Comparative performance assessment of a solar thermal organic Rankine cycle-driven alkaline electrolyzer for green hydrogen production

Green hydrogen is recognized as a critical energy carrier for deep decarbonization, yet many production pathways remain reliant on fossil fuels or conventional photovoltaic electrolysis. This study presents a comparative performance assessment of a solar thermal-driven hydrogen production system integrating an organic Rankine cycle (ORC) with an alkaline electrolyzer. The proposed configuration comprises solar thermal collectors, a pressurized sensible heat storage tank, an ORC power unit, and an electrolyzer. A dynamic MATLAB-based simulation framework was developed to evaluate eight system configurations under identical meteorological conditions over a full year of hourly operation. The investigated scenarios examined the combined effects of collector technology (evacuated tube vs. parabolic trough), ORC working fluids (R245fa and n-pentane), and system sizing parameters. Performance was assessed based on annual hydrogen yield, overall solar-to-hydrogen efficiency, and productivity per unit collector area. The optimal configuration—employing parabolic trough collectors, an R245fa working fluid, a 180 m 2 collector field, and an 8 m 3 storage tank—achieved an annual hydrogen production of 752.8 kg·year − 1 (4.705 kg·m − 2 ·year − 1 ), corresponding to 25,094 kWh·year − 1 of hydrogen energy output. The overall solar-to-hydrogen efficiency reached 7.03%, with a solar-to-ORC efficiency of 10.2%. Results underscore the critical role of thermal availability and storage stability in enhancing ORC operating hours and hydrogen yield, demonstrating the viability of solar thermal ORC–electrolyzer systems for sustainable hydrogen production in high-insolation regions.