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Here comes the flow battery

Electrolyte flows in and out. It's a handy concept.

DAVIS, Calif.--What is a flow battery? It's a battery with tanks of electrolytes that effectively lets the battery store more energy than normal batteries. The electrolyte flows or circulates through the system. The larger the tanks, the more electricity it can store.

"They are cheaply made out of plastic. They are low maintenance," said Rick Winter, an executive at Deeya Energy, which makes flow batteries. The company has been busy this summer setting up manufacturing facilities in India, CEO Saroj Sahu told a few weeks ago.

Flow batteries won't appear in watches or MP3 players any day soon. They are too big, Winter explained.The batteries are for bulk energy storage and will serve as backup or emergency power sources. Nonetheless, it's a somewhat large market. Flow batteries will compete against things like industrial fuel cells. In Silicon Valley, there's been a lot of whispering about the concept in the past year. Until recently, Deeya's Web site was rather cryptic.

"A flow battery starts with a few kilowatts and goes up from there," he said. "There is no way you could use a flow battery for a phone."

Winter said that there are about five or six companies out there. Each one has a different twist on the chemistry; some are using vanadium, some are using zinc.

Investors include Draper Fisher Jurvetson and Nokia's venture arm.