A Multi-carrier Energy System for Electricity, Desalinated Water, and Hydrogen Production: Conceptual Design and Techno-economic Optimisation

This study investigates the integration of multiple energy carriers within a unified, multi-carrier energy system using an energy cascade approach. The system harnesses geothermal energy to power interconnected subsystems, including an organic Rankine cycle (ORC), liquefied natural gas (LNG), and a solid oxide fuel cell (SOFC) stack. The dual ORC system and LNG stream are directly fed from the geothermal source, while the SOFC stack uses methane produced during LNG regasification. Besides electricity, the system generates hydrogen and desalinated water by incorporating a proton exchange membrane (PEM) electrolyzer and a reverse osmosis (RO) desalination plant. The electricity produced by the upper ORC powers the PEME for hydrogen production, while freshwater production is supported by the combined output from the lower ORC, LNG turbine, and SOFC. A detailed thermo-economic analysis assesses the system’s efficiency and economic feasibility. Optimization efforts focus on three areas: electrical efficiency, hydrogen, and freshwater production, using artificial neural networks (ANN) and genetic algorithms (GA). The optimization results reveal that Ammonia-propylene excels in electrical efficiency, R1234ze(Z)-ethylene in net power output, R1233zd(E)-propylene in cost-effectiveness, R1234ze(Z)-propylene in hydrogen production, and Ammonia-ethane in water production. The study offers valuable insights into enhancing the efficiency, cost-effectiveness, and sustainability of integrated energy systems.