Analysis of Unintended Hydrogen Releases from a Fuel Cell Tram

Abstract

Hydrogen is a promising alternative energy carrier, and its application in the industrial field, especially in the transportation sector, is increasing through fuel cells to power vehicles. Hydrogen fuel cell vehicles are typically equipped with high-pressure on- board storage tanks. Due to the low volumetric energy density of hydrogen, these tanks are relatively large to provide a comparable range to current fossil fuel vehicles. Therefore, hydrogen is also suitable for large and heavy vehicles, as they have more space than passenger cars. However, accidental hydrogen leakage from high-pressure containers can have serious consequences. Therefore, in-depth research on hydrogen safety issues is necessary to promote the popularization and commercialization of hydrogen energy. CRRC plans to use hydrogen to power urban rail transit systems to reduce the demand for urban electricity supply. This study modeled hydrogen leakage and diffusion in the scenario where the on-board storage tank of a fuel cell tram is placed inside the carriage, including both stationary and moving scenarios. The results show that upward leakage will form a flammable cloud above the tram roof, and when hydrogen diffuses inside the carriage, the hydrogen concentration in the front part of the carriage is higher than that in the rear part. Compared to the stationary situation, vehicle movement will accelerate the diffusion of hydrogen from inside to outside the carriage and significantly reduce the mass of the flammable cloud formed. Additionally, the volume of the flammable cloud will decrease as the vehicle speed increases. This work provides guidance for the placement of hydrogen storage tanks and the structural design of fuel cell trams.