Against the background of climate change, the reduction of greenhouse gases in the transport sector is increasingly coming to the fore. At present, electrically operated and in particular battery-powered vehicles (BEV) are of great importance.

Although cars with fuel cells (FCEV) do not yet have a significant market share, this could change soon in view of the imminent problems of battery-powered vehicles. New vehicles with H₂ drive are used both in passenger cars and in local public transport. The latter covers the entire range of vehicle types with city buses, passenger trains and trams. But what about their safety?

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Fires in vehicles happen every day, even if it is currently only the BEVs that “make it” to the headlines. The fact that the fire behaviour of a lithium-ion battery differs from that of petrol or diesel is just as obvious as the fact that the hydrogen used to power a fuel cell poses completely different risks. In particular, the high operating pressure at which hydrogen is carried in vehicles and which, depending on the application, is 350 bar or 700 bar, harbours the danger of a fire event unknown to conventional vehicle engines: jet fire.

A jet fire occurs when combustible gas escapes from a container through a small opening and is ignited on contact with ambient air. Depending on the pressure inside the container and the size of the opening, jet flames with a length of several metres can occur for a short time. An additional risk is posed by an urban environment: Underground facilities, such as tunnels, multi-storey car parks, bus and train stations, generally require special conditions for fighting fires and ensuring the safe escape of people. Like the new drive technologies, these are part of a modern infrastructure, so that safety issues should be taken into account when planning new and upgrading existing infrastructure as well as when designing vehicles.

Research project SUVEREN

Can the same safety regulations continue to apply in the City Tunnel in the future if most hydrogen-powered vehicles pass through it? Since mid-2017, the SUVEREN project, funded by the Federal Ministry of Education and Research (safety in underground urban transport sector using new energy sources), has been dedicated to answering these and other questions. In this project, Fogtec Brandschutz GmbH & Co. KG, the study company for tunnels and traffic facilities e.V. (STUVA) and the Federal Institute for Materials Research and Testing (BAM) are to investigate the effects of fires with new energy sources when the vehicles are in underground facilities.

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read more in H2-international July 2019

Authors: Rajko Rothe, Lic.Tech, M.Sc. Max Lakkonen
both from Ingenieure für angewandte Brandschutzforschung GmbH, Berlin, Germany