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'Hydroelectricity' is electricity produced by 'hydropower'. Hydroelectricity now supplies about 715,000 MWe or 19% of world electricity (16% in 2003). It is also the world's leading form of renewable energy, accounting for over 63% of the total in 2005.^[1]
Although large hydroelectric installations generate most of the world's hydroelectricity, small hydro schemes are particularly popular in China, which has over 50% of world small hydro capacity.¹

Contents

Electricity generation

Formula

Industrial hydroelectric plants

Advantages

Economics

Related activities

Greenhouse gas emissions

Disadvantages

Environmental damage

Greenhouse gas emissions

Population relocation

Dam failures

Comparison with other methods of power generation

Oldest hydro-electric power stations:

Countries with the most hydro-electric capacity

Largest hydroelectric power stations

Major schemes in progress

See also

External links

References

Electricity generation

Main articles: Electricity generation

Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. In this case the energy extracted from the water depends on the volume and 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.
Pumped storage hydroelectricity produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, excess generation capacity is used to pump water into the higher reservoir. When there is higher demand, water is released back into the lower reservoir through a turbine. Pumped storage schemes currently provide the only commercially important means of grid energy storage and improve the daily load factor of the generation system.
Less common types of hydro schemes use water's kinetic energy or undammed sources such as run-of-the-river, waterwheels, and tidal power.

Formula

This is a simple formula for approximating electricity production at a hydroelectric plant:
'''P=hrk,'''

where P is power in watts, h is height in meters, r is flow rate in cubic meters per second, and k is a constant of 7,500 watts (assuming an efficiency factor of about 75 percent).

Industrial hydroelectric plants

While many hydroelectric projects supply public electricity networks, some are created to serve specific industrial enterprises. Dedicated hydroelectric projects are often built to provide the substantial amounts of electricity needed for aluminium electrolytic plants, for example. In the Scottish Highlands there are examples at Kinlochleven and Lochaber, constructed during the early years of the 20th century. In Suriname, the Brokopondo Reservoir was constructed to provide electricity for the Alcoa aluminium industry. As of 2007 the Kárahnjúkar Hydropower Project in Iceland remains controversial.^[2]

Advantages

Economics

The major advantage of hydroelectricity is elimination of the cost of fuel. The cost of operating a hydroelectric plants is nearly immune to increases in the cost of fossil fuels such as oil, natural gas or coal. Hydroelectric plants tend to have longer economic 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.
Where a dam serves multiple purposes, a hydroelectric plant may be added with relatively low construction cost, providing a useful revenue stream to offset the costs of dam operation. It has been calculated that the sale of electricity from the Three Gorges Dam will cover the construction costs after 5 to 7 years of full generation.^[3]

Related activities

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 common. Multi-use dams installed for irrigation can support the fish farm with relatively constant water supply. Large hydro dams can control floods, which would otherwise affect people living downstream of the project. When dams create large reservoirs and eliminate rapids, boats may be used to improve transportation.

Greenhouse gas emissions

Since no fossil fuel is consumed, emission of carbon dioxide (a greenhouse gas) from burning fuel is eliminated. While some carbon dioxide is produced during manufacture and construction of the project, this is a tiny fraction of the operating emissions of equivalent fossil-fuel electricity generation. However, there may be other sources of emissions as discussed below.

Disadvantages

Environmental damage

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 spawn are also harmed on their migration to sea when they must pass through turbines. This has led to some areas transporting smolt downstream by barge during parts of the year. Turbine and power-plant designs that are easier on aquatic life are an active area of research.
Generation of hydroelectric power changes 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. 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.
Large-scale hydroelectric dams, such as the Aswan Dam and the Three Gorges Dam, have created environmental problems both upstream and downstream.
A further concern is the impact of major schemes on birds. 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.

Greenhouse gas emissions

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.^[5]
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. A new class of underwater logging operation that targets drowned forests can mitigate the effect of forest decay.^[6]

Population relocation

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.

Dam failures

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. Dams may be subject to enemy bombardment during wartime, sabotage and terrorism. Smaller dams and micro hydro facilities are less vulnerable to these threats.
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.

Comparison with other methods of power generation

Hydroelectricity eliminates the flue gas emissions from fossil fuel combustion, including pollutants such as sulfur dioxide, nitric oxide, carbon monoxide, dust, and mercury in the coal.
Compared to the nuclear power plant, hydroelectricity generates no nuclear waste, nor nuclear leaks. Unlike uranium, hydroelectricity is also a renewable energy source.
Compared to wind farms, hydroelectricity power plants have a more predictable load factor. If the project has a storage reservoir, it can be dispatched to generate power when needed. Hydroelectric plants can be easily regulated to follow variations in power demand.
Unlike fossil-fueled combustion turbines, construction of a hydroelectric plant requires a long lead-time for site studies, hydrological studies, and environmental impact assessment. Hydrological data up to 50 years or more is usually required to determine the best sites and operating regimes for a large hydroelectric plant. Unlike plants operated by fuel, such as fossil or nuclear energy, the number of sites that can be economically developed for hydroelectric production is limited; in many areas the most cost effective sites have already been exploited. New hydro sites tend to be far from population centers and require extensive transmission lines. Hydroelectric generation depends on rainfall in the watershed, and may be significantly reduced in years of low rainfall or snowmelt. Utilities that primarily use hydroelectric power may spend additional capital to build extra capacity to ensure sufficient power is available in low water years.



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.

Oldest hydro-electric power stations:

★ Cragside, Rothbury, England completed 1870.

★ 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.

★ Niagara Falls, New York. For many years the largest hydroelectric power station in the world. Operation began locally in 1895 and power was transmitted to Buffalo, New York, in 1896.

