March 9, 2026 - As many as half a million abandoned coal mines dot the United States. These mines pose a major threat to public health and safety, in addition to environmental well-being. While many of these sites have been abandoned since the 1970s, before federal regulations for their reclamation were established, they may finally be getting cleaned up, and even converted into a power bank for the renewable revolution.

Scientists at the Oak Ridge National Laboratory (ORNL) recently announced a breakthrough in the development of a methodology to turn the nation’s 500,000 abandoned coal mines into energy storage to help support the power grid. Using high-fidelity hydrodynamic and chemical models, the team has demonstrated how these sites could feasibly be converted into pumped hydro facilities, capable of long-term energy storage. 

Such a breakthrough would offer multiple benefits. First, it would help to clean up and repurpose defunct coal mines which are rife with “hazards such as open mine shafts, unstable highwalls, subsidence and polluted water that can threaten homes, roads and public infrastructure” according to a recent report from Mining.com. The Trump administration has recently recognized the urgency of this threat, and earmarked $725 million in 2025 to “clean up abandoned coal mines and restore opportunity in America’s historic coal communities.” But actually turning these mines from a liability into an asset could yield reverberating benefits for energy security, the environment, and the economy. 

Second, it would bring much-needed jobs and economic growth to former mining communities. This may offer a lifeline in many parts of the country that are facing near-total collapse of local economies as coal mining continues its terminal decline. Despite the Trump administration’s efforts to revitalize the dirtiest fossil fuel, experts say that we can still expect coal’s share of the national energy mix to drop to less than 1% in 2035, as compared to 45% in 2010. With this loss, coal communities face “a steep fall in economic activity, shrinking revenue, falling property values, and a dislocated workforce” according to the National Bureau of Economic Research. 

Finally, converting abandoned coal mines into “water batteries” would offer much-needed stability to the nation’s stressed power grids while helping to uphold decarbonization goals. As data centers pop up around the United States to support the AI boom, energy demand is soaring and the nation’s aging grids are being pushed to the brink. Meeting that demand without abandoning clean energy goals or energy security will require a massive and unprecedented buildout of long-term energy storage. Wind and solar power, while great options for cheap and clean energy, are variable – meaning that their production waxes and wanes according to the weather and the season, and often in opposition to energy demand patterns.

Long-term energy storage will be absolutely essential to managing these various needs and priorities. Currently, global energy storage systems are dominated by lithium-ion batteries, but these can only hold onto energy for a maximum of four hours, when stabilizing inflows and outflows of energy to the grid will require storing energy for much longer periods of time. Pumped hydro is one of the leading technologies in what is currently a fierce global race to find a high-efficiency, affordable, and long-term storage solution in a rapidly changing energy environment. 

Using an old coal mine to suit these purposes is not without its challenges, however. “The environment inside a mine is chemically active and structurally intricate,” reports Interesting Engineering. But this is where ORNL’s advanced modeling could be pivotal, as it accounts for how water moves through different spaces and interacts with various chemicals. “Our modeling tools will help industry partners evaluate these risks and make informed decisions about facility design, construction and operations at specific locations of interest,” says Galen Fader, Science Writer at ORNL.