Off-Grid System for Production of Green Hydrogen via Electrolysis of Industrial Effluents: A Technical Analysis

This study evaluates, through simulation, the technical feasibility and highlights the environmental benefits of a proposed off-grid system for electrolytic green hydrogen production using industrial effluents and solar photovoltaic and wind energy (Off-Grid GH₂PS). The simulations compare the operational dynamics of the current scenario (grid electricity and natural gas) of an industry located in northeastern Brazil with those of the proposed system (renewable electricity, PEM electrolyzer, effluent conditioning system, battery storage, and hydrogen-natural gas blending). The results show strong solar-wind complementarity, with irradiance ranging from 4.77-6.92 kWh/m²/day and wind speeds from 5.04-8.49 m/s, resulting in a total generation of 1.91 GWh/year, of which 62% came from solar energy. Of this amount, the electrolyzer consumed 1.36 GWh/year (84% of the demand). Hydrogen production reached 17,976 kg/year, and annual consumption totaled 17,262 kg. The 10% hydrogen blending into natural gas reduced natural gas use by 3%, but it required a 6.5% increase in volumetric flow. Effluent conditioning showed low seasonal variability and delivered 486.8 m³/year, although only 27% reached the electrolyzer due to purification losses. It was observed that 27.54 kgH₂O/kgH₂ and an energy consumption of 75.90 kWh/kgH₂ were required. Environmental performance showed an emission reduction of 10.99% (465.5 tCO₂eq/year). Overall, the Off-Grid GH₂PS demonstrates a strong potential for industrial decarbonization in regions with high availability of renewable resources and effluents. Finally, future studies should incorporate high-resolution temporal data sets, integrate degradation models for system components, and enable dynamic coupling between water treatment and the energy-hydrogen subsystems. A detailed life-cycle assessment is also recommended to strengthen the overall sustainability analysis, as well as an economic feasibility evaluation of the proposed system.