Wind farm

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A wind farm is a group of wind turbines in the same location used for production of electric power. 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. A large wind farm may consist of a few dozen to about 100 individual wind turbines, and cover an extended area of hundreds of square miles (square kilometers), but the land between the turbines may be used for agricultural or other purposes. A wind farm may be located off-shore to take advantage of strong winds blowing over the surface of an ocean or lake.

A proposed solution for wind energy and other intermittent power sources is to create a supergrid of interconnected wind farms^[1] across western Europe. This large-scale array of dispersed wind farms^[2] would be located in different wind regimes.

Contents 1 Location planning 1.1 Wind speed 1.2 Altitude 1.3 Wind park effect 1.4 Environmental and esthetic impacts 2 Types 2.1 Onshore 2.2 Near-Shore 2.3 Offshore 2.4 Airborne 3 Capacity by country 4 Wind farms by country 4.1 Australia 4.2 Brazil 4.3 Canada 4.4 European Union 4.5 India 4.6 Japan 4.7 New Zealand 4.8 South Africa 4.9 United States 5 See also 6 References 7 External links

[edit] Location planning

[edit] Wind speed

As a general rule, wind generators are practical where the average wind speed is 10 mph (16 km/h or 4.5 m/s) 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. A vitally important factor of turbine siting is also access to local demand or transmission capacity.

Usually sites are preselected on 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.^[3] To collect wind data a meteorological tower is installed with instruments at various heights along the tower. All towers include anemometers to determine the wind speed and wind vanes to determine the direction. The towers generally vary in height from 30 to 60 meters. The towers primarily are guyed steel-pipe structures which are left to collect data for one to two years and then disassembled. Data is collected by a data logging device which stores and transmits data for analysis. Great attention must be paid to the exact positions of the turbines (a process known as micro-siting) because a difference of 30 m can sometimes double energy production.

[edit] Altitude

The wind blows faster at higher altitudes because of the reduced influence of drag of the surface and lower air viscosity. 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%.

[edit] Wind park effect

Wind farms have many turbines and each extracts some of the energy of the wind. Where land area is sufficient, turbines are spaced three to five rotor diameters apart perpendicular to the prevailing wind, and five to ten rotor diameters apart in the direction of the prevailing wind, to minimize efficiency loss. The "wind park effect" loss can be as low as 2% of the combined nameplate rating of the turbines.

[edit] Environmental and esthetic impacts

See Wind power#environmental effects for a discussion of environmental impacts of wind power. Near-shore and certain inland wind sites may have significant esthetic impact, since the turbines are visible for great distances. Wind farm siting must also consider impacts on wildlife, including migratory animals. Wind project proponents may face opposition from area residents conerened about sound level, light flicker, appearance, and the other impacts of wind turbine placement.

[edit] Types

[edit] Onshore

Onshore turbine installations in hilly or mountainous regions tend to be on ridgelines generally three kilometers or more inland from the nearest shoreline. This is done to exploit the so-called topographic acceleration as the wind accelerates over a ridge. The additional wind speeds gained in this way make large differences to the amount of energy that is produced. Great attention must be paid to the exact positions of the turbines (a process known as micro-siting) because a difference of 30 m can sometimes mean a doubling in output. Local winds are often monitored for a year or more with anemometers and detailed wind maps constructed before wind generators are installed.

For smaller installations where such data collection is too expensive or time consuming, the normal way of prospecting for wind-power sites is to directly look for trees or vegetation that are permanently "cast" or deformed by the prevailing winds. Another way is to use a wind-speed survey map, or historical data from a nearby meteorological station, although these methods are less reliable.

Wind farm siting can sometimes be highly controversial, particularly when sites are picturesque or environmentally sensitive (for instance, having substantial bird life).

[edit] Near-Shore

Near-Shore turbine installations are on land within three kilometers of a shoreline or on water within ten kilometers of land. These areas are good sites for turbine installation, because of wind produced by convection due to differential heating of land and sea each day. Wind speeds in these zones share the characteristics of both onshore and offshore wind, depending on the prevailing wind direction.

Common issues that are shared within near-shore wind development zones are bird migration and nesting, aquatic habitat, transportation (including shipping and boating) and visual aesthetics. Residents near some sites have strongly opposed the installation of wind farms due to these concerns.

[edit] Offshore

Offshore wind development zones are generally considered to be ten kilometers or more from land. Offshore wind turbines are less obtrusive than turbines on land, as their apparent size and noise can be 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 and near-shore locations.

