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[[Image:Windenergy.jpg|thumb|220px| A [[wind turbine]].]]

{{Renewable energy sources}}
{{Sustainable energy}}

'''Wind power''' is the conversion of [[wind]] energy into a useful form of energy, such as using [[wind turbine]]s to make electricity, [[wind mill]]s for mechanical power, [[wind pump]]s for pumping water or drainage, or sails to propel ships.

At the end of 2009, worldwide [[nameplate capacity]] of wind-powered generators was 157.9 [[gigawatt]]s (GW).<ref name="wwea">{{cite web
| publisher = [[World Wind Energy Association]]
| title = World Wind Energy Report 2008
| format = PDF
| work = Report
| date = February 2009
| url = http://www.wwindea.org/home/images/stories/worldwindenergyreport2008_s.pdf
| accessdate = 16-March-2009}}</ref>, which is about 1.5% of worldwide electricity usage;<ref name="wwea"/><ref name=wor>[http://www.worldwatch.org/node/6102?emc=el&m=239273&l=5&v=ca5d0bd2df Wind Power Increase in 2008 Exceeds 10-year Average Growth Rate]</ref> and is growing rapidly, having doubled in the three years between 2005 and 2008. Several countries have achieved relatively high levels of wind power penetration (with large governmental subsidies), such as 19% of stationary electricity production in [[Wind power in Denmark|Denmark]], 13% in [[Wind power in Spain|Spain]]<ref>http://www.ree.es/sala_prensa/web/notas_detalle.aspx?id_nota=151 </ref> and [[Wind power in Portugal|Portugal]], and 7% in [[Wind power in Germany|Germany]] and the [[Wind power in Ireland|Republic of Ireland]] in 2008. As of May 2009, eighty countries around the world are using wind power on a commercial basis.<ref name=wor/>

Large-scale [[wind farms]] are connected to the [[electric power transmission]] network; smaller facilities are used to provide electricity to isolated locations. Utility companies increasingly [[Net metering|buy back surplus electricity]] produced by small domestic turbines. Wind energy as a power source is attractive as an alternative to [[fossil fuel]]s, because it is plentiful, [[renewable energy|renewable]], widely distributed, clean, and produces no [[greenhouse gas emissions]]. However, the construction of wind farms is not universally welcomed because of their visual impact and other [[Environmental effects of wind power|effects on the environment]].

Wind power is [[Dispatchable generation|non-dispatchable]], meaning that for economic operation, all of the available output must be taken when it is available. Other resources, such as [[hydropower]], and standard [[load management]] techniques must be used to match supply with demand. The [[Intermittent power sources|intermittency]] of wind seldom creates problems when using wind power to supply a low proportion of total demand.<ref name="ieawind">{{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><ref name="claverton-energy.com">http://www.claverton-energy.com/wind-energy-variability-new-reports.html</ref>

== History ==
{{Main|History of wind power}}
[[File:Fourteenth century windmill.png|thumb|Medieval depiction of a windmill]]
[[File:Toro de osborne.jpg|thumb|right|Windmills are typically installed in favourable windy locations. In the image, [[Wind power in Spain|generators in Spain]]]]
Humans have been using wind power for at least 5,500 years to propel sailboats and sailing ships, and architects have used wind-driven [[natural ventilation]] in buildings since similarly ancient times. [[Windmill]]s have been used for irrigation pumping and for milling grain since the 7th century AD..

In the United States, the development of the [[windpumps|"water-pumping windmill"]] was the major factor in allowing the farming and ranching of vast areas otherwise devoid of readily accessible water. Windpumps contributed to the expansion of rail transport systems throughout the world, by pumping water from water wells for the [[steam locomotive]]s.<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. When fitted with generators and battery banks, small wind machines provided electricity to isolated farms.

In July 1887, a Scottish academic, [[Professor James Blyth]], undertook wind power experiments that culminated in a UK patent in 1891.<ref name="Price">{{cite journal|last=Price|first=Trevor J|title=James Blyth - Britain's first modern wind power engineer|url=http://www.ingentaconnect.com/content/mscp/wind/2005/00000029/00000003/art00002|journal=Wind Engineering|volume=29|issue=3|pages=191–200|date=3 May 2005|doi=10.1260/030952405774354921}}</ref> In the United States, [[Charles F. Brush]] produced electricity using a wind powered machine, starting in the winter of 1887-1888, which powered his home and laboratory until about 1900. In the 1890s, the Danish scientist and inventor [[Poul la Cour]] constructed wind turbines to generate electricity, which was then used to produce [[hydrogen]].<ref name="Price"/> These were the first of what was to become the modern form of wind turbine.

Small wind turbines for lighting of isolated rural buildings were widespread in the first part of the 20th century. Larger units intended for connection to a distribution network were tried at several locations including [[Balaklava]] USSR in 1931 and in a 1.25 [[megawatt]] (MW) [[Smith-Putnam wind turbine|experimental unit in Vermont]] in 1941.

The modern [[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 20–30&nbsp;kW each. Since then, they have increased greatly in size, while wind turbine production has expanded to many countries.

== Wind energy ==
{{See|Wind}}
[[Image:Lee Ranch Wind Speed Frequency.png|thumb|right|350px|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 {{convert|100|m|ft|0|abbr=on}} diameter circle facing directly into the wind. Total energy for the year through that circle was 15.4 [[gigawatt-hour]]s (GW·h).]]

The Earth is unevenly heated by the sun, such that the poles receive less energy from the sun than the equator; along with this, 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 {{convert|160|km/h|mph|abbr=on}} occur. Eventually, the wind energy is converted through friction into diffuse heat throughout the Earth's surface and the atmosphere.

The total amount of economically extractable power available from the wind is considerably more than present human power use from all sources.<ref>[http://www.claverton-energy.com/where-does-the-wind-come-from-and-how-much-is-there.html "Where does the wind come from and how much is there"] - Claverton Energy Conference, Bath 24th Oct 2008 </ref> An estimated 72&nbsp;[[terawatt]]&nbsp;(TW) of wind power on the Earth potentially can be commercially viable,<ref> [http://www.ocean.udel.edu/windpower/ResourceMap/index-world.html Mapping the global wind power resource]</ref> compared to about [[World energy resources and consumption|15&nbsp;TW average global power consumption]] from all sources in 2005. Not all the energy of the wind flowing past a given point can be recovered (see [[Betz' law]]).

=== Distribution of wind speed ===

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 [[Weibull distribution|Weibull]] model closely mirrors the actual distribution of hourly wind speeds at many locations. The Weibull factor is often close to 2 and therefore a [[Rayleigh distribution]] can be used as a less accurate, but simpler model.

Because so much power is generated by higher wind speed, much of the energy comes in short bursts. The 2002 Lee Ranch sample is telling;<ref>[http://www.sandia.gov/wind/other/LeeRanchData-2002.pdf Lee Ranch Data 2002] Retrieved 2008-09-14</ref> half of the energy available arrived in just 15% of the operating time. The consequence is that wind energy from a particular turbine or wind farm does not have as consistent an output as fuel-fired power plants; utilities that use wind power provide power from starting existing generation for times when the wind is weak thus wind power is primarily a fuel saver rather than a capacity saver. Making wind power more consistent requires that various existing technologies and methods be extended, in particular the use of stronger inter-regional transmission lines to link widely distributed wind farms. Problems of variability are addressed by [[grid energy storage]], [[Battery (electricity)|batteries]], [[pumped-storage hydroelectricity]] and [[energy demand management]].<ref>[http://www.claverton-energy.com/common-affordable-and-renewable-electricity-supply-for-europe-and-its-neighbourhood.html "Common Affordable and Renewable Electricity Supply for Europe"] Claverton Energy Conference, Bath, Oct 24th 2008</ref>

== Electricity generation ==

[[Image:Scout moor gearbox, rotor shaft and brake assembly.jpg|thumb|right|Typical components of a wind turbine (gearbox, rotor shaft and brake assembly) being lifted into position]]

In a [[wind farm]], individual turbines are interconnected with a medium voltage (often 34.5 kV), power collection system and communications network. At a substation, this medium-voltage electrical current is increased in voltage with a [[transformer]] for connection to the high voltage [[electric power transmission]] system.

