A Comprehensive Thermodynamics Investigation of a Solar-Powered Hydrogen Production Plant

Green hydrogen production utilizing a solar-powered proton exchange membrane (PEM) electrolyzer is a promising technology for generating clean energy and reducing greenhouse gas emissions. This work presents a comprehensive thermodynamics study to investigate producing hydrogen gas through PEM electrolysers driven by solar-powered Rankine cycles. Parabolic trough solar collectors supply thermal energy to a single-stage Rankine cycle (SRC) and a binary steam-organic Rankine cycle (SRC-ORC) using different refrigerants to generate electricity that powers the electrolysers. First and second law analysis on solar collectors, power cycles, and PEM electrolysers are presented. Over the solar irradiation range (G_b = 600–1000 W/m²), results show that (SRC-ORC) configuration produced the highest hydrogen rate when using the R134a and R744 as working refrigerants in the ORC. Moreover, at a G_b = 800 W/m², the model shows that (SRC-ORC) yields higher energetic and exergetic efficiencies compared to the corresponding (SRC) by about 12% and 14%, respectively. The analytical model reveals that more than half of the exergy input to the system was destroyed in the electrolysers followed by solar collectors and then power cycles. This highlights the necessity to optimize the design of PEM electrolysers to enhance the hydrogen production rate.