also heating with ceiling-cooling systems is evident. This paper analyses challenges related to the capabilities and performance limitations of these applications, concerning thermal comfort limits, potential condensation risks, system energy efficiency and reliable control strategies. The outcomes of static and dynamic heat flux simulations are presented, accompanied with a literature review and conclusions from post occupancy performance evaluation surveys of realised projects. Arguments for utilising the ceiling surface for heating and cooling predominate those of the floor usage. Furthermore, there are convincing results in favour of laying the pipes close to the surface of thermally activated building systems (TABS). Control strategies of these systems in residential building should be very simple and robust. For cooling, best performance is obtained by TABS permanently operating with a constant water flow temperature of 21°C. For heating, very simple zone thermostats, without any features of nocturnal temperature reduction or weekly schedules are sufficient. This works also supports the argument of extending the applicability range of adaptive comfort to buildings with hydronic mass activation as a system cooling.

Futureproofing and scaling machine learning for occupancy prediction

Davor Stjelja — 2022-05-17

An important instrument for achieving smart and high-performance buildings is Machine Learning (ML). A lot of research was done in exploring the ML learning models for various applications in the built environment such as occupancy prediction. Nevertheless, this research focused mostly on analyzing the feasibility and performance of different supervised ML models but have rarely focused on practical applications and scalability of those models. In this study, we are proposing a transfer learning method as a solution to few typical problems with the practical application of ML in buildings. Such problems are scaling a model to another (different) building, collecting ground truth data necessary for training the supervised model and adapting the model when conditions change. The practical application examined in this work is a deep learning model used for predicting room occupancy using indoor air quality (IAQ) IoT sensors. The importance of occupancy prediction has risen in recent times of remote work and is especially important for futureproofing of the built environment. This work proves that it is possible to reduce significantly the need for ground truth data collection for deep learning based occupancy detection model. Additionally, the robustness of the transferred model was tested, where performance stayed on similar level if suitable normalization technique was used.

Development of a multi-criteria decision support tool for sustainable building retrofits

Zaid Romani — 2022-05-17

The existing building stock represents a major challenge for a successful energy transition and achieving zero carbon territories. Several thermal simulation tools have integrated optimization modules for building design and retrofit. However, in these tools there are problems of convergence towards local optimum and the unknown computation time. Indeed, we propose in this research work a tool allowing an optimal choice of building envelope to achieve a sustainable building retrofit by integrating 16 criteria representing the heating energy needs as well as economic and environmental criteria. This tool is based on thermo-aeraulic dynamic simulation using TRNSYS and CONTAM software, the metamodeling based on the design of experiments method and polynomial regression as well as three multicriteria analysis methods such as weighted sums, Min Max and Pareto optimality. Using this tool, the calculation time of the optimization process and the uncertainties of the results are known. Thermal comfort considered as a social criterion is studied in the post-processing. A real-life existing building located in La Rochelle city (France) was chosen as a case study. The results show that the tool developed allows a rapid choice of building envelope technical solutions and to get a compromise between all criteria studied.

Building Assessment Framework from Whole Building to Components

Kamilla Heimar Andersen — 2022-05-21

Well-functioning buildings are crucial for the occupant's health and comfort and for reducing the CO2 emissions from the building sector. A first step in assessing a well-functioning building is to know the current state of the building by, for example, relevant Key Performance Indicators (KPIs). Choosing suitable KPIs to provide a clear message can be challenging; however, beneficial to convey a message to the building actors. This study proposes a Building Assessment Framework to mitigate the latter, consisting of 1) a flexible and novel KPI tool and 2) a step-bystep KPI assessment methodology applicable to all buildings, systems, subsystems, and components. The KPI tool provides the user with a list of KPIs suited for all building systems, and with a separate backend and frontend, it is an easy tool to use. The KPI assessment methodology will guide the user through 5 steps and propose visualization of the chosen KPIs. The step-bystep KPI assessment methodology consists of 5 steps: 1) identification of the selected building resolution level 2) selection of the KPIs for the resolution level 3 + 4) recognition and crossreferencing of necessary sensors 5) choice of benchmarking for the data. The results from the KPI assessment using historical data from a university building located in Denmark demonstrate that the KPI tool is generic, making it applicable to all levels of a building and its systems. The Building
Assessment Framework is flexible; it can be used over short and long periods (instantaneous to several years) and implemented in the building management system. However, it is necessary to be used with historical data, allowing for the real-time performance evaluation of the selected buildings or systems, thereby enabling the users to spot potential abnormal behavior that can lead to faults in the systems.

Fault detection in district heating substations

Jad Al Koussa — 2022-04-24

In district heating or collective heating substations, components can fail or can be inappropriately installed or configured (e.g. valves get broken, heat exchangers get fouled, controller parameters are inappropriately chosen, heat exchanger wrongly connected, internal heating system problems, etc.). The result of these faults is a reduced cooling of the supply water, and as such higher than necessary return temperatures to the grid and higher volume flows (to deliver the same needed power) occur, leading to higher OPEX for all stakeholders. In this work, two approaches for a fault detection routine for district heating substations are introduced, based solely on the energy meter data, with an application on a real-life district heating network in Sweden. The first approach is a cluster-based approach in which substations within the district heating are compared to each other using the overflow method and performance signatures to flag substations with sub-optimal performance compared to other substations in the network. The second method is an instance-based approach using a black-box model to predict the behaviour of the substation using an extended set of input variables and comparing the predictions to the measurements. The results from the two fault detection approaches show that both the cluster-based and the instance-based methods can detect deviating behaviours in DH customer installations.

Digital Twin as energy management tool through IoT and BIM data integration

Alice Schweigkofler — 2022-04-24

Energy Management has gained increasing value in construction market. The spread of Building Information Modelling (BIM) as a methodology for the construction processes organization will bring progressively to a digitalized asset management. Taking a step further, the concept of Digital Twin (DT) is being used to integrate building’s assets with digital technologies to allow real-time analysis, as well as to provide simulation capabilities. DT is expected to have high impact on facilitating sustainable transition through technological developments, according to the European Green Deal mission. Considering operation and maintenance phase in building lifecycle, one of the main problems is about data management. Energy managers and decision-makers use indeed text and spreadsheets to visualize and interpret data. The most recent software solutions in this field focus mostly on the collection of
information in a systematic way and in document and deadlines management. This approach helps operators but makes it difficult to understand the real-time building’s performance. Furthermore, the indoor environmental performance in dynamic use conditions is rarely considered in decision processes. Therefore, a more efficient and less error-prone method is needed for the real-time management of heterogeneous data. A new approach which combines BIM and Internet of Things (IoT) technology could create a shared data environment for crossed management energy aspects. Equipping the building with monitoring systems means that a large amount of collectible data needs to be managed. This paper describes an attempt to represent and visualize sensor data in BIM, in a user-friendly way to support complex decisions as a significantly improved alternative compared to the traditional ways. The proposed framework is tested and verified on the case study of a school building within the project “SINCRO”. In the first part of the paper the use case, devices, and the proposed BIM-IoT integration workflow are described. In the second part the resulting cloud-based DT is explained together with its functionalities applied to a testing period. Feedbacks of the energy manager are collected to demonstrate how real-time performance information can lead to more responsive building management and improve energy efficiency.

Verification of Energy Efficiency Measures in Three Apartment Buildings Using Gaussian Process

Sakari Uusitalo — 2022-05-06

The aim of this work was to examine whether the Gaussian process as a machine learning method is suitable for modelling time series data collected from buildings and whether it can be used to verify the effects of energy efficiency measures on three apartment buildings. A Gaussian process regression model was created using outdoor temperature and time information as inputs including information about the day of the week and the hour of the current day. Correspondingly, the output of the model was to estimate the hourly heating power demand corresponding to these inputs. The results provided by the created model were used as a reference point to verify the effects of energy efficiency measures taken on these residential buildings. The model was trained with 2016 hourly data. The 2017 data was used as test data to evaluate the functionality of the model. The impact assessment of the energy efficiency measures was performed with the measured data of 2019, which was compared with the results given by the model. Based on the performed modelling, it can be stated that using the Gaussian process, the need for hourly power of buildings was reasonably well modelled with even small amount of input variables. It can be assumed that the biggest uncertainty factor in the modelling is related to the domestic hot water consumption and the resulting power requirement. By measuring hot water consumption, modelling accuracy could probably be significantly improved. Based on the reviews, it could also be verified that the energy efficiency measures taken have had an impact on the peak power needs of residential buildings as well as on total energy consumption. For all three buildings, peak power needs appear to have decreased and overall energy consumption is lower than it would have been without the actions taken.

The role of simulation in design of high-performance buildings in Turkey

Gülsu Ulukavak Harputlugil — 2022-05-06

This paper reports on an exploration of the current role of building performance simulation tools in the building and HVAC design process. The focus of the study is on the design of high-performance buildings; our hypothesis is that this is the leading edge of building design, where simulation is most likely to be used to its full potential. The methodology underlying the paper consists of surveys with architects and engineers who carried out the design of a number of high-profile buildings. The paper adds to a small body of work that, over the years, has monitored the actual role of simulation in design. Whilst a lot of work is carried out to improve the role of simulation in design, especially the early phases, the real uptake and role of the technology may not always match our expectations. Critical review of the actual role of simulation tools remains necessary to assess progress and needs for further development. Results show that simulation is regularly used in building design projects, by a range of actors. However, the use of simulation efforts seems to be mainly the confirmation of expectations and the demonstration of meeting targets, especially those that are relevant for certification schemes. Building simulation still has unused potential in terms of selection of design alternatives from extensive search or option spaces. The use of more advanced techniques such as optimization in industry remains relatively low; work on uncertainty and sensitivity is not often undertaken in practice.

Placement and utilization of CO2 measurements in the ventilation and occupancy assessments

Antti Mäkinen — 2022-05-05

Continuous carbon dioxide measurements have typically been used to adjust the demand-based ventilation. With the global COVID-19 pandemic, the use of measurements to ensure the functionality of ventilation and to assess the utilization rate of the space has increased in importance due to the significant impact of air exchange on the spread of the disease via aerosols. The work aimed to examine the spread of carbon dioxide in the room and how the location of the sensors and space users affects the measurement result. In our study, six carbon dioxide sensors were placed in the room that serves as a teaching restaurant. Five sensors were placed in the space itself and one sensor in the exhaust valve. Two meals were arranged, each attended by 10 people. The location of the persons in the space was also monitored. Based on the measurements, it was assessed how the air distribution of the space and the location of the users affected the measurement result of carbon dioxide. It was found that the carbon dioxide content measured close to diners differed from the result measured in the exhaust duct. Because the air in the exhaust duct is mixed with more fresh supply air than in the vicinity of the dining table, it can be thought that the concentration measured in the exhaust duct can indicate better the air variability of the whole space. On the other hand, sensors located closer to the seating area are potentially better positioned from the demand-based ventilation point of view. In the future, it will be necessary to study the issue in more detail for different types of premises and to examine the application of ventilation and space utilization assessment to real-time monitoring of the risk of airborne infectious diseases, for example.

4S3F Diagnostic Bayesian Network method

Ziao Wang — 2022-05-08

In practice, automated energy performance fault diagnosis systems are seldom installed in HVAC systems. The main reason is that a specific Fault Detection and Diagnosis (FDD) setup is time-consuming and expensive because the existing methods are component-specific, not aligned with HVAC design practices, and not fully automated. 4S3F (four symptoms three faults) method, based on system engineering and Diagnostic Bayesian Networks (DBN), was proposed to decrease the gap between the design of HVAC systems for buildings and energy performance diagnosis, and proofs of concepts were tested on diverse parts of the HVAC system of one specific building. In order to test the further applicability potential of the method, it is necessary to expand these tests and to study possible problems arising in practice, like the lack of sensors installed in a specific system or practical difficulties in the construction of the 4S3F Bayesian network by HVAC or control. However, due to the small number of validations carried out on the environment, parameters, and installation process of this method still need further discussion and refinements. In this paper, we investigate how to construct the DBN for the quite generic AHU (Air Handling Unit) of a, with mechanical supply and exhaust, heating and cooling coils, and heat recovery. The paper describes the possible DBN's depending on the technical design and the measurement points. The diverse Bayesians networks are compared, and it is concluded that also, with a limited number of sensors, a diagnostic network can be set up. It is also concluded that step-by-step instructions would be needed to facilitate the work of HVAC engineers when setting up the diagnosis model.

Quality requirements for forecasts in HVAC operation optimization

Thomas Oppelt — 2022-05-12

Optimizing HVAC operation by taking into account predictions for presence, occupancy and inner loads, weather (mainly air temperature and solar irradiation) and thermal behaviour of the room or building can lead to significant energy savings while maintaining thermal comfort for the occupants. However, the quality of forecasts plays an important role for the success: High prediction qualities are essential for achieving the objectives in energy saving and thermal comfort. In the present paper, a simulation study is presented for the example of an office room with up to three occupants. Perfect and real (non-perfect) forecasts are applied for simulating predictive HVAC control in the course of one year. For evaluating the impact of forecast quality, the annual reduction of cooling energy demand and the decrease of thermal comfort are considered. Results show that there is a complex interaction between the different forecasts: The combined quality of all forecasts determines the benefit which can be reached from predictive control. If forecasts are not good enough, thermal comfort decreases significantly compared to perfect forecasts or the reference case without predictive control. Here, especially the forecast of room temperature development (thermal behaviour of the room) was found to be very important. If the forecasts are good, the annual cooling energy demand can be decreased by 19 % in the example while maintaining high thermal comfort.

