America's Abandoned Coal Mines Could Become Giant Underground Batteries

Reimagining Abandoned Coal Mines

Across the United States, an estimated 500,000 abandoned coal mines present significant environmental and safety hazards. These sites, often neglected since the 1970s, pose risks to public health, infrastructure, and ecological balance. However, a novel approach is emerging to transform these liabilities into assets, potentially revolutionizing energy storage and revitalizing affected communities.

Scientists at the Oak Ridge National Laboratory (ORNL) have pioneered a method to repurpose these mines as energy storage facilities, specifically through pumped hydro technology. Their research demonstrates the feasibility of converting these sites into long-term energy storage solutions, leveraging sophisticated hydrodynamic and chemical models.

Economic and Environmental Benefits

The benefits of this approach are multifaceted. Firstly, it addresses the pressing need for remediation of hazardous mine sites. According to Mining.com, these abandoned mines are plagued by dangers such as “hazards such as open mine shafts, unstable highwalls, subsidence and polluted water that can threaten homes, roads and public infrastructure.” Recent government initiatives, including a $725 million allocation in 2025, underscore the urgency of this issue. Transforming these sites into productive assets could generate substantial economic, environmental, and energy security advantages.

Secondly, this initiative promises to inject much-needed economic stimulus into former mining communities. As coal mining continues its decline, these regions face severe economic hardship. The National Bureau of Economic Research highlights the challenges of “a steep fall in economic activity, shrinking revenue, falling property values, and a dislocated workforce.” Repurposing mines can create new jobs and foster sustainable economic growth.

Power Grid Stability and the Future of Energy Storage

The conversion of abandoned coal mines into pumped hydro storage facilities offers critical stability to the nation’s power grids while supporting decarbonization efforts. The increasing demand for energy, driven by factors such as the growth of data centers, is straining existing infrastructure. Renewable energy sources like wind and solar are essential but intermittent, necessitating robust long-term energy storage solutions.

While lithium-ion batteries dominate current energy storage systems, their limited storage duration poses a challenge. Pumped hydro offers a viable alternative for long-term storage, positioning it as a key technology in the global race for efficient, affordable, and sustainable energy solutions. Pumped hydro can store energy for much longer durations than 4 hours which is the limit for lithium-ion batteries.

Galen Fader, Science Writer at ORNL, notes that the ORNL modeling tools can “help industry partners evaluate these risks and make informed decisions about facility design, construction and operations at specific locations of interest,” which will be necessary because “the environment inside a mine is chemically active and structurally intricate,” according to Interesting Engineering.