From Yahoo Tech
This magic box is called a vanadium redox flow battery. The heart of a flow battery are two electrolyte solutions — one positive, one negative — contained in separate tanks. When the solutions are pumped through a power cell containing a membrane, a chemical reaction takes place that generates electricity. When the process is reversed, the electrolyte stores energy.
The key component is vanadium, a naturally occurring element that can exist in positive and negative states, eliminating the contamination and degradation that occurs when two different elements are used to create a chemical reaction. Flow batteries are not as efficient as solid-state lithium-ion batteries. But unlike lithium-ion batteries that lose their capacity over time as they charge and discharge, the nontoxic electrolyte in a vanadium flow battery is endlessly reusable and never loses its efficiency.
Vanadium flow batteries are not new — an Australian scientist named Maria Skyllas-Kazacos invented the technology in 1985. But there was a catch. Two, actually. The battery needed pure and pricey vanadium to work. And the fact that the electrolyte became unstable at 35 degrees Celsius (95 degrees Fahrenheit) limited the usefulness of the batteries.
“The electrolyte was always the one cost you couldn’t squeeze because you needed pure vanadium,” says Tim Hennessy, Imergy’s president, who previously ran a Vanadium battery company in China. “So the batteries ended up being about 50 percent more expensive.”
But Imergy claims it has made a big breakthrough. First, chief technology officer Majid Keshavarz developed a novel electrolyte chemistry that allows Imergy to use a lower grade of vanadium that can be extracted from iron ore waste, oil sludge, or fly ash generated by coal-powered power plants.
Their 30 KW battery will be housed in a 40' shipping container and cost >$15,000, should be in production by 2017.