Experimental study on the performance of a photovoltaic/thermal-air dual heat source direct-expansion heat pump

Abstract A new type of photovoltaic (PV)/thermal (PV/T) air evaporator based on micro heat pipe arrays (MHPAs) and a PV/T air dual heat source direct-expansion heat pump system that can achieve heating, refrigeration, and PV power generation were developed. System performance was experimentally investigated. Results showed that the MHPAs exerted a significant cooling effect on the PV modules, which were cooled by 31.6 °C under the experimental conditions, with a low longitudinal temperature difference of 2.1 °C. The increase in PV efficiency was 5.3%. The evaporator can receive heat from solar energy and air energy under appropriate ambient temperature, and the average heat collection efficiency was 106.1%. The average heating coefficients of performance (COP) of the heat pump in solar (S), combined solar and air (SA), and air (A) modes were 2.8, 2.1, and 2, respectively, under typical heating conditions during winter. Average PV efficiency values in S and SA modes were 13.3% and 6.8%, respectively. The average cooling COP was 2.2 and the average PV efficiency was 11.2% under typical cooling conditions during summer. The performance difference and control strategy in various modes and seasons were summarized. This research provides data to support the practical application of heat pump systems.