Andreas Augustin, Thomas Wintgens
• Indirect seawater splitting is the preferred option for large-scale H 2 production. • RO outperforms thermal desalination due to system integration constraints. • The Balance of Plant for AWE and PEM systems is analyzed in detail. • Feed water quality requirements and impact of impurities are discussed. • Water treatment concepts are proposed for AWE and PEM. This study examines the technical feasibility of using seawater as a feedstock for green hydrogen production, with a focus on system design and water treatment aspects. Both direct and indirect seawater splitting approaches are considered. Direct seawater electrolysis is excluded from further consideration due to unresolved challenges such as parasitic side reactions and electrode degradation. For make-up water generation, thermal desalination and seawater reverse osmosis (SWRO) were evaluated. Thermal desalination, though potentially powered by waste heat from electrolysis, was deemed impractical due to its dependence on the electrolyzer plant’s heat management system, which complicates overall plant control. In contrast, SWRO operates as a standalone system and imposes minimal impact on hydrogen production costs through competing power consumption, making it the preferred option for large-scale applications. Alkaline Water Electrolysis (AWE) and Proton Exchange Membrane (PEM) electrolysis are identified as the only currently available industrial-scale electrolyzer technologies. A Balance of Plant analysis revealed key water treatment interfaces, including make-up water systems required for both technologies, and a loop purification system specific to PEM systems. A design study translated the identified requirements into practical plant configurations, providing a detailed evaluation of treatment options and implementation strategies. The study concluded with an outlook on future water-focused research, laying the groundwork for continued advancements in support of large-scale green hydrogen production.