TVA energy storage project decision expected in 'weeks'

The Tennessee Valley Authority and the UK's Innogy Holdings PLC expect to announce within 'weeks' whether modules for a novel new electricity storage system will be fabricated in the UK or in the US, Barry Davidson, development manager of subsidiary Innogy Technology Ventures, said at Power-Gen International.

br>Kate Thomas
OGJ Online

ORLANDO-The Tennessee Valley Authority and the UK's Innogy Holdings PLC expect to announce within "weeks" whether modules for a novel new electricity storage system will be fabricated in the UK or in the US, said Barry Davidson, development manager of subsidiary Innogy Technology Ventures.

That decision will be the next step in the agreement between the two companies reported in August, Davidson said in an interview Wednesday at Power-Gen International. Under the initial agreement, TVA would serve as the US demonstration site for the technology.

Innogy's Regenesys energy storage technology is based on regenerative fuel cell technology, Davidson explained during a panel on energy storage technology. Construction is already underway on a 15 Mw, 120 Mw-hr, and 40 Mw storage system at National Grid Co.'s 680 Mw Little Barford power station in the UK. The plant is being built for a total installed cost of $1,500/kw, Davidson said, and is expected to be completed in 2002. Capital costs are expected to be cut in half during the "medium term," he said.

The Little Barford energy storage system will feature a black start capability, supplying the station's auxiliary load to restart the station in the event of a network interruption. The plant will also be used for electricity arbitrage.

Davidson said the system offers utilities features, including:

� An alternative to power stations to ensure security of supply during peak demand.

� Better use of the cleanest generating plant by reducing the need for less efficient peaking plant.

� The ability to enhance the flexibility and reliability of renewable energy.

� The potential to provide balancing services to the grid system, including frequency response, reserve, and voltage support.

� High ramp rates to meet changing loads on a power system.

� Fast response time of a fraction of a cycle required for ancillary service applications.

� Ability to supply real and reactive power.

� Low or no self-discharge to avoid energy losses.

� Environmentally benign and no adverse siting requirements.

Davidson noted Regenesys has been tested at Innogy's Aberthaw power station in South Wales since 1996. He said the electrochemical process operates like a giant rechargeable battery in that it can store electricity when demand and costs are low, and can release energy quickly when it is needed to meet demand. It uses electrolytes solutions of sodium bromide and sodium polysulphide. The electrolytes are pumped through the fuel cells in individual circuits separated by an ion exchange membrane.

When storing energy, the electrolytes convert to a charged state and can be discharged to release energy. Davidson said the conversion of electrical to stored chemical energy can be repeated indefinitely. In response to a question, Davidson said the projected life of the plant is about 15 years, cycling once every 24 hr.

"We believe electricity can now be treated like another commodity," Davidson. "It can be stored."

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