The Energy Cost of Storing Hydrogen: Thermodynamic Minima versus Practice, Recounted

Reversible minima for hydrogen storage computed from stated thermodynamic inputs with an archived script: real-gas-corrected isothermal compression requires 2.08 kWh/kg to 350 bar and 2.40 kWh/kg to 700 bar (6.24% and 7.19% of LHV); liquefaction of a normal feed requires at minimum 3.59 kWh/kg (10.8% of LHV), with the ortho-para conversion releasing 540 kJ/kg, 1.21 times the latent heat. Operating stations and liquefiers operate at second-law efficiencies of about 46% and 31% respectively. For ammonia, pressurised liquefaction costs 0.53 kWh per kg of hydrogen carried but cracking requires at minimum 4.24 kWh of thermal energy per kg of hydrogen (12.7% of LHV).