Hydraulic Integration and Control of Heat Pump and Combi-storage: Same Components, Big Differences

Field test as well as laboratory measurements have shown that the performance of systems that combine heat pumps with combi- storages is often lower than expected. One reason that has been identified is a large gap between the temperature level provided by the heat pump condenser and the useful heat distributed for space heating and/or DHW. Within this work, different options for hydraulic integration and control of a heat pump connected to a solar combi-storage are investigated by means of annual system simulations. The results show that unfavorable hydraulic integration can lead to additional electric energy demand of the system of up to 45% (>1000 kWh electric energy per year) compared to a - well designed - reference solution with the same components. Based on the system performance analysis, recommendations are given for the hydraulic integration of heat pumps into systems with combi-storages.