Real-time diagnostic tool for hygienic and energy parameters of air handling components

Christian Friebe — 2022-05-12

Material and surface properties in air conditioning systems are subject to change, e.g. due to aging, wear or fouling. This is why regular inspections, maintenance or even cleaning measures are mandatory. In the course of quality assurance and the striving for sustainability and energy efficiency, heat- and mass-transferring air conditioning components particularly require permanent metrological monitoring. This goes beyond the conventional data recording in air conditioning components. With the aim of parameter-guided maintenance management, this means a comprehensive monitoring of function and properties based on design and process data. An extensive exchange of information throughout the entire value chain and life cycle (Industry 4.0) also is essential. ILK Dresden has developed a measurement-based diagnostic tool especially for a new type of membrane heat and mass transfer unit for air humidification and sorptive dehumidification. The aim was to process real-time measurement data, considering long-term data, and to apply it for statistical evaluations of changing material parameters, for target-performance comparisons and for risk assessments (e.g. mould growth). The central element of the tool was programmed in Python and is a script for the direct and simultaneous iterative calculation of the ideal reference process and the real characteristic values of the heat and mass transfer process in the membrane heat exchanger. In addition to the thermodynamic calculation, the mould growth risk can be determined with this algorithm. The basis for assessing the mould growth risk is based on a known algorithm comprising different thermodynamic parameters. This method in addition with a detection of special events (load curves, maintenance, faults, etc.), provided by machine learning algorithms is the basis for a process optimisation, quality assurance and sustainable system operation. This presentation will illustrate the technical parameters and the function of the diagnostic tool. Furthermore, the results of the initial test phase under laboratory conditions will be presented as well as an overview of further development steps and potential areas of application.

Examination of life cycle cost in nZEB design

Makiko Ukai — 2022-05-12

In this paper, the feasibility and net present value of life cycle cost (LCC(NPV)) of nZEB under the meteorological conditions of Sapporo, Japan was examined for the model building. The procedure for examining the feasibility of nZEB is as follows. First, a building with envelope and equipment that meets the performance standards of the Japanese Building Energy Conservation Law is set as a reference building. Then the energy performance improvement measures of strengthening the thermal insulation performance, installing energy-saving lighting equipment, improving the efficiency of the heat source, installing the total heat exchanger, a combined heat and power and PV power generation were applied in order of cost effectiveness. And the change in LCC(NPV) was calculated. When all measures except PV power generation and ground source heat pump were adopted, the primary energy consumption was reduced by about 53%, which reached the level of ZEB Ready in Japan's ZEB evaluation. Furthermore, the installation of PV power generation reduced the primary energy consumption to about 25%. This is a nearly ZEB in Japan's ZEB evaluation. The point of becoming the cost optimum (minimum LCC(NPV)) was the level at which the primary energy consumption was about 50%. From this result, it was possible to show the importance of deciding the policy of ZEB while considering energy consumption and LCC(NPV) at the same time.

Study on occupancy presence and heat use in a Norwegian office building

Lu Yan — 2022-05-13

Energy management in buildings is facing a great challenge in Norway due to the COVID-19 pandemic. The largest difference between the pre-pandemic and post-pandemic period is the occupancy pattern in non-residential buildings. However, existing research only discussed the energy use change by longitudinal analysis, and no related research has been conducted based on the measured occupancy data in the post-pandemic period. Therefore, to fill this research gap, a case study with an office building in Trondheim, Norway, was conducted in our work to compare occupancy presence, heat use, and their relationship before and after the pandemic by using data-driven methods. For occupancy presence, on the one hand, occupantsâ€™ presence rate was lower during the post-pandemic period compared with during the pre-pandemic period; on the other hand, occupantsâ€™ absence rate in the lunchtime was decreased during the post-pandemic period compared with during the pre-pandemic period. In addition, two typical occupancy presence patterns in workdays were given in our study, the normal-working day pattern and half-working day pattern. The half-working day occupancy pattern appeared when Norway faced the second wave pandemic and the government implements more restrictive measures. In terms of heat use, the heat use increased markedly in the post-pandemic period, with the largest gap in hourly heat use between pre-pandemic and post-pandemic on workdays increasing around 21%, and increasing around 31% on holidays. The minimum daily heat demand of this building during the post-pandemic period was much higher than that in the pre-pandemic period, with increasing around 46% (on workdays and increasing around 86% on holidays. Regarding to their relationship, a more significant correlation between the daily heat use and the daily maximum occupancy rate during the post-pandemic period was observed compared with that during the pre-pandemic period. This study indicates that the operation of the heating system of the case building may be inefficient in the post-pandemic period, and findings of this study could help engineers to optimize the operation mode of the heating system according to the change of occupancy pattern and achieve better energy-efficiency management in the post-pandemic period for similar type of building.

Detection of the low ∆T syndrome using machine learning models

Anand Thamban — 2022-05-13

The low ∆T syndrome has been a prevalent issue in many chilled water systems, leading to an increase in the pump energy consumption, increase in the chiller energy consumption, and/or failure to meet the cooling loads. It is therefore important to detect the low ∆T syndrome using suitable fault detection and diagnosis methods. One such fault detection method is the data-based approach using machine learning algorithms. The main signs indicating the low ∆T syndrome include a reduced return water temperature from the cooling coil and an increased mass flow rate through the cooling coil. Since the mass flow rate of water is not measured in all chilled water installations, the cooling coil valve position is measured instead. This research aims to compare the performance of different machine learning regression models which predict the return water temperature and the cooling coil valve position, based on the R2 score and root mean square error. The different machine learning algorithms compared for the study include Support Vector Regression, Artificial Neural Network and eXtreme Gradient Boosting. The data required for the analysis was obtained from fault-introduced experiments conducted in an office building. The different fault cases include stuck cooling coil valve at 50%, stuck cooling coil valve at 75%, reduced supply air temperature by 2K and reduced supply air temperature by 1K. The regression models are expected to predict the fault-free data (Xpredicted) of the system such that faulty data (Xactual) can be identified with residuals (Xpredicted – Xactual). The results showed that XGBoost was the best performing algorithm in terms of model accuracy. The XGBoost based prediction models for return water temperature and cooling coil valve position were able to successfully detect anomalies for 3 out of the 4 fault cases.

Assessment of fouling in plate heat exchangers using classification machine learning algorithms

Seyit Ahmet Kuzucanlı — 2022-05-13

Plate heat exchangers (PHE) used in combi-boilers are continuously affected by small particles, both from the heating circuit and other components of the heating system. These particles can accumulate in the heat exchanger and create clogging that affect the performance of the heat exchanger over time by generating a insulating layer. To avoid unexpected blockage and other kinds of mechanical failure caused by unintended particles that originate from the pipeline and other components, it is crucial to design an effective predictive maintenance system for PHE used in the combi-boiler. In this study, the early stage of blockage in a PHE is investigated experimentally to minimize the field failure rate. The data is acquired from an experimental set-up in which just the PHEs are tested. The PHEs with the same plate pattern and different plate numbers are tested using varied flow rate and inlet temperatures as parameters. The overall heat transfer coefficient and fouling resistance are calculated to associate with the functionality of PHE. A comparison study of multi-classification algorithms has been investigated to present an algorithm which gives the most accurate model trained by experimental data. K-folds cross validation are studied using Naïve Bayes, k-nearest neighbours (kNN) and decision tree machine learning algorithms. As a result, the behaviour of overall heat transfer coefficient and fouling resistance in normalized time scale show the expected trends. The attempted models of machine learning algorithms result in Naïve Bayes predicting the classes of test data perfectly and it is followed by decision tree algorithm with an accuracy of 99.3% and kNN algorithm with 96.3%.

Applying MTP-concept for the standardization of building automation and control systems

Michael Krüttgen (M. Eng.) — 2022-05-14

Energy requirements for buildings and their technical systems are becoming stricter and interfaces of technical systems more complex. Today's processes for monitoring applications are inefficient in planning, commissioning and operation due to the high effort involved. This is caused by lack of semantic specifications in existing standards. A basis for their economic implementation is not given. This paper proposes a lifecycle spanning standardization of production related technical building equipment systems. The standardization work is based on the information model of the I4.0 Asset Administration Shell including the application of an online repository. Unified properties are defined from aspects of engineering to operation for technical plants. As a result, monitoring applications are possible with little effort. By applying Module Type Package, an information model is available for manufacturer-neutral and service-oriented plant control. A prototype is used to illustrate the advantages and engineering by means of Module Type Package. Quality assurance as an aspect of the commissioning is supported by the development of digital twins. Finally, the effort in the lifecycle phases of engineering, commissioning and operation is reduced. The standards developed will be published in a NAMUR recommendation.

Deep learning for CFD analysis in built environment applications

Giovanni Calzolari — 2022-05-14

The study and control of the airflow in indoor environment is of great importance since it directly affects human daily life primarily in terms of health and comfort. Fast and accurate airflow predictions are therefore desirable when it comes to built environment applications of inverse design, system control, evaluation, and management. Computational fluid dynamics (CFD) enables detailed predictions through numerical flow simulations and it has been consistently used to simulate airflow motion, heat transfer, and contaminant transport in indoor environment. However, CFD still faces many challenges mainly in terms of computational expensiveness and accuracy. With digitization, recent interest is posed on new data driven tools to either substitute CFD typically for faster predictions or aid the CFD simulation for improved accuracy. More specifically, the abilities of deep learning and artificial neural networks (ANN) as universal non-linear approximator, handling of high dimensionality fields, and computational inexpensiveness are very appealing. This work reviews current deep learning applications in built environment research, which are only limited to surrogate modeling as replacement for expensive CFD simulation. ANN enables fast and sometimes even real-time prediction, but usually at a cost of a degraded accuracy. For this reason, we also critically review what it is done and presented in fluid mechanics simulations research in general, to propose and inform about different techniques other than surrogate modeling for built environment applications and possibly improve the predictions quality as well. More precisely, ANNs can enhance the turbulence model in various way for coupled CFD simulations of higher accuracy, improve the efficiency of POD decompositions methods, leverage crucial physical properties and information with physics informed deep learning modeling, and even unlock new advanced methods for flow analysis such as super-resolution techniques. All these methods are very promising and largely yet to be explored in the built environment scene. Together with promising advancements, deep learning methods come with challenges to overcome, such as the availability of consistent large flow databases, the extrapolation task problem, and over-fitting, etc.

Transient analysis of individual return temperatures in hydronic floor heating systems

Simon Thorsteinsson — 2022-05-14

In this work, we investigate some potential benefits and opportunities gained from monitoring the return temperature of all the circuits in a hydronic floor heating (FH) system. It is for example possible to obtain information on the flow distribution in the FH system. Since flow sensors are relatively expensive, most currently installed FH systems do not provide any information on the flow entering the forward manifold, let alone flows in the individual circuits. This lack of information inhibits analysis of performance and prevents commissioning of more advanced control methods. The approach proposed here, based on temperature sensors mounted on the exterior of the pipes, provides a possible cheap alternative to measuring the flows directly. Further, we argue that this retrofitted solution can be applied to most already installed floor heating systems. The paper contains a description of the retrofit kit and a dynamic model, which is shown to be able to replicate the behaviour of measurements acquired from an actual FH system installed in a single family house, as well as a method for calculating the relative flows. The results show that flow related parameters such as circulation time are, under the right circumstances, directly observable in the data. Overall, we conclude that measuring the individual return temperatures provides valuable information when monitoring the health and performance of a floor heating system.

Customized Neural Network training to predict the highly imbalanced data of domestic hot water usage

Caroline Risoud — 2022-05-14

Despite space heating and cooling, the energy use for hot water production has not changed significantly over time and accounts for a big share in modern, well-insulated buildings. The main challenge of hot water generation lies in the highly stochastic nature of the domestic hot water (DHW) demand. Prediction of DHW demand can significantly help to a more efficient operational strategy in water heating systems. However, the time-series data of hot water demand is very sparse and imbalanced, including many zero demands, which makes it challenging to be predicted properly by Machine Learning methods. This study uses data recorded from a single-family building in South Africa and aims to understand how the customizations of a neural network for learning imbalanced datasets can affect the prediction of hot water demand. Four different customizations (Random over-sampling, Random under-sampling, Weight Relevance-based Combination Strategy, Synthetic Minority Over-sampling Technique for Regression) are compared with the baseline model to predict the hot water demand data. The performance of 9 different simulations is compared and the challenges are outlined. The over-sampling technique shows promising results for practical implementation by over-predicting high peaks by up to 20%, which will guarantee enough hot water production at peak usage.

Interoperability of semantically heterogeneous digital twins through Natural Language Processing methods

Alina Cartus — 2022-05-14

Self-organizing systems represent the next stage in the development of automation technology. For being able to interact with each other in an interoperable manner, it requires a uniform digital representation of the system’s components, in the form of digital twins. In addition, the digital twins must be semantically interoperable in order to realize interoperability without the need for costly engineering in advance. For this purpose, the current research approach focuses on a semantically homogeneous language space. Due to the multitude of actors within an automation network, the agreement on a single semantic standard seems unlikely. Different standards and vendor-specific descriptions of asset information will continue to exist. This paper presents a method extending the homogeneous semantics approach to heterogeneous semantics. For this purpose, a translation mechanism is designed. The mapping of unknown vocabularies to a target vocabulary enables the interactions of semantically heterogeneous digital twins. The mapping is based on methods from the artifcial intelligence domain, specifically machine learning and natural language processing. Semantic attributes (name, definition) as well as further classifying attributes (unit, data type, qualifier, category, submodel element subtype) of the digital twins’ attributes are used therefore. For the mapping of the semantic attributes pre-trained language models on domain specific texts and sentence embeddings are combined. A decision tree classifies the other attributes. Different semantics for submodels of pumps and HVAC systems are used as the evaluation dataset. The combination of the classification of the attributes (decision tree) and the subsequent semantic matching (language model), leads to a significant increase in accuracy compared to previous studies.

