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[[Image:Windenergy.jpg|thumb|This three-bladed [[wind turbine]] is the most common modern design because it minimizes forces related to fatigue.]]
'''Wind power''' is the conversion of wind energy into a useful form, such as electricity, using [[wind turbine]]s. At the end of 2007, worldwide capacity of wind-powered generators was 94.1 [[gigawatt]]s.<ref name="gwec">[http://www.gwec.net/index.php?id=28 Global Wind Energy Council News]</ref> Although wind produces about 1% of world-wide electricity use,<ref>[http://www.wwindea.org/home/images/stories/pr_statistics2007_210208_red.pdf World Wind Energy Association press release] retrieved 2008 03 18</ref> it accounts for approximately 19% of electricity production in [[Wind power in Denmark|Denmark]], 9% in [[Wind power in Spain|Spain]] and [[Wind power in Portugal|Portugal]], and 6% in [[Wind power in Germany|Germany]] and the [[Wind power in Ireland|Republic of Ireland]] (2007 data). Globally, wind power generation increased more than fivefold between 2000 and 2007.<ref name="gwec" />

Most wind power is generated in the form of electricity. Large scale [[wind farms]] are connected to electrical grids. Individual turbines can provide electricity to isolated locations. In [[windmill]]s, wind energy is used directly as mechanical energy for pumping water or grinding grain.

Wind energy is plentiful, [[renewable energy|renewable]], widely distributed, clean, and reduces [[greenhouse gas emissions]] when it displaces fossil-fuel-derived electricity. Therefore, it is considered by experts to be more environmentally friendly than many other energy sources. The [[Intermittent power sources|intermittency]] of wind seldom creates problems when using wind power to supply a low proportion of total demand. Where wind is to be used for a moderate fraction of demand, additional costs for compensation of intermittency are considered to be modest.<ref>{{cite web
| url= http://www.ieawind.org/AnnexXXV/Meetings/Oklahoma/IEA%20SysOp%20GWPC2006%20paper_final.pdf
| title= "Design and Operation of Power Systems with Large Amounts of Wind Power", IEA Wind Summary Paper
| author= Hannele Holttinen, ''et al.''
| date= September 2006 |format= [[PDF]] |work= |publisher= Global Wind Power Conference September 18-21, 2006, Adelaide, Australia
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= }} </ref>
{{renewable energy sources}}

==History==
{{main|History of wind power}}

[[Sailboats]] and [[sailing ship]]s have been using wind power for at least 5,500 years, and architects have used wind-driven [[natural ventilation]] in buildings since similarly ancient times. The use of wind to provide mechanical power came somewhat later in antiquity.

The earliest historical reference to a rudimentary windmill was used to power an [[Organ (music)|organ]] in the 1st century AD.<ref>A.G. Drachmann, "Heron's Windmill", ''Centaurus'', 7 (1961), pp. 145-151</ref> The first practical [[windmill]]s were later built in [[Sistan]], [[Afghanistan]], from the 7th century. These were vertical-[[axle]] windmills, which had long vertical [[driveshaft]]s with rectangle shaped [[blade]]s.<ref>[[Ahmad Y Hassan]], [[Donald Routledge Hill]] (1986). ''Islamic Technology: An illustrated history'', p. 54. [[Cambridge University Press]]. ISBN 0-521-42239-6.</ref> Made of six to twelve [[Windmill sail|sail]]s covered in [[reed mat]]ting or [[cloth]] material, these windmills were used to grind [[corn]] and draw up [[water]], and were used in the [[gristmill]]ing and [[Sugar refinery|sugarcane industries]].<ref>[[Donald Routledge Hill]], "Mechanical Engineering in the Medieval Near East", ''Scientific American'', May 1991, p. 64-69. ([[cf.]] [[Donald Routledge Hill]], [http://home.swipnet.se/islam/articles/HistoryofSciences.htm Mechanical Engineering])</ref> Horizontal-axle windmills were later used extensively in Northwestern [[Europe]] to grind flour beginning in the 1180s, and many Dutch windmills still exist.<ref>Dietrich Lohrmann, "Von der östlichen zur westlichen Windmühle", ''Archiv für Kulturgeschichte'', Vol. 77, Issue 1 (1995), pp.1-30 (18ff.)</ref>

In the [[United States]], the development of the "water-pumping windmill" was the major factor in allowing the farming and ranching of vast areas of North America, which were otherwise devoid of readily accessible water. They contributed to the expansion of [[rail transport]] systems throughout the world, by pumping water from [[water well|well]]s to supply the needs of the [[steam locomotive]]s of those early times.<ref>[http://www.mysanantonio.com/news/weather/weatherwise/stories/MYSA092407.01A.State_windmills.3430a27.html Quirky old-style contraptions make water from wind on the mesas of West Texas]</ref>

The multi-bladed wind turbine atop a lattice tower made of wood or steel was, for many years, a fixture of the landscape throughout rural America.

The modern wind turbine was developed beginning in the 1980s, although designs are still under development.

== Wind energy ==
{{details more|Wind}}

The origin of wind is complex. The Earth is unevenly heated by the sun resulting in the [[Geographic pole|pole]]s receiving less energy from the sun than the [[equator]] does. Also the dry land heats up (and cools down) more quickly than the seas do. The differential heating drives a global [[convection#Atmospheric convection|atmospheric convection]] system reaching from the Earth's surface to the [[stratosphere]] which acts as a virtual ceiling. Most of the energy stored in these wind movements can be found at high altitudes where continuous wind speeds of over 160 km/h (100 mph) occur. Eventually, the wind energy is converted through friction into diffuse heat throughout the Earth's surface and the atmosphere.

There is an estimated 72&nbsp;TW of wind energy on the Earth that potentially can be commercially viable.<ref> [http://www.ocean.udel.edu/windpower/ResourceMap/index-world.html Mapping the global wind power resource]. </ref> Not all the energy of the wind flowing past a given point can be recovered (see [[Betz' law]]).

=== Distribution of wind speed ===
{{Nofootnotes|section|date=August 2008}}
[[Image:Lee Ranch Wind Speed Frequency.png|thumb|left|Distribution of wind speed (red) and energy (blue) for all of 2002 at the Lee Ranch facility in Colorado. The histogram shows measured data, while the curve is the Rayleigh model distribution for the same average wind speed. Energy is the Betz limit through a 100&nbsp;meter diameter circle facing directly into the wind. Total energy for the year through that circle was 15.4&nbsp;[[gigawatt-hour]]s.]]

The strength of wind varies, and an average value for a given location does not alone indicate the amount of energy a wind turbine could produce there. To assess the frequency of wind speeds at a particular location, a probability distribution function is often fit to the observed data. Different locations will have different wind speed distributions. The [[Rayleigh distribution|Rayleigh]] model closely mirrors the actual distribution of hourly wind speeds at many locations.

Because so much power is generated by higher windspeed, much of the energy comes in short bursts. The 2002 Lee Ranch sample is telling; half of the energy available arrived in just 15% of the operating time. The consequence is that wind energy does not have as consistent an output as fuel-fired power plants; utilities that use wind power must provide backup generation for times that the wind is weak. Making wind power more consistent requires that [[Energy storage|storage technologies]] must be used to retain the large amount of power generated in the bursts for later use.

