Energy cannot be created or destroyed, so producing and storing electricity is all about clever transformations. Some seem more out there than others – like the idea to give new life to abandoned mine pits and turn them into giant batteries. The only thing they need is sand (or an equivalent heavy enough material).
The approach is wonderfully simple and uses already-established technology. Things that are high up have potential energy. By bringing them down to a lower level, you can transform the potential energy into kinetic energy. That energy is usually what’s extracted. In the case of a gravity battery, sand would be placed in a lift that will go down a shaft, and energy extracted using regenerative braking.
Regenerative braking is used in many cars to charge batteries, with electric and hybrid vehicles even using the approach to charge the batteries that power their engine. They don’t completely emulate friction breaking, but they are effective at slowing down the car over a longer distance and getting energy out. It is also used in public transport, for example, the trains in the London Underground system. The sand will be deposited at the bottom and the lift is sent back up empty, costing a much smaller fraction of the electricity generated.
“To decarbonize the economy, we need to rethink the energy system based on innovative solutions using existing resources. Turning abandoned mines into energy storage is one example of many solutions that exist around us, and we only need to change the way we deploy them,” co-author Behnam Zakeri, a researcher at the International Instituto of Applied Systems Analysis, co-author in a statement
Many renewable power plants do not supply a continuous amount of electricity as they depend on factors like the weather. Batteries are needed to store that energy. When the electricity is abundant and cheap, sand can be brought up from the storage deep in the mine to storage on the surface (or near enough). When extra energy is needed, the sand is sent back down.
There are likely millions of mine pits in the world, and not all of them can be turned into Dark Matter detection facilities. Finding approaches to reuse in a sustainable way can be good for the environment and the local communities.
“When a mine closes, it lays off thousands of workers. This devastates communities that rely only on the mine for their economic output. UGES would create a few vacancies as the mine would provide energy storage services after it stops operations,” says Julian Hunt, a researcher in the IIASA Energy, Climate, and Environment Program and the lead author of the study. “Mines already have the basic infrastructure and are connected to the power grid, which significantly reduces the cost and facilitates the implementation of UGES plants.”
A paper describing this approach was published in the journal Energies.