A new long duration energy storage project is taking shape more than 2,000 feet below the surface, using advanced compressed air technology to store energy for when the grid needs it most. The approach marks a significant shift in how utilities can firm up intermittent renewable resources without relying on lithium-ion batteries.
At that depth, natural geological formations serve as pressure vessels, allowing compressed air to be stored in salt caverns or other stable rock structures. The system can discharge power for 8 to 12 hours or longer, far outstripping the typical 4-hour duration of most battery storage installations. This extended capacity helps grid operators manage multi-day weather events or sudden drops in renewable generation.
The project is being constructed with a focus on scalability and cost-effectiveness. Developers are leveraging existing natural gas plant infrastructure, including turbines and grid interconnections, to reduce capital expenditures. While specific investment figures were not disclosed, industry estimates suggest such projects can achieve levelized costs competitive with combined-cycle gas plants when deployed at scale.
From a regulatory standpoint, the technology is gaining traction as states push for carbon-free electricity by mid-century. It offers a solution to the intermittency problem without requiring new transmission lines or controversial mining for battery materials. However, the technology remains nascent, with only a handful of commercial-scale projects operating globally.
A key caveat: compressed air energy storage requires specific underground geology, limiting its geographic applicability. Critics also argue that round-trip efficiency—typically around 60% to 70%—lags behind lithium-ion batteries, which exceed 90%. This efficiency gap means developers must carefully match the technology to use cases where long duration outweighs energy losses.