Influence of shadow on shunt-type potential-induced degradation for crystalline Si photovoltaic modules exposed outdoors

Potential-induced degradation (PID) was observed for crystalline Si photovoltaic (PV) modules set at a PID test system constructed outdoors. It was clearly shown that partial shadow and periodical water spray during daytime accelerate PID generation. PID easily occurred just underneath the shielding plate. It was also found that when a large part of one cell in the PV module was shadowed, PID is accelerated; however, when a small part of one cell in the PV module was shadowed or when the weak light is uniformly irradiated, less PID acceleration is observed. Simulation was also carried out for discussing the influence of light irradiation. These findings suggest that UV irradiation during the PID indoor test is essential for the exact estimation of the acceleration factor of the indoor PID test. (C) 2020 The Japan Society of Applied Physics