Most of the folks around Smith Mountain Lake probably know that the dam generates much of the electricity used in their vicinity. But what most of us don’t know is exactly how that is done. It is a rather interesting process that takes running water and converts it into energy for our homes, etc.
|Operation of the Smith Mountain Lake Dam project makes maximum use of one of our natural resources – water – through a process called pumped storage. Water stored in Smith Mountain Lake first drops through the turbine generators in the Smith Mountain Dam powerhouse to produce electricity. Instead of allowing all of the spent water to run away downstream, much is caught and held by Leesville Dam, the lower dam in the project, to be pumped back into Smith Mountain Lake later for re-use. A portion of the water goes through turbine generators at Leesville, generating additional electricity.
Smith Mountain is a pumped storage project that utilizes an upper reservoir (Smith Mountain Lake) and a lower reservoir (Leesville Lake.) The water that is stored in Smith Mountain Lake first passes through turbine generators in the powerhouse to produce electricity and is then discharged into Leesville Lake. Most of this water is retained in Leesville Lake and is pumped back into Smith Mountain Lake for reuse. A portion of the water goes through the turbine-generators at the Leesville powerhouse to generate additional electricity and to meet the minimum discharge requirements of the project’s Federal Energy Regulatory Commission (FERC) license.
The Smith Mountain development utilizes a two-foot power pool. This means that when Smith Mountain generates power by passing water through the turbines, the Smith Mountain lake level can fluctuate up to two feet before Leesville Lake becomes full. In other words, a two-foot decrease in Smith Mountain results in Leesville Lake increasing thirteen (13) feet or from a minimum elevation of 600 feet to a maximum elevation of 613 feet. Once Leesville is full, power cannot be produced at Smith Mountain until some portion of the water is pumped back to Smith Mountain Lake. There is no set schedule for operating the project. Generation generally takes place when the electricity demand is high and water from the lower reservoir is pumped back into the upper reservoir when the power demand is low. The operation of the project can change on an hourly basis depending on system demand. The normal full pond elevation at Smith Mountain is 795 feet but the normal operating range under full pond conditions is considered to be between 793 feet and 795 feet because of the two-foot power pool. The normal operating range for Leesville is between 600 feet and 613 feet. Under low in-flow conditions, the pond elevation at Smith Mountain can fall below 793 feet.
This information is from the Smith Mountain Lake Dam Project Site.