The storage performance of automotive cryo-compressed hydrogen vessels

Abstract

Cryo-compressed hydrogen storage promises to deliver the highest system storage density leading to practical vehicles with range comparable to today's gasoline vehicles and fundamental cost and safety advantages. However, cryogenic vessels are complex systems, continuously drifting in thermodynamic space depending on use patterns, insulation performance, vessel characteristics, liquid hydrogen pump performance, and para-H2 to ortho-H2 conversion. In this paper, cryogenic vessel fill density results from a previous publication are extended to calculate system storage performance, including volumetric (gH2/L), gravimetric (H2 weight fraction), and vent losses over a broad range of conditions. The results confirm previous experiments and models indicating that cryogenic pressure vessels have maximum system density of all available storage technologies while avoiding vent losses in all but the most extreme situations. Design pressures in the range 250–350 bar seem most advantageous due to high system density and low weight and cost, although determining an optimum pressure demands a complete economic and functional analysis. Future insulation, vessel, and liquid hydrogen pump improvements are finally analyzed that, while not experimentally demonstrated to date, show promise of being feasible in the future as their level of technical maturity increases, leading to maximum H2 storage performance for cryo-compressed storage. If proven feasible and incorporated into future cryogenic vessels, these improvements will enable 50 + gH2/L system density at 10+% H2 weight fraction.