Cogeneration system utilizing geothermal energy: Energy, exergy, economic and environmental analyses and multi-objective optimization

Abstract

A comprehensive energy, exergy, economic, and exergoeconomic analyses was performed on a geothermal-based cogeneration system designed for the simultaneous production of hydrogen, oxygen, and freshwater. The system comprises three principal subsystems: a dual-pressure organic Rankine cycle for power generation, a reverse osmosis desalination unit for freshwater production, and a proton exchange membrane electrolyzer for hydrogen and oxygen generation. The system optimization was carried out using a non-dominated sorting genetic algorithm with the objective of minimizing the total exergy destruction cost rate while maximizing freshwater output. The results indicate that the organic Rankine cycle is responsible for the largest share of exergy destruction, accounting for approximately 61 % of the total, whereas the proton exchange membrane electrolyzer contributes about 65 % of the total exergy destruction cost rate. From an exergoeconomic perspective, the high-pressure turbine demonstrated the highest exergoeconomic factor, implying that its exergy destruction is relatively low compared to its associated investment cost. The overall exergy efficiency of the system and the corresponding payback period were estimated to be 23.81 % and 7.04 years, respectively, confirming the technical feasibility and economic viability of the proposed configuration.