Dynamics of cryogenic hydrogen storage in insulated pressure vessels for automotive applications

A dynamic model is used to characterize cryogenic H2 storage in an insulated pressure vessel that can flexibly hold liquid H2 and compressed H2 at 350 bar. A double-flow refueling device is needed to ensure that the tank can be consistently refueled to its theoretical capacity regardless of the initial conditions. Liquid H2 charged into the tank is stored as supercritical fluid if the initial tank temperature is >120 K and as a subcooled liquid if it is <100 K. An in-tank heater is needed to maintain the tank pressure above the minimum delivery pressure. Even if H2 is stored as a supercritical fluid, liquid H2 will form as H2 is withdrawn and will further transform to a two-phase mixture and ultimately to a superheated gas. The recoverable fraction of the total stored inventory depends on the minimum H2 delivery pressure and the power rating of the heater. The dormancy of cryogenic H2 is a function of the maximum allowable pressure and the pressure of stored H2; the evaporative losses cannot deplete H2 from the tank beyond 64% of the theoretical storage capacity.