Design and Optimization\nof Large-Scale Green Liquid\nHydrogen Production Integrated with Heat Recovery and Absorption Precooling

Liquid hydrogen (LH<sub>2</sub>) presents a viable solution\nfor\nenergy storage and transportation, particularly when produced by using\nrenewable electricity. In this study, the energy efficiency of large-scale\nPEM water electrolysis for hydrogen production was investigated to\nbe 59.74%, with the levelized electricity cost of hydrogen of 57.48\nkWh/kg. To recover the waste heat from the PEM electrolyzer, two heat\nintegration approaches have been proposed: the organic Rankine cycle\n(ORC) and the absorption refrigeration cycle (ARC). The ORC converted\nwaste heat into electricity, while the ARC generated cold energy to\nprecool the refrigerant, alongside electricity generation, both of\nwhich reduced energy consumption in the hydrogen liquefaction process.\nSubsequently, the process parameters were optimized through Matlab\nwith the Mesh Adaptive Direct Search algorithm aimed at minimizing\nthe specific energy consumption (SEC) of hydrogen liquefaction integrated\nwith ORC or ARC, resulting in SECs of 6.76 and 6.61 kWh/kg LH<sub>2</sub>, with 21.33% and 22.87% reductions compared with the liquefaction\nprocess without heat recovery, respectively. The corresponding exergy\nefficiencies were 56.96% and 57.16% for the liquid hydrogen production\nprocess, with 86.69% and 87.73% for the hydrogen liquefaction process,\nrespectively.