The surplus power produced by domestic microgenerators can, in some jurisdictions, be fed into the network and sold to the utility company, producing a retail credit for the microgenerators' owners to offset their energy costs.<ref>[http://www.aessolarenergy.com/sell_electricity.htm "Sell electricity back to the utility company"] Retrieved on 7 november 2008</ref><ref>[http://www.timesonline.co.uk/tol/news/environment/article4187635.ece ''[[The Times]]'' 22 June 2008 "Home-made energy to prop up grid"] Retrieved on 7 November 2008</ref>

=== Grid management ===
[[Induction generator]]s, often used for wind power, require [[reactive power]] for [[Excitation (magnetic)|excitation]] so [[Electrical substation|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 [[Wind energy software|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 (see: [[Low voltage ride through]]). In particular, induction generators cannot support the system voltage during faults, unlike steam or hydro turbine-driven synchronous generators. [[Doubly-fed electric machine|Doubly-fed machines]]—wind turbines with solid-state converters between the turbine generator and the collector system—generally have 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 name=Demeo2005>{{citation
| last1 = Demeo | first1 = E.A.
| last2 = Grant | first2 = W.
| last3 = Milligan | first3 = M.R.
| last4 = Schuerger | first4 = M.J.
| year = 2005
| title = Wind plant integration
| journal = Power and Energy Magazine, IEEE
| volume = 3
| issue = 6
| pages = 38–46
| doi = 10.1109/MPAE.2005.1524619
| url = http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1524619
}}</ref><ref name=Zavadil2005>{{citation
| last1 = Zavadil | first1 = R.
| last2 = Miller | first2 = N.
| last3 = Ellis | first3 = A.
| last4 = Muljadi | first4 = E.
| year = 2005
| title = Making connections
| journal = Power and Energy Magazine, IEEE
| volume = 3
| issue = 6
| pages = 26–37
| doi = 10.1109/MPAE.2005.1524618
| url = http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1524618
}}</ref>

=== Capacity factor ===
[[Image:WorldWindPower2008.png|thumb|Worldwide installed capacity 1997–2008, with projection 2009–13 based on an exponential fit. Data source: [http://www.wwindea.org/ WWEA]]]
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.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&nbsp;MW turbine with a capacity factor of 35% will not produce 8,760&nbsp;MW·h in a year (1 × 24 × 365), but only 1 × 0.35 × 24 × 365&nbsp;=&nbsp;3,066&nbsp;MW·h, averaging to 0.35&nbsp;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&nbsp;— Bourne, Mass] This 660&nbsp;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 28–35%.</ref>

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.
Plants with higher fuel cost are throttled back to [[Load following power plant|follow load]]. [[Gas turbine]] plants using [[natural gas]] as fuel may be very expensive to operate and may be run only to meet [[Peaking power plant|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 can allow an average of 33% of the total energy produced to be used as reliable, [[baseload power|baseload electric power]], as long as minimum criteria are met for wind speed and turbine height.<ref name="connecting_wind_farms">{{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><ref name=Archer2007>{{citation
| title = Supplying Baseload Power and Reducing Transmission Requirements by Interconnecting Wind Farms
| author = Archer, C. L.; Jacobson, M. Z.
| year = 2007
| journal = Journal of Applied Meteorology and Climatology
| volume = 46
| issue = 11
| pages = 1701–1717
| url = http://www.stanford.edu/group/efmh/winds/aj07_jamc.pdf
| publisher = [[American Meteorological Society]]
}}</ref>

In a 2008 study released by the U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy, the capacity factor achieved by the wind turbine fleet is shown to be increasing as the technology improves. The capacity factor achieved by new wind turbines in 2004 and 2005 reached 36%.<ref>[http://www.windpoweringamerica.gov/pdfs/20_percent_wind_2.pdf]46. U.S. Department of Energy; Energy Efficiency and Renewable Energy "20% Wind Energy by 2030"</ref>

=== 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://ases.org/images/stories/file/ASES/climate_change.pdf | title=Tackling Climate Change in the U.S.|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. Electrical utilities continue to study the effects of large (20% or more) scale penetration of wind generation on system stability and economics.<ref>
The UK System Operator, [[National Grid (UK)]] have quoted estimates of balancing costs for 40% wind and these lie in the range £500-1000M per annum. "These balancing costs represent an additional £6 to £12 per annum on average consumer electricity bill of around £390." {{cite web| work=National Grid | date=2008 | title=National Grid's response to the House of Lords Economic Affairs Select Committee investigating the economics of renewable energy|
url=http://www.parliament.uk/documents/upload/EA273%20National%20Grid%20Response%20on%20Economics%20of%20Renewable%20Energy.pdf}}</ref><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 kW·h.{{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><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%" {{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><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>

At present, a few grid systems have penetration of wind energy above 5%: Denmark (values over 19%), Spain and Portugal (values over 11%), Germany and the Republic of Ireland (values over 6%).
For instance, in the morning hours of 8 November 2009, wind energy produced covered more than half the electricity demand in Spain, setting a new record, and without problems for the network.<ref> Wind power produced more than half the electricity in Spain during the early morning hours http://www.ree.es/ingles/sala_prensa/web/notas_detalle.aspx?id_nota=117 </ref>

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.countryguardian.net/2008.%20Wind%20power%20in%20Denmark.%20%5BDecember%202008%20version%20plus%20%20Refs%5D%20(1).pdf
| title= Wind power in Denmark
| author=Dr V.C. Mason |last=Mason |first=V.C. |authorlink= |coauthors=
| date= December 2008 |format= [[PDF]] |work= |publisher=
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2009-08-07 }} </ref>

=== Intermittency and penetration limits ===
{{Main|Intermittent Power Sources}}
{{See also|Wind Power Forecasting}}

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

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-[[Intermittent power sources#Terminology|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 interconnection with [[High-voltage direct current|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. Wind power can be replaced by other power stations during low wind periods. Transmission networks must already cope with outages of generation plant and daily changes in electrical demand. Systems with large wind capacity components may need more spinning reserve (plants operating at less than full load).<ref> http://www.claverton-energy.com/is-wind-power-reliable-an-authoritative-article-from-david-millborrow-who-is-technically-experienced-and-numerate-unlike-many-other-commentators.html</ref><ref>http://www.claverton-energy.com/download/316/</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. The 2 GW Dinorwig pumped storage plant in Wales evens out electrical demand peaks, and allows base-load suppliers to run their plant more efficiently. Although pumped storage power systems are only about 75% efficient, and have high installation costs, their low running costs and ability to reduce the required electrical base-load can save both fuel and total electrical generation costs.<ref>[http://www.fhc.co.uk/dinorwig.html l First Hydro, Dinorwig]</ref><ref>[The Future of Electrical Energy Storage: The economics and potential of new technologies 2/1/2009 ID RET2107622]</ref>

In particular geographic regions, peak wind speeds may not coincide with peak demand for electrical power. In the US states of [[California]] and [[Texas]], for example, hot days in summer may have low wind speed and high electrical demand due to [[air conditioning]]. Some utilities subsidize the purchase of [[geothermal heat pump]]s by their customers, to reduce electricity demand during the summer months by making air conditioning up to 70% more efficient;<ref name="geothermal_incentive">{{Cite web
|url=http://www.capitalelec.com/Energy_Efficiency/ground_source/index.html
|title=Geothermal Heat Pumps
|publisher=[[Capital Electric Cooperative]]
|accessdate=2008-10-05
}}</ref> widespread adoption of this technology would better match electricity demand to wind availability in areas with hot summers and low summer winds. Another option is to interconnect widely dispersed geographic areas with an HVDC "[[Super grid]]". In the USA it is estimated that to upgrade the transmission system to take in planned or potential renewables would cost at least $60 billion<ref>[http://www.nytimes.com/2008/08/27/business/27grid.html?_r=2&oref=slogin&oref=slogin Wind Energy Bumps Into Power Grid’s Limits] Published: August 26, 2008</ref>. Total annual US power consumption in 2006 was 4 thousand billion kW·h.<ref>[http://www.eia.doe.gov/cneaf/electricity/epa/figes1.html U.S. Electric Power Industry Net Generation] retrieved 12 March 2009</ref> Over an asset life of 40 years and low cost utility investment grade funding, the cost of $60 billion investment would be about 5% p.a. (i.e. $3 billion p.a.) Dividing by total power used gives an increased unit cost of around $3,000,000,000 × 100 / 4,000 × 1 exp9 = 0.075 cent/kW·h.

