Here's some good news for the energy storage market:

Deeya Energy, the flow battery company, has started to commercially ship its units, according to Izak Bencuya, CEO of Deeya, who spoke this morning at the Smart Grid Innovation Symposium sponsored by Innovation Center Denmark (otherwise known as the SGISICD taking place in Menlo Park.)

"We started selling in June," he said. The first permanent installations will take place this month, he added.

Deeya's units can hold about 2 kilowatts of energy. It is selling them first to cellular companies to provide power to cell towers. Its first market is India. Flow batteries, however, could help balance or store power at utilities. VCs have been clamoring for energy storage technologies and large conglomerates like General Electric have been to. So the fact that they have succeeded should give everyone a dose of optimism.

Right now, the technology costs are high because the company is not at scale, he said. "The customers who are paying for it right now are using diesel generators as distributed power generation, maybe 20 hours a day, for mission critical applications. The cost of running diesel generators is very very high."

Deeya saves these kind of customers 50 percent to 90 percent of the operating cost. To get to grid, Deeya will have to bring the cost down by four times. The units now sell for around $4,000 per kilowatt. In the next twelve to 18 months, Deeya would like to do a megawatt-scale demonstration.

Earlier in the month, Deeya announced it raised $30 million.

Founded in 2004, Deeya earlier raised $15 million in January 2008 and about $7.5 million in an earlier round of funding (see Funding Roundup: First Deals of the New Year).

Deeya's redox flow batteries are aimed at providing a low-cost alternative to lithium-ion and other advanced batteries – about 10 to 20 times less expensive, the company says. Redox flow batteries work by moving an electrolyte through a reactor that converts their chemical energy to electricity. Spent electrolyte is recovered for recharge while newly energized electrolyte is pumped back in.

That system combines a battery's efficiency with a fuel cell's bulk energy storage capacity, according to NASA, which first developed the technology behind Deeya's energy storage platform in the 1970s.