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[[Image:Windenergy.jpg|thumb|This three-bladed [[wind turbine]] is the most common modern design because it minimizes forces related to fatigue.]]
'''Wind power''' is the conversion of wind energy into a useful form, such as electricity, using [[wind turbine]]s. At the end of 2008, worldwide [[nameplate capacity]] of wind-powered generators was 120.8 [[gigawatt]]s.<ref name="wwea">{{cite web
| author = World Wind Energy Association
| title = 120 Gigawatt of wind turbines globally contribute to secure electricity generation
| work = Press release
| date = 06-Feb-2009
| url = http://www.wwindea.org/home/index.php?option=com_content&task=view&id=223&Itemid=40
| accessdate = 06-Feb-2009}}
</ref>

Wind energy has historically been used directly to propel [[sailing ship]]s or converted into mechanical energy for pumping water or grinding grain, but the principal application of wind power today is the generation of electricity. Large scale [[wind farms]] are typically connected to the local [[electric power transmission]] network, with smaller turbines being 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 favoured by many [[environmentalist]]s as an alternative to [[fossil fuel]]s, as it is plentiful, [[renewable energy|renewable]], widely distributed, clean, and produces lower [[greenhouse gas emissions]], although the construction of wind farms is not universally welcomed due to their visual impact and other [[Environmental effects of wind power|effects on the environment]]. The [[Intermittent power sources|intermittency]] of wind seldom creates problems when using wind power to supply a low proportion of total demand. Where wind is to be used for a moderate fraction of demand, additional costs for compensation of intermittency are considered to be modest.<ref>{{cite web
| url= http://www.ieawind.org/AnnexXXV/Meetings/Oklahoma/IEA%20SysOp%20GWPC2006%20paper_final.pdf
| title= "Design and Operation of Power Systems with Large Amounts of Wind Power", IEA Wind Summary Paper
| author= Hannele Holttinen, ''et al.''
| date= September 2006 |format= [[PDF]] |work= |publisher= Global Wind Power Conference September 18-21, 2006, Adelaide, Australia
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= }} </ref>

{{renewable energy sources}}

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

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. The use of wind to provide mechanical power came somewhat later in antiquity.

The [[Babylonia]]n emperor [[Hammurabi]] planned to use wind power for his ambitious [[irrigation]] project in the 17th century BC<ref>{{citation|last=Sathyajith|first=Mathew|title=Wind Energy: Fundamentals, Resource Analysis and Economics|publisher=[[Springer Science+Business Media|Springer Berlin Heidelberg]]|year=2006|isbn=978-3-540-30905-5|pages=1–9}}</ref>. The ancient [[Sinhala people|Sinhalese]] utilized the monsoon winds to power furnaces as early as 300 BC evidence has been found in cities such as [[Anuradhapura]] and in other cities around [[Sri Lanka]]<ref>G. Juleff, "An ancient wind powered iron smelting technology in Sri Lanka", Nature 379 (3), 60-63 (January, 1996).</ref> The furnaces were constructed on the path of the monsoon winds to exploit the wind power, to bring the temperatures inside up to 1100-1200 Celsius. An early historical reference to a rudimentary windmill was used to power an [[Organ (music)|organ]] in the 1st century AD.<ref>A.G. Drachmann, "Heron's Windmill", ''Centaurus'', 7 (1961), pp. 145-151</ref> The first practical [[windmill]]s were later built in [[Sistan]], [[Afghanistan]], from the 7th century. These were vertical-[[axle]] windmills, which had long vertical [[driveshaft]]s with rectangle shaped [[blade]]s.<ref>[[Ahmad Y Hassan]], [[Donald Routledge Hill]] (1986). ''Islamic Technology: An illustrated history'', p. 54. [[Cambridge University Press]]. ISBN 0-521-42239-6.</ref> Made of six to twelve [[Windmill sail|sail]]s covered in [[reed mat]]ting or [[cloth]] material, these windmills were used to grind [[maize|corn]] and draw up [[water]], and were used in the [[gristmill]]ing and [[Sugar refinery|sugarcane industries]].<ref>[[Donald Routledge Hill]], "Mechanical Engineering in the Medieval Near East", ''Scientific American'', May 1991, p. 64-69. ([[cf.]] [[Donald Routledge Hill]], [http://home.swipnet.se/islam/articles/HistoryofSciences.htm Mechanical Engineering])</ref> Horizontal-axle windmills were later used extensively in Northwestern [[Europe]] to grind flour beginning in the 1180s, and many [[Netherlands|Dutch]] windmills still exist.<ref>Dietrich Lohrmann, "Von der östlichen zur westlichen Windmühle", ''Archiv für Kulturgeschichte'', Vol. 77, Issue 1 (1995), pp.1-30 (18ff.)</ref>

In the [[United States]], the development of the "water-pumping windmill" was the major factor in allowing the farming and ranching of vast areas of North America, which were otherwise devoid of readily accessible water. They contributed to the expansion of [[rail transport]] systems throughout the world, by pumping water from [[water well|well]]s 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.

The first modern wind turbines were built in the early 1980s, although more efficient designs are still being developed.

== Wind energy ==
{{details more|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 100&nbsp;meter diameter circle facing directly into the wind. Total energy for the year through that circle was 15.4&nbsp;[[gigawatt-hour]]s.]]

The Earth is unevenly heated by the sun resulting in the [[Geographic pole|pole]]s receiving less energy from the sun than the [[equator]] does. Also, the dry land heats up (and cools down) more quickly than the seas do. The differential heating drives a global [[convection#Atmospheric convection|atmospheric convection]] system reaching from the Earth's surface to the [[stratosphere]] which acts as a virtual ceiling. Most of the energy stored in these wind movements can be found at high altitudes where continuous wind speeds of over 160&nbsp;km/h (100 mph) 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|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 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 [[Rayleigh distribution|Rayleigh]] model closely mirrors the actual distribution of hourly wind speeds at many locations.