In the UK, demand for electricity is higher in winter than in summer, 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>{{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.<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 daily to weekly timescales, [[high pressure area]]s tend to bring clear skies and low surface winds, whereas [[low pressure area]]s tend to be windier and cloudier. On seasonal timescales, solar energy typically peaks in summer, whereas in many areas wind energy is lower in summer and higher in winter.<ref name="cleveland_water_crib">{{Cite web
|url=http://www.development.cuyahogacounty.us/pdf_development/en-US/ExeSum_WindResrc_CleveWtrCribMntr_Reprt.pdf
|title=Lake Erie Wind Resource Report, Cleveland Water Crib Monitoring Site, Two-Year Report Executive Summary
|format=PDF
|publisher=Green Energy Ohio
|date=2008-01-10
|accessdate=2008-11-27
}} This study measured up to four times as much average wind power during winter as in summer for the test site.</ref> Thus the intermittencies of wind and solar power tend to cancel each other somewhat. A demonstration project at the [[Massachusetts Maritime Academy]] shows the effect.<ref>Live data is available comparing [http://view2.fatspaniel.net/PV2Web/merge?view=PV/detail/HostedAdmin&eid=67668 solar] and [http://view2.fatspaniel.net/FST/Portal/LighthouseElectrical/maritime/HostedAdminView.html wind] generation [http://view2.fatspaniel.net/PV2Web/graph?value-axis-title=kWh&max-value=660&series-dev_1.1=KYZ&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=3600000&start-date={{#time:m/d/Y|-2 day}}+00:00:00&chart-bgcolor=0xFFFFFF&chart-width=750&series-chan_1.1=CumEnergy&min-value=0&tick-unit=hour&num-ticks=4&pattern=000&chart-type=bar&series-mult_1.2=-1&chart-title=Massachusetts+Maritime+Academy+Renewable+Energy+-+Hourly&scale=kilowatt-hours&series-item_2.1=GenerationEnergy&series-mult_2.1=10&series-color_2=0x009933&eid=67668&series-legend_2=Solar+Panels+x+10 hourly] since the day before yesterday, daily for [http://view2.fatspaniel.net/PV2Web/graph?series-legend_2=Solar+Panels+x+10&series-color_2=0x009933&series-mult_2.1=10&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+x+10&series-color_2=0x009933&series-mult_2.1=10&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], and monthly for the [http://view2.fatspaniel.net/PV2Web/graph?series-legend_2=Solar+Panels+x+10&series-color_2=0x009933&series-mult_2.1=10&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=1M&start-date=last-12-months&num-ticks=1&date-format=MMM&chart-bgcolor=0xFFFFFF&series-chan_1.2=CumEnergy2&chart-width=750&series-chan_1.1=CumEnergy&min-value=0&tick-unit=month&pattern=00.0&chart-type=bar&series-mult_1.2=-1&chart-title=Massachusetts+Maritime+Academy+Renewable+Energy+Last+Year&scale=kilowatt-hours last year].</ref> The Institute for Solar Energy Supply Technology of the [[University of Kassel]] pilot-tested a [[virtual power plant|combined power plant]] linking solar, wind, [[biogas]] and [[Pumped-storage hydroelectricity|hydrostorage]] to provide load-following power around the clock, entirely from renewable sources.<ref name="combined_power_plant">{{Cite web
|url=http://www.solarserver.de/solarmagazin/anlagejanuar2008_e.html
|title=The Combined Power Plant: the first stage in providing 100% power from renewable energy
|month=January
|year=2008
|accessdate=2008-10-10
|publisher=SolarServer
}}</ref>

A report from Denmark noted that their wind power network was without power for 54 days during 2002.<ref name="Denmark">{{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 name="Czisch-Giebel">[http://www.risoe.dk/rispubl/reports/ris-r-1608_186-195.pdf Realisable Scenarios for a Future Electricity Supply based 100% on Renewable Energies] Gregor Czisch, University of Kassel, Germany and Gregor Giebel, Risø National Laboratory, Technical University of Denmark</ref> Electrical grids with slow-responding thermal power plants and without ties to networks with hydroelectric generation may have to limit the use of wind power. <ref name="Denmark" />

Three reports on the wind variability in the UK issued in 2009, generally agree that variability of wind needs to be taken into account, but it does not make the grid unmanageable; and the additional costs, which are modest, can be quantified.<ref>[http://www.claverton-energy.com/wind-energy-variability-new-reports.html Wind Energy Variability and Intermittency in the UK]</ref>

A 2006 International Energy Agency forum presented costs for managing intermittency as a function of wind-energy's share of total capacity for several countries, as shown:
<center>
'''Increase in system operation costs, Euros per MW·h, for 10% and 20% wind share'''<ref name="ieawind">http://www.ieawind.org/AnnexXXV/Meetings/Oklahoma/IEA%20SysOp%20GWPC2006%20paper_final.pdf</ref>


</center><center>
{| class="wikitable"
|-
!
! 10%
! 20%
|-
| Germany
| 2.5
| 3.2
|-
| Denmark
| 0.4
| 0.8
|-
| Finland
| 0.3
| 1.5
|-
| Norway
| 0.1
| 0.3
|-
| Sweden
| 0.3
| 0.7
|}</center>

===Capacity credit and fuel saving===
Many commentators concentrate on whether or not wind has any "capacity credit" without defining what they mean by this and its relevance. Wind does have a capacity credit, using a widely accepted and meaningful definition, equal to about 20% of its rated output (but this figure varies depending on actual circumstances). This means that reserve capacity on a system equal in MW to 20% of added wind could be retired when such wind is added without affecting system security or robustness. But the precise value is irrelevant since the main value of wind (in the UK, worth 5 times the capacity credit value<ref>[ http://www.claverton-energy.com/conference/programme Dr Graham Sinden, Oxford Environmental Change Institute: The implications of the Em’s 20/20/20 directive on renewable electricity generation requirements in the UK, and the potential role of offshore wind power in this context. (Graham Sinden has published a number of papers looking at the effects of integrating variable/intermittent generation into the generation mix) ]</ref>) is its fuel and CO2 savings.

== Turbine placement ==
{{Main|Wind farm}}
{{See also|Wind atlas}}

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. [[List of offshore wind farms|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.{{Citation needed|date=September 2009}}

[[Wind profile power law#Wind power density|Wind power density]] (WPD) is a calculation of the effective power of the wind at a particular location.<ref> http://www.awea.org/faq/basicwr.html Basic Principles of Wind Resource Evaluation, retrieved July&nbsp;28, 2009 </ref> A map showing the distribution of wind power density is a first step in identifying possible locations for wind turbines. In the United States, the [[National Renewable Energy Laboratory]] classifies wind power density into ascending classes. The larger the WPD at a location, the higher it is rated by class. Wind power classes&nbsp;3 (300–400&nbsp;W/m<sup>2</sup> at 50&nbsp;m altitude) to 7 (800–2000&nbsp;W/m<sup>2</sup> at 50&nbsp;m altitude) are generally considered suitable for wind power development. There are 625,000&nbsp;km<sup>2</sup> in the contiguous United States that have class&nbsp;3 or higher wind resources and which are within 10&nbsp;km of electric transmission lines. If this area is fully utilized for wind power, it would produce power at the average continuous equivalent rate of 734&nbsp;GW<sub>e</sub>.
For comparison, in 2007 the US consumed electricity at an average rate of 474&nbsp;GW,<ref> {{cite web
| url= http://www.eia.doe.gov/cneaf/electricity/epm/table1_1.html
| title= Net Generation by Energy Source: Total (All Sectors)
| date= September&nbsp;11, 2009 |work= |publisher= [[Energy Information Administration]] (EIA), [[United States Department of Energy|Dept. of Energy]] (DOE)
| accessdate= 2009-09-22 }} </ref>
from a total generating capacity of 1,088&nbsp;GW.<ref> {{cite web
| url= http://www.eia.doe.gov/cneaf/electricity/epa/epat2p2.html
| title= Existing Capacity by Energy Source
| date= January&nbsp;21, 2009 |work= |publisher= EIA, DOE
| accessdate= 2009-09-22 }} </ref>

