Vanadium redox batteries could balance the electrical grid for solar and wind power

Vanadium “redox flow” batteries are very stable. They can be discharged and recharged 20,000 times without much loss of performance, and are thought to last decades (they have not been around long enough for this to have been demonstrated in practice).

They can also be enormous, and – in large part thanks to their vanadium content – expensive. The smallest of the “Cellcube” batteries that American Vanadium is producing in partnership with German engineering firm Gildemeister has a footprint the size of a parking bay and costs $100,000.

How does a Vanadium Redox Flow Battery work?

They consist of two giant tanks of different solutions of vanadium dissolved in sulphuric acid, separated by a membrane

The battery produces an electrical current as the fluids are pumped past electrodes on either side of the battery
In one tank, the vanadium releases electrons, turning from yellow to blue
In the other tank, the vanadium receives electrons, turning from green to violet
The electrons pass around a circuit, generating a current, while at the same time a matching number of protons (hydrogen ions) pass across the membrane between the two solutions

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