Annual performance analysis of solar-assisted raw-water source heat pumps at low water temperatures

With the increase in energy consumption for building heating and cooling, raw-water source heat pumps (RWSHPs) have garnered strong attention because of their advantages of high efficiency and utilization of a clean heat source. However, RWSHPs exhibit poor performance at low water source temperatures. Thus, this study proposes a solar-assisted raw-water source heat pump (SA-RWSHP) to solve the performance degradation of RWSHPs. The SA-RWSHP can improve performance during the heating period by elevating the entering water temperature (EWT) using solar collectors. During the cooling period, a solar heat source can be used to produce domestic hot water. Optimal design parameters are determined by analyzing the performance of SA-RWSHP using the TRNSYS. Additionally, the performance of SA-RWSHP is compared with that of RWSHP. During the heating period, the unit COP (COP_hp) of SA-RWSHP was 12.7% higher than that of RWSHP on average, owing to the increase in the EWT. Furthermore, the annual total system COP of SA-RWSHP was approximately 18% higher than that of RWSHP owing to the high COP_hp and effective use of solar energy. Overall, the SA-RWSHP exhibited superior performance throughout the year, resulting in a substantial reduction in building energy consumption.