Hydroelectricity is the term referring to electricity generatedby hydropower; the production of electrical power throughthe use of the gravitational force of falling or flowing water. Itis the most widely used form of renewable energy,accounting for 16 percent of global electricity consumption,and 3,427 terawatt-hours of electricity production in 2010,which continues the rapid rate of increase experiencedbetween 2003 and 2009.
Hydropower is produced in 150countries, with the Asia-Pacificregion generating 32 percent ofglobal hydropower in 2010. Chinais the largest hydroelectricityproducer, with 721 terawatt-hoursof production in 2010,representing around 17 percent ofdomestic electricity use. There arenow three hydroelectricity plantslarger than 10 GW: the ThreeGorges Dam in China, ItaipuDam in Brazil, and Guri Dam inVenezuela
The cost of hydroelectricity is relatively low, making it acompetitive source of renewable electricity. The averagecost of electricity from a hydro plant larger than 10megawatts is 3 to 5 U.S. cents per kilowatt-hour. Hydro is also a flexible source of electricity sinceplants can be ramped up and down very quickly toadapt to changing energy demands. However, damminginterrupts the flow of rivers and can harm localecosystems, and building large dams and reservoirsoften involves displacing people and wildlife. Once ahydroelectric complex is constructed, the projectproduces no direct waste, and has a considerably loweroutput level of the greenhouse gas carbondioxide (CO2) than fossil fuel powered energy plants.
Hydropower has been used since ancient times to grindflour and perform other tasks. In the mid-1770s, Frenchengineer Bernard Forest deBélidor published Architecture Hydraulique whichdescribed vertical- and horizontal-axis hydraulicmachines. By the late 19th century, the electricalgenerator was developed and could now be coupled withhydraulics. The growing demand for the IndustrialRevolution would drive development as well. In 1878 theworlds first hydroelectric power scheme was developedat Cragside in Northumberland, England by WilliamGeorge Armstrong. It was used to power a single arclamp in his art gallery. The old Schoelkopf PowerStation No. 1 near Niagara Falls in the U.S. side began toproduce electricity in 1881. The first Edison hydroelectricpower plant, the Vulcan Street Plant, began operatingSeptember 30, 1882, in Appleton, Wisconsin, with anoutput of about 12.5 kilowatts. By 1886 there were 45hydroelectric power plants in the U.S. and Canada. By1889 there were 200 in the U.S. alone.
Hydropower or water power is power derived from the energy of falling water,which may be harnessed for useful purposes. Since ancient times, hydropower hasbeen used for irrigation and the operation of various mechanical devices, suchas watermills, sawmills, textile mills, dock cranes, and domestic lifts.Since the early 20th century, the term is used almost exclusively in conjunction withthe modern development of hydro-electric power, which allowed use of distantenergy sources. Another method used to transmit energy used a trompe, whichproduces compressed air from falling water. Compressed air could then be piped topower other machinery at a distance from the waterfall.Waters power is manifested in hydrology, by the forces of water on the riverbed andbanks of a river. When a river is in flood, it is at its most powerful, and moves thegreatest amount of sediment. This higher force results in the removal of sedimentand other material from the riverbed and banks of the river, locally causing erosion,transport and, with lower flow, sedimentation downstream.
Generating methodsConventional (dams)Most hydroelectric power comes from the potential energy of dammed water drivinga water turbine and generator. The power extracted from the water depends on thevolume and on the difference in height between the source and the waters outflow. Thisheight difference is called the head. The amount of potential energy in water isproportional to the head. A large pipe (the "penstock") delivers water to the turbine.Pumped-storageMain article: Pumped-storage hydroelectricityThis method produces electricity to supply high peak demands by moving waterbetween reservoirs at different elevations. At times of low electrical demand, excessgeneration capacity is used to pump water into the higher reservoir. When there is higherdemand, water is released back into the lower reservoir through a turbine. Pumped-storageschemes currently provide the most commercially important means of large-scale gridenergy storage and improve the daily capacity factor of the generation system
.Run-of-the-riverRun-of-the-river hydroelectric stations are those with small or no reservoir capacity, so thatthe water coming from upstream must be used for generation at that moment, or must beallowed to bypass the dam.TideA tidal power plant makes use of the daily rise and fall of ocean water due to tides; suchsources are highly predictable, and if conditions permit construction of reservoirs, can alsobe dispatchable to generate power during high demand periods. Less common types ofhydro schemes use waters kinetic energy or undammed sources such asundershotwaterwheels.UndergroundAn underground power station makes use of a large natural height difference between twowaterways, such as a waterfall or mountain lake. An underground tunnel is constructed totake water from the high reservoir to the generating hall built in an underground cavernnear the lowest point of the water tunnel and a horizontal tailrace taking water away to the
Hydropower typesHydropower is used primarily to generate electricity. Broad categories include: A conventional dammed-hydro facility (hydroelectric dam) is the most common type ofhydroelectric power generation.•Conventional hydroelectric, referring to hydroelectric dams.•Run-of-the-river hydroelectricity, which captures the kinetic energy in rivers orstreams, without the use of dams.•Small hydro projects are 10 megawatts or less and often have no artificialreservoirs.•Micro hydro projects provide a few kilowatts to a few hundred kilowatts to isolatedhomes, villages, or small industries.•Pumped-storage hydroelectricity stores water pumped during periods of lowdemand to be released for generation when demand is high.
