why does it matter: Gravity batteries are a potential candidate for storing excess renewable energy, but finding places to install them is a challenge. Researchers have suggested that abandoned mines around the world could be a cost-effective solution that may also provide employment.
Study from the International Institute for Applied Systems Analysis (IIASA) Suggest Decommissioned mines could be repurposed to power gravity batteries. Converting ancient mines could provide enough energy to match the planet’s current daily consumption of electricity.
Gravity batteries attempt to solve one of the central problems with renewables such as wind and solar power – excess energy storage. Wind and solar often generate more power than the grid can use right away, so power companies have to store what’s left, usually in batteries.
Methods like the IIASA experiment use that extra energy to lift heavy objects. When the energy is needed again, the weight is dropped which spins the turbine and converts the kinetic energy from gravity.
In theory, gravity batteries could be anything with significant weight, such as water or solid objects. The IIASA study lowered and raised sand in abandoned mine shafts, moving it back and forth between upper and lower chambers based on energy needs.
Another advantage of this process is that while batteries tend to self-discharge over time, gradually losing their stored energy, the gravity method stores energy in sand (or whatever else is lifted to harness gravity) that does not self-discharge.
IIASA suggests using abandoned mines because there are likely already millions of them all over the planet that can be converted relatively cheaply for this purpose. Most have the basic infrastructure to function and are already connected to the power grid.
The researchers believe that after an investment cost of approximately $1-10 per kilowatt-hour and an energy capacity cost of $2,000 per kilowatt-hour, their method could have a global potential of 7-70 TWh. According to the International Energy Association, global energy consumption for 2020 – the latest year on record – sum 24,901.4 TWh, which breaks down to about 68 TWh per day.
Furthermore, operating gravity batteries in abandoned mines could restore or preserve some of the jobs lost when those mines closed.