Wind Power - Wikipedia, The Free Encyclopedia

7/30/2019 Wind Power - Wikipedia, The Free Encyclopedia

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Burbo Bank Offshore Wind Farm, at

the entrance to the River Mersey in

North West England.

The Shepherds Flat Wind Farm is a

845 megawatt (MW) wind farm in

the U.S. state of Oregon.

Wind powerFrom Wikipedia, the free encyclopedia

(Redirected from Wind energy)

Wind power is the conversion of wind energy into a useful form of

energy, such as using wind turbines to make electrical power,

windmills for mechanical power, windpumps for water pumping or

drainage, or sails to propel ships.

Large wind farms consist of hundreds of individual wind turbines

which are connected to the electric power transmission network.

Offshore wind is steadier and stronger than on land, and offshore

farms have less visual impact, but construction and maintenance costs

are considerably higher. Small onshore wind farms provide electricity

to isolated locations. Utility companies increasingly buy surplus

electricity produced by small domestic wind turbines.[1]

Wind power, as an alternative to fossil fuels, is plentiful, renewable,

widely distributed, clean, produces no greenhouse gas emissions

during operation and uses little land.[2] The effects on the environment

are generally less problematic than those from other power sources.

As of 2011, Denmark is generating more than a quarter of its

electricity from wind and 83 countries around the world are using

wind power on a commercial basis.[3] In 2010 wind energy

production was over 2.5% of total worldwide electricity usage, and

growing rapidly at more than 25%per annum. The monetary cost per

unit of energy produced is similar to the cost fornew coal and naturalgas installations.[4]

Wind power is very consistent from year to year but has significant

variation over shorter time scales. The intermittency of wind seldom

creates problems when used to supply up to 20% of total electricity

demand,[5] but as the proportion increases, a need to upgrade the

grid, and a lowered ability to supplant conventional production can

occur.[6] Power management techniques such as having excess

capacity storage, geographically distributed turbines, dispatchable

backing sources, storage such as pumped-storage hydroelectricity,

exporting and importing powerto neighboring areas or reducing

demand when windproduction is low, can greatly mitigate these problems.[7] In addition, weather forecasting

permits the electricity network to be readied for the predictable variations in production that occur.[8][9]

Contents

1 History

1.1 Mechanical power

1.2 Electrical power

2 Wind energy

2.1 Distribution of wind speed
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Medieval depiction of a wind mill

2.2 High altitude winds

3 Wind farms

3.1 Feeding into grid

3.2 Offshore wind power

4 Wind power capacity and production

4.1 Growth trends

4.2 Capacity factor

4.3 Penetration4.4 Variability

4.5 Predictability

4.6 Reliability

4.7 Integration with other sources

4.8 Energy storage

4.9 Capacity credit and fuel savings

5 Economics

5.1 Cost trends

5.2 Incentives and community benefits6 Environmental effects

7 Politics

7.1 Central government

7.2 Public opinion

7.3 Community

8 Small-scale wind power

9 See also

10 Notes

11 References

12 External links

History

Main article: History of wind power

Mechanical power

Sailboats and sailing ships have been using wind power for thousands

of years, and architects have used wind-driven natural ventilation in

buildings since similarly ancient times. The use of wind to provide

mechanical power came somewhat later in antiquity. The windwheel

of the Greek engineer Heron of Alexandria in the 1st century AD is

the earliest known instance of using a wind-driven wheel to power a

machine.[10][11]

The first windmills were in use in Persia at least by the 9th century

and possibly as early as the 7th century.[12]

The use of windmillsbecame widespread across the Middle East and Central Asia, and later spread to China and India.[13] By 1000

AD, windmills were used to pump seawater for salt-making in China and Sicily.[14] Windmills were used

extensively in Northwestern Europe to grind flour from the 1180s,[13] and windpumps were used to drain land
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Blyth's "windmill" at his cottage in

Marykirk in 1891

Advertisement for a windmill electric

power system, 1897

for agriculture and for building.[15] Early immigrants to the New World brought the technology with them from

Europe.[15]

In the US, the development of the water-pumping windmill was the major factor in allowing the farming and

ranching of vast areas otherwise devoid of readily accessible water.[16] Windpumps contributed to the

expansion of rail transport systems throughout the world, by pumping water from water wells for steam

locomotives. The multi-bladed wind turbine atop a lattice tower made of wood or steel was a century a fixture

of the landscape throughout rural America.[17]

In 1881, Lord Kelvin proposed using wind power when coal ran out, as "so little of it is left".[18] Solar power

was also proposed, at about the same time.[19]

Electrical power

In July 1887, a Scottish

academic, Professor

James Blyth, built a cloth-

sailed wind turbine in the

garden of his holiday

cottage in Marykirk and

used the electricity it

produced to charge

accumulators which he

used to power the lights in

his cottage.[20] His

experiments culminated in

a UK patent in 1891.[21]

In the winter of 188788 US inventorCharles F. Brush produced electricity using a wind powered

generator 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 used to

produce hydrogen and Oxygen by electrolysis and a mixture of the

two gases was stored for use as a fuel.[21] La Cour was the first to

discover that fast rotating wind turbines with fewer rotor blades were

the most efficient in generating electricity and in 1904 he founded the

Society of Wind Electricians.[22]

By the mid-1920s, 1 to 3-kilowatt wind generators developed by

companies such as Parris-Dunn and Jacobs Wind-electric[18] found

widespread use in the rural areas of the midwestern Great Plains of the US but by the 1940s the demand for

more power and the coming of the electrical grid throughout those areas made these small generators

obsolete.[23]

IN 1931 the French aeronautical engineer, George Darrieus was granted a patent for the Darrieus wind turbine

which uses vertical-axis airfoils to create rotation[24] and a 100 kW precursor to the modern horizontal wind

generator was used in Yalta, in the USSR. In 1956 Johannes Juul, a former student of la Cour, built a 200 kW,

three-bladed turbine at Gedser in Denmark, which influenced the design of many later turbines.[22]
http://en.wikipedia.org/wiki/Gedser_wind_turbinehttp://en.wikipedia.org/wiki/Johannes_Juulhttp://en.wikipedia.org/wiki/Airfoilhttp://en.wikipedia.org/wiki/Darrieus_wind_turbinehttp://en.wikipedia.org/wiki/Georges_Jean_Marie_Darrieushttp://en.wikipedia.org/wiki/Jacobs_Windhttp://en.wikipedia.org/wiki/Parris-Dunnhttp://en.wikipedia.org/wiki/Electrolysishttp://en.wikipedia.org/wiki/Oxygenhttp://en.wikipedia.org/wiki/Hydrogenhttp://en.wikipedia.org/wiki/Poul_la_Courhttp://en.wikipedia.org/wiki/Charles_F._Brushhttp://en.wikipedia.org/wiki/Accumulator_(energy)http://en.wikipedia.org/wiki/James_Blyth_(engineer)http://en.wikipedia.org/wiki/William_Thomson,_1st_Baron_Kelvinhttp://en.wikipedia.org/wiki/Steam_locomotivehttp://en.wikipedia.org/wiki/New_Worldhttp://en.wikipedia.org/wiki/File:Electric_Power_Generating_Windmill_system_advertisement_1897.jpghttp://en.wikipedia.org/wiki/File:James_Blyth%27s_1891_windmill.jpg


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Map of available wind power for theUnited States. Color codes indicate

wind power density class. (click to

see larger)

In 1975 the United States Department of Energy funded a project to develop utility-scale wind turbines. The

NASA wind turbines project built thirteen experimental turbines which paved the way for much of the

technology used today.[22] Since then, turbines have increased greatly in size with the Enercon E-126 capable o

delivering up to 7.5 Megawatts (MW).[nb 1][25] Wind turbine production has expanded to many countries and

wind power is expected to grow worldwide in the twenty-first century.