Automated performance monitoring of HVAC components by artificial intelligence

Maximilian Both — 2022-05-14

Energy management systems are an important tool for increasing the energy efficiency of buildings. However, the widespread availability of such systems is offset by the high complexity and high costs of implementation, as well as a lack of data. By using standardized digital twins of technical components, these obstacles can be addressed. In combination with homogeneous semantics of the digital twins and standardized interfaces as uniform access points to the information, the implementation of an energy management system can be simplified. If all technical components of a building have the same information technology structure in the form of digital twins and make their standardized information uniformly available for query, simple query rules can be implemented. These enable the automated integration of the information into an energy management system. However, given the large number of different manufacturers of the technical components, agreement on a common semantic standard in particular seems unlikely. Studies show that methods from the field of Natural Language Processing can be used to process heterogeneous semantics. Agreement on a common vocabulary is no longer necessary. Instead, different semantics can be used and matched to a target vocabulary. In order to use semantic matching in Industrie 4.0 environments, it must be provided as an Industrie 4.0 service. The service provides a translation mechanism from a foreign vocabulary to one's own. For this purpose, a standardized Industrie 4.0 interface consisting of two operations is specified. This interface is implemented prototypically as an API to show how it can be used. The specified interface can be used within the digital twins to process heterogeneous semantics and map them to its own. Extending the Industrie 4.0 approach from homogeneous to heterogeneous semantics can help simplifying the implementation of energy management systems. Simpler implementation lowers the barriers to the use of such systems, which in turn can lead to their higher availability.

Automated classification of HVAC systems through analysis of system behaviour

Björn Kämper — 2022-05-15

Technical monitoring applications support the operator in identifying potential improvements in plant operation and deriving recommendations for action. Today, the integration of building automation network data points into technical monitoring applications is complex and costly. The current state of the art is to manually integrate data points into dashboard applications. The decision which data point describes which HVAC component is made by engineers. The basis for the decision is usually identifiers or data point descriptions. An automated recognition of the structural information of the HVAC systems would help to automate the process and make the implementation of a technical monitoring in existing buildings and new buildings easier. One way to determine structural information from data points is to look at the behaviour of an HVAC system type. Common HVAC systems follow known regularities in their construction and behaviour. By analysing the system behaviour, conclusions can be drawn about the heating circuit type (flow temperature controlled, outdoor temperature controlled, etc.). For example, an outdoor temperature-controlled heating circuit will behave differently than a flow temperature controlled heating circuit. Likewise, by analysing the system behaviour, it is possible to predict which data point is assigned to which system component. If two data points increase by a similar value with a short time offset, it is highly probable that they represent the supply and return temperature of a heating circuit. If the flow and return are heated up, it is likely that a pump has started up beforehand, which was represented by a binary switching command. This paper describes an automated method to classify heating circuit data based on system behaviour. BACnet trend objects of heating circuits from different buildings, that are maintained by the building management of the city of Cologne, serve as data sets. This ensures that the developed method can be applied to a wide variety of heating circuit types. The automated classification of a heating circuit is intended to reduce the effort of manually assigning data points to specially created dashboards. Building operators can thus be supported in the creation and implementation of technical monitoring.

Automated energy performance diagnosis of HVAC systems by the 4S3F method

Arie Taal — 2022-05-16

In practice, faults in building installations are seldom noticed because automated systems to diagnose such faults are not common use, despite many proposed methods: they are cumbersome to apply and not matching the way of thinking of HVAC engineers. Additionally, fault diagnosis and energy performance diagnosis are seldom combined, while energy wastage is mostly a consequence of component, sensors or control faults. In this paper new advances on the 4S3F diagnose framework for automated diagnostic of energy waste in HVAC systems are presented. The architecture of HVAC systems can be derived from a process and instrumentation diagram (P&ID) usually set up by HVAC designers. The paper demonstrates how all possible faults and symptoms can be extracted on a very structured way from the P&ID, and classified in 4 types of symptoms (deviations from balance equations, operational states, energy performances or additional information) and 3 types of faults (component, control and model faults). Symptoms and faults are related to each other through Diagnostic Bayesian Networks (DBNs) which work as an expert system. During operation of the HVAC system the data from the BMS is converted to symptoms, which are fed to the DBN. The DBN analyses the symptoms and determines the probability of faults. Generic indicators are proposed for the 4 types of symptoms. Standard DBN models for common components, controls and models are developed and it is demonstrated how to combine them in order to represent the complete HVAC system. Both the symptom and the fault identification parts are tested on historical BMS data of an ATES system including heat pump, boiler, solar panels, and hydronic systems. The energy savings resulting from fault corrections are estimated and amount 25%. Finally, the 4S3F method is extended to hard and soft sensor faults. Sensors are the core of any FDD system and any control system. Automated diagnostic of sensor faults is therefore essential. By considering hard sensors as components and soft sensors as models, they can be integrated into the 4S3F method.

Economic evaluation of properties based on consumption data

Rebekka Benfer — 2022-05-16

The building stock is a major factor for achieving climate targets. By improving existing buildings, their efficiency can be significantly increased, thus reducing emissions. The economic evaluation of consumption data is an essential task for operators of properties in order to identify optimization potential. Here, the costs of heat transfer media, electricity and water are essential. The sole evaluation of building-specific consumption data does not fully allow for cross-building comparisons, since other aspects such as their type of use, size and intensity of use have a significant influence. It is necessary to develop a method that allows this comparison and at the same time can be applied with little effort. This paper presents a method for the economic evaluation of buildings taking into account the type of use, size and intensity of use. The innovative method allows the calculation of annuities for certain consumption categories such as electricity. These are combined into an overall performance indicator (PI) for each building. The scale of the PI is generated dynamically depending on the building data under consideration. Thus, a comparison of different buildings is easily and at the same time individually possible in consideration of the real estate portfolio. The results provide an overview of the potential need for optimization of the building as well as the installed plant technology. The effects of potential optimizations on the economic building performance are calculated based on the annuity method and are also included in the revaluation of the respective building. The method was tested in a study of school buildings in a major city in Germany. The method can be used to compare different combinations of measures and determine the optimal option. As a result, decisions regarding possible building optimization measures can be made transparently and scientifically in the future. This enables a more efficient use of resources.

Effect of measurement resolution on data-based models of thermodynamic behaviour of buildings

Thea Hauge Broholt — 2022-05-16

Multiple studies have investigated and shown a theoretical potential in utilising Model Predictive Control (MPC) of residential heating systems to lower CO2-emissions. However, there are several practical issues in realising this potential. This paper reports on a simulation-based study focused on two of these issues both related to the data-based identification of a black-box state-space model for MPC. First, it is investigated how the measurement resolution of the heating energy consumption affects the precision of the model used for MPC. Second, the resolution analysis is combined with an investigation on whether it is possible to obtain appropriate models using data generated from excitation signals that in theory do not lead to occupant discomfort. The performance of the models was evaluated by combining different resolutions of data with different types of excitation signals. The results show that a Pseudo-Random Binary Sequence signal within a temperature span from 20 to 24 °C, and a time and data resolution of one hour and 0.1 kWh, respectively, of the heat consumption is expedient to ensure black-box models sufficient for MPC purposes.

Interoperable interactions of HVAC components based on a capability ontology

Nicolai Maisch — 2022-05-16

In today's building automation networks, automation functions of installed HVAC components are rigidly predefined. Increasingly hybrid HVAC systems combining different generators (e.g. heat pumps with fossil boilers) and different transmission options pose new challenges for the engineering of automation functions. Rigidly predefined automation functions lead to inflexible operating procedures and high engineering efforts when changing the system environment. The reason for this is the lack of availability of standardised digital twins and the lack of mutual informational explorability of their capabilities to enable interactions between assets without rigid automation functions. Yet if digital twins of technical assets are not semantically described in a uniform way, the semantics of their information and capabilities can be referenced to external ontologies. Semantically describing the capabilities is necessary for self-x interactions between assets to be able to take over joint functions. In the field of HVAC, there is no ontology for capabilities that can be referenced by digital twins of HVAC assets, for example, to semantically characterise their functionality within a power generation system. This paper describes the development of such an ontology and the method used to derive the key terms. The ontology also presents a framework to compose the higher-level functionalities from granular asset functions. This is to ensure that references to the respective functions of individual assets can be used to imply the functionality of their overall system. The usage of the presented ontology by digital twins of HVAC components can serve as a basis for flexible interactions between real world assets. This can help to reduce engineering effort and increase energy efficiency.

Response of low-cost environmental monitors to typical emission events in daycare centers

Hailin Zheng — 2022-05-16

Daycare centers (DCCs), the first program for the social development of young children (0-5 years old), are the most important place for young children besides their homes. Continuous indoor air quality (IAQ) monitoring in DCCs is a means to assess the IAQ and assure a healthy and comfortable environment for infants and toddlers. To date, an extensive array of low-cost air quality monitors (LCMs) is available on the commercial market. Still, only a limited number of these LCMs have been subjected to any research-based evaluation. Furthermore, performance evaluations of low-cost sensors in previous literature are mainly focused on residential emission activities. To the best of our knowledge, there is no research into simulating emission sources related to DCCs scenarios yet. Therefore, this study is aimed to evaluate the response of one type of LCM (2 units) to typical emissions events related to DCCs in detecting the IAQ parameters, that is, particulate matter (PM2.5, PM10), carbon dioxide (CO2), total volatile organic compounds (TVOC), temperature (T), and relative humidity (RH). The LCMs were compared to outcomes from research-grade instruments (RGIs). All the experiments were performed in a climate chamber, where 3 kinds of typical activities (Background test; Arts-and-crafts events; Cleaning events; in a total of 20 events) were simulated by recruited subjects in an indoor climate condition (cool and dry [20±1 ℃ & 40±5% ℃]). The IAQ parameters sensed by the LCM detected the majority of events, despite a difference in the magnitude of responses. Intra-sensor consistency was significantly strong for all IAQ parameters, with a mean coefficient of variation of 4.14%. The LCM particle sensor underestimated the reference concentrations, with a mean RMSE of 12.8 μg/m³ for PM2.5 and 36.5 μg/m³ for PM10. Although TVOC and CO2 sensors reported a weak quantitative response, both had a close correlation with RGIs’ data, with R2 values in the range of 0.8-1.0 and 0.5-1.0, respectively. A good qualitative and quantitative agreement was observed in both T (within 1.1°C) and RH sensor (within 1%). In summary, this study reveals that the LCMs investigated are useful in providing IAQ-based monitoring in the specific application scenarios of daycare centers.

A web-based approach to BMS, BIM and IoT integration

Lasitha Chamari — 2022-05-17

Buildings are complex cyber-physical systems that rely on a combination of heterogeneous systems to provide smooth operation, energy efficiency, occupant comfort, well-being and safety. Building Management Systems (BMS) are central to these operations and generate a huge amount of data. Traditionally operated in a local server in a building, state-of-art BMS solutions are now moving towards the cloud. Internet of Things (IoT) meters and sensors are also increasingly used in buildings and hold tremendous potential for smart building monitoring and control. Another valuable data source is a properly developed and managed Building Information Model (BIM). BIM itself is moving towards Level 3, which is web-based and data-driven, as opposed to the file-based BIM of today. Improving building performance (e.g., energy, comfort, operational cost) relies on data from all the above systems. However, these data usually remain siloed within their own environment and do not provide an opportunity to perform evaluations across multiple systems. Moreover, valuable information about geometry, spatial location, and metadata about the building objects that the BIM models already contain remains unusable for building performance monitoring and reporting tools. Integrating these heterogeneous data sources will provide ample opportunities to improve building performance. Even though some commercial tools enable the integration of sensor data with BIM models, such tools remain largely proprietary and are not compatible with other applications. This study presents a methodology to integrate multiple information sources at their system level in a distributed manner. The Industry Foundation Class (IFC) model of the building is used as the primary source of information for creating a semantic building graph. Since the semantics of BMS sensors was not originally available in the IFC model, the Brick ontology is used to semantically describe BMS sensors in the graph. Sensor data related to spaces in the BIM model is visualized by selecting a space from the 3D model via the web application. Each data stream remains in its optimum environment and the connections are made via an Application Programming Interface (API).

Converge

Peter van den Engel — 2022-05-19

This research gives an overview of the current comfort and energy performance, and
optional future design of highly transparent and lightweight buildings. The transparent Co-
Creation Centre in the Green Village at the TU Delft, has a combination of active and passive
climate control measures. The aim of the research is to show how transparent buildings with
a high glass/floor percentage (here 122 %) perform and how these could be optimized. An
overview of the research project and system integration is presented, with the focus on
energy, comfort and working of the BMS-system. Energy and comfort performances are
measured and simulated. Validation has been executed of daylight, solar heat access, and
thermal performances. A large Phase Change Material (PCM) buffer in the air handling unit
reduces the heating and cooling demand. Making use of passive qualities of the outdoor and
indoor air temperature and solar energy requires a more complex control strategy than
usual. A Model Predictive Control (MPC) strategy has been investigated and can optimize
the energy consumption.

Next generation energy performance assessment methods for EPCs using measured energy data

Jan Verheyen — 2022-05-19

The European Union (EU) aims at net-zero greenhouse gas emissions by 2050, with intermediate quantified targets in 2030. To achieve these long-term objectives, the renovation rates in the building sector should be increased. Therefore, as part of the European Green Deal, the EU has initiated the renovation wave initiative with the ambition to at least double the annual renovation rate and to foster deep renovation. An important tool to raise awareness regarding the building energy performance and the need for renovation is the energy performance of buildings certification (EPC). The EPC was already introduced in the Energy Performance of Buildings Directive (EPBD) in 2002 (2002/91/EC) and is a specific focus of the upcoming revision of the EPBD. Currently, EPCs are mostly based on calculation of theoretical performance. Despite challenges such as correction for actual occupant behaviour and weather conditions, the inclusion of measured data of building energy use may lead to additional benefits, improve the quality, reliability and usability of next-generation EPCs. On the one hand, energy performance indicated based on actual energy use data relates better with non-experts understanding of energy consumption and bills. On the other hand, the actual energy use data can attribute to a more efficient and accurate reflection of the actual energy performance of a building. Such aspects are important for augmenting user acceptance and increasing trust in the market, which in turn may lever renovation rates. This paper presents energy performance indicators based on measured building energy use, either to replace or to supplement EPC indicators currently in use. First, state of the art approaches for energy performance evaluation based on data of measured energy use or related parameters are described. Next, implementation cases are presented that are being developed in the frame of EU H2020 research projects ePANACEA and X-Tendo. Finally, the outline of future work within these projects is given.