[[Image:WorldWindPower2008.png|thumb|Worldwide installed capacity 1997-2007, with projection 2008-2013 based on an exponential fit. Data source: [http://www.wwindea.org/ WWEA]]]

=== Grid management ===
Induction generators often used for wind power projects require [[reactive power]] for excitation, so substations used in wind-power collection systems include substantial [[capacitor]] banks for [[power factor correction]]. Different types of wind turbine generators behave differently during transmission grid disturbances, so extensive modelling of the dynamic electromechanical characteristics of a new wind farm is required by transmission system operators to ensure predictable stable behaviour during system faults. In particular, induction generators cannot support the system voltage during faults, unlike steam or hydro turbine-driven synchronous generators (however properly matched power factor correction capacitors along with electronic control of resonance can support induction generation without grid). [[Doubly-fed electric machine|Doubly-fed machines]], or wind turbines with solid-state converters between the turbine generator and the collector system, have generally more desirable properties for grid interconnection. Transmission systems operators will supply a wind farm developer with a ''grid code'' to specify the requirements for interconnection to the transmission grid. This will include [[power factor]], constancy of [[Utility frequency|frequency]] and dynamic behaviour of the wind farm turbines during a system fault. <ref> Robert Zavadil et al, ''Making Connections: Wind Generation Challenges and Progress'', ''IEEE Power and Energy Magazine'', Nov/Dec. 2005, pgs. 27-37</ref> <ref> Edgar A. DeMoe et al, ''Wind Plant Integration: Cost, Status and Issues'', 'IEEE Power and Energy Magazine'', Nov/Dec. 2005, pgs. 39-46</ref>

=== Capacity factor ===
Since wind speed is not constant, a [[wind farm]]'s annual energy production is never as much as the sum of the generator nameplate ratings multiplied by the total hours in a year. The ratio of actual productivity in a year to this theoretical maximum is called the [[capacity factor]]. Typical capacity factors are 20-40%, with values at the upper end of the range in particularly favourable sites.<ref> [http://www.awea.org/faq/basicen.html How Does A Wind Turbine's Energy Production Differ from Its Power Production?] </ref><ref> [http://www.ceere.org/rerl/about_wind/RERL_Fact_Sheet_2a_Capacity_Factor.pdf Wind Power: Capacity Factor, Intermittency, and what happens when the wind doesn’t blow?] retrieved 24 January 2008.</ref> For example, a 1 megawatt turbine with a capacity factor of 35% will not produce 8,760 megawatt-hours in a year (1x24x365), but only 0.35x24x365&nbsp;=&nbsp;3,066&nbsp;MWh, averaging to 0.35 MW. Online data is available for some locations and the capacity factor can be calculated from the yearly output.<ref>[http://view2.fatspaniel.net/FST/Portal/LighthouseElectrical/maritime/HostedAdminView.html Massachusetts Maritime Academy — Bourne, Mass] This 660 kW wind turbine has a capacity factor of about 19%.</ref><ref>[http://www.ieso.ca/imoweb/marketdata/windpower.asp Wind Power in Ontario] These wind farms have capacity factors of about 28 to 35%.</ref><!--Note to editors, please add links from other geographical regions.-->

Unlike fueled generating plants, the capacity factor is limited by the inherent properties of wind. Capacity factors of other types of power plant are based mostly on fuel cost, with a small amount of downtime for maintenance. [[Nuclear Power|Nuclear plants]] have low incremental fuel cost, and so are run at full output and achieve a 90% capacity factor.<ref>{{cite web
| author = Nuclear Energy Institute
| title = Nuclear Facts
| url = http://www.nei.org/doc.asp?catnum=2&catid=106
| accessdate = 2006-07-23 }}</ref> Plants with higher fuel cost are throttled back to follow load. [[Gas turbine]] plants using [[natural gas]] as fuel may be very expensive to operate and may be run only to meet peak power demand. A gas turbine plant may have an annual capacity factor of 5-25% due to relatively high energy production cost.

According to a 2007 Stanford University study published in the Journal of Applied Meteorology and Climatology, interconnecting ten or more wind farms allows 33 to 47% of the total energy produced to be used as reliable, baseload electric power, as long as minimum criteria are met for wind speed and turbine height.<ref>{{cite web
| url=http://www.eurekalert.org/pub_releases/2007-11/ams-tpo112107.php
| title=The power of multiples: Connecting wind farms can make a more reliable and cheaper power source
| date=2007-11-21
}}</ref>

== Intermittency and penetration limits ==
{{main|Intermittent Power Sources}}
[[Image:WindMills.jpg|right|thumb|Wind power mills on [[Inner Mongolia]]n grassland]]
Electricity generated from wind power can be highly variable at several different timescales: from hour to hour, daily, and seasonally. Annual variation also exists, but is not as significant. Because instantaneous electrical generation and consumption must remain in balance to maintain grid stability, this variability can present substantial challenges to incorporating large amounts of wind power into a grid system. [[Intermittent power sources|Intermittency]] and the non-dispatchable nature of wind energy production can raise costs for regulation, incremental [[operating reserve]], and (at high penetration levels) could require an increase in the already existing[[energy demand management]], [[load shedding]], or storage solutions or system interconnectoin with HVDC cables. At low levels of wind penetration, fluctuations in load and allowance for failure of large generating units requires reserve capacity that can also regulate for variability of wind generation.

A series of detailed modelling studies by Drs. Gregor Giebel,
Niels, Gylling Mortensen and Gregor Czisch, which looked at the European wide adoption of renewable energy and interlinking power grids using HVDC cables, indicates that the entire European power usage could come from renewables, with 70% total energy from wind at the same sort of costs or lower than at present. Intermittency can clearly be dealt with, according to this model by a combination of geographic dispersion to de link weather system effects, and the ability of HVDC to shift power from windy areas to non-windy areas.<ref>^ Realisable Scenarios for a Future Electricity Supply based 100% on Renewable Energies Gregor Czisch, Institute for Electrical Engineering – Efficient Energy Conversion University of Kassel, Germany, Phone/Fax: (+49) 561-804-6377/6434, E-Mail: gczisch@uni-kassel.de Gregor Giebel, Risø National Laboratory, Technical University of Denmark http://www.risoe.dk/rispubl/reports/ris-r-1608_186-195.pdf </ref><ref>Realisable Scenarios for a Future Electricity
Supply based 100% on Renewable Energies
Gregor Czisch, Institute for Electrical Engineering – Efficient Energy Conversion
University of Kassel, Germany, Phone/Fax: (+49) 561-804-6377/6434, E-Mail:
gczisch@uni-kassel.de
Gregor Giebel, Risø National Laboratory, Technical University of Denmark
http://www.risoe.dk/rispubl/reports/ris-r-1608_186-195.pdf</ref><ref>EFFECTS OF LARGE-SCALE DISTRIBUTION OF WIND
ENERGY IN AND AROUND EUROPE
Dr. Gregor Giebel
Niels Gylling Mortensen
Risø National Laboratory
P.O. Box 49
DK-4000 Roskilde
Gregor.Giebel@Risoe.DK
Tel: +45 4677 5095
Fax: +45 4677 5970
Gregor Czisch
ISET
Universität-Gesamthochschule Kassel
D-34119 Kassel
GCzisch@iset.uni-kassel.de
Tel: +49 561 7294 359
Fax: +49 561 7294 20 http://www.iset.uni-kassel.de/abt/w3-w/projekte/Risoe200305.pdf </ref>

[[Pumped-storage hydroelectricity]] or other forms of [[grid energy storage]] can store energy developed by high-wind periods and release it when needed.<ref name="Mitchell 2006">Mitchell 2006.</ref> Stored energy increases the economic value of wind energy since it can be shifted to displace higher cost generation during peak demand periods. The potential revenue from this [[arbitrage]] can offset the cost and losses of storage; the cost of storage may add 25% to the cost of any wind energy stored, but it is not envisaged that this would apply to a large proportion of wind energy generated. Thus the 2 GW Dinorwig pumped storage plant adds costs to nuclear energy in the UK for which it was built, but not to all the power produced from the 30 or so GW of nuclear plants in the UK.

