Liquid battery

08-26-2010 • Technology Review

In the fall of 2007, David Bradwell, an MIT grad student, created a new kind of battery--one that might eventually be used to store massive amounts of solar and wind energy for use at night or when the wind isn't blowing. Unlike existing batteries, it has active components that are liquid, which enables it to handle high currents without fracturing (the battery is kept at 700 degrees Celcius with the help of insulation). Last year Bradwell's research attracted a total of about $11 million from the U.S. Department of Energy's new Advanced Research Projects Agency-Energy (ARPA-E) and the French oil company Total.

Bradwell's battery is based on an electrolyte that can dissolve a compound consisting of two metals, such as magnesium and antimony. Applying a current in one direction splits the compound, and the two metals are deposited onto opposite electrodes. When no electricity is delivered, a voltage difference between the electrodes drives a current in the other direction. That generates electricity and causes the metals to recombine in the electrolyte.

The system could eventually cost less than $100 per kilowatt-hour for a new installation--about the same as pumping water up a hill to be released later to spin a turbine (the cheapest conventional approach for large-scale energy storage), says Arun Majumdar, the director of ARPA-E. The battery, however, would have the advantage of working in places without hills or large amounts of water, where many renewable power resources are located.