Health monitoring

Bram Hajee — 2022-05-19

Multi-sensor networks are becoming more and more popular in order to assess the post
occupancy performance of smart buildings, since they enable continuous monitoring with a high spatial resolution of the occupancy, thermal comfort and indoor air quality. An urgent, but poorly attended topic in this field is the automated detection of sensor anomalies. For example, CO2-sensors can perform auto-calibration, during which the data is not reliable. Without identifying the poor reliability of this data, any analysis based on it may be misleading. Automated detection and diagnosis of multi-sensor anomalies is a challenging task due to the complex characteristics of each data point, the variety of data points and the sheer number of data points. As a result, rule-based algorithms require an extensive expert-based set of rules, which makes them sensitive to threshold values and case specific exceptions. Machine learning algorithms can overcome these issues, but they require datasets with labelled sensor anomalies to do diagnosis. Acquiring such labelled datasets is labour intensive and therefore expensive. In this paper we show the potential of a transition from an unsupervised to a supervised machine learning approach. The unsupervised algorithm is used to detect anomalies and to identify anomaly classes of interest. This enables for labelling such classes efficiently in order to train classifiers for multiple classes of anomalies. The unsupervised and supervised algorithms are employed in parallel during the transition, allowing for the simultaneous detection of unknown anomaly classes and diagnosis of known anomaly classes. The improved performance of the combined classifier compared to unsupervised detection is shown by the precision-recall curve. Though the presented approach is rather generic, it does have some limitations. Because a window-based approach is used, only time windows can be detected as being anomalous, not the exact time. Also, we focus on the detection of sudden anomalies and the approach does not allow for detecting stationary or trend anomalies.

Assessment of energy and business performance of innovative technologies in SMEs

Pieter Proot — 2022-05-19

A major target of the European Green Deal is to raise the 2030 greenhouse gas emission reduction target to 55% compared to 1990. This high ambition includes an increase of the energy performance of buildings and additional generation of renewable energy in all sectors. The tertiary sector, including small and medium sized enterprises (SMEs) such as butchers, small food and non-food shops, restaurants and pubs, is one of the sectors that can contribute to this goal. While large companies in this sector are regularly in the news with iconic projects, for many SME owners “sustainability” is not a key issue. Reasons are that 1) they are not aware of interesting technologies or business cases specific for their company, 2) they are focused on their own business operation and 3) do not always own the building. That is why the Flemish-Dutch TERTS project strives for a transition in energy use and production by 1) demonstrating cutting-edge (innovative) technologies (e.g. circular isolation materials, heat pumps etc.) in SMEs and 2) by guiding these SMEs. This study assesses the impact of different (innovative) technologies specific for the target group ‘barber shops’. A reference building is made by analysing 60 existing barber shops in Flanders. The energy use of the barber shop including the systems is calculated according to DIN V 18599 using the Energieberater 18 599 3D PLUS. Subsequently, the cost benefit of various measures is calculated and compared. This provides us with an approach that not only includes financial measures but also takes metrics into account for CO2 reduction and comfort. Several technologies, which only have moderate financial benefits, reach acceptable overall satisfaction due to the inclusive metrics. This approach is based on modern business model developments and offer SMEs a more qualitative and inclusive way of the return of innovative technologies to support their investment decision making.

Data Integrity Checks for Building Automation and Control Systems

Markus Gwerder — 2022-05-19

Data from building automation and control systems are becoming more and more important, since they are used in a growing number of (novel and established) analytics applications such as fault detection & diagnostics (FDD), smart maintenance and optimization. However, the quality of such data is often poor due to erroneous installation, commissioning, data recording or meta-information. In addition, building automation engineering and service departments usually focus on implementing and maintaining basic control functionality – data acquisition, tagging quality, and analytics do often not take priority. Due to these data quality issues, a first important step in any data analytics operation is to ensure data integrity. One main goal of data integrity checks is to increase data reliability. The paper presents such checks for building automation applications, in particular three different types of plausibility checks for time series data: single signal tests, similarity tests, and reaction tests. Examples using data recorded from real building automation project are presented for each of the three check types, demonstrating the usefulness of these checks. Data integrity checks are set up and configured using the available metadata which – in our case – comes in the form of semantic models that are automatically generated from building automation engineering data. Many data integrity checks have been identified that are potentially of great benefit in practice – both as a stand-alone application or as first part in a data analytics process. The major prerequisite for successful data integrity checking is that the checks can be set up with minimal effort and executed periodically. To achieve a high degree of automation, semantic data is of great importance, because it is through them that the recorded time series are provided with context and meaning. The automatically generated semantic models from building automation engineering proved to be already rich in automation information and are sufficient for many of the checks investigated.

Predict the remaining useful life in HVAC filters using a hybrid strategy

Hossein Alimohammadi — 2022-05-20

This article discusses an engineering prediction-oriented method to monitor and predict the healthy conditions of air filters in heating, ventilation and air conditioning (HVAC) installations in the construction industry. In the literature, many researchers have studied hybrid prognostic methods for monitoring and predicting filter clogging, and experimental studies have been conducted to develop degradation models to demonstrate the mechanism of filter clogging. The common methods usually predict residual useful life based on a physics-based degradation model along with a prognostic model based on measured data. However, if there is not run-to-fail data or it is costly to prepare, another method is needed. The method used in the present work is useful when the data of entire operating period is not available, instead part of the operational range is obtained during the operation of the air handling unit (AHU). The method described in this article includes a combination of physically-based models and acquired operational data. An appropriate health indicator (HI) is calculated based on measurements. Learning algorithms are used to calibrate a carefully designed filter degradation model. The remaining useful life (RUL) of the filter is estimated using the dimensional reduction method, in particular principal component analysis (PCA) technique. The proposed method has been tested on a real air conditioning unit installed in a building located in Tallinn. The results show that the selected degradation model provides the best fit based on the data observed from the field. In addition, using dimensional reduction methods to estimate remaining useful life is feasible for HVAC filter clogging prediction. This is based on a comparison between an acceptable remaining useful life estimate and experimental data. The performance analysis results show that predictive maintenance methods can provide accurate prognostic indications. The application of a hybrid prediction model allows accurate estimation of the characteristics of the remaining useful life of the target component. It should be noted that the use of predictive maintenance strategies in this situation has increased the life of filters in buildings by a significant amount compared to replacement time schedule.

Energy consumption characteristics based on monitored data

Kristina Vassiljeva — 2022-05-19

This study is an initial step for a creation of smart platform for schools in Estonia which will model, analyze, and evaluate the real energy performance of school buildings. Energy meters provide electricity consumption data which can be used to understand energy usage patterns and finally improve building energy management. First, data preparation is made. On the following step hierarchical clustering is applied to identify the outliers of weekly electricity load profiles. Finally, daily electrical load patters are clustered and similar profiles are grouped using K-means centroids.

Reinforcement learning for occupant-centric operation of residential energy system

Amirreza Heidari — 2022-05-20

Occupant behavior is a highly stochastic phenomenon, which is known as a key challenge for the optimal control of residential energy systems. With the increasing share of renewable energy in the building sector, the volatile nature of renewable energy is also another key challenge for optimal control. It is challenging and time-consuming to develop a rule-based or model-based control algorithm that can properly take into account these stochastic parameters and ensure an optimal operation. Rather, a learning ability can be provided for the controller to learn these parameters in each specific house, without the need for any model. This research aims to develop a model-free control framework, based on Reinforcement Learning, which takes into account the stochastic occupants' behavior and PV power production and tries to minimize energy use while ensuring occupants' comfort and water hygiene. This research, for the first time, integrates a model of Legionella growth to ensure that energy saving is not with the cost of occupants' health. Hot water use data of three different residential houses are measured to evaluate the performance of the proposed framework on realistic occupants' behavior. The measurement campaign was during the COVID-19 pandemic, which would further highlight the adaptability of the Reinforcement Learning framework to the unusual situation when the prediction of occupants' behavior is even more challenging. Results indicate that the proposed framework can successfully learn and predict occupants' behavior and PV power production, and significantly reduce energy use without violating comfort and hygiene aspects.

Digital system interaction test

Rebekka Benfer — 2022-05-20

Technical building systems are becoming increasingly complex, more diverse and more strongly networked through building automation systems. As a result, resource-saving and energy-efficient operation can be achieved. In practice, however, faults and deficiencies often exist in the systems that prevent the most efficient plant operation possible. The deficiencies include, for example, an incorrect parameterization of systems, controller settings that are not matched and optimized to the system, and inadequate cross-plant automation functions. In practice, various methods are used to identify these deficiencies and ensure the quality of automation functions. These include visual inspection of the plant to be tested by certified testing experts. In addition, applications of monitoring and commissioning as well as user-oriented test sequences can be used for fault detection and quality assurance of automation functions. However, the aforementioned procedures are associated with time and configuration effort, which result in costs for their usage and configuration. In addition, they are not based on any generally valid and standardized procedure. Based on these findings, this paper describes the conceptual development of digital system interaction tests that can be used to check different cross-plant automation functions. On the one hand, the focus of the process is on implementing the test procedure as automatically as possible. On the other hand, it should be standardized and generally applicable. Due to the low configuration effort, time and costs for the use of the procedure can be reduced. The standardization of the test procedure enables the application to be used in different technical building systems and creates a transparent form of testing.

Time Series Building Energy Systems Data Imputation

Adrien Lucbert — 2022-05-20

Completeness of data is vital for the decision making and forecasting on Building Management
Systems (BMS) as missing data can result in biased decision making down the line. This study creates a guideline for imputing the gaps in BMS datasets by comparing four methods: K Nearest Neighbour algorithm (KNN), Recurrent Neural Network (RNN), Hot Deck (HD) and Last Observation Carried Forward (LOCF). The guideline contains the best method per gap size and scales of measurement. The four selected methods are from various backgrounds and are tested on a real BMS and meteorological dataset. The focus of this paper is not to impute every cell as accurately as possible but to impute trends back into the missing data. The performance is characterised by a set of criteria in order to allow the user to choose the imputation method best suited for its needs. The criteria are: Variance Error (VE) and Root Mean Squared Error (RMSE). VE has been given more weight as its ability to evaluate the imputed trend is better than RMSE. From preliminary results, it was concluded that the best K‐values for KNN are 5 for the smallest gap and 100 for the larger gaps. Using a genetic algorithm the best RNN architecture for the purpose of this paper was determined to be Gated Recurrent Units (GRU). The comparison was performed using a different training dataset than the imputation dataset. The results show no consistent link between the difference in Kurtosis or Skewness and imputation performance. The results of the experiment concluded that RNN is best for interval data and HD is best for both nominal and ratio data. There was no single method that was best for all gap sizes as it was dependent on the data to be imputed.

Practical experiences from the implementation of extensive sensoring in a modern building

Ádám Bognár — 2022-05-20

The extensive use of sensors is quickly becoming a standard feature of modern new buildings. Apart from the use of regular Building Management System (BMS) data, we see the addition of sensors that monitor in more detail the indoor environmental quality and the use and performance of innovative (and local) system solutions. This is also combined with integrated energy solutions at supra-building level. The assumption is that all these data are valuable to arrive at buildings that can optimize their operation towards indoor environmental and other sustainable performance indicators. In this research, data from a large modern building that combines office and educational rooms, features an innovative façade design and is connected to an aquifer thermal energy storage are considered. In order to perform detailed analyses, several sensor and data related issues had to be resolved first. In this paper we provide a procedure for structuring the data as was available for this specific building, originating from different sources. The outcomes provide a practical basis for other buildings to assess the correctness and quality of the sensor data and the analysis potential. An example of an analysis is presented. In addition, the paper demonstrates how the obtained measurement data can be used to calibrate a simulation model that is employed to analyse the ventilative cooling potential of the innovative façade in comparison to shading.

Co-benefits of building automation and control systems

Federico Garzia — 2022-05-21

The more and more widespread availability and implementation of building automation and control systems (BACS) is revealing how building monitoring, control, and real-time data, can support building users' well-being, providing additional co-benefits, besides the positive energetic impacts. Therefore, these technologies will play an important role in the transition towards a smart built environment, reducing energy consumption, enhancing comfort and interacting with a smart grid and building users. The Standard EN15232 with the BAC factor method introduces smart control efficiency classes and provides quantitative data for estimating the energy savings associated with the installation of smart controls. Although this method is not very detailed, it aims to provide a rough estimation in the early design stages. Assessment methods for BACS (such as the European Smart Readiness Indicator, the French SBA' Ready to Service label's) also stress the importance of non-energetic impacts of BACS. At present, these methods mostly rely on qualitative assessments or use ordinal scores, since investigation on non-energetic benefits and quantitative data are largely lacking. This paper analyses the multiple co-benefits of smart controls in office buildings in greater detail. By means of data reported in literature and building simulations, the most important co-benefits are identified and to the extent possible also quantified. A contemporary office building is used as case study to apply and demonstrate the proposed analysis framework.

A novel machine learning approach to predict short- term energy load for future low-temperature district heating

Thomas Ohlson Timoudas — 2022-05-21

In this work, we develop machine learning methods to forecast the day-ahead heating energy demand of district heating (DH) end-users in hourly resolution, using existing metering data for DH end-users and weather data. The focus of the study is a detailed analysis of the accuracy levels of short-term load prediction methods. In particular, accuracy levels are quantified for Artificial Neural Network (ANN) models with variations in the input parameters. The importance of historical data is investigated – in particular the importance of including historical hourly heating loads as input to the forecasting model. Additionally, the impact of different lengths of the historical input data is studied. Our methods are evaluated and validated using metering data from a live use-case in a Scandinavian environment, collected from 20 DH-supplied nursing homes through the years of 2016 to 2019. This study demonstrates that, although there is a strong linear relationship between outdoor temperature and heating load, it is still important to include historical heating loads as an input for prediction of future heating loads. Furthermore, the results show that it is important to include historical data from at least the preceding 24 hours, but suggest diminishing returns of including data much further back than that. The resulting models demonstrate the practical feasibility of such prediction models in a live use-case.