Wind energy

Wind energy is the kinetic energy of air in motion, also called wind. Total wind energy flowing through an

imaginary areaA during the time tis:

[26]

where is the density of air; v is the wind speed;Avtis the volume of air passing throughA (which is

considered perpendicular to the direction of the wind);Avt is therefore the mass m passing per unit time. Note

that v

2 is the kinetic energy of the moving air per unit volume.

Power is energy per unit time, so the wind power incident onA (e.g. equal to the rotor area of a wind turbine) is:

[26]

Wind power in an open air stream is thusproportionalto the third powerof the wind speed; the available

power increases eightfold when the wind speed doubles. Wind turbines for grid electricity therefore need to be

especially efficient at greater wind speeds.

Wind is the movement of air across the surface of the Earth, affected

by areas of high pressure and of low pressure.[27] The surface of the

Earth is heated unevenly by the Sun, depending on factors such as the

angle of incidence of the sun's rays at the surface (which differs with

latitude and time of day) and whether the land is open or covered with

vegetation. Also, large bodies of water, such as the oceans, heat up

and cool down slower than the land. The heat energy absorbed at the

Earth's surface is transferred to the air directly above it and, as

warmer air is less dense than cooler air, it rises above the cool air to

form areas of high pressure and thus pressure differentials. Therotation of the Earth drags the atmosphere around with it causing

turbulence. These effects combine to cause a constantly varying

pattern of winds across the surface of the Earth.[27]

The total amount of economically extractable power available from

the wind is considerably more than present human power use from all sources.[28] Axel Kleidon of the Max

Planck Institute in Germany, carried out a "top down" calculation on how much wind energy there is, starting

with the incoming solar radiation that drives the winds by creating temperature differences in the atmosphere. He

concluded that somewhere between 18 TW and 68 TW could be extracted.[29] Cristina Archer and Mark Z.

Jacobson presented a "bottom-up" estimate, which unlike Kleidon's are based on actual measurements of windspeeds, and found that there is 1700 TW of wind power at an altitude of 100 metres over land and sea. Of this,

"between 72 and 170 TW could be extracted in a practical and cost-competitive manner".[29] They later

estimated 80 TW.[30] However research at Harvard University estimates 1 Watt/m2 on average and 2-10
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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 modeldistribution for the same average

wind speed.

Two of the wind turbines at the BlackLaw Wind Farm in Scotland

MW/km2 capacity for large scale wind farms, suggesting that these estimates of total global wind resources are

too high by a factor of about 4.[31]

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 particularlocation, a probability distribution function is often fit to the observed

data. Different locations will have different wind speed distributions.

The Weibull model closely mirrors the actual distribution of

hourly/ten-minute 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.[32]

High altitude winds

Power generation from winds usually comes from winds very close to

the surface of the earth. Winds at higher altitudes are stronger and

more consistent, and may have a global capacity of 380 TW.[30]

Recent years have seen significant advances in technologies meant to

generate electricity from high altitude winds.[33]

Wind farms

Main article: Wind farm

A wind farm is a group of wind turbines in the same location used for

production of electricity. A large wind farm may consist of several

hundred individual wind turbines distributed over an extended area,

but the land between the turbines may be used for agricultural or other

purposes. A wind farm may also be located offshore.

Almost all large wind turbines have the same design a horizontal

axis wind turbine having an upwind rotor with three blades, attached

to a nacelle on top of a tall tubular tower. 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 electric current is increased in voltage

with a transformer for connection to the high voltage electric power transmission system.

Many of the largest operational onshore wind farms are located in the US. As of 2012, the Alta Wind Energy

Center is the largest onshore wind farm in the world at 1020 MW, followed by the Shepherds Flat Wind Farm

(845 MW), and the Roscoe Wind Farm (781.5 MW). As of September 2012, the Sheringham Shoal Offshore

Wind Farm and the Thanet Wind Farm in the UK are the largest offshore wind farms in the world at 317 MW

and 300 MW, followed by Horns Rev II (209 MW) in Denmark.

There are many large wind farms under construction including; The London Array (offshore) (1000 MW),

BARD Offshore 1 (400 MW), Sheringham Shoal Offshore Wind Farm (317 MW), Lincs Wind Farm

(offshore), Clyde Wind Farm (548 MW), Greater Gabbard wind farm (500 MW), Macarthur Wind Farm (420
http://en.wikipedia.org/wiki/Macarthur_Wind_Farmhttp://en.wikipedia.org/wiki/Greater_Gabbard_wind_farmhttp://en.wikipedia.org/wiki/Clyde_Wind_Farmhttp://en.wikipedia.org/wiki/Lincs_Wind_Farmhttp://en.wikipedia.org/wiki/Sheringham_Shoal_Offshore_Wind_Farmhttp://en.wikipedia.org/wiki/BARD_Offshore_1http://en.wikipedia.org/wiki/London_Arrayhttp://en.wikipedia.org/wiki/Horns_Revhttp://en.wikipedia.org/wiki/Thanet_Wind_Farmhttp://en.wikipedia.org/wiki/Sheringham_Shoal_Offshore_Wind_Farmhttp://en.wikipedia.org/wiki/Roscoe_Wind_Farmhttp://en.wikipedia.org/wiki/Shepherds_Flat_Wind_Farmhttp://en.wikipedia.org/wiki/Alta_Wind_Energy_Centerhttp://en.wikipedia.org/wiki/Electric_power_transmissionhttp://en.wikipedia.org/wiki/Transformerhttp://en.wikipedia.org/wiki/Wind_farmhttp://en.wikipedia.org/wiki/Wind_turbinehttp://en.wikipedia.org/wiki/Wind_farmhttp://en.wikipedia.org/wiki/High-altitude_wind_powerhttp://en.wikipedia.org/wiki/Rayleigh_distributionhttp://en.wikipedia.org/wiki/Weibull_distributionhttp://en.wikipedia.org/wiki/Black_Law_Wind_Farmhttp://en.wikipedia.org/wiki/File:Windfarm_-_geograph.org.uk_-_150717.jpghttp://en.wikipedia.org/wiki/File:Lee_Ranch_Wind_Speed_Frequency.svg


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Aerial view of Lillgrund Wind Farm,

Sweden

MW), Lower Snake River Wind Project (343 MW) and Walney Wind Farm (367 MW).

A panoramic view of the Whitelee Wind Farm with Lochgoin Reservoir in the foreground.

Feeding into grid

Induction generators, often used for wind power, require reactive power for excitation so substations used in

wind-power collection systems include substantial capacitor banks for power factor correction.[34] Different

types of wind turbine generators behave differently during transmission grid disturbances, so extensive modelling

of the dynamic electromechanical characteristics of a new wind farm is required by transmission system

operators to ensure predictable stable behaviour during system faults (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 machines generally have more desirable properties for grid

interconnection.[35][36] Transmission systems operators will supply a wind farm developer with agrid code to

specify the requirements for interconnection to the transmission grid. This will include power factor, constancy ofrequency and dynamic behavior of the wind farm turbines during a system fault.[37][38]

Offshore wind power

Main article: Offshore wind power

Offshore wind power refers to the construction of wind farms in large

bodies of water to generate electricity. These installations can utilise

the more frequent and powerful winds that are available in these

locations and have less aesthetic impact on the landscape than land

based projects. However, the construction and the maintenance costs

are considerably higher.[39][40] As of 2011, offshore wind farms were

at least 3 times more expensive than onshore wind farms of the same

nominal power[41] but these costs are expected to fall as the industry

matures.[42]

Siemens and Vestas are the leading turbine suppliers for offshore

wind power. DONG Energy, Vattenfall and E.ON are the leading offshore operators.[43] As of October 2010,

3.16 GW of offshore wind power capacity was operational, mainly in Northern Europe. According to BTMConsult, more than 16 GW of additional capacity will be installed before the end of 2014 and the UK and

Germany will become the two leading markets. Offshore wind power capacity is expected to reach a total of 75