Peak wind speeds may not coincide with peak demand for electrical power. In [[California]] and [[Texas]], for example, hot days in summer may have low wind speed and high electrical demand due to [[air conditioning]]. In the [[United Kingdom|UK]], however, winter demand is higher than summer demand, and so are wind speeds.<ref>{{cite web
| url=http://www.ecolo.org/documents/documents_in_english/Wind-heat-06-5pc.htm
| title=Wind Generation's Performance during the July 2006 California Heat Storm
| date=2006-08-09
| author=David Dixon, Nuclear Engineer
| publisher=US DOE, Oakland Operations
}}</ref><ref>[http://www.theiet.org/factfiles/energy/env-intro.cfm?type=pdf The Environmental Effects of Electricity Generation]</ref><ref>{{cite web |url= http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2W-4HPD59N-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=bf0326d6c9fba5f5d1fc6c86b25eb2d8
| title= Characteristics of the UK wind resource: Long-term patterns and relationship to electricity demand
| author=Graham Sinden
| publisher=Environmental Change Institute, Oxford University Centre for the Environment
| date=2005-12-01
}}</ref> [[Solar power]] tends to be complementary to wind;{{Who|date=March 2008}}<ref name=windsun>[http://blog.oregonlive.com/pdxgreen/2008/01/wind_sun_join_forces_at_washin.html Wind + sun join forces at Washington power plant] Retrieved 31 January 2008</ref><ref>[http://www.seco.cpa.state.tx.us/re_wind_smallwind.htm Small Wind Systems]</ref> on most days with no wind there is sun and on most days with no sun there is wind.{{Fact|date=March 2008}} A demonstration project at the [[Massachusetts Maritime Academy]] shows the effect.<ref>Live data is available comparing solar and wind generation [http://view2.fatspaniel.net/PV2Web/graph?series-legend_2=Solar+Panels+%20x%20+20&&series-color_2=0x009933&series-mult_2.1=20&series-item_2.1=GenerationEnergy&series-eid_2.1=67668&series-dev_1.2=KYZ&value-axis-title=kWh&max-value=5000&series-dev_1.1=KYZ&series-gw_1.2=1141&series-gw_1.1=1141&bin-type=cum&series-legend_1=Wind+Turbine&chart-height=375&bar-gap=0.10&series-color_1=0x003399&bin-duration=86400000&start-date=last-7-days&num-ticks=1&date-format=MM/dd&chart-bgcolor=0xFFFFFF&series-chan_1.2=CumEnergy2&chart-width=750&series-chan_1.1=CumEnergy&min-value=0&tick-unit=day&pattern=00.0&chart-type=bar&series-mult_1.2=-1&chart-title=Massachusetts+Maritime+Academy+Renewable+Energy+Last+Week&scale=kilowatt-hours last week] and [http://view2.fatspaniel.net/PV2Web/graph?series-legend_2=Solar+Panels+%20x%20+20&&series-color_2=0x009933&series-mult_2.1=20&series-item_2.1=GenerationEnergy&series-eid_2.1=67668&series-dev_1.2=KYZ&value-axis-title=kWh&max-value=5000&series-dev_1.1=KYZ&series-gw_1.2=1141&series-gw_1.1=1141&bin-type=cum&series-legend_1=Wind+Turbine&chart-height=375&bar-gap=0.10&series-color_1=0x003399&bin-duration=86400000&start-date=last-30-days&num-ticks=2&date-format=MM/dd&chart-bgcolor=0xFFFFFF&series-chan_1.2=CumEnergy2&chart-width=750&series-chan_1.1=CumEnergy&min-value=0&tick-unit=day&pattern=00.0&chart-type=bar&series-mult_1.2=-1&chart-title=Massachusetts+Maritime+Academy+Renewable+Energy+Last+Month&scale=kilowatt-hours last month].</ref> A combined power plant linking solar, wind, bio-gas and hydrostorage is proposed as a way to provide 100% renewable power.<ref>[http://www.solarserver.de/solarmagazin/anlage-e.html The Combined Power Plant: the first stage in providing 100% power from renewable energy]</ref>

A report from Denmark noted that their wind power network was without power for 54 days during 2002.<ref>{{cite web
| url= http://www.thomastelford.com/journals/DocumentLibrary/CIEN.158.2.66.pdf
| title= Why wind power works for Denmark
| author= |last= |first= |authorlink= |coauthors=
| date= May 2005 |format= [[PDF]] |work= |publisher= ''[[Civil Engineering]]''
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-01-15 }} </ref> Wind power advocates argue that these periods of low wind can be dealt with by simply restarting existing power stations that have been held in readiness or interlinking with HVDC <ref>^ Realisable Scenarios for a Future Electricity Supply based 100% on Renewable Energies Gregor Czisch, Institute for Electrical Engineering – Efficient Energy Conversion University of Kassel, Germany, Phone/Fax: (+49) 561-804-6377/6434, E-Mail: gczisch@uni-kassel.de Gregor Giebel, Risø National Laboratory, Technical University of Denmark http://www.risoe.dk/rispubl/reports/ris-r-1608_186-195.pdf </ref> . The cost of keeping a power station idle is in fact quite low, since the main cost of running a power station is the fuel{{Fact|date=August 2008}}.

===Penetration===

Wind energy "penetration" refers to the fraction of energy produced by wind compared with the total available generation capacity. There is no generally accepted "maximum" level of wind penetration. The limit for a particular grid will depend on the existing generating plants, pricing mechanisms, capacity for storage or demand management, and other factors. An interconnected electricity grid will already include reserve generating and transmission capacity to allow for equipment failures; this reserve capacity can also serve to regulate for the varying power generation by wind plants. Studies have indicated that 20% of the total electrical energy consumption may be incorporated with minimal difficulty.<ref>{{cite web| url= http://www.ases.org/climatechange/climate_change.pdf | title=Tackling Climate Change in the U.S.| first=| last= +format= [[PDF]] | publisher= American Solar Energy Society| year=January 2007| accessdate=2007-09-05 }}</ref> These studies have been for locations with geographically dispersed wind farms, some degree of dispatchable energy, or hydropower with storage capacity, demand management, and interconnection to a large grid area export of electricity when needed. Beyond this level, there are few technical limits, but the economic implications become more significant.

At present, few grid systems have penetration of wind energy above 5%: Denmark (values over 18%), Spain and Portugal (values over 9%), Germany and the Republic of Ireland (values over 6%). The Danish grid is heavily interconnected to the European electrical grid, and it has solved grid management problems by exporting almost half of its wind power to Norway. The correlation between electricity export and wind power production is very strong.<ref>{{cite web
| url= http://www.wind-watch.org/documents/wp-content/uploads/dk-analysis-wind.pdf
| title= "Analysis of Wind Power in the Danish Electricity Supply in 2005 and 2006" (translated from Danish)
| author= |last= |first= |authorlink= |coauthors=
| date= 10-08-2007 |format= [[PDF]] |work= |publisher=
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-01-15 }} </ref>

Denmark has active plans to increase the percentage of power generated to over 50%.<ref>Paul Fredrick Bach – "EcoGrid.dk - preparing for 50 % wind electricity in 2025". (Paul used to run the Western part of the Danish power grid, and has great experience of integrating wind power and CHP into a power grid)Claverton Conference April 2008 , Bath, http://energydiscussiongroup.wikispaces.com/2008+Conference </ref>

A study commissioned by the state of [[Minnesota]] considered penetration of up to 25%, and concluded that integration issues would be manageable and have incremental costs of less than one-half cent ($0.0045) per kWh.<ref>{{cite web
| url= http://www.puc.state.mn.us/docs/windrpt_vol%201.pdf
| title= "Final Report - 2006 Minnesota Wind Integration Study"
| author= |last= |first= |authorlink= |coauthors=
| date= [[November 30]], [[2006]] | format= [[PDF]]
| publisher= The Minnesota Public Utilities Commission
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-01-15 }} </ref>

ESB National Grid, Ireland's electric utility, in a 2004 study that, concluded that to meet the renewable energy targets set by the EU in 2001 would "increase electricity generation costs by a modest 15%"<ref>{{cite web
| url= http://www.eirgrid.com/EirGridPortal/uploads/Publications/Wind%20Impact%20Study%20-%20main%20report.pdf
| title= Impact of Wind Power Generation In Ireland on the Operation of Conventional Plant and the Economic Implications
| author= |last= |first= |authorlink= |coauthors=
| date= February, 2004 | format= [[PDF]]
| publisher= ESB National Grid
| pages= 36|language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-07-23 }} </ref>

A recent report by Sinclair Merz <ref>Sinclair Merz GROWTH SCENARIOS FOR UK RENEWABLES GENERATION
AND IMPLICATIONS FOR FUTURE DEVELOPMENTS AND
OPERATION OF ELECTRICITY NETWORKS
BERR Publication URN 08/1021
June 2008</ref> saw no dificulty in accomodating 50% of total power delivered in the UK at modest cost increases.

