From today's EEI newsletter:

Sodium-Sulfur Batteries Could Boost Grid Strength by Storing Power

The use of room-size sodium-sulfur batteries is seen as a potential way to improve grid reliability by storing power at night for consumption during daytime peak demand periods, USA Today reported. American Electric Power already has installed a $2.5-million, 1.2-MW battery in West Virginia and plans to install another battery with twice the capacity in 2008.

Ali Nourai, AEP utility manager of distributed energy, said the device has allowed a seven-year postponement in the previously planned $1-million upgrade of a substation. The battery scheduled for installation in 2008 will be used as a backup in case of blackouts. Dan Mears, consultant for Japanese battery manufacturer NGK Insulators, said the batteries use a porcelain-like material for bridging electrodes to create a 15-year battery life. He said dozens of utilities may install the batteries.

The batteries also are seen as a way to store wind generation from strong nighttime winds for use during summer demand peaks, when the air is often stagnant. Stow Walker of Cambridge Energy Research Associates was quoted as saying: "If you've got these batteries distributed in the neighborhood, you have, in a sense, lots of little power plants. The difference between these and diesel generators is these batteries don't need fuel."
USA Today , July 5.


Sounds like a great way to deal with the variable nature of wind and solar power. Informative video here.