By David Wagman, Chief Editor
Our hardhat-wearing tour group, made up of delegates from the Renewable Energy World Conference and Expo in nearby Las Vegas, is more than 700 feet underground. We are making our way through a rough-cut tunnel that connects the turbine hall at the base of Hoover Dam to a second tunnel. This tunnel, also cut through hard volcanic rock, contains one of four 13-foot-tall penstocks. Standing on top of the penstock we can feel the vibration and hear the roar as water flows from Lake Mead upstream of the dam to one of 17 main turbines housed in this storied hydroelectric facility.
Upon its completion in 1936, Hoover Dam was trumpeted as one of the Wonders of the World. As a feat of civil engineering and flood control, yes, but as a power generator, the behemoth’s 2,080 MW of capacity is used for no more than peaking power. On this particular day, the total output was not much more than 25 percent of capacity. That’s because electricity production ranks a distant second to meeting agricultural water demand in Arizona and California. Flood control and irrigation were the primary reasons Hoover Dam was conceived in the 1920s. Hydroelectric power was almost an afterthought, but a lucky one at that. Electric power sales paid off the dam’s construction debt back in 1987. Today, rates are high enough to cover dam maintenance costs but aren’t meant to generate a financial profit for the U.S. Bureau of Reclamation, which owns and operates the dam.
Hoover Dam’s original turbines were all replaced through an uprating program between 1986 and 1993. With the uprates, there are 15 132 MW, one 75 MW and one 64 MW Francis-type vertical hydraulic turbines in place. There are also 13 130 MW, two 127 MW, one 61.5 MW and one 68.5 MW generators. Two 2.4 MW 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.
 Renewable Energy World delegates pass through a tunnel 700 feet underground leading to a penstock. |
Given the vintage of much of the dam’s power generating equipment, repairs and replacement parts are made on site in a machine shop whose aluminum doors and architectural details are distinctly Art Deco, a surprising artistic detail at the base of this massive concrete dam. Supplies and machinery that are too big to navigate a single-track, rough-hewn road from the canyon rim to the power plant are lowered via a cable system that has been in place since construction first began.
Transmission lines were no doubt among the first electric infrastructure constructed at the site. These lines imported power to the dam construction project, where much of it was used to operate a refrigeration plant. Refrigeration proved necessary because the chemical heat from the setting concrete was so great that the dam would still be cooling today had it been left untouched. So to accelerate the cooling, more than 580 miles of one-inch steel pipe was embedded in the concrete. Ice water circulated through the pipe from the refrigeration plant, which could produce 1,000 tons of ice in 24 hours. Cooling was completed in March 1935.