Hartwell Power 
plant is referred to as a “peaking” plant – which means the power plant is designed to supply dependable power during hours of “peak” daily demand. In addition to being a very clean energy source, another major advantage of hydropower is the availability to come “on-line” (begin producing power) within a few minutes. Other types of power plants such as nuclear and fossil fuels often take several hours, at which point the peak demand has often passed. This ability to virtually produce power on demand during peak periods helps to reduce energy shortages (especially during the summer months) and makes hydropower, and the Hartwell Power plant, an exceptional resource.
Hydroelectric power is produced when water from Hartwell Lake flows through the intake section of the dam by large pipes called “penstocks”. The penstocks are located approximately 100 ft. below the surface of the reservoir. Water flows through these 24 ft. in diameter penstocks at a rate of 2 – 3 million gallons per minute when generating. The force of the water rotates the “turbines” which resemble large water wheels or fan blades. The rotating turbine causes the 41-inch diameter generator shaft to spin, which then causes the rotor to turn (the rotor is a series of magnets where the magnetic field is created). The rotor turns inside the “stator” – a stationary part of the generator made of copper coils of wire called “windings”. Electricity is produced as the rotor spins past (inside of) these windings. The generators create electricity in the form of volts. By means of transformers, the electric current produced is “stepped up” or increased in voltage from 13,800 volts to 230,000 volts for transmission to power companies or decreased in voltage for use in power plant operations. Water used in generating the power is discharged into the river below the dam, where it can be “reused” for additional purposes such as water supply and water quality needs of the Savannah River Basin.
Where Does the Power Go? Power produced at Hartwell and all other Corps operated power plants in the southeast, is marketed by the Department of Energy’s Southeastern Power Administration (SEPA). Power is sold through SEPA to private power companies and public cooperatives in the Southeastern U.S. and from there to customers of those companies. Although electricity is not sold directly to the consumer, the underlying goal of all Corps hydroelectric projects is to provide power to consumers at the lowest possible rates. Rates are set by the marketing agency and approved by the Federal Energy Regulatory Commission. Revenue from Corps power plants is returned to the U.S. Treasury.
Courtesy US Corp of Engineers