Dominion Energy is set to build a $2-billion pumped hydroelectric storage unit in southwest Virginia to accommodate 240 MW of solar generation it plans to add every year through 2032, the company confirmed.
The utility has filed a preliminary permit with the Federal Energy Regulatory Commission for a traditional unit in Tazewell County, Va., and it has tapped Virginia Tech to study the feasibility of using an abandoned mine cavity as the lower reservoir of a pumped storage unit at a separate site, says Mark Mitchell, vice president of generation and construction. “With our system changing to more renewable generation, storage is needed for short-term variations in generation,” he says. The unit could range from 300 MW over 10 hours up to 1,000 MW. Dominion will decide which to build by mid-2018. It would be on line in 2027.
One Tazewell alternative includes a 3,263-ft concrete-face rockfill dam, with a 150-ft concrete-lined overflow spillway and a maximum height of 380 ft. The lower, 1,723-ft-long reservoir dam would be up to 288 ft high, with a 150-ft spillway. An underground reinforced-concrete powerhouse would have two turbines, with a combined 446-MW capacity and 10 hours of continuous generation. The second alternative also would have a 3,263-ft dam, with a maximum height of 380 ft; the lower reservoir dam would be up to 257 ft and have a concrete underground powerhouse to accommodate three turbines, with a combined capacity of 870 MW and 10 hours of continuous generation.
Will Clear, a Virginia Dept. of Mines, Minerals and Energy manager, says Dominion identified the former Bullitt coal mine, which closed in 1997, as its preferred other site. The firm will seek a FERC permit when the feasibility study is finished.