== Wind power usage ==
{{further|[[:Category:Wind power by country]]|[[Installed wind power capacity]]}}
{| class="wikitable sortable" style="float: right; margin-left: 10px"
|+'''Installed windpower capacity (MW)'''<ref name=wwea/><ref>http://www.gwec.net/fileadmin/documents/PressReleases/PR_2010/Annex%20stats%20PR%202009.pdf</ref>
|-
! style="background-color: #cfb;" | #
! 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
! style="background-color: #cfb;" align=right | 2009
|-
| align=right | - || {{flagicon|European Union}} [[Wind power in the European Union|European Union]] || align=right | 40,722 || align=right | 48,122 || align=right | 56,614 || align=right | 65,255 || align=right | 74,767<ref> http://www.ewea.org/fileadmin/ewea_documents/documents/statistics/general_stats_2009.pdf </ref>
|-
| align=right | 1 || {{flagicon|United States}} [[Wind power in the United States|United States]] || align=right | 9,149 || align=right | 11,603 || align=right | 16,819 || align=right | 25,170 || align=right | 35,159<ref> http://www.reuters.com/article/idUSN2211296320100126?type=marketsNews </ref>
|-
| align=right | 2 || {{flagicon|Germany}} [[Wind power in Germany|Germany]] || align=right | 18,428 || align=right | 20,622 || align=right | 22,247 || align=right | 23,903 || align=right | 25,777 <ref>German Federal Wind Energy Association, [http://www.wind-energie.de/fileadmin/dokumente/statistiken/WE%20Deutschland/100127_PM_Dateien/DEWI_Statistik_2009.pdf Status der Windenergienutzung in Deutschland], 31 December 2009, visited on 28 January 2010 </ref>
|-
| align=right | 3 || {{flagicon|China}} [[Wind power in China|China]] || align=right | 1,266 || align=right | 2,599 || align=right | 5,912 || align=right | 12,210 || align=right | 25,104
|-
| align=right | 4 || {{flagicon|Spain}} [[Wind power in Spain|Spain]] || align=right | 10,028 || align=right | 11,630 || align=right | 15,145 || align=right | 16,740 || align=right | 19,149 <ref>[[ Asociación Empresarial Eólica]], [http://www.aeeolica.es/index.php], 1 Febrary 2010 </ref>
|-
| align=right | 5 || {{flagicon|India}} [[Wind power in India|India]] || align=right | 4,430 || align=right | 6,270 || align=right | 7,850 || align=right | 9,587 || align=right | 10,925
|-
| align=right | 6 || {{flagicon|Italy}} [[Wind power in Italy|Italy]] || align=right | 1,718 || align=right | 2,123 || align=right | 2,726 || align=right | 3,537|| align=right | 4,850
|-
| align=right | 7 || {{flagicon|France}} [[Wind power in France|France]] || align=right | 779 || align=right | 1,589 || align=right | 2,477 || align=right | 3,426 || align=right | 4,410
|-
| align=right | 8 || {{flagicon|United Kingdom}} [[Wind power in the United Kingdom|United Kingdom]] || align=right | 1,353 || align=right | 1,963 || align=right | 2,389 || align=right | 3,288 || align=right | 4,070
|-
| align=right | 9 || {{flagicon|Portugal}} [[Wind power in Portugal|Portugal]] || align=right | 1,022 || align=right | 1,716 || align=right | 2,130 || align=right | 2,862 || align=right | 3,535
|-
| align=right | 10 || {{flagicon| Denmark}} [[Wind power in Denmark|Denmark]] || align=right | 3,132 || align=right | 3,140 || align=right | 3,129 || align=right | 3,164 || align=right | 3,465
|-
| align=right | 11 || {{flagicon|Canada}} [[Wind power in Canada|Canada]] || align=right | 683 || align=right | 1,460 || align=right | 1,846 || align=right | 2,369 || align=right | 3,319
|-
| align=right | 12 || {{flagicon|Netherlands}} [[Wind power in the Netherlands|Netherlands]] || align=right | 1,236 || align=right | 1,571 || align=right |1,759 || align=right | 2,237 || align=right | 2,229
|-
| align=right | 13 || {{flagicon|Japan}} [[Wind power in Japan|Japan]] || align=right | 1,040 || align=right | 1,309 || align=right | 1,528 || align=right | 1,880|| align=right | 2,056
|-
| align=right | 14 || {{flagicon|Australia}} [[Wind power in Australia|Australia]] || align=right | 579 || align=right | 817 || align=right | 817 || align=right | 1,494|| align=right | 1,712
|-
| align=right | 15 || {{flagicon|Sweden}} [[Wind power in Sweden|Sweden]] || align=right | 509 || align=right | 571 || align=right | 831 || align=right | 1,067 || align=right | 1,560
|-
| align=right | 16 ||{{flagicon|Ireland}} [[Wind power in Ireland|Ireland]] || align=right | 495 || align=right | 746 || align=right | 805 || align=right | 1,245 || align=right | 1,260
|-
| align=right | 17 ||{{flagicon|Greece}} [[Wind power in Greece|Greece]] || align=right | 573 || align=right | 758 || align=right | 873 || align=right | 990 || align=right | 1,087
|-
| align=right | 18 || {{flagicon|Austria}} [[Wind power in Austria|Austria]] || align=right | 819 || align=right | 965 || align=right | 982 || align=right | 995 || align=right | 995
|-
| align=right | 19 ||{{flagicon|Turkey}} [[Wind power in Turkey|Turkey]] || align=right | 20 || align=right | 65 || align=right | 207 || align=right | 433 || align=right | 801
|-
| align=right | 20 || {{flagicon|Poland}} [[Wind power in Poland|Poland]] || align=right | 83 || align=right | 153 || align=right | 276 || align=right | 472 || align=right | 725
|-
| align=right | 21 || {{flagicon|Brazil}} [[Wind power in Brazil|Brazil]] || align=right | 29 || align=right | 237 || align=right | 247 || align=right | 339|| align=right | 606
|-
| align=right | 22 ||{{flagicon|Belgium}} [[Wind power in Belgium|Belgium]] || align=right | 167 || align=right | 194 || align=right | 287 || align=right | 384 || align=right | 563
|-
| align=right | 23 ||{{flagicon|New Zealand}} [[Wind power in New Zealand|New Zealand]] || align=right | 168 || align=right | 171 || align=right | 322 || align=right | 325|| align=right | 497
|-
| align=right | 24 || {{flagicon|Taiwan}} [[Wind power in Taiwan|Taiwan]] || align=right | 104 || align=right | 188 || align=right | 280 || align=right | 358|| align=right | 436
|-
| align=right | 25 || {{flagicon|Norway}} [[Wind power in Norway|Norway]] || align=right | 268 || align=right | 325 || align=right | 333 || align=right | 428 || align=right | 431
|-
| align=right | 26 || {{flagicon|Egypt}} [[Wind power in Egypt|Egypt]] || align=right | 145 || align=right | 230 || align=right | 310 || align=right | 390|| align=right | 430
|-
| align=right | 27 || {{flagicon|South Korea}} [[Wind power in South Korea|South Korea]] || align=right | 119 || align=right | 176 || align=right | 192 || align=right | 278|| align=right | 348
|-
| align=right | 28 || {{flagicon|Morocco}} [[Wind power in Morocco|Morocco]] || align=right | 64 || align=right | 64 || align=right | 125 || align=right | 125|| align=right | 253
|-
| align=right | 29 ||{{flagicon|Mexico}} [[Wind power in Mexico|Mexico]] || align=right | 2 || align=right | 84 || align=right | 85 || align=right | 85|| align=right | 202
|-
| align=right | 30 || {{flagicon|Hungary}} [[Wind power in Hungary|Hungary]] || align=right | 18 || align=right | 61 || align=right | 65 || align=right | 127 || align=right | 201<ref>[http://www.zoldtech.hu/cikkek/20100105-Bony-25MW-szeleromupark 25 MW teljesítményű szélerőműparkot helyzetek üzembe Bőnyben], 10 January 2010, language: [[Hungarian language|Hungarian]]</ref>
|-
| align=right | 31 || {{flagicon|Czech Republic}} [[Wind power in Czech Republic|Czech Republic]] || align=right | 30 || align=right | 57 || align=right | 116 || align=right | 150 || align=right | 192
|-
| align=right | 32 ||{{flagicon|Bulgaria}} [[Wind power in Bulgaria|Bulgaria]] || align=right | 14 || align=right | 36 || align=right | 57 || align=right | 158 || align=right | 177
|-
| align=right | 33 || {{flagicon|Finland}} [[Wind power in Finland|Finland]] || align=right | 82 || align=right | 86 || align=right | 110 || align=right | 143 || align=right | 147
|-
| align=right | 34 || {{flagicon|Iran}} [[Wind power in Iran|Iran]] || align=right | 32 || align=right | 47 || align=right | 67 || align=right | 82|| align=right | 91
|-
| align=right | 35 || {{flagicon|Ukraine}} [[Wind power in Ukraine|Ukraine]] || align=right | 77 || align=right | 86 || align=right | 89 || align=right | 90
|-
| align=right | || Rest of Europe || align=right | 141 || align=right | 204 || align=right | 233 || align=right | 261
|-
| align=right | || Rest of Americas || align=right | 155 || align=right | 159 || align=right | 184 || align=right | 210
|-
| align=right | || Rest of Africa<br> & Middle East || align=right | 52 || align=right | 52 || align=right | 51 || align=right | 56
|-
| align=right | || Rest of Asia<br> & Oceania || align=right | 27 || align=right | 27 || align=right | 27 || align=right | 36
|-
|style="background-color: #cfb;" |
! style="background-color: #cfb;" | World total (MW)
| align=right style="background-color: #cfb;" | '''59,024''' || align=right style="background-color: #cfb;" | '''74,151''' || align=right style="background-color: #cfb;" | '''93,927''' || align=right style="background-color: #cfb;" | '''121,188''' || align=right style="background-color: #cfb;" | '''157,899''' <ref>http://www.gwec.net/fileadmin/documents/PressReleases/PR_2010/Annex%20stats%20PR%202009.pdf</ref>
|}
<!-- nbsp's needed to fix work wrap problems-->