In stormy areas with extended shallow continental shelves (such as Denmark), turbines are practical to install; for example Denmark has many offshore windfarms.^[4]

The United Kingdom plans to use offshore wind turbines to generate enough power to light every home in the U.K. by 2020.^[5]

Locations have begun to be developed in the Great Lakes — with one project by Trillium Power approximately 20 km from shore and over 700 MW in size. Ontario, Canada is pursuing several proposed near-shore locations in fresh water ^[6] and one on the Pacific west coast ^[7].

Offshore installation is more expensive than onshore but this depends on the attributes of the site. Offshore towers are generally taller than onshore towers once the submerged height is included. Offshore foundations may be more expensive to build. Power transmission from offshore turbines is through undersea cable. Offshore installations may use high voltage direct current operation if significant distance is to be covered. Offshore saltwater environments can also raise maintenance costs by corroding the towers, but fresh-water locations such as the Great Lakes do not. Repairs and maintenance are usually more costly than on onshore turbines. Offshore saltwater wind turbines are outfitted with extensive corrosion protection measures like coatings and cathodic protection, which may not be required in fresh water locations.

Offshore wind turbines will probably continue to be the largest turbines in operation, since the high fixed costs of the installation are spread over more energy production, reducing the average cost. Offshore wind farms tend to be quite large, often involving over 100 turbines.

[edit] Airborne

Main article: Airborne wind turbine

Wind turbines might also be flown in high speed winds at altitude, although no such systems are in commercial operation.

[edit] Capacity by country

Wind power capacity installed and under construction by country

Region	Installed Wind Capacity (MW)	Wind Capacity Under Construction (MW)
Australia[8]	817	521
Canada	1856[9]	5474[10]
Europe[11]	48,000
India[12]	7,113.6
New Zealand[13]	320	151
United States	18,303[14]	5736[14]
Total[15]	74,223

[edit] Wind farms by country

Main article: Wind power#Utilization of wind power

See also: Category:Wind power by country

[edit] Australia

Some of the largest wind farms in Australia are:

1. Wattle Point (SA) — 90.75 MW
2. Alinta/Walkaway (WA) — 90 MW
3. Lake Bonney (stage 1) (SA) — 80.5 MW
4. Cathedral Rocks (SA) — 66 MW
5. Emu Downs Wind Farm, Western Australia (WA) — 80 MW

[edit] Brazil

1. São Gonçalo do Amarante/CE (10 Turbines)
2. Prainha de Aquiraz-CE (20 Turbines)
3. Mucuripe-CE (4 Turbines)
4. Fernando de Noronha Island-PE 1&2 (2 Turbines)
5. Olinda-PE 1&2 (2 Turbines)
6. Morro do Camelinho-MG (4 Turbines)
7. Palmas-PR (5 Turbines)
8. Osório-RS (75 Turbines)

[edit] Canada

Main article: List of wind farms in Canada

The total capacity of all wind farms in Canada is approximately 1,856 MW as of January, 2008.^[16] Each province and territory contains the following capacity (rounded to one decimal):

1. Alberta, 524.0 MW,
2. Ontario, 501.3 MW,
3. Quebec, 422.2 MW,
4. Saskatchewan, 171.2 MW,
5. Manitoba, 104.0 MW,
6. Prince Edward Island, 72.4 MW,
7. Nova Scotia, 59.3 MW,
8. Yukon, 0.8 MW, and then
9. Newfoundland and Labrador, 0.4 MW.

There are currently no operating wind farms in British Columbia, New Brunswick, Nunavut (territory), or the Northwest Territories.

The five largest wind farms in Canada are:

1. Prince Project — Phase I&II (Ontario), 189 MW
2. Murdochville Project — Phase I&II&III (Quebec), 162 MW
3. Centennial (SaskPower near Swift Current, Saskatchewan), 149.4 MW
4. Erie Shores (Ontario), 99 MW
5. St Leon — Phase 2 (Manitoba), 84 MW

Government support for wind power continues to increase. The last incentive, the Wind Power Production Incentive ended on March 31, 2007 (WPPI)^[17], and future projects are part of its new Ecoenergy set of programs, ecoEnergy for Renewable Power^[18]. There is an additional 5826 MW planned or under construction.

[edit] European Union

Main article: Wind power in the European Union

The development of wind farms in Europe enjoys greater public acceptance and creates a larger share of energy. Germany has the biggest wind turbine to be established offshore, and the largest number of wind farms in the world. Its installed capacity was 20,622 MW as of December 2006. The second country in capacity was Spain with 11,615 MW. The third one was Denmark with 3,136 MW. Italy was in the fourth position, with 2,123 MW.^[19]

Overall national government policies across Europe are also generally in favour of increasing the use of renewable energy sources. The United Kingdom government, for example, has a target for 10% of domestic energy consumption to be generated from renewable sources by the year 2010. A number of on- and off-shore wind farms are currently going through planning permission at the moment. Recently an onshore farm was opened at Cefn Croes in West Wales's Cambrian Mountains. In May 2006, operational wind farms in wind farms in the UK comprised an installed capacity of 1693 MW, in Portugal 1188 MW,^[20] in France 918 MW and in the Republic of Ireland 496 MW. The planned 322 MW wind farm south of Glasgow will be the biggest wind farm in Europe. The €350 million farm is ordered by Scottish Power and the 140 wind turbines are to be delivered by Siemens.

