Romania is developing a compressed-air energy storage project using underground salt caverns, with the aim of providing long-duration flexibility as renewable generation expands. The initiative is described as a Long Duration Energy Storage (LDES) technology.
How the compressed-air facility would operate
The project would use Romania’s natural underground salt caverns as reservoirs for compressed air. When electricity generation exceeds demand, air would be compressed and injected into the caverns. When demand rises, the stored air would be released to drive turbines via a hydraulic system to generate electricity for the grid.
Storage capacity and investment phases
Total project costs are estimated at approximately €55 million. A first phase is expected to deliver around 200 MWh of storage capacity with an investment of roughly €4.5 million. Operations are expected to start within 12 to 18 months after construction begins.
A second phase would expand discharge capability and total storage volume. It targets approximately 25 MW of discharge capacity and around 5 GWh (5,000 MWh) of total storage capacity. The additional investment for the expansion is estimated at about €50 million.
Partnership structure for cavern access and plant delivery
The partnership involves Hagag Europe and Airengy, with roles split between resource access and facility operations. Hagag Europe would provide access rights to the underground salt caverns. Airengy would be responsible for designing, constructing and operating the storage facility.
The model separates ownership of the geological resource from technology deployment and operational management. It is described as a framework that could be replicated in other countries with suitable underground storage formations.
Role in Romania’s evolving power system
Romania’s interest in long-duration storage is linked to changes in its power sector, including growth in photovoltaic capacity and renewable energy investment. Storage infrastructure has not expanded at the same pace as generation additions. Conventional lithium-ion battery systems are described as effective for short-term balancing and frequency support but less suited to multi-day fluctuations in renewable output.
Compressed-air storage is positioned as an alternative that can store energy over extended periods while relying on large underground volumes. The project also highlights reduced dependence on critical minerals compared with battery-based systems, according to the description of the technology category.
Market and delivery risks cited for financing
The project is described as carrying technology, regulatory and execution risks from an investment perspective. Commercial viability would depend on electricity market spreads and balancing market opportunities. It would also depend on potential capacity remuneration mechanisms and financing conditions.
The development of alternative storage technologies is presented as part of Romania’s strategic objective for flexibility layers in a system that includes solar, wind, natural gas and cross-border interconnections. Batteries are described as providing speed, pumped hydro as delivering scale, and compressed-air storage as supplying long-duration capability to bridge extended periods of renewable variability.
