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A wind farm or wind park is a group of wind turbines in the same location used to produce energy. A large wind farm may consist of several hundred individual wind turbines and cover an extended area of hundreds of square miles, but the land between the turbines may be used for agricultural or other purposes. A wind farm can also be located offshore.
Many of the largest operational onshore wind farms are located in the United States and China. For example, the Gansu Wind Farm in China has a capacity of over 5,000 MW of power with a goal of 20,000 MW by 2020. The Alta Wind Energy Center in California, United States is the largest onshore wind farm outside of China, with a capacity of 1,020 MW. As of April 2013, the 630 MW London Array in the UK is the largest offshore wind farm in the world, followed by the 504 MW Greater Gabbard wind farm in the UK.
As a general rule, economic wind generators require windspeed of 16 km/h (10 mph) or greater. An ideal location would have a near constant flow of non-turbulent wind throughout the year, with a minimum likelihood of sudden powerful bursts of wind. An important factor of turbine siting is also access to local demand or transmission capacity.
Usually sites are screened on the basis of a wind atlas, and validated with wind measurements. Meteorological wind data alone is usually not sufficient for accurate siting of a large wind power project. Collection of site specific data for wind speed and direction is crucial to determining site potential in order to finance the project. Local winds are often monitored for a year or more, and detailed wind maps constructed before wind generators are installed.
The wind blows faster at higher altitudes because of the reduced influence of drag. The increase in velocity with altitude is most dramatic near the surface and is affected by topography, surface roughness, and upwind obstacles such as trees or buildings. Typically, the increase of wind speeds with increasing height follows a wind profile power law, which predicts that wind speed rises proportionally to the seventh root of altitude. Doubling the altitude of a turbine, then, increases the expected wind speeds by 10%, and the expected power by 34%.
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. Construction of a land-based wind farm requires installation of the collector system and substation, and possibly access roads to each turbine site.
|Alta (Oak Creek-Mojave)||1,320||United States|||
|Jaisalmer Wind Park||1,064||India|||
|Buffalo Gap Wind Farm||523.3||United States|||
|Capricorn Ridge Wind Farm||662.5||United States|||
|Dabancheng Wind Farm||500||People's Republic of China|||
|Fântânele-Cogealac Wind Farm||600||Romania|||
|Fowler Ridge Wind Farm||599.8||United States|||
|Horse Hollow Wind Energy Center||735.5||United States|||
|Meadow Lake Wind Farm||500||United States|||
|Panther Creek Wind Farm||458||United States|||
|Roscoe Wind Farm||781.5||United States|||
|Shepherds Flat Wind Farm||845||United States|
|Sweetwater Wind Farm||585.3||United States|||
Onshore turbine installations in hilly or mountainous regions tend to be on ridgelines generally three kilometres or more inland from the nearest shoreline. This is done to exploit the topographic acceleration as the wind accelerates over a ridge. The additional wind speeds gained in this way can increase energy produced because more wind goes through the turbines. The exact position of each turbine matters, because a difference of 30m could potentially double output. This careful placement is referred to as 'micro-siting'.
Europe is the leader in offshore wind energy, with the first offshore wind farm being installed in Denmark in 1991. As of 2010, there are 39 offshore wind farms in waters off Belgium, Denmark, Finland, Germany, Ireland, the Netherlands, Norway, Sweden and the United Kingdom, with a combined operating capacity of 2,396 MW. More than 100 GW (or 100,000 MW) of offshore projects are proposed or under development in Europe. The European Wind Energy Association has set a target of 40 GW installed by 2020 and 150 GW by 2030.
