New Battery Material Could Help Wind and Solar Power Go Big MIT Review Jan 10 2014

Utilities would love to be able to store the power that wind farms generate at night—when no one wants it—and use it when demand is high during the day. But conventional battery technology is so expensive that it only makes economic sense to store a few minutes of electricity, enough to smooth out a few fluctuations from gusts of wind.

http://www.technologyreview.com/news/523251/new-battery-material-could-help-wind-and-solar-power-go-big/