Large-scale liquid hydrogen production methods and approaches: A review

Large-scale hydrogen liquefaction (LHL) methods and different approaches of the configuration of hydrogen liquefaction cycles are chronicled. History landmarks of permanent gases liquefaction are quick reviewed and the basic hydrogen liquefaction cycles, the existing in-service LHL plants around the world, and LHL conceptual proposed plants, including the state of the art plants, are recorded and categorized based on the systems’ main parameters. In addition, a novel classification of hydrogen liquefaction systems in terms of heat exchange and expansion process method is introduced. As well as, the authors infer that renewable energy technologies section should be added to the old sectioning of the hydrogen liquefaction plants. In addition, hybrid conceptual hydrogen liquefaction plants, combining with renewable power cycles are reviewed and the increasing contribution of this new approach is demonstrated. Finally, the operational costs of the plants considering the systems’ efficiency are examined, and a trend in specific energy consumption (SEC) and exergy efficiency of hydrogen liquefiers is discussed. Accordingly, considering the existing technologies, SEC reduction of hydrogen liquefaction will not be abrupt in near future and it will remain within the range of 5–8 kWh/kgLH2. Moreover, exploiting of isentropic expansion processes instead of isenthalpic one, cascading of refrigerating cycles, using of new mixed refrigerants as working fluid of refrigeration cycles, and hybridization of renewable energy power cycles to refrigeration cycles are the main four growing approaches in the hydrogen liquefaction context.