GW worldwide by 2020, with significant contributions from China and the US.[43]
http://en.wikipedia.org/wiki/BTM_Consulthttp://en.wikipedia.org/wiki/E.ONhttp://en.wikipedia.org/wiki/Vattenfallhttp://en.wikipedia.org/wiki/DONG_Energyhttp://en.wikipedia.org/wiki/Vestashttp://en.wikipedia.org/wiki/Siemenshttp://en.wikipedia.org/wiki/Offshore_wind_powerhttp://en.wikipedia.org/wiki/Utility_frequencyhttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Doubly_fed_electric_machinehttp://en.wikipedia.org/wiki/Low_voltage_ride_throughhttp://en.wikipedia.org/wiki/Wind_energy_softwarehttp://en.wikipedia.org/wiki/Power_factor_correctionhttp://en.wikipedia.org/wiki/Capacitorhttp://en.wikipedia.org/wiki/Electrical_substationhttp://en.wikipedia.org/wiki/Excitation_(magnetic)http://en.wikipedia.org/wiki/Reactive_powerhttp://en.wikipedia.org/wiki/Induction_generatorhttp://en.wikipedia.org/wiki/Whitelee_Wind_Farmhttp://en.wikipedia.org/wiki/File:Whitelee_panorama.JPGhttp://en.wikipedia.org/wiki/Walney_Wind_Farmhttp://en.wikipedia.org/wiki/Lower_Snake_River_Wind_Projecthttp://en.wikipedia.org/wiki/Lillgrund_Wind_Farmhttp://en.wikipedia.org/wiki/File:Sund_mpazdziora.JPG


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Worldwide wind generation up to

2010

As of September 2012, the Greater Gabbard Wind Farm in the United Kingdom is the largest offshore wind

farm in the world at 504 MW, followed by Walney Wind Farm (367 MW), also in the UK. The London Array

(630 MW) is the largest project under construction.

Wind power capacity and production

Main article: Wind power by country

Worldwide there are now over two hundred thousand wind turbines

operating, with a total nameplate capacity of 282,482 MW as of end

2012.[44] The European Union alone passed some 100,000 MW

nameplate capacity in September 2012,[45] while the United States

surpassed 50,000 MW in August 2012 and China passed 50,000

MW the same month.[46][47]

World wind generation capacity more than quadrupled between 2000

and 2006, doubling about every three years. The United States

pioneered wind farms and led the world in installed capacity in the

1980s and into the 1990s. In 1997 German installed capacity

surpassed the U.S. and led until once again overtaken by the U.S. in

2008. China has been rapidly expanding its wind installations in the

late 2000s and passed the U.S. in 2010 to become the world leader.

At the end of 2012, worldwide nameplate capacity of wind-powered

generators was 282 gigawatts (GW), growing by 44 GW over the

preceding year.[44] According to the World Wind Energy

Association, an industry organization, in 2010 wind power generated430 TWh or about 2.5% of worldwide electricity usage,[48] up from

1.5% in 2008 and 0.1% in 1997.[49] Between 2005 and 2010 the average annual growth in new installations

was 27.6 percent.[50] Wind power market penetration is expected to reach 3.35 percent by 2013 and 8

percent by 2018.[50][51]

Several countries have already achieved relatively high levels of penetration, such as 28% of stationary (grid)

electricity production in Denmark (2011),[52] 19% in Portugal (2011),[53] 16% in Spain (2011),[54] 14% in

Ireland (2010)[55] and 8% in Germany (2011).[56] As of 2011, 83 countries around the world were using wind

power on a commercial basis.[3]

Europe accounted for 48% of the world total wind power generation capacity in 2009. In 2010, Spain became

Europe's leading producer of wind energy, achieving 42,976 GWh. Germany held the top spot in Europe in

terms of installed capacity, with a total of 27,215 MW as of 31 December 2010. [57]
http://en.wikipedia.org/wiki/Wind_power_in_Europehttp://en.wikipedia.org/wiki/Wind_power_in_Germanyhttp://en.wikipedia.org/wiki/Wind_power_in_Irelandhttp://en.wikipedia.org/wiki/Wind_power_in_Spainhttp://en.wikipedia.org/wiki/Wind_power_in_Portugalhttp://en.wikipedia.org/wiki/Wind_power_in_Denmarkhttp://en.wikipedia.org/wiki/World_Wind_Energy_Associationhttp://en.wikipedia.org/wiki/Gigawatthttp://en.wikipedia.org/wiki/Nameplate_capacityhttp://en.wikipedia.org/wiki/Wind_power_in_the_United_Stateshttp://en.wikipedia.org/wiki/Wind_power_in_the_People%27s_Republic_of_Chinahttp://en.wikipedia.org/wiki/European_Unionhttp://en.wikipedia.org/wiki/Nameplate_capacityhttp://en.wikipedia.org/wiki/Wind_power_by_countryhttp://en.wikipedia.org/wiki/London_Arrayhttp://en.wikipedia.org/wiki/Walney_Wind_Farmhttp://en.wikipedia.org/wiki/Megawatthttp://en.wikipedia.org/wiki/Greater_Gabbard_Wind_Farmhttp://en.wikipedia.org/wiki/File:Wind_generation-with_semilog_plot.png


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Worldwide installed capacity 1997

2020 [MW], developments and

prognosis. Data source: WWEA[59]

Top 10 countries

by nameplate windpower capacity

(2012 year-end)[44]

Country

New 2012

capacity

(MW)

Windpower total

capacity

(MW)

% world

total

China 12,960 75,324 26.7United

States13,124 60,007 21.2

Germany 2,145 31,308 11.1

Spain 1,122 22,796 8.1

India 2,336 18,421 6.5

UK 1,897 8,845 3.0

Italy 1,273 8,144 2.9

France 757 7,564 2.7

Canada 935 6,200 2.2

Portugal 145 4,525 1.6

(rest of

world)6,737 39,853 14.1

World

total44,799 MW 282,587 MW 100%

Top 10 countries

by windpower electricity production

(2011 totals)[58]

Country

Windpower

production

(TWh)

% world

total

UnitedStates 120.5 26.2

China 88.6 19.3

Germany 48.9 10.6

Spain 42.4 9.2

India 24.9 5.4

Canada 19.7 4.3

UK 15.5 3.4

France 12.2 2.7

Italy 9.9 2.1

Denmark 9.8 2.1

(rest of

world)67.7 14.7

World

total459.9 TWh 100%

Growth trends

In 2010, more than half of all new wind power was added outside of

the traditional markets in Europe and North America. This was largely

from new construction in China, which accounted for nearly half the

new wind installations (16.5 GW).[62]

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 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.[63]

Although the wind power industry was affected by the 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 newinstallations has been 27.6 percent each year. In the forecast to 2013 the expected average annual growth rate

is 15.7 percent.[50][51] More than 200 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.[50][51]
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Worldwide installed wind power

capacity forecast (Source: Global

Wind Energy Council)[60][61]

Worldwide installed wind power

capacity (Source: GWEC)[64]

Capacity factor

Since wind speed is not constant, a wind farm's annual energy

production is never as much as the sum of the generator nameplate

ratings multiplied by the total hours in a year. The ratio of actual

productivity in a year to this theoretical maximum is called the

capacity factor. Typical capacity factors are 1550%, with values at

the upper end of the range in favourable sites and are due to windturbine improvements.[65][66][nb 2]

Online data is available for some locations and the capacity factor can

be calculated from the yearly output.[67][68] For example, the German

nation-wide average wind power capacity factor over all of 2012 was

ust under 17.5%

(45867 GWh/yr / (29.9 GW 24 366) = 0.1746)[69] and the

capacity factor for Scottish wind farms averaged 24% between 2008

and 2010.[70]

Unlike fueled generating plants the capacity factor is affected by

several parameters, including the variability of the wind at the site but

also the generator size. A small generator would be cheaper and

achieve a higher capacity factor but would produce less electricity

(and thus less profit) in high winds. Conversely, a large generator

would cost more but generate little extra power and, depending on the type, may stall out at low wind speed.

