Once a mine has been exhausted of its ore, there’s really no use for it anymore – it just becomes an abandoned hole in the ground. According to a new study, the shafts of mines that do not have more ores could be used in energy-storing gravity batteries.
It is a system in which electricity is generated by releasing a heavy load, allowing it to drop. That electricity can then be used at times when demands on the municipal grid are high.
In a pumped-storage hydroelectric system, water is released from a high elevation, generating electricity by spinning up turbines as it flows downhill. When excess energy is available, that water is pumped back up to the starting point.
Last year, scientists from Austria’s International Institute of Applied Systems Analysis (IIASA) proposed a different type of gravity battery. The basic idea was that the elevators in high-rise buildings would use regenerative braking systems to generate electricity while lowering weighted payloads from higher to lower floors.
The mine-based Underground Gravity Energy Storage (UGES) system, recently proposed by the same researchers, will utilize elevators, but these ones would be in existing disused mine shafts, and they’d be raising and lowering containers full of sand.
For maximum efficiency, the elevators could take on a sand load at the surface, have that load removed at the bottom of the shaft, then return to the surface empty. A combination of electric conveyor belts and dump trucks would be used for the on- and offloading.
“When a mine closes, it lays off thousands of workers […] UGES would create a few vacancies as the mine would provide energy storage services after it stops operations,” said IIASA’s Julian Hunt, lead author of a paper on 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.”
The paper was recently published in the journal Energies.