The Study on Micromismatch Losses of the Bifacial PV Modules Due to the Irradiance Nonuniformity on Its Backside Surface

Compared with monofacial photovoltaic (PV) modules, the output power of bifacial modules is higher since they can utilize additional sunlight of backside. Therefore, the backside irradiance distributions have a great influence on the performance of the bifacial modules. In this article, the backside irradiance distributions of the bifacial PV modules were studied according to the view factor models. Based on irradiance nonuniformity of the PV module backside and single diode model of solar cell equivalent circuit, the micromismatch losses were calculated by the IV curve superposition method. In addition, simulations and experiments of the backside irradiance nonuniformity is designed in Changzhou, China, to verify the theoretical calculation model. According to simulation and experiment result, the micromismatch losses of bifacial modules under different conditions (including grassland, cement floor, snowfield, with and without crossbeam) were analyzed. In the simulation, the micromismatch loss of bifacial PV module in PV system is less than 3%, which depends on field surrounding ground of PV modules. The losses in grassland, cement floor, snow ground is 0.3%-0.5%, 0.5%-1%, 1%-3%, respectively. Due to the shadows of PV module mounting frame, the micromismatch loss will increase by 0.5%-3.3%.