Abandoned Mines Hold the Key to Cheap Energy Storage

Gravity batteries are not new, but when placed into abandoned mines, they are cheap, plentiful and easy to deploy.

Renewable energy from wind and solar is intermittent; winds are not constant or even predictable with 100% certainty, and while predictable, the sun only shines during the day. The key to making these abundant renewables work for society is energy storage; how do you store energy to make it useful later? Experts have been researching and developing methods of storing renewable energy which can be used when needed. Reservoirs could supplement lithium-ion batteries, and existing coal plants can be converted into wind or sun energy distribution points.

An additional appealing technique is known as gravity batteries. This technology can store energy and put it back onto the grid through regenerative braking and gravity. Recently, scientists revealed a gravity battery that uses abandoned mines to store energy based on vestiges of dirty energy’s past.

The International Institute for Applied Systems Analysis (IIASA) researched these new batteries, examining Underground Gravity Energy Storage (UGES) technology. When generated energy is expensive (aka peak hours), this battery lowers large containers of sand or concrete into a mine. Regenerative braking converts the potential energy of the sand into actual energy, and the larger the mine, the larger the battery.

The mine battery later recharges using electric motors to bring the weights back to the surface – in off-peak hours when electrical energy is cheap. Unlike lithium-ion batteries, gravity batteries don’t experience any self-discharge, allowing them to remain ready with energy for long periods. Moreover, this strategy offers plenty of additional advantages; it maintains jobs, keeps unsightly infrastructure out of sight and takes advantage of existing connections to the grid. Most mines already have the basic infrastructure in place and are usually connected to the power grid, reducing costs and facilitating implementation. 

In England, companies are looking into ways to turn abandoned coal mines into modern batteries. The greatest beneficiaries of this technology would mainly be countries with many existing mines, but to make it more widely available, Energy Vault – a company from Switzerland – is working to create gravity batteries which could be installed in urban and suburban areas. These gravity batteries are built on the sides of existing buildings or in new construction, allowing them to be incorporated into the architecture and making them more attractive visually.

The future will be green and full of new ideas to create energy using readily available renewable sources. All renewable sources are made more efficient using storage in some way. It is somehow satisfying to see the relics of our industrial past, like mines, being turned into valuable parts of our future.