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

Abstract

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).