Bath County, USA
The rejuvenation of the quiet giant
For a period of nearly 20 years, the pumped storage power plant in Bath County, Virginia, USA was the largest of its kind.
Voith modernized the "quiet giant's" six turbines in 2009 to make it fit for the years to come. As a result, the considerable increase in maximum capacity means that Bath County has returned to the top of the list of the world's largest pumped storage power stations.
From the exterior, the building may seem unimpressive. On the banks of the lower reservoir, the Bath County pumped storage power station can be found nestling in the foothills of the Allegheny Mountains in the US state of Virginia. Viewed from the lake, only the power house can be seen. The vast majority of the complex, of almost twenty stories, is hidden beneath the surface of the water. This gave rise to the nickname of the power station, "quiet giant". At peak times, when around 500 000 homes and companies in Virginia require power, the spherical shutoff valves are open and more than 850 cubic meters of water per second rush down the underground pipes from the upper basin and through the six turbines located in the lower part of the building.
New pump-turbines for more power
For almost two decades, the pump-turbines were in service in the interior of the power station. In 2003, Voith was commissioned for the redevelopment. On the one hand, this was to ensure that the plant could continue to be run economically, and on the other to increase the efficiency of the turbines. To make the power station fit for the future, Voith's specialists carried out an analysis with the help of sophisticated tests and computer simulations to determine the potential for optimization. This quickly showed that a significantly higher level of efficiency could be achieved by replacing the ventilation and cooling system as well as by redesigning the stator windings.
The energy store
The upper basin of the Bath County pumped storage power station is more than a square kilometer in size and contains almost 14 million cubic meters of water. When the spherical valves are open for turbine operation, the water level in the upper basin drops by 32 meters.
High-tonnage special transportation from York
Voith dismantled the giant turbines piece by piece. Each impeller has a diameter of more than six meters and weighs around 87 tons. The impellers were replaced. The head covers were rehabilitated with new components. These components had to be delivered by special transport from the Voith plant in York some 250 miles away. The biggest challenge in all of this was the transportation of the approximately 100-ton head covers which were divided into two parts. Robert Steele, the project manager at Voith, recalls: "The head cover and the impellers were transported on a special 19 axle truck. The transport of these components was completed during the winter months. All shipment arrived at the Bath County Pumped Storage Station as planned."
Back to top place in the efficiency rankings
The new concept for the stator winding used a 540 degrees transposition instead of the original 360 degrees. This construction increases the maximum capacity of the turbines to a total of 530 megawatts - an increase of almost 25 percent. The overhaul of Bath County was completed within six years. This maintains the pumped storage power station as an efficient and reliable energy supplier. With a total capacity of more than 3030 megawatts, Bath County is once more the most powerful pumped storage power station in the world following the modernization.