Currently the Largest-Scale Form of Grid Storage Available
Last week, California's PG&E; filed a request with regulators to study the feasibility of building a new "pumped hydro storage" facility in the Mokelumne River watershed in Amador County. It would store energy by pumping water from a low reservoir to another one that is at a higher elevation. This is done when there's a surplus of energy, such as when the wind is blowing hard at night, for example. Then when you need the energy, you open up the valves and let the water run through turbines like any other hydro station.
Photo: TVA, public domain.
PG&E; would like study the possibility of a pumped hydro storage plant ranging in size from 400 MW to 1,200 MW.
The environmental advantages of pumped hydro storage are numerous, especially in combination with intermittent sources like wind and solar, and until we get a smart grid with 'demand response' capabilities, it's probably going to stay the cheapest way to store energy.
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."
Of course, pumped hydro storage isn't cheap, and it doesn't produce energy (it's actually a net user of energy, because the pumping process isn't 100% efficient), but it's greener than burning fossil fuels.
Other Ways to Add Storage to the Grid
Increasing the size of existing hydro reservoirs is another way to store more power on the grid, but that isn't always feasible, especially in sensitive areas or where the region's hydro potential has already been tapped.
Another alternative might be to store compressed air in vast underground reservoirs to store energy, but that isn't as developed as pumped hydro.
Via Next100, Greentech
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