Field experimental investigation on electricity and thermal performances of a large scale photovoltaic solar-thermal direct expansion heat pump system

The comprehensive utilization of photovoltaic and solar-thermal (PVT) is an important approach to achieve the carbon peaking and carbon neutrality goals, and can realize the generation of electricity and thermal energy cleanly and efficiently. In order to satisfy the basic living demands including electricity, space heating and do-mestic hot water of Chinese rural residents, a large scale direct expansion PVT heat pump (DX-PVT-HP) system used plate-tube evaporator has been proposed in the present paper. An experimental platform with a solar panel installation area of 32.47 m2 is installed on the roof of a dormitory in Hefei, and its operation characteristics including electricity and thermal performance are field tested and analyzed in winter. The data indicates that during the operation of the heat pump, the cooling effect of the plate-tube evaporator on the solar panel can maximum increase the photoelectric conversion efficiency by 25.0% in comparison with that of the conventional solar panel. In the process of heating 1500 L water from 5.5 degrees C to 45 degrees C on a sunny day, the average coefficient of performance (COP) of the system reaches 4.96, and the power generation of the system is greater than the power consumption. Finally, the concept of equivalent net thermal energy is proposed to unify the output of electricity and thermal energy to evaluate the comprehensive performance of the system. The results demonstrate that it is feasible to adopt the designed PVT heat pump system to meet the basic living needs of rural residents.