Wind turbine: Difference between revisions
←Replaced page with 'Wind turbines are GAY. Shoutout to you Rudy.... too bad about those maple leafs.' |
m Reverting possible vandalism by 72.139.130.50 to version by Wtshymanski. False positive? Report it. Thanks, User:ClueBot. (294061) (Bot) |
||
Line 1: | Line 1: | ||
{{WindTurbineSegments}} |
|||
Wind turbines are GAY. |
|||
[[Image:Turbine aalborg.jpg|thumb|right|Wind turbines near [[Aalborg]], [[Denmark]]. For scale, a standard doorway can be seen at the base of the pylon.]] |
|||
A '''wind turbine''' is a rotating machine that converts the [[kinetic energy]] in [[wind]] into [[mechanical energy]]. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a '''[[windmill]]'''. If the mechanical energy is then converted to [[electric power|electricity]], the machine is called a '''wind generator''', '''wind turbine''', '''wind power unit (WPU)''' or '''wind energy converter (WEC)''' . |
|||
Shoutout to you Rudy.... too bad about those maple leafs. |
|||
This article discusses electric power generation machinery. [[Windmill]] discusses machines used for grain-grinding,water pumping, etc. The article on [[wind power]] describes turbine placement, economics, public concerns, and controversy. The [[Wind power#Wind energy|wind energy]] section of that article describes the distribution of wind energy over time, and how that affects wind-turbine design. See [[environmental concerns with electricity generation#Wind power|environmental concerns with electricity generation]] for discussion of environmental problems with wind-energy production. |
|||
==History== |
|||
{{Main|History of wind power}} |
|||
[[Image:Wind turbine 1941.jpg|thumb|right|The world's first [[watt|megawatt]] wind turbine at [[Castleton, Vermont]]]] |
|||
Wind machines were used for grinding grain in Persia as early as 200 B.C. This type of machine was introduced into the [[Roman Empire]] by 250 A.D. By the 14th century Dutch [[windmill]]s were in use to drain areas of the [[Rhine River]] delta. 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 MW. The first windmill for electricity production was built in [[Cleveland, Ohio]] by Charles F Brush in 1888, and in 1908 there were 72 wind-driven electric generators from 5 kW to 25 kW. The largest machines were on 24 m (79 ft) towers with four-bladed 23 m (75 ft) diameter rotors. Around the time of World War I, American windmill makers were producing 100,000 farm windmills each year, most for water-pumping.<ref name="Aermotor">[http://www.mysanantonio.com/news/weather/weatherwise/stories/MYSA092407.01A.State_windmills.3430a27.html Quirky old-style contraptions make water from wind on the mesas of West Texas]</ref> |
|||
By the 1930s windmills for electricity were common on farms, mostly in the United States where distribution systems had not yet been installed. In this period, high-tensile steel was cheap, and windmills were placed atop prefabricated open steel lattice towers. |
|||
A forerunner of modern horizontal-axis wind generators was in service at [[Yalta]], [[USSR]] in 1931. This was a 100 kW generator on a 30 m (100 ft) tower, connected to the local 6.3 kV distribution system. It was reported to have an annual [[capacity factor]] of 32 per cent, not much different from current wind machines. |
|||
The very first electricity generating windmill operated in the UK was a battery charging machine installed in 1887 by James Blyth in Scotland. The first utility grid-connected wind turbine operated in the UK was built by the John Brown Company in 1954 in the Orkney Islands. It had an 18 metre diameter, three-bladed rotor and a rated output of 100 kW. |
|||
== Potential turbine power == |
|||
{{main|Wind turbine design}} |
|||
[[Image:Wind power coeff.jpg|right|thumb|Wind Turbine Power Coefficent]] |
|||
The amount of [[Power (physics)|power]] transferred to a wind turbine is directly proportional to the density of the air, the area swept out by the rotor, and the cube of the wind speed. |
|||
The usable power <math>P</math> available in the wind is given by: |
|||
: <math>P = \begin{matrix}\frac{1}{2}\end{matrix}\alpha\rho\pi r^2 v^3</math>, |
|||
where P = power in watts, ''α'' = an [[energy efficiency|efficiency]] factor determined by the design of the turbine, ''ρ'' = mass density of air in kilograms per cubic meter, ''r'' = radius of the wind turbine in meters, and ''v'' = velocity of the air in meters per second.<ref> [http://www.energy.iastate.edu/Renewable/wind/wem/windpower.htm Iowa Energy Center Wind Energy Manual].</ref> |
|||
As the wind turbine extracts energy from the air flow, the air is slowed down, which causes it to spread out. [[Albert Betz]], a German physicist, determined in 1919 (see [[Betz' law]]) that a wind turbine can extract at most 59% of the energy that would otherwise flow through the turbine's cross section, that is ''α'' can never be higher than 0.59 in the above equation. The Betz limit applies regardless of the design of the turbine. |
|||
This equation shows the effects of the mass rate of flow of air travelling through the turbine, and the energy of each unit mass of air flow due to its velocity. As an example, on a cool 15 °C (59 °F) day at sea level, air density is 1.225 kilograms per cubic metre. An 8 m/s (28.8 km/h or 18 mi/h) breeze blowing through a 100 meter diameter rotor would move almost 77,000 kilograms of air per second through the swept area. The total power of the example breeze through a 100 meter diameter rotor would be about 2.5 megawatts. Betz' law states that no more than 1.5 megawatts could be extracted. |
|||
==Types of wind turbines== |
|||
Wind turbines can be separated into two types based by the axis in which the turbine rotates. Turbines that rotate around a horizontal axis are more common. Vertical-axis turbines are less frequently used. |
|||
===Horizontal axis=== |
|||
Horizontal-axis wind turbines(HAWT) have the main [[rotor]] shaft and [[electrical generator]] at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple [[wind vane]], while large turbines generally use a wind sensor coupled with a [[servo motor]]. Most have a [[gearbox]], which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive a [[generator]]. |
|||
Since a tower produces [[turbulence]] behind it, the turbine is usually pointed upwind of the tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed a considerable distance in front of the tower and are sometimes tilted up a small amount. |
|||
Downwind machines have been built, despite the problem of turbulence, because they don't need an additional mechanism for keeping them in line with the wind, and because in high winds, the blades can be allowed to bend which reduces their swept area and thus their wind resistance. Since turbulence leads to fatigue failures, and reliability is so important, most HAWTs are upwind machines. |
|||
====HAWT Subtypes==== |
|||
There are several types of HAWT: |
|||
[[Image:Doesburgermolen.jpg|thumb|right|Doesburger windmill, Ede, [[The Netherlands]]]] |
|||
; Windmills : These squat structures, typically (at-least) four-bladed, usually with wooden shutters or fabric sails, were developed in Europe. These [[windmill]]s were pointed into the wind manually or via a tail-fan and were typically used to grind grain. In [[the Netherlands]] they were also used to pump water from low-lying land, and were instrumental in keeping its [[polder]]s dry. Windmills were also located throughout the USA, especially in the Northeastern region. |
|||
; Modern Rural Windmills : |
|||
