Liquid hydrogen cold energy recovery to enhance sustainability: Optimal design of dual-stage power generation cycles

Liquid hydrogen (LH2) is a promising hydrogen carrier because of its high density. However, liquefying hydrogen requires considerable energy and expenses. To enhance the sustainability, this study focuses on recovering cold energy from LH2 to mitigate costs and carbon emissions in LH2 supply chain. Three power generation configurations are proposed, combining the Brayton and Rankine cycles to efficiently recover cold energy across a wide temperature range of LH2. These configurations are the series Brayton and Rankine (SBR), the parallel Brayton and Rankine (PBR), and the integrated Brayton and Rankine (IBR) processes. In the SBR process, the Brayton cycle recovers cold energy from LH2 in the cryogenic temperature, followed by the Rankine cycle in the low temperature. The PBR process involves the Rankine cycle recovering LH2 cold energy indirectly from the Brayton cycle. In the IBR process, the Rankine cycle recovers cold energy not only from LH2 in the low temperature but also from the Brayton cycle. This results in the highest cold energy recovery performance and net power output, leading to a 6.19% reduction in carbon emissions within the LH2 supply chain. Furthermore, despite its high initial investment, the IBR process demonstrates economic feasibility due to its superior energy performance.