Wind-driven smoke dispersion in rooftop photovoltaic fires: An experimental investigation with helium smoke

Abstract

In 2022, global photovoltaic (PV) deployed capacity increased by 240 GW, reaching a cumulative capacity 1.185 of terawatts, accompanied by anticipated 34,247 PV-inducted fires. The dispersion of fire smoke from rooftops with PVs raises significant safety concerns regarding residents’ exposure. Therefore, it is essential to investigate the phenomenon of smoke dispersion generated by rooftop PV fires, particularly through rooftop openings such as skylights. However, there are limited studies on this topic in the literature. This study conducts small-scale tests in a wind tunnel to examine rooftop PV fire smoke dispersion using a novel smoke-helium similarity and scaling law. A parametric analysis is carried out, aiming to guide the fire protection design of the building. It examines the smoke dispersion generated from rooftop PV fires, considering a variety of rooftop angles, incoming wind velocities, as well as heat release rates (HRR). According to the findings, residents exposed to rooftop PV fire smoke must evacuate within 4 min. Moreover, descending to lower levels may not be a safe means of escape. The scenario with a 15° rooftop angle is deemed fatal. Conversely, rooftop angles of 45° and 60° are considered the most reliable layout for rooftop PV. As incoming wind velocity decreases from 7.75 m/s (full-scale 30 m/s) to 2.58 m/s (full-scale 10 m/s), smoke dispersion increases across the rooftop opening (e.g., skylight) as the rooftop angle increases from 0° to 30°. Smaller HRRs of rooftop PV fires correspond to more reliable fire protection.