Investigation on a direct-expansion solar-assisted heat pump with a novel hybrid compound parabolic concentrator/photovoltaic/fin evaporator

The evaporator of a traditional photovoltaic solar-assisted heat pump generally covers a large area to meet the heating demand and the performance is poor under low or no irradiation. Many scholars connected an additional finned-tube evaporator in series or parallel to solve the problem, adding additional pipelines. Besides, the heat collection of the plate photovoltaic is still not improved. Thus, a novel direct-expansion solar-assisted heat pump with a hybrid compound parabolic concentrator/photovoltaic/fin evaporator (CPC/PV/fin-SAHP) is proposed in this paper. The newly established system can make full use of solar and air energy in a limited space to achieve a much higher unit output. The mathematical model is established and validated in MATLAB. The investigation on the impact of water temperature, wind speed, irradiation, as well as ambient temperature has been completed. Additionally, a comparison among the novel hybrid heat pump, traditional air-source heat pump, and photovoltaic heat pump has been conducted. Results show that the irradiation and the wind speed are beneficial for the coefficient of performance, but the water temperature is not. When irradiation is 200 W/m2 and above, the novel system is the best in coefficient of performance, total output, and exergy efficiency. Even without irradiation, the coefficient of performance of the novel system could be 4.08 while that of the traditional photovoltaic heat pump is only 1.69. Thus, the proposed system can greatly improve the performance of traditional heat pumps, inspiring the design of high-efficient heat pumps with limited space.