As the world shifts towards cleaner energy solutions, hydrogen stands out as a promising renewable resource, being the most abundant element in our known universe. Hydrogen fuel cells (PEM) utilize hydrogen and oxygen to produce electricity and are considered zero-emissions, producing only water as a byproduct. This places hydrogen at the forefront as a viable solution for reducing emissions.
While Electric Vehicles (EVs) have dominated the spotlight, hydrogen Fuel Cell Electric Vehicles (FCEVs) are emerging as another viable alternative to traditional combustion engines[1]. FCEVs offer comparable refueling times and range to Internal Combustion Engine (ICE) vehicles and exceed the capabilities of many currently available EVs. As hydrogen production, storage, and infrastructure continue to develop, FCEVs are becoming increasingly viable, particularly for heavy-duty transport and long-haul applications.
As with any new technology, safety discussions are crucial to understanding the unique risks of hydrogen fuel cells. Although hydrogen itself is highly flammable, it disperses quickly and burns upward if fully released, due to hydrogen being approximately 14 times lighter than air. This dispersion helps to limit the spread of fire. However, small leaks from hydrogen fuel cells can lead to fires that last longer than if fully released[2]. Hydrogen has good energy density (energy per kg), which, while positive for FCEVs, poses unique challenges in fire scenarios. A recent study demonstrated that fires in hydrogen FCEVs can expose nearby structures to gases reaching temperatures of 800°C for over 13 minutes[3]. For comparison, pure aluminum has a melting point of approximately 660°C. While 13 minutes may sound like a long duration of sustained heat, EV fires, with lithium-ion batteries vulnerable to thermal runaway, may last for days and re-ignite. However, the temperature of lithium-ion battery fires in EVs due to thermal runaway is around 500°C[4], which is of much lower intensity than the shorter-duration hydrogen FCEV fires.
Additionally, unlike EV and ICE fires, which produce heavy smoke detectable by standard alarms, hydrogen fires are nearly invisible, emitting no smoke or soot and radiating little heat[2]. This makes hydrogen fires much more difficult to detect and control with traditional fire safety systems and design methodology. As a result, fire safety systems for FCEVs will require different strategies from those used for ICE vehicles and EVs to ensure rapid detection and prevention of potentially prolonged fires.
At Sotera, we are committed to ensuring the safety of all vehicles in public and private spaces. In considering the hazards associated with hydrogen vehicle fires, we are developing fire safety measures for car parks, including advanced detection systems tailored for hydrogen and EV risks. With these strategies, we aim to create safer environments as we move towards a sustainable, zero-emission future.
Reference:
[1] Pramuanjaroenkij, A. and Kakaç, S., 2023. The fuel cell electric vehicles: The highlight review. International Journal of Hydrogen Energy, 48(25), pp.9401-9425.
[2] Ringland, J.T., 1994. Safety issues for hydrogen-powered vehicles.
[3] Kang, S., Lee, K.M., Kwon, M., Lim, O.K. and Choi, J.Y., 2022. A quantitative analysis of the fire hazard generated from hydrogen fuel cell electric vehicles. International Journal of Fire Science and Engineering, 36(2), pp.26-39.
[4] Chen, H., Buston, J.E., Gill, J., Howard, D., Williams, R.C., Vendra, C.M.R., Shelke, A. and Wen, J.X., 2020. An experimental study on thermal runaway characteristics of lithium-ion batteries with high specific energy and prediction of heat release rate. Journal of Power Sources, 472, p.228585.