Because so much power is generated by higher windspeed, much of the energy comes in short bursts. The 2002 Lee Ranch sample is telling;<ref>http://www.sandia.gov/wind/other/LeeRanchData-2002.pdf 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 to link widely distributed wind farms since the average variability is much less; the use of hydro storage and demand-side energy 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>

Wind power density (WPD) is a calculation relating to the effective force of the wind at a particular location, frequently expressed in terms of the elevation above ground level over a period of time. It further takes into account wind velocity and mass. Color coded maps are frequently prepared for a particular area described, for example, as "Mean Annual Power Density at 50 Meters." The results of the above calculation are used in an index developed by the National Renewable Energy Labs and referred to as "NREL CLASS." The larger the WPD calculation, the higher it is rated by class.

== Electricity Generation ==
=== Grid management system ===
[[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]]

Electricity generated by a wind farm is normally fed into the national [[electric power transmission]] network. Individual turbines are interconnected with a medium voltage (usually 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 transmission system. The surplus power produced by domestic microgenerators can, in some jurisdictions, be fed back into the network and sold back to the utility company, producing a retail credit for the consumer 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>

[[Induction generator]]s, often used for wind power projects, 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 (however properly matched power factor correction capacitors along with electronic control of [[Electrical resonance|resonance]] can support induction generation without grid). [[Doubly-fed electric machine|Doubly-fed machines]], or wind turbines with solid-state converters between the turbine generator and the collector system, have generally more desirable properties for grid interconnection. Transmission systems operators will supply a wind farm developer with a ''grid code'' to specify the requirements for interconnection to the transmission grid. This will include [[power factor]], constancy of [[Utility frequency|frequency]] and dynamic behaviour of the wind farm turbines during a system fault.<ref 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 2009-2013 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.awea.org/faq/basicen.html How Does A Wind Turbine's Energy Production Differ from Its Power Production?] </ref><ref> [http://www.ceere.org/rerl/about_wind/RERL_Fact_Sheet_2a_Capacity_Factor.pdf Wind Power: Capacity Factor, Intermittency, and what happens when the wind doesn’t blow?] retrieved 24 January 2008.</ref> For example, a 1 megawatt turbine with a capacity factor of 35% will not produce 8,760 megawatt-hours in a year (1x24x365), but only 1x0.35x24x365&nbsp;=&nbsp;3,066&nbsp;MWh, averaging to 0.35 MW. Online data is available for some locations and the capacity factor can be calculated from the yearly output.<ref>[http://view2.fatspaniel.net/FST/Portal/LighthouseElectrical/maritime/HostedAdminView.html Massachusetts Maritime Academy&nbsp;— Bourne, Mass] This 660 kW wind turbine has a capacity factor of about 19%.</ref><ref>[http://www.ieso.ca/imoweb/marketdata/windpower.asp Wind Power in Ontario] These wind farms have capacity factors of about 28 to 35%.</ref><!--Note to editors, please add links from other geographical regions.-->

Unlike fueled generating plants, the capacity factor is limited by the inherent properties of wind. Capacity factors of other types of power plant are based mostly on fuel cost, with a small amount of downtime for maintenance. [[Nuclear Power|Nuclear plants]] have low incremental fuel cost, and so are run at full output and achieve a 90% capacity factor.<ref>{{cite web
| author = Nuclear Energy Institute
| title = Nuclear Facts
| url = http://www.nei.org/doc.asp?catnum=2&catid=106
| accessdate = 2006-07-23 }}</ref> Plants with higher fuel cost are throttled back to [[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>

== Intermittency and penetration limits ==
{{main|Intermittent Power Sources}}
[[Image:WindMills.jpg|right|thumb|[[Wind turbine]]s on [[Inner Mongolia]]n grassland]]
[[Image:Pumpstor racoon mtn.jpg|thumb|right| Diagram of the TVA pumped storage facility at [[Raccoon Mountain Pumped-Storage Plant]]]]
Electricity generated from wind power can be highly variable at several different timescales: from hour to hour, daily, and seasonally. Annual variation also exists, but is not as significant. Because instantaneous electrical generation and consumption must remain in balance to maintain grid stability, this variability can present substantial challenges to incorporating large amounts of wind power into a grid system. [[Intermittent power sources|Intermittency]] and the non-[[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.

A series of detailed modelling studies which looked at the Europe wide adoption of renewable energy and interlinking power grids using HVDC cables, indicates that the entire power usage could come from renewables, with 70% total energy from wind at the same sort of costs or lower than at present. Intermittency would be dealt with, according to this model, by a combination of geographic dispersion to de-link weather system effects, and the ability of HVDC to shift power from windy areas to non-windy areas.<ref 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><ref>[http://www.iset.uni-kassel.de/abt/w3-w/projekte/Risoe200305.pdf Effects of Large-Scale Distribution of Wind Energy in and Around Europe]</ref>

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

In particular geographic regions, peak wind speeds may not coincide with peak demand for electrical power. In [[California]] and [[Texas]], for example, hot days in summer may have low wind speed and high electrical demand due to [[air conditioning]]. 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. Geothermal heat pumps also allow renewable electricity from wind to displace [[natural gas]] and [[heating oil]] for [[central heating]] during winter, when winds tend to be stronger in many areas. Another option is to interconnect widely dispersed geographic areas with a relatively cheap and efficient 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>Wind Energy Bumps Into Power Grid’s Limits.Published: August 26, 2008.http://www.nytimes.com/2008/08/27/business/27grid.html?_r=2&oref=slogin&oref=slogin</ref>. Total annual US power consumption in 2006 was 4 thousand billion kilowatt hours. <ref>http://www.eia.doe.gov/cneaf/electricity/epa/figes1.html</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. ie $3 billion p.a. Dividing by total power used gives an increased unit cost of around $3,000,000,000 x 100 / 4,000 x 1 exp9 = 0.075 cent / kWh.

