Design Challenges and Modeling for An Efficient Liquid Hydrogen Storage Tank for Autonomous Systems

Liquid hydrogen (LH₂) is an attractive fuel for autonomous systems because of its high specific energy and energy density.  When combined with a high efficiency fuel cell or engine, LH₂ offers long endurance.  The design of an LH₂ storage system which is both efficient and safe presents challenges due to the low (cryogenic) temperature of LH₂, the high permeability of H₂, and constraints imposed by the vehicle requirements.  Common vehicle requirements include low weight and high density storage of the fuel, safe fueling and operation, the ability to support transients in the gaseous H₂ withdrawal rate as the power load changes, and sufficient strength to resist stresses from vehicle dynamics.  These design challenges are addressed by modeling and simulation.  Specifically, heat transfer models are used to design insulation and transfer lines, load-data-based simulations are used to design a fuel delivery system to accommodate the expected transients, finite element models are used for structural analysis, and a coupled heat transfer/flow model is used for safety analysis.  All four modeling and simulation efforts are validated by experiments.