Energy storage in salt caverns under investigation by RWE


Salt caverns currently used for gas storage are under investigation as large-scale, organic flow batteries.

The project by RWE Gas Storage West GmbH and CMBlu Energy AG is investigating organic flow technology as a means of harnessing the massive storage potential of huge underground caverns.

The challenge for energy storage is to scale the capacity on different timescales to make the most of the growing renewable generation capacity. Currently Europe’s largest battery located in Jardelund, Schleswig-Holstein, which is based on lithium-ion technology, has a storage capacity of about 50MWh. In comparison, the potential capacity of the caverns is estimated up to several gigawatt hours.

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The concept is to use an organic electrolyte solution filling the salt caverns as the primary energy source. As a first step, potentially suitable electrolytes have been identified. In the next stage running up to the beginning of 2021, their suitability for use in salt caverns will be investigated in the lab.

Once a suitable electrolyte has been identified, work will start on constructing and operating a test system. The planned capacity of the system is 100kW/1,000kWh and is expected to be in place by the spring of 2024.

“The future belongs to renewables. In order to make optimal use of green electricity, we need large stationary electricity storage systems,” says Andreas Frohwein, technical managing director of RWE Gas Storage West. “In the future, we may be able to use our salt caverns as batteries for storing enormous quantities of electricity. Using existing technical infrastructure, they could also be connected to the electricity grid quickly.”

Such storage systems also offer other benefits, notes Peter Geigle, CEO of CMBlu Energy AG. “Organic flow batteries are based on carbon, which is available globally in almost unlimited volumes. The components are easy to recycle, and water is the largest component by volume. That means the battery isn’t flammable, so it’s safe to use. In addition, organic storage systems use no metal, unlike most other batteries.”