Thus an optimum capacity factor would be aimed for, of around 4050%.[66][71]

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 U.S. wind turbine fleet is shown to be increasing as the technology

improves. The capacity factor achieved by new wind turbines in 2010 reached almost 40%.[72][73]

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 energy storage, 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 compensate for thevarying power generation produced by wind plants. Studies have indicated that 20% of the total annual electrical

energy consumption may be incorporated with minimal difficulty.[74] These studies have been for locations with

geographically dispersed wind farms, some degree of dispatchable energy or hydropower with storage capacity,

demand management, and interconnected to a large grid area enabling the export of electricity when needed.

Beyond the 20% level, there are few technical limits, but the economic implications become more significant.

Electrical utilities continue to study the effects of large scale penetration of wind generation on system stability

and economics.[75][76][77][78]

A wind energy penetration figure can be specified for different durations of time. On an annual basis, as of 2011,

few grid systems have penetration levels above five percent: Denmark 26%, Portugal 17%, Spain 15%,Ireland 14%, and Germany 9%.[79] For the U.S. in 2011, the penetration level was estimated at 2.9%.[79]

To obtain 100% from wind annually requires substantial long term storage. On a monthly, weekly, daily, or

hourly basisor lesswind can supply as much as or more than 100% of current use, with the rest stored or
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Windmills are typically installed in

favourable windy locations. In the

image, wind power generators in

Spain, near an Osborne bull.

Increase in system

operation costs,

Euros per MWh, for

10% & 20% windshare[5]

Country 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

exported. Seasonal industry can take advantage of high wind and low usage times such as at night when wind

output can exceed normal demand. Such industry can include production of silicon, aluminum, steel, or of natural

gas, and hydrogen, which allow long term storage, facilitating 100% energy from variable renewable

energy.[80][81] Homes can also be programmed to accept extra electricity on demand, for example by remotely

turning up water heater thermostats.[82]

GE has installed a prototype wind turbine with onboard battery similar to that of an electric car, equivalent of 1

minute of production. Despite the small capacity, it is enough to guarantee that power output complies withforecast for 15 minutes, as the battery is used to eliminate the difference rather than provide full output. The

increased predictability can be used to take wind power penetration from 20 to 30 or 40 per cent. The battery

cost can be retrieved by selling burst power on demand and reducing backup needs from gas plants.[83]

Variability

Main articles: Intermittent energy source and wind power forecasting

Electricity generated from wind power can be highly variable at

several different timescales: hourly, daily, or seasonally. Annualvariation 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. Intermittency and the non-dispatchable nature of

wind energy production can raise costs for regulation, incremental

operating reserve, and (at high penetration levels) could require an

increase in the already existing energy demand management, load

shedding, storage solutions or system interconnection with HVDCcables.

Fluctuations in load and allowance for failure of large fossil-fuel generating units require reserve capacity that can

also compensate for variability of wind generation.

Wind power is however, variable, but during low wind periods it can be replaced by

other power sources. Transmission networks presently cope with outages of other

generation plants and daily changes in electrical demand, but the capacity factor of

intermittent power sources such as wind power, are unlike those of conventional

power generation plants, being on average 70-90%,[citation needed] higher than winds,thus offering a challenge to the prospect of large wind power grid penetration.

Presently, grid systems with large wind penetration require an increase in the

frequency of usage of natural gas spinning reserve power plants to prevent a total loss

of electricity in the event that conditions are not favorable for power production from

the wind.[84][85][86] At low wind power grid penetration, this is less of an issue.

A report on Denmark's wind power noted that their wind power network provided

less than 1% of average demand on 54 days during the year 2002.[87] 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.[88] 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.[87] According to a 2007 Stanford University

study published in the Journal of Applied Meteorology and Climatology, interconnecting ten or more wind farms
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can allow an average of 33% of the total energy produced to be used as reliable, baseload electric power, as

long as minimum criteria are met for wind speed and turbine height. [89][90]

Conversely, on particularly windy days, even with penetration levels of 16%, wind power generation can

surpass all other electricity sources in a country. In Spain, on 16 April 2012 wind power production reached the

highest percentage of electricity production till then, with wind farms covering 60.46% of the total demand. [91]

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 in the table on the right. 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. The additional costs, which are modest, can be quantified.[92]

Solar power tends to be complementary to wind.[93][94] On daily to weekly timescales, high pressure areas tend

to bring clear skies and low surface winds, whereas low pressure areas tend to be windier and cloudier. On

seasonal timescales, solar energy peaks in summer, whereas in many areas wind energy is lower in summer and

higher in winter.[nb 3][95] Thus the intermittencies of wind and solar power tend to cancel each other somewhat.

In 2007 the Institute for Solar Energy Supply Technology of the University of Kassel pilot-tested a combined

power plant linking solar, wind, biogas and hydrostorage to provide load-following power around the clock andthroughout the year, entirely from renewable sources.[96]

Predictability

Wind power forecasting methods are used, but predictability of any particular wind farm is low for short-term

operation. For any particular generator there is an 80% chance that wind output will change less than 10% in an

hour and a 40% chance that it will change 10% or more in 5 hours. [97]

However, studies by Graham Sinden (2009) suggest that, in practice, the variations in thousands of wind

turbines, spread out over several different sites and wind regimes, are smoothed. As the distance between sites

increases, the correlation between wind speeds measured at those sites, decreases.[98]

Thus, while the output from a single turbine can vary greatly and rapidly as local wind speeds vary, as more

turbines are connected over larger and larger areas the average power output becomes less variable and more

predictable.[99]

Wind speeds can be accurately forecast over large areas, and hence wind is a predictable source of power for

feeding into an electrical grid. However, due to the variability, although predictable, wind energy availability must

be scheduled.

Reliability

Wind power hardly ever suffers major technical failures, since failures of individual wind turbines have hardly any

effect on overall power, so that the distributed wind power is highly reliable and predictable,[100] whereas

conventional generators, while far less variable, can suffer major unpredictable outages.

Integration with other sources

The combination of diversifying variable renewables by type and location, forecasting their variation, andintegrating them with dispatchable renewables, flexible fueled generators, and demand response can create a

power system that has the potential to meet power supply needs reliably. Integrating ever-higher levels of

renewables is being successfully demonstrated in the real world:[101]
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In 2009, eight American and three European authorities, writing in the leading electrical engineers'

professional journal, didn't find "a credible and firm technical limit to the amount of wind energy

that can be accommodated by electricity grids". In fact, not one of more than 200 international

studies, nor official studies for the eastern and western U.S. regions, nor the International Energy

Agency, has found major costs or technical barriers to reliably integrating up to 30% variable

renewable supplies into the grid, and in some studies much more. Reinventing Fire[101]

Energy storage

In general, hydroelectricity complements wind power very well. When the wind is blowing strongly, nearby

hydroelectric plants can temporarily hold back their water, and when the wind drops they can rapidly increase

production again giving a very even power supply.

Pumped-storage hydroelectricity or other forms of grid energy storage can store energy developed by high-wind

periods and release it when needed.[102] The type of storage needed depends on the wind penetration level

low penetration requires daily storage, and high penetration requires both short and long term storage as long

as a month or more. 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 offsetthe 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. For example, in the UK, the

1.7 GW Dinorwig pumped storage plant evens out electrical demand peaks, and allows base-load suppliers to

run their plants 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.[103][104]

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 the use of air conditioning. Some utilities subsidize the purchase of geothermal heatpumps by their customers, to reduce electricity demand during the summer months by making air conditioning up

to 70% more efficient;[105] 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 U.S. it is estimated that to upgrade the

transmission system to take in planned or potential renewables would cost at least $60 billion.[106]

Germany has an installed capacity of wind and solar that exceeds daily demand, and has been exporting peak

power to neighboring countries. A more practical solution is the installation of thirty days storage capacity able

to supply 80% of demand, which will become necessary when most of Europe's energy is obtained from wind

power and solar power. Just as the EU requires member countries to maintain 90 days strategic reserves of oil it

can be expected that countries will provide electricity storage, instead of expecting to use their neighbors for net

metering.[107]

Capacity credit and fuel savings

The capacity credit of wind is estimated by determining the capacity of conventional plants displaced by wind

power, whilst maintaining the same degree of system security,.[108] However, the precise value is irrelevant since

the main value of wind is its fuel and CO2 savings,[109] and wind is not expected to be constantly available.[110]

Economics
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Estimated cost per MWh for windpower in Denmark

The National Renewable Energy

Laboratory projects that the levelized

cost of wind power in the U.S. will

decline about 25% from 2012 to

2030.[112]

A turbine blade convoy passing

through Edenfield in the U.K. (2008).

