From ocean motion to green fuel: Integration of hybrid wave-tidal energy and offshore hydrogen production

Wave and tidal energy are promising renewable resources for offshore electricity generation, with hydrogen serving as a storable and transportable energy carrier. This study presents an integrated offshore hydrogen production system combining full-scale hybrid wave-tidal energy converters (HWTEC), hybrid supercapacitor-battery energy storage system, proton exchange membrane (PEM) electrolyzers, and subsea underground hydrogen storage (UHS). A system-level co-simulation framework is developed to capture the coupled dynamics of energy conversion, storage, and hydrogen production under stochastic marine conditions. UHS significantly reduces platform space requirements for hydrogen storage, enabling higher on-platform hydrogen capacity. A case study using 2024 UK wave and tidal data evaluates a conceptual platform with six HWTECs and PEM electrolyzers with combined average output of 64.8 kW. Results indicate a representative hydrogen production rate of 1.4 kg/h and an estimated annual yield of 12.4 t, with specific energy consumption of 46.8∼55.7 kWh/kgH 2 and exergy efficiency of 21.4∼25.3%. The system demonstrates enhanced power continuity, efficient conversion of intermittent offshore energy, and feasibility for grid-independent operation. The proposed framework advances beyond previous device-level studies by integrating multiple subsystems with real marine inputs, providing a scalable and practical tool for design, optimization, and performance assessment of offshore hybrid renewable hydrogen platforms. • Full-scale hybrid wave-tidal energy converter (HWTEC) developed for real deployment. • System-level co-simulation framework integrating HWTEC, battery and PEM electrolyzer. • Real UK wave and tidal data are embedded into system-level simulations. • Case study yields 12.4 t/yr hydrogen production and 21.4%∼25.3% exergy efficiency. • Underground hydrogen storage cuts deck space demand by 18.4× versus pressure vessels.