The largest hydroelectric dam in the United States is the Grand Coulee Dam on the Columbia River in Washington state. Construction.

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1 Another potential drawback of waterwheel power plants is safety. Such plants, including the wheel itself, have to be fenced off so that they do not injure curious people who get too close. This fencing, combined with the plant itself, has the potential to become an eyesore, though manufacturers attempt to make the equipment as visually attractive as possible. A final drawback stems from the variability of water flow. During spring runoff, when snow is melting and rivers run rapidly, the amount of power generated is much higher than in, say, August, when rivers are running low, providing less flow. Issues, challenges, and obstacles of hydropower The primary issue surrounding the use of waterwheels is ownership rights. Any stream or river almost certainly flows through property owned by many people. The river itself is common property; no one individual owns it. If one property owner builds a waterwheel, other property owners along the river might object, particularly if they are uncertain about the effects the wheel might have downstream. Another challenge concerns distribution of the power. One property owner might build a waterwheel for personal use, but larger waterwheels in high flow streams might generate enough electricity for multiple users. The questions then become how that power is going to be distributed and how its users will divide the cost of constructing the waterwheel. Hydroelectricity Hydroelectricity is any electricity generated by the energy contained in water, but most often the word is used to refer to the electricity generated by hydroelectric dams. These dams harness the kinetic energy contained in the moving water of a river and convert it to mechanical energy by means of a turbine. In turn, the turbine converts the energy into electrical energy that can be distributed to thousands, even millions, of users. One of the most prominent hydroelectric dams in the United States is Hoover Dam on the Colorado River along the border between Arizona and Nevada. Construction on the dam began in It was completed five years later, under budget, for $165 million. Behind the dam is a reservoir, Lake Mead, containing about 1.24 trillion gallons of water. The dam is 726 feet (221 meters) tall, and at its base is 660 feet (201 meters) thick. Its 4.5 million cubic yards of concrete would be enough Alternative Energy, 2nd Edition 323

2 Water Energy to build a two-lane highway from Seattle, Washington, to Miami, Florida. Each year, the dam produces 4 billion kilowatt-hours of electricity, enough to serve 1.3 million people. The largest hydroelectric dam in the United States is the Grand Coulee Dam on the Columbia River in Washington state. Construction Aerial view of Hoover Dam, which was built in the 1930s to harness the mighty Colorado River. It created the reservoir of Lake Mead. ANDY Z/SHUTTERSTOCK.COM. 324 Alternative Energy, 2nd Edition

3 began on the dam in 1933 and was completed in The original purpose of the dam, however, was not to generate electricity but to irrigate one-half million acres of agricultural land. From 1966 to 1974, the power-producing ability of the dam was expanded with the addition of six new electrical generators. The scope of the Grand Coulee Dam continues to amaze visitors. It is the largest concrete structure in the United States, at 11,975,521 cubic yards (9,155,943 cubic meters). At its widest point, it is almost exactly 1 mile (1.6 kilometers) long. At 550 feet (167 meters) tall, it is twice the height of the Statue of Liberty and more than twice the height of Niagara Falls. Its reservoir, Roosevelt Lake, contains up to 421 billion cubic feet of water. Its four power plants and 33 generators have a combined capacity of 6,809 megawatts of electrical power. A hydroelectric dam consists of the following components: Dam: The dam is built to hold back water, which is contained in a reservoir. This water is regarded as stored energy, which is then released as kinetic energy when the dam operators allow water to flow. Sometimes these reservoirs, such as Lake Mead, are used as recreational lakes. Intake: Gates open to allow the water in the reservoir to flow into a penstock, which is a pipeline that leads to the turbine. The water gathers kinetic energy as it flows downward through the penstock, which serves to shoot the water at the turbine. Turbine: A turbine is in many ways like the blades of a windmill or the veins of a pinwheel. The water flows past the turbine, striking its blades and turning it. The most common turbine design used in large, modern hydroelectric power plants is the Francis turbine, which is a disc with curved blades. The Francis turbine was developed by British-American engineer James B. Francis ( ), who began and ended his professional career in the United States as an engineer at the Locks and Canal Company in Lowell, Massachusetts. In the largest hydroelectric plants, these turbines are enormous, weighing up to 170 tons or more. The largest ones turn at a rate of about 90 revolutions per minute. Generator: The turbine is attached by a shaft to the generator, which actually produces the electricity. Generators are based on the principle of electromagnetic induction, discovered by British Alternative Energy, 2nd Edition 325

4 scientist Michael Faraday ( ) in Faraday discovered that as a metal that conducts electricity, such as copper wire, moves through a magnetic field, an electrical current can be induced, or created, in the wire from the flow of electrons. The mechanical energy of the moving wire is therefore converted into electrical energy. In a hydroelectric plant, the mechanical energy is supplied by the turbine, which in turn is powered by the kinetic energy of moving water. Transformer: A transformer converts the alternating current produced by the generator and converts it into a higher voltage current. Power lines: Power lines transmit the power out of the power plant to the electrical grid, where it can be used by consumers. Outflow: Pipes called tailraces channel the water back into the river downstream. A view of turbines in the power house at the Bonneville Dam in Oregon. RIGUCCI/SHUTTERSTOCK.COM. 326 Alternative Energy, 2nd Edition