A series of detailed modelling studies by Drs. Gregor Giebel, Niels, Gylling Mortensen and Gregor Czisch, which looked at the European wide adoption of renewable energy and interlinking power grids using HVDC cables, indicates that the entire European power usage could come from renewables, with 70% total energy from wind at the same sort of costs or lower than at present. <ref>^ Realisable Scenarios for a Future Electricity Supply based 100% on Renewable Energies Gregor Czisch, Institute for Electrical Engineering – Efficient Energy Conversion University of Kassel, Germany, Phone/Fax: (+49) 561-804-6377/6434, E-Mail: gczisch@uni-kassel.de Gregor Giebel, Risø National Laboratory, Technical University of Denmark http://www.risoe.dk/rispubl/reports/ris-r-1608_186-195.pdf </ref><ref>^ EFFECTS OF LARGE-SCALE DISTRIBUTION OF WIND ENERGY IN AND AROUND EUROPE Dr. Gregor Giebel Niels Gylling Mortensen Risø National Laboratory P.O. Box 49 DK-4000 Roskilde Gregor.Giebel@Risoe.DK Tel: +45 4677 5095 Fax: +45 4677 5970 Gregor Czisch ISET Universität-Gesamthochschule Kassel D-34119 Kassel GCzisch@iset.uni-kassel.de Tel: +49 561 7294 359 Fax: +49 561 7294 20
http://www.iset.uni-kassel.de/abt/w3-w/projekte/Risoe200305.pdf </ref>

=== Predictability ===
{{main|Wind Power Forecasting}}

Related to variability is the short-term (hourly or daily) predictability of wind plant output. Like other electricity sources, wind energy must be "scheduled". The nature of this energy source makes it inherently variable. Wind power forecasting methods are used, but predictability of wind plant output remains low for short-term operation.

== Turbine placement ==
{{main|Wind farm}}

Good selection of a wind turbine site is critical to economic development of wind power. Aside from the availability of wind itself, other factors include the availability of transmission lines, value of energy to be produced, cost of land acquisition, land use considerations, and environmental impact of construction and operations. Off-shore locations may offset their higher construction cost with higher annual load factors, thereby reducing cost of energy produced. Wind farm designers use specialized [[wind energy software]] applications to evaluate the impact of these issues on a given wind farm design.

== Offshore Windfarms ==
{{further|List of offshore wind farms}}
On 21 December 2007, Q7, a 120MW offshore wind farm with a construction budget of €383 million, exported first power to the Dutch grid, which was a milestone for the offshore wind industry. Q7 was the first offshore wind farm to be financed by a nonrecourse loan (project finance).

The project comprised of 60 2 MW V80 Vestas machines and features monopile foundation to a depth of between 18-23 meters at a distance of about 23 km off the Dutch coast.

