Wind energy production has soared in Spain, rising from 6 percent of the country’s electricity generation in 2004 to about 20 percent today. While that is certainly good news for boosters of clean energy, the surge in renewables has come with the challenge of ensuring that electric power is available. Pumped storage facilities are typically equipped with pumps and generators that move water between upper and lower reservoirs. A basic setup uses excess electricity — generated, say, from wind turbines during a blustery night — to pump water from a lower reservoir, such as behind a dam, to a reservoir at a higher elevation.
Then, when the wind ceases to blow or electricity demand spikes, the water from on high is released to spin hydroelectric turbines. 98% of world energy storage is still pumped hydro. “Among all energy storage technologies,” Koritarov notes, “pumped storage hydropower is still the only one that is mature, reliable, proven, and commercially available to provide large utility-scale energy storage.” Currently, 292 pumped storage hydro facilities are in operation worldwide, with a total capacity of 142 gigawatts. Another 46 projects, with a total capacity of 34 gigawatts, are being developed, according to the U.S. Department of Energy’s Global Energy Storage Database.
In the United States, the Federal Energy Regulatory Commission issued licenses for two projects in 2014, both in California. The Sacramento Municipal Utility District’s $800 million, 400-megawatt Iowa Hill Pumped-Storage Project involves construction of a reservoir 1,200 feet above Slab Creek Reservoir, along with an underground powerhouse and tunnels to connect the water bodies. Eagle Crest Energy Company’s $1.4 billion 1,300-megawatt Eagle Mountain Pumped Storage Project involves construction of upper and lower reservoirs at an old iron mine near Joshua Tree National Park.
Several dozen other U.S. projects are in the early planning and preliminary study stages. These include the $2.5 billion, 1,200-megawatt JD Pool Pumped Storage Hydroelectric Project in Washington State, which would site a pair of upper reservoirs between strings of wind turbines on the Columbia Plateau and a lower reservoir, located 2,400 feet down the wall of the Columbia River Gorge at an abandoned aluminum smelter near the John Day Dam. Planners envision close coordination among Columbia River dams, large arrays of wind turbines, and the proposed pumped storage facilities, which would hold water in reserve during steady winds and unleash it during calm periods.
Pumped storage hydro was first used in the 1890s in the Swiss, Austrian, and Italian Alps to provide greater flexibility for the management of water resources. The technology was widely adopted in the 1960s, 70s, and 80s to provide load shifting, which transfers electric generation from peak hours to off-peak hours of the day, according to Koritarov. The technique allows utilities to continually operate large, inflexible assets such as nuclear and coal-fired power plants at their optimal efficiency. Surplus generation from these plants is used to fill storage reservoirs; when demand peaks, the water is released to generate additional electricity