|Country||Turbines & model||Commissioned||Refs|
|London Array||630||United Kingdom||175 × Siemens SWT-3.6||2013|||
|Greater Gabbard wind farm||504||United Kingdom||140 × Siemens SWT-3.6||2012|||
|Anholt||400||Denmark||111 × Siemens|
|BARD Offshore 1||400||Germany||80 × BARD 5.0||2013|||
|Walney||367||United Kingdom||102 × Siemens SWT-3.6||2012|||
|Thorntonbank||325||Belgium||6 × 5MW REpower|
and 48 × 6.15MW REpower
|Sheringham Shoal||315||United Kingdom||88 × Siemens|
|Thanet||300||United Kingdom||100 × Vestas V90-3MW||2010|||
|Lincs||270||United Kingdom||75 × 3.6MW||2013|||
|Horns Rev II||209||Denmark||91 × Siemens 2.3–93||2009|||
Offshore wind turbines are less obtrusive than turbines on land, as their apparent size and noise is mitigated by distance. Because water has less surface roughness than land (especially deeper water), the average wind speed is usually considerably higher over open water. Capacity factors (utilisation rates) are considerably higher than for onshore locations.
The province of Ontario in Canada is pursuing several proposed locations in the Great Lakes, including the suspended Trillium Power Wind 1 approximately 20 km from shore and over 400 MW in size. Other Canadian projects include one on the Pacific west coast.
As of 2010, there are no offshore wind farms in the United States. However, projects are under development in wind-rich areas of the East Coast, Great Lakes, and Pacific coast.
Installation and service / maintenance of off-shore wind farms are a specific challenge for technology and economic operation of a wind farm. Service vessels have to be operated nearly 24/7 (availability higher than 80% of time) to get sufficient amortisation from the wind turbines. Therefore special fast service vehicles for installation (like Wind Turbine Shuttle) as well as for maintenance (including heave compensation and heave compensated working platforms to allow the service staff to enter the wind turbine also at difficult weather conditions) are required. So-called inertial and optical based Ship Stabilization and Motion Control systems (iSSMC) are used for that.
There exist also some wind parks, which were mainly built for testing wind turbines. In such wind parks, there is usually from each type to be tested only a single wind turbine. Such parks have usually at least one meteorological tower. An example of an experimental wind park is Østerild Wind Turbine Test Field.
For some time, airborne wind farms have been discussed. Airborne wind farm is a group of airborne wind energy systems in the same location, connected to the grid in the same point.
|Collgar Wind Farm||206||UBS Investment Bank &|
Retail Employees Superannuation Trust
|Capital Wind Farm||140.7||Infigen Energy||New South Wales|
|Hallett Group||298||AGL Energy||South Australia|
|Lake Bonney Wind Farm||278||Infigen Energy||South Australia|
|Waubra Wind Farm||192||Acciona Energy &|
ANZ Infrastructure Services
|Woolnorth Wind Farm||140||Roaring 40s & Hydro Tasmania||Tasmania|
|Anse-à-Valleau Wind Farm||100||Gaspé||Quebec|
|Caribou Wind Park||99||70 km west of Bathurst||New Brunswick|
|Bear Mountain Wind Park||120||Dawson Creek||British Columbia|
|Centennial Wind Power Facility||150||Swift Current||Saskatchewan|
|Enbridge Ontario Wind Farm||181||Kincardine||Ontario|
|Erie Shores Wind Farm||99||Port Burwell||Ontario|
|Jardin d'Eole Wind Farm||127||Saint-Ulric||Quebec|
|Kent Hills Wind Farm||96||Riverside-Albert||New Brunswick|
|Melancthon EcoPower Centre||199||Melancthon||Ontario|
|Port Alma Wind Farm||101||Chatham-Kent||Ontario|
|Chatham Wind Farm||101||Chatham-Kent||Ontario|
|Prince Township Wind Farm||189||Sault Ste. Marie||Ontario|
|St. Joseph Wind Farm||138||Montcalm||Manitoba|
|St. Leon Wind Farm||99||St. Leon||Manitoba|
|Wolfe Island Wind Project||197||Frontenac Islands||Ontario|
In just five years, China leapfrogged the rest of the world in wind energy production, going from 2,599 MW of capacity in 2006 to 62,733 MW at the end of 2011. However, the rapid growth outpaced China's infrastructure and new construction slowed significantly in 2012.