An early prototype for fault detection and diagnosis of Air-Handling Units

Shobhit Chitkara — 2022-05-21

The built environment is responsible for nearly 35% of energy consumption and is undergoing a digital transformation. Up to 30% of energy is consumed inefficiently due to inadequate setup and/or incomplete utilization of available data. An efficient fault detection and diagnosis (FDD) strategy for air handling units is key to addressing this gap. Even though numerous FDD approaches have been published, real-world applications are far more complex and rarely discussed. This paper deals with FDD tool prototyping and integration aspects and discusses its development for air handling units deployed at 2 case-study buildings located in the Netherlands. The design and development of the FDD tool follows a structured 4 step process. Firstly, literature research is utilized to narrow the design space and establish a complete use case for developing the FDD tool. Secondly, the developed use case is handled utilizing a data-driven strategy to generate fault symptoms using a state-of-the-art extreme gradient boosting algorithm (XGBoost). Thirdly, the detected faults are isolated with a diagnostic Bayesian network. This way the fault detection and diagnosis aspects are separately handled. Lastly, integration of the prototyped tool with a commercially operated continuous monitoring system, currently being utilized to monitor 400 buildings, is discussed. Upon experimental validation, diagnosis specificity exceeding 90% is realized. It is further observed that the prototyped FDD tool could prevent up to 33% of chiller consumed energy. Moreover, the results presented will contribute to the adoption and deployment of AI-based FDD strategies in commercial applications.

Interoperability as a driver or barrier of smart building technologies?

Stijn Verbeke — 2022-05-21

Smart building solutions are a strong leverage for increased energy efficiency in buildings, improved quality of life for occupants and added value for work performance. However, the degree of interoperability of technical building systems (and analysis / software tools that use data from these systems) can be a limiting factor affecting the smart services and impacts that can be delivered within a building since several ways of representing components and systems exist and inherently means a comprehensive knowledge not easily reachable. Interoperability is essential for allowing technical building systems to interact with the energy grids, can avoid duplication of efforts and is desirable in the light of future upgrades of the building. On the downside, it can increase the risk for malfunctioning and introduce cybersecurity and liability risks. This paper presents an overview of the various layers of interoperability in smart buildings and related standards and ontologies. Experts from industry and academia were surveyed and mapped the barriers and drivers related to interoperability of smart building systems, followed by further prioritisation of key actions to strengthen the market uptake of smart building technologies.

Floor heating pre-on/off parameters based on Model Predictive Control feature extrapolation

Ettore Zanetti — 2022-05-21

Floor heating systems are typically characterized by a relatively high thermal inertia, thus they react slowly to setpoint changes. When the system turns on, an under-heating period could occur for a relative long period, vice versa when the setpoint is decreased the floor thermal inertia could lead to overheating. In residential applications, the users try to avoid these discomfort problems by using a constant setpoint, higher than the setback. In this way the average energy consumption as well as the userâ€™s bill increases. A smarter solution to mitigate this problem is to include a pre-on period parameter, so that the system will turn on a certain time before the increase in setpoint to avoid the under-heating period and a pre-off period so that it will switch off before overheating. Predictive controllers can be a solution to compensate the slow response of the radiant floor system. However, besides the need for more data, the computational power goes beyond what is available in heating systems micro controllers for residential cases. To avoid these issues, in this paper the optimal control trajectory obtained using a Model Predictive Control (MPC) approach is used to identify the pre-on and pre-off
parameters to be periodically updated in the micro controller (e.g. monthly). A simulation work was carried out to compare the performance between a baseline Rule Based Controller (RBC), an improved RBC and a MPC in terms of comfort and energy use. The result is a reduction from an average of 1.1Â°C to 0.2Â°C for the worst thermal zone meaning 80% reduction of the discomfort with respect to the baseline and a slight increase of the electrical consumption of the heat pump (less than 5%).

Increasing the Energy Flexibility of Buildings controlled by Model Predictive Control

Christian Karczewski — 2022-05-21

The growth of renewable energy sources in the electricity grid and the electrification of heat generation in buildings using heat pumps increase the necessity of flexible consumers who can change their electric load. Operating the building in a flexible way means that the building’s load is adjusted, e.g. to an electricity price. Model Predictive Control (MPC) is seen as a key algorithm in building energy management systems to provide the requested flexibility. In most studies covering energy flexible buildings, the load shifting is achieved by an economic MPC that uses an objective function, which aims to minimize the building’s operating costs, assuming
a variable electricity tariff. However, the most economic operating point corresponds in the heating period to the lower limit and in the cooling period to the upper limit of the thermal comfort band. As a result, the available flexibility that a building can offer is limited. In this work, a novel formulation of the control law, aiming to increase the energy flexibility of buildings, is derived and evaluated. From the current operating point, the heat pump’s load for reaching the upper and lower comfort limit in the building is estimated. These two demand curves are used to determine a control signal that balances the trade-off between thermal comfort and operating costs whilst increasing the building’s available flexibility. The proposed control strategy is evaluated on lumped-element models of German single-family houses, which are equipped with heat pumps, using the day-ahead electricity price as an incentive. Different indicators (e.g. power shifting capability and flexibility factor) are evaluated showing increased flexibility but also
increased operating costs compared to classical economic MPC. Providing flexibility to the grid through demand response will require to operate the building at a point that is not cost-optimal. Higher operating costs on the building side would need future electricity contracts to include a flexibility refund in order to increase the building operator’s willingness to provide flexibility.

Mapping of an abstract PLC information model into different fields of application

Björn Kämper — 2022-05-21

Collaborative working in BIM applications requires that different users have a common understanding of components such as pumps, valves or pipes. This common understanding is achieved by describing components through information models composed of defined properties. The different roles involved in the planning process (manufacturer, planner, operator) have different views of components. To avoid that different roles, develop specific information models, it makes sense to develop common information models describing the whole product life cycle (PLC). Besides BIM applications, information modeling of components is an area that is also used in industrial applications. An abstract modeling approach helps to ensure that information models are not developed in a technology-specific way.
This paper describes how a manufacturer- and technology-independent PLC information model for pumps and vacuum pumps was developed and subsequently integrated into industrial services and building services information standards. The integration is intended to serve as the basis for a continuous flow of information over the life cycle of pumps in building services applications.
The challenges of this work include mapping an abstract modeling concept to existing semantics in different technologies and not creating duplicates in existing data standards.

De-Risking Building Performance Investments by Certified Quality Management Services (QUEST)

Ivo Martinac — 2022-05-21

Non-compliance with predicted, contracted or otherwise required aspects and levels of building performance can result in a wide range of problems. This includes sub-par quality of building functions and services, unsatisfactory indoor environmental quality, disappointing end-user experience, excessive energy use, excessive environmental emissions, increased maintenance and operational costs, operational start-up loss, component and system faults, difficulties in achieving targeted building certification levels, mismatch with business case, lack of adaptability and flexibility, expenses changed from capital expenditure to operational expenditure, facility not meeting regulatory requirements, as well as increased risk and liability. This is often referred to as the building performance gap.
Compliance with ambitious levels of resource efficiency, energy performance, decarbonisation and circularity goals, as well as other key objectives defined by the EU Taxonomy for sustainable activities will be essential criteria for the sustained future success of businesses throughout the building sector.
Building performance investments, including investments in energy efficiency, can generate significant environmental benefits, while also increasing financial returns. The key goal of the EU-funded project Quality Management Investments for Energy Efficiency (QUEST) is to promote private investments and financing in quality management services to ensure sustainability and energy-efficiency of building projects. To that end, a toolkit, with the QUEST data engine as the core data source, has been developed that will enable financial institutions to determine key factors influencing risk in the design, development and operations of energy-efficiency and sustainability projects, as well as the impact of quality management services. This will allow them to reduce risk, increase financial performance and therefore significantly increase investment volumes.

Control device for pumping one-pipe hydronic systems

Jiří Dostál — 2022-05-21

The article presents the development and algorithms behind an active control device for pumping one-pipe (or primary-secondary pumping) systems. The main feature of such a system is the series connection of thermal loads/sources and a small pump by each load/source, as opposed to classical two-pipe systems with a parallel connection and throttling valves. Our main contribution is an integration of all necessary components into one device and the ability to infer mass flow in a secondary circuit without a flowmeter. By also measuring a temperature drop, we can estimate and control a heat flow and provide remote thermal and hydraulic diagnostics of a connected heat terminal via the device. It is powered and communicates through the Ethernet and contains a wet-rotor BLDC pump controlled by the field-oriented control method. A Kalman filter provides a mass flow estimate, and a robust distributed parameter system controller regulates the heat flow.

An ontology-based approach for building automation data analysis

Eunju Park — 2022-05-21

For the efficient and sustainable operation of building automation systems, it is critical to consider various aspects such as users’ comfort requirements and energy consumption. The successful application is associated with the integration of multiple and heterogeneous data sources. However, the high complexity of the data poses a challenge. To address this problem, various ontologies have become popular with many applications for data modelling, management and analysis through harmonizing different data sources, as well as efficient querying. In this work, the design, implementation and usage of semantic approaches is investigated to exploit building automation data for customized room automation. As a main contribution, a building automation ontology focusing on room automation is proposed, which is represented in the Resource Description Framework (RDF). Furthermore, several scenarios with the proposed model are demonstrated in-situ, showing easier access to various data sources using a query language like SPARQL. Based on the ontology in RDF format, building data from different sources such as commercial building automation system (e.g. KNX), weather station and room monitoring sensors (e.g. temperature, humidity) are considered for multiple scenarios: (a) anomaly detection of shading automation systems, (b) monitoring user’s shading controls in automatic and manual mode, (c) identifying influential factors affecting user’s preference. The ontology-based approaches have benefits especially in multiple and heterogeneous data environments using a standardized common and controlled vocabulary. It allows engineers and researchers to enrich and interlink with various databases. Additionally, it explicitly describes the relationships between variables that make data understandable for both humans and machines.

Data driven energy efficiency in an air heated office building in Norway

Natasa Nord — 2022-05-21

There are lots of data stored about buildings that could be better used to improve the operation of existing and new buildings. In the long run, this means that building data can be used much more efficiently for energy, heat rate, and electricity reduction based on price and load. However, building data are only stored and the knowledge that may be found in this data is not fully utilized. The aim of the study was to evaluate potentials and opportunities with continuous energy, heat rate, and power reduction in an all-air heated office building in Trondheim, Norway. The observed building has an area of 14 000 m2 and the building was built according to the passive house standard. The background for the work was that high peak loads in electricity and heat are challenging for both the district heating and power grid. By reducing or moving the energy use of the ventilation heat to periods with low grid loads, cost savings can be achieved through a reduced rate in district heating and electricity. In this study, a model of the building was created in the simulation program IDA-ICE, where data about building body, outdoor climate, energy supply, energy distribution, set points for room control, operation and schedules were used from a real building. This included measurements of the outdoor temperature, supply temperature, internal loads, electricity use, district heating, and hot water, as well as indoor temperatures and air flow rates. Various scenarios were developed to reduce peak loads in heating and electricity with the focus on controlling the ventilation system. The results for the annual simulation showed a reduction in ventilation heat rate from 12% to 33%. Further, the results showed a cost saving for heat and electricity from of 10% to 16%. The study may be useful for facility managers, operators, and end users of office buildings that want cost-effective building performance improvement.

From Data To Control

Bram de Wit — 2022-05-21

This study introduced a framework for smart HVAC controllers that can be used at scale. The proposed controllers derive their control policy solely from data. First a simulator of the process is learned, which we call the Neural Twin. The results showed that the Neural Twin framework is able to simulate several distinct processes with an average absolute error close to 0.2 °C for all processes, even when predicting several hours ahead. Then, the Neural Twin was used to develop two different control algorithms. The first algorithm learned a control policy for a process using a neural network. The network was trained using Proximal Policy Optimization by gathering experience from the simulated environment provided by the Neural Twin. The second algorithm performed Model Predictive Control using the Neural Twin at real time during control. It used the Neural Twin to choose an optimal control sequence, given a set of possible control sequences. It selects the optimal control sequence based on a horizon, which is usually a few hours ahead. Both control algorithms were inspected in several environments and for one of those environments the best controller was tested on a physical room. The results show that the control algorithms were able to handle a wide variety of different processes, without manual tuning. The controllers achieved improved performance compared to the conventional control algorithms, which were manually tuned, mainly in terms of energy usage. It is estimated that the proposed controllers can lead to a 5% - 40% decrease in effective energy usage, while retaining the thermal comfort and stability. The controller trained using reinforcement learning showed the best performance. From the results it was concluded that the control methods pose an attractive alternative compared to conventional controllers.

From BIM databases to Modelica - Automated simulations of heating systems

Esben Visby Fjerbæk — 2022-05-21

Detailed simulations of HVAC systems play a crucial role in creating 1:1 digital twins of buildings and their systems. In particular, detailed models of hydronic systems are essential for fault detection of building services and control optimization. However, modeling HVAC systems is labour intensive due to the components and connections that one must create based on drawings or models. Creating the HVAC simulation models from BIM data eases the modelling burden, simplifying the creation of digital twins. Straight-forward HVAC simulations can aid the design process. Instead of prescriptive design based on the worst-case conditions, simulations enable performance-based design with partial-loads and dynamic behaviour. This paper presents a preliminary tool using BIM data to create and simulate models of heating systems. The tool uses a central BIM data platform with a dedicated data format – defining components and their relations in a database. Python scripts apply model templates to create heating system models in the Modelica language. The tool simulates the models in Dymola, while Python scripts read and parse the results to the database for visualization and analysis. The tool efficiently simulated a small heating system and obtained results for the return temperatures of several loops.

