Nachhaltigkeit - Storing Liquid Hydrogen

20 October 2026, Peter S. Friese

Why hydrogen?

• zero emission: no direct co2 emissions and has the potential to reduce nox and water vapor emissions
• versatility
• declining costs

combination of hydeogn and oxygen reacts in the fuel cell to produce electricity - needs to be cooled
large portion of engine is taken up by cooling system\

technical challenges of storage

• hydrogen molecule is very small (80pm in largest direction)
• material compatibility
  • permeation
  • hydrogen embrittlement
• temperature compatibility
  • thermal expansion
  • thermal protection
• low density
  • hydrogen three times lighter per unit energy
• Hydrogen tank does not save H2 at state that is needed by engine - conditioning needed
  • to transfer fuel from tank state to engine state, 90kW of thermal energy are needed - heat loss of fuel cell can be used for this
  • per 1MW of themal energy: 20 g/s of H2 mass flow possible
• Tank pressure has to be kept constant with boiler
• In case of direct combustion: very high pressure is needed - can be achieved with pump
  • pumps require a certain level of net positive suction pressure (NPSP) at the inlet to avoid cavitation
  • NPSP drops to zero when tank is mixed (e.g. sloshing during a maneuver)

Good slide comparing pressure feed tank systems and pump feed tank systems

solid / liquid matter may show non expected behaviour e.g.

• thermal conductivity of copper (goes way up at 25K)
• ortho-para-transition of H2 (quantum effect)
• ductile-brittle fracture mechanics of austenitic steel at specific temperatures
• cryo-pumping
• change of emissivity
• change of thermophysical material properties

don't assume everything stays the same at different (especially lower) temperatures!