Growing water demand and reduced runoff due to drought has depleted waters feeding many hydroelectric power plants around the world—sometimes causing severe power shortages, such as in Brazil and New Zealand. The 2,080-MW Hoover Dam (Figure 4), a facility that generates power for more than a million people in Arizona, Nevada, and Southern California, is not immune to this phenomenon. According to a recent study by the Scripps Institution of Oceanography, the Colorado River system, which includes Lake Powell and Lake Mead (both manmade reservoirs), is suffering a net deficit of nearly one million acre-feet of water per year.
|4. Finding its own level. Water levels at Lake Mead have dropped to 1,099 feet mean above sea level (msl)—and keep falling mostly due to surging water demand—but some existing turbines at the 2,080-MW Hoover Dam (shown here) will only operate efficiently in waters of more than 1,050 msl. The U.S. Bureau of Reclamation, the federal body that oversees hydropower production at the power plant, recently commissioned the design and manufacture of a new “wide-head” turbine runner for one of its generating units. The design could prove useful for several hydropower plants around the world, where water shortages have spurred chronic energy crises. Source: Bureau of Reclamation|
The study estimated a 50% chance that levels at Lake Mead, already showing a deficit, could drop too low for power production. Additionally, the Scripps researchers predicted that there is a 50% chance that by 2021, Lake Mead could run dry if water demand is not curbed and climate changes continue as expected.
To combat dropping water levels, the U.S. Bureau of Reclamation, which oversees power production at the dam, recently awarded Austrian company Andritz Hydro Corp. a $3.4-million contract for the design and manufacture of a new “wide-head” turbine runner for generating unit N-8 at Hoover Dam. The “turbine runner” is the water wheel portion of the generating unit that drives the generator, and “N-8” is the designation for the number 8 unit in the Nevada wing of the power plant.
The federal agency—the largest wholesale water supplier and the second-largest producer of hydroelectric power in the U.S.—recognizes that at very low lake levels, operation of existing turbines becomes inefficient. The existing N-8 turbine, for example, is designed to operate when Lake Mead is as low as 1,050 feet mean above sea level (msl). Current Lake Mead levels stand at 1,099 feet msl—about 120 feet below the full operating level.
There are 17 commercial generators at the Hoover Dam power plant—nine in the Arizona wing and eight in the Nevada wing. The new runner is expected to be delivered to the dam in February 2012 for installation by the bureau. If it performs as anticipated, the bureau said it could ask for more runners to outfit units N-6, A-1, and N-5. These turbines could altogether cost $11.56 million. If ordered, they would arrive at the dam in November 2013, 2014, and 2015, respectively, it said.