★ 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.

★ The oldest continuously-operated commercial hydroelectric plant in the United States is built on the Hudson River at Mechanicville, New York. The seven 750 kW units at this station initially supplied power at a frequency of 38 Hz, but later were increased in speed to 40 Hz. It went into commercial service July 22,1898. It is now being restored to its original condition and remains in commercial operation. ^[7]

Countries with the most hydro-electric capacity

The ranking of hydro-electric capacity is either by actual annual energy production or by installed capacity power rating. A hydro-electric plant rarely operates at its full power rating over a full year; the ratio between annual average power and installed capacity rating is the load factor. The installed capacity is the sum of all generator nameplate power ratings. Sources came from ''BP Annual Report 2006''

Country	Annual Hydroelectric Energy Production(TWh)	Installed Capacity (GW)	Load Factor
People's Republic of China [8]	416.7	128.57	0.37
Canada	350.3	68.974	0.59
Brazil	349.9	69.080	0.56
USA	291.2	79.511	0.42
Russia	157.1	45.000	0.42
Norway	119.8	27.528	0.49
India	112.4	33.600	0.43
Japan	95.0	27.229	0.37
France	61.5	25.335	0.25

Country, annual hydroelectricity production, installed capacity (2006 data including pumped storage schemes)^[9]

Largest hydroelectric 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 (MW)	Max annual electricity production (TW-hour)
Itaipú	Brazil/Paraguay	1984/1991/2003	14,000	93.4
Three Gorges Dam	China	2004 ★	11,900 (August 2007); 22,500 (when complete)	84.7
Guri	Venezuela	1986	10,200	46
Grand Coulee	United States	1942/1980	6,809	22.6
Sayano Shushenskaya	Russia	1983	6,721	23.6
Krasnoyarskaya	Russia	1972	6,000	20.4
Robert-Bourassa	Canada	1981	5,616
Churchill Falls	Canada	1971	5,429	35
Bratskaya	Russia	1967	4,500	22.6
Ust Ilimskaya	Russia	1980	4,320	21.7
Tucurui	Brazil	1984	4,240
Yaciretá	Argentina/Paraguay	1998	4,050	19.2
Ertan Dam	China	1999	3,300 (550×6)	17.0
Gezhouba Dam	China	1988	3,115	17.01
Nurek Dam	Tajikistan	1979/1988	3,000
La Grande-4	Canada	1986	2,779
W. A. C. Bennett Dam	Canada	1968	2,730
Chief Joseph Dam	United States	1958/73/79	2,620
Volzhskaya (Volgogradskaya)	Russia	1961	2,541	12.3
La Grande-3	Canada	1984	2,418
Atatürk Dam	Turkey	1990	2,400
Zhiguliovskaya (Samarskaya)	Russia	1957	2,300	10.5
Iron Gates	Romania/Serbia	1970	2,280	11.3
John Day Dam	United States	1971	2,160
La Grande-2-A	Canada	1992	2,106
Aswan	Egypt	1970	2,100
Tarbela Dam	Pakistan	1976	2,100
Hoover Dam	United States	1936/1961	2,080
Cahora Bassa	Mozambique	1975	2,075
Karun III Dam	Iran	2007	2,000	4.1

★ Powered first 14 water turbogenerators

Major schemes in progress

Name	Maximum Capacity	Country	Construction started	Scheduled completion	Comments
Three Gorges Dam	22,400 MW	China	December 14 1994	2009	Largest power plant in the world. First power in July 2003, with 10,500 MW installed by June 2007.
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 30 2007	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
Jirau Dam	3,300 MW	Brazil	2007	2012
Pubugou Dam	3,300 MW	China	March 30 2004	2010
Santo Antônio Dam	3,150 MW	Brazil	2007	2012
Goupitan Dam	3,000 MW	China	November 8 2003	2011
Boguchan Dam	3,000 MW	Russia	1980	2012
Guandi Dam	2,400 MW	China	2007	2012
Son la Dam	2,400 MW	Vietnam	2005
Bureya Dam	2,010 MW	Russia	1978	2009
subansiri lower	2000 MW	India	2005	2009

Those 12 dams in China will have a total generating capacity of 89,400 MW (89.4 GW) when completed. For comparison purposes, in 2006 the total capacity of hydroelectric generators in Brazil, the third country by hydroelectric capacity, was 69.08GW.

See also

★ Hydropower

★ Wave power

★ Tidal power

★ List of reservoirs and dams

★ Small hydro

★ Pumped-storage hydroelectricity

★ Environmental concerns with electricity generation

★

★

External links

★ National Hydropower Association, USA

★ Center of expertise on hydropower impacts on fish and fish habitat, Canada

★ Hydro Quebec

★ CBC Digital Archives – Hydroelectricity: The Power of Water

★ University of Washington Libraries – Seattle Power and Water Supply Collection

★ United States Federal Energy Regulatory Commission (FERC)

★ European Small Hydropower Association

★ Power at Niagara Falls Niagara Falls Public Library (Ont.)

References

1. Renewables Global Status Report 2006 Update, ''REN21'', published 2007, accessed 2007-05-16
2. Summer of International dissent against Heavy Industry, ''Saving Iceland'', published 2007, accessed 2007-05-17
3. [1]
4. Stay Clear, Stay Safe, ''Ontario Power Generation''
5. [2]
6. http://inhabitat.com/2006/12/01/rediscovered-wood-the-triton-sawfish/#more-1973
7. ''The Historic Mechanicville Hydroelectric Station Part 1: The Early Days'', IEEE Industry Applications Magazine, Jan/Feb. 2007
8. [3]
9. Consumption TWh'!A1

Other 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.