Risk Assessment of Rooftop-Mounted Solar PV Systems

This paper discusses the issues encountered by design engineers due to the lack of a method specified in IEC 62305-2 to conduct the risk assessment only for the solar PV system mounted on a part of a large roof. Typically, the Solar PV system provider is a party independent from the building contractor and the building owner, thus, they would be interested only in the protection of the PV system rather than the total building. On the other hand, a lightning strike to the parts of the roof beyond the PV panel may also affect the PV system due to fire hazards and injected (or induced) current into the power system. Thus, it may not be advisable to consider only the part of the building with a PV panel as an isolated system. In this study we first show the difference in the risk level by conducting the risk assessment for a hypothetical case of a roof-mounted solar PV system, considering the entire building and the part of the building with PV panel on the rooftop as an isolated structure in the presence of the other parts. The computations show a significant difference in the outcomes for the two cases. We also discuss other methods adopted by lightning protection professionals in the region in computing the lightning risk for roof-mounted solar PV systems. The key objective of this study is to demonstrate the confusion concerning this subject rather than proposing a solid methodology for conducting the risk assessment for roof-mounted solar PV systems. It is of prime importance for the working groups of standards committees to come to an agreement in this regard.