== Utilization of wind power ==
{{further|[[:Category:Wind power by country]]}}
<blockquote>
''Also see [[Installed wind power capacity]] for prior years''
</blockquote>
<!-- Please do not change the order of countries until end of 2008 figures are available in March 2009. Please supply a reference for any changes. -->
{| class="wikitable" style="float: right; margin-left: 10px"
! colspan="5" align=center style="background-color: #cfb;" | Installed windpower capacity (MW)<ref name="GWEC">{{cite web | url= http://www.gwec.net/uploads/media/07-02_PR_Global_Statistics_2006.pdf | title=Global Wind Energy Council (GWEC) statistics |format= [[PDF]] }}</ref><ref name="EWEA">{{cite web | url= http://www.ewea.org/fileadmin/ewea_documents/documents/publications/statistics/070129_Wind_map_2006.pdf | title=European Wind Energy Association (EWEA) statistics |format= [[PDF]] }}</ref><ref>[http://www.gwec.net/uploads/media/chartes08_EN_UPD_01.pdf Global installed wind power capacity (MW)] Global Wind Energy Council 6.2.2008</ref>
|-
! style="background-color: #cfb;" | Rank
! style="background-color: #cfb;" | Nation
! style="background-color: #cfb;" align=right | 2005
! style="background-color: #cfb;" align=right | 2006
! style="background-color: #cfb;" align=right | 2007<!--
! style="background-color: #cfb;" align=right | 2008-->
|-
| align=right | 1 || [[Wind power in Germany|Germany]] || align=right | 18,415|| align=right | 20,622 || align=right | 22,247
|-
| align=right | 2 || [[Wind power in the United States|United States]] || align=right | 9,149 || align=right | 11,603 || align=right | 16,818
|-
| align=right | 3 || [[Wind power in Spain|Spain]] || align=right | 10,028 || align=right | 11,615 || align=right | 15,145
|-
| align=right | 4 || [[Wind power in India|India]] || align=right | 4,430 || align=right | 6,270 || align=right | 8,000
|-
| align=right | 5 || [[Wind power in China|China]] || align=right | 1,260 || align=right | 2,604 || align=right | 6,050
|-
| align=right | 6 || [[Wind power in Denmark|Denmark (& Faeroe Islands)]] || align=right | 3,136 || align=right | 3,140 || align=right |3,129
|-
| align=right | 7 || [[Wind power in Italy|Italy]] || align=right | 1,718 || align=right | 2,123 || align=right | 2,726
|-
| align=right | 8 || [[Wind power in France|France]] || align=right | 757 || align=right | 1,567 || align=right | 2,454
|-
| align=right | 9 || [[Wind power in the United Kingdom|United Kingdom]] || align=right | 1,332 || align=right | 1,963 || align=right | 2,389 <!-- || align=right | 2,406 -->
|-
| align=right | 10 || [[Wind power in Portugal|Portugal]] || align=right | 1,022 || align=right | 1,716 || align=right | 2,150
|-
| align=right | 11 || [[Wind power in Canada|Canada]] || align=right | 683 || align=right | 1,459 || align=right | 1,856
|-
| align=right | 12 || [[Wind power in the Netherlands|Netherlands]] || align=right | 1,219 || align=right | 1,560 || align=right |1,747
|-
| align=right | 13 || [[Wind power in Japan|Japan]] || align=right | 1,061 || align=right | 1,394 || align=right | 1,538
|-
| align=right | 14 || [[Wind power in Austria|Austria]] || align=right | 819 || align=right | 965 || align=right |982
|-
| align=right | 15 || [[Wind power in Greece|Greece]] || align=right | 573 || align=right | 746 || align=right | 871
|-
| align=right | 16 || [[Wind power in Australia|Australia]] || align=right | 708 || align=right | 817 || align=right |824
|-
| align=right | 17 || [[Wind power in Ireland|Ireland]] || align=right | 496 || align=right | 745 || align=right | 805
|-
| align=right | 18 || [[Wind power in Sweden|Sweden]] || align=right | 510 || align=right | 572 || align=right |788
|-
| align=right | 19 || [[Wind power in Norway|Norway]] || align=right | 267 || align=right | 314 || align=right |333
|-
| align=right | 20 || [[Wind power in New Zealand|New Zealand]] || align=right | 169 || align=right | 171 || align=right | 322
|-
| align=right | 21 || [[Wind power in Egypt|Egypt]] || align=right | 145 || align=right | 230 || align=right | 310
|-
| align=right | 22 || [[Wind power in Belgium|Belgium]] || align=right | 167 || align=right | 193 || align=right |287
|-
| align=right | 23 || [[Wind power in Taiwan|Taiwan]] || align=right | 104 || align=right | 188 || align=right |282
|-
| align=right | 24 || [[Wind power in Poland|Poland]] || align=right | 83 || align=right | 153 || align=right | 276
|-
| align=right | 25 || [[Wind power in Brazil|Brazil]] || align=right | 29 || align=right | 237 || align=right |247
|-
| align=right | 26 || [[Wind power in South Korea|South Korea]] || align=right | 98 || align=right | 173 || align=right |191
|-
| align=right | 27 || [[Wind power in Turkey|Turkey]] || align=right | 20 || align=right | 51 || align=right |146
|-
| align=right | 28 || [[Wind power in Czech Republic|Czech Republic]] || align=right | 28 || align=right | 50 || align=right |116
|-
| align=right | 29 || [[Wind power in Morocco|Morocco]] || align=right | 64 || align=right | 124 || align=right |114
|-
| align=right | 30 || [[Wind power in Finland|Finland]] || align=right | 82 || align=right | 86 || align=right | 110
|-
| align=right | 31 || [[Wind power in Ukraine|Ukraine]] || align=right | 77 || align=right | 86 || align=right |89
|-
| align=right | 32 || [[Wind power in Mexico|Mexico]] || align=right | 3 || align=right | 88 || align=right |87
|-
| align=right | 33 || [[Wind power in Costa Rica|Costa Rica]] || align=right | 71 || align=right | 74 || align=right |74
|-
| align=right | 34 || [[Wind power in Bulgaria|Bulgaria]] || align=right | 6 || align=right | 36 || align=right |70
|-
| align=right | 35 || [[Wind power in Iran|Iran]] || align=right | 23 || align=right | 48 || align=right |66
|-
| align=right | 36 || [[Wind power in Hungary|Hungary]] || align=right | 18 || align=right | 61 || align=right |65
|-
| align=right | || Rest of Europe || align=right | 129 || align=right | 163 || align=right |
|-
| align=right | || Rest of Americas || align=right | 109 || align=right | 109 || align=right |
|-
| align=right | || Rest of Asia || align=right | 38 || align=right | 38 || align=right |
|-
| align=right | || Rest of Africa & Middle East || align=right | 31 || align=right | 31 || align=right |
|-
| align=right | || Rest of Oceania || align=right | 12 || align=right | 12 || align=right |
|-
|style="background-color: #cfb;" |
! style="background-color: #cfb;" | World total (MW)
| align=right style="background-color: #cfb;" | '''59,091''' || align=right style="background-color: #cfb;" | '''74,223''' || align=right style="background-color: #cfb;" | '''93,849'''
|}
{| class="wikitable" style="float: left; margin-left: 10px"
! colspan="11" align=center style="background-color: #cfb;" | Annual Wind Power Generation (TWh) / Total electricity consumption(TWh)<ref>http://www.bp.com/liveassets/bp_internet/globalbp/globalbp_uk_english/reports_and_publications/statistical_energy_review_2008/STAGING/local_assets/downloads/spreadsheets/statistical_review_full_report_workbook_2008.xls</ref><ref>http://www.sp.com.cn/sjdl/sjdltj/sjdltj0612.htm</ref><ref>http://www.sp.com.cn/sjdl/sjdltj/sjdltj0512.htm</ref><ref>[http://www.eia.doe.gov/emeu/international/electricitygeneration.html Energy Information Administration - International Electricity Generation Data<!-- Bot generated title -->]</ref>
|-
! rowspan=2 style="background-color: #cfb;" | Rank
! rowspan=2 style="background-color: #cfb;" | Nation
! style="background-color: #cfb;" align=right colspan=3 | 2005
! style="background-color: #cfb;" align=right colspan=3 | 2006
! style="background-color: #cfb;" align=right colspan=3 | 2007<!--
! style="background-color: #cfb;" align=right colspan=3 | 2008-->
|-
| style="background-color: #cfb;" align=right | Wind Power||style="background-color: #cfb;"|%||style="background-color: #cfb;" align=right | Total Power||style="background-color: #cfb;" align=right | Wind Power||style="background-color: #cfb;"|%||style="background-color: #cfb;" align=right | Total Power||style="background-color: #cfb;" align=right | Wind Power||style="background-color: #cfb;"|%|| align=right style="background-color: #cfb;" | Total Power
|-
| align=right | 1 || [[Wind power in Germany|Germany]] || align=right | 27.225||5.1|| align=right | 533.700|| align=right | 30.700||5.4|| align=right | 569.943|| align=right | 39.500||6.8|| align=right | 584.939<ref>http://www.iea.org/Textbase/stats/surveys/mes.pdf</ref>
|-
| align=right | 2 || [[Wind power in the United States|United States]] || align=right | || || align=right | 4049.8|| align=right | 26.3<ref>[http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=212819 Analysis of wind farm energy produced in the United States]</ref>||0.6|| align=right | 4104.967|| align=right | || || align=right | 4179.908
|-
| align=right | 3 || [[Wind power in Spain|Spain]] || align=right | 23.166||9.1|| align=right | 254.90|| align=right | 29.777||10.1|| align=right | 294.596|| align=right | || || align=right | 303.758
|-
| align=right | 4 || [[Wind power in India|India]] || align=right | || || align=right | 679.2|| align=right | || || align=right | 726.7|| align=right |14.7 ||1.9|| align=right | 774.7
|-
| align=right | 5 || [[Wind power in China|China]] || align=right | || || align=right | 2474.7|| align=right | 2.70||0.1|| align=right | 2834.4|| align=right | || || align=right | 3255.9
|-
| align=right | 6 || [[Wind power in Denmark|Denmark (& Faeroe Islands)]] || align=right | 6.614||19.3|| align=right | 34.30|| align=right |7.432 ||16.8|| align=right | 44.24|| align=right | || || align=right | 37.276
|-
| align=right | 7 || [[Wind power in France|France]] || align=right | || ||align=right | 547.8 || align=right |2.323||0.4|| align=right | 550.063|| align=right | || || align=right | 545.289
|-
| align=right | 8 || [[Wind power in the United Kingdom|United Kingdom]] || align=right | 0.973||0.2|| align=right | 407.365|| align=right | || || align=right | 383.898|| align=right | || || align=right | 379.756 <!-- || || align=right | 2,406 -->
|-
| align=right | 9 || [[Wind power in Portugal|Portugal]] || align=right | || || align=right | 35.0|| align=right | 4.74||9.7|| align=right | 48.876|| align=right | ||
|-
! style="background-color: #cfb;" |
! style="background-color: #cfb;" | World total (TWh)
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" | 15,746.54<ref>[http://www.eia.doe.gov/emeu/international/electricityconsumption.html International Electricity Consumption]</ref>
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" | 16,790<ref>[https://www.cia.gov/library/publications/the-world-factbook/rankorder/2042rank.html CIA - The World Factbook - Rank Order - Electricity - consumption<!-- Bot generated title -->]</ref>
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
|}
<!-- nbsp's needed to fix work wrap problems-->
The&nbsp;modern&nbsp;[[wind power industry]] began in 1979 with the serial production of wind turbines by Danish manufacturers Kuriant, Vestas, Nordtank, and Bonus. These early turbines were small by today's standards, with capacities of 20 to 30 kW each. Since then, they have increased greatly in size, while wind turbine production has expanded to many countries all over the world.

There are now many thousands of wind turbines operating, with a total capacity of 73,904&nbsp;MW of which [[wind power in Europe]] accounts for 65% (2006). Wind power was the fastest growing energy source at the end of 2004.{{Fact|date=March 2008}} World wind generation capacity more than quadrupled between 2000 and 2006. 81% of wind power installations are in the US and Europe, but the share of the top five countries in terms of new installations fell from 71% in 2004 to 62% in 2006.

In 2007, the countries with the highest total installed capacity were Germany, the United States, Spain, India, and China (see chart).

By 2010, the World Wind Energy Association expects 160GW of capacity to be installed worldwide,<ref name="wwindea" /> up from 73.9&nbsp;GW at the end of 2006, implying an anticipated net growth rate of more than 21% per year.

[[Wind power in Denmark|Denmark]] generates nearly one-fifth of its electricity with wind turbines -- the highest percentage of any country -- and is fifth in the world in total wind power generation. Denmark is prominent in the manufacturing and use of wind turbines, with a commitment made in the 1970s to eventually produce half of the country's power by wind.

