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A wind turbine is a device that wind power the kinetic energy of wind into electrical energy. , hundreds of thousands of large turbines, in installations known as , were generating over 650 of power, with 60 GW added each year. Wind turbines are an increasingly important source of intermittent renewable energy, and are used in many countries to lower energy costs and reduce reliance on . One study claimed that, wind had the "lowest relative greenhouse gas emissions, the least water consumption demands and the most favorable social impacts" compared to photovoltaic, hydroelectricity, geothermal power, coal power and gas energy sources.
Smaller wind turbines are used for applications such as battery charging and remote devices such as traffic warning signs. Larger turbines can contribute to a domestic power supply while selling unused power back to the utility supplier via the electrical grid.
Wind are manufactured in a wide range of sizes, with either horizontal or vertical axes, though horizontal is most common.
Wind power first appeared in Europe during the Middle Ages. The first historical records of their use in England date to the 11th and 12th centuries; there are reports of German crusades taking their windmill-making skills to Syria around 1190. (2025). 9780333792483, Palgrave/UNEP. ISBN 9780333792483 By the 14th century, Dutch windmills were in use to drain areas of the Rhine delta. Advanced wind turbines were described by Croatian inventor Fausto Veranzio in his book Machinae Novae (1595). He described vertical axis wind turbines with curved or V-shaped blades.
The first electricity-generating wind turbine was installed by the Josef Friedländer at the Vienna International Electrical Exhibition in 1883. It was a Halladay windmill for driving a dynamo. Friedländer's diameter Halladay "wind motor" was supplied by U.S. Wind Engine & Pump Co. of Batavia, Illinois. The windmill drove a dynamo at ground level that fed electricity into a series of Electric battery. The batteries powered various electrical tools and lamps, as well as a threshing machine. Friedländer's windmill and its accessories were prominently installed at the north entrance to the main exhibition hall ("Rotunde") in the Prater.
In July 1887, Scottish academic James Blyth installed a battery-charging machine to light his holiday home in Marykirk, Scotland. Some months later, American inventor Charles F. Brush was able to build the first automatically operated wind turbine after consulting local University professors and his colleagues Jacob S. Gibbs and Brinsley Coleberd and successfully getting the blueprints peer-reviewed for electricity production. Although Blyth's turbine was considered uneconomical in the United Kingdom, electricity generation by wind turbines was more cost effective in countries with widely scattered populations.
In Denmark by 1900, there were about 2500 windmills for mechanical loads such as pumps and mills, producing an estimated combined peak power of about 30 megawatts (MW). The largest machines were on towers with four-bladed diameter rotors. By 1908, there were 72 wind-driven electric generators operating in the United States from 5 kilowatts (kW) to 25 kW. Around the time of World War I, American windmill makers were producing 100,000 farm windmills each year, mostly for water-pumping.
By the 1930s, use of wind turbines in rural areas was declining as the distribution system extended to those areas.
A forerunner of modern horizontal-axis wind generators was in service at Yalta, USSR, in 1931. This was a 100 Kilowatt generator on a tower, connected to the local 6.3 kV distribution system. It was reported to have an annual capacity factor of 32 percent, not much different from current wind machines.
In the autumn of 1941, the first megawatt-class wind turbine was synchronized to a utility grid in Vermont. The Smith–Putnam wind turbine only ran for about five years before one of the blades snapped off. The unit was not repaired, because of a shortage of materials during the war.
The first utility grid-connected wind turbine to operate in the UK was built by John Brown & Company in 1951 in the Orkney.
In the early 1970s, however, anti-nuclear protests in Denmark spurred artisan mechanics to develop microturbines of 22 Kilowatt despite declines in the industry. Organizing owners into associations and co-operatives led to the lobbying of the government and utilities and provided incentives for larger turbines throughout the 1980s and later. Local activists in Germany, nascent turbine manufacturers in Spain, and large investors in the United States in the early 1990s then lobbied for policies that stimulated the industry in those countries. (2025). 9781118794180 ISBN 9781118794180
It has been argued that expanding the use of wind power will lead to increasing geopolitical competition over critical materials for wind turbines, such as rare earth elements neodymium, praseodymium, and dysprosium. However, this perspective has been critically dismissed for failing to relay how most wind turbines do not use permanent magnets and for underestimating the power of economic incentives for the expanded production of these minerals.
