Hydrogen liquefaction

Hydrogen liquefaction involves a multi-stage process of compression and cooling to -253 °C, so that it is liquefied and stored in cryogenic tanks, increasing its volumetric density. The process starts with hydrogen compression and an optional (liquid nitrogen) pre-cooling to -193 °C, followed by cryogenic cooling to -243 °C (including heat exchangers and ortho- to para- catalytic conversion) and a final isenthalpic expansion to bring hydrogen to liquid phase at -253 °C and 1 bar. Hydrogen liquefaction is an energy-intensive process, especially for compression. The most recent hydrogen liquefaction plants have an electricity consumption of approximately 10 kWh/kg, equivalent to around 30% of the energy content (LHV) of hydrogen, and while hydrogen liquefaction is considered an established technology, efficiency improvements to values around 6 kWh/kg are expected in larger plants. Electricity costs are only a fraction of the hydrogen liquefaction costs and the capital cost for liquefaction is also expected to decrease with further innovations.