Simulation analysis of a photovoltaic/thermal-air dual heat source direct-expansion heat pump

A new type of photovoltaic/thermal air evaporator based on micro heat pipe arrays and a dual heat source direct-expansion heat pump system were developed to utilize the flat heat pipes and strengthen the complementary utilization of solar and air energy within a limited component area. This system can realize the function of dual heat source utilization while generating photovoltaic power. A simulation program of the heat pump system was established. The influence of environmental conditions on the comprehensive performance of the system was analyzed, and the operation strategy and optimization methods were summarized by numerical and exergy analyses. The average COPh values of the solar/air and solar modes were 1.42–3.44 and 1.44–3.42 under calculation conditions, respectively. The system performed well in the two modes, indicating that it can effectively utilize dual heat sources. The system's operation strategy was determined. When the irradiation exceeds the critical solar irradiation, the system runs in solar/air mode, otherwise it runs in solar mode. The exergy loss mainly concentrated in the evaporator and compressor, and the sum of the two accounted for 69.1%–83.9%. The analysis suggests that increasing the heat transfer area on the air and R22 side is the direction of system optimization.