Use of hydrogen as energy vector: an inherent safety analysis

Hydrogen and hydrogen carrier materials (e.g. hydrides) have received considerable attention in the last decade. However, the hazard related to flammability and high pressure storage is evident. The widespread diffusion on the territory of the future hydrogen facilities and vehicles may lead to severe accidents in highly vulnerable areas. Since hydrogen technologies still need to be developed and implemented, the application of traditional quantitative risk assessment (QRA) techniques is problematic. The present contribution applies a novel consequence-based approach for inherent safety assessment (i.e. analysis of the potential hazards) to the envisaged hydrogen usage and supply system. The proposed approach evaluates a set of Key Performance Indicators (KPIs), accounting for the spatial scale of expected accident consequences and the reliability performance of the equipment. In the approach, inherent safety is assessed in a physically sound and auditable manner, resorting to the application of physical model runs for consequence simulation of reference release scenarios. The KPI method was applied to a number of reference schemes and units, including cars, domestic storage, refueling stations, hydrogen transport trucks, and hydrogen production plants. Several alternative technologies were considered (compressed gas, liquefied, metal matrices hydrides and slurry hydrides). The KPI results were compared identifying the best technologies and pinpointing the potential for performance improvement.