"Усны эрчим хүч"-ны өөр хувилбарууд

== Ерөнхий аргачлал ==
[[File:Sala de turbinas.jpg|thumb|300px|Turbine row at Los Nihuiles Power Station in [[Mendoza, Argentina|Mendoza]], Argentina]]
[[Image:Hydroelectric dam.svg|thumb|300px|Cross section of a conventional hydroelectric dam.]]
[[Image:Water turbine.svg|thumb|A typical [[Water turbine|turbine]] and [[electrical generator|generator]]]]
===Conventional (dams)===
{{See also|List of conventional hydroelectric power stations}}
Most hydroelectric power comes from the [[potential energy]] of [[dam]]med water driving a [[water turbine]] and [[electric generator|generator]]. The power 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 (hydraulic)|head]]. The amount of [[potential energy]] in water is proportional to the head. A large pipe (the "[[penstock]]") delivers water to the turbine.<ref>[http://www.electricityforum.com/hydroelectricity.html Hydro Electricity Explained]</ref>
{{Main|Pumped-storage hydroelectricity}}
{{See also|List of pumped-storage hydroelectric power stations}}
This method produces electricity to supply high peak demands by moving water between [[reservoir (water)|reservoirs]] at different elevations. At times of low electrical demand, the excess generation capacity is used to pump water into the higher reservoir. When the demand becomes greater, water is released back into the lower reservoir through a turbine. Pumped-storage schemes currently provide the most commercially important means of large-scale [[grid energy storage]] and improve the daily [[capacity factor]] of the generation system. Pumped storage is not an energy source, and appears as a negative number in listings.<ref>[http://thesouthslope.com/content/pumped-storage-explained Pumped Storage, Explained]</ref>
===Run of the river===
{{Main|Run of the river hydroelectricity}}
{{See also|List of run-of-the-river hydroelectric power stations}}
Run of the river hydroelectric stations are those with small or no reservoir capacity, so that the water coming from upstream must be used for generation at that moment, or must be allowed to bypass the dam. In the United States, run of the river hydropower could potentially provide 60,000 MW (about 13.7% of total use in 2011 if continuously available).<!--total use in 2011 was 3841 billion kWh from Annual Energy Outlook http://www.eia.gov/forecasts/aeo/er/ --><ref>[http://www.renewableenergyworld.com/rea/news/article/2012/01/run-of-the-river-hydropower-goes-with-the-flow Run-of-the-River Hydropower Goes With the Flow]</ref>
{{Main|Tide power}}
{{See also|List of tidal power stations}}
A [[tidal power]] station makes use of the daily rise and fall of ocean water due to tides; such sources are highly predictable, and if conditions permit construction of reservoirs, can also be [[Dispatchable generation|dispatchable]] to generate power during high demand periods. Less common types of hydro schemes use water's [[kinetic energy]] or undammed sources such as undershot [[water wheel|waterwheels]]. Tidal power is viable in a relatively small number of locations around the world. In Great Britain, there are eight sites that could be developed, which
have the potential to generate 20% of the electricity used in 2012.<ref>[http://www.darvill.clara.net/altenerg/tidal.htm Energy Resources: Tidal power]</ref>
==Sizes, types and capacities of hydroelectric facilities==
=== Large facilities ===
{{See also|List of largest power stations in the world|List of largest hydroelectric power stations}}
Large-scale hydroelectric power stations are more commonly seen as the largest power producing facilities in the world, with some hydroelectric facilities capable of generating more than double the installed capacities of the current [[List of nuclear power stations|largest nuclear power stations]].
Although no official definition exists for the capacity range of large hydroelectric power stations, facilities from over a few hundred [[megawatt]]s are generally considered large hydroelectric facilities.
Currently, only four facilities over {{nowrap|10 [[Gigawatt|GW]]}} ({{nowrap|10,000 [[Megawatt|MW]]}}) are in operation worldwide, see table below.<ref name=wi2012>{{cite web |url=http://www.worldwatch.org/node/9527 |title=Use and Capacity of Global Hydropower Increases |author=Worldwatch Institute |date=January 2012 |work= }}</ref>
! Rank !! width=150 | Station !! width=150 | Country !! [[Geographic coordinate system|Location]] !! Capacity ([[Megawatt|MW]])
| align=center | 1. || [[Three Gorges Dam]] || {{flag|China}} || {{Coord|30|49|15|N|111|00|08|E|name=Three Gorges Dam}} || align=center | 22,500
| align=center | 2. || [[Itaipu Dam]] || {{flag|Brazil}}<br />{{flag|Paraguay}} || {{Coord|25|24|31|S|54|35|21|W|name=Itaipu Dam}} || align=center | 14,000
| align=center | 3. ||[[Xiluodu Dam]] || {{flag|China}} || {{Coord|28|15|35|N|103|38|58|E|name=Xiluodu Dam}} || align=center | 13,860
| align=center | 4. || [[Guri Dam]] || {{flag|Venezuela}} || {{Coord|07|45|59|N|62|59|57|W|name=Guri Dam}} || align=center | 10,200
{{wide image|Itaipu Décembre 2007 - Vue Générale.jpg|1500px|Panoramic view of the Itaipu Dam, with the spillways (closed at the time of the photo) on the left. In 1994, the [[American Society of Civil Engineers]] elected the Itaipu Dam as one of the seven modern [[Wonders of the World]].<ref>{{Citation
| last = Pope
| first = Gregory T.