Even longer two-piece blades are now

manufactured, and then assembled

on-site to reduce difficulties in

transportion.

Wind turbines reached grid parity (the point at which the cost of wind power matches traditional sources) in

some areas of Europe in the mid-2000s, and in the US around the same time. Falling prices continue to drive the

levelized cost down and it has been suggested that it has reached general grid parity in Europe in 2010, and will

reach the same point in the US around 2016 due to an expected reduction in capital costs of about 12%.[111]

Nevertheless, a significant amount of the wind power resource in North America remains above grid parity due

to the long transmission distances involved.

Cost trends

Wind power has low ongoing costs, but a moderate capital cost. The

marginal cost of wind energy once a plant is constructed is usually less

than 1-cent per kWh.[113] This cost has reduced as wind turbine

technology improved. There are now longer and lighter wind turbine

blades, improvements in turbine performance and increased power

generation efficiency. Also, wind project capital and maintenance

costs have continued to decline.[114]

The estimated average cost per unit incorporates the cost ofconstruction 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. 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 turbines were

mass-produced.[115] As of 2012 capital costs for wind turbines are

substantially lower than 20082010 but are still above 2002

levels.[116] A 2011 report from the American Wind Energy

Association stated, "Wind's costs have dropped over the past two

ears, in the range of 5 to 6 cents per kilowatt-hour recently.... about

2 cents cheaper than coal-fired electricity, and more projects were

financed through debt arrangements than tax equity structures last

ear.... winning more mainstream acceptance from Wall Street's

banks.... Equipment makers can also deliver products in the same

ear that they are ordered instead of waiting up to three years as was

the case in previous cycles.... 5,600 MW of new installed capacity isunder construction in the United States, more than double the number

at this point in 2010. Thirty-five percent of all new power generation

built in the United States since 2005 has come from wind, more than

new gas and coal plants combined, as power providers are

increasingly enticed to wind as a convenient hedge against

unpredictable commodity price moves."[117]

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 kWh (2005).[118] Cost per unit of energy produced wasestimated 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 MWh, coal at $53.10/MWh and natural gas at $52.50.[4] Similar comparative results with
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U.S. landowners typically receive

$3,000$5,000 annual rental income

per wind turbine, while farmers

continue to grow crops or graze

cattle up to the foot of the

turbines.[124] Shown: the Brazos

Wind Farm in Texas.

natural gas were obtained in a governmental study in the UK in 2011.[119] A 2009 study on wind power in

Spain by Gabriel Calzada Alvarez of King Juan Carlos University concluded that each installed MW of wind

power led to the loss of 4.27 jobs, by raising energy costs and driving away electricity-intensive businesses.[120]

The U.S. Department of Energy found the study to be seriously flawed, and the conclusion unsupported. [121]

The presence of wind energy, even when subsidised, can reduce costs for consumers (5 billion/yr in Germany)

by reducing the marginal price, by minimising the use of expensive peaking power plants.[122]

In February 2013 Bloomberg New Energy Finance reported that the cost of generating electricity from newwind farms is cheaper than new coal or new baseload gas plants. When including the current Australian federal

government carbon pricing scheme their modeling gives costs (in Australian dollars) of $80/MWh for new wind

farms, $143/MWh for new coal plants and $116/MWh for new baseload gas plants. The modeling also shows

that "even without a carbon price (the most efficient way to reduce economy-wide emissions) wind energy is

14% cheaper than new coal and 18% cheaper than new gas."[123] Part of the higher costs for new coal plants is

due to high financial lending costs because of "the reputational damage of emissions-intensive investments". The

expense of gas fired plants is partly due to "export market" effects on local prices. Costs of production from

coal fired plants built in "the 1970s and 1980s" are cheaper than renewable energy sources because of

depreciation.[123]

Incentives and community benefits

The U.S. wind industry generates tens of thousands of jobs and

billions of dollars of economic activity.[126] Wind projects provide

local taxes, or payments in lieu of taxes and strengthen the economy

of rural communities by providing income to farmers with wind

turbines on their land.[124][127] Wind energy in many jurisdictions

receives financial or other support to encourage its development.

Wind energy benefits from subsidies in many jurisdictions, either toincrease its attractiveness, or to compensate for subsidies received by

other forms of production which have significant negative externalities.

In the US, wind power receives a production tax credit (PTC) of

1.5/kWh in 1993 dollars for each kWh produced, for the first ten

ears; at 2.2 cents per kWh in 2012, the credit was renewed on 2

January 2012, to include construction begun in 2013.[128] A 30% tax

credit can be applied instead of receiving the PTC.[129][130] Another

tax benefit is accelerated depreciation. Many American states also

provide incentives, such as exemption from property tax, mandated

purchases, and additional markets for "green credits".[131] The Energy Improvement and Extension Act of 2008

contains extensions of credits for wind, including microturbines. Countries such as Canada and Germany also

provide incentives for wind turbine construction, such as tax credits or minimum purchase prices for wind

generation, with assured grid access (sometimes referred to as feed-in tariffs). These feed-in tariffs are typically

set well above average electricity prices.[132][133]

Secondary market forces also provide incentives for businesses to use wind-generated power, even if there is a

premium price for the electricity. For example, socially responsible manufacturers pay utility companies a

premium that goes to subsidize and build new wind power infrastructure. Companies use wind-generated

power, and in return they can claim that they are undertaking strong "green" efforts. In the US the organization

Green-e monitors business compliance with these renewable energy credits.[134]
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Some of the 6,000 wind turbines in

California's Altamont Pass Wind Farm

aided by tax incentives during the

1980s.[125]

According to the manager of this

wind farm, livestock ignore wind

turbines, [135] and continue to graze

as they did before wind turbines were

installed.

Environmental effects

Main article: Environmental impact of wind power

Compared to the

environmental impact of

traditional energy sources,

the environmental impact ofwind power is relatively

minor in terms of pollution.

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. While a

wind farm may cover a large area of land, many land uses such asagriculture are compatible, with only small areas of turbine

foundations and infrastructure made unavailable for use.[136][137]

There are reports of bird and bat mortality at wind turbines as there are around other artificial structures. The

scale of the ecological impact may[138] or may not[139] be significant, depending on specific circumstances.

Although all artificial structures can kill birds, wind power has a disproportionate effect on certain endangered

bird species,[140] such as the precarious US population of golden eagles. An especially vulnerable group are

raptors, which are slow to reproduce and favor the high wind speed corridors that wind turbine companies build

turbines in, to maximize energy production.[140]

Although they have a negligible effect on most birds, in somelocations there is a disproportionate effects on some birds of conservation concern, such as the golden eagle and

raptor species.[140]

However, a large meta-analysis of 616 individual studies on electricity production and its effects on avian

mortality concluded that the most visible impacts of wind technology are not necessarily the most flagrant ones,

as:[141]

Wind turbines seem to present a significant threat as all their negative externalities are

concentrated in one place, while those from conventional and nuclear fuel cycles are spread out

across space and time. Avian mortality and wind energy has consequently received far moreattention and research than the avian deaths associated with coal, oil, natural gas and nuclear

power generators [although] study suggests that wind energy may be the least harmful to birds.

Prevention and mitigation of wildlife fatalities, and protection of peat bogs,[142] affect the siting and operation of

wind turbines.

