Multi-objective particle swarm optimization applied to a solar-geothermal system for electricity and hydrogen production; Utilization of zeotropic mixtures for performance improvement

Abstract

Renewable energy sources such as solar, wind, and geothermal energy have become increasingly popular due to their environmental benefits and long-term sustainability. This study proposes an innovative integration of a solar system and a geothermal system to optimize the performance of a geothermal power plant. The geothermal system is coupled with a solar system, which utilizes a direct and storage system to increase the efficiency of solar energy utilization and minimize energy loss. To recover waste heat, an electrolyzer is used in a triple-flash geothermal system that operates at high feed geofluid temperatures, producing hydrogen as a byproduct. The organic Rankine cycle with a zeotropic mixture working fluid is employed to generate additional power. After considering eight candidate working fluids, Butene/R123 is selected. The designed system exhibits an impressive 10.83 MW net power, 9.87 kg/h hydrogen, 18.86% energetic efficiency, 29.45% exergetic efficiency, and 4.88 years payback period with a 29.72 M$ net present value. Additionally, two energy-economic and exergy-economic scenarios are evaluated to determine the optimum state. The energy-economic scenario has a lower payback period, whereas the exergy-economic scenario offers greater profitability over the system's lifetime.