At the end of 2009, wind power in China accounted for 25.1 gigawatts (GW) of electricity generating capacity, and China has identified wind power as a key growth component of the country's economy. With its large land mass and long coastline, China has exceptional wind resources. Researchers from Harvard and Tsinghua University have found that China could meet all of their electricity demands from wind power by 2030.
By the end of 2008, at least 15 Chinese companies were commercially producing wind turbines and several dozen more were producing components. Turbine sizes of 1.5 MW to 3 MW became common. Leading wind power companies in China were Goldwind, Dongfang Electric, and Sinovel along with most major foreign wind turbine manufacturers. China also increased production of small-scale wind turbines to about 80,000 turbines (80 MW) in 2008. Through all these developments, the Chinese wind industry appeared unaffected by the global financial crisis, according to industry observers.
According to the Global Wind Energy Council, the development of wind energy in China, in terms of scale and rhythm, is absolutely unparalleled in the world. The National People's Congress permanent committee passed a law that requires the Chinese energy companies to purchase all the electricity produced by the renewable energy sector.
|This article is outdated. (June 2012)|
The European Union has a total installed wind capacity of 93,957 MW. Germany has the third largest capacity in the world (after China and the United States) with an installed capacity was 29,060 MW at the end of 2011, and Spain has 21,674 MW. Italy and France each had between 6,000 and 7,000 MW. By January 2014, the UK installed capacity was 10,495 MW. But energy production can be different from capacity – in 2010, Spain had the highest European wind power production with 43 TWh compared to Germany's 35 TWh.
Europe's largest windfarm is the 'London Array', an off-shore wind farm in the Thames Estuary in the United Kingdom, with a current capacity of 630 MW (and thus the world's largest off-shore wind farm). Other large wind farms in Europe include Fântânele-Cogealac Wind Farm near Constanța, Romania with 600 MW capacity, and Whitelee Wind Farm near Glasgow, Scotland which has a total capacity of 539 MW.
An important limiting factor of wind power is variable power generated by wind farms. In most locations the wind blows only part of the time, which means that there has to be back-up capacity of conventional generating capacity to cover periods that the wind is not blowing. To address this issue it has been proposed to create a "supergrid" to connect national grids together across western Europe, ranging from Denmark across the southern North Sea to England and the Celtic Sea to Ireland, and further south to France and Spain especially in Higueruela which was considered for some time the biggest wind farm in the world. The idea is that by the time a low pressure area has moved away from Denmark to the Baltic Sea the next low appears off the coast of Ireland. Therefore, while it is true that the wind is not blowing everywhere all of the time, it will always be blowing somewhere.
India has the fifth largest installed wind power capacity in the world. As of 31 March 2014, the installed capacity of wind power was 21136.3 MW mainly spread across Tamil Nadu state (7253 MW). Wind power accounts nearly 8.5% of India's total installed power generation capacity, and it generates 1.6% of the country's power.
Pakistan is developing wind power plants in Jhimpir, Gharo, Keti Bandar and Bin Qasim in Sindh. The government of Pakistan decided to develop wind power energy sources due to problems supplying energy to the southern coastal regions of Sindh and Balochistan. The Jhimpir Wind Power Plant is the first wind power plant in Pakistan. The wind farm is being developed in Jhimpir, by Zorlu Energy Pakistan the local subsidiary of a Turkish company. The total cost of project is $136 million. Completed in 2002, it has a total capacity of 50MW. Fauji Fertilizer Company Energy Limited, is building 49.5 MW wind Energy Farm at Jhimpir near Karachi. Contract of supply of mechanical design was awarded to Nordex and Descon Engineering Limited. Nordex a German wind turbine manufacturer. In the end of 2011 49.6 MW will be completed.Pakistani Govt. also has issued LOI of 100 MW Wind power plant to FFCEL. Pakistani Govt. has plans to achieve electric power up to 2500 MW by the end of 2015 from wind energy to bring down energy shortage.
According to a USAID report, Pakistan has the potential of producing 150,000 megawatts of wind energy, of which only the Sindh corridor can produce 40,000 megawatts.