The Eclipse windmill factory was set up around 1866 in Beloit, Wisconsin and soon became a huge success building mills for farm water pumping and railroad tank filling. Other firms like Star, Dempster, and Aeromotor also entered the market. Hundreds of thousands of these mills were produced before rural electrification and small numbers continue to be made.<ref name= "Aermotor"/> They typically had many blades, operated at ''tip speed ratios'' (defined below) not better than one, and had good starting torque. Some had small direct-current generators used to charge storage batteries, to provide a few lights, or to operate a radio receiver. The American [[Rural Electrification Administration|rural electrification]] connected many farms to centrally-generated power and replaced individual windmills as a primary source of farm power by the 1950's. They were also produced in other countries like South Africa and Australia (where an American design was copied in 1876<ref>Extract from |
|||
''Triumph of the Griffiths Family'', http://au.geocities.com/ozwindmills/SouthernCross.htm, Bruce Millett, 1984, accessed January 26, 2008</ref>). Such devices are still used in locations where it is too costly to bring in commercial power. |
|||
[[Image:Hassloch-pfalz westernmill 20060429 387 part.jpg|thumb|right|Water pumping rural windmill in [[Germany]].]] |
|||
In [[Schiedam]], the [[Netherlands]], a traditional style windmill (the ''Noletmolen'') was built in 2005 to generate electricity.<ref name=Nolet>[http://www.molendatabase.nl/nederland/molen_e.php?nummer=1280 Molendatabase] Dutch text</ref> The mill is one of the tallest [[Tower mill]]s in the world, being some {{convert|42.5|m|ft}} tall. |
|||
; Common modern wind turbines : |
|||
Turbines used in wind farms for commercial production of electric power are usually three-bladed and pointed into the wind by computer-controlled motors. This type is produced by Danish and other manufacturers. These have high tip speeds of up to six times the wind speed, high efficiency, and low torque ripple which contributes to good reliability. The blades are usually colored light gray to blend in with the clouds and range in length from 20 to 40 metres (65 to 130 ft) or more. The tubular steel towers range from about 200 to 300 feet (60 to 90 metres) high. The blades rotate at 10-22 revolutions per minute,<ref>[http://www.gepower.com/prod_serv/products/wind_turbines/en/15mw/specs.htm 1.5 MW Wind Turbine Technical Specifications]</ref><ref>[http://www.aweo.org/windmodels.html Size specifications of common industrial wind turbines]</ref> and a gear box steps up the speed of the generator. Some models operate at constant speed, but more energy can be collected by variable-speed turbines which use a solid-state power converter to interface to the transmission system. All turbines are equipped with high wind shut down features to avoid over speed damage. |
|||
====HAWT advantages==== |
|||
* Blades are to the side of the turbine's center of gravity, helping stability. |
|||
* Ability to wing warp, which gives the turbine blades the best angle of attack. Allowing the angle of attack to be remotely adjusted gives greater control, so the turbine collects the maximum amount of wind energy for the time of day and season. |
|||
* Ability to pitch the rotor blades in a storm, to minimize damage. |
|||
* Tall tower allows access to stronger wind in sites with wind shear. In some wind shear sites, every ten meters up, the wind speed can increase by 20% and the power output by 34%.. |
|||
====HAWT disadvantages==== |
|||
* HAWTs have difficulty operating in near ground, turbulent winds. |
|||
* The tall towers and long blades up to 90 meters long are difficult to transport on the sea and on land. Transportation can now cost 20% of equipment costs. |
|||
* Tall HAWTs are difficult to install, needing very tall and expensive cranes and skilled operators. |
|||
* The FAA has raised concerns about tall HAWTs effects on radar near Air Force bases. |
|||
* Their height can create local opposition based on impacts to viewsheds. |
|||
* Downwind variants suffer from fatigue and structural failure caused by turbulence. |
|||
====Cyclic stresses and vibration==== |
|||
[[Cyclic stress]]es fatigue the blade, [[axle]] and [[Bearing (mechanical)|bearing]] material failures were a major cause of turbine failure for many years. Because wind velocity often increases at higher altitudes, the backward force and torque on a horizontal-axis wind turbine (HAWT) blade peaks as it turns through the highest point in its circle. The tower hinders the airflow at the lowest point in the circle, which produces a local dip in force and torque. These effects produce a cyclic twist on the main bearings of an HAWT. The combined twist is worst in machines with an even number of blades, where one is straight up when another is straight down. To improve reliability, teetering hubs have been used which allow the main shaft to rock through a few degrees, so that the main bearings do not have to resist the torque peaks. |
|||
When the turbine turns to face the wind, the rotating blades act like a [[gyroscope]]. As it pivots, [[gyroscopic precession]] tries to twist the turbine into a forward or backward somersault. For each blade on a wind generator's turbine, precessive force is at a minimum when the blade is horizontal and at a maximum when the blade is vertical. This cyclic twisting can quickly fatigue and crack the blade roots, hub and axle of the turbines. |
|||
===Vertical axis=== |
|||
'''[[Vertical-axis wind turbine]]s''' (or VAWTs) have the rotor shaft arranged vertically . VAWTs are usally situated closer to the ground since they can utilise turbulent winds , also , the air has a higher density at low altitude and therfore carries more energy at a given wind speed . |
|||
====VAWT subtypes==== |
|||
[[Image:Darrieus-windmill.jpg|thumb|right|30 m [[Darrieus wind turbine]] in the [[Magdalen Islands]]]] |
|||
; [[Darrieus wind turbine]] : "Eggbeater" turbines. They have good efficiency, but produce large torque ripple and cyclic stress on the tower, which contributes to poor reliability. Also, they generally require some external power source, or an additional Savonius rotor, to start turning, because the starting torque is very low. The torque ripple is reduced by using 3 or more blades which results in a higher solidity for the rotor. Solidity is measured by blade area over the rotor area. Newer Darrieus type turbines are not held up by guy wires but have an external superstructure connected to the top bearing. |
|||
; [[Gorlov helical turbine]] : Essentially a darrieus turbine in a [[helix|helical]] configuration. Patented in 2001. It solves most of the problems of the Darrieus rotor. It is self-starting, has lower torque ripple, low vibration and noise, and low cyclic stress. High reliability is expected from tested or matured designs. At least two wind turbine products are on the market as of 2007, including the [[Turby wind turbine]] and the [[Quietrevolution wind turbine]]. Most importantly, the GHT is an excellent turbine for zero-head [[hydropower]], and appears to be a much needed ecologically benign and affordable solution for [[micro-hydro]]power. It is up to 35% efficient, which is competitive with the most efficient VAWT's. |
|||
; [[Giromill]]: A subtype of Darrieus turbine with straight, as opposed to curved, blades. The cycloturbine variety have variable pitch to reduce the torque pulsation and are self-starting [http://www.awea.org/faq/vawt.html]. The advantages of variable pitch are: high starting torque; a wide, relatively flat torque curve; a lower blade speed ratio; a higher coefficient of performance; more efficient operation in turbulent winds; and a lower blade speed ratio which lowers blade bending stresses. Straight, V, or curved blades may be used. Recently , this type of turbine has been advanced by former Russian rocket scientists who claim to have increased the efficiency of the VAWT up to 38% . A company , SRC Vertical Ltd.[http://www.eng.src-vertical.com/] has been formed , and has begun selling the new turbine . |
|||
[[Image:Windlahor.jpg|thumb|right|12 m [[Windmill with rotational sails]] in the [[Osijek]], [[Croatia]]]] |
|||