There are now many thousands of wind turbines operating, with a total [[nameplate capacity]] of 157,899&nbsp;MW of which [[wind power in Europe]] accounts for 48% (2009). World wind generation capacity more than quadrupled between 2000 and 2006, doubling about every three years. 81% of wind power installations are in the US and Europe. The share of the top five countries in terms of new installations fell from 71% in 2004 to 62% in 2006, but climbed to 73% by 2008 as those countries—the United States, Germany, Spain, China, and India—have seen substantial capacity growth in the past two years (see chart).

By 2010, the World Wind Energy Association expects 160&nbsp;GW 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 ninth 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 US]] has added more wind energy to its grid than any other country, with a growth in power capacity of 45% to 16.8&nbsp;GW 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> and surpassing Germany's [[nameplate capacity]] in 2008. [[Wind power in California|California]] was one of the incubators of the modern wind power industry, and led the U.S. in installed capacity for many years; however, by the end of 2006, [[Wind power in Texas|Texas]] became the leading wind power state and [[Wind power in Texas#Installed capacity growth|continues to extend its lead]]. At the end of 2008, the state had 7,116&nbsp;MW installed, which would have ranked it sixth in the world if Texas was a separate country. Iowa and Minnesota each grew to more than 1&nbsp;GW installed by the end of 2007; in 2008 they were joined by Oregon, Washington, and Colorado.<ref>{{cite web
| url= http://awea.org/projects
| title= U.S. Wind Energy Projects
|author= |last= |first= |authorlink= |coauthors=
|date= 2009-02-03 |work= |publisher= [[American Wind Energy Association]]
|pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2009-02-03}}</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 MW 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% (equivalent to 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 the [[Great Plains]] states of Texas, Kansas, and North Dakota 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&nbsp;— 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><ref name=Brown2008>[[Lester R. Brown]]. (2008). [http://www.washingtonpost.com/wp-dyn/content/article/2008/08/29/AR2008082902334.html Want a Better Way to Power Your Car? It's a Breeze]. ''Washington Post''.</ref> In addition, the wind resource over and around the [[Great Lakes]], recoverable with currently available technology, could by itself provide 80% as much power as the U.S. and Canada currently generate from non-renewable resources,<ref name="great_lakes_wind_potential">{{Cite web
|url=http://greengold.org/wind/documents/107.pdf
|title=A Great Potential: The Great Lakes as a Regional Renewable Energy Source
|first=David
|last=Bradley
|date=2004-02-06
|accessdate=2008-10-04
|publisher=
}}</ref> with Michigan's share alone equating to one third of current U.S. electricity demand.<ref name="great_lakes_eyed_for_wind">{{Cite web
|url=http://www.msnbc.msn.com/id/27436310/
|title=Great Lakes eyed for offshore wind farms
|publisher=[[MSNBC]], [[Associated Press]]
|date=2008-10-31
|accessdate=2008-11-14
}}</ref>

[[Wind power in China|China]] had originally set a generating target of 30,000&nbsp;MW by 2020 from renewable energy sources, but reached 22,500 MW by end of 2009 and could easily surpass 30,000&nbsp;MW by end of 2010. Indigenous wind power could generate up to 253,000&nbsp;MW.<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, Issue 7, July 2007. </ref> A Chinese renewable energy law was adopted in November 2004, following the World Wind Energy Conference organized by the Chinese and the World Wind Energy Association. By 2008, wind power was growing faster in China than the government had planned, and indeed faster in percentage terms than in any other large country, having more than doubled each year since 2005. Policymakers doubled their wind power prediction for 2010, after the wind industry reached the original goal of 5&nbsp;GW three years ahead of schedule.<ref name="china_wind_2008">{{Cite web
|url=http://www.guardian.co.uk/environment/2008/jul/25/renewableenergy.alternativeenergy
|title=Energy in China: 'We call it the Three Gorges of the sky. The dam there taps water, we tap wind'
|first=Jonathan
|last=Watts
|publisher=[[The Guardian]]
|date=2008-07-25
|accessdate=2008-10-07}}</ref> Current trends suggest an actual installed capacity near 20&nbsp;GW by 2010, with China shortly thereafter pursuing the United States for the world wind power lead.<ref name="china_wind_2008"/>

[[Wind power in India|India]] ranks 5th in the world with a total wind power capacity of 9,587&nbsp;MW in 2008,<ref name=wwea/> 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> [[Muppandal]] village in [[Tamil Nadu]] state, [[India]], has several wind turbine farms in its vicinity, and is one of the major wind energy harnessing centres in India led by majors like [[Suzlon]], [[Vestas]], [[NEG Micon|Micon]] among others.<ref>{{cite web
| year = 2005
| month =February
| url=http://www.tve.org/ho/doc.cfm?aid=1678&lang=English
| title=Tapping the Wind&nbsp;— 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>

[[Mexico]] recently opened [[La Venta II wind power project]] as an important step in reducing Mexico's consumption of fossil fuels. The 88&nbsp;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&nbsp;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&nbsp;— Centrais Elétricas Brasileiras S. A&nbsp;— 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 100&nbsp;MW 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&nbsp;MW installed by 2010, though their installation trends over the past few years suggest they'll fall well short of their goal.

[[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>. By 2025, Canada will reach its capacity of 55,000 MW of wind energy, or 20% of the country's energy needs.

