Field test of a novel combined solar thermal and heat pump system with an ice store

The technological combination of solar thermal systems with heat pumps continues to be a highly topical subject in the market of sustainable domestic hot water and space heating concepts. The main background for this development is the expected increase of efficiency for both, the solar thermal system and the heat pump due to synergetic effects resulting from the mutual interaction of these two sub-systems. Solar thermal energy can be used for example to provide the heat pump with higher heat source temperatures, which is beneficial to its performance factor, while the solar collector’s degree of efficiency rises simultaneously due to lower return temperatures in the solar loop when using the heat pump or an additional buffer store for this purpose as second heat sink. Nonetheless, objective performance test methods for such combined systems are not yet common standard. In this context field tests with different combined solar and heat pump systems installed in several single family houses in Germany are being performed by ITW within the project “WPSol”. In this paper a novel combined solar thermal and heat pump system using an ice store for domestic hot water preparation and space heating in single family houses, in the following named solar ice store system, is presented as one selected example of the investigated system concepts. The solar ice store system consists of different types of solar thermal collectors in combination with a brine to water heat pump which utilises an ice store as only heat source. The system’s functionality and the monitoring procedure are described and first results are discussed.