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

Abstract

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.