Energy Storage and the Future Grid

Energy storage allows grid operators to shift electricity in time, storing surplus generation for use when demand is high or variable generation is low, and today the large majority of the world's installed grid-scale storage capacity, generally cited at more than 90 percent, still consists of pumped-storage hydropower, a mature technology that pumps water uphill into a reservoir when electricity is cheap or abundant and releases it back downhill through turbines to generate power when it is needed. The Bath County Pumped Storage Station in Virginia, completed in 1985 with a capacity of roughly 3,000 megawatts, remains the largest facility of its kind in the world, illustrating how much storage capacity a single well-sited pumped-hydro plant can provide compared with most other storage technologies built to date.