The following information about the powerplant is from the
Bureau of Reclamation:
"Where is the powerplant located?
"In a U-shaped structure at the base of the dam. Each powerplant wing is 650 feet long (the length of almost 2 football fields) and rise 299 feet (nearly 20 stories) above the powerplant foundation. In all of the galleries of the plant there are 10 acres of floor space.
What is the capacity of the Hoover Powerplant?
There 17 main turbines in the Hoover Powerplant -- nine on the Arizona wing and eight on the Nevada wing. The original turbines were replaced through an uprating program between 1986 and 1993. The plant has a nameplate capacity of about 2,080 megawatts. This includes the two station-service units (small generating units that provide power for plant operations), which are rated at 2.4 megawatts each. With the main units having a combined rated capacity of 2,991,000 horsepower, and two station-service units rated at 3,500 horsepower each, the plant has a rated capacity of 2,998,000 horsepower.
How does the water reach the turbines?
Through four penstocks, two on each side of the river. Wicket gates control water delivery to the units.
Under what heads do the turbines operate?
Maximum head (vertical distance the water travels), 590 feet; minimum, 420 feet; average, 510 to 530 feet.
When were the power installations in the plant completed, and of what do they consist?
The installation of the last generating units was completed in 1961. A plant uprating was completed in 1993, so presently there are fifteen 178,000 horsepower, one 100,000 horsepower, and one 86,000 horsepower Francis-type vertical hydraulic turbines in the Hoover powerplant. There are also thirteen 130,000 kilowatt, two 127,000 kilowatt, one 61,500 kilowatt, and one 68,500 kilowatt generators. All machines are operated at 60 cycles. The two 2,400 kilowatt station-service units are driven by Pelton water wheels. These provide electrical energy for lights and for operating cranes, pumps, motors, compressors, and other electrical equipment within the dam and powerplant."
The following information is from Wikipedia:
Power plant and water demands
"Excavation for the powerhouse was carried out simultaneously with the excavation for the dam foundation and abutments. A U-shaped structure located at the downstream toe of the dam, its excavation was completed in late 1933 with the first concrete placed in November 1933. Filling of Lake Mead began February 1, 1935 even before the last of the concrete was poured that May. The powerhouse was one of the projects uncompleted at the time of the formal dedication on September 30, 1935—a crew of 500 men remained after the dedication to finish it and other structures. To make the powerhouse roof bombproof, it was constructed of layers of concrete, rock, and steel with a total thickness of about 3.5 feet (1.1 m), topped with layers of sand and tar.
In the latter half of 1936, water levels in Lake Mead were high enough to permit power generation, and the first three Francis turbine-generators, all on the Nevada side, began operating. In March 1937, one more Nevada generator went online and the first Arizona generator by August. By September 1939, four more generators were operating and the dam's power plant became the largest hydroelectricity facility in the world. The final generator was not placed in service until 1961, bringing the maximum generating capacity to 1345 megawatts at the time. Original plans called for 16 large generators, eight on each side of the river, but two smaller generators were installed instead of one large one on the Arizona side for a total of 17. The smaller generators were used to serve smaller municipalities at a time when the output of each generator was dedicated to a single municipality, before the dam's total power output was placed on the grid and made arbitrarily distributable. The present contracts for the sale of electricity expire in 2017.
Before water from Lake Mead reaches the turbines, it enters the intake towers and enters four gradually narrowing penstocks which funnel the water down towards the powerhouse. The intakes provide a maximum hydraulic head (water pressure) of 590 ft (180 m) as the water reaches a speed of about 85 mph (140 km/h). The entire flow of the Colorado River passes through the turbines. The spillways and outlet works (jet-flow gates) are rarely used. The jet-flow gates, located in concrete structures 180 feet (55 m) above the river and at river level, may be used to divert water around the dam in emergency or flood conditions, but have never done so, and in practice are only used to drain water from the penstocks for maintenance. Following an uprating project from 1986 to 1993, the total gross power rating for the plant, including two 2.4 megawatt Pelton turbine-generators that power Hoover Dam's own operations is a maximum capacity of 2080 megawatts. The annual generation of Hoover Dam varies. The maximum net generation was 10.348 TWh in 1984, and the minimum since 1940 was 2.648 TWh in 1956. The average has been about 4.2 TWh/year.
Control of water was the primary concern in the building of the dam. Power generation has allowed the dam project to be self sustaining: proceeds from the sale of power repaid the 50-year construction loan, and those revenues also finance the multi-million dollar yearly maintenance budget. Power is generated in step with and only with the release of water in response to downstream water demands. Lake Mead and downstream releases from the dam provide water for both municipal and irrigation uses. Water released from the Hoover Dam eventually reaches the All-American Canal for the irrigation of over 1,000,000 acres (400,000 ha) of land. Water from the lake serves 8 million people in Arizona, Nevada and California."