; [[Savonius wind turbine]] : These are drag-type devices with two- (or more) scoops that are used in anemometers, the ''Flettner'' vents (commonly seen on bus and van roofs), and in some high-reliability low-efficiency power turbines. They are always self-starting if there are at least three scoops. They sometimes have long helical scoops to give a smooth torque. The Banesh rotor and especially the Rahai rotor improve efficiency with blades shaped to produce significant lift as well as drag. A [http://www.wipo.int/pctdb/en/wo.jsp?wo=2001077523 new variety] uses sails that can open or close with changes in wind speed. |
|||
====VAWT advantages==== |
|||
* Can be easier to maintain if the moving parts are located near the ground. This is due to the shape of some VAWTs , the airfoils or rotor blades are connected by arms to a shaft that sits on a bearing and drives a generator below, usually by first connecting to a gearbox. |
|||
* As the rotor blades are vertical, a yaw device is not needed, reducing the need for this bearing and its cost. |
|||
* VAWTs have a higher airfoil pitch angle, giving improved aerodynamics while decreasing drag at low and high pressures. |
|||
* Straight bladed VAWT designs with a square or rectangular crossection have a larger swept area for a given diameter than the circular swept area of HAWTs . |
|||
* Mesas, hilltops, ridgelines and passes can have faster more powerful winds near the ground because the wind is forced up a slope or funnelled into a pass and into the path of VAWTs situated close to the ground . |
|||
* Low height useful where laws do not permit structures to be placed high. |
|||
* Does not need a free standing tower so is much less expensive and stronger in high winds that are close to the ground. |
|||
* Usually have a lower [[Tip speed ratio|Tip-Speed ratio]] so less likely to break in high winds. |
|||
* Does not need to turn to face the wind if the wind direction changes making them ideal in turbulent wind conditions . |
|||
* They can potentially be built to a far larger size than HAWT's , for instance floating VAWT's hundreds of meters in diameter where the entire vessel rotates , can eliminate the need for a large and expensive bearing . |
|||
* Newer carbon composite blades are lightweight and easier to install. |
|||
====VAWT disadvantages==== |
|||
* Most VAWTs produce energy at only 50% of the efficiency of HAWTs in large part because of the additional drag that they have as their blades rotate into the wind. This can be overcome by using structures to funnel more and align the wind into the rotor (e.g. "stators" on early Windstar turbines) or the "vortex" effect of placing straight bladed VAWTs closely together (e.g. Patent # 6784566). |
|||
* There may be a height limitation to how tall a vertical wind turbine can be built and how much sweep area it can have. However , this can be overcome by connecting a multiple number of turbines together in a triangular pattern with bracing across the top of the structure . Thus reducing the need for such strong vertical support , and allowing the turbine blades to be made much longer . |
|||
* Most VAWTS need to be installed on a relatively flat piece of land and some sites could be too steep for them but are still usable by HAWTs. |
|||
* Most VAWTs have low starting torque, and may require energy to start the turning. |
|||
* A VAWT that uses guy wires to hold it in place puts stress on the bottom bearing as all the weight of the rotor is on the bearing. Guy wires attached to the top bearing increase downward thrust in wind gusts. Solving this problem requires a superstructure to hold a top bearing in place to eliminate the downward thrusts of gust events in guy wired models. |
|||
* While VAWTs' parts are located on the ground, they are also located under the weight of the structure above it, which can make changing out parts near impossible without dismantling the structure if not designed properly. |
|||
[[Image: Windmills at Lackawanna, New York.jpg|thumb|right|Wind turbines on the [[Lake Erie]] shore at [[Lackawanna, New York]] ]] |
|||
==Locations== |
|||
{{main|Wind power}} |
|||
Wind turbines can also be classified by the location in which they are to be used. Onshore, offshore, or even aerial wind turbines have unique design characteristics, which are explained in more detail in the section on [[#Turbine design and construction|turbine design and construction]]. |
|||
==Turbine design and construction== |
|||
{{Main|Wind turbine design}} |
|||
Wind turbines are designed to exploit the wind energy that exists at a location. Aerodynamic modeling is used to determine the optimum tower height, control systems, number of blades, and blade shape. |
|||
Virtually all modern wind turbines convert wind energy to electricity for energy distribution. As described, the modern wind turbine is a system that comprises three integral components with distinct disciplines of engineering science. The rotor component, which is approximately 20% of the wind turbine cost, includes the blades for converting wind energy to an intermediate low speed rotational energy. The generator component, which is approximately 34% of the wind turbine cost, includes the [[electrical generator]], the control electronics, and most likely a gearbox component for converting the low speed rotational energy to electricity. The structural support component, which is approximately 15% of the wind turbine cost, includes the tower for optimally situating the rotor component to the wind energy source.<ref>"Wind Turbine Design Cost and Scaling Model," Technical Report NREL/TP-500-40566, December, 2006, page 35,36. http://www.nrel.gov/docs/fy07osti/40566.pdf</ref> |
|||
==Special wind turbines== |
|||
{{Main|Special wind turbines}} |
|||
One E-66 wind turbine at [[Windpark Holtriem]], Germany carries an observation deck, open for visitors to see. Another turbine of the same type, with an observation deck, is located in [[Swaffham]], [[England]]. |
|||
A series of lighter-than-air wind turbines are in development in Canada by Magenn Power. They deliver power to the ground by a tether system.<ref>[http://www.magenn.com/technology.php Magenn Power Inc. - Technology<!-- Bot generated title -->]</ref> |
|||
Wind turbines may also be used in conjunction with a large vertical [[solar updraft tower]] to extract the energy due to air heated by the Sun. |
|||
[[Variable pitch]] wind turbines are another special (yet low-cost) design. Designs such as the [[Jacobs]] are said to be inexpensive, highly efficient and usable in diy-construction. <ref>[http://www.rebelwolf.com/essn/ESSN-Aug2005.pdf Jacobs wind turbine (page 18)]</ref> |
|||
==Small wind turbines== |
|||
Small wind turbines may be as small as a four hundred watt generators for residential use. The small ones often have direct drive generators, [[direct current]] output, aeroelastic blades, lifetime bearings and use a vane to point into the wind. Larger, more costly turbines generally have geared power trains, alternating current output, flaps and are actively pointed into the wind. Direct drive generators and aeroelastic blades for large wind turbines are being researched. |
|||
A small wind turbine can be installed on a roof. Installation issues then include the strength of the roof, vibration, and the turbulence caused by the roof ledge. A small-scale, rooftop wind turbine is said to be able to generate power from 10% to up to 25% of the electricity requirements of a regular house. <ref>[http://www.timesonline.co.uk/tol/news/uk/article706123.ece Rooftop wind turbines able to power up to 25% of domestic energy requirements]</ref> |
|||
[[Image:Wind-power-small-scale.jpg|thumb|left|Small-scale wind power in rural Indiana.]] |
|||
