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Hydroelectric Energy

Thu, 12/27/2007 - 12:02am — efadmin

"Water is currently the leading renewable energy source used by electric utilities to generate electric power. Hydroelectric plants operate where suitable waterways are available; many of the best of these sites have already been developed. Generating electricity using water has several advantages. The major advantage is that water is a source of cheap power. In addition, because there is no fuel combustion, there is little air pollution in comparison with fossil fuel plants and limited thermal pollution compared with nuclear plants. Like other energy sources, the use of water for generation has limitations, including environmental impacts caused by damming rivers and streams, which affects the habitats of the local plant, fish, and animal life."

"Hydroelectric energy is produced by converting the kinetic energy of falling water to electrical energy. The moving water rotates a turbine, which in turn spins an electric generator to produce electricity." Different types of hydropower facilities include:

  • Impoundment hydropower, using a dam to store the water and releasing it through turbines to meet electricity demand or maintain a desired reservoir level;
  • Pumped storage, where water is pumped from a lower reservoir to an upper reservoir when electricity demand is low, and water is released through the turbines to generate electricity when demand is higher;
  • Diversion projects, where some of the water is channeled through a canal or penstock;
  • Run-of-river projects, where the natural flow of river water is utilized to generate electricity; and
  • Microhydro projects, relatively small in size and typically used in remote locations to provide power to a single home or business.

"Hydropower provides one-fifth of the world’s electricity, second only to fossil fuels. Worldwide capacity is 776 gigawatts (GW)*, with 12% in the United States, 9% in Canada, and 8% in Brazil. When completed, China’s Three Gorges Dam, poised to become the largest hydroelectric project in the world with 18.2 GW of capacity, will move China ahead of Brazil."

"In the United States, hydropower has grown steadily, from 56 GW in 1970 to more than 95 GW today. As a percentage of the U.S. electricity supply mix, however, it has fallen to 10%, down from 14% 20 years ago, largely as a result of the rapid growth in natural gas power plants. In terms of electricity production, hydropower plants account for about 7% of America's current power needs." Hydroelectric power is more important in some parts of the country than others. "For example, the Pacific Northwest generates more than two-thirds of its electricity from 55 hydroelectric dams. The Grand Coulee dam on the Columbia River is one of the largest dams in the world, with a capacity of nearly 6,500 megawatts (MW)."

"[T]here are currently 2,378 hydro plants (not including pumped storage) in operation. These plants account for only a tiny fraction of the 80,000 dams that block and divert our rivers. As a result, there is a significant opportunity for growth according to the National Hydropower Association, which estimates that more than 4,300 MW of additional hydropower capacity can be brought online by upgrading existing facilities." "Although there are substantial undeveloped resources for hydropower, its share of the nation's total generation is predicted to decline through 2020 with almost no new hydropower capacity additions during this time. The reason for this is due to a combination of environmental concerns, regulatory complexities and pressures, and changes in economics. Due to environmental concerns, the most currently viable of the available hydropower potential is the 4.3 GW of 'incremental' capacity available at existing hydropower facilities."

"Although an inexpensive and nonpolluting energy resource, the environmental damage caused by hydropower can be serious. The most obvious effect is that fish are blocked from moving up and down the river . . . . In the Pacific Northwest, large federally owned dams have blocked the migration of coho, chinook and sockeye salmon from the ocean to their upstream spawning grounds. The number of salmon making the journey upstream has fallen 90% since the construction of four dams on the lower Snake River." "Dams can create large reservoirs submerging what used to be dry land, producing many problems. . . . This land is often composed of wetlands, which are important wildlife habitats, and low-lying flood plains, usually the most fertile crop land in the area. Population density is typically higher along rivers, leading to mass dislocation of urban centers. The Three Gorges Dam in China is expected to dislocate up to 1.9 million people."

"Another problem can occur when the land area behind the dam is flooded without proper preparation. In Brazil, the Tucurui dam was built creating a reservoir in a rain forest region, without the forest first being cleared. Later, as the plants and trees that were submerged began to rot, they reduced the oxygen content of the water, killing off the plants and fish in the water. Moreover, the rotting plants gave off large quantities of methane, a powerful global warming gas." "A similar problem has occurred in Canada, in hydro projects built by Hydro Quebec. The stones and soil in the flooded area contain naturally occurring mercury and other metals. When the land was flooded, the mercury dissolved into the water, and then into the local fish populations. The creatures that eat the fish – from bears and eagles, to the native Cree people – are suffering from mercury poisoning. Mercury poisoning can cause brain damage, birth defects, liver disorders, and other ailments."

Of course it is important to consider the environmental effects of hydropower with other alternatives. "The damage to aquatic habitat from dams may be significant, but acid rain, nitrogen deposition, and thermal pollution from coal plants also lead to aquatic damage, as well as to air pollution and global warming. Provided we dismantle the worst hydropower facilities, and improve the sustainability of others, we will be better off."

"Hydroelectric power contributed only 0.3% . . . of the total electricity generated in Indiana in 2004 . . . . Indiana has 91.4 MW of hydroelectric generation capacity . . . . Thus it can be seen that hydropower currently plays a very small role in Indiana’s generation mix."


*1GW = 1000 MW


References:
‹ Geothermal Energyup