Sri Lanka has received funding from the Asian Development Bank amounting to $300 million to invest in renewable energies. From this funding as well as $80 million from the Sri Lankan Government and $60 million from France’s Agence Française de Développement, Sri Lanka is building two 100MW wind farms from 2017 due to be completed by late 2020 in Northern Sri Lanka.
|This article is outdated. (May 2014)|
There are currently no large scale wind farms operational in South Africa, though a number are in the initial planning stages. Most of these are earmarked for locations along the Eastern Cape coastline. Eskom has constructed one small scale prototype windfarm at Klipheuwel in the Western Cape and another demonstrator site is near Darling with phase 1 completed. The first commercial wind farm, Coega Wind Farm in Port Elisabeth, was developed by the Belgian company Electrawinds.
|Coega Wind Farm||Eastern Cape||2010||1.8 (45)||Operational|||
|Darling Wind Farm||Western Cape||2008||5.2 (13.2)||Under construction|||
|Klipheuwel Wind Farm||Western Cape||2002||3.16||Operational (Prototype/Research)|||
|Sere Wind Farm||Western Cape||2012||(100)||Funding phase|||
New installations place the U.S. on a trajectory to generate 20% of the nation’s electricity by 2030 from wind energy. Growth in 2008 channeled some $17 billion into the economy, positioning wind power as one of the leading sources of new power generation in the country, along with natural gas. Wind projects completed in 2008 accounted for about 42% of the entire new power-producing capacity added in the U.S. during the year.
At the end of 2008, about 85,000 people were employed in the U.S. wind industry, and GE Energy was the largest domestic wind turbine manufacturer. Wind projects boosted local tax bases and revitalized the economy of rural communities by providing a steady income stream to farmers with wind turbines on their land. Wind power in the U.S. provides enough electricity to power the equivalent of nearly 9 million homes, avoiding the emissions of 57 million tons of carbon each year and reducing expected carbon emissions from the electricity sector by 2.5%.
Texas, with 10,929 MW of capacity, has the most installed wind power capacity of any U.S. state, followed by California with 4,570 MW and Iowa with 4,536 MW. The Alta Wind Energy Center (1,020 MW) in California is the nation's largest wind farm in terms of capacity. Altamont Pass Wind Farm is the largest wind farm in the U.S. in terms of the number of individual turbines.
Typically wind farms are designated to agricultural settings, though construction relies on support and consent from the land owners. This brings up one of the biggest factors inhibiting wind farm production: human opposition. Opposition to wind farm development is typically associated with the concept of NIMBY (Not In My Back Yard). In a study done by Theresa Groth and Christine Vogt, townships and counties were surveyed independently regarding thoughts about wind farm development. Overall, it was found that “turbine placement close to residents may heighten their uncertainty and concern of the wind turbines and overshadow any positive inclinations towards the development.” Belief factors scrutinized under the study fell under the economic, environmental, and social categories. Actual energy output/savings were never touched upon.
The emphasis placed on the factors associated with NIMBY has led to wind farm development being primarily in the domain of landscape assessment and environmental impact when seeking farm sites. The viability and efficiency of the wind farm are barely touched upon, instead falling to the developer. For example, Sturge et al. of the University of Sheffield wrote that in many countries where wind energy is becoming popular, engineering aspects, specifically energy yield are not being taken into consideration, either by the public or in the process of planning consent for wind farm development. As energy is the main purpose of wind farms, a lack of attention given to the subject could be detrimental to the general acceptance of wind farms.
Compared to the environmental impact of traditional energy sources, the environmental impact of wind power is relatively minor. Wind power consumes no fuel, and emits no air pollution, unlike fossil fuel power sources. The energy consumed to manufacture and transport the materials used to build a wind power plant is equal to the new energy produced by the plant within a few months. While a wind farm may cover a large area of land, many land uses such as agriculture are compatible, with only small areas of turbine foundations and infrastructure made unavailable for use.