{| class="wikitable" style="float: left; margin-left: 10px"
|+Annual Wind Power Generation (TW·h) and total electricity consumption(TW·h) for 10 largest countries<ref name="wwea"/><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 BP.com]</ref><ref>[http://web.archive.org/web/20070805092155/http://www.sp.com.cn/sjdl/sjdltj/sjdltj0512.htm 2005 月电力概况] (Chinese)</ref><ref>[http://web.archive.org/web/20071030080545/http://www.sp.com.cn/sjdl/sjdltj/sjdltj0612.htm 2006 月电力概况] (Chinese)</ref><ref>[http://www.eia.doe.gov/emeu/international/electricitygeneration.html Energy Information Administration - International Electricity Generation Data<!-- Bot generated title -->]</ref><ref>[http://tonto.eia.doe.gov/cfapps/ipdbproject/iedindex3.cfm?tid=2&pid=37&aid=2&cid=&syid=2005&eyid=2007&unit=BKWH International Energy Statistics]</ref><ref>[http://www.decc.gov.uk/media/viewfile.ashx?filepath=statistics/publications/dukes/1_20090924085844_e_@@_dukes09.pdf&filetype=4] Digest of United Kingdom energy statistics: 2009, Tables 5.1.2 (total electricity consumption) and 7.4 (installed capacity, electricity generated, capacity factor)</ref>
|-
! rowspan=2 style="background-color: #cfb;" |
! rowspan=2 style="background-color: #cfb;" | Nation
! style="background-color: #cfb;" align=right colspan=4 | 2005
! style="background-color: #cfb;" align=right colspan=4 | 2006
! style="background-color: #cfb;" align=right colspan=4 | 2007
! style="background-color: #cfb;" align=right colspan=4 | 2008
! style="background-color: #cfb;" align=right colspan=4 | 2009
|-
| style="background-color: #cfb;" align=right | Wind<br>power|| style="background-color: #cfb;" align=right | Capacity<br>Factor||style="background-color: #cfb;"|%||style="background-color: #cfb;" align=right |Total<br>Demand||style="background-color: #cfb;" align=right | Wind<br>power|| style="background-color: #cfb;" align=right | Capacity<br>Factor||style="background-color: #cfb;"|%||style="background-color: #cfb;" align=right |Total<br>Demand||style="background-color: #cfb;" align=right | Wind<br>power|| style="background-color: #cfb;" align=right | Capacity<br>Factor||style="background-color: #cfb;"|%|| align=right style="background-color: #cfb;" |Total<br>Demand||style="background-color: #cfb;" align=right | Wind<br>power|| style="background-color: #cfb;" align=right | Capacity<br>Factor||style="background-color: #cfb;"|%|| align=right style="background-color: #cfb;" |Total<br>Demand||style="background-color: #cfb;" align=right | Wind<br>power|| style="background-color: #cfb;" align=right | Capacity<br>Factor||style="background-color: #cfb;"|%|| align=right style="background-color: #cfb;" |Total<br>Demand
|-
| align=right | 1 || {{flagicon|United States}} [[Wind power in the United States|United States]] || align=right |17.8|| align=right |22.2%|| align=right |0.4%|| align=right |4048.9|| align=right | 26.6 || align=right | 26.1% || align=right | 0.7% || align=right | 4058.1 || align=right | 34.5 || align=right | 23.4% || align=right | 0.8% || align=right | 4149.9 || align=right | 52.0 || align=right | 23.5% || align=right | 1.3% || align=right | 4108.6 || align=right | || align=right| || align=right | || align=right |
|-
| align=right | 2 || {{flagicon|Germany}} [[Wind power in Germany|Germany]] || align=right |27.2|| align=right |16.9%|| align=right |5.1%|| align=right |533.7|| align=right | 30.7 || align=right | 17.0% || align=right | 5.4% || align=right | 569.9 || align=right | 38.5 || align=right | 19.7% || align=right | 6.6% || align=right | 584.9 || align=right | 40.4 || align=right| || align=right | 6.6% || align=right| 611.9 || align=right | 37.2 || align=right | || align=right | 6.4% || align=right | 581.3
|-
| align=right | 3 || {{flagicon|Spain}} [[Wind power in Spain|Spain]] || align=right | 20.7 || align=right | 23.5% || align=right | 7.9% || align=right | 260.7 || align=right | 22.9 || align=right | 22.4% || align=right | 8.5% || align=right | 268.8 || align=right | 27.2 || align=right | 20.5% || align=right | 9.8% || align=right | 276.8 || align=right | 31.4 || align=right | 21.7% || align=right | 11.1% || align=right | 282.1|| align=right | 36.6 || align=right| || align=right | 13.7% ||align=right | 267.0
|-
| align=right | 4 || {{flagicon|China}} [[Wind power in China|China]] || align=right | 1.9 || align=right | 17.2% || align=right | 0.1% || align=right | 2474.7 || align=right | 3.7 || align=right | 16.2% || align=right | 0.1% || align=right | 2834.4 || align=right | 5.6 <ref>[http://www.zdxw.com.cn/bgscpd/sdcpfx/200802/t20080225_219745.htm 深度分析产品] (Chinese)</ref> || align=right | 10.6% || align=right | 0.2% || align=right | 3255.9 || align=right | 12.8 <ref>[http://www.gov.cn/gzdt/2009-01/09/content_1200434.htm 全国电力建设与投资结构继续加快调整] (Chinese)</ref> || align=right | 12.0% || align=right | 0.4% || align=right | 3426.8 || align=right | || align=right| || align=right | || align=right |
|-
| align=right | 5 || {{flagicon|India}} [[Wind power in India|India]] || align=right | 6.3 || align=right | 16.2% || align=right | 0.9% || align=right | 679.2 || align=right | 7.6 || align=right | 13.8% || align=right | 1.0% || align=right | 726.7 || align=right | 14.7 || align=right | 21.0% || align=right | 1.9% || align=right | 774.7 || |||| align=right | || align=right| || align=right | || align=right| || align=right | || align=right |
|-
| align=right | 6 || {{flagicon|Italy}} [[Wind power in Italy|Italy]] || align=right | 2.3 || align=right | 15.3% || align=right | 0.7% || align=right | 330.4 || align=right | 3.0 || align=right | 16.1% || align=right | 0.9% || align=right | 337.5 || align=right | 4.0<ref>[http://www.terna.it/LinkClick.aspx?fileticket=QTuCYEB54ek%3d&tabid=720 Dati statistici sull’energia elettrica in Italia nel 2007] (Italian)</ref> || align=right | 16.7% || align=right| 1.2% || align=right | 339.9 || align=right | 4.9||align=right |15.7%|| align=right | 1.4%|| align=right |339.5|| align=right | || align=right| || align=right | || align=right |
|-
| align=right | 7 || {{flagicon|France}} [[Wind power in France|France]] || align=right | 0.9 || align=right | 13.6% || align=right | 0.2% ||align=right | 482.4 || align=right | 2.2 || align=right | 16.0% || align=right | 0.5% || align=right | 478.4 || align=right | 4.0 || align=right | 18.6% || align=right | 0.8% || align=right | 480.3 || align=right | 5.6 || align=right | 18.8% || align=right | 1.1% || align=right | 494.5 || align=right |7.8 || align=right| 20.2%|| align=right |1.6% || align=right |486
|-
| align=right | 8 || {{flagicon|United Kingdom}} [[Wind power in the United Kingdom|United Kingdom]] || align=right | 2.9 || align=right | 24.0% || align=right | 0.8% || align=right | 355.0 || align=right | 4.2 || align=right | 23.2% || align=right | 1.2% || align=right | 352.9 || align=right | 5.3 || align=right | 27.5% || align=right | 1.5% || align=right | 352.0 || align=right | 7.1 || align=right | 30.4% || align=right| 2.0%|| align=right | 350.5 || align=right| || align=right | || align=right |
|-
| align=right | 9 || {{flagicon|Denmark}} [[Wind power in Denmark|Denmark]] || align=right | 6.6 || align=right | 24.0% || align=right | 18.5% || align=right | 35.7 || align=right | 6.1 || align=right | 22.2% || align=right | 16.8% || align=right | 36.4 || align=right | 7.2 || align=right | 26.3% || align=right | 19.7% || align=right | 36.4 || align=right | 6.9 || align=right | 24.9% || align=right | 19.1% || align=right | 36.2 || align=right | || align=right| || align=right | || align=right |
|-
| align=right | 10 || {{flagicon|Portugal}} [[Wind power in Portugal|Portugal]] || align=right | 1.7 || align=right | 19.0% || align=right | 3.6% || align=right | 47.9 || align=right | 2.9 || align=right | 19.3% || align=right | 5.9% || align=right | 49.2 || align=right | 4.0 || align=right | 21.2% || align=right | 8.0% || align=right | 50.1 || align=right | 5.7 || align=right | 22.7% || align=right | 11.3% || align=right | 50.6 || align=right | 7.5 || align=right| || align=right | 15.0% || align=right | 49.9
|-
! style="background-color: #cfb;" |
! style="background-color: #cfb;" | World total (TW·h)
! align=right style="background-color: #cfb;" | 99.5
! align=right style="background-color: #cfb;" | 19.2%
! align=right style="background-color: #cfb;" | 0.6%
! align=right style="background-color: #cfb;" | 15,746<ref>[http://www.eia.doe.gov/emeu/international/electricityconsumption.html International Electricity Consumption]</ref>
! align=right style="background-color: #cfb;" | 124.9
! align=right style="background-color: #cfb;" | 19.2%
! align=right style="background-color: #cfb;" | 0.7%
! align=right style="background-color: #cfb;" | 16,790
! align=right style="background-color: #cfb;" | 173.3
! align=right style="background-color: #cfb;" | 21.1%
! align=right style="background-color: #cfb;" | 0.9%
! align=right style="background-color: #cfb;" | 19,853<ref>[http://www.iea.org/stats/electricitydata.asp?COUNTRY_CODE=29]</ref>
! align=right style="background-color: #cfb;" | 260<ref name="wwea"/>
! align=right style="background-color: #cfb;" | 24.5%<ref name="wwea"/>
! align=right style="background-color: #cfb;" | 1.5%<ref name="wwea"/>
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
|}
<br clear="all"/>

====Power Analysis====
Due to ever increasing sizes of turbines which hit maximum power at lower speeds<ref>http://news.cnet.com/8301-11128_3-10233108-54.html</ref> energy produced has been rising faster than nameplate power capacity. Energy more than doubled between 2006 and 2008 in the table above, yet nameplate capacity (table on left) grew by 63% in the same period.