Real-time Model Predictive Control with Digital Twins and Edge Computing Technologies

Michael Berger — 2022-05-21

Buildings consume almost a quarter of Worlds Energy Consumption and hence are one of the major sources of emissions globally. In commercial buildings, HVAC is by far the most energy intensive system, accounting for close to half of the total energy consumption. For this reason every efficiency improvement in HVAC performance can significantly reduce the energy profile of the building, turning HVAC optimisation into a core requirement to deliver energy efficiency. Fundamental to optimising large energy consumers in today’s modern buildings is the use of Machine Learning in order to dramatically improve the energy efficiency of modern central cooling and heating plants. This paper will demonstrate the techniques that have been implemented to deliver advanced Real-time Model Predictive Control on Edge Computing solutions that don't require Cloud connectivity or significant computing power. Through the use of deep domain knowledge and advances in Edge Computing, it is possible to 'learn' highly accurate models of how mechanical machines operate and apply those models to predict and then solve complex optimisation problems for advanced control and improvements in energy efficiency. The authors will show how, through the collection of real-time sensor data, our platform has successfully reduced energy consumption and electrical demand in real buildings without compromising space comfort in any way at all. The capability to generate self-adjusting control algorithms in an on-premises scenario not only delivers significant outcomes but lowers overall Total Cost of Ownership for the end client. The absence of ongoing subscription fees further improves the economic model and the case for on-premises, real-time, model predictive control. Furthermore, the paper will demonstrate how the same Digital Twins used for Model Predictive Control can be used for anomaly detection algorithms or Fault Detection and Diagnosis as well as Predictive Maintenance and that this will create new service opportunities and business models for smart companies of the future whilst continuing to deliver optimal performance of mechanical systems.

Development of a remote refrigerant leakage detection system for chillers and VRFs

Shunsuke Kimura — 2022-05-21

In Europe and Japan, owners of large refrigeration and air-conditioning equipment, such as chillers and VRFs, are required by law to carry out regular inspections for refrigerant leaks. There are two methods of regular inspection: the direct method, which uses visual inspection and leak detectors equipped with gas sensors; and the indirect method, which uses equipment operating data to estimate leaks. However, large equipment requires many inspection points and direct inspection is time-consuming and labor-intensive, placing a heavy burden on both the equipment owner and the inspector. On the other hand, the European F-gas regulation provides an incentive to halve the number of inspections if a permanent leakage detection system is installed, and similar incentives are being considered for other countries regulations. The authors developed a highly accurate refrigerant leakage detection system using machine learning techniques that can be used to meet incentive requirements. The details of the technology and the accuracy of the detection system tested on chillers and VRFs are discussed in this paper.

Impact of Traditional Augmentation Methods on Window State Detection

Seunghyeon Wang — 2022-05-21

Window state information and changes can help understand ventilation patterns or be used as input in energy models. State identification can be achieved by capturing time-lapse images and processing these through a deep learning model. Deep learning methods have shown reliable performance in object detection tasks such as window and door detection, but have not been applied for window states detection. One of the challenges in setting up such models is to collect a large number of images of window states. In this case, image augmentation can be a critical pre-processing step to enhance the training dataset artificially. Image augmentation has been beneficial in similar contexts and applications. This paper investigates image augmentation methods, adjusting for brightness, scale, and weather. Windows images were used as the starting dataset to demonstrate the proposed methods, and augmented images were artificially generated from the original images. Using the expanded dataset, the Faster R-CNN (faster region-based convolutional neural network) trained a model to detect the binary window states. The augmented dataset model showed better performance than when the original dataset was used. The findings are a testament to the utility of image augmentation methods in the training model of window states detection using deep learning methods.

Digital Twin for Heat Pump Systems

Joachim Seifert — 2022-05-21

Numerical building simulation is a tool that has been used intensively for years to analyse systems engineering in buildings. In the past, the focus of the development work was increasingly on the creation of detailed partial models and the coupling to other simulation programs, which was called co-simulation in the professional world. The development work regarding the coupling of building and plant simulation programs with programs of the numerical flow simulation is to be mentioned here. Currently, the coupling to measurement technology is pushed more strongly, whereby the focus is seen on the parallel use of the numerical model to a real system. This development is called "digital twin" of components or subsystems in power engineering. The following article addresses this development and would like to describe the system concept of a digital twin using the example of a heat pump technology. Based on the characterization of a special use case, the digital twin will first be divided into the development phase, field test phase, and deployment phase of heat pumps. Different model accuracies of the digital twin are assigned to the individual phases. In a second step, the different models for the component’s compressor, heat exchanger, expansion valve, and the necessary piping are described. The coupling to a building simulation program is also part of the article. Furthermore, an essential point is the interaction with a cloud platform, in which the comparison between measured values and values from the digital twin takes place. Here, the focus is on the data exchange formats and the additional analysis tools that were used in the system concept. The paper concludes with a demonstration of an example under laboratory conditions within the Combined Energy Lab (CEL) of the TU Dresden.

Enhanced building energy flexibility using passive PCM envelope and HVAC control automation

Mohammad Saffari — 2022-05-21

One solution for improving the thermal performance of existing building envelopes is the use of pre-formed internal insulative panels that incorporate impregnated phase change materials (PCM). Such measures have the potential to enhance the energy flexibility of buildings when combined with HVAC control automation and digitalisation techniques, thereby offering the possibility of participation in demand side management measures such as demand response programmes. The current literature on building envelope physics lacks research on the integration of such PCMs in building envelopes and advanced HVAC control automation, especially in the context of research into the energy flexibility and demand response nature under heating and cooling scenarios. The aim of the current study is to evaluate how the addition of PCM impregnated internal wall panels and HVAC thermostat control automation affect both the thermal performance of the building envelope, as well as the wider building energy characteristics, when subject to different demand response events. The reference building is a detached residential house which has a floor area of 160 m2 and a south-easterly facing aspect. This study presents a building energy management methodology to develop new energy flexibility indicators for HVAC thermostat control automation taking into consideration a pre-cooling period prior to the demand response event as well as evaluating the thermal energy storage capacity and peak power curtailment. Four different demand response scenarios are examined. Simulation results show that shorter envelope pre-cooling periods in association with longer demand response periods are preferable for all envelopes to achieve the maximum power curtailment for cooling. Gypsum boards enhanced with PCM were retrofitted as part of lightweight thermal mass and medium weight thermal mass envelopes and are shown to give best cooling demand shifting and performance. It is concluded that for energy flexibility scenarios, the pre-cooling length should be always less than the length of the demand response event to ensure higher cooling efficiencies.

Development and evaluation of digital twins for district-level heating energy demand simulation

Twan Rovers — 2022-05-21

To achieve the aim of a CO2 neutral built environment in 2050, a large part of the existing housing stock will have to be energetically retrofitted. It has been noted that a neighbourhood-oriented approach will be necessary for the feasibility, affordability and timeliness of this aim. Considering that many different stakeholders are involved in renovations at the neighbourhood level, and that multiple neighbourhoods will have to be retrofitted at the same time, efficient working methods are imperative. To facilitate the design, construction and operation of the new energy infrastructure, a prototype for a digital environment (digital twin) is developed for four Dutch pilot neighbourhoods. In this contribution, the authors will describe a procedure to convert publicly available geo-information to a CityGML model, which is used to simulate the monthly and annual space heating energy demand using SimStadt. To assess model fidelity, the simulation results are compared with publicly available aggregated energy use data. A procedure will be described to split the measured natural gas use into gas usage for space heating, domestic hot water and cooking. It is found that the simulation tends to overestimate the energy demand for space heating by 4 - 125%. This difference is largely explained by the manner in which the thermal properties of the buildings are estimated. In addition, the homogeneity of the neighbourhood in terms of the different building functions present has an impact on the accuracy of the simulation. Finally, possible invalid assumptions concerning setpoint temperatures and internal heating loads are of interest. It is concluded that more accurate simulation results will be obtained through the use of current input data. Most importantly: (i) reliable information on the buildings’ current thermal properties through e.g. energy audits, and (ii) reliable information on the buildings’ setpoint temperatures and internal heating loads through on-board monitoring systems.

Interactive GUI for enhancing user awareness applying IoT-sensors and physics-assisted AI

Dietmar Siegele — 2022-05-22

Several studies proved that occupant behaviour has a significant impact on energy consumption and indoor comfort. Thus, monitoring data and Internet of Things solutions are used to address behavioural changes for promoting energy efficiency and increasing, at the same time, the comfort perception. The possibility of seeing invisible information, such as energy consumption or comfort parameters, on a digital support have been proved to be effective in increasing users’ awareness and to encourage efficient behaviours. This paper presents a GUI developed for increasing the user awareness and involving them actively in addressing their actions and presents the back-end architecture for making prediction and sharing feedbacks with the users. By means of the interface user can: (1) Visualize information related to monitoring data, selecting, and filtering the data they would like to see. (2) Receive real time personalized feedbacks based on behavioural predictions defined by using Artificial Intelligence (AI) algorithm. The AI algorithms are based on a physics-assisted approach to achieve better results with less input. Missing (monitoring) data is calculated by applying physical models (building energy simulations) and only for the remaining parts machine learning models are used. Mainly we apply LSTM models. (3) Express personal comfort feedbacks based on comfort perception, for setting user-oriented feedbacks. The first part of the paper describes the architecture of the monitoring systems and presents the GUIs developed for two different case studies: a social housing building and a nursery school. The personalization of the GUIs based on user’s typology has been done for enhancing the active participation and the involvement of the users in the project. The second part of the paper presents the back-end architecture of the GUI and the AI algorithms used for monitoring data analysis. The physis-assisted algorithm allows us to make predictions based on occupancy behaviour and to provide each occupant with tailored personalized feedback to promote energy-saving behaviours in real-time. We have placed more than 150 sensors in these two buildings that return us almost 1000 measured variables that can be used for the training of the AI models.

Improving the Calibration on Building Stock Level method by Comparing Objective Functions and Optimization Algorithms

Paula van den Brom — 2022-05-22

Many researchers have indicated the energy performance gap (difference between actual and predicted energy used in buildings), not only on an individual building level, but also on a building stock level. For policy makers it is important that predictions are correct on an building stock level to make them a useful tool to predict the effect of their proposed energy saving policies. Often not all input parameters for building energy simulations are known (e.g. insulation rates are often only possible to determine with destructive inspection or extensive measurements), therefore assumptions are made (e.g. assumptions for insulation rates are often made based on construction year). It is expected that a large part of the energy performance gap on building stock level are caused by incorrect assumptions of the unknown parameters in the building simulations. Previous research has shown that automated calibration of the assumptions on building stock level seems a promising method to reduce the energy performance gap and therewith make building energy simulations on building stock level a more reliable tool for policy makers. The previous research about calibration on building stock level was a proof of concept and still needs some improvements before it can be applied in practice. One of the aspects to improve the method is to determine the most suitable objective function and the most suitable optimization algorithm. In this paper we compare different objective functions (e.g. Root Mean Square Error, Mean Absolute Error, Sum of Absolute Errors). Next to that we compare different optimization algorithms (e.g. Genetic Algorithm, Particle Swarm and simulated Annealing Algorithm). For the comparison of the objective functions and the algorithms the former Dutch calculation method to determine the energy label in dwellings is used, in combination with the SHAERE database and data from the Dutch Statistics. The SHAERE database contains all input information on individual dwelling level to calculate the energy label of a dwelling of almost 2 million dwellings. The Dutch Statistics database contains the individual annual energy use of all dwelling of the Netherlands and can be linked to the SHAERE database.

A Reference Architecture for Data-Driven Smart Buildings Using Brick and LBD Ontologies

Pieter Pauwels — 2022-05-22

With the increasing adoption of sensors, actors and IoT devices in existing buildings, the real estate sector is becoming increasingly automated. Not only do these devices allow to monitor these buildings (energy use, occupancy, indoor air quality, etc), they also enable modelpredictive control (MPC) through building automation and control systems (BACS). A critical feature to enable these is the metadata associated to data streams obtained from the building. Such metadata allows building operators to assess what these data streams are, what they are measuring and how. This can be achieved using metadata schemes and vocabularies, such as Brick, Haystack, Linked Building Data, Industry Foundation Classes. Merging these model-based metadata schemas (semantics) with data-driven monitoring and control (machine learning) into a functional system architecture is a considerable challenge. In this paper, we review the mentioned technologies and propose a draft reference architecture based on state-of -the-art research. This reference architecture is evaluated using a set of predefined criteria.

Co-simulation studies of optimal control for natural refrigerant heat pumps

Thibault Péan — 2022-05-22

The object of the present study is a natural refrigerant base (propane) heat pump system with a dual source/dual sink heat exchanger (air or ground-based) which is integrated into a centralized tri-generation system with PV and battery for a multi-family building located in Spain. To evaluate the performance of this complex system, a simulation environment was developed, connecting different software. The main program is TRNSYS, with the python package pytrnsys used to create the models and run the simulations, while a model predictive controller is externalized in a separate optimization software. The co-simulation environment enables to couple both software and operate the models in the simulation with the decisions made by the external controller. This environment was used to evaluate the considered system for three separate weeks of the year, each representative of the heating/cooling/DHW demands in winter, summer and intermediate seasons. For each of these weeks, the simulation was run once with a reference rule-based controller, and once with the advanced model predictive controller, to evaluate the additional benefits brought by the later strategy. The results were then extrapolated to the whole year, and revealed that the model predictive controller was able to provide cost savings of 12 to 20% (depending on the consideration or not of the cooling season which gave unexpectedly adverse results). This controller operated the heat pump more efficiently thanks to its prior knowledge of the best source to use at each moment (air or ground). It also managed the battery in a more economical way thanks to its prior knowledge of the time-varying electricity price, thus charging always at the cheaper hours of the day, and demonstrating the advantages of using forecasts and predictive optimization for HVAC control.

