CFD analysis of fast filling strategies for hydrogen tanks and their effects on key-parameters

A major requirement for the filling of hydrogen tanks is the maximum gas temperature within the vessels during the process. Different filling strategies in terms of pressure and temperature of the gas injected into the cylinder and their effects on key parameters like maximum temperature, state of charge, and energy cooling demand are investigated. It is shown that pre-cooling of the gas is required but is not necessary for the whole duration of the filling. Relevant energy savings can be achieved with pre-cooling over a fraction of the time. The most convenient filling strategy from the cooling energy point of view is identified: with an almost linear pressure rise and pre-cooling in the second half of the process, a 60% reduction of the cooling energy demand is achieved compared to the case of pre-cooling for the whole filling.