According to a 2007 Stanford University study published in the Journal of Applied Meteorology and Climatology, interconnecting ten or more wind farms allows 33 to 47% of the total energy produced to be used as reliable, [[baseload power|baseload electric power]], as long as minimum criteria are met for wind speed and turbine height.<ref name="connecting_wind_farms"/><ref name=Archer2007/>

In the [[United Kingdom|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>[http://www.theiet.org/factfiles/energy/env-intro.cfm?type=pdf The Environmental Effects of Electricity Generation]</ref><ref>{{cite web |url= http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V2W-4HPD59N-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=bf0326d6c9fba5f5d1fc6c86b25eb2d8
| title= Characteristics of the UK wind resource: Long-term patterns and relationship to electricity demand
| author=Graham Sinden
| publisher=Environmental Change Institute, Oxford University Centre for the Environment
| date=2005-12-01
}}</ref> [[Solar power]] tends to be complementary to wind.<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 solar and wind generation [http://view2.fatspaniel.net/PV2Web/graph?series-legend_2=Solar+Panels+%20x%20+20&&series-color_2=0x009933&series-mult_2.1=20&series-item_2.1=GenerationEnergy&series-eid_2.1=67668&series-dev_1.2=KYZ&value-axis-title=kWh&max-value=5000&series-dev_1.1=KYZ&series-gw_1.2=1141&series-gw_1.1=1141&bin-type=cum&series-legend_1=Wind+Turbine&chart-height=375&bar-gap=0.10&series-color_1=0x003399&bin-duration=86400000&start-date=last-7-days&num-ticks=1&date-format=MM/dd&chart-bgcolor=0xFFFFFF&series-chan_1.2=CumEnergy2&chart-width=750&series-chan_1.1=CumEnergy&min-value=0&tick-unit=day&pattern=00.0&chart-type=bar&series-mult_1.2=-1&chart-title=Massachusetts+Maritime+Academy+Renewable+Energy+Last+Week&scale=kilowatt-hours last week] and [http://view2.fatspaniel.net/PV2Web/graph?series-legend_2=Solar+Panels+%20x%20+20&&series-color_2=0x009933&series-mult_2.1=20&series-item_2.1=GenerationEnergy&series-eid_2.1=67668&series-dev_1.2=KYZ&value-axis-title=kWh&max-value=5000&series-dev_1.1=KYZ&series-gw_1.2=1141&series-gw_1.1=1141&bin-type=cum&series-legend_1=Wind+Turbine&chart-height=375&bar-gap=0.10&series-color_1=0x003399&bin-duration=86400000&start-date=last-30-days&num-ticks=2&date-format=MM/dd&chart-bgcolor=0xFFFFFF&series-chan_1.2=CumEnergy2&chart-width=750&series-chan_1.1=CumEnergy&min-value=0&tick-unit=day&pattern=00.0&chart-type=bar&series-mult_1.2=-1&chart-title=Massachusetts+Maritime+Academy+Renewable+Energy+Last+Month&scale=kilowatt-hours last month].</ref> 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>{{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"/> The cost of keeping a fossil fuel power station idle is in fact quite low, since the main cost of running a power station is the fuel (see [[spark spread]] and [[dark spread]]).{{Fact|date=August 2008}}

=== Penetration ===

Wind energy "penetration" refers to the fraction of energy produced by wind compared with the total available generation capacity. There is no generally accepted "maximum" level of wind penetration. The limit for a particular grid will depend on the existing generating plants, pricing mechanisms, capacity for storage or demand management, and other factors. An interconnected electricity grid will already include reserve generating and transmission capacity to allow for equipment failures; this reserve capacity can also serve to regulate for the varying power generation by wind plants. Studies have indicated that 20% of the total electrical energy consumption may be incorporated with minimal difficulty.<ref>{{cite web| url=http://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.

However In evidence to the House of Lords Economic Affairs Select Committee, the UK System Operator, National Grid 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."<ref>{{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>

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

Denmark has active plans to increase the percentage of power generated to over 50%.<ref name="Bach_2008">{{Cite web
|first=Paul Fredrick
|last=Bach
|title=EcoGrid.dk preparing for 50% wind electricity in 2025
|url=http://energydiscussiongroup.wikispaces.com/2008+Conference
|publisher=Claverton Conference
|month=April
|year=2008
|location=[[Bath, Somerset]]
|accessdate=2008-11-10
}}<!-- We need to upgrade this source as it does not appear to meet the Wikipedia standard for published reliability --></ref>

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

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

A recent report by Sinclair Merz<ref>Sinclair Merz ''Growth Scenarios for UK Renewables Generation and Implications for Future Developments and Operation of Electricity Networks'' BERR Publication URN 08/1021 June 2008</ref> saw no difficulty in accommodating 50% of total power delivered in the UK at modest cost increases.

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

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

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

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

Studies in the UK have shown that if onshore turbines are placed in a straight line then an increased risk of aerodynamic modulation can occur which can result in noise nuisance to nearby residents.

== Offshore wind farms ==
[[Image:Windmills D1-D4 - Thornton Bank.jpg|thumb|150px|[[REpower]] 5MW wind turbines D4 (nearest) to D1 on the [[Thorntonbank Wind Farm|Thornton Bank]]]]{{main|List of offshore wind farms}}
{{As of|2008}}, Europe leads the world in development of offshore wind power, due to strong wind resources and shallow water in the [[North Sea]] and the [[Baltic Sea]], and limitations on suitable locations on land due to dense populations and existing developments. [[Wind power in Denmark|Denmark]] installed the first offshore wind farms, and for years was the world leader in offshore wind power until the [[Wind power in the United Kingdom|United Kingdom]] gained the lead in October, 2008 with 590 [[megawatt|MW]] of [[nameplate capacity]] installed.<ref name="UK_overtakes_Denmark">{{Cite web
|url=http://www.guardian.co.uk/environment/2008/oct/21/windpower-renewableenergy1
|title=UK overtakes Denmark as world's biggest offshore wind generator
|first=Alok
|last=Jha
|publisher=[[guardian.co.uk]]
|date=2008-10-21
|accessdate=2008-11-12
}}</ref> The United Kingdom planned to build much more extensive offshore wind farms by 2020.<ref name="UK_wind_farms_2008">{{Cite web
|url=http://www.guardian.co.uk/environment/2008/oct/19/renewable-energy-greenhouse-carbon-emissions
|title=UK wind farm plans on brink of failure
|accessdate=2008-11-10
|date=2008-08-19
|publisher=[[guardian.co.uk]]
|first=John
|last=Vidal
}}</ref> Other large markets for wind power, including the [[Wind power in the United States|United States]] and [[Wind power in China|China]] focused first on developing their on-land wind resources where construction costs are lower (such as in the [[Great Plains]] of the U.S., and the similarly wind-swept steppes of [[Xinjiang]] and [[Inner Mongolia]] in China), but population centers along coastlines in many parts of the world are close to offshore wind resources, which would reduce transmission costs.

