Tim Radford September 30, 2015

The dream of a home battery—cheap, durable, safe and as big as you like—that could store solar or wind power is a step nearer reality

Researchers from Harvard University in the U.S. report that they have tested a “flow battery” that uses cheap and abundant chemical elements, can be operated with plastic components, will not catch fire and can operate at 99 percent efficiency.

Such batteries could be used to save and store surplus wind and solar power, which could then be used at times when neither form of renewable energy can deliver.

The latest advances are based on technology already tested by the same engineers, but made more attractive with a switch to chemical components that are non-toxic, non-flammable and safe for use in homes and offices.

The combination of a common organic dye and a cheap food additive in alkaline, rather than acidic solutions, meant that the researchers could increase their battery voltage by 50 percent.

It also means—at least in principle—that a domestic residence could store its own surplus solar or wind power and keep the refrigerator or the central heating running after sunset or on windless days. How much a house could store would depend only on the size of the tanks that held the two electrolytes.

“This is chemistry I’d be happy to put in my basement,” says Michael Aziz, a professor of materials and energy technologies at Harvard, who has led the research. “The non-toxicity and the cheap, abundant materials placed in water solution mean that it’s safe. It can’t catch fire—and that’s huge when you are storing large amounts of electrical energy anywhere near people.”

The researchers do not argue that better batteries would be of no advantage. Their case is that the absence of better batteries need not and should not, stop investment in renewables.