Simulation Study on the Performance Assessment of a Direct-Expansion Solar PV/T Coupled Air-Source Heat Pump System for Rural Buildings in Typical Climate Zones of China

The direct-expansion solar photovoltaic/thermal (PV/T) coupled air-source heat pump (ASHP) system is an integrated technology for the combined domestic hot water and electricity supply of rural buildings, but the variation in its performance across climate zones limits confidence in its large-scale deployment. In this study, a TRNSYS 18 model was established and validated against experimental data, with all mean bias errors (MBE) within ±10%, satisfying ASHRAE Guideline 14-2014. Annual simulations were performed for five representative cities of the building climate zones of China: Harbin (severe cold), Beijing (cold), Shanghai (hot-summer cold-winter), Fuzhou (hot-summer warm-winter), and Kunming (mild). Compared with the standalone ASHP system, the COP of the PV/T-ASHP system increases by 13.94–30.64% when the PV/T evaporator is in operation, with the most pronounced improvement in the severe-cold zone. The annual power generation of the PV/T system is 25.08–33.95% higher than that of the conventional PV system, with an annual mean electrical efficiency of 19.53–21.67%; the annual useful heat production ranges from 78,406.31 MJ (Harbin) to 110,656.16 MJ (Kunming), and the primary energy saving ratio reaches 66.27–74.57%. The system exhibits superior comprehensive energy performance in all climate zones. This study provides technical guidance for climate-specific application and optimal configuration, and proposes improvement measures for cold and severe cold regions.