On 21 December 2007, Q7 (later renamed as [[Princess Amalia Wind Farm]]) exported first power to the Dutch grid, which was a milestone for the offshore wind industry. The 120MW offshore wind farm with a construction budget of €383 million was the first to be financed by a nonrecourse loan (project finance). The project comprises 60 [[Vestas]] V80-2MW wind turbines. Each turbine's tower rests on a monopile foundation to a depth of between 18-23 meters at a distance of about 23&nbsp;km off the Dutch coast.

Transporting large wind turbine components (tower sections, nacelles, and blades) is much easier over water than on land, because ships and barges can handle large loads more easily than trucks/lorries or trains. On land, [[large goods vehicle]]s must negotiate bends on roadways, which fixes the maximum length of a wind turbine blade that can move from point to point on the road network; no such limitation exists for transport on open water. Construction and maintenance costs per wind turbine are higher for offshore wind farms, motivating operators to reduce the number of wind turbines for a given total power by installing the largest available units. An example is Belgium's [[Thorntonbank Wind Farm]] with construction underway in 2008, featuring 5MW wind turbines from [[REpower]], which were among the largest wind turbines in the world at the time.

== Utilization of wind power ==
{{further|[[:Category:Wind power by country]]}}
<blockquote>
''Also see [[Installed wind power capacity]] for prior years''
</blockquote>
<!-- Please do not change the order of countries until end of 2008 figures are available in March 2009. Please supply a reference for any changes. -->
{| class="wikitable" style="float: right; margin-left: 10px"
! colspan="6" align=center style="background-color: #cfb;" | Installed windpower capacity (MW)<ref name="GWEC">{{cite web | url= http://www.gwec.net/uploads/media/07-02_PR_Global_Statistics_2006.pdf | title=Global Wind Energy Council (GWEC) statistics |format= [[PDF]] }}</ref><ref name="EWEA">{{cite web | url= http://www.ewea.org/fileadmin/ewea_documents/documents/publications/statistics/070129_Wind_map_2006.pdf | title=European Wind Energy Association (EWEA) statistics |format= [[PDF]] }}</ref><ref>[http://www.gwec.net/uploads/media/chartes08_EN_UPD_01.pdf Global installed wind power capacity (MW)] Global Wind Energy Council 6.2.2008</ref><ref> {{cite web | url= http://www.awea.org/newsroom/releases/wind_energy_growth2008_27Jan09.html | title= Wind Energy grows by record 8,300 MW in 2008}} </ref><ref>{{cite web | url=http://www.gwec.net/fileadmin/documents/PressReleases/PR_stats_annex_table_2nd_feb_final_final.pdf | title = GLOBAL INSTALLED WIND POWER CAPACITY (MW) – Regional Distribution}}</ref><ref name="EWEC">{{cite web | url= http://www.ewec2009.info/fileadmin/ewec2009_files/documents/Media_room/European_Wind_Map_2008.pdf | title=Wind power installed in Europe by end of 2008 (cumulative) |format= [[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
|-
| align=right | 1 || [[Wind power in the United States|United States]] || align=right | 9,149 || align=right | 11,603 || align=right | 16,818 || align=right | 25,170
|-
| align=right | 2 || [[Wind power in Germany|Germany]] || align=right | 18,415|| align=right | 20,622 || align=right | 22,247 || align=right | 23,903
|-
| align=right | 3 || [[Wind power in Spain|Spain]] || align=right | 10,028 || align=right | 11,615 || align=right | 15,145 || align=right | 16,754
|-
| align=right | 4 || [[Wind power in China|China]] || align=right | 1,260 || align=right | 2,604 || align=right | 6,050|| align=right | 12,210
|-
| align=right | 5 || [[Wind power in India|India]] || align=right | 4,430 || align=right | 6,270 || align=right | 8,000 || align=right | 9,645
|-
| align=right | 6 || [[Wind power in Italy|Italy]] || align=right | 1,718 || align=right | 2,123 || align=right | 2,726 || align=right | 3,736
|-
| align=right | 7 || [[Wind power in France|France]] || align=right | 757 || align=right | 1,567 || align=right | 2,454 || align=right | 3,404
|-
| align=right | 8 || [[Wind power in the United Kingdom|United Kingdom]] || align=right | 1,332 || align=right | 1,963 || align=right | 2,389 || align=right | 3,241
|-
| align=right | 9 || [[Wind power in Denmark|Denmark<br>(& Faeroe Islands)]] || align=right | 3,136 || align=right | 3,140 || align=right |3,129 || align=right | 3,180
|-
| align=right | 10 || [[Wind power in Portugal|Portugal]] || align=right | 1,022 || align=right | 1,716 || align=right | 2,150 || align=right | 2,862
|-
| align=right | 11 || [[Wind power in Canada|Canada]] || align=right | 683 || align=right | 1,459 || align=right | 1,856 || align=right | 2,369
|-
| align=right | 12 || [[Wind power in the Netherlands|Netherlands]] || align=right | 1,219 || align=right | 1,560 || align=right |1,747 || align=right | 2,225
|-
| align=right | 13 || [[Wind power in Japan|Japan]] || align=right | 1,061 || align=right | 1,394 || align=right | 1,538 || align=right | 1,880
|-
| align=right | 14 || [[Wind power in Australia|Australia]] || align=right | 708 || align=right | 817 || align=right |824 || align=right | 1,306
|-
| align=right | 15 || [[Wind power in Sweden|Sweden]] || align=right | 510 || align=right | 572 || align=right |788 || align=right | 1,021
|-
| align=right | 16 || [[Wind power in Ireland|Ireland]] || align=right | 496 || align=right | 745 || align=right | 805 || align=right | 1,002
|-
| align=right | 17 || [[Wind power in Austria|Austria]] || align=right | 819 || align=right | 965 || align=right |982 || align=right | 995
|-
| align=right | 18 || [[Wind power in Greece|Greece]] || align=right | 573 || align=right | 746 || align=right | 871 || align=right | 985
|-
| align=right | 19 || [[Wind power in Poland|Poland]] || align=right | 83 || align=right | 153 || align=right | 276 || align=right | 472
|-
| align=right | 20 || [[Wind power in Turkey|Turkey]] || align=right | 20 || align=right | 51 || align=right |146 || align=right | 433
|-
| align=right | 21 || [[Wind power in Norway|Norway]] || align=right | 267 || align=right | 314 || align=right |333 || align=right | 428
|-
| align=right | 22 || [[Wind power in Belgium|Belgium]] || align=right | 167 || align=right | 193 || align=right |287 || align=right | 382
|-
| align=right | 23 || [[Wind power in Egypt|Egypt]] || align=right | 145 || align=right | 230 || align=right | 310 || align=right | 365
|-
| align=right | 24 || [[Wind power in Taiwan|Taiwan]] || align=right | 104 || align=right | 188 || align=right |282 || align=right | 358
|-
| align=right | 25 || [[Wind power in Brazil|Brazil]] || align=right | 29 || align=right | 237 || align=right |247 || align=right | 341
|-
| align=right | 26 || [[Wind power in New Zealand|New Zealand]] || align=right | 169 || align=right | 171 || align=right | 322 || align=right | 326
|-
| align=right | 27 || [[Wind power in South Korea|South Korea]] || align=right | 98 || align=right | 173 || align=right |191 || align=right | 236
|-
| align=right | 28 || [[Wind power in Bulgaria|Bulgaria]] || align=right | 6 || align=right | 20 || align=right |35 || align=right | 158
|-
| align=right | 29 || [[Wind power in Czech Republic|Czech Republic]] || align=right | 28 || align=right | 50 || align=right |116 || align=right | 150
|-
| align=right | 30 || [[Wind power in Finland|Finland]] || align=right | 82 || align=right | 86 || align=right | 110 || align=right | 143
|-
| align=right | 31 || [[Wind power in Morocco|Morocco]] || align=right | 64 || align=right | 124 || align=right |114 || align=right | 134
|-
| align=right | 32 || [[Wind power in Hungary|Hungary]] || align=right | 18 || align=right | 61 || align=right |65 || align=right | 127
|-
| align=right | 33 || [[Wind power in Ukraine|Ukraine]] || align=right | 77 || align=right | 86 || align=right |89 || align=right | 90
|-
| align=right | 34 || [[Wind power in Mexico|Mexico]] || align=right | 3 || align=right | 88 || align=right |87 || align=right | 85
|-
| align=right | 35 || [[Wind power in Iran|Iran]] || align=right | 23 || align=right | 48 || align=right |66 || align=right | 85
|-
| align=right | 36 || [[Wind power in Costa Rica|Costa Rica]] || align=right | 71 || align=right | 74 || align=right | 74 || align=right | 70
|-
| align=right | || Rest of Europe || align=right | 129 || align=right | 163 || align=right | ||
|-
| align=right | || Rest of Americas || align=right | 109 || align=right | 109 || align=right | ||
|-
| align=right | || Rest of Asia || align=right | 38 || align=right | 38 || align=right | ||
|-
| align=right | || Rest of Africa<br> & Middle East || align=right | 31 || align=right | 31 || align=right | ||
|-
| align=right | || Rest of Oceania || align=right | 12 || align=right | 12 || align=right | ||
|-
|style="background-color: #cfb;" |
! style="background-color: #cfb;" | World total (MW)
| align=right style="background-color: #cfb;" | '''59,091''' || align=right style="background-color: #cfb;" | '''74,223''' || align=right style="background-color: #cfb;" | '''93,849''' || align=right style="background-color: #cfb;" | '''120,791'''
|}
<!-- nbsp's needed to fix work wrap problems--><br>
The&nbsp;modern&nbsp;[[wind power industry]] began in 1979 with the serial production of wind turbines by Danish manufacturers Kuriant, Vestas, Nordtank, and Bonus. These early turbines were small by today's standards, with capacities of 20 to 30 kW each. Since then, they have increased greatly in size, while wind turbine production has expanded to many countries all over the world.