In recent years, [[Wind power in the United States|the United States]] has added more wind energy to its grid than any other country; U.S. wind power capacity grew by 45% to 16.8 gigawatts in 2007.<ref>{{cite web
| url = http://www.awea.org/newsroom/releases/AWEA_Market_Release_Q4_011708.html
| title = Installed U.S. Wind Power Capacity Surged 45% in 2007
| author= |last= |first= |authorlink= |coauthors=
| date= [[January 17]], [[2008]] |work= |publisher= [[American Wind Energy Association]]
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-01-20}}</ref> Texas has become the largest wind energy producing state, surpassing [[California]]. In 2007, the state expects to add 2&nbsp;gigawatts to its existing capacity of approximately 4.5&nbsp;gigawatts. Iowa and Minnesota are expected to each produce 1&nbsp;gigawatt by late-2007.<ref>{{cite web
| url= http://awea.org/projects
| title= U.S. Wind Energy Projects
|author= |last= |first= |authorlink= |coauthors=
|date= 2008-01-16 |work= |publisher= [[American Wind Energy Association]]
|pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-02-13}} </ref> Wind power generation in the U.S. was up 31.8% in February, 2007 from February, 2006.<ref>{{cite web
| url= http://www.eia.doe.gov/cneaf/electricity/epm/epm_sum.html
| title= ''Electric Power Monthly'' (January 2008 Edition)
| author= |last= |first= |authorlink= |coauthors=
| date= [[January 15]], [[2008]] |work= |publisher= [[Energy Information Administration]]
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-01-15 }} </ref>
The average output of one megawatt of wind power is equivalent to the average electricity consumption of about 250 American households.
According to the [[American Wind Energy Association]], wind will generate enough electricity in 2008 to power just over 1% (4.5 million households) of total electricity in U.S., up from less than 0.1% in 1999. [[U.S. Department of Energy]] studies have concluded wind harvested in just three of the fifty U.S. states could provide enough electricity to power the entire nation, and that offshore wind farms could do the same job.<ref>{{cite web
| url= http://www.eere.energy.gov/windandhydro/windpoweringamerica/images/windmaps/ma_50m_800.jpg
| title= Massachusetts — 50 m Wind Power
| author= |last= |first= |authorlink= |coauthors=
| date= [[6 February]] [[2007]] |format= [[JPEG]] |work=
| publisher= U.S. [[National Renewable Energy Laboratory]]
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-01-15 }} </ref>

[[Wind power in India|India]] ranks 4th in the world with a total wind power capacity of 8,000&nbsp;MW in 2007, or 3% of all electricity produced in India. The World Wind Energy Conference in New Delhi in November 2006 has given additional impetus to the Indian wind industry.<ref name="wwindea">[http://www.wwindea.org/home/images/stories/pdfs/pr_statistics2006_290107.pdf World Wind Energy Association Statistics] (PDF).</ref> The windfarm near [[Muppandal]], [[Tamil Nadu]], [[India]], provides an impoverished village with energy.<ref>{{cite web
| year = 2005
| month =February
| url=http://www.tve.org/ho/doc.cfm?aid=1678&lang=English
| title=Tapping the Wind — India
| publisher=
| accessdate=2006-10-28
}}</ref><ref>{{cite web
| last = Watts
| first = Himangshu
| year = 2003
| month =November 11
| url=http://www.planetark.com/dailynewsstory.cfm/newsid/22758/story.htm
| title=Clean Energy Brings Windfall to Indian Village
| publisher=Reuters News Service
| accessdate=2006-10-28
}}</ref> India-based [[Suzlon Energy]] is one of the world's largest wind turbine manufacturers.<ref> [http://www.renewableenergyaccess.com/rea/partner/story;jsessionid=EA70B1B5FF984FDD7D4FF04A44A917D4?id=45465 Suzlon Energy]</ref>

In December 2003, [[General Electric]] installed the world's largest offshore wind turbines in [[Wind power in Ireland|Ireland]], and plans are being made for more such installations on the west coast, including the possible use of floating turbines.

In 2005, [[Wind power in China|China]] announced it would build a 1000-megawatt wind farm in Hebei for completion in 2020. China reportedly has set a generating target of 20,000&nbsp;MW by 2020 from renewable energy sources — it says indigenous wind power could generate up to 253,000&nbsp;MW. Following the World Wind Energy Conference in November 2004, organised by the Chinese and the World Wind Energy Association, a Chinese renewable energy law was adopted. In late 2005, the Chinese government increased the official wind energy target for the year 2020 from 20&nbsp;GW to 30&nbsp;GW.<ref>Lema, Adrian and Kristian Ruby, [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2W-4NC5T5N-1&_user=642064&_coverDate=03%2F28%2F2007&_rdoc=7&_fmt=summary&_orig=browse&_srch=doc-info(%23toc%235713%239999%23999999999%2399999%23FLA%23display%23Articles)&_cdi=5713&_sort=d&_docanchor=&view=c&_ct=83&_acct=C000034558&_version=1&_urlVersion=0&_userid=642064&md5=ea3806a5e05a7c0146a34eb06e8aa142 ”Between fragmented authoritarianism and policy coordination: Creating a Chinese market for wind energy”], Energy Policy, Vol. 35, Isue 7, July 2007. </ref>

[[Mexico]] recently opened [[La Venta II wind power project]] as an important step in reducing Mexico's consumption of fossil fuels. The 88 MW project is the first of its kind in Mexico, and will provide 13 percent of the electricity needs of the state of Oaxaca. By 2012 the project will have a capacity of 3500 MW.

Another growing market is [[Wind power in Brazil|Brazil]], with a wind potential of 143&nbsp;GW.<ref>{{cite web| url= http://www.cresesb.cepel.br/atlas_eolico_brasil/atlas-web.htm | title=Atlas do Potencial Eólico Brasileiro| accessdate=2006-04-21}}</ref> The federal government has created an incentive program, called Proinfa,<ref>{{cite web| url= http://www.eletrobras.gov.br/EM_Programas_Proinfa/default.asp | title=Eletrobrás — Centrais Elétricas Brasileiras S. A — Projeto Proinfa| accessdate=2006-04-21}}</ref> to build production capacity of 3300&nbsp;MW of renewable energy for 2008, of which 1422&nbsp;MW through wind energy. The program seeks to produce 10% of Brazilian electricity through renewable sources.

[[South Africa]] has a proposed station situated on the West Coast north of the Olifants River mouth near the town of Koekenaap, east of Vredendal in the Western Cape province. The station is proposed to have a total output of 100MW although there are negotiations to double this capacity. The plant could be operational by 2010.

[[Wind power in France|France]] has announced a target of 12,500 MW installed by 2010.

[[Wind power in Canada|Canada]] experienced rapid growth of wind capacity between 2000 and 2006, with total installed capacity increasing from 137&nbsp;MW to 1,451&nbsp;MW, and showing an annual growth rate of 38%.<ref>{{cite web| url= http://www.canwea.ca/downloads/en/PDFS/Rapid_growth_eng_April_06.pdf | title=Wind Energy: Rapid Growth| publisher=Canadian Wind Energy Association| format=PDF| accessdate=2006-04-21}}</ref> Particularly rapid growth was seen in 2006, with total capacity doubling from the 684&nbsp;MW at end-2005.<ref>{{cite web |url= http://www.canwea.ca/images/uploads/File/fiche_anglais_Dec_2006.pdf | title= Canada's Current Installed Capacity|publisher=Canadian Wind Energy Association| format=PDF| accessdate=2006-12-11}}</ref> This growth was fed by measures including installation targets, economic incentives and political support. For example, the [[Ontario]] government announced that it will introduce a feed-in tariff for wind power, referred to as 'Standard Offer Contracts', which may boost the wind industry across the province.<ref>{{cite web| url= http://www.ontario-sea.org/whatsnew.html | year=2006| title=Standard Offer Contracts Arrive In Ontario| accessdate=2006-04-21| publisher=Ontario Sustainable Energy Association}}</ref> In [[Quebec]], the [[Hydro-Québec|provincially-owned electric utility]] plans to purchase an additional 2000&nbsp;MW by 2013.<ref>{{cite web| url= http://www.hydroquebec.com/distribution/en/marchequebecois/ao_200503/index.html | title=Call for Tenders A/O 2005-03: Wind Power 2,000&nbsp;MW| publisher=Hydro-Québec| accessdate=2006-04-21}}</ref>

== Small scale wind power ==
{{Nofootnotes|section|date=August 2008}}
[[Image:Urbine221dc.jpg|thumb|right|This wind turbine charges a 12 volt [[battery (electricity)|battery]] to run 12 volt appliances.]]

Small wind generation systems with capacities of 100 kW or less are usually used to power homes, farms, and small businesses. Isolated communities that otherwise rely on diesel generators may use wind turbines to displace diesel fuel consumption. Individuals purchase these systems to reduce or eliminate their electricity bills, or simply to generate their own clean power.

