Editing Dam (section)

=== Power generation plant ===
{{main|Hydroelectricity}}

[[File:Hydroelectric dam.svg|thumb|left|Hydroelectric dam in cross section]]
[[File:Water turbine - edit1.svg|thumb|upright|[[Water turbine|Hydraulic turbine]] and [[electric generator]]]]

{{As of|2005}}, hydroelectric power, mostly from dams, supplies some 19% of the world's electricity, and over 63% of [[renewable energy]].<ref name="REN21-2006">[http://www.ren21.net/globalstatusreport/download/RE_GSR_2006_Update.pdf Renewables Global Status Report 2006 Update]  {{webarchive|url=https://web.archive.org/web/20110718181410/http://www.ren21.net/globalstatusreport/download/RE_GSR_2006_Update.pdf |date=18 July 2011 }}  {{cite web|url=http://www.ren21.net/Portals/0/documents/activities/gsr/RE_GSR_2006_Update.pdf |title=RENEWABLES GLOBAL STATUS REPORT 2006 Update |access-date=2015-11-09 |url-status=dead |archive-url=https://web.archive.org/web/20160514070611/http://www.ren21.net/Portals/0/documents/activities/gsr/RE_GSR_2006_Update.pdf |archive-date=14 May 2016 }}, ''[[REN21]]'', published 2006, accessed 16 May 2007</ref> Much of this is generated by large dams, although [[China]] uses small-scale hydro generation on a wide scale and is responsible for about 50% of world use of this type of power.<ref name="REN21-2006" />

Most hydroelectric power comes from the [[potential energy]] of dammed water driving a [[water turbine]] and [[electric generator|generator]]; to boost the power generation capabilities of a dam, the water may be run through a large pipe called a [[penstock]] before the [[turbine]]. A variant on this simple model uses [[pumped-storage hydroelectricity]] to produce electricity to match periods of high and low demand, by moving water between [[reservoir]]s 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. (For example, see [[Dinorwig Power Station]].)