Thermal model of bifacial silicon photovoltaic modules with different backsheets under outdoor conditions

Bifacial silicon photovoltaic (PV) modules have obvious advantages in energy production compared to monofacial silicon PV modules because of the excess gain due to irradiance from the rear side. The double transparent material structure of bifacial modules improves the long-term durability compared to traditional glass-backsheet modules. In this paper, the thermal characteristics of both double glass (GG) and glass-transparent material (GT) bifacial modules are mathematically studied, and the limitation of former thermal models that determined the operating temperature without considering the bifaciality and rear irradiance factors is noted. After adding bifaciality and rear irradiance parameters into the new model, 2 groups of 32 bifacial PV modules were chosen to conduct indoor and outdoor tests from 1(st) Jan 2020 to 31(st) Dec 2020 in Yinchuan, China. Based on the whole year outdoor measured data, the operative transfer coefficients in the new model were iteratively computed through MATLAB for the optimized values under minimization of the root mean square error (RMSE). The results of the new model fit perfect well with the measured data for both the GG and GT modules, with RMSEs of 2.678 and 2.543, respectively. To verify the adoption of the new model under different conditions, four types of typical weather were analyzed, and the minimum RMSEs were 1.238 and 1.149 under median irradiance weather.