Thermally coupled solid hydrogen storage and carbon capture for balancing intermittent renewable energy

Wind turbines provide renewable power with near-zero CO₂ emissions, but struggle to achieve steady electricity supply, owing to inherent wind speed variability. Hence, clean energy carriers, such as 'green' hydrogen from electrolysis, are required to balance daily power output, and minimise reliance on dispatchable fossil fuels during periods of insufficient wind. Here, we present a system for integrating solid-state hydrogen storage with carbon capture via magnesium looping, using waste heat from the hydrogen storage reaction to drive the process. Incorporating magnesium looping as thermo-chemical energy storage overcomes a major limitation of solid-state hydrogen storage (poor thermal efficiency), and offsets CO₂ emissions from the use of back-up gas turbine capacity. Thermal integration of the MgH₂ storage improved round-trip efficiency (conversion from electricity to stored H₂, and back to electricity) to  ~ 19%, comparable to liquid or gas storage, whereas MgH₂ alone without heat recovery is limited to  ~ 4%. We model power supply and energy storage over five years for onshore and offshore windfarms using real-world data, finding combined hydrogen storage with magnesium looping is the only system able to meet daily electricity demand and compensate for seasonal wind capacity factor variation, while offsetting CO₂ operating emissions from flexible gas deployment.