Small scale turbines for residential-scale use are available that are approximately 7 feet (2 m) to {{convert|25|ft|m|0}} in diameter and produce electricity at a rate of 900 watts to 10,000 watts at their tested wind speed. Some units are designed to be very lightweight, e.g. 16 kilograms (35 lb), allowing rapid response to wind gusts typical of urban settings and easy mounting much like a television antenna. It is claimed that they are inaudible even a few feet under the turbine.{{Fact|date=February 2007}} [[Dynamic braking]] regulates the speed by dumping excess energy, so that the turbine continues to produce electricity even in high winds. The dynamic braking resistor may be installed inside the building to provide heat (during high winds when more heat is lost by the building, while more heat is also produced by the braking resistor). The location makes low voltage (around 12 volt) distribution practical. |
|||
Residential wind turbines typically cost between $12,000 and $55,000, but there are incentives and rebates available in 19 states in the U.S. that can cut the purchase price by up to 50 percent.<ref>[http://www.nytimes.com/2007/12/13/garden/13wind.html?em&ex=1197954000&en=57b42d0a2f9ce2be&ei=5087%0A Homespun Electricity, From the Wind - New York Times<!-- Bot generated title -->]</ref> |
|||
The American Wind Energy Association has released several studies on the small wind turbine market in the U.S. and abroad, showing that the U.S. continues to dominate the Small Wind industry.[http://www.awea.org/smallwind/documents/AWEASmallWindMarketStudy2007.pdf] According to another organization, the World Wind Energy Association, it is difficult to assess the total number or capacity of small-scaled wind turbines, but in China alone, there are roughly 300,000 small-scale wind turbines generating electricity.<ref name="wwindea">[http://www.wwindea.org/home/images/stories/pdfs/pr_statistics2006_290107.pdf World Wind Energy Association Statistics]</ref> |
|||
The dominant models on the market, especially in the United States, are [[Wind turbine#Horizontal axis|horizontal-axis wind turbines]] (HAWT). |
|||
There have been a number of recent developments of mini-turbines which could be adapted to home use, including: |
|||
{{prose|date=February 2008}} |
|||
* The AeroTecture [[Wind turbine#Vertical axis|vertical-axis turbine]]<ref>[http://www.aerotecture.com/products.html AeroTecture]</ref> |
|||
* The AeroVironment Architectural Wind Project<ref>{{cite news| title = Energy Technology Center: Project Architectural Wind | publisher = AeroVironment Inc |date=2006 | url=http://www.avinc.com/energy_lab_project_detail.php?id=85 }}</ref><ref>[http://news.com.com/Micro+wind+turbines+are+coming+to+town/2100-11398_3-6037539.html 'Micro' wind turbines are coming to town, CNET, February 10, 2006, Martin LaMonica]</ref> |
|||
* The [[piezoelectric]] windmill project<ref>{{cite news | title = Piezoelectric Windmill: A novel solution to remote sensing | publisher = Japanese Journal of Applied Physics, v. 44 no. 3 p. L104-L107|date=2005 | author = Shashank Priya et al | url =http://mse.uta.edu/Priya/Piezoelectric%20Windmill.pdf}} </ref> |
|||
* The Swift home wind turbine.<ref>[http://www.renewabledevices.com/swift/index.htm Swift Turbines]</ref> The Swift project peaked in 2004 and has had some implementation difficulties while promising to be a low-noise/safe roof-mount/low-cost alternative<ref>[http://www.bettergeneration.co.uk/wind-turbine-models/the-swift-rooftop-wind-energy-system.html Better Generation: Swift Rooftop wind energy system discussion]</ref> |
|||
* The Motorwave micro-wind turbine<ref>[http://www.inhabitat.com/2007/03/21/micro-wind-turbines-small-size-big-impact/ Motorwind]</ref><ref>[http://edition.cnn.com/2007/BUSINESS/04/15/ft.gambarota/index.html Lucien Gambarota: Alternative energy pioneer, CNN, 16 April 2007]</ref><ref>[http://www.motorwavegroup.com/new/motorwind/index.html Motorwind Turbines]</ref> |
|||
===DIY Wind turbines === |
|||
With a growing [[DIY]]-community and an increasing interest in environmentally friendly "[[green energy]]", some [[hobby]]ists have endeavored to build their own wind turbines from kits, sourced components, or from scratch. DIY-wind turbine construction has been made popular by diy [[magazines]] as [[OtherPower]], [[Home Power]] magazine<ref>[http://www.rebelwolf.com/essn/ESSN-Dec2005.pdf OtherPower and Home Power as popular diy microgeneration magazines]</ref>, websites as [[Instructables]], and by TV-series as [[Jericho (TV series)|Jericho]] and [[The Time Machine (2002 film)|The Time Machine]]. DIY-made wind turbines are usually smaller (rooftop) turbines of ~ 1kW or less. <ref>[http://www.bwea.com/you/byo.html British Wind and Energy Agency's DIY wind turbines page]</ref><ref>[http://www.otherpower.com/otherpower_wind_tips.html#reading Overview of wind turbine construction and info for proper building]</ref> <ref>[http://www.villageearth.org/pages/Appropriate_Technology/ATSourcebook/ VillageEarth AT SourceBook: Wind Generation]</ref>These small wind turbines are usually [[tilt-up]] or [[fixed]]/guyed towers <ref>[http://www.homepower.com/view/?file=HP105_pg64_Woofenden Smaller wind turbines usually of tilt-up or fixed design]</ref> However, larger (freestanding) and more powerful windtubines are sometimes built as well. The latter can generate power of up to 10kw <ref>[http://www.rebelwolf.com/essn/ESSN-Apr2006.pdf DIY 10kw freestanding turbine (page 17)]</ref> In addition, people are also showing interest in DIY-construction of [[Special_wind_turbines|wind turbines with special designs]] as the [[Savonius]], [[Panemone]], [[Savonius]] wind turbine(to boost power generation).<ref>[http://static2.instructables.com/id/Build-a-Savonius-Wind-Turbine-or-VAWT-to-make-elec/ Another DIY Savonious wind turbine]</ref> <ref>[http://static2.instructables.com/id/A-Home-Power-Plant---Wind-Power-Generator-Revised/ An improved design of a small savonious wind turbine]</ref> When compared to similar sized commercial wind turbines, these DIY turbines tend to be cheaper. <ref>[http://www.instructables.com/id/Ted-Baer_s-Bicycle-Wheel-Windmill/ DIY windturbine for less than 80 dollar]</ref> <ref>[http://www.solarshop.com.au/wind%20turbines%20page.htm Commercial wind turbine for 650 dollar]</ref>Through the internet, the community is now able to obtain plans to construct DIY-wind turbines.<ref>[http://peswiki.com/index.php/Directory:Home_Generation:Wind_Turbine Wind turbine plans from the PESN-database]</ref><ref>[http://static2.instructables.com/id/DIY-1000-watt-wind-turbine/ DIY 1000 Watt windturbine example with pictures]</ref> <ref>[http://www.instructables.com/id/Ted-Baer_s-Bicycle-Wheel-Windmill/ another DIY windmill-example with pictures]</ref><ref>[http://www.builditsolar.com/Projects/Wind/wind.htm#DIYWind Builditsolar wind turbine plans]</ref> <ref>[http://www.thebackshed.com/windmill/articles/GettingStarted.asp The Backshed Wind turbines plans]</ref> <ref>[http://www.rebelwolf.com/essn/ESSN-Jul2006.pdf DIY Wind turbine upgrading]</ref> and there is a growing trend toward building them for domestic requirements. The DIY-wind turbines are now being used both in developed countries and in [[developing countries]], to help power residences and small businesses. At present, organisations as [[Practical Action]] have designed DIY wind turbines that can be easily build by communities in developing nations and are supplying concrete documents on how to do so. <ref>[http://practicalaction.org/?id=region_united_kingdom_turbine Practical action producing info to construct DIY wind turbines for the developing world]</ref> <ref>[http://www.rebelwolf.com/essn/ESSN-Aug2005.pdf Basics on diy small scale windturbines and domestic power consumption]</ref>To assist people in the developing countries, and hobbyists alike, several projects have been [[Open design#Examples_of_open_design_projects|open-sourced]] (eg. with the Jua Kali wind turbine, Hugh Piggot's wind tubine, ForceField Wind Turbine, ...)<ref>[http://peswiki.com/index.php/Directory:Jua_Kali_Micro_Wind_Turbines Jua Kali Wind Turbines open-sourced]</ref> |
|||
== Records == |
|||