Used as a source of generating power forhundreds of years, Hydropower is theharnessing of the force of moving water andproducing energy to be used in multipleapplications.Dating back to ancient times, hydropowerwas used for the operation of variousmachines, such as watermills, sawmills, dockcranes and also for irrigation purposes. Backin Roman times, water was the source ofenergy that powered mills to extract flourfrom grains and to cut timber and stone inthe construction of the city and itsdwellings.Along with the impact on ecosystems, alesser-known result from the construction ofhydroelectric plants is the dispersing of thelocal population. It is not often thoughtabout, but it has been estimated thatbetween 40 and 80 million peopleworldwide have been relocated due to theconstruction of dams and other hydropowerplants.
The first known hydropower plant built inthe U.S. occurred in 1880, in Grand Rapids,Michigan. The so-called “boom” in largerscale plants did not take place until the 1930sand into the 1940s as part of PresidentRoosevelts "New Deal" program.In the modern world, the use of hydropoweris the catalyst in producing hydroelectricity.In its practice, hydroelectricity allows an enduser the use of the energy produced by thewater source in a lower, more cost effectivemanner.Hydroelectricity is produced fromhydropower, which is the generation ofenergy through the use of gravitational forcesfrom flowing or falling water, usually fromdams or rivers. Throughout the world,hydroelectric power supplies nearly 19% ofelectricity, or 715,000 MWe (megawattelectrical). It also represents more than 63%of the electricity used from renewablesources
.The greatest benefit from the use of hydropower is that it produces no carbon dioxideemissions or other harmful discharges, such as sulfur dioxide, carbon monoxide, andnitric acid, unlike the use of fossil fuels. Hydropower also generates no waste by-products and has no affect on today’s growing concerns with global warming.One of the most widely used devises for the production of hydropower is the dam.Currently there are more than 75,000 dams in the U.S. blocking more than 600,000miles of our nation’s rivers, or 17% of the free flowing water.
With the use of dammed water, thepotential energy source is used to drivewater turbines and generators. The keyelement to the production of hydropower isdependent on the volume of the water, andthe height difference between the originalsource of the water, the dammed water, andthe position of the outflow. This differencein the height is paramount to produce theoptimal amount of energy from the flowingwater.Within the United States, the Grand Coulee Dam, on the Columbia River inWashington State, currently holds the title as the country’s largest electric powerproducing facility, and is the fifth largest producer in the world. The dam also holdsthe distinction of being the largest concrete structure in North America as well,surpassing the Hoover Dam when constructed in 1942.Rounding out the top five dams in the world, the Grand Coulee is surpassed by only theThree Gorges Dam in China, the Guri Dam in Venezuela, the Itaipu Dam on the borderof Paraguay and Brazil, and the Sayano-Shushenskaya Dam in Russia.In addition to the more common practices of waterpower, several other forms are in useor in developmental stages as well. Included are damless hydropower, which harnessesthe kinetic energy of rivers, streams and oceans, and wave power, which captures theenergy produced by waves.
One of the up-and-coming developments is from the use of tidal stream power. Still in itsinfancy, this technology draws energy from the currents of high volume river and streams.Requiring much more research, early models have shown some promise.Despite the numerous advantages that hydropower possesses, there certainly are concernsthat are raised by the construction and usage of hydroelectric plants. The most common,negative perception of these plants is the affects surrounding environmental damage,namely the disruption of the local ecosystems.
Hydropowers effect on the environmentHydropower is a clean source of energy. There are no problems with air pollution, chemicalrunoff, toxic waste or the like.Hydropower plants also create recreation areas and animal habitat. Because of the change inwater location, wide areas after the dam become great for water edge species ofanimals. And the large reservoir is good for many types of large fish. Boating areas arecreated in the reservoir too, as well as bird watching sites downstream of the dam.Some problems may still occur though., but through careful planning these can beeliminated almost completely. Temporary disruption in the ecology to build the dam, but afterwards this cleared land can be used to make animal habitat. downstream of the dam, water flow may be significantly reduced, but careful monitoring of the land downstream of the dam can give operators enough information to allow more water to pass through the dam. Catadramous fish (fish that live in salt water and spawn in fresh water) migration may be interupted- but fish ladders and fish elevators may be installed to eliminate this problem. Anadromous (fish that live in fresh water and spawn in salt water) fish do not have this problem, because they can go right through the turbines which only spin at 81.8 rpms. Flooding of land upstream of the dam can be a problem, but careful monitoring of the land upstream of the dam can give operators enough information to allow more water to run through the dam to compensate for this problem.
Advantages of hydropower It is a clean and safe source of energy They are self sustaining They create habitat for more types of fish They can act as a flood controller They are the most efficient energy source running from 90-95% efficiency Other forms of Hydropower Tidal power: electricity generated by turbines moved by the tides. This is still in experimental stages. Ocean thermal power: power generated by the thermal expansion of the ocean. This can only be used in a location like the Gulf stream. Geothermal power: natural steam is used underground to turn turbines. This is limited to location which have these phenomenon.