California start-up Deeya Energy said on Tuesday it raised $30 million to build "redox flow batteries" which it says will be a competitively priced way to replace diesel generators and store wind and solar energy.
Deeya Energy is one of many start-ups targeting large-scale storage systems which can act as back-up power for commercial applications, such as telecommunications towers, or electricity.
The company's basic technology was first developed in the 1970s as part of a NASA research program. A flow battery uses electrolyte solutions of reactive chemicals that flow between two tanks to deliver an electrical current.
One advantage of flow batteries is that they can charge relatively quickly. Deeya Energy says its first product, called the Energy Storage Platform 24K, can store four hours worth of electricity to cell towers and takes only three hours to recharge.
Another advantage is that the material used in the flow battery is not toxic and can be recycled. Deeya Energy says its storage units will be far cleaner than diesel generators or lead-acid batteries.
Deeya Energy's series C round brought in new investor venture capital firm Technology Partners. The company has raised $53 million since it was founded in 2004. Initial investors BlueRun Ventures, Draper Fisher Jurvetson, Element Partners and New Enterprise Associates participated in the latest round.
The money will allow the company to build a few thousand of its 2-kilowatt cell phone tower back-up batteries it is marketing to the Indian telecommunications market, Deeya Energy CEO Isak Bencuya told Greentech Media.
The product is designed to last 20 years. The electrolytes need to be replaced every five years.
In the next year or two, the company intends to make 1-megawatt size flow batteries for power grid applications, such as storing energy from wind and solar farms.
Energy storage has become one of the hottest areas in clean-tech investing with entrepreneurs developing a wide range of different technologies.
One of the biggest challenges is finding ways to make storage cheaper than existing alternatives. In the large-scale energy storage business, the incumbent technology is often lead-acid batteries or, for grid storage applications, pumped hydro, where water is pumped uphill and released at off-peak times to generate electricity.