Fire Performance of Power Optimizers in Photovoltaic Systems

This study investigates the behaviour of photovoltaic (PV) systems with power optimizers under externally induced fire exposure, with a particular focus on facade-mounted installations. The objective is to determine whether power optimizers increase fire risk due to energy absorption at various abnormal operating temperatures and how the system behaviour of a PV installation with power optimizers responds to elevated external temperatures. Experimental investigations were conducted on grid-connected PV systems consisting of inverters, power optimizers, and PV module simulation sources. Devices from three manufacturers were analysed: Huawei, SolarEdge, and Tigo. Two types of experiments were performed: (I) non-destructive heating up to 140 °C, and (II) destructive flame exposure at temperatures of at least 800 °C. In both cases, one optimizer within the PV system was exposed to abnormal temperature. The results show that power optimizers detect overtemperature, stop energy conversion, and switch to bypass mode on the string side while opening the module side. After cooling, devices resume operation even with visible damage. Under destructive flame tests, burning droplets, enlarged flames, smoke, and moving burning parts were observed due to melting brackets. No Rapid Shutdown of system voltage occurred, although string current was interrupted by the inverter. Overall, PV systems with power optimizers exhibit similar behaviour to systems without optimizers during fire, but additional material increases the fire load.