http://www.google.com/hostednews/ap...VKugkw?docId=371623ab59694aef9f0a02fe83faca8a
The group that oversees the U.S. power grid is proposing an experiment would allow more frequency variation than it does now without corrections, according to a company presentation obtained by The Associated Press.
In the future, more use of renewable energy from the sun and wind will mean more variations in frequency on the grid, McClelland said. Solar and wind power can drop off the grid with momentary changes in weather. Correcting those deviations is expensive and requires instant backup power to be always at the ready, he said.