The world's largest turbines are manufactured by the Northern [[Germany|German]] companies [[Enercon]] and [[REpower]]. The [http://www.enercon.de/www/en/nachrichten.nsf/41657424de23a0b8c1256ed10041a39f/6230d2639aa384d9c125736e004679c2?OpenDocument ''Enercon E-126''] delivers up to 6 MW, has an overall height of 198 m (650 ft) and a diameter of 126 meters (413 ft). The ''Repower 5M'' delivers up to 5 MW, has an overall height of 183 m (600 ft) and has a diameter of 126 m (413 ft). |
|||
The turbine closest to the [[North Pole]] is a ''Nordex N-80'' in Havoygelvan near [[Hammerfest]], [[Norway]]. The ones closest to the [[South Pole]] are two ''Enarcan E-30'' in [[Antarctica]], used to power the Australian Research Division's [[Mawson Station]].<ref>[http://www.aad.gov.au/apps/operations/electrical.asp Mawson Station Electrical Energy - Australian Antarctic Division<!-- Bot generated title -->]</ref> |
|||
== See also == |
|||
{{Portal|Sustainable development|Sustainable development.svg}} |
|||
<div style="-moz-column-count:2; column-count:2;"> |
|||
* [[Airborne wind turbine]] |
|||
* [[Atmospheric icing]] |
|||
* [[Cape Wind]] Project |
|||
* [[Darrieus wind turbine]] |
|||
*[[Domestic energy consumption]]; supplies energy requirement numbers for private homes which is needed for anyone thinking of installing his own (small-scale) wind turbine |
|||
* [[Electrical generator]] |
|||
* [[Green energy]] |
|||
* [[Hybrid power source]] |
|||
* [[List of wind turbine manufacturers]] |
|||
* [[Microgeneration]] |
|||
* [[Renewable energy]] |
|||
* [[Savonius wind turbine]] |
|||
* [[Wind power]] |
|||
* [[Wind power in Australia]] |
|||
* [[Wind power in Germany]] |
|||
* [[Wind power in the United Kingdom]] |
|||
* [[Wind turbines (UK domestic)]] |
|||
* [[Windmill]] |
|||
</div> |
|||
==References== |
|||
{{reflist}} |
|||
* BBC News,"Wind farms 'must take root in UK", http://news.bbc.co.uk/2/hi/science/nature/4560139.stm, BBC News, Copyright 2007 |
|||
* Alan Wyatt: ''Electric Power: Challenges and Choices''. Book Press Ltd., Toronto 1986, ISBN 0-920650-00-7 |
|||
* Tony Burton, David Sharpe, Nick Jenkins, Ervin Bossanyi: ''Wind Energy Handbook'', John Wiley & Sons, 1st edition (2001), ISBN 0-471-48997-2 |
|||
*Darrell, Dodge, Early History Through 1875, TeloNet Web Development, http://telosnet.com/wind/early.html, Copyright 1996-2001 |
|||
*David, Macaulay, New Way Things Work, Houghton Mifflin Company, Boston, Copyright 1994-1999, pg.41-42 |
|||
==External links== |
|||
<!-- ==============================({{NoMoreLinks}})============================== --> |
|||
<!-- DO NOT ADD MORE LINKS TO THIS ARTICLE. WIKIPEDIA IS NOT A COLLECTION OF LINKS --> |
|||
<!-- If you think that your link might be useful, instead of placing it here, put --> |
|||
<!-- it on this article's discussion page first. Links that have not been verified --> |
|||
<!-- WILL BE DELETED --> |
|||
<!-- ============================================================================= --> |
|||
{{Commons|Wind turbine}} |
|||
===General wind turbine information=== |
|||
*[http://www.sustainablex.com/en/index.php?title=Portal:Wind Domestic and Commercial wind turbine directory and information wiki, SustainableX.com] |
|||
*[http://www.creswindfarm.gr/site1/last10min_en.htm 3.01 MW Demonstration Wind Farm] Online data (last 10min) |
|||
*[http://www.awea.org/faq/vawt.html Eric, Eggleston, What are vertical-axis wind turbines (VAWTS)?, American Wind Energy Association] |
|||
*[http://eereweb.ee.doe.gov/windandhydro/wind_history.html History of wind energy, U.S Department of Energy] |
|||
*[http://www1.eere.energy.gov/windandhydro/wind_how.html How wind turbines work, U.S Department of Energy] |
|||
*[http://www.awea.org/faq/basiccf.html Wind turbine configurations, American Wind] |
|||
*[http://www.windpower.org/en/tour/econ/economic.htm Wind energy economics, Danish Wind Industry Association] |
|||
*[http://www.wwindea.org/ Wind Energy Technology World Wind Energy Association] |
|||
*[http://green.nationalgeographic.com/environment/global-warming/wind-power-interactive.html Wind turbine simulation, National Geographic] |
|||
*[http://www.thekevdog.com/projects/wind_generator/ Build a wind turbine at home for $150] |
|||
*[http://www.ourecohouse.info/blog/?p=15 Wind turbines and birds] |
|||
*[http://www.shipwrecks.uk.com/news.htm#windturb Wind turbines and shipwrecks] |
|||
===Wind turbine manufacturers=== |
|||
*{{dmoz|Science/Technology/Energy/Renewable/Wind/|Wind technology websites}} |
|||
*{{Dmoz|Science/Technology/Energy/Renewable/Wind/}} |
|||
[[Category:Aerodynamics]] |
|||
[[Category:Electric power]] |
|||
[[Category:Electrical generators]] |
|||
[[Category:Electro mechanical engineering]] |
|||
[[Category:Energy conversion]] |
|||
[[Category:Renewable energy]] |
|||
[[Category:Wind turbines]] |
|||
{{Link FA|de}} |
|||
[[bg:Ветрогенератор]] |
|||
[[ca:Aerogenerador]] |
|||
[[cs:Větrná turbína]] |
|||
[[de:Windkraftanlage]] |
|||
[[el:Αιολική μηχανή]] |
|||
[[es:Aerogenerador]] |
|||
[[eo:Ventoturbino]] |
|||
[[fr:Éolienne]] |
|||
[[gl:Aeroxerador]] |
|||
[[id:Turbin angin]] |
|||
[[he:טורבינת רוח]] |
|||
[[lt:Vėjo jėgainė]] |
|||
[[nl:Windturbine]] |
|||
[[nn:Vindkraftverk]] |
|||
[[no:Vindkraftverk]] |
|||
[[ja:風力原動機]] |
|||
[[pl:Turbina wiatrowa]] |
|||
[[pt:Aerogerador]] |
|||
[[ru:Ветрогенератор]] |
|||
[[fi:Tuuliturbiini]] |
|||
[[sv:Vindkraftverk]] |
|||
[[vi:Tua bin gió]] |
|||
[[tr:Rüzgâr türbini]] |
|||
[[uk:Вітрогенератор]] |
|||
[[wa:Tourniketreye]] |
Revision as of 00:33, 29 March 2008
![](http://upload.wikimedia.org/wikipedia/commons/thumb/7/72/Turbine_aalborg.jpg/220px-Turbine_aalborg.jpg)
A wind turbine is a rotating machine that converts the kinetic energy in wind into mechanical energy. If the mechanical energy is used directly by machinery, such as a pump or grinding stones, the machine is usually called a windmill. If the mechanical energy is then converted to electricity, the machine is called a wind generator, wind turbine, wind power unit (WPU) or wind energy converter (WEC) .
This article discusses electric power generation machinery. Windmill discusses machines used for grain-grinding,water pumping, etc. The article on wind power describes turbine placement, economics, public concerns, and controversy. The wind energy section of that article describes the distribution of wind energy over time, and how that affects wind-turbine design. See environmental concerns with electricity generation for discussion of environmental problems with wind-energy production.
History
![](http://upload.wikimedia.org/wikipedia/commons/thumb/5/50/Wind_turbine_1941.jpg/220px-Wind_turbine_1941.jpg)
Wind machines were used for grinding grain in Persia as early as 200 B.C. This type of machine was introduced into the Roman Empire by 250 A.D. By the 14th century Dutch windmills were in use to drain areas of the Rhine River delta. 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 MW. The first windmill for electricity production was built in Cleveland, Ohio by Charles F Brush in 1888, and in 1908 there were 72 wind-driven electric generators from 5 kW to 25 kW. The largest machines were on 24 m (79 ft) towers with four-bladed 23 m (75 ft) diameter rotors. Around the time of World War I, American windmill makers were producing 100,000 farm windmills each year, most for water-pumping.[1] By the 1930s windmills for electricity were common on farms, mostly in the United States where distribution systems had not yet been installed. In this period, high-tensile steel was cheap, and windmills were placed atop prefabricated open steel lattice towers.
A forerunner of modern horizontal-axis wind generators was in service at Yalta, USSR in 1931. This was a 100 kW generator on a 30 m (100 ft) tower, connected to the local 6.3 kV distribution system. It was reported to have an annual capacity factor of 32 per cent, not much different from current wind machines.
