During the 2023 United Nations Climate Change Conference (COP28 ), the world is coming together for crucial global transformative action on climate change. Amid the imperative to find efficient and accessible storage for renewable energy, repurposing decommissioned mines as long-term energy storage systems emerges as a promising solution. This innovative approach addresses the need for reliable energy storage across various time scales, providing potential storage solutions for weekly, monthly, or seasonal periods.
Published in the open access journal Energies, a team of multi-institutional researchers introduce a unique Underground Gravity Energy Storage (UGES) design. This novel technique aims to repurpose underground mines for storing vast amounts of energy. The innovative process involves transporting sand into these mines to store energy and subsequently converting the sand's potential energy into electricity through regenerative braking.
The researchers estimate that by employing UGES into abandoned mines, this can provide a global energy storage potential ranging from 7 to 70 TWh. The majority of this potential is concentrated in China, India, the United States, and Russia.
This cost-effective and efficient long-term energy storage solution, not only could revitalise millions of defunct mining sites globally but also would bring economic benefits to local communities, offering a multitude of advantages for sustainable development.
“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, author on the paper.
In the study, the researchers explain how existing energy storage methods, like batteries, are prone to lose energy via self-discharge over time. In contrast, UGES, utilising sand as the storage medium, eliminates self-discharge, allowing for ultra-long energy storage time spanning weeks to several years. This component is vital for achieving efficient and sustained energy storage.
“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,” explains Hunt.
The study details the functioning of UGES, which harnesses excess energy produced by renewable sources to lift a substantial weight. During periods of excess electrical energy in the grid, UGES transports sand from the mine to an upper reservoir, storing potential energy. In times of low production, the released weight powers a turbine as it descends. The process uses regenerative braking to convert the sand's potential energy into electricity, providing an efficient means of storing and retrieving energy, ensuring grid stability and meeting demand fluctuations.
Using sand as an energy storage medium ensures a zero self-discharge rate, allowing for prolonged storage times, in contrast to battery energy storage. The system's key advantage lies in its low energy storage costs (MWh), encompassing the cost of sand and the land needed for the upper storage site.
“To decarbonise 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,” says Behnam Zakeri, author on the paper.
Underground Gravity Energy Storage is a promising avenue for generating and storing stable amounts of energy, particularly for long-term energy storage solutions to mitigate seasonal fluctuations in electricity demand and renewable generation from wind and solar sources.
If you're interested in learning more about this research, you can access the paper published Energies here: shorturl.at/kpuwC
MDPI