Wind turbine

Last updated

Thorntonbank Wind Farm, using 5 MW turbines REpower 5M in the North Sea off the coast of Belgium. Windmills D1-D4 (Thornton Bank).jpg
Thorntonbank Wind Farm, using 5 MW turbines REpower 5M in the North Sea off the coast of Belgium.

A wind turbine, or alternatively referred to as a wind energy converter, is a device that converts the wind's kinetic energy into electrical energy.

Wind power the conversion of wind energy into a useful form

Wind power is the use of air flow through wind turbines to provide the mechanical power to turn electric generators and traditionally to do other work, like milling or pumping. Wind power, as an alternative to burning fossil fuels, is plentiful, renewable, widely distributed, clean, produces no greenhouse gas emissions during operation, consumes no water, and uses little land. The net effects on the environment are far less problematic than those of fossil fuel sources.

Kinetic energy energy possessed by an object by virtue of its motion

In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest.

Electrical energy is energy derived from electric potential energy or kinetic energy. When used loosely, "electrical energy" refers to energy that has been converted from electric potential energy. This energy is supplied by the combination of electric current and electric potential that is delivered by an electrical circuit. At the point that this electric potential energy has been converted to another type of energy, it ceases to be electric potential energy. Thus, all electrical energy is potential energy before it is delivered to the end-use. Once converted from potential energy, electrical energy can always be called another type of energy.

Contents

Wind turbines are manufactured in a wide range of vertical and horizontal axis. The smallest turbines are used for applications such as battery charging for auxiliary power for boats or caravans or to power traffic warning signs. Larger turbines can be used for making contributions to a domestic power supply while selling unused power back to the utility supplier via the electrical grid. Arrays of large turbines, known as wind farms, are becoming an increasingly important source of intermittent renewable energy and are used by many countries as part of a strategy to reduce their reliance on fossil fuels. One assessment claimed that, as of 2009, wind had the "lowest relative greenhouse gas emissions, the least water consumption demands and... the most favourable social impacts" compared to photovoltaic, hydro, geothermal, coal and gas. [1]

Electrical grid Interconnected network for delivering electricity from suppliers to consumers

An electrical grid, or electric grid, is an interconnected network for delivering electricity from producers to consumers. It consists of

Wind farm group of wind turbines

A wind farm or wind park is a group of wind turbines in the same location used to produce electricity. A large wind farm may consist of several hundred individual wind turbines and cover an extended area of hundreds of square miles, but the land between the turbines may be used for agricultural or other purposes. A wind farm can also be located offshore.

Renewable energy energy that is collected from renewable resources

Renewable energy is energy that is collected from renewable resources, which are naturally replenished on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal heat. Renewable energy often provides energy in four important areas: electricity generation, air and water heating/cooling, transportation, and rural (off-grid) energy services.

History

James Blyth's electricity-generating wind turbine, photographed in 1891 James Blyth's 1891 windmill.jpg
James Blyth's electricity-generating wind turbine, photographed in 1891
Nashtifan wind turbines in Sistan, Iran. asbd nshtyfn.jpg
Nashtifan wind turbines in Sistan, Iran.

The windwheel of Hero of Alexandria (10 AD – 70 AD) marks one of the first recorded instances of wind powering a machine in history. [2] [3] However, the first known practical wind power plants were built in Sistan, an Eastern province of Persia (now Iran), from the 7th century. These "Panemone" were vertical axle windmills, which had long vertical drive shafts with rectangular blades. [4] Made of six to twelve sails covered in reed matting or cloth material, these windmills were used to grind grain or draw up water, and were used in the gristmilling and sugarcane industries. [5]

Hero of Alexandria ancient Greek mathematician and engineer

Hero of Alexandria was a mathematician and engineer who was active in his native city of Alexandria, Roman Egypt. He is considered the greatest experimenter of antiquity and his work is representative of the Hellenistic scientific tradition.

Sistan historical and geographical region in present-day Iran, Afghanistan and Pakistan

Sīstān, known in ancient times as Sakastan, is a historical and geographical region in present-day eastern Iran and southern Afghanistan. Largely desert, the region is bisected by the Helmand River, the largest river in Afghanistan, which empties into the hamun lakes that form part of the border between the two countries.

Panemone windmill

A panemone windmill is a type of vertical axis wind turbine. It has a rotating axis positioned vertically, while the wind-catching blades move parallel to the wind. By contrast, the shaft of a horizontal axis wind turbine (HAWT) points into the wind while its blades move at right-angles to the wind's thrust. That is, a panemone primarily uses drag whereas the blades of a HAWT use lift.

Wind power first appeared in Europe during the Middle Ages. The first historical records of their use in England date to the 11th or 12th centuries and there are reports of German crusaders taking their windmill-making skills to Syria around 1190. [6] 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.

