Researchers at Oak Ridge National Laboratory are Exploring Gravity, Underground Pumped Hydro, and Compressed Air Energy Storage at Appalachian Mines and Shafts

      Researchers at Oak Ridge National Laboratory have done advanced hydrodynamic modeling, including chemical modeling, to assess the feasibility of converting abandoned coal mines into underground pumped storage hydropower (PSH) facilities for energy storage. In September 2025, I wrote about a similar analysis done to evaluate using abandoned mines for PSH. in 2023 in China’s Henan Province. A study of abandoned Appalachian coal mines for use in pumped hydro, gravity, and compressed air energy storage is ongoing.

     PSH involves pumping water up, typically when energy demand and costs are low, and letting it fall back down while powering turbines, when demand and costs are high. Using mines and mine shafts for PSH has the advantage that deeper tunnels can function as the lower reservoir, while the surface or upper shafts serve as the upper reservoir. This creates a closed-loop system that avoids the need to dam rivers or flood natural valleys.

     Compressed air storage is being considered for horizontal mine works where the air is compressed when energy demand and costs are low and depressurized to power turbines when demand and costs are high.

     Gravity energy storage involves using excess grid electricity during low-cost/low-demand times to lift extremely heavy weights toward the top of a mine shaft. When electricity demand rises, the weights are slowly lowered back down the shaft. Their descent spins a generator, producing electricity that flows back into the grid, as depicted below. Company Green Gravity is working with this method. Many of the shafts are deep enough for such systems to work.

“The weights used in these systems are often constructed from recycled steel or dense concrete to maximize mass. Because the process depends on physical motion rather than chemical reactions, the equipment can operate for decades without the performance loss seen in many lithium-ion batteries.”    

     The researchers have developed a tool to rank and grade sites that offer the best circumstances, according to the Daily Galaxy:

“The tool analyzes factors such as shaft depth, geological stability, and proximity to existing transmission lines. Mines that meet these criteria are flagged as potential candidates for future energy storage facilities.”

“Many of these sites already sit near electrical infrastructure built during the mining era. Heavy-duty power lines once supplied electricity to ventilation systems, water pumps, and underground equipment. Reusing this infrastructure could reduce the cost and time needed to connect storage systems to the grid.”

“The research now underway at Oak Ridge National Laboratory focuses on identifying which abandoned coal mines meet the structural and geological requirements for underground storage systems. The laboratory maintains a national database listing mine sites that satisfy the depth, stability, and infrastructure conditions needed for gravity-based and underground energy storage.”

 

  

References:

 

500,000 abandoned US coal mines to become giant underground water batteries with a new storage method. Arezki Amiri. Daily Galaxy. March 12, 2026. 500,000 abandoned US coal mines to become giant underground water batteries with a new storage method

Transforming abandoned coal mines into energy storage solutions: Modeling capabilities evaluate sites for underground pumped storage hydropower. Thien D. Nguyen. Oak Ridge National Laboratory. March 3, 2026. Transforming abandoned coal mines into energy storage solutions