Wind turbines are classified by the wind speed they are designed for, from class I to class III, with A to C referring to the turbulence intensity of the wind. (2025). 9781118900116, Wind Resource Assessment and Micro-siting, Science and Engineering. ISBN 9781118900116
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The maximum theoretical power output of a wind machine is thus times the rate at which kinetic energy of the air arrives at the effective disk area of the machine. If the effective area of the disk is A, and the wind velocity v, the maximum theoretical power output P is:
where ρ is the air density.
Wind-to-rotor efficiency (including rotor blade friction and drag) are among the factors affecting the final price of wind power. Further inefficiencies, such as gearbox, generator, and converter losses, reduce the power delivered by a wind turbine. To protect components from undue wear, extracted power is held constant above the rated operating speed as theoretical power increases as the cube of wind speed, further reducing theoretical efficiency. In 2001, commercial utility-connected turbines delivered 75% to 80% of the Betz limit of power extractable from the wind, at rated operating speed.
Efficiency can decrease slightly over time, one of the main reasons being dust and insect carcasses on the blades, which alter the aerodynamic profile and essentially reduce the lift to drag ratio of the airfoil. Analysis of 3128 wind turbines older than 10 years in Denmark showed that half of the turbines had no decrease, while the other half saw a production decrease of 1.2% per year.
In general, more stable and constant weather conditions (most notably wind speed) result in an average of 15% greater efficiency than that of a wind turbine in unstable weather conditions, thus allowing up to a 7% increase in wind speed under stable conditions. This is due to a faster recovery wake and greater flow entrainment that occur in conditions of higher atmospheric stability. However, wind turbine wakes have been found to recover faster under unstable atmospheric conditions as opposed to a stable environment.
Different materials have varying effects on the efficiency of wind turbines. In an Ege University experiment, three wind turbines, each with three blades with a diameter of one meter, were constructed with blades made of different materials: A glass and glass/carbon epoxy, glass/carbon, and glass/polyester. When tested, the results showed that the materials with higher overall masses had a greater friction moment and thus a lower power coefficient.
The air velocity is the major contributor to the turbine efficiency. This is the reason for the importance of choosing the right location. The wind velocity will be high near the shore because of the temperature difference between the land and the ocean. Another option is to place turbines on mountain ridges. The higher the wind turbine will be, the higher the wind velocity on average. A windbreak can also increase the wind velocity near the turbine.
Most horizontal axis turbines have their rotors upwind of the supporting tower. (2025). 9780128148815 ISBN 9780128148815 Downwind machines have been built, because they don't need an additional mechanism for keeping them in line with the wind. In high winds, downwind blades can also be designed to bend more than upwind ones, which reduces their swept area and thus their wind resistance, mitigating risk during gales. Despite these advantages, upwind designs are preferred, because the pulsing change in loading from the wind as each blade passes behind the supporting tower can cause damage to the turbine.
Turbines used in for commercial production of electric power are usually three-bladed. These have low torque ripple, which contributes to good reliability. The blades are usually colored white for daytime visibility by aircraft and range in length from . The size and height of turbines increase year by year. Offshore wind turbines are built up to 8 megawatt today and have a blade length up to . Designs with 10 to 12 MW were in preparation in 2018, and a "15 MW+" prototype with three blades was planned to be constructed as of 2022. The average hub height of horizontal axis wind turbines is 90 meters.
Vertical turbine designs have much lower efficiency than standard horizontal designs.Hau, E., Wind Turbines: Fundamentals, Technologies, Application, Economics. Springer. Germany. 2006 The key disadvantages include the relatively low rotational speed with the consequential higher torque and hence higher cost of the drive train, the inherently lower power coefficient, the 360-degree rotation of the aerofoil within the wind flow during each cycle and hence the highly dynamic loading on the blade, the pulsating torque generated by some rotor designs on the drive train, and the difficulty of modelling the wind flow accurately and hence the challenges of analysing and designing the rotor prior to fabricating a prototype.
When a turbine is mounted on a rooftop the building generally redirects wind over the roof and this can double the wind speed at the turbine. If the height of a rooftop mounted turbine tower is approximately 50% of the building height it is near the optimum for maximum wind energy and minimum wind turbulence. While wind speeds within the built environment are generally much lower than at exposed rural sites, noise may be a concern and an existing structure may not adequately resist the additional stress.
Subtypes of the vertical axis design include:
Twisted Savonius is a modified savonius, with long helical scoops to provide smooth torque. This is often used as a rooftop wind turbine and has even been adapted for ships.