The very first electricity generating windmill operated in the UK was a battery charging machine installed in 1887 by James Blyth in Scotland. The first utility grid-connected wind turbine operated in the UK was built by the John Brown Company in 1954 in the Orkney Islands. It had an 18 metre diameter, three-bladed rotor and a rated output of 100 kW.
Potential turbine power
![](http://upload.wikimedia.org/wikipedia/commons/thumb/b/bb/Wind_power_coeff.jpg/220px-Wind_power_coeff.jpg)
The amount of power transferred to a wind turbine is directly proportional to the density of the air, the area swept out by the rotor, and the cube of the wind speed.
The usable power available in the wind is given by:
- ,
where P = power in watts, α = an efficiency factor determined by the design of the turbine, ρ = mass density of air in kilograms per cubic meter, r = radius of the wind turbine in meters, and v = velocity of the air in meters per second.[2]
As the wind turbine extracts energy from the air flow, the air is slowed down, which causes it to spread out. Albert Betz, a German physicist, determined in 1919 (see Betz' law) that a wind turbine can extract at most 59% of the energy that would otherwise flow through the turbine's cross section, that is α can never be higher than 0.59 in the above equation. The Betz limit applies regardless of the design of the turbine.
This equation shows the effects of the mass rate of flow of air travelling through the turbine, and the energy of each unit mass of air flow due to its velocity. As an example, on a cool 15 °C (59 °F) day at sea level, air density is 1.225 kilograms per cubic metre. An 8 m/s (28.8 km/h or 18 mi/h) breeze blowing through a 100 meter diameter rotor would move almost 77,000 kilograms of air per second through the swept area. The total power of the example breeze through a 100 meter diameter rotor would be about 2.5 megawatts. Betz' law states that no more than 1.5 megawatts could be extracted.
Types of wind turbines
Wind turbines can be separated into two types based by the axis in which the turbine rotates. Turbines that rotate around a horizontal axis are more common. Vertical-axis turbines are less frequently used.
Horizontal axis
Horizontal-axis wind turbines(HAWT) have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive a generator.
Since a tower produces turbulence behind it, the turbine is usually pointed upwind of the tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed a considerable distance in front of the tower and are sometimes tilted up a small amount.
Downwind machines have been built, despite the problem of turbulence, because they don't need an additional mechanism for keeping them in line with the wind, and because in high winds, the blades can be allowed to bend which reduces their swept area and thus their wind resistance. Since turbulence leads to fatigue failures, and reliability is so important, most HAWTs are upwind machines.
HAWT Subtypes
There are several types of HAWT:
![](http://upload.wikimedia.org/wikipedia/commons/thumb/5/56/Doesburgermolen.jpg/220px-Doesburgermolen.jpg)
- Windmills
- These squat structures, typically (at-least) four-bladed, usually with wooden shutters or fabric sails, were developed in Europe. These windmills were pointed into the wind manually or via a tail-fan and were typically used to grind grain. In the Netherlands they were also used to pump water from low-lying land, and were instrumental in keeping its polders dry. Windmills were also located throughout the USA, especially in the Northeastern region.
- Modern Rural Windmills
The Eclipse windmill factory was set up around 1866 in Beloit, Wisconsin and soon became a huge success building mills for farm water pumping and railroad tank filling. Other firms like Star, Dempster, and Aeromotor also entered the market. Hundreds of thousands of these mills were produced before rural electrification and small numbers continue to be made.[1] They typically had many blades, operated at tip speed ratios (defined below) not better than one, and had good starting torque. Some had small direct-current generators used to charge storage batteries, to provide a few lights, or to operate a radio receiver. The American rural electrification connected many farms to centrally-generated power and replaced individual windmills as a primary source of farm power by the 1950's. They were also produced in other countries like South Africa and Australia (where an American design was copied in 1876[3]). Such devices are still used in locations where it is too costly to bring in commercial power.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/09/Hassloch-pfalz_westernmill_20060429_387_part.jpg/220px-Hassloch-pfalz_westernmill_20060429_387_part.jpg)
In Schiedam, the Netherlands, a traditional style windmill (the Noletmolen) was built in 2005 to generate electricity.[4] The mill is one of the tallest Tower mills in the world, being some 42.5 metres (139 ft) tall.
- Common modern wind turbines
Turbines used in wind farms for commercial production of electric power are usually three-bladed and pointed into the wind by computer-controlled motors. This type is produced by Danish and other manufacturers. These have high tip speeds of up to six times the wind speed, high efficiency, and low torque ripple which contributes to good reliability. The blades are usually colored light gray to blend in with the clouds and range in length from 20 to 40 metres (65 to 130 ft) or more. The tubular steel towers range from about 200 to 300 feet (60 to 90 metres) high. The blades rotate at 10-22 revolutions per minute,[5][6] and a gear box steps up the speed of the generator. Some models operate at constant speed, but more energy can be collected by variable-speed turbines which use a solid-state power converter to interface to the transmission system. All turbines are equipped with high wind shut down features to avoid over speed damage.
HAWT advantages
- Blades are to the side of the turbine's center of gravity, helping stability.
- Ability to wing warp, which gives the turbine blades the best angle of attack. Allowing the angle of attack to be remotely adjusted gives greater control, so the turbine collects the maximum amount of wind energy for the time of day and season.
- Ability to pitch the rotor blades in a storm, to minimize damage.
- Tall tower allows access to stronger wind in sites with wind shear. In some wind shear sites, every ten meters up, the wind speed can increase by 20% and the power output by 34%..
HAWT disadvantages
- HAWTs have difficulty operating in near ground, turbulent winds.
- The tall towers and long blades up to 90 meters long are difficult to transport on the sea and on land. Transportation can now cost 20% of equipment costs.
- Tall HAWTs are difficult to install, needing very tall and expensive cranes and skilled operators.
- The FAA has raised concerns about tall HAWTs effects on radar near Air Force bases.
- Their height can create local opposition based on impacts to viewsheds.
- Downwind variants suffer from fatigue and structural failure caused by turbulence.
Cyclic stresses and vibration
Cyclic stresses fatigue the blade, axle and bearing material failures were a major cause of turbine failure for many years. Because wind velocity often increases at higher altitudes, the backward force and torque on a horizontal-axis wind turbine (HAWT) blade peaks as it turns through the highest point in its circle. The tower hinders the airflow at the lowest point in the circle, which produces a local dip in force and torque. These effects produce a cyclic twist on the main bearings of an HAWT. The combined twist is worst in machines with an even number of blades, where one is straight up when another is straight down. To improve reliability, teetering hubs have been used which allow the main shaft to rock through a few degrees, so that the main bearings do not have to resist the torque peaks.
When the turbine turns to face the wind, the rotating blades act like a gyroscope. As it pivots, gyroscopic precession tries to twist the turbine into a forward or backward somersault. For each blade on a wind generator's turbine, precessive force is at a minimum when the blade is horizontal and at a maximum when the blade is vertical. This cyclic twisting can quickly fatigue and crack the blade roots, hub and axle of the turbines.
Vertical axis
Vertical-axis wind turbines (or VAWTs) have the rotor shaft arranged vertically . VAWTs are usally situated closer to the ground since they can utilise turbulent winds , also , the air has a higher density at low altitude and therfore carries more energy at a given wind speed .
VAWT subtypes
![](http://upload.wikimedia.org/wikipedia/commons/thumb/3/3c/Darrieus-windmill.jpg/220px-Darrieus-windmill.jpg)
- Darrieus wind turbine
- "Eggbeater" turbines. They have good efficiency, but produce large torque ripple and cyclic stress on the tower, which contributes to poor reliability. Also, they generally require some external power source, or an additional Savonius rotor, to start turning, because the starting torque is very low. The torque ripple is reduced by using 3 or more blades which results in a higher solidity for the rotor. Solidity is measured by blade area over the rotor area. Newer Darrieus type turbines are not held up by guy wires but have an external superstructure connected to the top bearing.
