Stationary LH2 storage vessels have an inner wall that contains the fluid, an outer wall exposed to ambient conditions, and an evacuated volume between the walls (akin to a Thermos bottle) [1]. A high level of vacuum must be created and maintained between the walls to ensure adequate thermal performance. Insulation is generally used in the evacuated space to further reduce heat transfer to the inner tank wall. Commonly used insulation types—ordered in increasing thermal performance in a high-vacuum environment—include aerogels, perlite, glass bubbles, and multilayer insulation.
This double wall dewar construction, also referred to as “vacuum-jacketed,” is needed for most mobile applications to achieve an acceptable boil-off rate and to meet other system requirements. Vacuum-jacketed piping, valves, and connections are also used to minimize heat load during transfer and other LH2 operations.
Typical inner wall materials compatible with LH2 service include 300-series stainless steel and aluminum alloys. Composite formulations are currently under development as a lighter-weight option to achieve higher mass fraction LH2 storage. Airbus and the Royal Netherlands Aerospace Centre are developing composite LH2 dewars for aircraft. Gloyer-Taylor Laboratories is also developing single- and double-walled composite storage vessels for a variety of applications. Conformable tanks for improved form factor integration, as well as additive manufacturing techniques, are being developed by various organizations [2].