A 1.5 (megawatt) wind turbine of a type frequently seen in the United States has a tower high. The rotor assembly (blades and hub) measures about in diameter. The nacelle, which contains the generator, is and weighs around 300 tons.
As of 2021, the longest blade was , producing 15 MW.
Blades usually last around 20 years, the typical lifespan of a wind turbine.
Carbon fiber has more tensile strength, higher stiffness and lower density than glass fiber. An ideal candidate for these properties is the spar cap, a structural element of a blade that experiences high tensile loading. A glass fiber blade could weigh up to , while using carbon fiber in the spar saves 20% to 30% weight, about .
For the wind turbine blades, while the material cost is much higher for hybrid glass/carbon fiber blades than all-glass fiber blades, labor costs can be lower. Using carbon fiber allows simpler designs that use less raw material. The chief manufacturing process in blade fabrication is the layering of plies. Thinner blades allow reducing the number of layers and thus the labor and in some cases, equate to the cost of labor for glass fiber blades.
Offshore has significantly higher installation costs.
Modern turbines use a couple of tons of copper for generators and cables and such.Frost and Sullivan, 2009, cited in Wind Generator Technology, by Eclareon S.L., Madrid, May 2012; www.eclareon.com; Available at Leonardo Energy – Ask an Expert; , global production of wind turbines use of copper per year.
A 2011 study by the United States Geological Survey estimated resources required to fulfill the US commitment to supplying 20% of its electricity from wind power by 2030. It did not consider requirements for small turbines or offshore turbines because those were not common in 2008 when the study was done. Common materials such as cast iron, steel and concrete would increase by 2%–3% compared to 2008. Between 110,000 and 115,000 metric tons of fiber glass would be required per year, a 14% increase. Rare-earth metal use would not increase much compared to available supply, however rare-earth metals that are also used for other technologies such as batteries which are increasing its global demand need to be taken into account. Land required would be 50,000 square kilometers onshore and 11,000 offshore. This would not be a problem in the US due to its vast area and because the same land can be used for farming. A greater challenge would be the variability and transmission to areas of high demand.
Permanent magnets for wind turbine generators contain rare-earth metals such as neodymium (Nd), praseodymium (Pr), terbium (Tb), and dysprosium (Dy). Systems that use magnetic direct drive turbines require greater amounts of rare-earth metals. Therefore, an increase in wind turbine manufacture would increase the demand for these resources. By 2035, the demand for Nd is estimated to increase by 4,000 to 18,000 tons and for Dy by 200 to 1,200 tons. These values are a quarter to half of current production. However, these estimates are very uncertain because technologies are developing rapidly.
Reliance on rare earth minerals for components has risked expense and price volatility as China has been main producer of rare earth minerals (96% in 2009) and was reducing its export quotas. However, in recent years, other producers have increased production and China has increased export quotas, leading to higher supply, lower cost, and greater viability of large-scale use of variable-speed generators.
Glass fiber is the most common material for reinforcement. Its demand has grown due to growth in construction, transportation and wind turbines. Its global market might reach US$17.4 billion by 2024, compared to US$8.5 billion in 2014. In 2014, Asia Pacific produced more than 45% of the market; now China is the largest producer. The industry receives subsidies from the Chinese government allowing it to export cheaper to the US and Europe. However, price wars have led to anti-dumping measures such as tariffs on Chinese glass fiber.
The Bahrain World Trade Center is an example of wind turbines displayed prominently for the public. It is the first skyscraper to integrate wind turbines into its design
Research by John Dabiri of Caltech suggests that vertical wind turbines may be placed much more closely together so long as an alternating pattern of rotation is created allowing blades of neighbouring turbines to move in the same direction as they approach one another.
Modern turbines usually have a small onboard crane for hoisting maintenance tools and minor components. However, large, heavy components like generators, gearboxes, blades, and so on are rarely replaced, and a Mobile crane is needed in those cases. If the turbine has a difficult access road, a Liftra can be lifted up by the internal crane to provide heavier lifting.
Interest in recycling blades varies in different markets and depends on the waste legislation and local economics. A challenge in recycling blades is related to the composite material, which is made of fiberglass with carbon fibers in epoxy resin, which cannot be remolded to form new composites.
Wind farm waste is less toxic than other garbage. Wind turbine blades represent only a fraction of overall waste in the US, according to the wind-industry trade association, American Wind Energy Association.
