United Kingdom

United Kingdom

Storage options

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Of the various storage technologies, pumped storage is the most firmly established, with around 22,000 MW installed in the United States and over 2000 MW in the UK. It is proven technology. The turbines used are similar to those found in hydro electric plant, but they are reversible and pump the water uphill when water is not flowing through them to make electricity. The other advantage is that they can deliver power for minutes or even hours at a time; most other technologies struggle to deliver (or absorb) power for long periods.

In terms of installed capacity, compressed air energy storage (CAES) follows next, but some way behind pumped storage. In the, US CAES capacity is around 100 MW, but more is being planned. As the title implies, compressed air is pumped into caverns and then released, usually into gas turbines. Research into improving CAES technology is also in progress in Germany, where a facility has been operating for some time, and elsewhere.

Other storage technologies include batteries, flywheels and superconducting magnets. The latter have relatively low energy storage capabilities and high costs but "flow batteries" -- where chemical reactions in electrolytes take the place of the water in a pumped storage system -- show some promise. The Regenesys technology based on this technique, developed by the UK's National Power (Windpower Monthly, October 2000) fell into this category. Although its new owner, German utility RWE, discontinued the work -- apparently confirming the poor options for making money on storage -- other, similar, systems are being developed in Canada, Japan and elsewhere.

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