Quantitative Risk Assessment of an Indoor Hydrogen Dispenser Using HyRAM+
The use of hydrogen as an energy carrier has gained widespread adoption in warehouses and industrial environments. This increasing adoption necessitates the need for stringent safety evaluations specifically for enclosed fueling systems where the potential of accidental discharges may result in explosions or jet fires. This study demonstrates a quantitative risk assessment of an indoor hydrogen dispenser positioned in a warehouse facility using the Hydrogen Risk Assessment Models (HyRAM+) version 6.1 software developed by Sandia National Laboratories. A representative 120 m x 120 m x 10.62 m housing a 70 MPa gaseous hydrogen dispenser used in the refueling of hydrogen-powered vehicles in an enclosed space scenario was modeled Based on realistic industry standard assumptions system geometry conditions of operation and component inventory were defined. HyRAM+ was employed to evaluate deterministic and probabilistic models to determine potential loss of life (PLL), fatal accident rate (FAR), and average individual risk (AIR). The PLL, FAR, and AIR values of 1.05 x 10-4 fatalities per year 0.02 fatalities per 100 million working hours and 5.99 x 10-7, respectively indicate negligible individual risk under the modeled conditions. Additionally flame and leak analysis revealed smaller sizes of leaks being likely to result in no ignition and safe shutdown with larger leak size resulting in the probability of explosion or jet fire. Furthermore radiative heat flux analysis of a 6.223 mm leak also revealed the occurrence of peak heat flux along the jet axis with a decrease in distance demonstrating that thermal exposure is highly directional. These findings demonstrate that the assessed indoor hydrogen dispenser operates within acceptable safety limits and highlight the effectiveness of HyRAM+ as a tool for hydrogen safety designs.