Multilayer Thermal Model for Evaluating the Performances of Monofacial and Bifacial Photovoltaic Modules

This article aims to present a novel mono-dimensional multilayer mathematical model apt to estimate the temperature of photovoltaic (PV) cells for both monofacial and bifacial PV modules. A dynamic three-layer model (3L-NM) has been developed, in which the contribution of solar radiation that hits the back of the PV module is included. The model is constituted by energy balance equations, one for each layer of the PV module. The input data of the proposed model are the environmental weather conditions as well as the withdrawal electrical power. The outputs are the average temperature of each layer, so it is possible to determine the PV cell temperatures that typically cannot be directly measured. With the purpose to investigate the reliability of the proposed model, the numerical results have been compared with experimental data. Finally, a sensitivity analysis has been performed to evaluate the impact of solar radiation in the back of the PV module considering the different wind speed, as well as the operating electrical points (open circuit and maximum power point). From the statistical analysis, correlation values of 0.993 and 0.990 were obtained, PE values equal to 0.718% and 0.161%, respectively, for the monofacial and bifacial module. The sensitivity study shows that the solar radiation on the backside of the module has a greater impact on the bifacial module, infact, when the contribution of back is included in a model, temperature differences up to 5.2 °C for bifacial and 1.0 °C for monofacial module at 1000 W/m2 were observed.