Quantitative Risk Assessment Models for Extinguishing and Controlling Hydrogen Fires and Explosions Across the Hydrogen Energy Cycle

Abstract

Hydrogen is widely regarded as a clean energy carrier for decarbonising mobility and stationary power, yet its wide flammability range, low ignition energy and high flame speed make fire and explosion the governing hazards across the supply chain. This study develops and applies a quantitative risk assessment (QRA) framework to estimate, evaluate and control fire and explosion risks for seven representative objects spanning the hydrogen energy cycle: a solar hydrogen production plant, a liquid-hydrogen (LH2) depot, a fuelling station, an on-board vehicle tank, a fuel-cell combined heat and power (CHP) unit, a road tanker and a gaseous-hydrogen (GH2) pipeline. Accident scenarios were identified using HAZOP and FMEA. Event frequencies were derived from a combined fault-tree and event-tree analysis (FTA/ETA) with lognormal basic-event data propagated through 10,000 Monte-Carlo trials, while road-transport and pipeline frequencies were obtained from historical accident statistics. Physical consequences—dispersion, jet fire, pool fire, fireball, flash fire and vapour-cloud explosion—were simulated with PHAST Professional v6.4 (DNV) and converted to fatality levels using thermal-radiation and overpressure probit relations. Individual and societal (F-N) risks were benchmarked against the ALARP/ALARA acceptance criteria and against an equivalent liquefied-petroleum-gas (LPG) study. Continuous releases dominated loss of containment (~94%), with tank overpressure as the leading initiator (~50%); fires accounted for ~60% of outcomes and explosions ~5%. The overall societal risk of the hydrogen cycle was 8.5 × 10−3/year, dominated by the fuelling station (39%) and the on-board vehicle tank (35%). Although individual risks for hydrogen storage exceeded those of LPG, the maximum effect distances and societal risks were consistently smaller, indicating that hydrogen poses a lower public risk than LPG of comparable tank size. The framework identifies critical weak points and prioritised risk-reduction measures for the safe deployment of hydrogen infrastructure