Flow battery maker gets $15 million

Deeya Energy, which makes large flow batteries to provide backup power to industrial plants, raised $15 million in a second round of financing, according to Venture Wire.

The company earlier raised $7.5 million and is building manufacturing facilities in India.

What is a flow battery? It's a battery with tanks of electrolytes that effectively let the battery store more energy than normal batteries. The electrolytes flow or circulate through the system. The larger the tanks, the more electricity it can store.

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. An individual flow battery can provide backup power for 8 to 16 hours and store several kilowatts of power. The electricity is discharged during peak demand periods.

Deeya claims its batteries are 3 times less expensive than lead acid batteries, which were around when Calvin Coolidge still strode the earth, and 10 to 20 times cheaper than lithium ion batteries. "They are cheaply made out of plastic. They are low maintenance," said Rick Winter, an executive at Deeya last fall.

Energy storage is the big kahuna in the green tech market (along with clean coal.) Demand for both these technologies is huge. Car makers, utilities, industrial sites, solar homes, and wind power companies all want better batteries and other devices for storing energy. Unfortunately, it's also a difficult problem.

Hence, a lot of money is flowing into companies like Deeya, Boston-Power (notebook and later plug-in hybrid batteries), and General Compression (compresses air for later use).