Risk Assessment and Mitigation Evaluation for Hydrogen Vehicles in Private Garages. Experiments and Modelling

Governments and local authorities introduce new incentives and regulations for cleaner mobility, as part of their environmental strategies to address energy challenges. Fuel cell electric vehicles (FCEVs) are becoming increasingly important and will extend beyond captive fleets, reaching private users. Research on hydrogen safety issues is currently led in several projects in order to highlight and manage risks of FCEVs in confined spaces such as tunnels, underground parkings, repair garages, etc. But what about private garages - that involve specific geometries, volumes, congestion, ventilation? This study has been carried out in the framework of PRHyVATE JIP project, which aims at better understanding hydrogen build-up and distribution in a private garage. The investigation went through different rates and modes of ventilation. As first step, an HAZID (Hazard Identification) has been realized for a generic FCEV. This preliminary work allowed to select and prioritize accidental release scenarios to be explored experimentally with helium in a 40-m3 garage. Several configurations of release, ventilation modes and congestion – in transient regime and at steady state – have been tested. Then, analytical and numerical calculation approaches have been applied and adjusted to develop a simplified methodology. This methodology takes into account natural ventilation for assessment of hydrogen accumulation and mitigation means optimization. Finally, a global risk evaluation – including ignition of a flammable hydrogen-air mixture – has been performed to account for the mostly feared events and to evaluate their consequences in a private garage. Thus preliminary recommendations, good practices and safety features for safely parking FCEVs in private garages can be proposed.