== Small-scale wind power ==

{{See|Microgeneration}}
[[Image:Urbine221dc.jpg|thumb|right|This wind turbine charges a 12 V [[battery (electricity)|battery]] to run 12 V appliances.]]

'''Small-scale wind power''' is the name given to wind generation systems with the capacity to produce up to 50&nbsp;kW of electrical power.<ref>[http://www.carbontrust.co.uk/technology/technologyaccelerator/small-wind Small-scale wind energy]</ref> Isolated communities, that may otherwise rely on [[Diesel generator|diesel]] generators may use wind turbines to displace diesel fuel consumption. Individuals may purchase these systems to reduce or eliminate their dependence on grid electricity for economic or other reasons, or to reduce their [[carbon footprint]]. Wind turbines have been used for household electricity generation in conjunction with [[Battery (electricity)|battery]] storage over many decades in remote areas.
[[Image:Tassa_5KW_2_ElectronSolarEnergy2.jpg|thumb|right|5 kilowatt vertical axis wind turbine]]
[[Image:Windlahor.jpg|thumb|[http://hr.wikipedia.org/wiki/Vjetrenja%C4%8Da_s_rotiraju%C4%87im_jedrima Windmill with rotating sails]]]
Grid-connected wind turbines may use [[grid energy storage]], displacing purchased energy with local production when available. Off-grid system users can 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 (little is known about the actual wind resource of towns and cities <ref>[http://www.carbontrust.co.uk/News/presscentre/2007/230107_Smallscalwind.htm Windy Cities? New research into the urban wind resource]</ref>), 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.

A new [[Carbon Trust]] study into the potential of small-scale wind energy has found that small wind turbines could provide up to 1.5 terawatt hours (TW·h) per year of electricity (0.4% of total UK electricity consumption), saving 0.6 million tonnes of carbon dioxide (Mt CO<sub>2</sub>) emission savings. This is based on the assumption that 10% of households would install turbines at costs competitive with grid electricity, around 12 pence (US 19 cents) a kW·h.<ref>[http://www.carbontrust.co.uk/News/presscentre/2008/Small-Scale-Wind-Energy.htm The Potential Of Small-Scale Wind Energy]</ref>

Distributed generation from [[renewable resource]]s is increasing as a consequence of the increased awareness of [[climate change]]. The electronic interfaces required to connect renewable generation units with the [[utility]] system can include additional functions, such as the active filtering to enhance the power quality.<ref>[http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/8658/27439/01221533.pdf?arnumber=1221533 Active filtering and load balancing with small wind energy systems]</ref>

== Economics and feasibility ==

=== Relative cost of electricity by generation source ===
{{See also|Relative cost of electricity generated by different sources}}


=== Growth and cost trends ===

Wind and [[hydroelectric]] power generation have negligible fuel costs and relatively low maintenance costs. 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 pence (between US 5 and 6 cents) per kW·h (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 US for coal and natural gas: wind cost was estimated at $55.80 per MW·h, coal at $53.10/MW·h and natural gas at $52.50.<ref>{{cite web
| url= http://www.eia.doe.gov/oiaf/archive/ieo06/special_topics.html
| title= "International Energy Outlook", 2006
| author= |last= |first= |authorlink= |coauthors=
| date= |year= |month= |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]]).

In 2004, wind energy cost a fifth of what it did in the 1980s, and some expected that downward trend to continue as larger multi-megawatt [[Wind turbine|turbines]] were mass-produced.<ref>Helming, Troy (2004) [http://web.archive.org/20071118125045/arizonaenergy.org/News&Events/Uncle%20Sam's%20New%20Year's%20Resolution.htm "Uncle Sam's New Year's Resolution"] ''ArizonaEnergy.org''</ref> However, installed cost averaged €1,300 a kW in 2007,<ref name=gwec2007/> compared to €1,100 a kW 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> Research from a wide variety of sources in various countries shows that support for wind power is consistently 70–80% among the general public.<ref>[http://www.windenergy.org.nz/documents/2005/050825-NZWEA-FactSheet4Tourism.pdf Fact sheet 4: Tourism]</ref>

Global Wind Energy Council (GWEC) figures show that 2007 recorded an increase of installed capacity of 20&nbsp;GW, taking the total installed wind energy capacity to 94&nbsp;GW, up from 74&nbsp;GW in 2006. Despite constraints facing supply chains for wind turbines, the annual market for wind continued to increase at an estimated rate of 37%, 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&nbsp;– 20&nbsp;GW of new capacity in 2007]</ref>

Although the [[wind power industry]] will be impacted by the [[Late 2000s recession|global financial crisis]] in 2009 and 2010, a [[BTM Consult]] five year forecast up to 2013 projects substantial growth. Over the past five years the average growth in new installations has been 27.6 percent each year. In the forecast to 2013 the expected average annual growth rate is 15.7 percent.<ref name=re>[http://www.renewableenergyworld.com/rea/news/article/2009/03/btm-forecasts-340-gw-of-wind-by-2013?src=rss BTM Forecasts 340-GW of Wind Energy by 2013]</ref><ref name=bt>BTM Consult (2009). [http://www.btm.dk/documents/pressrelease.pdf International Wind Energy Development World Market Update 2009]</ref> More than 200&nbsp;GW of new wind power capacity could come on line before the end of 2013. Wind power market penetration is expected to reach 3.35 percent by 2013 and 8 percent by 2018.<ref name=re/><ref name=bt/>

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.

=== Theoretical potential - World ===
[[File:United States Wind Resources and Transmission Lines map.jpg|thumb|right|Map of available wind power for the [[Wind power in the United States|United States]]. Color codes indicate wind power density class.]]
Wind power available in the atmosphere is much greater than current world energy consumption. The most comprehensive study {{as of|2005}}<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]]| date=2005 | accessdate=2006-04-21}}</ref> found the potential of wind power on land and near-shore to be 72&nbsp;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&nbsp;≥ 6.9 m/s at 80 m. The study assumes six 1.5 megawatt, 77 m diameter turbines per square kilometer 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.

===Theoretical potential - UK===

A recent estimate gives the total potential average output for UK for various depth and distance from the coast. The maximum case considered was beyond 200 km from shore and in depths of 100 - 700 m (necessitating [[floating wind turbine]]s) and this gave an average resource of 2,000&nbsp;GWe which is to be compared with the average UK demand of about 40&nbsp;GWe.<ref>http://www.claverton-energy.com/two-terawatts-average-power-output-the-uk-offshore-wind-resource.html</ref>

=== Direct costs ===

Many potential sites for wind farms are far from demand centres, requiring substantially more money to construct new transmission lines and substations. In some regions this is partly because frequent strong winds themselves have discouraged dense human settlement in especially windy areas. The wind which was historically a nuisance is now becoming a valuable resource, but it may be far from large populations which developed in areas more sheltered from wind.

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 depends 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 kW·h.<ref name="Patel"> "Wind and Solar Power Systems&nbsp;— 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 price paid to 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.

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]].{{Citation needed|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 ===
{{Unreferenced 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 can be competitive in more cases, as costs have generally decreased because of technology development and scale enlargement. 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, the expense of transmission lines to connect the wind farms to population centers, 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 ===
[[Image:Wind energy converter5.jpg|thumb||Some of the over 6,000 wind turbines at [[Altamont Pass]], in California, United States. Developed during a period of tax incentives in the 1980s, this wind farm has more turbines than any other in the United States.<ref> [http://www.ilr.tu-berlin.de/WKA/windfarm/altcal.html Wind Plants of California's Altamont Pass]</ref>]]

Wind energy in many jurisdictions receives some financial or other support to encourage its development. Wind energy benefits from [[subsidy|subsidies]] in many jurisdictions, either to increase its attractiveness, or to compensate for subsidies received by other forms of production which have significant negative externalities.

