Comparative risk analysis of aqueous formate solutions and compressed hydrogen storage: Safety and scalability assessment

This work investigates the safety performance of low-pressure aqueous formate solutions as an alternative hydrogen storage strategy, comparing them with conventional high-pressure compressed hydrogen tanks. Quantitative consequence analyses were performed using PHAST 9.0, considering both continuous and catastrophic release scenarios across a wide range of vessel volumes and operating pressures. The results show that aqueous systems exhibit markedly reduced hazard distances in dispersion, jet fire, fireball, and explosion events, primarily due to the dilution effect of water vapor, which lowers the calorific value and radiant efficiency of hydrogen, and lower release pressure. In particular, the 50% fatality threshold was never reached for aqueous storage cases, while compressed hydrogen consistently produced severe consequences that scaled with vessel size. Moreover, volume scale-up of aqueous formate tanks displayed a saturation trend, indicating increasing industrial scalability without proportional escalation of risk. Furthermore, in accidental release scenarios at near-ambient temperature and pressure, hydrogen generation is kinetically limited and concentrations remain below the lower flammability limit, confirming intrinsically safe behavior under normal operating conditions. These findings highlight the inherent safety advantages of aqueous formate solutions, supporting their potential as safer hydrogen carriers for large-scale applications.