The future of energy is right around the corner; abandoned mines with batteries harnessing the power of gravity have the potential to help the globe run sustainably.

One of the major problems with many sources of renewable energy, especially wind and solar, is managing the excess power they generate. As they only generate electricity during certain conditions (when the wind is strong and when the sun is out, respectively) more energy is created than the grid can use during those periods.

This excess energy is then stored in batteries, typically made from lithium or other similar minerals that can be harmful to the environment when mined – soil degradation, loss of biodiversity, and immense water usage being some examples. This can somewhat cancel out the environmental benefits of sustainable energy.

Gravity batteries pose a possible solution to this issue, storing excess energy by using it to lift heavy objects from deep in the ground. To access this energy, the objects are dropped, spinning a turbine to convert the kinetic energy to electricity.

Digging out many large holes could still have a negative effect on the environment though, with similar impacts to mining battery materials. This is where abandoned mines come in handy, according to a study from the International Institute for Applied Systems Analysis (IIASA). As millions of abandoned mines across the globe are already there and not in use, no extra mining, environmental damage, or land usage is needed.

The gravity battery method has many other advantages too, such as not losing charge over time. Standard batteries gradually lose their stored energy through self-discharge.

“A minuscule amount of the chemical substances inside the batteries reacts even without any connections between the electrodes. Those internal reactions reduce the stored charge of the battery and thus decrease the capacity of the battery little by little,” battery manufacturer Panasonic claims.

Another benefit of the batteries is how their operation would open up new jobs, restoring those lost from mines closing.