Several utilities, startup companies, and researchers are developing methods for reusing or recycling blades. Manufacturer Vestas has developed technology that can separate the fibers from the resin, allowing for reuse. In Germany, wind turbine blades are commercially recycled as part of an alternative fuel mix for a cement factory. In the United Kingdom, a project will trial cutting blades into strips for use as rebar in concrete, with the aim of reducing emissions in the construction of High Speed 2. Used wind turbine blades have been recycled by incorporating them as part of the support structures within pedestrian bridges in Poland and Ireland.
Wind turbines provide a clean energy source, use little water, emitting no greenhouse gases and no waste products during operation. Over of carbon dioxide per year can be eliminated by using a one-megawatt turbine instead of one megawatt of energy from a fossil fuel.
Environmental impact of wind power includes effect on wildlife, but can be mitigated if proper strategies are implemented. Thousands of birds, including rare species, have been killed by the blades of wind turbines, though wind turbines contribute relatively insignificantly to anthropogenic avian mortality (birds killed by humans). Wind farms and nuclear power plants are responsible for between 0.3 and 0.4 bird deaths per gigawatt-hour (GWh) of electricity while fossil fuel power stations are responsible for about 5.2 fatalities per GWh. In comparison, conventional coal-fired generators contribute significantly more to bird mortality. A study on recorded bird populations in the United States from 2000 to 2020 found the presence of wind turbines had no significant effect on bird population numbers.
Energy harnessed by wind turbines is variable, and is not a "dispatchable" source of power; its availability is based on whether the wind is blowing, not whether electricity is needed. Turbines can be placed on or bluffs to maximize the access of wind they have, but this also limits the locations where they can be placed. In this way, wind energy is not a particularly reliable source of energy. However, it can form part of the energy mix, which also includes power from other sources. Technology is also being developed to store excess energy, which can then make up for any deficits in supplies.
Wind turbines have blinking lights that warn aircraft, to avoid collisions. Residents living near windfarms, especially those in rural areas, have complained that the blinking lights are a bothersome form of light pollution. A light mitigation approach involves Aircraft Detection Lighting Systems (ADLSs) by which the lights are turned on, only when the ADLS's radar detects aircraft within thresholds of altitude and distance.
Hybrid reinforcements
Instead of making wind turbine blade reinforcements from pure glass or pure carbon, hybrid designs trade weight for cost. For example, for an blade, a full replacement by carbon fiber would save 80% of weight but increase costs by 150%, while a 30% replacement would save 50% of weight and increase costs by 90%. Hybrid reinforcement materials include E-glass/carbon, E-glass/aramid. The current longest blade by LM Wind Power is made of carbon/glass hybrid composites. More research is needed about the optimal composition of materials.
Nano-engineered polymers and composites
Additions of small amount (0.5 weight %) of nanoreinforcement (carbon nanotubes or nanoclay) in the polymer matrix of composites, fiber sizing or inter-laminar layers can improve fatigue resistance, shear or compressive strength, and fracture toughness of the composites by 30% to 80%. Research has also shown that incorporating small amounts of carbon nanotubes (CNT) can increase the lifetime up to 1500%. (2025). 9781538682715 ISBN 9781538682715
Costs
, the capital cost of a wind turbine was around $1 million per megawatt of nameplate capacity, though this figure varies by location; for example, such numbers ranged from a half million in South America to $1.7 million in Asia.
Non-blade materials
Wind turbine parts other than the rotor blades (including the rotor hub, gearbox, frame, and tower) are largely made of steel. Smaller turbines (as well as megawatt-scale Enercon turbines) have begun using aluminum alloys for these components to make turbines lighter and more efficient. This trend may grow if fatigue and strength properties can be improved.
Pre-stressed concrete has been increasingly used for the material of the tower, but still requires much reinforcing steel to meet the strength requirement of the turbine. Additionally, step-up gearboxes are being increasingly replaced with variable speed generators, which requires magnetic materials.