In the United States, wind power receives a tax credit for each kW·h produced; at 1.9 cents per kW·h 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 "[[Renewable Energy Certificates|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 Tariff|feed-in tariffs]]). These feed-in tariffs are typically set well above average electricity prices. The [[Energy Improvement and Extension Act of 2008]] contains extensions of credits for wind, including microturbines.

Secondary market forces also provide incentives for businesses to use wind-generated power, even if there is a [[Renewable Energy Certificates|premium price for the electricity]]. For example, [[Corporate social responsibility|socially responsible manufacturers]] pay utility companies a premium that goes to subsidize and build new wind power infrastructure. Companies use wind-generated power, and in return they can claim that they are making a powerful "green" effort. In the USA the organization Green-e monitors business compliance with these renewable energy credits.<ref>[http://www.green-e.org Green-e.org] Retrieved on 20 May 2009</ref>

=== Full costs and lobbying ===

Commenting on the [[Energy policy of the European Union|EU's 2020 renewable energy target]], Helm (2009) is critical of how the costs of wind power are citied by lobbyists:<ref name=helm>{{cite book
|date=October 2009
|author=Helm, D. D. Helm and C. Hepburn (eds)
|title=EU climate-change policy-a critique. From: "The Economics and Politics of Climate Change"
|publisher=Oxford University Press
|url=http://www.dieterhelm.co.uk/publications/SS_EU_CC_Critique.pdf
|accessdate=September 6, 2009}}</ref>

<blockquote>For those with an economic interest in capturing as much of the climate-change [[pork barrel]] as possible, there are two ways of presenting the costs [of wind power] in a favourable light: first, define the cost base as narrowly as possible; and, second, assume that the costs will fall over time with R&D and large-scale deployment. And, for good measure, when considering the alternatives, go for a wider cost base (for example, focusing on the full fuel-cycle costs of nuclear and coal-mining for coal generation) and assume that these technologies are mature, and even that costs might rise (for example, invoking the highly questionable ‘peak oil hypothesis’).</blockquote>

A [[House of Lords]] [[Select Committee (Westminster System)|Select Committee]] report (2008) on renewable energy in the [[UK]] says:<ref>{{cite web
|date=November 12, 2008
|title=Chapter 7: Recommendations and Conclusions. In: Economic Affairs – Fourth Report, Session 2007-2008. The Economics of Renewable Energy
|author=House of Lords Economic Affairs Select Committee
|publisher=UK Parliament website
|url=http://www.publications.parliament.uk/pa/ld200708/ldselect/ldeconaf/195/19510.htm
|accessdate=September 6, 2009}}</ref>

<blockquote>We have a particular concern over the prospective role of wind generated and other intermittent sources of electricity in the UK, in the absence of a break-through in electricity storage technology or the integration of the UK grid with that of continental Europe. Wind generation offers the most readily available short-term enhancement in renewable electricity and its base cost is relatively cheap. Yet the evidence presented to us implies that the full costs of wind generation (allowing for intermittency, back-up conventional plant and grid connection), although declining over time, remain significantly higher than those of conventional or nuclear generation (even before allowing for support costs and the environmental impacts of wind farms). Furthermore, the evidence suggests that the capacity credit of wind power (its probable power output at the time of need) is very low; so it cannot be relied upon to meet peak demand. Thus wind generation needs to be viewed largely as additional capacity to that which will need to be provided, in any event, by more reliable means</blockquote>

Helm (2009) says that wind's problem of intermittent supply will probably lead to another [[dash for gas|dash-for-gas]] or dash-for-coal in Europe, possibly with a negative impact on [[energy security]].<ref name=helm />

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

[[File:Wb deichh drei kuhs.jpg|thumb|right|350px|Livestock ignore wind turbines,<ref name="livestock_ignore">{{Cite web |url=http://www.uintacountyherald.com/V2_news_articles.php?heading=0&page=72&story_id=1299 |title=Capturing the wind
|first=Erin
|last=Buller
|date=2008-07-11
|publisher=Uinta County Herald
|accessdate=2008-12-04
}}"The animals don’t care at all. We find cows and antelope napping in the shade of the turbines." - Mike Cadieux, site manager, Wyoming Wind Farm</ref> and continue to graze as they did before wind turbines were installed.]]
Compared to the environmental effects of traditional energy sources, the environmental effects of wind power are relatively minor. Wind power consumes no fuel, and emits no [[air pollution]], unlike fossil fuel power sources. The energy consumed to manufacture and transport the materials used to build a wind power plant is equal to the new energy produced by the plant within a few months of operation{{Citation needed|date=February 2010}}. Garrett Gross, a scientist from [[University of Missouri–Kansas City|UMKC]] in Kansas City, Missouri states, "The impact made on the environment is very little when compared to what is gained." The initial carbon dioxide emission from energy used in the installation is "paid back" within about 9 months of operation for offshore turbines{{Citation needed|date=February 2010}}.

Danger to birds and bats has been a concern in some locations. However, studies show that the number of birds killed by wind turbines is very low, compared to the number of those that die as a result of certain other ways of generating electricity and especially of the environmental impacts of using [[fossil fuels|non-clean power sources]]. Fossil fuel generation kills around twenty times as many birds per unit of energy produced than wind-farms.<ref>{{cite doi|10.1016/j.enpol.2009.02.011}}</ref> Bat species appear to be at risk during key movement periods. 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&nbsp;km or more from shore do not interact with bat populations. While a [[wind farm]] may cover a large area of land, many land uses such as agriculture are compatible, with only small areas of turbine foundations and infrastructure made unavailable for use.

Aesthetics have also been an issue. In the USA, the Massachusetts [[Cape Wind]] project was delayed for years mainly because of aesthetic concerns. In the UK, repeated opinion surveys have shown that more than 70% of people either like, or do not mind, the visual impact. According to a town councillor in [[Ardrossan]], Scotland, the overwhelming majority of locals believe that the [[Ardrossan Wind Farm]] has enhanced the area, saying that the turbines are impressive looking and bring a calming effect to the town.<ref>[http://www.guardian.co.uk/commentisfree/2008/aug/12/windpower.alternativeenergy Wind farms are not only beautiful, they're absolutely necessary]</ref>

Finally, [[Environmental_effects_of_wind_power#Effects_of_noise|noise]] has also been an important disadvantage. With careful implanting of the wind turbines, along with use of noise reducing-modifications for the wind turbines however, these issues can be easily adressed.

== See also ==
{{portal|Energy}}
{{Portalpar|Sustainable development|Sustainable development.svg}}
{{commons}}
*[[Renewable energy]]
* [[Distributed Energy Resources]]
* [[Electricity generation]]
* [[Energy development]]
* [[Floating wind turbine]]
* [[Green energy]]
* [[Green tax shift]]
* [[Grid energy storage]]
* [[Intermittent energy source]]
* [[List of countries by renewable electricity production]]
* [[List of wind farms]]
* [[List of offshore wind farms]]
* [[List of wind turbine manufacturers]]
* [[Merchant Wind Power]]
* [[Pickens plan]]
* [[Vertical axis wind turbine]]
* [[Wind farm]]
* [[Wind profiler]]
* [[Wind-Diesel Hybrid Power Systems|Wind-Diesel]]
* [[World energy resources and consumption]]
* [[:Category:Wind power by country]]

== References ==

{{reflist|3}}

== External links ==
<!-- Discuss new proposed links on talk page first. -->
<!-- See [[Wikipedia:External links]] and [[Wikipedia:Spam]] for details -->
*[http://solarpowernotes.com/renewable-energy/wind-power/how-wind-power-works.html How electricity is produced using Wind Energy]
* [http://www.gizmag.com/the-first-race-for-wind-powered-vehicles/9953/ Wind-powered vehicles].
* [http://www.ted.com/index.php/talks/saul_griffith_on_kites_as_the_future_of_renewable_energy.html Inventing a super-kite to tap the energy of high-altitude wind, Feb 2009 ([[TED conference]] video), 5:25 min.]
===U.S.===
*[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
*[http://www.reuters.com/article/idUSN2211296320100126?type=marketsNews US wind power capacity up in '09]

{{Wind power|state=expanded}}
{{Wind power by country}}
{{Electricity generation|state=collapsed}}
{{Application of wind energy}}

{{DEFAULTSORT:Wind Power}}
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