Wind turbines have been used for household electricity generation in conjunction with [[Battery (electricity)|battery]] storage over many decades in remote areas. Increasingly, U.S. consumers are choosing to purchase grid-connected turbines in the 1 to 10 kilowatt range to power their whole homes. Household generator units of more than 1&nbsp;kW are now functioning in several countries, and in every state in the U.S.

Grid-connected wind turbines may use [[grid energy storage]], displacing purchased energy with local production when available. Off-grid system users either adapt to intermittent power or use batteries, [[photovoltaic]] or [[diesel]] systems to supplement the wind turbine.

In urban locations, where it is difficult to obtain predictable or large amounts of wind energy, smaller systems may still be used to run low power equipment. Equipment such as parking meters or wireless internet gateways may be powered by a wind turbine that charges a small battery, replacing the need for a connection to the power grid.

== Economics and feasibility ==

[[Image:EnerconE70-Magedeburg 2005-Steinkopfinsel01.jpg|thumb|Erection of an [[Enercon]] E70-4 in [[Germany]]]]

=== Growth and cost trends ===

Global Wind Energy Council (GWEC) figures show that 2007 recorded an increase of installed capacity of 20 GW, taking the total installed wind energy capacity to 94 GW, up from 74 GW in 2006. Despite constraints facing supply chains for wind turbines, the annual market for wind continued to increase at an estimated rate of 31% following 32% growth in 2006. In terms of economic value, the wind energy sector has become one of the important players in the energy markets, with the total value of new generating equipment installed in 2007 reaching €25 billion, or US$36 billion.<ref name=gwec2007>[http://www.gwec.net/index.php?id=30&no_cache=1&tx_ttnews%5Btt_news%5D=121&tx_ttnews%5BbackPid%5D=4&cHash=f9b4af1cd0 Continuing boom in wind energy – 20 GW of new capacity in 2007]</ref>

In 2004, wind energy cost one-fifth of what it did in the 1980s, and some expected that downward trend to continue as larger multi-megawatt [[Wind turbine|turbines]] are mass-produced.<ref>[http://arizonaenergy.org/News&Events/Uncle%20Sam's%20New%20Year's%20Resolution.htm 404 - File not found]</ref> However, installed cost averaged €1,300 per kilowatt in 2007,<ref name=gwec2007/> compared to €1,100 per kilowatt in 2005<ref>[http://www.gwec.net/fileadmin/documents/Publications/GWEC-Global_Wind_05_Report_low_res_01.pdf Global Wind 2005 Report]</ref> Not as many facilities can produce large modern turbines and their towers and foundations, so constraints develop in the supply of turbines resulting in higher costs.<ref>[http://www.sunjournal.com/story/226451-3/Business/Wind_turbine_shortage_continues_costs_rising/ Wind turbine shortage continues; costs rising]</ref>

Wind and hydro power have negligible fuel costs and relatively low maintenance costs; in economic terms, wind power has a low [[marginal cost]] and a high proportion of capital cost. The estimated [[average cost]] per unit incorporates the cost of construction of the turbine and transmission facilities, borrowed funds, return to investors (including cost of risk), estimated annual production, and other components, averaged over the projected useful life of the equipment, which may be in excess of twenty years. Energy cost estimates are highly dependent on these assumptions so published cost figures can differ substantially. A British Wind Energy Association report gives an average generation cost of onshore wind power of around 3.2&nbsp;pence per kilowatt hour (2005).<ref name="BWEA"> [http://www.bwea.com/pdf/briefings/target-2005-small.pdf BWEA report on onshore wind costs] (PDF).</ref> Cost per unit of energy produced was estimated in 2006 to be comparable to the cost of new generating capacity in the United States for coal and natural gas: wind cost was estimated at $55.80 per MWh, coal at $53.10/MWh and natural gas at $52.50.<ref>{{cite web
| url= http://www.eia.doe.gov/oiaf/ieo/pdf/0484(2006).pdf
| title= "International Energy Outlook", 2006
| author= |last= |first= |authorlink= |coauthors=
| date= |year= |month= |format= [[PDF]] |work= |publisher= [[Energy Information Administration]]
| pages= 66 |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= }} </ref> Other sources in various studies have estimated wind to be more expensive than other sources (see [[Economics of new nuclear power plants]], [[Clean coal]], and [[Carbon capture and storage]]).

Similar methods apply to other electrical energy sources. Existing generation capacity represents [[sunk costs]], and the decision to continue production will depend on marginal costs going forward, not estimated average costs at project inception. For example, the estimated cost of new wind power capacity may be lower than that for "new coal" (estimated average costs for new generation capacity) but higher than for "old coal" (marginal cost of production for existing capacity). Therefore, the choice to increase wind capacity will depend on factors including the profile of existing generation capacity.

Research from a wide variety of sources in various countries shows that support for wind power is consistently between 70 and 80 per cent amongst the general public.<ref>[http://www.windenergy.org.nz/documents/2005/050825-NZWEA-FactSheet4Tourism.pdf Fact sheet 4: Tourism]</ref>

=== Theoretical potential ===

Wind power available in the atmosphere is much greater than current world energy consumption. The most comprehensive study to date<ref>{{cite web| url= http://www.stanford.edu/group/efmh/winds/global_winds.html | title=Evaluation of global wind power| first=Cristina L.| last=Archer| coauthors=Mark Z. Jacobson| accessdate=2006-04-21}}</ref> found the potential of wind power on land and near-shore to be 72 [[Watt|TW]], equivalent to 54,000 [[Tonne of oil equivalent|MToE]] (million tons of oil equivalent) per year, or over five times the world's current energy use in all forms. The potential takes into account only locations with
mean annual wind speeds ≥ 6.9 m/s at 80 m. It assumes 6 turbines per square km for 77 m diameter, 1.5 MW-turbines on roughly 13% of the total global land area (though that land would also be available for other compatible uses such as farming). The authors acknowledge that many practical barriers would need to be overcome to reach this theoretical capacity.

The practical limit to exploitation of wind power will be set by economic and environmental factors, since the resource available is far larger than any practical means to develop it.

=== Direct costs ===

Many potential sites for wind farms are far from demand centres, requiring substantially more money to construct new transmission lines and substations.

Since the primary cost of producing wind energy is construction and there are no fuel costs, the average cost of wind energy per unit of production is dependent on a few key assumptions, such as the cost of capital and years of assumed service. The [[marginal cost]] of wind energy once a plant is constructed is usually less than 1 cent per kilowatt-hour.<ref name="Patel"> "Wind and Solar Power Systems — Design, analysis and Operation" (2nd ed., 2006), Mukund R. Patel, p. 303</ref> Since the [[cost of capital]] plays a large part in projected cost, risk (as perceived by investors) will affect projected costs per unit of electricity.

The commercial viability of wind power also depends on the pricing regime for power producers. Electricity prices are highly regulated worldwide, and in many locations may not reflect the full cost of production, let alone indirect subsidies or negative externalities. Customers may enter into long-term pricing contracts for wind to reduce the risk of future pricing changes, thereby ensuring more stable returns for projects at the development stage. These may take the form of standard offer contracts, whereby the system operator undertakes to purchase power from wind at a fixed price for a certain period (perhaps up to a limit); these prices may be different than purchase prices from other sources, and even incorporate an implicit subsidy.

In jurisdictions where the price for electricity is based on market mechanisms, revenue for all producers per unit is higher when their production coincides with periods of higher prices. The profitability of wind farms will therefore be higher if their production schedule coincides with these periods. If wind represents a significant portion of supply, average revenue per unit of production may be lower as more expensive and less-efficient forms of generation, which typically set revenue levels, are displaced from [[economic dispatch]].{{Fact|date=October 2007}} This may be of particular concern if the output of many wind plants in a market have strong temporal correlation. In economic terms, the [[marginal revenue]] of the wind sector as penetration increases may diminish.

=== External costs ===
{{Nofootnotes|section|date=August 2008}}
Most forms of energy production create some form of [[negative externality]]: costs that are not paid by the producer or consumer of the good. For electric production, the most significant externality is [[pollution]], which imposes social costs in increased health expenses, reduced agricultural productivity, and other problems. In addition, [[carbon dioxide]], a [[greenhouse gas]] produced when fossil fuels are burned, may impose even greater costs in the form of [[global warming]]. Few mechanisms currently exist to ''internalise'' these costs, and the total cost is highly uncertain. Other significant externalities can include military expenditures to ensure access to fossil fuels, remediation of polluted sites, destruction of wild habitat, loss of scenery/tourism, etc.

