Dynamic simulation of offshore wind-to-green hydrogen power with thermochemical hydrogen co-production and underground storage in Ireland

Ireland’s National Hydrogen Strategy targets 2 GW of offshore wind capacity dedicated to hydrogen production by 2030. This study presents a dynamic 20-year simulation of an integrated wind-to-hydrogen-to-power system in which green hydrogen produced via proton exchange membrane electrolysis is stored in the depleted Southwest Kinsale gas reservoir and reconverted through a hydrogen-fuelled gas turbine to meet peak electricity demand. Four scenarios representing 10–25% of the planned offshore wind capacity are evaluated. A novel feature of the system is the integration of a vanadium–chlorine thermochemical cycle using gas turbine exhaust heat to co-produce additional hydrogen. The base-case system achieves an overall efficiency of 31.67%, increasing to 61.13% under advanced material assumptions. Net present values (NPV) remain negative under current assumptions (–€0.295 bn to –€1.051 bn), while levelised costs of energy (LCoE) range from €495 to €528 MWh⁻ 1 , indicating that the system is not economically viable as a private investment under current assumptions, primarily due to high capital costs and limited gas turbine utilisation. However, under improved material performance, the system achieves a positive NPV of €407 million and an LCoE of €259 MWh⁻ 1 . The results demonstrate that large-scale geological hydrogen storage combined with thermochemical hydrogen recovery is technically feasible for balancing offshore wind and enhancing energy security. While private-sector viability remains challenging under present conditions, future technology improvements could enable commercially viable large-scale renewable hydrogen power systems.