There are now many thousands of wind turbines operating, with a total [[nameplate capacity]] of 120,791&nbsp;MW of which [[wind power in Europe]] accounts for 55% (2008). Wind power is the fastest growing energy source.<ref>{{Citation | date =Jan | year =2007 | title =Global Wind Power Market Potential | publisher =Energy Business Reports | pages =85 | url = http://www.researchandmarkets.com/reports/c50505
| accessdate =2008-11-09}}</ref> World wind generation capacity more than quadrupled between 2000 and 2006. 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 160GW of capacity to be installed worldwide,<ref name="wwindea" /> up from 73.9&nbsp;GW at the end of 2006, implying an anticipated net growth rate of more than 21% per year.

[[Wind power in Denmark|Denmark]] generates nearly one-fifth of its electricity with wind turbines -- the highest percentage of any country -- and is 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 United States]] has added more wind energy to its grid than any other country; U.S. wind power capacity grew by 45% to 16.8 gigawatts in 2007<ref>{{cite web
| url = http://www.awea.org/newsroom/releases/AWEA_Market_Release_Q4_011708.html
| title = Installed U.S. Wind Power Capacity Surged 45% in 2007
| author= |last= |first= |authorlink= |coauthors=
| date= January 17, 2008 |work= |publisher= [[American Wind Energy Association]]
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-01-20}}</ref> 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;[[megawatts|MW]] installed, which would have ranked it sixth in the world if Texas was [[Republic of Texas|a separate country]]. Iowa and Minnesota each grew to more than 1&nbsp;gigawatt 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 megawatt of wind power is equivalent to the average electricity consumption of about 250 American households.
According to the [[American Wind Energy Association]], wind will generate enough electricity in 2008 to power just over 1% (4.5 million households) of total electricity in U.S., up from less than 0.1% in 1999. [[U.S. Department of Energy]] studies have concluded wind harvested in 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 India|India]] ranks 5th in the world with a total wind power capacity of 9,645&nbsp;MW in 2008, 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>

In 2005, [[Wind power in China|China]] announced it would build a 1000-megawatt wind farm in Hebei for completion in 2020. China has set a generating target of 30,000&nbsp;MW by 2020 from renewable energy sources&nbsp;— it says 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 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 GW by 2010, with China shortly thereafter pursuing the United States for the world wind power lead.<ref name="china_wind_2008"/>

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

Another growing market is [[Wind power in Brazil|Brazil]], with a wind potential of 143&nbsp;GW.<ref>{{cite web| url= http://www.cresesb.cepel.br/atlas_eolico_brasil/atlas-web.htm | title=Atlas do Potencial Eólico Brasileiro| accessdate=2006-04-21}}</ref> The federal government has created an incentive program, called Proinfa,<ref>{{cite web| url= http://www.eletrobras.gov.br/EM_Programas_Proinfa/default.asp | title=Eletrobrás&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 100MW although there are negotiations to double this capacity. The plant could be operational by 2010.