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 or may not be significant, depending on specific circumstances. Prevention and mitigation of wildlife fatalities, and protection of peat bogs, affect the siting and operation of wind turbines. Deaths by collision with wind turbines must also be compared with alternatives, for example one company reported 20 eagle deaths by wind turbines and 232 by power lines for coal plants.
There have been anecdotal reports of negative effects from noise on people who live very close to wind turbines, however this has not been supported by reliable peer-reviewed research.
A 2007 report by the U.S. National Research Council noted that noise produced by wind turbines is generally not a major concern for humans beyond a half-mile or so. Low-frequency vibration and its effects on humans are not well understood and sensitivity to such vibration resulting from wind-turbine noise is highly variable among humans. There are opposing views on this subject, and more research needs to be done on the effects of low-frequency noise on humans.
In a 2009 report about "Rural Wind Farms", a Standing Committee of the Parliament of New South Wales, Australia, recommended a minimum setback of two kilometres between wind turbines and neighbouring houses (which can be waived by the affected neighbour) as a precautionary approach.
Utility-scale wind farms must have access to transmission lines to transport energy. The wind farm developer may be obliged to install extra equipment or control systems in the wind farm to meet the technical standards set by the operator of a transmission line. The company or person that develops the wind farm can then sell the power on the grid through the transmission lines and ultimately chooses whether to hold on to the rights or sell the farm or parts of it to big business like GE, for example.
Wind farms can interfere with ground radar systems used for defense, weather and air traffic control. The large, rapidly moving blades of the turbines can return signals to the radar that can be mistaken as an aircraft or weather pattern. Actual aircraft and weather patterns around wind farms can be accurately detected, as there is no fundamental physical constraint preventing that. But ageing radar infrastructure is significantly challenged with the task. The US military is using wind turbines on some bases, including Barstow near the radar test facility.
The level of interference is a function of the signal processors used within the radar, the speed of the aircraft and the relative orientation of wind turbines/aircraft with respect to the radar. An aircraft flying above the wind farm's turning blades could become impossible to detect because the blade tips can be moving at nearly aircraft velocity. Studies are currently being performed to determine the level of this interference and will be used in future site planning. Issues include masking (shadowing), clutter (noise), and signal alteration. Radar issues have stalled as much as 10,000 MW of projects in USA.
Some very long range radars are not affected by wind farms.
Permanent problem solving include a non-initiation window to hide the turbines while still tracking aircraft over the wind farm, and a similar method mitigates the false returns. England's Newcastle Airport is using a short-term mitigation; to "blank" the turbines on the radar map with a software patch. Wind turbine blades using stealth technology are being developed to mitigate radar reflection problems for aviation. As well as stealth windfarms, the future development of infill radar systems could filter out the turbine interference.
In early 2011, the U.S. government awarded a program to build a radar/wind turbine analysis tool. This tool will allow developers to predict the impact of a wind farm on a radar system before construction, thus allowing rearrangement of the turbines or even the entire wind farm to avoid negative impacts on the radar system.
A mobile radar system, the Lockheed Martin TPS-77, has shown in recent tests that it can distinguish between aircraft and wind turbines, and more than 170 TPS-77 radars are in use around the world. In Britain, the Lockheed Martin TPS-77 system was to be installed at Trimingham in Norfolk to remove military objections to a series of offshore wind farms in the North Sea. A second TPS-77 was to be installed in the Scottish Borders, overcoming objections to a 48-turbine wind farm at Fallago.
A 2010 study found that in the immediate vicinity of wind farms, the climate is cooler during the day and slightly warmer during the night than the surrounding areas due to the turbulence generated by the blades.
In another study an analysis carried out on corn and soybean crops in the central areas of the United States noted that the microclimate generated by wind turbines improves crops as it prevents the late spring and early autumn frosts, and also reduces the action of pathogenic fungi that grow on the leaves. Even at the height of summer heat, the lowering of 2.5–3 degrees above the crops due to turbulence caused by the blades, can make a difference for the cultivation of corn.
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