Hazard footprint of alternative fuel storage concepts for hydrogen-powered urban buses

Hydrogen mobility is a powerful strategy to fight climate change promoting the decarbonization of the transportation sector. However, the higher flammability of hydrogen in comparison with traditional fuels raises issues concerning the safety of hydrogen-powered vehicles, in particular when urban mobility in crowded areas is concerned. In the present study, a comparative analysis of alternative hydrogen storage concepts for buses is carried out. A specific inherent safety assessment methodology providing a hazard footprint of alternative hydrogen storage technologies was developed. The approach provides a set of ex-ante safety performance indicators and integrates a sensitivity analysis performed by a Monte Carlo method. Integral models for consequence analysis and a set of baseline frequencies are used to provide a preliminary identification of the worst-case credible fire and explosion scenarios and to rank the inherent safety of alternative concepts. Cryo-compressed storage in the supercritical phase resulted as the more hazardous storage concept, while cryogenic storage in the liquid phase at ambient pressure scored the highest safety performance. The results obtained support risk-informed decision-making in the shift towards the promotion of sustainable mobility in urban areas.