[[Wind power in France|France]] has announced a target of 12,500 MW installed by 2010, 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>
{| class="wikitable" style="float: left; margin-left: 10px"
! colspan="14" align=center style="background-color: #cfb;" | Annual Wind Power Generation (TWh) for Top 10 countries and their total electricity consumption(TWh)<ref>[http://www.bp.com/liveassets/bp_internet/globalbp/globalbp_uk_english/reports_and_publications/statistical_energy_review_2008/STAGING/local_assets/downloads/spreadsheets/statistical_review_full_report_workbook_2008.xls BP.com]</ref><ref>http://www.sp.com.cn/sjdl/sjdltj/sjdltj0612.htm</ref><ref>http://www.sp.com.cn/sjdl/sjdltj/sjdltj0512.htm</ref><ref>[http://www.eia.doe.gov/emeu/international/electricitygeneration.html Energy Information Administration - International Electricity Generation Data<!-- Bot generated title -->]</ref>
|-
! rowspan=2 style="background-color: #cfb;" | Rank
! rowspan=2 style="background-color: #cfb;" | Nation
! style="background-color: #cfb;" align=right colspan=3 | 2005
! style="background-color: #cfb;" align=right colspan=3 | 2006
! style="background-color: #cfb;" align=right colspan=3 | 2007
! style="background-color: #cfb;" align=right colspan=3 | 2008
|-
| style="background-color: #cfb;" align=right | Wind Power||style="background-color: #cfb;"|%||style="background-color: #cfb;" align=right | Total Power||style="background-color: #cfb;" align=right | Wind Power||style="background-color: #cfb;"|%||style="background-color: #cfb;" align=right | Total Power||style="background-color: #cfb;" align=right | Wind Power||style="background-color: #cfb;"|%|| align=right style="background-color: #cfb;" | Total Power||style="background-color: #cfb;" align=right | Wind Power||style="background-color: #cfb;"|%|| align=right style="background-color: #cfb;" | Total Power
|-
| align=right | 1 || [[Wind power in Germany|Germany]] || align=right | 27.225||5.1|| align=right | 533.700|| align=right | 30.700||5.4|| align=right | 569.943|| align=right | 39.500||6.8|| align=right | 584.939<ref>http://www.iea.org/Textbase/stats/surveys/mes.pdf</ref>|| align=right | |||| align=right |
|-
| align=right | 2 || [[Wind power in the United States|United States]] || align=right | || || align=right | 4049.8|| align=right | 26.3<ref>[http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=212819 Analysis of wind farm energy produced in the United States]</ref>||0.6|| align=right | 4104.967|| align=right |32.14<ref>http://www.eia.doe.gov/cneaf/alternate/page/renew_energy_consump/table3.html</ref> ||0.77 || align=right | 4179.908|| align=right | |||| align=right |
|-
| align=right | 3 || [[Wind power in Spain|Spain]] || align=right | 23.166||9.1|| align=right | 254.90|| align=right | 29.777||10.1|| align=right | 294.596|| align=right | 29.4<ref>http://www.bmu.de/files/pdfs/allgemein/application/pdf/ee_in_zahlen_en_26.pdf</ref>||9.7 || align=right | 303.758|| align=right | ||10<ref name=gusty/>|| align=right |
|-
| align=right | 4 || [[Wind power in India|India]] || align=right | || || align=right | 679.2|| align=right | || || align=right | 726.7|| align=right |14.7 ||1.9|| align=right | 774.7|| align=right | |||| align=right |
|-
| align=right | 5 || [[Wind power in China|China]] || align=right | || || align=right | 2474.7|| align=right | 2.70||0.1|| align=right | 2834.4|| align=right | 5.6<ref>http://www.zdxw.com.cn/bgscpd/sdcpfx/200802/t20080225_219745.htm</ref>||0.172 || align=right | 3255.9|| align=right |12.8 <ref>http://www.gov.cn/gzdt/2009-01/09/content_1200434.htm</ref>||0.374|| align=right | 3426.8
|-
| align=right | 6 || [[Wind power in Italy|Italy]] || align=right | 2.34 || 0.71 || align=right | 330.4|| align=right | 2.96||0.9|| align=right | 337.5|| align=right | 4.03<ref>http://www.terna.it/LinkClick.aspx?fileticket=QTuCYEB54ek%3d&tabid=720</ref>||1.186 || align=right | 339.9|| align=right | |||| align=right |
|-
| align=right | 7 || [[Wind power in Denmark|Denmark <br />(& Faeroe Islands)]] || align=right | 6.614||19.3|| align=right | 34.30|| align=right |7.432 ||16.8|| align=right | 44.24|| align=right | || || align=right | 37.276|| align=right | ||19<ref name=gusty>{{cite news |first= |last= |authorlink= |coauthors= |title=Denmark's Wind of Change |url=http://www.time.com/time/magazine/article/0,9171,1881646-1,00.html |quote=As a result, wind turbines now dot Denmark, the country gets more than 19% of its electricity from the breeze (Spain and Portugal, the next highest countries, get about 10%) |work=[[Time magazine]] |date=March 16, 2009 |accessdate=2009-03-10 }}</ref>|| align=right |
|-
| align=right | 8 || [[Wind power in France|France]] || align=right | || ||align=right | 547.8 || align=right |2.323||0.4|| align=right | 550.063|| align=right | || || align=right | 545.289|| align=right | |||| align=right |
|-
| align=right | 9 || [[Wind power in the United Kingdom|United Kingdom]] || align=right | 0.973||0.2|| align=right | 407.365|| align=right | || || align=right | 383.898|| align=right | || || align=right | 379.756 <!-- || || align=right | 2,406 -->|| align=right | |||| align=right |
|-
| align=right | 10 || [[Wind power in Portugal|Portugal]] || align=right | || || align=right | 35.0|| align=right | 4.74||9.7|| align=right | 48.876|| align=right | |||| align=right | ||10<ref name=gusty/>|| align=right |
|-
! style="background-color: #cfb;" |
! style="background-color: #cfb;" | World total (TWh)
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" | 15,746.54<ref>[http://www.eia.doe.gov/emeu/international/electricityconsumption.html International Electricity Consumption]</ref>
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" | 16,790<ref>[https://www.cia.gov/library/publications/the-world-factbook/rankorder/2042rank.html CIA - The World Factbook - Rank Order - Electricity - consumption<!-- Bot generated title -->]</ref>
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
! align=right style="background-color: #cfb;" |
|}
<br clear="all"/>
== Small scale wind power ==