| title = The seven wonders of the modern world
| newspaper = Popular Mechanics
| pages = 48–56
| date = December 1995
| url = http://books.google.ca/books?id=O2YEAAAAMBAJ&lpg=PA50&dq=itaipu&as_brr=1&pg=PA50#v=onepage&q&f=false}}</ref>
{{Main|Small hydro}}
Small hydro is the development of [[hydroelectric power]] on a scale serving a small community or industrial plant. The definition of a small hydro project varies but a generating capacity of up to 10 [[megawatt]]s (MW) is generally accepted as the upper limit of what can be termed small hydro. This may be stretched to 25 MW and 30 MW in [[Canada]] and the [[United States]]. Small-scale hydroelectricity production grew by 28% during 2008 from 2005, raising the total world small-hydro capacity to {{nowrap|85 [[Gigawatt|GW]]}}. Over 70% of this was in [[China]] ({{nowrap|65 GW}}), followed by [[Japan]] ({{nowrap|3.5 GW}}), the [[United States]] ({{nowrap|3 GW}}), and [[India]] ({{nowrap|2 GW}}).<ref>[http://www.ren21.net/globalstatusreport/download/RE_GSR_2006_Update.pdf Renewables Global Status Report 2006 Update], ''[[REN21]]'', published 2006</ref>
[[File:Nw vietnam hydro.jpg|thumb|300px|A micro-hydro facility in [[Vietnam]]]]
[[File:Amateur Hydroelectricity.jpg|thumb|300px|Pico hydroelectricity in [[Mondulkiri]], [[Cambodia]]]]
Small hydro stations may be connected to conventional electrical distribution networks as a source of low-cost renewable energy. Alternatively, small hydro projects may be built in isolated areas that would be uneconomic to serve from a network, or in areas where there is no national electrical distribution network. Since small hydro projects usually have minimal reservoirs and civil construction work, they are seen as having a relatively low environmental impact compared to large hydro. This decreased environmental impact depends strongly on the balance between stream flow and power production.
{{Main|Micro hydro}}
Micro hydro is a term used for [[hydroelectric power]] installations that typically produce up to {{nowrap|100 [[Kilowatt|kW]]}} of power. These installations can provide power to an isolated home or small community, or are sometimes connected to electric power networks. There are many of these installations around the world, particularly in developing nations as they can provide an economical source of energy without purchase of fuel.<ref>{{cite web|url=http://www.tve.org/ho/doc.cfm?aid=1636&lang=English |title=Micro Hydro in the fight against poverty |publisher=Tve.org |date= |accessdate=2012-07-22}}</ref> Micro hydro systems complement [[photovoltaics|photovoltaic]] solar energy systems because in many areas, water flow, and thus available hydro power, is highest in the winter when solar energy is at a minimum.
{{Main|Pico hydro}}
Pico hydro is a term used for [[hydroelectric power]] generation of under {{nowrap|5 [[Kilowatt|kW]]}}. It is useful in small, remote communities that require only a small amount of electricity. For example, to power one or two fluorescent light bulbs and a TV or radio for a few homes.<ref>{{cite web|url=http://www.t4cd.org/Resources/ICT_Resources/Projects/Pages/ICTProject_287.aspx|title=Pico Hydro Power|publisher=T4cd.org|accessdate=2010-07-16}}</ref> Even smaller turbines of 200-300W may power a single home in a developing country with a drop of only {{Convert|1|m|ft|0|abbr=on}}. A Pico-hydro setup is typically [[#Run-of-the-river|run-of-the-river]], meaning that dams are not used, but rather pipes divert some of the flow, drop this down a gradient, and through the turbine before returning it to the stream.
{{Main|Underground power station}}
An [[underground power station]] is generally used at large facilities and makes use of a large natural height difference between two waterways, such as a waterfall or mountain lake. An underground tunnel is constructed to take water from the high reservoir to the generating hall built in an underground cavern near the lowest point of the water tunnel and a horizontal tailrace taking water away to the lower outlet waterway.[[Image:Tailrace-Forebay-Limestone.JPG|thumb|Measurement of the tailrace and forebay rates at the [[Limestone Generating Station]] in [[Manitoba]], [[Canada]].]]
== Эрчим хүчний тооцоо ==