There are anecdotal reports of negative effects from noise on people who live very close to wind turbines. Peer-

reviewed research has generally not supported these statements.[143]

Politics

Central government
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Fossil fuels are subsidized by many governments, and wind power and other forms of renewable energy are also

often subsidized. For example a 2009 study by the Environmental Law Institute[144] assessed the size and

structure of U.S. energy subsidies over the 20022008 period. The study estimated that subsidies to fossil-fuel

based sources amounted to approximately $72 billion over this period and subsidies to renewable fuel sources

totalled $29 billion. In the United States, the federal government has paid US$74 billion for energy subsidies to

support R&D for nuclear power ($50 billion) and fossil fuels ($24 billion) from 1973 to 2003. During this same

time frame, renewable energy technologies and energy efficiency received a total of US$26 billion. It has been

suggested that a subsidy shift would help to level the playing field and support growing energy sectors, namelysolar power, wind power, and biofuels.[145] History shows that no energy sector was developed without

subsidies.[145]

According to the International Energy Agency (IEA) (2011) energy subsidies artificially lower the price of

energy paid by consumers, raise the price received by producers or lower the cost of production. "Fossil fuels

subsidies costs generally outweigh the benefits. Subsidies to renewables and low-carbon energy technologies

can bring long-term economic and environmental benefits".[146] In November 2011, an IEA report entitled

Deploying Renewables 2011 said "subsidies in green energy technologies that were not yet competitive are

ustified in order to give an incentive to investing into technologies with clear environmental and energy security

benefits". The IEA's report disagreed with claims that renewable energy technologies are only viable throughcostly subsidies and not able to produce energy reliably to meet demand.

In the US, the wind power industry has recently increased its lobbying efforts considerably, spending about $5

million in 2009 after years of relative obscurity in Washington.[147] By comparison, the US nuclear industry

alone spent over $650 million on its lobbying efforts and campaign contributions during a single ten-year period

ending in 2008.[148][149][150]

Following the 2011 Japanese nuclear accidents, Germany's federal government is working on a new plan for

increasing energy efficiency and renewable energy commercialization, with a particular focus on offshore wind

farms. Under the plan large wind turbines will be erected far away from the coastlines, where the wind blowsmore consistently than it does on land, and where the enormous turbines won't bother the inhabitants. The plan

aims to decrease Germany's dependence on energy derived from coal and nuclear power plants.[151]

Commenting on the EU's 2020 renewable energy target, economist Professor Dieter Helm is critical of how the

costs of wind power are cited by lobbyists. Helm also says that the problem of intermittent supply will probably

lead to another dash for gas or dash for coal in Europe, possibly with a negative impact on energy security. [152]

A House of Lords Select Committee report (2008) on renewable energy in the UK reported a "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".[153]

Public opinion

Surveys of public attitudes across Europe and in many other countries show strong public support for wind

power.[154][155][156] About 80 percent of EU citizens support wind power.[157] In Germany, where wind power

has gained very high social acceptance, hundreds of thousands of people have invested in citizens' wind farms

across the country and thousands of small and medium sized enterprises are running successful businesses in a

new sector that in 2008 employed 90,000 people and generated 8 percent of Germany's electricity.[158][159]

Although wind power is a popular form of energy generation, the construction of wind farms is not universallywelcomed, often for aesthetic reasons.[136][154][155][156][157][160][161]
http://en.wikipedia.org/wiki/Aestheticshttp://en.wikipedia.org/wiki/Germanyhttp://en.wikipedia.org/wiki/Europehttp://en.wikipedia.org/wiki/Select_Committee_(Westminster_System)http://en.wikipedia.org/wiki/House_of_Lordshttp://en.wikipedia.org/wiki/Energy_securityhttp://en.wikipedia.org/wiki/Dash_for_gashttp://en.wikipedia.org/wiki/Dieter_Helmhttp://en.wikipedia.org/wiki/Energy_policy_of_the_European_Unionhttp://en.wikipedia.org/wiki/Renewable_energy_commercializationhttp://en.wikipedia.org/wiki/Efficient_energy_usehttp://en.wikipedia.org/wiki/2011_Japanese_nuclear_accidentshttp://en.wikipedia.org/wiki/International_Energy_Agencyhttp://en.wikipedia.org/wiki/Biofuelshttp://en.wikipedia.org/wiki/Solar_powerhttp://en.wikipedia.org/wiki/Efficient_energy_usehttp://en.wikipedia.org/wiki/Renewable_energyhttp://en.wikipedia.org/wiki/Fossil_fuelshttp://en.wikipedia.org/wiki/Nuclear_powerhttp://en.wikipedia.org/wiki/R%26Dhttp://en.wikipedia.org/wiki/Energy_subsidies


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Environmental group members are

both more in favor of wind power

(74%) as well as more opposed

(24%). Few are undecided.

In Spain, with some exceptions, there has been little opposition to the

installation of inland wind parks. However, the projects to build

offshore parks have been more controversial.[162] In particular, the

proposal of building the biggest offshore wind power production

facility in the world in southwestern Spain in the coast of Cdiz, on the

spot of the 1805 Battle of Trafalgar.[163] has been met with strong

opposition who fear for tourism and fisheries in the area,[164] and

because the area is a war grave.[163]

Which should be increased in

Scotland?[165]

In a survey conducted by Angus Reid Strategies in October 2007, 89 per cent of respondents said that using

renewable energy sources like wind or solar power was positive for Canada, because these sources were better

for the environment. Only 4 per cent considered using renewable sources as negative since they can be

unreliable and expensive.[166] According to a Saint Consulting survey in April 2007, wind power was the

alternative energy source most likely to gain public support for future development in Canada, with only 16%opposed to this type of energy. By contrast, 3 out of 4 Canadians opposed nuclear power developments.[167]

A 2003 survey of residents living around Scotland's 10 existing wind farms found high levels of community

acceptance and strong support for wind power, with much support from those who lived closest to the wind

farms. The results of this survey support those of an earlier Scottish Executive survey 'Public attitudes to the

Environment in Scotland 2002', which found that the Scottish public would prefer the majority of their electricity

to come from renewables, and which rated wind power as the cleanest source of renewable energy.[168] A

survey conducted in 2005 showed that 74% of people in Scotland agree that wind farms are necessary to meet

current and future energy needs. When people were asked the same question in a Scottish renewables study

conducted in 2010, 78% agreed. The increase is significant as there were twice as many wind farms in 2010 asthere were in 2005. The 2010 survey also showed that 52% disagreed with the statement that wind farms are

"ugly and a blot on the landscape". 59% agreed that wind farms were necessary and that how they looked was

unimportant.[169] Scotland is planning to obtain 100% of electricity from renewable sources by 2020.[170]

Community

See also: Community debate about wind farms

Many wind power companies work with local communities to reduce environmental and other concerns

associated with particular wind farms.[173][174][175] In other cases there is direct community ownership of wind

farm projects. Appropriate government consultation, planning and approval procedures also help to minimize

environmental risks.[154][176][177] Some may still object to wind farms[178] but, according to The Australia

Institute, their concerns should be weighed against the need to address the threats posed by climate change and
http://en.wikipedia.org/wiki/Climate_changehttp://en.wikipedia.org/wiki/The_Australia_Institutehttp://en.wikipedia.org/wiki/Community_wind_energyhttp://en.wikipedia.org/wiki/Community_debate_about_wind_farmshttp://en.wikipedia.org/wiki/Scotlandhttp://en.wikipedia.org/wiki/Canadahttp://en.wikipedia.org/wiki/Angus_Reid_Public_Opinionhttp://en.wikipedia.org/wiki/Battle_of_Trafalgarhttp://en.wikipedia.org/wiki/Cadizhttp://en.wikipedia.org/wiki/Spainhttp://en.wikipedia.org/wiki/File:Public_Opinion_Wind_Farm_Redington_Mountain.jpg


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Wind turbines such as these, in

Cumbria, England, have been opposed

for a number of reasons, including

aesthetics, by some sectors of the

population.[171][172]

the opinions of the broader community.[179]

In America, wind projects are reported to boost local tax bases,

helping to pay for schools, roads and hospitals. Wind projects also

revitalize the economy of rural communities by providing steady

income to farmers and other landowners.[124]