Material supply
A 2015 study of the material consumption trends and requirements for wind energy in Europe found that bigger turbines have a higher consumption of precious metals but lower material input per Kilowatt generated. The material consumption and stock at that time was compared to input materials for various onshore system sizes. In all EU countries, the estimates for 2020 doubled the values consumed in 2009. These countries would need to expand their resources to meet the estimated demand for 2020. For example, the EU had 3% of world supply of fluorspar, and it would require 14% by 2020. Globally, the main exporting countries are South Africa, Mexico, and China. This is similar with other critical and valuable materials required for energy systems such as magnesium, silver and indium. The levels of recycling of these materials are very low, and focusing on that could alleviate supply. Because most of these valuable materials are also used in other emerging technologies, like light emitting diodes (LEDs), photo voltaics (PVs) and liquid crystal displays (LCDs), their demand is expected to grow.
Wind turbines on public display
A few localities have exploited the attention-getting nature of wind turbines by placing them on public display, either with visitor centers around their bases, or with viewing areas farther away. The wind turbines are generally of conventional horizontal-axis, three-bladed design and generate power to feed electrical grids, but they also serve the unconventional roles of technology demonstration, public relations, and education.
Small wind turbines
Small wind turbines may be used for a variety of applications including on- or off-grid residences, telecom towers, offshore platforms, rural schools and clinics, remote monitoring and other purposes that require energy where there is no electric grid, or where the grid is unstable. Small wind turbines may be as small as a fifty-watt generator for boat or Travel trailer use. Hybrid solar- and wind-powered units are increasingly being used for traffic signage, particularly in rural locations, since they avoid the need to lay long cables from the nearest mains connection point. The U.S. Department of Energy's National Renewable Energy Laboratory (NREL) defines small wind turbines as those smaller than or equal to 100 kilowatts. Small Wind , U.S. Department of Energy National Renewable Energy Laboratory website Small units often have direct-drive generators, direct current output, aeroelastic blades, and lifetime bearings and use a vane to point into the wind.
Wind turbine spacing
On most horizontal wind turbine farms, a spacing of about 6–10 times the rotor diameter is often upheld. However, for large wind farms, distances of about 15 rotor diameters should be more economical, taking into account typical wind turbine and land costs. This conclusion has been reached by research conducted by Charles Meneveau of Johns Hopkins University and Johan Meyers of Leuven University in Belgium, based on computer simulations that take into account the detailed interactions among wind turbines (wakes) as well as with the entire turbulent atmospheric boundary layer.
Operability
Maintenance
Wind turbines need regular maintenance to stay reliable and available. In the best case turbines are available to generate energy 98% of the time. Ice accretion on turbine blades has been found to greatly reduce the efficiency of wind turbines, which is a common challenge in cold climates where in-cloud icing and freezing rain events occur. Deicing is mainly performed by internal heating or in some cases, by helicopters spraying clean warm water on the blades.
Repowering
Installation of new wind turbines can be controversial. An alternative is repowering, where existing wind turbines are replaced with bigger, more powerful ones, sometimes in smaller numbers while keeping or increasing capacity.
Demolition and recycling
Some wind turbines which are out of use are recycling or repowered. 85% of turbine materials are easily reused or recycled, but the blades, made of a composite material, are more difficult to process.
Comparison with other power sources
Advantages
Wind turbines is one of the lowest-cost sources of renewable energy along with . As technology needed for wind turbines continued to improve, the prices decreased as well. In addition, there is currently no competitive market for wind energy (though there may be in the future), because wind is a freely available natural resource, most of which is untapped. The main cost of small wind turbines is the purchase and installation process, which averages between $48,000 and $65,000 per installation. Usually, the total amount of energy harvested amounts to more than the cost of the turbines.
Disadvantages
Wind turbines can be very large, reaching over tall with blades long, and people have often complained about their visual impact.
Records
See also List of most powerful wind turbines
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!Record
!Model/Name
!Location
!Constructor/Manufacturer Largest and most powerful MYSE18.X-20MW Hainan, China Mingyang Wind Power Largest vertical-axis Éole Cap-Chat, Quebec, Canada NRC, Hydro-Québec Largest 1-blade turbine Monopteros M50 Jade Wind Park MBB Messerschmitt Largest 2-blade turbine SCD6.5 Longyuan Wind Farm Mingyang Wind Power Most rotors Four-in-One Maasvlakte, Netherlands Lagerwey Highest-situated 2.5 Pastoruri Glaicer WindAid Largest offshore MySE18.X-20MW Hainan, China Mingyang Wind Power Tallest Schipkau GICON Wind Turbine Schipkau, Germany Vensys, GICON
See also
Further reading
External links
target="_blank" rel="nofollow"> Harvesting the Wind (45 lectures about wind turbines by professor Magdi Ragheb
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