Simulation study on a Domestic Solar/Heat Pump Heating System Incorporating Latent and Stratified Thermal Storage

Both solar and heat pump heating systems are innovative technologies for sustaining ecological heat generation. They are gaining more and more importance due to the accelerating pace of climate change and the rising cost of limited fossil resources. Against this background, a heating system combining solar thermal collectors, heat pump, stratified thermal storage, and water/ice latent heat storage has been investigated. The major advantages of the proposed solar/heat pump heating system are considered to be its flexible application (suitable for new and existing buildings because of acceptable space demand), as well as the improvement of solar fraction (extended solar collector utilization time, enhanced collector efficiency), i.e., the reduction of electric energy demand for the heat pump by management of the source and sink temperatures. In order to investigate and optimize the heating system, a dynamic system simulation model was developed. On this basis, a fundamental control strategy was derived for the overall co-ordination of the heating system with particular regard to the performance of the two storage tanks. In a simulation study, a fundamental investigation of the heating system configuration was carried out and an optimization was derived for the system control, as well as the selection of components and their dimensioning. The influence of different parameters on the system performance was identified, where the collector area and the latent heat storage volume were found to be the predominant parameters for system dimensioning. For a modern one-family house of $120m2$ living area with a specific annual heat demand of $60kWh/(m2a)$ for both heating and domestic hot water, a solar collector area of $30m2$⁠, and a latent heat store volume of $12.5m3$ are proposed for the location of Wuerzburg (Germany). In this configuration, the heating system reaches a seasonal performance factor of 4.6, meaning that 78% of the building’s and users’ heat demand are delivered by solar energy. The results show that the solar/heat pump heating system can give an acceptable performance using up-to-date components in a state-of-the-art building.