FDD method for a variable-speed heat pump with natural refrigerants

Ivan Bellanco — 2022-05-22

Heat pumps are one of the most efficient devices to provide heat and cool. The number of heat pumps sold in Europe increases every year as European Legislation moves towards the use of natural refrigerants that have negligible global warming potential compared to synthetic refrigerants. Variable-speed domestic heat pumps may have hard-to-detect faults that increase energy consumption while the demand is still covered. These faults could worsen and take down the equipment. Fault detection and diagnosis (FDD) systems aim to detect these types of soft faults, reducing operating and maintenance costs. The present study is the result of developing an FDD system for variable-speed heat pumps. The FDD system has been tested with a 10 kW water-to-water variable-speed heat pump charged with propane. Some of the most common faults were emulated for 10 kW and 12 kW heating loads. These faults were evaporator fouling, compressor valve leakage, liquid line restriction and refrigerant overcharge. The present paper presents the overall structure of the developed FDD, each of its different modules and the performance indicators during tests. The FDD developed consists of different modules: a steady-state detector, the input space module, the no-fault regression models and the diagnosis module. The steady-state detector filters the measurements to select only the steady-state data. The input space classifies the data in clusters defined by the heat pump driving variables. For each of these clusters, a regression model is trained. Once trained, the deviation between the models and the real data will indicate a fault occurrence. The diagnosis module analyses the trends of different features to diagnose the fault. The FDD was able to monitor in real time the heat pump performance during the fault tests. The results showed fault detection before 10 minutes with COP drifts above 7 %. Each fault could be diagnosed correctly, except evaporator fouling, which was detected as a fault but could not be distinguished from the others.

DEVELOPMENT OF AN OPTIMIZATION MODEL FOR DECISION MAKING IN BUILDING RETROFIT PROJECTS

Ehsan Asadi — 2022-05-22

Retrofitting of existing buildings offers significant opportunities for improving occupants’ comfort and well-being, reducing global energy consumption and greenhouse gas emissions. This is being considered as one of the main approaches to achieve sustainability in the built environment at relatively low cost and high uptake rates. Although a wide range of retrofit technologies is readily available, methods to identify the most suitable set of retrofit actions for particular projects are still a major technical and methodological challenge. This study presents a simulation-based multi-objective optimization model to quantitatively assess technology choices in a building retrofit project (a combination of TRNSYS, and MOBO optimization freeware). This model is employed to assess a school building retrofit project as a case study to illustrate the practicability of the proposed approach, and therefore, the final decision (set of non-dominated solutions) for optimum building retrofit. The study starts with the individual optimization of objective functions focusing on building’s characteristics and performance: primary energy consumption, global costs, and thermal discomfort hours. Then the proposed multi-objective optimization model is used to study the interaction between these conflicting objectives and assess their trade-offs.

domOS: an “Operating System” for Smart Buildings

Junior Dongo — 2022-05-22

Smart energy services deployed in buildings have the potential to increase their energy efficiency and to turn them into active nodes of energy grids, with limited costs and in the short term. Today, smart services are deployed by manufacturers of energy appliances as independent silo solutions. The lack of a common approach prevents the deployment of unified multi-appliance, multi-service solutions. This paper presents the domOS ecosystem specification, a guideline for a unified organisation of energy services where multiple applications can access multiple on-line appliances and devices, if permitted. The specification leverages legacy IoT technologies and can be implemented with a limited effort on any existing IoT platform. A compliant IoT platform acts as an “operating system” for the building, effectively decoupling the application plane and the building infrastructure plane. The domOS ecosystem specification builds upon the Web of Things (WoT) architecture defined by W3C. Compliant buildings feature a digital nameplate called Building Description (BD). The BD is a document readable by machines and humans that contains relevant metadata (e.g., construction type, size, energy system…) and provides handles to monitor and control local energy processes. The domOS ecosystem specification leads to a unified and standardised approach of energy services in buildings.

Flipped Classroom Concept for Industry 4.0 Pump Monitoring in Building Information Technology

Daniel Eichberger — 2022-05-12

The Flipped Classroom teaching concept has already proven itself in regular school and university teaching for some time. It is already regularly used for frontal teaching, lectures, seminars, and exercises at many universities. For some time now, practical laboratory courses and projects have become the focus of digitalization. Considering distance learning in particular, solutions must be found in this field. This paper describes the didactic concept, the technical background as well as the implementation of a flipped project in the master course Building Automation. It answers the research question: "How to design didactics and implementation of a practical laboratory project on the topics of information modeling, OPC UA and Self-X capabilities using the example of pump monitoring for realizing it as a flipped classroom teaching concept for master students of Building Automation?" To answer the research question, established concepts of didactics were combined with established and new technologies. On the didactic aspect, resources and methods such as explanatory videos in the form of screencasts, competency-oriented learning objectives of different taxonomy levels and group work according to the partner-ship model are used. Combining this with technological tools and concepts, such as a GitHub Repository as reader, task collection and forum, Node-RED as low-code environment, OPC UA, information modeling and Self-X as challenging content emphasis, results in a modern and demanding Flipped Classroom teaching concept. Evaluation, student feedback and conclusion show that even high complexity practical projects can be realized as a Flipped Classroom concept on the level of a master's program. Furthermore, the project can be replicated at any time and, thanks to the manual, can in principle be carried out by any teaching staff or even other laboratories. Further work must primarily address the potential for optimization in terms of organization and content, yet the abstraction of the described project to a meta-level is also conceivable.

From insight into energy transition maturity to powerful task-based cross-sectoral upskilling

Jan Cromwijk — 2022-05-17

To make advancements in energy transition and creating a future proof built environment, professionals and workers who possess required skills are crucial. This paper proposes a model that can be flexibly adopted to reach an acceleration of upskilling opportunities and outcomes. The paper outlines the Technological Innovation Systems approach for delivering cross-sectoral knowledge and skill development agendas, as well as a method to develop and apply skills mappings and task-based qualifications. The combined approach is a stepping stone to enable digital support for learning on the job, learning transaction based recognition of successfully acquired knowledge and skills, as well as skills passports and micro-credentials. The approach has proven to be useful for sectors where technological innovations heavily influence ways of working, and it enables a common reference methodology in Europe. In order for the approach to be utilised optimally, key requirements should be taken into account, indicating that the taxonomy, toolkits and context of skills should be well aligned. The paper suggests future developments to address the transorganisational implementation of the approach, and the transitional management of skills gaps.

Data encounters in renovated homes

Evert van Beek — 2022-05-12

There is an increasing acknowledgement of the role of residents in the success of low- or zero-energy renovations. One of the approaches to improve this factor is by influencing resident behaviour by means of devices for feedback on consumption. The goal of these systems is to help residents make sense of the relation between their actions and choices, and their energy consumption, indoor environmental conditions and comfort. In this paper we describe interactions with these devices as one form of data encounter. We then suggest that there are other forms of data encounters already happening in renovated homes by which residents make sense. These data encounters are useful to understand if we want to understand the interactions between residents and buildings. We introduce the concepts of sense-making and interactive adaptation to better understand these data encounters. In this study we show data encounters in various forms as they happen in four renovated homes in the same building in the Netherlands. We use interviews and video-recorded walkthroughs to identify data encounters related to indoor climate and energy consumption within these homes. We find data encounters that involve more than displays and technical devices. Residents use bodily senses, information from other people, and complex contextual information to understand indoor climate and energy consumption. We also find that data encounters relate to, and are embedded in everyday practices and routines. Finally, we find that data encounters involve active sense-making rather than passive consumption of information. We discuss these findings and conclude by suggesting that existing data encounters could serve as a starting point for the improved design of buildings, renovation processes, and the selection, design and implementation of new data encounters.

Integral design a necessity for sustainable building design

Wim Zeiler — 2022-05-13

Due to the rising demand for more sustainable buildings it is essential to make optimal use of the natural resources of sun, earth, water and wind. There is a urgent need saving energy and the necessity of zero or even energy positive buildings in the near future. However, therefor it is necessary to end the dichotomy between architecture and technology. This dichotomy leading to far from optimal functional buildings with poor indoor comfort and health conditions and also being responsible for high operational and failure costs. To close the gap between technology and architecture, between science and art, it is important to no longer subordinate to architecture but part of architecture itself. Instead of integrated design it is time for integral design. Architect and engineer working really together within the conceptual design phase of a building. It seems so easy however, it take an enormous mind shift for the engineers to become designers. The necessity for this was recognized by the Dutch Royal society of Architects, BNA, as well as the society of Dutch consulting engineers, NL Engineers. As a result the combined research project Integral Design was started together with the Dutch Building Services society, TVVL, in 2000. As a result of this project a design methodology was developed and implemented in the education curriculum of the Technical University of Eindhoven. In this paper the method and experiences of the application and testing of the method by organizing workshop between professionals and students will be presented

Learning and Knowledge Transfer of Professionals within the Building Services Sector

Mohammad Samir Ahmed — 2022-05-14

Buildings need to be carefully operated and maintained for optimum health, comfort, energy performance, and utility costs. The increasing use of Machine Learning combined with Big Data in the building services sector has shown the potential to bring energy efficiency and cost-effectiveness. Therefore, upskilling and reskilling the current workforce is required to realize new possibilities. In addition, sharing and preserving knowledge are also required for the sustainable growth of professionals and companies. This formed the basis for the Dutch Research Council funded TransAct project. To increase access to education on the job, online learning is experiencing phenomenal growth. A study was conducted with two focus groups - professionals of a building service company and university researchers - to understand the existing challenges and the ways to improve knowledge sharing and upskilling through learning on the job. This study introduced an Enterprise Social Network platform that connects members and may facilitate knowledge sharing. As a community forum, Yammer from office 365 was used. For hosting project files, a SharePoint page was created. For online courses, the company’s online learning site was utilized. The log data from the online tools were analysed, semi-structured interviews and webinars were conducted and feedback was collected with google forms. Incentive models like social recognition and innovative project results were used to motivate the professionals for online activities. This paper distinguishes the impacts of initiatives on the behaviour of university researchers vs company employees.

Integrating technology, education and practice to change energy behaviours in schools

Edelle Doherty — 2022-05-15

Schools are learning communities where multiple stakeholders can collaborate to learn about energy efficiency, including via formal curricula, non-formal learning and day-to-day practices. Furthermore, by improving energy literacy among building occupants, the energy efficiency of schools can be improved. However, turning schools into learning communities rather than learning organizations is still problematic. This article details a case study realised in the form of the ENERGE project, which integrates technological, educational and practical activities in 13 post-primary schools from 6 European countries. Owing to an extensive collaboration of diverse stakeholders, the ENERGE project resulted in the origination of a learning community around energy efficiency in the schools. The outcomes of building a learning community within the ENERGE project included: capacity building (in the form of the ENERGE Committees and Teacher Network), the introduction of digital education (via the ENERGE digital platform), development of curriculum-based modules to raise energy literacy, and the establishment of a viable model for expanding ENERGE experience to other schools. The article concludes by explaining the benefits of the ENERGE approach for stakeholders.

Interactive worksheets as a resource for teaching building performance and energy systems simulation

Roel Loonen — 2022-05-16

This paper describes the development, implementation and evaluation of Jupyter Notebooks as a digital tool to promote (i) self-directed learning of theory concepts and (ii) active engagement with practical assignments in a graduate-level course on building performance and energy systems simulation. Jupyter Notebooks are gaining popularity as an educational tool for their ability to accommodate digital documents that weave together executable code, equations, data visualizations, and narrative text, without the need for dedicated software environments or advanced programming skills. Specifically, Jupyter Notebooks allow the user - in this case both the lecturer and the student - to bring together data, code, and prose, to tell an interactive, computational story. In our case, the Jupyter Notebooks are used as a teaching resource to foster individualized place and time-independent learning as part of a regular on-campus course, with particular emphasis on homologation of students with heterogeneous backgrounds and for proactive engagement with theoretical subjects. This paper follows the principles of ‘constructive alignment’ to highlight various aspects of the use of Jupyter Notebooks in this engineering education context. After a general discussion of the course set-up and key learning objectives, the implementation part of the paper showcases a number of concrete examples of the interactive worksheets on the subjects of thermal comfort assessment, building-integrated renewable energy systems and smart grid interaction. These example assignments illustrate a variety of tasks and functions, including dataset manipulation, scripting assignments, click-and-learn apps and explanatory video clips. An evaluation of the approach is presented on the basis of student questionnaires and informal evidence collected during two years of running the course. The paper finishes by providing a critical reflection of opportunities and caveats and suggested directions for further development.

Closing the Knowledge Gap on Circularity: the CBE Hub Lifelong Education Programmes

Tillmann Klein — 2022-05-16

This paper discusses the relevance of academia in addressing complex contemporary issues and more specifically, its potential to help society transition to a circular built environment. Can academia provide society with a safe space for developing imaginaries and socially performing alternative political futures? Can it help reconnect the many knowledge domains that appear now to be dispersed and fragmented? And what is the role of adult learning in achieving this transition and in dealing with complex issues such as sustainability? The typology and goals of adult educational modules developed by the Faculty of Architecture and the Built Environment of TU Delft and in particular the Circular Built Environment (CBE) Hub are presented here as a response to the growing need of creating synergistic alliances between academia and the rest of society. Three different typologies are examined in this chapter for their specific contribution in raising awareness; inspiring professionals and instigating change in attitudes as well as contributing to the training of selected groups of stakeholders respectively. Authors reflect on the benefits of such interaction, its limitations as well as its future potential. Promoting the benefits of transitioning to a circular built environment and reaching the widest audience possible to assist with the transition requires that academia develops new educational formats. Attention should therefore be given not only to the content produced, but also to the modes of delivery; the effectiveness of the message that is ultimately delivered as well as the establishment of a continuous presence where different individuals or groups can return to when challenged by complex issues. Consolidating this relation can close the knowledge gap between the two: on the one hand society directly benefits from academic research, on the other hand, academia becomes more relevant for society.

