Techno-economic assessment and optimization of integrating a geothermal-powered cascade setup with a steam electrolyzer to devise a high-performance poly-generation scheme

This study introduces a novel poly-generation system integrating a cascade Kalina cycle, organic Rankine cycle, and a liquefied natural gas regasification system with a solid oxide steam electrolyzer for simultaneous production of electricity, cooling, hydrogen, and potable water using geothermal energy. The system uses the heat from geothermal fluid to drive the Kalina cycle for power generation, which powers a reverse osmosis unit for desalination. Residual heat powers the bottoming organic Rankine cycle-liquefied natural gas system for additional electricity and cooling production, while steam feeds the solid oxide steam electrolyzer for hydrogen production. Unlike prior geothermal-based poly-generation systems employing proton exchange membrane or alkaline electrolyzers, this design utilizes a solid oxide steam electrolyzer for enhanced efficiency and lower costs. A multi-objective optimization yields a trade-off point with poly-generation exergy efficiency of 38.44%, total cost rate of 679.9 $h−1, and unit cost of 18.28 $GJ−1. Exergy analysis reveals 6409 kW of useful products from 16673 kW fuel exergy, with contributions of electricity (66%), cooling (23%), hydrogen (9.9%), and freshwater (1.1%) to the total exergy production. Comparative results show superior thermodynamic performance and reduced hydrogen production costs over existing systems, positioning this as a promising geothermal utilization strategy.