Wednesday, February 15, 2012

#ENERGY: "Grid-Scale Batteries Could Buffer Renewables"

Gigantic grid-scale batteries containing self-separating liquids, instead of metal electrodes, promise to buffer renewable energy sources by storing, for instance, wind energy at night for use during the day.

Professor Donald Sadoway and research affiliate David Bradwell at MIT's Materials Processing Center observe a test battery inside the heavily insulated metal cylinder heated to 700 degrees Celsius (1292 degrees Fahrenheit). (Source: MIT)

Novel grid-scale all-liquid batteries promise to enable electricity from renewable sources--such as solar, wind, and ocean--to be stored then released on-demand by virtue of chemical reactions that take place at over 1200 degrees Fahrenheit.

Researchers at the Massachusetts Institute of Technology (MIT) claim their all liquid battery technology can be inexpensively replicated on a gigantic scale, to help make renewable energy sources viable, since much of their production is wasted today due to a lack of grid-scale battery technologies. For instance, when the wind blows at night when electricity demands are low the all-liquid batteries could level-the-load by storing the energy produced until daylight, thus smoothing out erratic renewables.

The key to the inexpensive new battery technology is that it consists entirely of liquid components. Conventional liquid batteries--like the one it most cars--use two metal electrodes separated by a liquid electrolyte. However, the new MIT gird-scale battery is entirely liquid. Three different liquids of different densities--the top and bottom liquids acting as the electrodes and the middle one as the electrolyte--naturally stay separated in a manner similar to how some cocktails will separate into liquid levels in your glass.

The liquid materials are all inexpensive and yet work even better than liquid-core batteries with solid electrodes, according to their inventor, professor Donald Sadoway. (Sadoway has been working toward the all-liquid battery for three years with his team that includes MIT doctoral candidate David Bradwell.)

The only major downside to MIT's all-liquid battery is that it must be heated to 1292 degrees Fahrenheit in order to keep the three liquids separate. By keeping the all-liquid battery in a tightly sealed and insulated container, the MIT team claims it could be safely deployed by electric grid owners.

The battery has a top layer consisting of molten magnesium, the middle electrolytic layer consisting of molten magnesium-chloride, and the bottom layer consisting of molten antimony. The battery delivers current by stripping electrons from the top magnesium layer; these ions migrate through the electrolyte to form an alloy with the antimony at the bottom. When recharging, electrons from a renewable energy source recombine with the magnesium ions in the alloy at the bottom. The freed magnesium atoms then migrate back across the electrolyte to rejoin the molten magnesium at the top where it is ready to again supply energy to the grid.

Sadoway and Bradwell have founded Liquid Metal Battery Corp. to commercialize their all-liquid battery.