Alternative way to store energy
The yield from natural energy sources such as wind and sunshine is fundamentally difficult to plan. In view of the ever-more necessary energy transition, alternative options for efficient energy storage are increasingly coming into focus. This is an alternative because, although batteries are a good storage solution, cheaper options have been lacking in a long-term cost-benefit comparison.
This now seems to be changing with the so-called Underground Gravity Energy Storage (-UGES) method. This novel method, developed by the International Institute for Applied Systems Analysis (IIASA), makes use of mine decommissioning to store energy. It involves lowering sand into an underground mine and later returning it to an above-ground reservoir. The trick is that the sinking of the sand takes place at peak times, i.e. when the price of energy is high, while the raising takes place at times when prices are low. When the sand is lowered, electricity is generated from regenerative braking energy, while the sand is raised by an electric motor.
The UGES is not only an effective solution for long-term energy storage; at the same time, it also offers an opportunity for communities that once flourished and whose main source of income has disappeared with the closure of the mine. For there are probably several million of them worldwide (estimated potential: 7-70 TWh, mainly in China, India, Russia and the USA). The infrastructure of the former mine is already in place and the connection to an electricity grid is as well, which means considerable cost savings. And even a few jobs are created by the new solution.
Durability as an advantage
While other energy storage methods - above all batteries - lose energy over time through self-discharge, the UGES is based on an extremely durable storage medium: sand. This means that energy can be stored for months or even years. The energy yield depends on the depth and width of the shaft, and the capacity of the energy storage in turn depends on the size of the mine.
Role model for the energy transition
Behnam Zakeri, a researcher in the IIASA programme and co-author, sees the new method as just one of many examples of how we will have to rethink in the future in order to make the necessary decarbonisation of the economy a reality. Many more innovative solutions are needed for the global energy transition.
Source: chemie.de, International Institute for Applied Systems Analysis (IIASA), 16.01.2023
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