http://www.sfgate.com/business/article/ ... 833753.php
Advanced Rail here:Some companies are pushing things uphill besides water to tap gravity for making power.
Bill Gates-backed Energy Cache is shoveling gravel up and down a slope on ski lifts. Gravity Power LLC is pushing water in and out of underground caves. Advanced Rail Energy Storage LLC, headed by James Kelly, the former vice president of transmission and distribution for Southern California Edison Co., sends electric trains between high and low rail yards.
For smaller applications, companies including GE and Siemens are developing batteries. Lithium-ion batteries, such as those produced by Siemens, are receiving the most attention, according to Roberts. Siemens technology already is being tested by Enel SpA, Italy's biggest utility, as a means of storing energy from its solar farms.
Advanced Rail, or ARES, is working a small-scale demonstration facility in Nevada that's due to start in about nine months, and a commercial-scale project in California that may eventually accommodate as much as 300 megawatts of energy. Its Nevada project will probably cost as much as $50 million.
The Nevada project will be connected to the western regional grid that's controlled by the California Independent System Operator, Kelly said. Utilities that belong to the CAL ISO including Southern California Edison Co., Pacific Gas & Electric Co. and San Diego Gas & Electric Co. "all have contracts with renewable power generators, and an ARES project could store energy from any or all of them," he said.
Nice press kit from them that outlines the issues with grid storage needs and various technologies:
http://s3.amazonaws.com/siteninja/site- ... essKit.pdf
Vid on Vimeo that illustrates their system: