Hydroelectricity
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Hydroelectricity is electricity produced by hydropower. Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator, although less common variations use water's kinetic energy or dammed sources, such as tidal power. Hydroelectricity is a renewable energy source.
The energy extracted from water depends not only on the volume but on the difference in height between the source and the water's outflow. This height difference is called the head. The amount of potential energy in water is proportional to the head. To obtain very high head, water for a hydraulic turbine may be run through a large pipe called a penstock.
While many supply public electricity networks, some hydroelectric projects were created for private commercial purposes. For example, aluminium processing requires substantial amounts of electricity, and often dedicated hydroelectric projects are built to serve aluminium electrolytic plants. In the Scottish Highlands there are examples at Kinlochleven and Lochaber, constructed during the early years of the 20th century. In Suriname, the 'van Blommestein' lake, dam and power station were constructed to provide electricity for the Alcoa aluminum industry.
In parts of Canada (the provinces of British Columbia, Manitoba, Ontario, Quebec and Newfoundland and Labrador) hydroelectricity is used so extensively that the word "hydro" is used to refer to any electricity delivered by a power utility. The government-run power utilities in these provinces are called BC Hydro, Manitoba Hydro, Hydro One (formerly "Ontario Hydro"), Hydro-Québec and Newfoundland and Labrador Hydro respectively. Hydro-Québec is the world's largest hydroelectric generating company, with a total installed capacity (2005) of 31,512 MW.
Advantages
The major advantage of hydro systems is elimination of the cost of fuel,hense the emission of the greenhouse gas produced when buring them. (Although there is some greenhouse gas emission during construction and operation of the hydro system, the total amount per unit of electricity is much lower than fossil fuel plants.) Hydroelectric plants are immune to price increases for fossil fuels such as oil, natural gas or coal, and do not require imported fuel. Hydroelectric plants tend to have longer lives than fuel-fired generation, with some plants now in service having been built 50 to 100 years ago. Operating labor cost is usually low since plants are automated and have few personnel on site during normal operation.
Reservoirs created by hydroelectric schemes often provide facilities for water sports, and become tourist attractions in themselves. In some countRIES, farming fish in the reservoirs is pretty common. Multi-use dams installed for irrigation can support the farm with relatively constant water supply.Large hydro dam can control flood,which may save thousands of people living in downstream by eliminate or reduce the impact of big flood. Some big hydro dam can creat a huge deep reserviors and eliminate the rapids, so that big boat can be used to improve transportation. With modern technology,a hydroelectric plant may have relatively low construction cost, providing a useful revenue stream to offset the cost of dam operation. It was calculated that just after 5 to 7 years of full power of Three Gorge Dam, they can cover all the cost by selling the electricity it generates.
Pumped storage plants currently provide the only commercially important means for energy storage on a scale useful for a utility. Low-value generation in off-peak times occurs because fossil-fuel and nuclear plants cannot be entirely shut down on a daily basis. This energy is used to store water that can be released during high load daily peaks. Operation of pumped-storage plants improves the daily load factor of the generation system.
Disadvantages
Hydroelectric projects can be disruptive to surrounding aquatic ecosystems. For instance, studies have shown that dams along the Atlantic and Pacific coasts of North America have reduced salmon populations by preventing access to spawning grounds upstream, even though most dams in salmon habitat have fish ladders installed. Salmon smolt are also harmed on their migration to sea when they must pass through turbines. This has led to some areas barging smolt downstream during parts of the year. Turbine and power-plant designs that are easier on aquatic life are an active area of research. Since damming and redirecting the waters of the Platte River in Nebraska for agricultural and energy use, many native and migratory birds such as the Piping Plover and Sandhill Crane have become increasingly endangered. Large-scale hydroelectric dams, such as the Aswan Dam and the Three Gorges Dam, have created environmental problems both upstream and downstream.
Generation of hydroelectric power impacts on the downstream river environment. Water exiting a turbine usually contains very little suspended sediment, which can lead to scouring of river beds and loss of riverbanks. Since turbines are often opened intermittently, rapid or even daily fluctuations in river flow are observed. For example, in the Grand Canyon, the daily cyclic flow variation caused by Glen Canyon Dam was found to be contributing to erosion of sand bars. Dissolved oxygen content of the water may change from pre-construction conditions. Water exiting from turbines is typically much colder than the pre-dam water, which can change aquatic faunal populations, including endangered species.
The reservoirs of hydroelectric power plants in tropical regions may produce substantial amounts of methane and carbon dioxide. This is due to plant material in flooded areas decaying in an anaerobic environment, and forming methane, a very potent greenhouse gas. According to the World Commission on Dams report, where the reservoir is large compared to the generating capacity (less than 100 watts per square metre of surface area) and no clearing of the forests in the area was undertaken prior to impoundment of the reservoir, greenhouse gas emissions from the reservoir may be higher than those of a conventional oil-fired thermal generation plant [1]. In boreal reservoirs of Canada and Northern Europe, however, greenhouse gas emissions are typically only 2 to 8% of any kind of conventional thermal generation. The contributive effect of forest decay can be mitigated by a new class of underwater logging operation targeting drowned forests.[1]
Another disadvantage of hydroelectric dams is the need to relocate the people living where the reservoirs are planned. In many cases, no amount of compensation can replace ancestral and cultural attachments to places that have spiritual value to the displaced population. Additionally, historically and culturally important sites can be flooded and lost. Such problems have arisen at the Three Gorges Dam project in China, the Clyde Dam in New Zealand and the Ilısu Dam in Southeastern Turkey.
Recreational users of the reservoir or downstream areas are exposed to hazards due to changing water levels, and must be wary of power plant intakes and spillway operation. Ontario Power Generation's brochure "Stay Clear, Stay Safe" can be downloaded at www.opg.com/power/hydro/ The brochure describes why people need to exercise extreme care when near hydroelectric dams, stations, and surrounding waterways.
Some hydroelectric projects also utilize canals, typically to divert a river at a shallower gradient to increase the head of the scheme. In some cases, the entire river may be diverted leaving a dry riverbed. Examples include the Tekapo and Pukaki Rivers. The creation of a dam in a geologically inappropriate location may cause disasters like the one of the Vajont Dam in Italy, where almost 2000 people died, in 1963. Failures of large dams, while rare, are potentially serious — the Banqiao Dam failure in China resulted in the deaths of 171,000 people and left millions homeless, more than some estimates of the death toll from the Chernobyl disaster. Dams may be subject to enemy bombardment during wartime, sabotage and terrorism. Smaller dams and micro hydro facilities are less vulnerable to these threats.
Hydro-electric facts
Oldest hydro-electric power stations:
- Appleton, Wisconsin, USA completed 1882, A waterwheel on the Fox river supplied the first commercial hydroelectric power for lighting to two paper mills and a house, two years after Thomas Edison demonstrated incandescent lighting to the public. Within a matter of weeks of this installation, a power plant was also put into commercial service at Minneapolis.
- Duck Reach, Launceston, Tasmania. Completed 1895. The first publicly owned hydro-electric plant in the Southern Hemisphere. Supplied power to the city of Launceston for street lighting.
- Decew Falls 1, St. Catharines, Ontario, Canada completed 25 August 1898. Owned by Ontario Power Generation. Four units are still operational. Recognized as an IEEE Milestone in Electrical Engineering & Computing by the IEEE Executive Committee in 2002.
- It is believed that the oldest Hydro Power site in the United States is located on Claverack Creek, in Stottville, New York. The turbine, a Morgan Smith, was constructed in 1869 and installed 2 years later. It is one of the earliest water wheel installations in the United States and also generated electricity. It is owned today by Edison Hydro [citation needed].
Largest hydro-electric power stations
The La Grande Complex in Quebec, Canada, is the world's largest hydroelectric generating system. The eight generating stations of the complex have a total generating capacity of 16,021 MW. The Robert Bourassa station alone has a capacity of 5,616 MW. A ninth station (Eastmain-1) is currently under construction and will add 480 MW to the total. Construction on an additional project on the Rupert River was started on January 11, 2007. It will add two stations with a combined capacity of 888 MW.
| Name | Country | Year of completion | Total Capacity | Max annual electricity production |
| Itaipú | Brazil/Paraguay | 1984/1991/2003 | 14,000 MW | 93.4 TW-hours |
| Guri | Venezuela | 1986 | 10,200 MW | 46 TW-hours |
| Three Gorges Dam | China | 2004* | 9,800 MW(2006)22,400 MW(when complete) | 84,7 TW-hours |
| Grand Coulee | United States | 1942/1980 | 6,809 MW | 22.6 TW-hours |
| Sayano Shushenskaya | Russia | 1983 | 6,721 MW | 23.6 TW-hours |
| Krasnoyarskaya | Russia | 1972 | 6,000 MW | 20.4 TW-hours |
| Robert-Bourassa | Canada | 1981 | 5,616 MW | |
| Churchill Falls | Canada | 1971 | 5,429 MW | 35 TW-hours |
| Bratskaya | Russia | 1967 | 4,500 MW | 22.6 TW-hours |
| Ust Ilimskaya | Russia | 1980 | 4,320 MW | 21.7 TW-hours |
| Yaciretá | Argentina/Paraguay | 1998 | 4,050 MW | 19.1 TW-hours |
| Ertan Dam | China | 1999 | 3,300 MW(550MW×6) | 17.0 TW-hours |
| Gezhouba Dam | China | 1988 | 3,115 MW | 17.01 TW-hours |
| Nurek Dam | Tajikistan | 1979/1988 | 3,000 MW | |
| La Grande-4 | Canada | 1986 | 2,779 MW | |
| W. A. C. Bennett Dam | Canada | 1968 | 2,730 MW | |
| Volzhskaya (Volgogradskaya) | Russia | 1961 | 2,541 MW | 12.3 TW-hours |
| La Grande-3 | Canada | 1984 | 2,418 MW | |
| Atatürk Dam | Turkey | 1990 | 2,400 MW | |
| Zhiguliovskaya (Samarskaya) | Russia | 1957 | 2,300 MW | 10.5 TW-hours |
| Iron Gates | Romania/Serbia | 1970 | 2,280 MW | 11.3 TW-hours |
| La Grande-2-A | Canada | 1992 | 2,106 MW | |
| Aswan | Egypt | 1970 | 2,100 MW | |
| Tarbela Dam | Pakistan | 1976 | 2,100 MW | |
| Hoover Dam | United States | 1936/1961 | 2,080 MW | |
| Cahora Bassa | Mozambique | 1975 | 2,075 MW | |
| Karun III Dam | Iran | 2007 | 2,000 MW | 4,1 TW-hours |
* Powered first 14 water turbogenerators
These are ranked by maximum power.
In progress
| Name | Capacity | Country | Construction started | Scheduled completion | Comments
|
|---|---|---|---|---|---|
| Three Gorges Dam | 22,400 MW | China | December 141994 | 2009 | Largest Power Plant of the world. First power in July 2003, with 9,800MW installed until 2006. |
| Xiluodu Dam | 12,600 MW | China | December 26 2005 | 2015 | |
| Baihetan Dam | 12,000 MW | China | 2009 | 2015 | Still in planning |
| Wudongde Dam | 7,000 MW | China | 2009 | 2015 | Still in planning |
| Longtan Dam | 6,300 MW | China | July 1 2001 | December 2009 | |
| Xiangjiaba Dam | 6,000 MW | China | November 26 2006 | 2009 | |
| Jinping 2 Hydropower Station | 4,800 MW | China | January 302007 | 2014 | To build this dam, only 23 families and 129 local residents need to be moved. It works with Jinping 1 Hydropower Station as a group. |
| Laxiwa Dam | 4,200 MW | China | April 18 2006 | 2010 | |
| Xiaowan Dam | 4,200 MW | China | January 1 2002 | December 2012 | |
| Jinping 1 Hydropower Station | 3,600 MW | China | November 11 2005 | 2014 |
|
| Pubugou Dam | 3,300 MW | China | March 30 2004 | 2010 | |
| Goupitan Dam | 3,000 MW | China | November 8 2003 | 2011 | |
| Ilısu Dam | 1,200MW | Turkey | August 5, 2006 | 2013 | one of the Southeastern Anatolia Project Dams in Turkey |
Those 10 dams in China will have total generating capacity of 70,400MW (70.2 GW) when completed. For comparison purposes, in 1999 the total capacity of hydroelectric generators in Brazil, the third country by hydroelectric capacity, was 57.52GW.
Countries with the most hydro-electric capacity
Country, total annual hydroelectricity production, total capacity installed（most recent data） [2]
- People's Republic of China, 416,700 GWh (128,570 MW installed)[3]
- Canada, 356,930 GWh (68,974 MW installed)
- Brazil, 336,80 GWh (69,080 MW installed)
- USA, 289,980 GWh (79,511 MW installed)
- Russia, 167,000 GWh (45,000 MW installed)
- India, 125,126 GWh (33,600 MW installed)
- Norway, 119,000 GWh (27,528 MW installed)
- Japan, 88,500 GWh (27,229 MW installed)
- France, 56,100 GWh (25,335 MW installed)
These are 2006 figures and include pumped-storage hydroelectricity schemes. GWh means giga-watt-hour, which equal to 1 million kWh (kilo-watt-hour) equal to 3.6×10^12 Joule, equal to 123.0 tons(1000 kilogram) of standard coal, equal to 86 ton of standard oil.
References
- New Scientist report on greenhouse gas production by hydroelectric dams.
- International Water Power and Dam Construction Venezuela country profile
- International Water Power and Dam Construction Canada country profile
- Tremblay, Varfalvy, Roehm and Garneau. 2005. Greenhouse Gas Emissions - Fluxes and Processes, Springer, 732 p.
See also
- Hydropower
- List of energy topics
- Wave power
- Tidal power
- List of reservoirs and dams
- Tennessee Valley Authority
- Small hydro
- Pumped-storage hydroelectricity
- Environmental concerns with electricity generation
- William George Armstrong, 1st Baron Armstrong an early private hydro-electric station
External links
- National Hydropower Association, USA
- Center of expertise on hydropower impacts on fish and fish habitat
- World Commission on Dams report on environmental and social effects of large dams, including discussion of greenhouse gas emissions
- Edith Irvine Collection of photographs which includes the Electra Power Project, the first hydroelectric project in California located at Mokelumne Hill, California
- Hydro Quebec
- CBC Digital Archives – Hydroelectricity: The Power of Water
- University of Washington Libraries Digital Collections – Seattle Power and Water Supply Collection Historical photographs and pamphlets documenting the construction of hydroelectric power and water supply facilities built in Washington State from the late 1890s to the 1950s including the Snoqualmie Falls Power Plant, the Electron Plant, the Skagit River Hydroelectric Project, and the Cedar River water supply system.
- The Federal Energy Regulatory Commission (FERC) Federal Agency that regulates more than 1500 hydropower dams in the United States.
- European Small Hydropower Association, Guide to Developing Small Hydropower (Part 1), Part 2
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