<!--{{Splitsection|Small scale wind power|date=September 2008}}-->
{{See|Microgeneration}}
[[Image:Urbine221dc.jpg|thumb|right|This wind turbine charges a 12 volt [[battery (electricity)|battery]] to run 12 volt appliances.]]

'''Small scale wind power''' is the name given to wind generation systems with the capacity to produce 50 [[kW]] or less of electrical power.<ref>[http://www.carbontrust.co.uk/technology/technologyaccelerator/small-wind Small-scale wind energy]</ref> Isolated communities, that otherwise rely on 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. Increasingly, U.S. consumers are choosing to purchase grid-connected turbines in the 1 to 10 kilowatt range to power their whole homes.{{Fact|date=November 2008}} Household generator units of more than 1&nbsp;kW are now functioning in several countries, and in every state in the U.S.{{Fact|date=November 2008}} 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, making the potential carbon savings of small wind turbines difficult to determine.

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) and 0.6 million tonnes of carbon dioxide (Mt CO<sub>2</sub>) emission savings. This is based on 10% of households installing turbines at costs competitive with grid electricity, which is currently around 12p per kilowatt-hour.<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 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 ==

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

=== Growth and cost trends ===

Wind and [[hydroelectric]] power generation have negligible fuel costs and relatively low maintenance costs; in economic terms, wind power has a low [[marginal cost]] and a high proportion of capital cost. The estimated [[average cost]] per unit incorporates the cost of construction of the turbine and transmission facilities, borrowed funds, return to investors (including cost of risk), estimated annual production, and other components, averaged over the projected useful life of the equipment, which may be in excess of twenty years. Energy cost estimates are highly dependent on these assumptions so published cost figures can differ substantially. A British Wind Energy Association report gives an average generation cost of onshore wind power of around 3.2 cents per kilowatt hour (2005).<ref name="BWEA"> [http://www.bwea.com/pdf/briefings/target-2005-small.pdf BWEA report on onshore wind costs] (PDF).</ref> Cost per unit of energy produced was estimated in 2006 to be comparable to the cost of new generating capacity in the United States for coal and natural gas: wind cost was estimated at $55.80 per MWh, coal at $53.10/MWh and natural gas at $52.50.<ref>{{cite web
| url= http://www.eia.doe.gov/oiaf/archive/ieo06/special_topics.html
| title= "International Energy Outlook", 2006
| author= |last= |first= |authorlink= |coauthors=
| date= |year= |month= |format= [[HTML]] |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 one-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 per kilowatt in 2007,<ref name=gwec2007/> compared to €1,100 per kilowatt in 2005.<ref>[http://www.gwec.net/fileadmin/documents/Publications/GWEC-Global_Wind_05_Report_low_res_01.pdf Global Wind 2005 Report]</ref> Not as many facilities can produce large modern turbines and their towers and foundations, so constraints develop in the supply of turbines resulting in higher costs.<ref>[http://www.sunjournal.com/story/226451-3/Business/Wind_turbine_shortage_continues_costs_rising/ Wind turbine shortage continues; costs rising]</ref> Research from a wide variety of sources in various countries shows that support for wind power is consistently between 70 and 80 percent amongst 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 GW, taking the total installed wind energy capacity to 94 GW, up from 74 GW in 2006. Despite constraints facing supply chains for wind turbines, the annual market for wind continued to increase at an estimated rate of 31% following 32% growth in 2006. In terms of economic value, the wind energy sector has become one of the important players in the energy markets, with the total value of new generating equipment installed in 2007 reaching €25 billion, or US$36 billion.<ref name=gwec2007>[http://www.gwec.net/index.php?id=30&no_cache=1&tx_ttnews%5Btt_news%5D=121&tx_ttnews%5BbackPid%5D=4&cHash=f9b4af1cd0 Continuing boom in wind energy&nbsp;– 20 GW of new capacity in 2007]</ref>

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 ===
[[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 to date<ref>{{cite web| url= http://www.stanford.edu/group/efmh/winds/global_winds.html | title=Evaluation of global wind power| first=Cristina L.| last=Archer| coauthors=[[Mark Z. Jacobson]]| accessdate=2006-04-21}}</ref> found the potential of wind power on land and near-shore to be 72&nbsp;[[terawatt|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. It assumes 6 turbines per square kilometer for 77 m diameter, 1.5 MW turbines on roughly 13% of the total global land area (though that land would also be available for other compatible uses such as farming). The authors acknowledge that many practical barriers would need to be overcome to reach this theoretical capacity.

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

=== Direct costs ===

Many potential sites for wind farms are far from demand centres, requiring substantially more money to construct new transmission lines and substations. 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 kilowatt-hour.<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 pricing regime for power producers. Electricity prices are highly regulated worldwide, and in many locations may not reflect the full cost of production, let alone indirect subsidies or negative externalities. Customers may enter into long-term pricing contracts for wind to reduce the risk of future pricing changes, thereby ensuring more stable returns for projects at the development stage. These may take the form of standard offer contracts, whereby the system operator undertakes to purchase power from wind at a fixed price for a certain period (perhaps up to a limit); these prices may be different than purchase prices from other sources, and even incorporate an implicit subsidy.

