Modelling, thermodynamic optimization and exergoeconomic analysis of an ORC aided multifunctional system utilizing geothermal energy for the production of liquid hydrogen

In this study, a comprehensive, multifunctional system consisting of ORC system, high temperature electrolysis system, absorption refrigeration system and hydrogen liquefaction system, developed for liquid hydrogen production, aided from geothermal energy, was modeled and thermodynamic optimization and exergoeconomic analyzes of the modeled system were performed. The thermodynamic performance of the system modeled for liquid hydrogen production was investigated at different evaporator temperatures (100⁰C-150⁰C) for different refrigerants (R123, R245fa, R601, n-Hexane) used in ORC systems. In addition, within the scope of the study, six different models were created for the hydrogen production system by considering the different liquefaction cycles and the solution pairs used in the absorption refrigeration system. Energy and exergy analyze of the models were performed, liquid hydrogen production performances were compared, and optimum operating parameters were determined for the system. Exergoeconomic analysis were performed for optimum operating conditions, and the exergoeconomic performances of the components that made up the system were evaluated. Considering all created models, it was determined that the thermodynamic performance of Model 2, in which the precooled Claude liquefaction system is used and the NH3-H2O solution pair is preferred in the absorption refrigeration cycle, was higher than the other models and more usable in terms of the amount of hydrogen production. Under constant operating conditions, the amount of hydrogen produced in Model 2 depending on the refrigerant and evaporator temperature was calculated as maximum 0,18049 kg/h, the energy and exergy efficiency was determined as 11,56% and 35,09% respectively. Exergoeconomic analysis of Model 2 for 150⁰C evaporator temperature and n-Hexane was performed and the electrolysis unit became the component with the highest investment cost with 441,206 USD/h. Furthermore, it was determined that the component with the highest exergy destruction cost in the system was the heat exchanger (2) in the Claude liquefaction system with a cost of 61,206 USD/h. The unit exergetic cost of liquefied hydrogen was calculated as 11,277 USD/GJ.