- Gorlov helical turbine
- Essentially a darrieus turbine in a helical configuration. Patented in 2001. It solves most of the problems of the Darrieus rotor. It is self-starting, has lower torque ripple, low vibration and noise, and low cyclic stress. High reliability is expected from tested or matured designs. At least two wind turbine products are on the market as of 2007, including the Turby wind turbine and the Quietrevolution wind turbine. Most importantly, the GHT is an excellent turbine for zero-head hydropower, and appears to be a much needed ecologically benign and affordable solution for micro-hydropower. It is up to 35% efficient, which is competitive with the most efficient VAWT's.
- Giromill
- A subtype of Darrieus turbine with straight, as opposed to curved, blades. The cycloturbine variety have variable pitch to reduce the torque pulsation and are self-starting [1]. The advantages of variable pitch are: high starting torque; a wide, relatively flat torque curve; a lower blade speed ratio; a higher coefficient of performance; more efficient operation in turbulent winds; and a lower blade speed ratio which lowers blade bending stresses. Straight, V, or curved blades may be used. Recently , this type of turbine has been advanced by former Russian rocket scientists who claim to have increased the efficiency of the VAWT up to 38% . A company , SRC Vertical Ltd.[2] has been formed , and has begun selling the new turbine .
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Windlahor.jpg/220px-Windlahor.jpg)
- Savonius wind turbine
- These are drag-type devices with two- (or more) scoops that are used in anemometers, the Flettner vents (commonly seen on bus and van roofs), and in some high-reliability low-efficiency power turbines. They are always self-starting if there are at least three scoops. They sometimes have long helical scoops to give a smooth torque. The Banesh rotor and especially the Rahai rotor improve efficiency with blades shaped to produce significant lift as well as drag. A new variety uses sails that can open or close with changes in wind speed.
VAWT advantages
- Can be easier to maintain if the moving parts are located near the ground. This is due to the shape of some VAWTs , the airfoils or rotor blades are connected by arms to a shaft that sits on a bearing and drives a generator below, usually by first connecting to a gearbox.
- As the rotor blades are vertical, a yaw device is not needed, reducing the need for this bearing and its cost.
- VAWTs have a higher airfoil pitch angle, giving improved aerodynamics while decreasing drag at low and high pressures.
- Straight bladed VAWT designs with a square or rectangular crossection have a larger swept area for a given diameter than the circular swept area of HAWTs .
- Mesas, hilltops, ridgelines and passes can have faster more powerful winds near the ground because the wind is forced up a slope or funnelled into a pass and into the path of VAWTs situated close to the ground .
- Low height useful where laws do not permit structures to be placed high.
- Does not need a free standing tower so is much less expensive and stronger in high winds that are close to the ground.
- Usually have a lower Tip-Speed ratio so less likely to break in high winds.
- Does not need to turn to face the wind if the wind direction changes making them ideal in turbulent wind conditions .
- They can potentially be built to a far larger size than HAWT's , for instance floating VAWT's hundreds of meters in diameter where the entire vessel rotates , can eliminate the need for a large and expensive bearing .
- Newer carbon composite blades are lightweight and easier to install.
VAWT disadvantages
- Most VAWTs produce energy at only 50% of the efficiency of HAWTs in large part because of the additional drag that they have as their blades rotate into the wind. This can be overcome by using structures to funnel more and align the wind into the rotor (e.g. "stators" on early Windstar turbines) or the "vortex" effect of placing straight bladed VAWTs closely together (e.g. Patent # 6784566).
- There may be a height limitation to how tall a vertical wind turbine can be built and how much sweep area it can have. However , this can be overcome by connecting a multiple number of turbines together in a triangular pattern with bracing across the top of the structure . Thus reducing the need for such strong vertical support , and allowing the turbine blades to be made much longer .
- Most VAWTS need to be installed on a relatively flat piece of land and some sites could be too steep for them but are still usable by HAWTs.
- Most VAWTs have low starting torque, and may require energy to start the turning.
- A VAWT that uses guy wires to hold it in place puts stress on the bottom bearing as all the weight of the rotor is on the bearing. Guy wires attached to the top bearing increase downward thrust in wind gusts. Solving this problem requires a superstructure to hold a top bearing in place to eliminate the downward thrusts of gust events in guy wired models.
- While VAWTs' parts are located on the ground, they are also located under the weight of the structure above it, which can make changing out parts near impossible without dismantling the structure if not designed properly.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/e/e7/Windmills_at_Lackawanna%2C_New_York.jpg/220px-Windmills_at_Lackawanna%2C_New_York.jpg)
Locations
Wind turbines can also be classified by the location in which they are to be used. Onshore, offshore, or even aerial wind turbines have unique design characteristics, which are explained in more detail in the section on turbine design and construction.
Turbine design and construction
Wind turbines are designed to exploit the wind energy that exists at a location. Aerodynamic modeling is used to determine the optimum tower height, control systems, number of blades, and blade shape.
Virtually all modern wind turbines convert wind energy to electricity for energy distribution. As described, the modern wind turbine is a system that comprises three integral components with distinct disciplines of engineering science. The rotor component, which is approximately 20% of the wind turbine cost, includes the blades for converting wind energy to an intermediate low speed rotational energy. The generator component, which is approximately 34% of the wind turbine cost, includes the electrical generator, the control electronics, and most likely a gearbox component for converting the low speed rotational energy to electricity. The structural support component, which is approximately 15% of the wind turbine cost, includes the tower for optimally situating the rotor component to the wind energy source.[7]
Special wind turbines
One E-66 wind turbine at Windpark Holtriem, Germany carries an observation deck, open for visitors to see. Another turbine of the same type, with an observation deck, is located in Swaffham, England.
A series of lighter-than-air wind turbines are in development in Canada by Magenn Power. They deliver power to the ground by a tether system.[8]
Wind turbines may also be used in conjunction with a large vertical solar updraft tower to extract the energy due to air heated by the Sun.
Variable pitch wind turbines are another special (yet low-cost) design. Designs such as the Jacobs are said to be inexpensive, highly efficient and usable in diy-construction. [9]
Small wind turbines
Small wind turbines may be as small as a four hundred watt generators for residential use. The small ones often have direct drive generators, direct current output, aeroelastic blades, lifetime bearings and use a vane to point into the wind. Larger, more costly turbines generally have geared power trains, alternating current output, flaps and are actively pointed into the wind. Direct drive generators and aeroelastic blades for large wind turbines are being researched.
A small wind turbine can be installed on a roof. Installation issues then include the strength of the roof, vibration, and the turbulence caused by the roof ledge. A small-scale, rooftop wind turbine is said to be able to generate power from 10% to up to 25% of the electricity requirements of a regular house. [10]
![](http://upload.wikimedia.org/wikipedia/commons/thumb/2/20/Wind-power-small-scale.jpg/220px-Wind-power-small-scale.jpg)
Small scale turbines for residential-scale use are available that are approximately 7 feet (2 m) to 25 feet (8 m) in diameter and produce electricity at a rate of 900 watts to 10,000 watts at their tested wind speed. Some units are designed to be very lightweight, e.g. 16 kilograms (35 lb), allowing rapid response to wind gusts typical of urban settings and easy mounting much like a television antenna. It is claimed that they are inaudible even a few feet under the turbine.[citation needed] Dynamic braking regulates the speed by dumping excess energy, so that the turbine continues to produce electricity even in high winds. The dynamic braking resistor may be installed inside the building to provide heat (during high winds when more heat is lost by the building, while more heat is also produced by the braking resistor). The location makes low voltage (around 12 volt) distribution practical.