5 Hydroelectric power plants come in three basic types: High head: Head refers to the difference in level between the source of the water and the point at which energy is extracted from it. Assuming other things are equal, the higher the head, the more power is generated. A high head hydroelectric plant is one that uses a dam and a reservoir to provide the kinetic energy that powers the plant. Most major hydroelectric plants are of this type. Run-of-the-river: In contrast, a run-of-the-river plant requires either no dam or a very low dam. It operates entirely, or almost entirely, from the flow of the river s current. No energy is stored in a reservoir. These hydroelectric plants are generally small, producing less than about 25 kilowatts. Pumped-storage: Some hydroelectric plants rely on a system of two reservoirs. The upper reservoir operates exactly as the reservoir does in a high head plant: Water from the reservoir flows through the plant to turn the turbines, then exits the plant and reenters the river downstream. In a pumped-storage plant, the water exiting the plant is stored in a lower reservoir rather than reentering the river. Using a reversible turbine, normally during off-peak hours (or hours when power usage is low, usually at night), water is then pumped from the lower to the higher reservoir to refill it. This gives the plant more water to use to generate electricity. Current uses of hydroelectricity During the 1930s, a large number of hydroelectric dams were built on the waterways of the United States. Many of these dam projects were the result of the Great Depression, which occurred during that decade. During the Depression, the U.S. government sponsored public-works projects designed to put people to work and recharge the economy. These dams, such as Hoover Dam and the many dams that were built along the Columbia River in the Pacific Northwest, produced hydroelectric power. By the end of the 1930s, they were meeting about 40 percent of the nation s electricity needs. Many dams were also built in a seven-state region around the Tennessee River Valley under the guidance of the Tennessee Valley Authority (TVA). During much of the first decade of the 2000s, around 2,000 hydroelectric dams in the United States provided about 9 to 10 percent of the nation s electricity. By 2010 that percentage was down Alternative Energy, 2nd Edition 327

6 Roll on, Columbia In the 1940s, social activist and folksinger Woody Guthrie ( ) was hired by the Bonneville Power Administration (BPA) to write folk songs about the dams being built on the Columbia River. (The Columbia River, which begins in British Columbia, winds its way more than 1,200 miles [1,930 kilometers] to the Pacific Ocean. During its final stretch to the sea, it becomes the natural border between Oregon and Washington.) Over a period of about a month, Guthrie wrote 26 folk songs under the general title Columbia River Ballads. One of the most popular of these songs was Roll on, Columbia, which the state of Washington adopted as its official folk song in Among the hydroelectric dams on the Columbia River are the Grand Coulee Dam, The Dalles Dam, and the Bonneville Dam. At the time of their construction, the dams were intended to provide power but also to help with the irrigation of farm lands and to provide a safer passageway for ships. In Roll on, Columbia, Guthrie sings about the benefits of hydroelectric dams, but also praises the common working man whose hard labor built Folk performer Woody Guthrie. COURTESY OF THE LIBRARY OF CONGRESS. the dams. He notes that the construction workers tamed the wild river, contending with rapids and waterfalls, for the benefit of all people. Many of Guthrie s BPA songs were re-released on CD and in MP3 format. to 6 percent. The share of electricity produced by hydroelectric dams decreased largely because most of the best sites for hydroelectric dams already had one, plus there were serious concerns about the environmental impact of building new dams. As a result, practically no new large dams were being built to keep up with America s appetite for ever-more power. However, developing countries such as China in search of greatly expanded electricity production, and with far fewer environmental rules in place were constructing large hydroelectric dams at a frenetic pace. Worldwide in 328 Alternative Energy, 2nd Edition

7 2010, hydroelectric dams provided a total of around 800,000 megawatts of power to over a billion users. Benefits of hydroelectricity The chief benefit of hydroelectric power, like the power provided by waterwheels, is that fossil fuels do not have to be burned. Fossil fuels release particulate matter and greenhouse gases (such as carbon dioxide and sulfur dioxide) into the atmosphere, where they produce smog and contribute to global warming and acid rain. Hydroelectric power is also free in the sense that fuel does not have to be purchased to produce it, although money has to be spent to build and maintain the power plant and to distribute power to consumers. The World s Smallest Hydroelectric Power Plant Another major benefit of hydroelectric energy is that it is renewable. Over time, it will become more and more expensive to extract fossil fuels from the earth until eventually these fuels will be entirely depleted. Hydroelectric power will remain available as long as there are rivers. Hydroelectric energy, in contrast to oil, is not dependent on imported fuels from other countries, which could be cut off by one or more of those countries and make a nation vulnerable to political pressures from them. Hydroelectric dams can also have secondary benefits. They provide flood control on rivers, and their reservoirs often serve as lakes for recreational activities such as boating and swimming. Drawbacks of hydroelectricity Hydroelectric energy has always been thought of as clean energy. However, scientists and engineers have started to understand that hydroelectric power has significant drawbacks as well. One drawback is that damming rivers floods large areas of land. Construction of the Three Gorges Dam on China s Yangtze River, completed in 2008, resulted in the forced evacuation of 1.4 million people from the reservoir area. Thirteen cities, 140 small towns, and over 1,350 small villages had to be abandoned because of the dam. On file at the U.S. Patent and Trademark Office is patent number 6,239,501. The patent is held by Canadian inventor Robert Komarechka, who conceived the idea that a tiny hydroelectric power plant embedded in the soles of shoes could provide power to run cell phones, MP3 players, laptop computers, and other modern electronic gadgets. The design is based on the way people walk. When a person takes a step, force is exerted downward on the heel. The foot then rolls forward, so that force is exerted on the toe. Komarechka found a way to harness this power by inserting sacs of fluid in the soles of shoes, one at the heel end and one at the toe end. Connecting the sacs is a conduit through which the fluid, a gel-like substance, can flow. As it flows, it turns a tiny turbine that is attached to a microgenerator, which in turn produces electrical power. A tiny socket allows the user to connect an electronic gadget to the power source, either directly at the shoe or at a power pack attached to, perhaps, a person s belt. Alternative Energy, 2nd Edition 329