Study of operation performance for a solar photovoltaic system assisted cooling by ground heat exchangers in arid climate, China

Photovoltaic power generation application with advantages of sustainability and low emission is limited on its low photovoltaic (PV) efficiency mainly due to high panel temperature. In this paper, a solar photovoltaic system coupled by ground heat exchangers (PV-GHEs system) is proposed to reduce the operation temperature of panels and keep a high PV efficiency. Taking Tikanlik with typical arid climate of northwestern China as an example, a numerical model based on the software TRNSYS is built and its reliability are validated based on an actual thermal response test data. The simulation results show that the PV-GHEs system can reduce the panel temperature by 26.8% and increase the annual electricity yield by 7.9%, compared with conventional PV systems. Sensitivity analysis highlights the influences of environmental, geological and design parameters on the system performance. For the long-term operation, a gradually growing ground temperature is unfavorable and may weaken the heat transfer between GHEs and the surrounding ground. For the case of Tikanlik, the growing rate of the ground temperature is 0.67 °C per year and a minimum distance of 10 m between boreholes is recommended when more GHEs are needed. Finally, a life cycle cost analysis of the PV-GHEs system is investigated.