That's why PG&E on Friday filed a request with state regulators for funding to study the feasibility of building a major new "pumped hydro storage" facility in the Mokelumne River watershed in Amador County. The facility, if built, would provide critical backup energy to even out the fluctuations of wind and solar energy, thus supporting California's ambitious goal of providing a third of the state's electricity from renewable power by 2020.
The wind can blow strongly for hours, only to die out for days at a time. Solar modules can gush electrons in full sun, then go dormant when clouds pass overhead. Since customers don't want their lights to flicker on and off as the weather changes, today's utilities—lacking much of any stored energy to call upon—must ramp generators powered by fossil fuels up and down as needed to keep supply in balance with demand.
As utilities add more and more wind and solar to their mix, managing the grid the old way would require a big investment in new backup natural gas-fired power plants.
Using energy storage instead to tame the output of wind and solar power--one of the key goals of the emerging "Smart Grid"—offers "multiple economic and environmental benefits," according to a recent staff report by the California Public Utilities Commission. By storing "intermittent renewable power, the state may reduce greenhouse gas emissions from carbon-based electricity production, avoid the need to build expensive new transmission lines and power plants to meet peak energy demand, increase system reliability and generate economic activity through the manufacture and operation of these . . . technologies."
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