Yesterday, we four old geezers made a road trip, visiting a number of places, including the Just Aircraft Company to see the SuperSTOL. One of our most satisfying stops was at the upper end of Lake Jocassee on the SC-NC border, where Whitewater Falls descends 411 feet into the lake.
Just yards from the foot of the falls, a nearly hidden entrance leads to a tunnel into the mountain. At the end is a huge, 7 story high man-made cavern containing the four pump-generator turbines of Duke Power's Bad Creek Pumped Storage project. These use surplus power from the Oconee Nuclear Plant at times of low demand to pump water from Lake Jocassee in through 4 eight foot diameter pipes and then up through the roof of the cavern to the Bad Creek pond sitting 1000 feet higher on the mountain.
During times of high demand for electric power this water runs back down through the pumps, which now function as generators, emptying into lake Jocassee. Each generator produces a nominal 250 megawatts. Thus, this "gravity battery" produces one gigawatt. In fact. at "full pond", it is producing 1,320 megawatts.
NEAT!
This article has a great video tour inside the powerhouse.