Achieving optimal energy efficiency, enhanced exergy performance, and comprehensive economic analysis in hydrogen refrigeration systems

This study introduces an optimized hydrogen liquefaction process using an enhanced precooling Joule-Brayton cycle. The hydrogen liquefaction process is highly energy-intensive due to its cryogenic temperature, with efficiency improvements constrained by process complexity, capital costs, and technical risks. To address these challenges and leverage the environmental benignity of hydrogen as the future energy source, we analyze the sensitivity of objective functions to key operating variables and propose a novel optimization approach. This method balances equipment costs and energy consumption, ultimately reducing total expenses. An integrated MATLAB-Aspen HYSYS framework, using a genetic algorithm (GA), is employed for the optimization. Thermodynamic analysis is conducted based on the heat exchangers' composite curve and the cycle’s entropy, accounting for non-ideal operation. The process liquefies 5 TPD of hydrogen, achieving an SEC of 5.941 kWh/kg, a coefficient of performance (COP) of 0.2065, and a figure of merit (FOM) of 0.5125, outperforming recent studies that employed the MR cascaded liquefaction process. Exergy analysis yielded an efficiency of 51 %, considerably higher than other similar processes. Economic analysis was conducted with a levelized cost of hydrogen at $3.42/kg. Additionally, the liquified hydrogen attained a much lower temperature −252.9 °C compared to the Claude cycle −252.7 °C, increasing the storage efficiency. These findings provide a practical basis for the optimization and financial feasibility analysis of hydrogen liquefaction processes.