Depleted and abandoned underground mines not only being considered for geologycal CO2 storage purposes - Carbon Capture and Storage (CCS) technologies - but also for Underground Gravity Energy Storage, UGES.
Yes. You read correctly and we find the potential of this concept to be great. From both environmental and social perspectives.
The UGES model proposed by the International Institute for Applied Systems Analysis (IIASA) group of researchers is a gravitational energy storage technology that consists of filling an underground mine with sand to generate electricity when the cost is high and then removing the sand from the mine to "store energy", when electricity is either cheap or renewable. Unlike battery energy storage, the energy storage medium of UGES is sand (its weight), which means the self-discharge rate of the system is zero, enabling ultra-long energy storage times.
Undeground mines are well-suited to such "batteries" because they already have:
elevators to raise and lower the containers
deep shafts that could be used to drop a weight
basic infrastructure and are connected to the power grid
Gravity batteries, require at least 300 metres of fall space to work properly. "The number of closed or abandoned mines is challenging to estimate, but it is likely to be in the range of millions of sites globally. Over 550,000 have been found in the USA, 50,000 in Australia and over 10,000 in Canada.
From a social perspective, “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.
Click at the image below https://pure.iiasa.ac.at/id/eprint/18562/1/energies-16-00825.pdf to read the article "Underground Gravity Energy Storage: A Solution for Long-Term Energy Storage". It includes:
schemes that better explain the concept
formula to calculate how much power could be generated for each mine characteristic
UGES potential per country
advantages and disadvantages of UGES compared with other gravitational energy technologies: energy vault, gravitricity, Lift Energy Storage Technology (LEST), Mountain Gravity Energy Storage (MGES), Electric Truck Gravity Energy Storage (ETGES)
a suggested operation at the TauTona mine and solar power plant near Johannesburg, South Africa
cost estimates for the investment
75 interesting references
