24-03-2012, 02:54 PM
HYDROELECTRIC POWER GENERATION
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Introduction
Hydropower is produced when kinetic energy in flowing water is converted into electricity.
Hydropower has been a significant source of electrical energy in the United States since the early
1900s when manufacturers recognized and harnessed its tremendous potential to develop and build
entire industries. Traditionally, hydropower has been a low-cost, reliable energy source. It utilizes a
renewable fuel (water) that can be sustained indefinitely, and is free of fossil fuel emissions. And
because hydroelectric generators are especially suited for providing peaking power, hydropower
complements thermal generation and improves overall power production efficiency. Hydroelectricity
presently constitutes approximately 10 percent of the United States’ energy supply, which is enough
to meet the needs of 28.3 million consumers.
Nomenclature
The following terms are commonly used to describe hydroelectric equipment, facilities, and
production:
Afterbay (tailrace). The body of water immediately downstream from a power plant or pumping
plant.
Appurtenant structures. Intakes, outlet works, spillways, bridges, drain systems, tunnels, towers, etc.
Auxiliary power. The electric system supply to motors and other auxiliary electrical equipment
required for operation of a generating station.
Base loading. Running water through a power plant at a roughly steady rate, thereby producing
power at a steady rate.
Base load plant. Powerplant normally operated to take all or part of the minimum load of a system,
and which consequently runs continuously and produces electricity at an essentially constant rate.
Operated to maximize system mechanical and thermal efficiency and minimize operating costs.
Bulkhead. A one-piece fabricated steel unit that is lowered into guides and seals against a frame
to close a water passage in a dam, conduit, spillway, etc.
Bulkhead gate. A gate used either for temporary closure of a channel or conduit before dewatering
it for inspection or maintenance or for closure against flowing water. Bulkhead gates nearly
always operate under balanced pressures.
passage of water. Used to provide a cheaper or more easily handled means of temporary closure
than a bulkhead gate.
Storage reservoir. A reservoir having the capacity to collect and hold water from spring time
snowmelts. Retained water is released as necessary for multiple uses such as power production,
fish passage, irrigation, and navigation.
Surge tank. A large tank, connected to the penstock, used to prevent excessive pressure rises and
drops during sudden load changes in plants with long penstocks.
Switchyard. An outdoor facility comprised of transformers, circuit breakers, disconnect switches,
and other equipment necessary to connect the generating station to the electric power system.
Tailrace. See Afterbay.
Tailwater. The water in the natural stream immediately downstream from a dam.
Transformer. An electromagnetic device used to change the magnitude of voltage or current of
alternating current electricity or to electrically isolate a portion of a circuit.
Trashrack. A metal or reinforced concrete structure placed at the intake of a conduit, pipe, or tunnel
that prevents large debris from entering the intake.
Trashrake (trash rake). A device that is used to remove debris, which is collected on a trashrack
to prevent blocking the associated intake.