Oak Ridge National Laboratory has developed advanced modeling tools that could transform thousands of abandoned coal mines across the United States into giant underground energy storage systems, potentially solving one of the biggest challenges facing renewable power adoption.
Researchers created high-precision hydrodynamic and chemical simulations that help determine whether defunct mine networks can be safely repurposed for pumped storage hydropower, a technology often described as a “water battery” because it stores energy by moving water between reservoirs at different heights, according to Oak Ridge National Laboratory.
Pumped storage hydropower already accounts for more than 90% of large-scale energy storage in the US, but expansion has been limited by geography. Conventional systems require mountains or large elevation differences to function effectively, restricting projects to specific regions. The new approach bypasses this barrier by moving operations underground, using deep mine shafts as the lower reservoir instead of relying on natural terrain.
This method reuses existing mining infrastructure, allowing energy storage facilities to be built in flatter regions that previously could not support hydropower projects. By avoiding the need for large surface construction, the approach could reduce project costs and significantly shorten development timelines. It also provides economic opportunities for former mining communities by turning long-abandoned industrial sites into modern energy assets.
However, converting coal mines into storage facilities is not straightforward. Underground environments are chemically reactive and structurally complex, raising concerns about equipment damage and long-term safety. Scientists must ensure that high-pressure water movement does not destabilize tunnels or cause collapses.
The newly developed models simulate how water would flow through mine networks and how it would interact with residual minerals. This allows engineers to predict corrosion risks that could damage turbines and to evaluate the structural integrity of mine walls under operational stress.
With the technical groundwork in place, researchers are now moving toward full techno-economic assessments to determine feasibility at specific sites. Future studies will analyze system efficiency, construction requirements, and operational best practices to guide potential commercial deployment.
If successful, the technology could convert environmental liabilities into critical infrastructure, enabling long-duration energy storage needed for a carbon-neutral grid while breathing new life into regions shaped by America’s coal mining past.