On 18 December 2006, the British government gave planning consent for the world's largest offshore wind farm, the 'London Array'. It is to be built 12 miles off of the Kent coast and will include 341 turbines.

Wind farms in different countries yield different amounts of electricity, because of differences in prevailing wind patterns, siting of the turbines, and the fact that early turbine designs were considerably less efficient and capable of adapting quickly to changes in wind direction and speed. For example, an Oxford University study of the wind over the past 35 years found that UK turbines would have produced 27% of their peak power generating capacity, compared with 20% in Denmark and 15% in Germany.^[21]

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" of interconnected wind farms ^[22] 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.^[23] The idea is that by the time a low pressure area has moved away from Denmark to the Baltic Sea the next low appears of 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. Such a supergrid would therefore reduce the need for backup capacity.

[edit] India

Main article: Wind power in India

At the end of September 2007, India had 7660.2 MW of wind generating capacity and is the fourth largest market in the world.^[24] Indian Wind Energy Association has estimated that with the current level of technology, the ‘on-shore’ potential for utilization of wind energy for electricity generation is of the order of 65,000 MW.^[25] There are about a dozen wind pumps of various designs providing water for agriculture, afforestation, and domestic purposes, all scattered over the country. The wind farms are predominantly present in the states of Tamil Nadu, Maharashtra, Karnataka and Gujarat. Other states like Andhra Pradesh, Rajasthan, Kerala and Madhya Pradesh have a very good potential.

[edit] Japan

There is no particular controversy about the sightliness or otherwise of the Wakamatsu ward windfarm in Kitakyushu, as there is in some other countries. It is far from the scenic areas of Wakamatsu, and on windy reclaimed land. Asahi Shimbun reported on May 18, 2005 that many utilities have put limits on the amount of wind power they will allow, because of lack of confidence in their ability to deal with the variable output. It should be noted that several European countries are successfully accommodating significantly higher shares of wind energy in to their networks and that the Japanese grid is capable of coping with large conventional power stations disconnecting unexpectedly due to faults; on the other hand, it is true that integrating windpower or unreliable conventional power stations in to island grids is more difficult than into continent-wide inter-connected grids.

[edit] New Zealand

New Zealand is located in the northern latitudes of the 'roaring 40s' — an abundant wind energy resource. Genesis Energy built the Hau Nui wind farm in 1996 and is located south east of Martinborough on the coastal road to White Rock. The Brooklyn Wind Turbine was installed on the top of a hill in Brooklyn, Wellington in March 1993 as part of a research project commissioned by the now defunct Electricity Corporation of New Zealand. Meridian Energy recently applied for, and obtained with conditions, resource consent to build a consignment of wind farms in the rural Makara Hill area west of Wellington. Meridian Energy have finished the Te Apiti Wind Farm on the Ruahine Ranges. It can be seen clearly at Ashhurst near Palmerston North. The Te Rere Hau Wind Farm is under construction nearby. Meridian Energy's White Hill wind farm at Mossburn in the South Island, reached full capacity in 2007. TrustPower purchased the Tararua wind farm, located on the Tararua Ranges behind Palmerston North, from Tararua Wind Power Limited. As of September 2007 this was New Zealand's largest wind farm, with an installed capacity of 161MW, half of the country's total installed capacity. Applications for resource content have been submitted for several new wind farms, with a total potential capacity of 1900MW as of late 2007.

[edit] South Africa

The first commercial wind farm in South Africa 13km's outside Darling in the Western Cape on farm Windhoek, was opened on the 23rd of May 2008. The first phase consists of four 1.3MW turbines supplied by Fuhrlander, Germany. The total power generated estimated at 5.2MW will be put into the national grid at 66kV. It has taken the developer Herman Oelsner 10 years to achieve his dream of being the first privatised wind farm in South Africa. There has been enormous concerns regarding environmental and aviation some of which still need to be resolved. DWP ( Darling Wind Power ) will be responsible for the maintenance and upkeep of the wind farm under a watchful eye from Germany. Various stake holders from international to Local have invested in the project which could only benefit an already over extended power producer in South Africa namely Eskom.

