Converting coal mines into gravity-based renewable energy storage facilities

Scottish start-up Gravitricity is considering the deployment of its gravity energy storage system at the decommissioned Staříč coal mine, in the Moravian Silesian region of Czechia.

The mine consists of six deep sites that could potentially host the storage solution developed by Gravitricity, which uses clean power to raise a mass in a 150-1,500m shaft and discharges the electricity thus ‘stored’ by releasing the mass to rotate an electric generator.

Specialists from the U.K. company and Diamo, which is a state-owned entity that manages decommissioned mining sites across Czechia, investigated the location features down to a depth of over 1km.

An investment decision is expected to be made early next year and more mining sites in the country may be considered for further plans, Gravitricity said in a statement. “We are ready to cooperate in [the] preparation of this project and have provided Gravitricity with all the information to allow them to make a fully qualified decision on the Staříč mine,” stated Diamo CEO Ludvík Kašpar. “We are convinced that closed mines have the potential for further use and an energy storage project could be attractive and useful for the region.”

Experts from the VSB Technical University of Ostrava were also active in the project assessment. The project is part of a plan to commence a full-scale, 4-8 MW prototype scheme in a disused mine next year.

The storage system developed by Gravitricity has so far been built as a 250 kW demonstrator project on an industrial site at Port of Leith, Scotland’s largest enclosed deepwater port. That facility was built with a 15m high lattice tower, two 25-ton weights suspended by steel cables and two grid-connected generator units. The technology is claimed to have a faster response time than lithium-ion storage technology and to be able to help stabilize electricity networks at 50Hz by responding to full power demand in less than a second.

Gravity storage has begun to raise interest in the renewable energy industry in recent years. U.S. company Energy Vault unveiled, in 2019, gravity-based storage technology relying on a crane and 35-ton concrete blocks. Austrian research organization the International Institute for Applied Systems Analysis (IIASA) recently suggested gravitational energy storage for low-energy-demand locations.