Photovoltaic-powered saline electrolyzers for sustainable crop irrigation and integrated CO2 mitigation: A case study

This study presents a bench-scale demonstration of a sustainable irrigation system powered by solar energy and integrated with chlor-alkali electrolysis for hydrogen production and CO2 capture. A 100 Wp photovoltaic panel directly powered a saline electrolyzer, generating hydrogen and sodium hydroxide. The hydrogen was compressed and used in a fuel cell to drive a 7 W peristaltic pump simulating agricultural irrigation. Once hydrogen was depleted, a thermal engine was activated, and its CO2 emissions were partially captured using the hydroxide-rich catholyte. A long-duration field test confirmed the system's viability. Solar energy input (213.7 Wh) was sufficient to fill five hydrogen cylinders. Electrochemical performance showed high Faradaic efficiencies (>95% for hydrogen), with chlorine yields up to 185 mg Wh−1. Hydroxide production peaked at ∼200 mmol but was limited by membrane degradation and chlorine crossover, especially at low current densities. Comparative tests using constant current densities (50–150 mA cm−2) validated the scalability of hydrogen production. Fuel cell operation recovered ∼6% of the input energy, sustaining irrigation for up to 2.5 h. Hydrogen feed rates (∼130 mL min−1) remained within optimal specifications. CO2 capture tests showed near-stoichiometric carbonate formation under controlled dosing. In real exhaust conditions, capture efficiency dropped to ∼2% due to short gas residence time, though total carbonate retention increased. These results demonstrate the dual utility of the system: clean hydrogen generation and effective CO2 capture. The approach offers a promising, low-emission solution for off-grid agricultural energy and carbon management.