Recent advances in hydrogen liquefaction and storage
Several review articles present a comprehensive overview of the liquid hydrogen supply chain. IIR members Linde and Air Liquide are contributing to address the global demand for hydrogen.
According to the IEA, hydrogen and hydrogen‐based fuels are important on the roadmap to decarbonising the global energy system. Admittedly, hydrogen applications provide small total emission reductions by 2030 in the IEA Net Zero Scenario, compared with deployment of renewables or direct electrification. Nevertheless, they play a fundamental role in sectors where emissions are hard to abate, such as heavy industry, shipping, aviation and heavy-duty transport.
Hydrogen can be stored in various forms, including its gaseous, liquid, and solid states, as well as derived chemical molecules. Liquid hydrogen has gained increased attention as the most suitable for the transport of large volumes of hydrogen over long distances. However, hurdles to the development of liquid hydrogen systems include an energy intensive liquefaction process (∼13.8 kWh/kgLH2) and high hydrogen boil-off losses (liquid hydrogen evaporation during storage, 1–5% per day).
Furthermore, the environmental impact of depends on how it is produced:
- Grey hydrogen relies on coal gasification and steam reforming of natural gas, It is massively used in industry nowadays because the costs of steam reforming are relatively low. It emits at least 10 kg CO2 per kilo hydrogen production. 
- Blue hydrogen has the same production process as grey hydrogen, but is complemented by carbon capture and storage to reduce greenhouse gas emissions.
- Green hydrogen is produced from renewable energy and is the most appropriate hydrogen for a fully sustainable energy transition. The most established technological option for producing green hydrogen is water electrolysis fuelled by renewable electricity.
Hydrogen liquefaction processes
Although hydrogen liquefaction is considered a proven technology, improvements are still being made to further reduce energy consumption and enhance efficiency, which is critical for reducing the cost of the liquid hydrogen supply chain.
Hydrogen liquefaction methods can be broadly divided into two categories in terms of thermodynamic cycles: common liquefaction cycles (including Linde-Hampson cycles, refrigerant liquefaction cycles, Claude cycles, and expander liquefaction cycles), and magnetic refrigeration cycles.
Please read the following review articles for more information on hydrogen liquefaction, cryogenic storage technologies, liquid hydrogen regasification processes as well as current industrial applications and the drivers and barriers that are making liquid hydrogen a commercially viable part of the emerging global hydrogen economy:
- Zhang T et al. 2023 Hydrogen liquefaction and storage: Recent progress and perspectives.
Commercial hydrogen liquefaction plants
Over the last 20 years, commercial hydrogen liquefaction plants have been constructed in the USA, Japan, Germany, Australia and Korea. Recently constructed plants are based on modified Claude cycles. The simple Claude cycle for liquid hydrogen production has been reported to give a liquefaction yield of 8%, a specific energy consumption of 22.1 kWh/kgH2 and an exergy efficiency of 18.1%.
In 2021, IIR member Linde doubled its hydrogen liquefaction capacity at its Leuna site in Germany (built in 2008) by commissioning a second plant.[3, 4] Because natural gas is a fossil resource, the hydrogen produced is referred to as “grey hydrogen”. At present, grey hydrogen still accounts for more than 90 percent of the hydrogen mix at Leuna. Although the same plant can be used to produce gray and green hydrogen, the biomethane used to produce green hydrogen is a more limited resource than natural gas. According to Linde, green hydrogen currently represents five percent of the output at Leuna.
In 2022, IIR member Air Liquide inaugurated its largest liquid hydrogen production and logistics infrastructure facility in North Las Vegas, USA. The facility will produce 30 tonnes of liquid hydrogen per day, namely to serve the growing clean mobility market on the West Coast of USA. Fully powered by renewable electricity, the facility can also use renewable natural gas to meet the California Low Carbon Fuel Standard (LCFS) when supplying the California mobility market.
Hydrogen re-liquefaction process for boil-off gas handling on a large-scale liquid hydrogen carrier.
 IEA (2022), Hydrogen, IEA, Paris https://www.iea.org/reports/hydrogen , License: CC BY 4.0
 Zhang, T., Uratani, J., Huang, Y., Xu, L., Griffiths, S., & Ding, Y. (2023). Hydrogen liquefaction and storage: Recent progress and perspectives. Renewable and Sustainable Energy Reviews, 176, 113204. https://doi.org/10.1016/j.rser.2023.113204
 Yue, M., Lambert, H., Pahon, E., Roche, R., Jemei, S., & Hissel, D. (2021). Hydrogen energy systems: A critical review of technologies, applications, trends and challenges. Renewable and Sustainable Energy Reviews, 146, 111180. https://iifiir.org/en/fridoc/hydrogen-energy-systems-a-critical-review-of-technologies-144416
 Al Ghafri, S. Z., Munro, S., Cardella, U., Funke, T., Notardonato, W., Trusler, J. M., ... & May, E. F. (2022). Hydrogen liquefaction: a review of the fundamental physics, engineering practice and future opportunities. Energy & environmental science, 15(7), 2690-2731. https://doi.org/10.1039/D2EE00099G
Credits image: Air Liquide Las Vegas H2 plant