In the UK, both the National Trust and the Campaign to ProtectRural England have expressed concerns about the effects on the rural

landscape caused by inappropriately sited wind turbines and wind

farms.[180][181]

Some wind farms have become tourist attractions. The Whitelee

Wind Farm Visitor Centre has an exhibition room, a learning hub, a caf with a viewing deck and also a shop. It

is run by the Glasgow Science Centre.[182]

In Denmark, a loss-of-value scheme gives people the right to claim compensation for loss of value of their

property if it is caused by proximity to a wind turbine. The loss must be at least 1% of the property's value.[183]

Despite this general support for the concept of wind power in the public at large, local opposition often exists

and has delayed or aborted a number of projects.[184][185][186]

While aesthetic issues are subjective and some find wind farms pleasant and optimistic, or symbols of energy

independence and local prosperity, protest groups are often formed to attempt to block new wind power sites

for various reasons.[178][187][188]

This type of opposition is often described as NIMBYism,[189] but research carried out in 2009 found that there

is little evidence to support the belief that residents only object to renewable power facilities such as windturbines as a result of a "Not in my Back Yard" attitude.[190]

Small-scale wind power

Further information: Microgeneration

Small-scale wind power is the name given to wind generation systems with the capacity to produce up to

50 kW of electrical power.[191] Isolated communities, that may otherwise rely on diesel generators, may use

wind turbines as an alternative. Individuals may purchase these systems to reduce or eliminate their dependenceon grid electricity for economic reasons, or to reduce their carbon footprint. Wind turbines have been used for

household electricity generation in conjunction with battery storage over many decades in remote areas.[23]

Grid-connected domestic wind turbines may use grid energy storage, thus replacing purchased electricity with

locally produced power when available. 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.[192][193]

Off-grid system users can either adapt to intermittent power or use batteries, photovoltaic or diesel systems to

supplement the wind turbine. Equipment such as parking meters, traffic warning signs, street lighting, or wirelessInternet gateways may be powered by a small wind turbine, possibly combined with a photovoltaic system, that

charges a small battery replacing the need for a connection to the power grid. [194]
http://en.wikipedia.org/wiki/Photovoltaichttp://en.wikipedia.org/wiki/Grid_energy_storagehttp://en.wikipedia.org/wiki/Battery_(electricity)http://en.wikipedia.org/wiki/Carbon_footprinthttp://en.wikipedia.org/wiki/Diesel_generatorhttp://en.wikipedia.org/wiki/Microgenerationhttp://en.wikipedia.org/wiki/NIMBYhttp://en.wikipedia.org/wiki/Energy_securityhttp://en.wikipedia.org/wiki/Environmental_effects_of_wind_powerhttp://en.wikipedia.org/wiki/Glasgow_Science_Centrehttp://en.wikipedia.org/wiki/Whitelee_Wind_Farmhttp://en.wikipedia.org/wiki/Campaign_to_Protect_Rural_Englandhttp://en.wikipedia.org/wiki/National_Trusthttp://en.wikipedia.org/wiki/Cumbriahttp://en.wikipedia.org/wiki/File:Wind_tubines_cumbria.JPG


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A 5 kilowatt vertical axis wind turbine

In locations near or around a group of high-rise buildings, wind shear

generates areas of intense turbulence, especially at street-level.[195]

The risks associated with mechanical or catastrophic failure have thus

plagued urban wind development in densely populated areas,

rendering the costs of insuring urban wind systems prohibitive.[196]

Moreover, quantifying the amount of wind in urban areas has been

difficult, as little is known about the actual wind resources of towns

and cities.[197]

A Carbon Trust study into the potential of small-scale wind energy in

the UK, published in 2010, found that small wind turbines could

provide up to 1.5 terawatt hours (TWh) per year of electricity (0.4%

of total UK electricity consumption), saving 0.6 million tonnes of

carbon dioxide (Mt CO2) 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

kWh.[198] A report prepared for the UK's government-sponsored

Energy Saving Trust in 2006, found that home power generators of

various kinds could provide 30 to 40 percent of the country's electricity needs by 2050.[199]

Distributed generation from renewable resources 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.[200]

See also

Airborne wind turbineControlled aerodynamic instability phenomena

Copper in wind power generation

Floating wind turbine

High altitude wind power

Crosswind kite power

List of countries by electricity production from renewable sources

List of energy storage projects

List of wind turbine manufacturers

Design feasibility of Wind turbine systemsLists of offshore wind farms by country

Lists of wind farms by country

Wind turbines on public display

Outline of wind energy

Renewable energy commercialization

Vertical axis wind turbine

Wind-diesel hybrid power system

Wind lens

Wind profiler

Wind rights

Notes
http://en.wikipedia.org/wiki/Wind_rightshttp://en.wikipedia.org/wiki/Wind_profilerhttp://en.wikipedia.org/wiki/Wind_lenshttp://en.wikipedia.org/wiki/Wind-diesel_hybrid_power_systemhttp://en.wikipedia.org/wiki/Vertical_axis_wind_turbinehttp://en.wikipedia.org/wiki/Renewable_energy_commercializationhttp://en.wikipedia.org/wiki/Outline_of_wind_energyhttp://en.wikipedia.org/wiki/Wind_turbines_on_public_displayhttp://en.wikipedia.org/wiki/Lists_of_wind_farms_by_countryhttp://en.wikipedia.org/wiki/Lists_of_offshore_wind_farms_by_countryhttp://en.wikipedia.org/wiki/Design_feasibility_of_Wind_turbine_systemshttp://en.wikipedia.org/wiki/List_of_wind_turbine_manufacturershttp://en.wikipedia.org/wiki/List_of_energy_storage_projectshttp://en.wikipedia.org/wiki/List_of_countries_by_electricity_production_from_renewable_sourceshttp://en.wikipedia.org/wiki/Crosswind_kite_powerhttp://en.wikipedia.org/wiki/High_altitude_wind_powerhttp://en.wikipedia.org/wiki/Floating_wind_turbinehttp://en.wikipedia.org/wiki/Copper_in_renewable_energy#Copper_in_wind_power_generationhttp://en.wikipedia.org/wiki/Controlled_aerodynamic_instability_phenomenahttp://en.wikipedia.org/wiki/Airborne_wind_turbinehttp://en.wikipedia.org/wiki/Utilityhttp://en.wikipedia.org/wiki/Climate_changehttp://en.wikipedia.org/wiki/Renewable_resourcehttp://en.wikipedia.org/wiki/Distributed_generationhttp://en.wikipedia.org/wiki/Energy_Saving_Trusthttp://en.wikipedia.org/wiki/Carbon_Trusthttp://en.wikipedia.org/wiki/Vertical_axis_wind_turbinehttp://en.wikipedia.org/wiki/File:Tassa_5KW_2_ElectronSolarEnergy2.jpg


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1. ^ Wind turbine power output is measured in kilowatts (kW) or megawatts (MW), and energy output in MWh,

GWh, or TWh, Megawatt hours, Gigawatt hours or Terawatt hours. One Gigawatt hour is one million kilowatt

hours, and one Terawatt hour is a billion kilowatt hours.

2. ^ For example, a 1 MW turbine with a capacity factor of 35% will not produce 8,760 MWh in a year (1 24

365), but only 1 0.35 24 365 = 3,066 MWh, averaging to 0.35 MW.

3. ^ California and Minnesota are exceptions.

References

1. ^ Gipe, Paul. The Wind Industry's Experience with Aesthetic Criticism. Leonardo. JSTOR 1575818

(http://www.jstor.org/stable/1575818).

2. ^ Fthenakis, V.; Kim, H. C. (2009). "Land use and electricity generation: A life-cycle analysis". Renewable and

Sustainable Energy Reviews13 (67): 1465. doi:10.1016/j.rser.2008.09.017

(http://dx.doi.org/10.1016%2Fj.rser.2008.09.017).

3. ^ ab REN21 (2011). "Renewables 2011: Global Status Report" (http://germanwatch.org/klima/gsr2011.pdf).

p. 11.