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

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

In the United States, wind power receives a tax credit for each [[kilowatt-hour]] produced; at 1.9 cents per kilowatt-hour in 2006, the credit has a yearly inflationary adjustment. Another tax benefit is [[accelerated depreciation]]. Many American states also provide incentives, such as exemption from property tax, mandated purchases, and additional markets for "[[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 like the Borealis Press print millions of greeting cards every year using this wind-generated power, and in return they can claim that they are making a powerful "green" effort, in addition to using recycled, chlorine-free paper, soy inks, and safe press wash. The organization Green-e http://www.green-e.org monitors business compliance with these renewable energy credits.

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

Wind power consumes no fuel for continuing operation, and has no emissions directly related to electricity production. Operation does not produce [[carbon dioxide]], [[sulfur dioxide]], [[Mercury (element)|mercury]], [[particulate]]s, or any other type of [[air pollution]], as fossil fuel power sources do. Wind power plants consume resources in manufacturing and construction. During manufacture of the wind turbine, [[steel]], [[concrete]], [[aluminum]] and other materials will have to be made and transported using energy-intensive processes, generally using fossil energy sources. The initial carbon dioxide emissions "pay back" is claimed by one company to be within about 9 months of operation for their offshore turbines<ref name="vestas">{{cite web
| url= http://www.vestas.com/en/about-vestas/sustainability/wind-turbines-and-the-environment/life-cycle-assessment-(lca).aspx
| title= Vestas: Life Cycle Assessments (LCA)
| author= |last= |first= |authorlink= |coauthors=
| date= |year= |month= |format= |work= |publisher=
| pages= |language= |doi= |archiveurl= |archivedate= |quote=
| accessdate= 2008-02-13}} </ref>
and the British Wind Energy Association claim the average wind farm will pay back the energy used in its manufacture within 3 to 5 months of operation.<ref>[http://www.bwea.com/energy/myths.html bwea.com: Myth: Building a wind farm takes more energy than it ever makes] retrieved on 3 November 2008</ref> However, a report to the British [[House of Lords]] in 2004 suggested a payback time of 1.1 years, taking into account factors such as plant construction and decommissioning. A shorter period for offshore facilities was given, as the higher capacity factors would more than offset the added energy costs of installation.<ref>[http://www.publications.parliament.uk/pa/ld200304/ldselect/ldsctech/126/12620.htm Select Committee on Science and Technology Fourth Report] Retrieved on 3 November 2008</ref>

Danger to birds is often the main complaint against the installation of a wind turbine.<ref>[http://environment.newscientist.com/channel/earth/dn7350-sea-birds-might-pay-for-green-electricity.html newscientist.com: Sea birds might pay for green electricity] Retrieved on 3 November 2008</ref><ref>[http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2007/06/27/eaeagle127.xml ''Daily Telegraph'' Sea eagles being killed by wind turbines] Retrieved on 3 November 2008</ref> However, studies show that the number of birds killed by wind turbines is negligible compared to the number that die as a result of other human activities such as [[traffic]], [[hunting]], [[electric power transmission|power line]]s and [[high-rise building]]s and especially the environmental impacts of using [[fossil fuels|non-clean power sources]]. For example, in the UK, where there are several hundred turbines, about one bird is killed per turbine per year; 10&nbsp;million per year are killed by cars alone.<ref>http://web.archive.org/web/20060113010247/http://www.bwea.org/media/news/birds.html</ref> The [[Audubon Society]] have also come out in support of wind energy generation, claiming that birds are over 10,000 times more likely to be killed by other human-related causes than by a wind turbine.<ref>[http://www.renewableenergyworld.com/rea/news/story?id=46840 For the Birds: Audubon Society Stands Up in Support of Wind Energy] Retrieved on 3 November 2008</ref>

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

The noise created by wind turbines is often cited as an issue, although the noise of large turbines is far less than of smaller turbines.<ref>[http://www.walesonline.co.uk/news/wales-news/2008/07/03/wind-farm-plans-scrapped-after-noise-nuisance-fears-91466-21220329/ Wind farm plans scrapped after noise nuisance fears]</ref>

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

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

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

== References ==

{{reflist|2}}

== External links ==
<!-- Discuss new proposed links on talk page first. -->
<!-- See [[Wikipedia:External links]] and [[Wikipedia:Spam]] for details -->
*[http://www.awea.org/ American Wind Energy Association (AWEA)]
*[http://www.bwea.com/energy/briefing-sheets.html British Wind Energy Association (BWEA) Briefing Sheets]
*[http://www.canwea.ca/ Canadian Wind Energy Association (CANWEA)]
*[http://www.ewea.org/ European Wind Energy Association (EWEA)]
*[http://www.gwec.net/ Global Wind Energy Council (GWEC)]
*[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://show.mappingworlds.com/world/?subject=WINDCAP Wind Cartogram on SHOW displays wind power capacity per country.]
=== Wind power projects ===
* [http://www.thewindpower.net/index_en.php Database of projects throughout the whole World]
* [http://www.offshorewind.net Database of offshore wind projects in North America]
* [http://windpowerlaw.info New York state wind projects (Wind Power Law Blog)]
* [http://www.windpowerhandbook.com/ Wind Project Community Organizing] - This free website includes dozens of current articles, links and resources about windpower, problem issues, community programs, case studies, lesson plans, etc.
* [http://www.gizmag.com/the-first-race-for-wind-powered-vehicles/9953/ Wind-powered vehicles].
* [http://windfuels.com/ Wind fuels]

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

[[Category:Wind power| ]]

{{Link FA|vi}}
[[af:Windenergie]]
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[[sv:Vindkraft]]
[[ta:காற்றுத் திறன்]]
[[te:పవన విద్యుత్తు]]
[[th:พลังงานลม]]
[[vi:Năng lượng gió]]
[[tr:Rüzgâr enerjisi]]
[[uk:Вітроенергетика]]
[[zh-yue:風力]]
[[bat-smg:Viejė energėjė]]
[[zh:風能]]

Revision as of 14:37, 10 March 2009

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