DCU Researchers Show Hydrogen Storage in Salt Caverns Could Transform Ireland's Renewable Energy Future

The researchers have published an extensive techno-economic analysis examining how Ireland's surplus wind energy could be captured, converted into green hydrogen, and stored underground in salt caverns for later use across electricity, transport, and heating markets.

The study as Ireland has recorded one of the highest rates of wind energy curtailment in Europe in 2024, with 14% of available wind energy going unused across the island — rising to 30% in Northern Ireland alone. Rather than allowing that energy to go to waste, the team modelled a system in which the surplus is used to produce hydrogen gas via electrolysis, which is then stored in underground salt formations until needed.

Salt Caverns provide a solution

The team have identified salt formations in Islandmagee and Larne in County Antrim as geologically well-suited to large-scale hydrogen storage. A candidate site near Belfast demonstrated excellent structural integrity, with a projected annual leakage rate of just 0.03% and a volume loss rate low enough to support storage over a 30-year horizon with a capacity of 400,000 cubic metres.

Salt caverns were favoured over alternatives such as aquifers or depleted gas reservoirs because they are chemically inert with respect to hydrogen, require less cushion gas, and can support the frequent charging and discharging cycles needed for dynamic energy markets.

Multi-Sector Approach key to affordability

When modelled purely as a seasonal electricity storage system charging the cavern during Ireland's windier spring and summer months, then selling electricity back to the Day-Ahead Market in winter, the costs proved prohibitive, reaching approximately €37.60 per kilogram of hydrogen. The fundamental problem is idle time: under a purely seasonal model, the system is actively operating for only around three weeks of the year.

However, the picture changes dramatically when hydrogen is also supplied to the transport and heating sectors. By increasing the number of annual charging and discharging cycles to between 20 and 30, the levelised cost of storage falls to just €2–3 per kilogram — a range competitive with emerging hydrogen market prices. The team found that the electricity business case alone was actually cash-positive, with the seasonal model generating over €55,000 in annual profit from electricity trading. The high overall storage cost is therefore driven not by energy prices but by the large capital investment being spread across too few operational cycles.

Sensitivity and Scalability

The study also found that electrolyser costs are among the most significant variables in the system's economics. Reducing electrolyser capital expenditure from €1,500 per kilowatt to €700 per kilowatt — a reduction considered plausible as next-generation Anion Exchange Membrane technology matures — cuts overall costs by around 30%. Careful management of operational and maintenance expenditure was likewise shown to have a material effect on viability.

Scaling the system across multiple adjacent cavern wells at the same site would allow shared use of compression infrastructure, further reducing per-unit costs and enabling a much larger share of Ireland's curtailed wind energy to be captured.