If the external costs are taken into account, wind energy may be competitive in more cases. Wind energy costs have generally decreased due to technology development and scale enlargement. Wind energy supporters argue that, once external costs and subsidies to other forms of electrical production are accounted for, wind energy is amongst the least costly forms of electrical production. Critics argue that the level of required subsidies, the small amount of energy needs met, and the uncertain financial returns to wind projects make it inferior to other energy sources. Intermittency and other characteristics of wind energy also have costs that may rise with higher levels of penetration, and may change the cost-benefit ratio.

=== Incentives ===
{{Nofootnotes|section|date=August 2008}}
[[Image:Wind energy converter5.jpg|thumb||Some of the over 6,000 wind turbines at [[Altamont Pass]], in California. Developed during a period of tax incentives in the 1980s, this wind farm has more turbines than any other in the United States, producing about 125 MW.<ref> [http://www.ilr.tu-berlin.de/WKA/windfarm/altcal.html Wind Plants of California's Altamont Pass]</ref> Considered largely obsolete, these turbines produce only a few tens of kilowatts each.]]

Wind energy in many jurisdictions receives some financial or other support to encourage its development. A key issue is the comparison to other forms of energy production, and their total cost. Two main points of discussion arise: direct [[subsidy|subsidies]] and [[externalities]] for various sources of electricity, including wind. Wind energy benefits from subsidies of various kinds in many jurisdictions, either to increase its attractiveness, or to compensate for subsidies received by other forms of production or which have significant negative externalities.

In the United States, wind power receives a tax credit for each [[kilowatt-hour]] produced; at 1.9 cents per kilowatt-hour in 2006, the credit has a yearly inflationary adjustment. Another tax benefit is [[accelerated depreciation]]. Many American states also provide incentives, such as exemption from property tax, mandated purchases, and additional markets for "green credits." Countries such as [[Wind Power Production Incentive|Canada]] and [[Germany]] also provide incentives for wind turbine construction, such as tax credits or minimum purchase prices for wind generation, with assured grid access (sometimes referred to as feed-in tariffs). These feed-in tariffs are typically set well above average electricity prices.

Secondary market forces also provide incentives for businesses to use wind-generated power, even if there is a premium price for the electricity. For example, socially responsible manufacturers pay utility companies a premium that goes to subsidize and build new wind power infrastructure. Companies like the Borealis Press print millions of greeting cards every year using this wind-generated power, and in return they can claim that they are making a powerful "green" effort, in addition to using recycled, chlorine-free paper, soy inks, and safe press wash. The organization Green-e http://www.green-e.org monitors business compliance with these renewable energy credits.

== Environmental effects ==
{{main|Environmental effects of wind power}}

Wind power consumes no fuel for continuing operation, and has no emissions directly related to electricity production. Operation does not produce [[carbon dioxide]], [[sulfur dioxide]], [[Mercury (element)|mercury]], [[particulate]]s, or any other type of [[air pollution]], as do fossil fuel power sources. Wind power plants consume resources in manufacturing and construction. During manufacture of the wind turbine, [[steel]], [[concrete]], [[aluminium|aluminum]] and other materials will have to be made and transported using energy-intensive processes, generally using fossil energy sources. The initial carbon dioxide emissions "pay back" is within about 9 months of operation for off shore turbines.<ref name="vestas">{{cite web
| url= http://www.vestas.com/en/about-vestas/sustainability/wind-turbines-and-the-environment/life-cycle-assessment-(lca).aspx
| title= Vestas: Life Cycle Assessments (LCA)
| author= |last= |first= |authorlink= |coauthors=
| date= |year= |month= |format= |work= |publisher=
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-02-13}} </ref>

Danger to birds is often the main complaint against the installation of a wind turbine. However, studies show that the number of birds killed by wind turbines is negligible compared to the number that die as a result of other human activities such as [[traffic]], [[hunting]], [[electric power transmission|power line]]s and [[high-rise building]]s and especially the environmental impacts of using [[fossil fuels|non-clean power sources]]. For example, in the UK, where there are several hundred turbines, about one bird is killed per turbine per year; 10&nbsp;million per year are killed by cars alone.<ref>{{cite web| url=http://www.bwea.org/media/news/birds.html| title=Birds| accessdate=2006-04-21}}</ref>

Migratory bat species appear to be particularly at risk, especially during key movement periods (spring and more importantly in fall). Lasiurines such as the [[hoary bat]], [[red bat]], and the [[silver-haired bat]] appear to be most vulnerable at North American sites. Almost nothing is known about current populations of these species and the impact on bat numbers as a result of mortality at windpower locations. Offshore wind sites 10 km or more from shore do not interact with bat populations.<ref>{{cite web| url= http://vawind.org/Assets/Docs/BCI_ridgetop_advisory.pdf | publisher=Bat Conservation International| title=Caution Regarding Placement of Wind Turbines on Wooded Ridge Tops| year=[[4 January]] [[2005]]| accessdate=2006-04-21| format=PDF}}</ref>

Aesthetics have also been a concern. The Massachusetts [[Cape Wind]] project was delayed for years mainly because of aesthetic concerns.<ref>[http://www.cbsnews.com/stories/2003/06/26/sunday/main560595.shtml Opposition to Cape Cod wind farms].</ref>

== Wind power projects ==
* [[Altamont Pass Wind Farm]]
* [[Cape Wind]] ([[Massachusetts]])
* [[Gharo Wind Power Plant]] in [[Pakistan]]
* [[Renewable energy in Portugal]]
* [[Renewable energy in Scotland]]
* [[Wind power in Australia]]
* [[Wind power in Canada]]
* [[Wind power in Denmark]]
* [[Wind power in Germany]]
* [[Wind power in Spain]]
* [[Wind power in the United Kingdom]]
* [[Wind power in the United States]]

== See also ==
{{portal|Energy}}
{{Portalpar|Sustainable development|Sustainable development.svg}}
{{commons}}

* [[Airborne wind turbine]]
* [[Distributed Energy Resources]]
* [[Electricity generation]]
* [[Energy development]]
* [[Green energy]]
* [[Green tax shift]]
* [[Grid energy storage]]
* [[List of countries by renewable electricity production]]
* [[List of large wind farms]]
* [[List of offshore wind farms]]
* [[List of wind turbine manufacturers]]
* [[Merchant Wind Power]]
* Microeolic generator: [[Philippe Starck]].
* [[Pickens plan]]
* [[Renewable energy]]
* [[SkySails]]
* [[Vaneless ion wind generator]]
* [[Wind profiler]]
* [[Wind profile power law]]
* [[Wind-Diesel Hybrid Power Systems|Wind-Diesel]]
* The [[Windbelt]], a non-turbine approach to tapping wind power
* [[World energy resources and consumption]]
* [[:Category:Wind power by country]]

== References ==

{{reflist|2}}

==External links==
<!-- ==External links== -->
<!-- Discuss new proposed links on talk page first. -->
<!-- See [[Wikipedia:External links]] and [[Wikipedia:Spam]] for details -->
*[http://www.bwea.com/energy/briefing-sheets.html British Wind Energy Association (BWEA) Briefing Sheets]
*[http://www.fas.org/sgp/crs/misc/RL34546.pdf Wind Power in the United States: Technology, Economic, and Policy Issues] (53p), Congressional Research Service, June 2008
=== Wind power projects ===
* [http://www.thewindpower.net/index_en.php Database of projects throughout the whole World]
* [http://www.offshorewind.net Database of offshore wind projects in North America]
* [http://www.windpowerhandbook.com/ Wind Project Community Organizing] - This free website includes dozens of current articles, links and resources about windpower, problem issues, community programs, case studies, lesson plans, etc.
* [http://www.asiaing.com/wind-energy-siting-handbook.html Wind Energy Siting Handbook]

{{Wind power|state=expanded}}
{{Renewable energy by country}}
{{Sustainability}}

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