Additionally, Klipheuwel wind farm, the first wind farm in sub-Saharan Africa, comprises three turbines – a Vestas V66 with 1.75 MW output, a Vestas V47 with 660 kW output and a Jeumont J48 with 750 kW output, giving a total output of almost 3.2 MW.

[edit] United States

Main article: Wind power in the United States

The United States has the third most installed capacity of wind power in the world, after Germany and Spain. As of January 2008, its wind farms had a combined capacity of 16,818 MW.^[14] Historically, the rise of wind farms in the US began in the late 1970s when the US government implemented favorable tax policies for wind investors as a reaction to the energy crisis of that era. Subsequent variability over time of the availability of government incentives, combined with an easing of energy costs led to an extended stagnation in the US wind energy industry in the following decades. In the mid-2000s, however, higher energy prices combined with an increase in demand for green energy (driven in large part by policy setting at the state level — such as the creation of statewide Renewable Portfolio Standards — in the absence of any materially significant or coordinated federal response to global warming) to result in unprecedented and accelerating growth in new wind development.

Currently, the largest wind farm in the US – and the largest in the world – is Florida Power & Light's Horse Hollow Wind Energy Center, located in Taylor County, Texas. The Horse Hollow project operates 421 wind turbines and has a capacity of 735 megawatts.^[26] Prior to Horse Hollow's completion, the largest US wind farm was the Stateline Wind Project on the Oregon-Washington line, with a peak capacity of 300 megawatts. Three California wind "farms" arguably have greater combined capacity than the Stateline farm, but are actually collections of dozens of individual wind farms. The California farms have many different owners and turbine types and have been constructed, retrofitted and occasionally dismantled since they were first installed in late 1982. As of 2005, all three of these areas are seeing renewed growth. Primarily, the older and smaller wind turbines are being replaced with much larger, more efficient models. Some of the workhorses of the past were only 65 kilowatts (kW) in capacity or even smaller, though some were several hundred kW. Today, the smallest utility-scale wind turbines are about 700 kW, with a few models approaching 5,000 kW (5 MW). Secondarily, non-functional turbines are also being returned to service.

Northern California is home to one of the earliest large wind farms. An advantage of the Altamont Pass Wind Farm is that under hot inland (Central Valley) conditions, a thermal low is developed that brings in cool coastal marine air, driving the turbines at a time of maximum electricity demand. However, this phenomenon is not always reliable and with an inland high pressure condition the entire region can be both hot and windless. At this time additional power must be provided by natural gas-powered gas turbine peaker plants. Solano County has one of the five major wind farms in California and has integrated the most advanced wind power technology anywhere in the United States. From 2003 to 2006, dozens of state-of-the-art turbines were installed at the Montezuma Hills near the Sacramento River delta. Eight of the turbines, at 415 feet tall, are the largest in the United States--and are 110 feet taller than the Statue of Liberty. These 3-megawatt Vestas wind turbines each produce enough power to meet the annual needs of more than 1,000 households.

Even though California has some of the largest wind farms in the U.S., it does not have very many commercially viable wind farm sites, at least not onshore. Much of the Southwest is not much better, although there are some significant exceptions. The Great Plains states have an abundance of suitable sites for wind energy development^[27] however the region's potential is still largely untapped. Iowa and Minnesota are leading the Midwest in the development of wind energy with their combined capacities expected to reach 2,000 MW in 2007. The Pacific Northwest and the Northeast both have many excellent sites as well. In contrast, the Southeast has a very poor wind energy resource, though the Appalachian Mountains do provide a few good areas.

[edit] See also

• Intermittent power source
• Electrical generator
• Net metering
• Wind power
• Value of wind
• Wind turbine
• Wind power in the United Kingdom
• Wave farm
• Category:Wind power by country
• List of large wind farms

[edit] References

[edit] External links

The external links in this article may not follow Wikipedia's content policies or guidelines. Please improve this article by removing excessive or inappropriate external links.

• Wind Over Water — a documentary film about the Cape Wind Project a proposed wind farm in Massachusetts, US.
• Altahullion Wind farm A Quicktime VR panorama illustrating the scale of the largest wind farm in Ireland
• Wind power
• MySME.deInformation on Wind Farm Development in Germany
• Offshorewind.net — Offshore wind energy information.
• www.world-wind.energy.info — Basic information of wind energy utilisation (technology, planning a wind farm, grid integration etc.), presented by the World Wind Energy Association
• American Wind Energy Association. An association promoting wind power growth through advocacy and education.
• Pictures of a Wind Farm being deployed
• National Wind Watch — A coalition of US wind power opposition groups.
• Chanson, Hubert (2004). Wind Farms in Brittany (Bretagne), France. Shore and Beach, 72 3: 15-16
• Wind Farm Buffets Family, Town Relations by David Baron. Retrieved on 2008-04-09.