Sustainable liquid hydrogen production: Comprehensive modeling and thermodynamic analysis of a geothermal-powered multifunctional system

Abstract

In this study, a comprehensive, multifunctional system developed for the production of liquid hydrogen, utilizing geothermal energy, and consisting of an organic Rankine cycle (ORC), high-temperature electrolysis system, absorption refrigeration cycle, and precooled Linde-Hampson liquefaction system as subsystems, was modeled. The thermodynamic performance of the liquid hydrogen production system was investigated using alternative refrigerants (n-Hexane, R123, R245fa, R601) in the ORC at evaporator temperatures ranging from 100 °C to 150 °C. Energy and exergy analyses of the liquid hydrogen production system were performed, and the specific energy consumption (SEC) of the system was evaluated for different working parameters. The best operating conditions of the system were determined by comparing the amount of liquid hydrogen produced. Based on the evaporator temperature and refrigerant used in the ORC, the energy efficiency of the liquid hydrogen production system varied between 7.93 % and 10.53 %, while the exergy efficiency ranged from 24.07 % to 31.94 %. Additionally, it was found that the amount of liquid hydrogen obtained from the modeled system varied between 0.124 kg/s and 0.164 kg/s depending on the operating parameters. The decrease in SEC with increasing evaporator temperature suggested a potential improvement in system performance at higher temperatures. Specifically, as the evaporator temperature increased, the SEC of the system decreased by 22 % for n-Hexane and by 18 % for R245fa. This indicated that n-Hexane might offer greater energy efficiency at elevated temperatures.