Performance study of solar assisted heat pump using phase change slurry as heat exchange medium

Comparison of cumulative heating capacity and heating rate . • A novel solar phase-change slurry direct-evaporation PV/T heat pump system was proposed; • A test system was constructed to verify its feasibility; • PCS was used to directly heat the evaporator, achieving an average heat pump COP of 4.67; • Experimental operations demonstrated average heat collection and power generation efficiencies of 74.77% and 15.53%, respectively; • A method for enhancing both the efficiency and stability of the heat pump cycle was identified. The use of n-octadecane phase change slurry (n-PCS) as a heat storage, heat transfer, and heat release medium in indirect expansion photovoltaic/thermal (PV/T) heat pump system aims to simultaneously enhance solar energy conversion efficiency and heat pump cycle performance. A solar n-PCS direct evaporation PV/T heat pump system is proposed. In this system, n-PCS serves as a heat storage, heat transfer, and heat release medium, linking the evaporator with the PV/T collector. The PV/T heat pump system achieves a high-power generation capacity, with an average output of 189.85 W, while also maintaining stable electricity production. During operation, the maximum heat collection and power generation efficiencies reach 86.82 % and 26.82 %, respectively, with average efficiencies of 74.77 % and 15.53 %. In the heat pump cycle, n-PCS releases latent heat to maintain a high and steady evaporation temperature for evaporator heating, enhancing both the cycle efficiency and stability. During the experiment, the average and instantaneous heat pump coefficients of performance (COPs) reached 4.67 and 6.34, respectively. The maximum and minimum hybrid COP s were 14.86 and 4.33, respectively, demonstrating consistent system stability throughout operation.