Residential wind turbines typically cost between $12,000 and $55,000, but there are incentives and rebates available in 19 states in the U.S. that can cut the purchase price by up to 50 percent.[11]
The American Wind Energy Association has released several studies on the small wind turbine market in the U.S. and abroad, showing that the U.S. continues to dominate the Small Wind industry.[3] According to another organization, the World Wind Energy Association, it is difficult to assess the total number or capacity of small-scaled wind turbines, but in China alone, there are roughly 300,000 small-scale wind turbines generating electricity.[12]
The dominant models on the market, especially in the United States, are horizontal-axis wind turbines (HAWT).
There have been a number of recent developments of mini-turbines which could be adapted to home use, including:
![]() |
- The AeroTecture vertical-axis turbine[13]
- The AeroVironment Architectural Wind Project[14][15]
- The piezoelectric windmill project[16]
- The Swift home wind turbine.[17] The Swift project peaked in 2004 and has had some implementation difficulties while promising to be a low-noise/safe roof-mount/low-cost alternative[18]
- The Motorwave micro-wind turbine[19][20][21]
DIY Wind turbines
With a growing DIY-community and an increasing interest in environmentally friendly "green energy", some hobbyists have endeavored to build their own wind turbines from kits, sourced components, or from scratch. DIY-wind turbine construction has been made popular by diy magazines as OtherPower, Home Power magazine[22], websites as Instructables, and by TV-series as Jericho and The Time Machine. DIY-made wind turbines are usually smaller (rooftop) turbines of ~ 1kW or less. [23][24] [25]These small wind turbines are usually tilt-up or fixed/guyed towers [26] However, larger (freestanding) and more powerful windtubines are sometimes built as well. The latter can generate power of up to 10kw [27] In addition, people are also showing interest in DIY-construction of wind turbines with special designs as the Savonius, Panemone, Savonius wind turbine(to boost power generation).[28] [29] When compared to similar sized commercial wind turbines, these DIY turbines tend to be cheaper. [30] [31]Through the internet, the community is now able to obtain plans to construct DIY-wind turbines.[32][33] [34][35] [36] [37] and there is a growing trend toward building them for domestic requirements. The DIY-wind turbines are now being used both in developed countries and in developing countries, to help power residences and small businesses. At present, organisations as Practical Action have designed DIY wind turbines that can be easily build by communities in developing nations and are supplying concrete documents on how to do so. [38] [39]To assist people in the developing countries, and hobbyists alike, several projects have been open-sourced (eg. with the Jua Kali wind turbine, Hugh Piggot's wind tubine, ForceField Wind Turbine, ...)[40]
Records
The world's largest turbines are manufactured by the Northern German companies Enercon and REpower. The Enercon E-126 delivers up to 6 MW, has an overall height of 198 m (650 ft) and a diameter of 126 meters (413 ft). The Repower 5M delivers up to 5 MW, has an overall height of 183 m (600 ft) and has a diameter of 126 m (413 ft).
The turbine closest to the North Pole is a Nordex N-80 in Havoygelvan near Hammerfest, Norway. The ones closest to the South Pole are two Enarcan E-30 in Antarctica, used to power the Australian Research Division's Mawson Station.[41]
See also
- Airborne wind turbine
- Atmospheric icing
- Cape Wind Project
- Darrieus wind turbine
- Domestic energy consumption; supplies energy requirement numbers for private homes which is needed for anyone thinking of installing his own (small-scale) wind turbine
- Electrical generator
- Green energy
- Hybrid power source
- List of wind turbine manufacturers
- Microgeneration
- Renewable energy
- Savonius wind turbine
- Wind power
- Wind power in Australia
- Wind power in Germany
- Wind power in the United Kingdom
- Wind turbines (UK domestic)
- Windmill
References
- ^ a b Quirky old-style contraptions make water from wind on the mesas of West Texas
- ^ Iowa Energy Center Wind Energy Manual.
- ^ Extract from Triumph of the Griffiths Family, http://au.geocities.com/ozwindmills/SouthernCross.htm, Bruce Millett, 1984, accessed January 26, 2008
- ^ Molendatabase Dutch text
- ^ 1.5 MW Wind Turbine Technical Specifications
- ^ Size specifications of common industrial wind turbines
- ^ "Wind Turbine Design Cost and Scaling Model," Technical Report NREL/TP-500-40566, December, 2006, page 35,36. http://www.nrel.gov/docs/fy07osti/40566.pdf
- ^ Magenn Power Inc. - Technology
- ^ Jacobs wind turbine (page 18)
- ^ Rooftop wind turbines able to power up to 25% of domestic energy requirements
- ^ Homespun Electricity, From the Wind - New York Times
- ^ World Wind Energy Association Statistics
- ^ AeroTecture
- ^ "Energy Technology Center: Project Architectural Wind". AeroVironment Inc. 2006.
- ^ 'Micro' wind turbines are coming to town, CNET, February 10, 2006, Martin LaMonica
- ^ Shashank Priya; et al. (2005). "Piezoelectric Windmill: A novel solution to remote sensing" (PDF). Japanese Journal of Applied Physics, v. 44 no. 3 p. L104-L107.
{{cite news}}
: Explicit use of et al. in:|author=
(help) - ^ Swift Turbines
- ^ Better Generation: Swift Rooftop wind energy system discussion
- ^ Motorwind
- ^ Lucien Gambarota: Alternative energy pioneer, CNN, 16 April 2007
- ^ Motorwind Turbines
- ^ OtherPower and Home Power as popular diy microgeneration magazines
- ^ British Wind and Energy Agency's DIY wind turbines page
- ^ Overview of wind turbine construction and info for proper building
- ^ VillageEarth AT SourceBook: Wind Generation
- ^ Smaller wind turbines usually of tilt-up or fixed design
- ^ DIY 10kw freestanding turbine (page 17)
- ^ Another DIY Savonious wind turbine
- ^ An improved design of a small savonious wind turbine
- ^ DIY windturbine for less than 80 dollar
- ^ Commercial wind turbine for 650 dollar
- ^ Wind turbine plans from the PESN-database
- ^ DIY 1000 Watt windturbine example with pictures
- ^ another DIY windmill-example with pictures
- ^ Builditsolar wind turbine plans
- ^ The Backshed Wind turbines plans
- ^ DIY Wind turbine upgrading
- ^ Practical action producing info to construct DIY wind turbines for the developing world
- ^ Basics on diy small scale windturbines and domestic power consumption
- ^ Jua Kali Wind Turbines open-sourced
- ^ Mawson Station Electrical Energy - Australian Antarctic Division
- BBC News,"Wind farms 'must take root in UK", http://news.bbc.co.uk/2/hi/science/nature/4560139.stm, BBC News, Copyright 2007
- Alan Wyatt: Electric Power: Challenges and Choices. Book Press Ltd., Toronto 1986, ISBN 0-920650-00-7
- Tony Burton, David Sharpe, Nick Jenkins, Ervin Bossanyi: Wind Energy Handbook, John Wiley & Sons, 1st edition (2001), ISBN 0-471-48997-2
- Darrell, Dodge, Early History Through 1875, TeloNet Web Development, http://telosnet.com/wind/early.html, Copyright 1996-2001
- David, Macaulay, New Way Things Work, Houghton Mifflin Company, Boston, Copyright 1994-1999, pg.41-42
External links
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
General wind turbine information
- Domestic and Commercial wind turbine directory and information wiki, SustainableX.com
- 3.01 MW Demonstration Wind Farm Online data (last 10min)
- Eric, Eggleston, What are vertical-axis wind turbines (VAWTS)?, American Wind Energy Association
- History of wind energy, U.S Department of Energy
- How wind turbines work, U.S Department of Energy
- Wind turbine configurations, American Wind
- Wind energy economics, Danish Wind Industry Association
- Wind Energy Technology World Wind Energy Association
- Wind turbine simulation, National Geographic
- Build a wind turbine at home for $150
- Wind turbines and birds
- Wind turbines and shipwrecks