Hydroelectricity
Hydroelectricity is a form of energy generated by harnessing the power of flowing or falling water to produce electricity. It is recognized as a clean and renewable energy source, as it does not emit greenhouse gases during operation. The concept began to materialize in the late 19th century with advancements in electrical engineering, particularly following the invention of the dynamo by Michael Faraday and the practical use of electricity by Thomas Edison. The technology relies heavily on turbines, which convert the mechanical energy of water flow into electrical energy.
The capacity for hydroelectric power generation is influenced by factors such as the height from which water falls, which is categorized into low-head and high-head facilities. Major hydroelectric projects, like the Three Gorges Dam in China, exemplify the scale at which this energy source can be developed, although they often come with significant social and environmental impacts, including displacement of communities and alteration of ecosystems. Hydroelectric plants also play a crucial role in flood control and water supply management, making them appealing to governments, especially in regions with limited fossil fuel access. However, challenges such as high construction costs and seasonal water variability can complicate their efficiency and sustainability.
Hydroelectricity
Because hydroelectricity uses falling water rather than fossil fuels for its production, it does not contribute greenhouse gases (GHGs) to the atmosphere. It is both a clean and a renewable energy source.
Background
Hydroelectricity is a twentieth-century phenomenon. Although the use of moving water for the production of mechanical energy is ancient (water wheels go back to ancient times), the use of falling water to create electricity awaited knowledge about using electricity as a motive power. Although Michael Faraday invented a dynamo that produced an electric current in 1831, the concept of using an electric current to move energy from one place to another awaited the appearance of Thomas Alva Edison and the electric light in the 1870s. Critical for hydroelectricity were the understanding that electricity could be produced by other kinds of mechanical energy, the development of machines that could use mechanical energy to induce an electric current (generators), and knowledge of the transmission systems that made it possible to move electricity across significant distances. In 2023, the US Energy Information Administration estimated that hydroelectricity accounted for 6 percent of total US electricity generation.
Early History of Hydroelectricity
The invention of the turbine allowed water running through a containing vessel to produce mechanical energy that could, in turn, generate an electrical current. The turbine designed by James Francis was the earliest to appear, but modifications made by Lester Allan Pelton and later Viktor Kaplan adapted the turbine to use in situations involving falls of significant distance. Generally, hydraulic installations are classified into either low-head facilities, where the drop is on the order of 15 meters, and high-head facilities, with a drop of more than 60 meters. The height of the head determines whether a vertical- or horizontal-impulse turbine is used. The determining factor is the continuous volume of water passing through the turbine.
Initially, use was made of sites that both were close to manufacturing facilities and involved large volumes of water falling substantial distances. The most notable example was Niagara Falls. Sites with this combination of features are relatively rare, however. Most suitable sites tend to be located at the base of chains of mountains, where they can make use of the water generated by large amounts of melting snow. The drawback to such sites is that the amount of water they generate is seasonally variable. The very high capital costs of constructing such installations make it essential that they be sited where the flow of water is steady, allowing them to operate year-round. Thus, in the twentieth century, operators of hydroelectric facilities began to build holding ponds or reservoirs. These structures allowed them to collect water when its flow was great and store it for later use during drier seasons.
Major Facilities
The common preference, especially among governments, for economies of scale has led to the development of a number of very large hydroelectric facilities, of which the largest, in China, is the Three Gorges Dam in Hubei province. Governmental priorities also entailed building a large reservoir to ensure that there would always be sufficient water to operate the facility’s generators. This construction in turn flooded some one hundred thousand of China’s towns and villages, forced one million people to move, and submerged about 400 hundred square kilometers of farmland.
Other large facilities include the Itaipu, serving both Paraguay and Brazil; the Yacyreta, serving Argentina and Brazil; the Krasnoyarsk, the Bratsk, the Ust-Ilim, and the Volgograd in Russia; the Minamiaiki in Japan; and the Chief Joseph in the United States. The United States also has a number of facilities built during the 1920s and 1930s, notably the Hoover Dam, the Glen Canyon Dam, the Grand Coulee, and the Bonneville facility. Although many of these were built in sparsely inhabited areas, they have had an effect on the human populations in their area, though perhaps none so much as the Three Gorges Dam in China.
Environmental Effects of Hydroelectricity
Although the construction of large hydroelectric projects has benefitted the population served by the electricity they produce, the heavy use of hydroelectricity in some parts of the world has also had some negative effects. Among the advantages are the production of low-cost electricity without burning fossil fuels (although many hydroelectric plants have backup fossil fuel generators to keep the generation steady); the creation of dams that can also be used for flood control, controlling water supply in urban areas with large populations; and the creation of artificial lakes that can provide many recreational opportunities.
The disadvantages include high construction costs, conflicting demands for flood control and hydroelectric generating capacity, the withdrawal of substantial amounts of land from agricultural use (as in China), degradation of fish habitat, and the elimination of trees on the flooded land. In several cases, Indigenous communities have lost the land that they traditionally used for their sustenance. The Hoover Dam in the United States experienced unique issues due to drought in 2022. Lake Mead, the reservoir formed by the Hoover Dam, had been drying up for decades due to an extended megadrought, which was problematic for the dam's water supply. If the lake were to dry up completely, the Hoover Dam would no longer be able to generate hydroelectric power. In 2022, critically low water levels led US officials to announce cuts in the water supplies to Arizona, Nevada, and Mexico, which would inevitably have economic, social, and environmental repercussions.
Context
The steadily growing need of human populations for electricity has created a continuing demand for large facilities that appear to place little burden on the environment. By producing electricity without burning fossil fuels and at low cost, hydroelectric plants are seductive, especially to the politicians who make public policy. Although the best sites have already been taken, there are still a number of lesser locations that may yet be claimed. For many countries in the developing world, hydroelectricity has a large attraction, especially if those countries lack local sources of fossil fuels.
Key Concepts
- fossil fuels: fuels, such as coal, gas, or oil, created during early geologic eras
- generator: a mechanical device whose rotational movement around magnets produces an electrical current
- head: the fall of the water at a site selected for production of hydroelectricity
- reservoir: a gathering place for water held in reserve for later hydroelectric production
- turbine: an enclosed vessel containing rotating parts turned by the passage of a fluid, such as water or air
Bibliography
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