H2 storage methods
Hydrogen can be compressed and held under very high pressures, or liquefied and held at cryogenic temperatures. Compression and cryogenic refrigeration increase H2 energy density per unit of volume, but both are energy-intensive operations, and the vessels for both must be made of materials that can withstand high pressure and prevent hydrogen loss via permeation. The resulting robust containers don’t “package” well in commercial trucks, let alone on passenger cars. Further, the cryo option requires continuous energy input to keep hydrogen at -253°C. In the world of ground transportation, it’s impractical for any use other than large-scale H2 storage at vehicle refueling stations.
A third option would be quite welcome in automotive circles. It’s technically possible to store hydrogen in a solid state at, notably, room temperature and normal atmospheric pressure. The method involves absorption or adsorption of hydrogen into certain metal halides. This method, however, is fraught with challenges and remains commercially impractical.
For the present, auto OEMs are focusing on compressed hydrogen gas, which currently offer the best cost vs. benefit ratio and the fewest practical barriers