4. ^ ab "International Energy Outlook" (http://www.eia.doe.gov/oiaf/archive/ieo06/special_topics.html). Energy

Information Administration. 2006. p. 66.5. ^ ab Hannele Holttinen, et al. (September 2006). ""Design and Operation of Power Systems with Large

Amounts of Wind Power", IEA Wind Summary Paper"

(http://www.ieawind.org/AnnexXXV/Meetings/Oklahoma/IEA%20SysOp%20GWPC2006%20paper_final.pdf)

(PDF). Global Wind Power Conference 1821 September 2006, Adelaide, Australia.

6. ^ Jo Abbess (28 August 2009). "Claverton-Energy.com" (http://www.claverton-energy.com/wind-energy-

variability-new-reports.html). Claverton-Energy.com. Retrieved 29 August 2010.

7. ^ "Impact of Wind Power Generation in Ireland on the Operation of Conventional Plant and the Economic

Implications"

(http://www.eirgrid.com/media/2004%20wind%20impact%20report%20(for%20updated%202007%20report,

%20see%20above).pdf). eirgrid.com. February 2004. Retrieved 22 November 2010.

8. ^ Reg Platt. Wind power delivers too much to ignore (http://www.newscientist.com/article/mg21729000.200-

wind-power-delivers-too-much-to-ignore.html),New Scientist, 21 January 2013

9. ^ Beyond the Bluster why Wind Power is an Effective Technology Institute for Public Policy Research

August 2012 (http://www.ippr.org/images/media/files/publication/2012/08/beyond-the-

bluster_Aug2012_9564.pdf)

10. ^ Dietrich Lohrmann, "Von der stlichen zur westlichen Windmhle", Archiv fr Kulturgeschichte, Vol. 77,

Issue 1 (1995), pp.130 (10f.)

11. ^ A.G. Drachmann, "Heron's Windmill", Centaurus, 7 (1961), pp. 145151

12. ^ Ahmad Y Hassan, Donald Routledge Hill (1986). Islamic Technology: An illustrated history, p. 54. Cambridge

University Press. ISBN 0-521-42239-6.

13. ^a

b

Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May1991, p. 64-69. (cf. Donald Routledge Hill, Mechanical Engineering

(http://home.swipnet.se/islam/articles/HistoryofSciences.htm))

14. ^ Mark Kurlansky, Salt: a world history,Penguin Books, London 2002 ISBN 0-14-200161-9, pg. 419

15. ^ ab Baker, T. Lindsay. "Brief History of Windmills in the New World"

(http://www.windmillersgazette.com/history.html). Windmillers' Gazette. Retrieved 31 October 2012.

16. ^ "Quirky old-style contraptions make water from wind on the mesas of West Texas"

(http://web.archive.org/web/20100916054539/http://www.mysanantonio.com/news/MYSA092407_01A_State_

windmills_3430a27_html15318.html). Mysanantonio.com. 23 September 2007. Archived from the original

(http://www.mysanantonio.com/news/weather/weatherwise/stories/MYSA092407.01A.State_windmills.3430a2

7.html) on 16 September 2010. Retrieved 29 August 2010.

17. ^ "Windmills in Rural America" (http://www.greenenergyohio.org/page.cfm?pageID=339).Greenenergyohio.org. Retrieved 2013-01-11.

18. ^ ab "World Energy Timeline" (http://danielyergin.com/World-Energy-timeline/). Danielyergin.com. 21

September 2011. Retrieved 2013-01-11.

19. ^ "A surprising history" (http://www.environmentalhistory.org/brilliant/2012/10/29/intro/).
http://www.environmentalhistory.org/brilliant/2012/10/29/intro/http://danielyergin.com/World-Energy-timeline/http://www.greenenergyohio.org/page.cfm?pageID=339http://www.mysanantonio.com/news/weather/weatherwise/stories/MYSA092407.01A.State_windmills.3430a27.htmlhttp://web.archive.org/web/20100916054539/http://www.mysanantonio.com/news/MYSA092407_01A_State_windmills_3430a27_html15318.htmlhttp://www.windmillersgazette.com/history.htmlhttp://en.wikipedia.org/wiki/Special:BookSources/0142001619http://home.swipnet.se/islam/articles/HistoryofSciences.htmhttp://en.wikipedia.org/wiki/Donald_Routledge_Hillhttp://en.wikipedia.org/wiki/Donald_Routledge_Hillhttp://en.wikipedia.org/wiki/Special:BookSources/0521422396http://en.wikipedia.org/wiki/Cambridge_University_Presshttp://en.wikipedia.org/wiki/Donald_Routledge_Hillhttp://en.wikipedia.org/wiki/Ahmad_Y_Hassanhttp://www.ippr.org/images/media/files/publication/2012/08/beyond-the-bluster_Aug2012_9564.pdfhttp://en.wikipedia.org/wiki/New_Scientisthttp://www.newscientist.com/article/mg21729000.200-wind-power-delivers-too-much-to-ignore.htmlhttp://www.eirgrid.com/media/2004%20wind%20impact%20report%20(for%20updated%202007%20report,%20see%20above).pdfhttp://www.claverton-energy.com/wind-energy-variability-new-reports.htmlhttp://www.ieawind.org/AnnexXXV/Meetings/Oklahoma/IEA%20SysOp%20GWPC2006%20paper_final.pdfhttp://en.wikipedia.org/wiki/Energy_Information_Administrationhttp://www.eia.doe.gov/oiaf/archive/ieo06/special_topics.htmlhttp://germanwatch.org/klima/gsr2011.pdfhttp://en.wikipedia.org/wiki/REN21http://dx.doi.org/10.1016%2Fj.rser.2008.09.017http://en.wikipedia.org/wiki/Digital_object_identifierhttp://www.jstor.org/stable/1575818http://en.wikipedia.org/wiki/JSTORhttp://en.wikipedia.org/wiki/Wind_power_in_Minnesotahttp://en.wikipedia.org/wiki/Wind_power_in_Californiahttp://en.wikipedia.org/wiki/Kilowatt_hourhttp://en.wikipedia.org/wiki/Watt


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Environmentalhistory.org. 29 October 2012. Retrieved 2013-01-11.

20. ^ Hardy, Chris (6 July 2010). "Renewable energy and role of Marykirk's James Blyth"

(http://web.archive.org/web/20120314025335/http://www.thecourier.co.uk/Community/Heritage-and-

History/article/2332/renewable-energy-and-role-of-marykirk-s-james-blyth.html). The Courier. D. C. Thomson

& Co. Ltd. Archived from the original (http://www.thecourier.co.uk/Community/Heritage-and-

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12 December 2010.

21. ^ ab Price, Trevor J (3 May 2005). "James Blyth Britain's first modern wind power engineer". Wind

Engineering29 (3): 191200. doi:10.1260/030952405774354921(http://dx.doi.org/10.1260%2F030952405774354921).

22. ^ abc NIxon, Niki (17 October 2008). "Timeline: The history of wind power"

(http://www.guardian.co.uk/environment/2008/oct/17/wind-power-renewable-energy). The Guardian.

Guardian News and Media Limited. Retrieved 10 April 2012.

23. ^ ab Dodge, Darrell M. "Part 2 20th Century Developments" (http://telosnet.com/wind/20th.html). Illustrated

history of wind power development. TelosNet Web Development. Retrieved 10 April 2012.

24. ^ Anon. "The historical development of the wind turbine" (http://www.ivt.ntnu.no/offshore2/?

page_id=266#14).NTNU environmental studies: Wind power. NTNU. Retrieved 7 January 2013.

25. ^ "Enercon E-126 7.5MW still world's biggest" (http://www.windpowermonthly.com/news/1143257/Enercon-

E-126-75MW-worlds-biggest/). Windpowermonthly.com. 1 August 2012. Retrieved 2013-01-11.

26. ^ ab "Harvesting the Wind: The Physics of Wind Turbines"

(https://dspace.lasrworks.org/bitstream/handle/1034

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