A first attempt in shaping learning communities for the energy transition

Margot van Rees — 2022-05-17

Learning communities (LCs) can be seen as an promising concept to shape professional development and thereby enhance innovation for the energy transition. However, as the design of an LC is dependent on the needs of the participating organizations and the problems they want to solve, no general blue prints are available for shaping an LC. Therefore, this study aims to find an answer to the question: How should LCs for the energy transition be designed to support participants’ professional development and stimulate innovation? First, a literature study and needs assessment was conducted at eight SMEs in the installation sector, which led to an LC prototype. The LC prototype was then tested in four different SME’s which eventually provided an LC prototype for the installation sector that stimulates professional development and innovation.

Reflections on flipped classroom and digitized laboratory concept in building automation courses

Jochen Müller — 2022-05-20

In the last decade, innovative digitized teaching concepts were developed to improve the learning environment of students. Also due to actual restrictions concerning classroom teaching during the corona pandemic, these concepts are increasingly spreading in daily university life. This article describes our experience of the last five years with digitized lecture and laboratory based on the flipped classroom concept. A comparison to the classic teaching form is difficult to achieve in daily university practice. Thus, the paper reflects the applicability of flipped classroom format for control engineering and building automation based on subjective experiences of students and tutors, as well as lecturers.

Using Social Network Analysis to explore Learning networks in MOOCs discussion forums

Ali Soleymani — 2022-05-20

Learning and educational challenges in the field of indoor climate and building services like energy systems are mainly due to the transformation of professional practices and learning networks, a big shift in the way in which people work, communicate, and share their knowledge and the need for additional workforce, either juniors or coming from other disciplines. One of the most important factors that highly influence professional development and workplace learning is networked learning. Our goal in this study, is understanding the learning networks characteristics and patterns of interaction using Social Network Analysis techniques in three MOOCs discussion forums. The result of this study shows not only the importance of Learning networks and peer support on professionalization of learners, but also how pedagogical approach of instructors in MOOCs can foster learning networks. This novel approach in developing learning networks and communities is not only able to help connect young professionals and experienced practitioners digitally, but also it can promote professional development and innovation in the energy installation sector.

A structured approach to online education of future HVAC and energy professionals

Laure Itard — 2022-05-22

The HVAC sector is essential to realize the energy transition and is facing numerous challenges like educating enough HVAC engineers to carry out the task and being able to integrate knowledge from the construction, energy, IT and health sectors and to cope with rapid technological changes. The availability of structured and easy-to-follow courses on HVAC and energy systems for buildings at higher education level could help to motivate (future) engineers to contribute to the HVAC sector, and to understand how challenging and high-tech it is. Such a course program would ideally also bring a basic understanding of the field to architects and building engineers, in such a way that a better common ground is created for collaboration and integrated design. It would also be useful to Machine Learning and Artificial Intelligence experts joining the HVAC sector. Last but not least, it could help bridging the gap between engineering and policy making, by here too, offering common views on primary energy, resource depletion and CO2 emissions relating to HVAC systems. The paper describes the structure and content of such an on-line course program. It was developed based on years of teaching experience with international master students of Mechanical Engineering, Civil Engineering, Architecture, Technical Management and Policy, Electrical Engineering and with professionals from housing associations, ministries and municipalities. The choices for the program structure, based on systems engineering, are underpinned and explained, as well as the choices for specific contents. Additionally, experience with the development of self-assessment tools for students, and self-paced courses is shared, as well as the feed-back from students. A first version of the course program was tested on the edX platform with more than 5000 students participating in each module and is publicly available.

A New Learning Programme to Facilitate nZEB Implementation

Florin Bode — 2022-05-22

The goal of nearly zero-energy can be achieved nowadays with existing technologies and practices, but the concept is still unfamiliar and elusive in most of the European countries, considering the whole process chain, despite all previous initiatives in this direction. At this moment there are still barriers in the value chain, making the nZEB concept difficult to arrive at the final users. The nZEB market analysis at European level reveals a significant gap between the countries with a high level of implementation and those which are not so well performing, and which remain more and more behind. To overcome this, a new learning programme to facilitate the nZEB implementation, has been launched in 2021 with the main objective to create support mechanisms and stimulating the development of skills frameworks by new market driven mutual recognition training and certification scheme for nZEB deployment that will facilitate the necessary legislative changes.

Open BIM-based LCA of HVAC and circularity assess-ment using the Madaster platform

Sebastian Theißen — 2022-05-16

In Life Cycle Assessments (LCA) of buildings and circularity assessment, Heating Ven-tilation and Air-Conditioning (HVAC) systems are almost completely ignored due to the lack of regulation requirements, simplified consideration in green building certification and high com-plexity. Therefore, there is a lack of relevant information that enables a comprehensive whole building LCA and a circularity assessment of materials in HVAC. Using a digital Material Passport (MP) for buildings enables combining whole building LCA with qualitative and quantitative as-sessments of circularity. The open Building Information Modeling (BIM) method and the open data exchange format Industry Foundation Classes (IFC) offer a high potential for the efficient creation and management of a MP, as data can be integrated, linked and exchanged in 3D models with a high degree of semantics. This work analyses the life cycle assessment and circularity of two design variants of Ventilation and Air-Conditioning (VAC) systems of an office building within an open BIM-based process. Thereby, the embodied carbon of the VAC design variants was ana-lyzed within an open BIM-based LCA. As a second step, the VAC models were assessed regarding their circularity using the Madaster Circularity Indicator (MCI) and detachability index within the Madaster platform as a case study. The results show that the impact of VAC materials is very im-portant to consider within a whole building LCA, as VAC cause high material-related embodied impacts. In addition, the circularity assessment, using MCI and Detachability index, shows that the reduction of material mass does not influence the assessment. Instead, Design for Disassem-bly (DfD) turns out as a very important factor, which can also provide information for a more realistic assignment of end-of-life scenarios, effecting LCA results interpretation in the future. However, therefore various competencies in planning, data modelling and sustainability assess-ment need to be more connected. The open BIM approach already offers the tools to make this more efficient and automated. The research shows advantages and obstacles of open BIM based LCA and circularity assessment of HVAC and provides insights for further research regarding a more holistic assessment of buildings.

Should we ventilate differently in an adaptable context?

Oskar Seuntjens — 2022-05-20

Currently a great number of buildings, that are not able to meet the evolving needs of building owners and users, are being demolished before reaching their technical life span. To avoid such waste, it is crucial that buildings have an adaptable design in order to allow for flexible building usage. Ventilation is crucial in this transition as a flexible building usage can lead to fluctuating ventilation requirements. However, knowledge about how to choose between ventilation systems in an adaptable context is sorely lacking. In this research, an exploratory LCA-study will be carried out on two ventilation systems in an adaptable context over a period of 15 years. The case study concerns a school building where a reconfiguration of the floorplan design is planned every five years. The first ventilation system concerns a centralized balanced mechanical ventilation system which uses a heat recovery system and ductwork to distribute the air to all the classrooms. The second ventilation system is a ductless exhaust ventilation system which uses three exhaust fans to extract air and vents above windows to supply air naturally. Despite the centralized balanced ventilation system having a higher energy efficiency, the environmental impact of this ventilation system is 40% higher than the impact of the ductless exhaust ventilation system. This is caused by the use of a great amount of ductwork and an air handling unit. The largest share of the environmental impact of the ductless exhaust ventilation system is related to the additional energy that is needed to condition the temperature in the classrooms. Further research should include other ventilation systems and flexibility scenarios as well. Moreover, follow-up research should not only quantify the environmental impact but also assess the financial impact of ventilation systems in an adaptable context.

Embodied Energy and Carbon of Residential Buildings

Nazanin Moazzen — 2022-05-20

Over the past few decades, energy efficiency policies have concentrated more on buildings' energy consumption and performance. EU established strategies by energy performance of buildings directive and its amendments for all new and retrofitted buildings to achieve nearly Zero Energy Buildings (nZEBs). Most of the studies and approaches cover the operation phase of the building life cycle, while, by observing the building's whole life cycle, it is determined that buildings are accounted for energy consumption during not just the operation phase and also the construction and demolishing stages. Consequently, the most prominent buildings should progress towards nearly Zero Energy Buildings by evaluating the energy consumption during the whole life cycle and not just during the operation. The embodied energy that covers the energy consumed in the process and manufacturing of the material, transportation, and installations on-site, is intensive energy consumed in a short period compared to the operation energy.
Residential buildings are accounted for extensive energy consumption among different building typologies due to their size and number. According to various studies on residential buildings, in conventional and low energy buildings, the share of embodied energy has varied between 6 and 20%, and 26 and 57%, respectively. It means that embodied energy of the buildings is not negligible.
Consequently, a logical method for residential buildings to reach the nZEB level using energy-efficient measures and proper materials considering the life cycle of buildings is inevitable. The paper aims to investigate the possibility of obtaining nearly zero energy levels in residential buildings reflecting the whole life cycle. The paper has concentrated not only on the operation energy but also on the embodied energy and carbon commencing from applying various measures to the building. The embodied energy and carbon data for building materials have been obtained from the Intergovernmental Panel on Climate Change (IPCC) database. All primary energy consumption of the building and improvement measures during the operation phase are computed with dynamic simulation tools, EnergyPlus and DesignBuilder. The life cycle energy consumption and CO2 emissions of various measures have been calculated. Optimum alternatives have been proposed in the temperate-dry climatic zones of Turkey.

BIM-based circular building assessment and design for demountability

Tetiana Lukianova — 2022-05-20

The on-going transformation of the linear economy model (LE) to a sustainable circular economy (CE) creates new challenges for information management, evaluation methods, and information exchange. This impacts also the traditional definitions of roles and processes in the AEC sector. OpenBIM and a proper definition of the design process and the key decision points based on EN ISO 19650 and using the IDM framework (EN ISO 29481) can help to master these challenges. This is complemented by the need for reliable product data that could be satisfied by implementing EN ISO 23386 and 23387 together with the more specific EN ISO 16757 tailored for the needs of the HVAC sector. While the general methodology has recently been defined in these international standards, the concrete application for sustainable design and many implementation details remain still open. This paper presents a BIM-based scoring approach for Circular building assessment (CBA). It defines the information needs at different design stages: from the requirements in an early design stage to the solutions chosen in the detailed design stage. The same methodology can be applied to structural elements of the building envelope as well as to technical equipment and HVAC systems, providing a common framework for the integrated design of sustainable buildings. Besides the methodology, this paper describes a first implementation for the case of the Living Lab (LL) building, a prototype dwelling in Ghent (Belgium) built in the scope of the Circular Bio-Based Construction Industry (CBCI) project funded by the EU Interreg 2 Seas program. The aim of this paper is to demonstrate how BIM can be used to partly automate decision-making and evaluation for the specific needs of CBA and design for demountability. The proposed solution based on Alba Concept is creating an efficient link between an external database and the BIM model. This is performed by extracting the necessary object information and integrating it for further evaluation during the lifecycle of the building including the design, construction, operation, end-of-life and re-use phases.

Application of circular technical services in a living lab in Ghent

Lode Lefevre — 2022-05-20

The construction industry in the EU possesses great potential for mitigating environmental impacts because of its large share in resource use and waste production. The Circular Economy Action Plan of the EU stimulates the sector to adopt more circular principles and bio-based material use. The European Interreg 2 Seas project “Circular Bio-Based Construction Industry” (CBCI) is in line with these European ambitions researching technical, economical, legal and, social aspects. In the course of the project, a prototype for a terraced single-family house called the living lab (LL) Ghent is developed and constructed in close collaboration with multiple stakeholders of the construction sector. The building implements and tests the research outputs in a real-life setting. During the development of LL, the circularity of building components was taken into account by utilizing the layers of Brand approach. Among those layers are structure, skin, technical services and, space plan. On the one hand, each layer has its specificity (e.g. life duration). For example, for technical services and space plan, components are subject to upgrades and/or replacement more often than those in other layers. The retention and reuse of valuable materials and components need to be anticipated. This calls for circular strategies and solutions corresponding to each layer. On the other hand, the layers are interdependent and integrated in terms of energy performance and spatiality. This interconnectedness compromises the efficacy of the applied circular strategies. Despite the need for such circular strategies, existing assessment tools seldom focus on technical services due to a lack of appropriate design methods and increased investment costs of components suitable for reuse. This paper documents the translation of existing European assessment tools as method and related design strategies for layers of structure, skin and space plan to the layer of technical services. The selected design strategy was an iterative process ensured by a design & build procurement and the solution for the integration of technical services was determined as a plug-in unit which is part of a modular CLT technical core. It is expected that the technical unit will continue its lifetime beyond the lifetime of LL Ghent.

The circularity of renovation solutions for residential buildings

Kalle Kuusk — 2022-05-21

Construction and demolition waste accounts for approximately a third of all waste generated in the EU. Adopting circularity principles to the construction processes aims to reduce waste generation. The focus of the study was on circular renovation solutions as renovation is becoming increasingly important. The renovation wave for Europe sets a target to double annual energy renovation rates in the next ten years. This study analyses circularity of the renovation concepts for the pilot renovation cases in seven countries in different climate zones in Europe. Analyses were carried out within the DRIVE 0 project funded by the European Unionâ€™s Horizon 2020 research and innovation program. Pilot buildings are detached houses and apartment buildings with different renovation interventions. Design for Disassembly criteria and embodied energy and embodied CO2 analyses combine design and material use aspects. Results show that in terms of design for disassembly indicators, prefabricated modular solutions have much higher circularity potential than the traditional wall insulation systems due to the low disassembly and reusability potential of external thermal insulation composite systems (ETICS). The environmental impact of the prefabricated insulation solutions is lower than and ETICS solutions. Although the difference between prefabricated and ETICS solutions in terms of environmental impact is smaller than in terms of disassembly and recovery options.