Electric Vehicles and Fire Safety

With 2021 in full swing, we say goodbye to a tumultuous year and welcome the exciting challenges that lie ahead.

As we at Sotera look to the future we are considering the way fire engineering is adapting to the fast-changing world around us.

The age of electrified transport is here, and the built environment is changing to adapt to the growing need to power the way we get around. The exponentially growing trend for electric mobility – ranging from compact last-mile personal transport to long range electric vehicles (EV) – is shaping the way we design buildings.

There is a push for new buildings to be electric vehicle ready. Consequently, shared (frequently underground) carparks now contain a growing number of high-capacity Lithium-Ion batteries which fundamentally differ from conventional fuels used in the mobility sector. A characteristic difference is the potential for thermal runaway which can lead to rapid fire propagation and production of asphyxiant gases. This requires us as fire engineers to reassess the associated fire hazard and the way we intend to control or suppress such fires.

Design standards are rarely able to keep up with the cutting-edge; so, are standard sprinkler systems typically installed in basement carparks suitable to control the risk of EVs?

Recent real-scale tests [1] suggest that targeted water-based and gaseous suppression systems appear suitable to control fire growth until brigade intervention is undertaken and the EV can be quarantined. This is further supported by bench-scale testing that was undertaken by Underwriters Laboratories [4] which suggests that targeted mist or gaseous suppression can mitigate flame spread between battery cells. However, standard ceiling sprinklers are not targeted to the affected area, which is shielded from the water spray, preventing water from penetrating the seat of the fire.

The Fire Protection Research Foundation [6] undertook large-scale testing on Lithium-Ion battery racks to assess the effectiveness of standard ceiling sprinklers typical of those installed in underground car parks. The study found that although the ceiling sprinklers reduce the overall fire intensity, they are unlikely to provide adequate cooling to suppress the fire. The ceiling sprinklers were however capable of controlling fire growth and, in combination with adequate physical clearance between battery racks, may prevent fire spread.

More research is required in this arena, but the available information suggests that ceiling sprinklers can provide adequate control of an EV fire until the fire brigade can intervene, and the vehicle can be removed through specialised towing [7] (to avoid reignition that can still occur days later). Staggering of EV parking spaces between internal combustion vehicles may also provide adequate physical separation to avoid catastrophic fire spread. That said, further testing is required to fully validate these assumptions.

At Sotera we can develop specialised and bespoke solutions which assess and adequately mitigate fire hazards that are introduced by our fast-changing world.