IN Brief:
- Net Zero Energy is developing a proposed 600MW long-duration storage project in County Carlow.
- The Rathrush scheme would use surplus renewable power to produce green hydrogen.
- The project is being developed around grid security, renewable balancing, and long-duration flexibility.
Net Zero Energy has selected County Carlow for a proposed 600MW long-duration energy storage project that would use surplus renewable electricity to produce green hydrogen and return power to the grid when required.
The Rathrush Green Energy Park is planned near Rathoe, southeast of Carlow town, and has been presented as a first-of-a-kind development for Ireland. The scheme would produce green hydrogen using renewable electricity, store it in underground lined rock caverns, and convert it back into electricity during periods of system demand.
With an estimated development cost of around €2bn, the project is positioned as long-duration infrastructure rather than a short-duration battery asset. The development is at planning and pre-application consultation stage, with delivery dependent on consenting, grid connection, finance, engineering design, environmental assessment, and commercial support for long-duration storage.
Ireland’s electricity system already relies heavily on wind generation, and higher renewable penetration brings more periods where output exceeds immediate system demand or network capability. Storage that can absorb surplus renewable electricity and deliver power later could reduce dispatch-down, strengthen security of supply, and provide flexibility across longer periods than lithium-ion batteries usually target.
Hydrogen-linked storage carries a different engineering profile from conventional battery storage. Electrolysers, compression systems, cavern storage, conversion equipment, grid interface systems, safety infrastructure, and water management all add technical complexity. The value of the approach lies in duration and scale, particularly where stored energy may be needed beyond the intraday windows served by most battery assets.
The wider balancing challenge is already visible across the UK and Irish energy systems. National Gas’s summer outlook raised questions around system flexibility and demand patterns, with balancing pressure becoming more prominent as renewable output and electrified demand change operating conditions.
Long-duration storage is now being discussed as a necessary counterpart to short-duration flexibility. Batteries can deliver frequency response, reserve, intraday arbitrage, and rapid system support. Hydrogen-linked assets, pumped hydro, compressed-air storage, and other long-duration technologies are aimed at deeper system gaps, including low-renewable periods and multi-day security-of-supply requirements.
Rathrush also illustrates the scale of infrastructure needed to turn surplus renewable electricity into dependable stored power. The project would need electrical, civil, mechanical, chemical, and subsurface engineering disciplines to work together, with grid connection and safety approval processes running alongside hydrogen production and storage design.
The commercial framework remains one of the hardest parts of the model. Long-duration storage can provide system value that is not always captured cleanly by existing wholesale, capacity, or balancing markets. Without a revenue structure that reflects duration, availability, and security-of-supply value, large projects can struggle to move from development to investment.
Ireland’s power system will need more storage, more flexible generation, and more active demand management as renewable output increases. Rathrush is one of the clearest signs that long-duration storage is moving from national energy planning into site-specific engineering development.
