IN-24-C022 - Investigation of Fire Hazard Mitigation, Control and Ventilation for Battery Electric Bus Fire in Enclosed Vehicular Facility

A growing number of transit authorities are pursuing zero emission transition of their bus fleets, particularly to battery electric buses (BEBs). Concerns arise for BEB fires due to their high energy density lithium-ion battery technology and potential for thermal runaway. The fire risk and hazard associated with a BEB fire become substantially larger due to their higher onboard battery energy capacities and more combustible material. This is magnified in typical enclosed vehicular charging, parking, and maintenance facilities, such as bus depots where large numbers of vehicles with very high-capacity batteries are densely parked, with many charging simultaneously. There is currently limited guidance available from fire safety codes and standards as to appropriate design criteria and fire mitigation options for enclosed vehicular facilities that will host BEBs. This study investigates a BEB fire in an enclosed vehicular facility. The use of water-based fixed firefighting system with different water application rates and emergency exhaust ventilation systems are investigated to mitigate fire spread to adjacent parked BEBs or infrastructure. Various bus separation distances are explored to determine an appropriate bus spacing that could minimize fire spread. Economical fire mitigation options including separation barriers and fire curtain are also explored. The study uses computational modeling to provide quantitative analysis and thermal exposure prediction of this unique fire hazard, outcomes of which could help establish a leading technical approach for analyzing and designing safe enclosed vehicular infrastructure and facilities.