Middle Ages Period of European history from the 5th to the 15th century

In the history of Europe, the Middle Ages lasted from the 5th to the 15th century. It began with the fall of the Western Roman Empire and merged into the Renaissance and the Age of Discovery. The Middle Ages is the middle period of the three traditional divisions of Western history: classical antiquity, the medieval period, and the modern period. The medieval period is itself subdivided into the Early, High, and Late Middle Ages.

Crusades Military campaigns of Western Christians in the Middle Ages against Muslims and others

The Crusades were a series of religious wars sanctioned by the Latin Church in the medieval period. The most commonly known Crusades are the campaigns in the Eastern Mediterranean aimed at recovering the Holy Land from Muslim rule, but the term "Crusades" is also applied to other church-sanctioned campaigns. These were fought for a variety of reasons including the suppression of paganism and heresy, the resolution of conflict among rival Roman Catholic groups, or for political and territorial advantage. At the time of the early Crusades the word did not exist, only becoming the leading descriptive term around 1760.

Rhine river in Western Europe

The Rhine is one of the major European rivers, which has its sources in Switzerland and flows in an mostly northerly direction through Germany and The Netherlands, emptying into the North Sea. The river begins in the Swiss canton of Graubünden in the southeastern Swiss Alps, forms part of the Swiss-Liechtenstein, Swiss-Austrian, Swiss-German and then the Franco-German border, then flows through the German Rhineland and the Netherlands and eventually empties into the North Sea.

The first electricity-generating wind turbine was a battery charging machine installed in July 1887 by Scottish academic James Blyth to light his holiday home in Marykirk, Scotland. [7] Some months later American inventor Charles F. Brush was able to build the first automatically operated wind turbine after consulting local University professors and colleagues Jacob S. Gibbs and Brinsley Coleberd and successfully getting the blueprints peer-reviewed for electricity production in Cleveland, Ohio. [7] Although Blyth's turbine was considered uneconomical in the United Kingdom, [7] electricity generation by wind turbines was more cost effective in countries with widely scattered populations. [6]

Professor James Blyth MA, LLD, FRSE FRSSA was a Scottish electrical engineer and academic at Anderson's College, now the University of Strathclyde, in Glasgow. He was a pioneer in the field of electricity generation through wind power and his wind turbine, which was used to light his holiday home in Marykirk, was the world's first-known structure by which electricity was generated from wind power. Blyth patented his design and later developed an improved model which served as an emergency power source at Montrose Lunatic Asylum, Infirmary & Dispensary for the next 30 years. Although Blyth received recognition for his contributions to science, electricity generation by wind power was considered uneconomical and no more wind turbines were built in the United Kingdom until 1951, some 64 years after Blyth built his first prototype.

Marykirk village in United Kingdom

Marykirk is a village in the Kincardine and Mearns area of Aberdeenshire, Scotland, next to the border with Angus at the River North Esk.

Charles F. Brush American businessman

Charles Francis Brush was an American engineer, inventor, entrepreneur, and philanthropist.

The first automatically operated wind turbine, built in Cleveland in 1887 by Charles F. Brush. It was 60 feet (18 m) tall, weighed 4 tons (3.6 metric tonnes) and powered a 12 kW generator. Wind turbine 1888 Charles Brush.jpg
The first automatically operated wind turbine, built in Cleveland in 1887 by Charles F. Brush. It was 60 feet (18 m) tall, weighed 4 tons (3.6 metric tonnes) and powered a 12 kW generator.

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 largest machines were on 24-meter (79 ft) towers with four-bladed 23-meter (75 ft) diameter rotors. By 1908, there were 72 wind-driven electric generators operating in the United States from 5 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. [9]

By the 1930s, wind generators 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 the generators 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-meter (98 ft) 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. [10] [11]

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 1,100 hours before suffering a critical failure. 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 Islands. [7] [12]

Despite these diverse developments, developments in fossil fuel systems almost entirely eliminated any wind turbine systems larger than supermicro size. In the early 1970s, however, anti-nuclear protests in Denmark spurred artisan mechanics to develop microturbines of 22 kW. Organizing owners into associations and co-operatives lead 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.

Resources

Wind Power Density (WPD) is a quantitative measure of wind energy available at any location. It is the mean annual power available per square meter of swept area of a turbine, and is calculated for different heights above ground. Calculation of wind power density includes the effect of wind velocity and air density. [13]

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. [14]

ClassAvg Wind Speed (m/s)Turbulence
IA1016%
IB1014%
IC1012%
IIA8.516%
IIB8.514%
IIC8.512%
IIIA7.516%
IIIB7.514%
IIIC7.512%

Efficiency

Conservation of mass requires that the amount of air entering and exiting a turbine must be equal. Accordingly, Betz's law gives the maximal achievable extraction of wind power by a wind turbine as 16/27 (59.3%) of the total kinetic energy of the air flowing through the turbine. [15]

The maximum theoretical power output of a wind machine is thus 16/27 times the kinetic energy of the air passing through 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 impacting the final price of wind power. [16] Further inefficiencies, such as gearbox losses, 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 at the cube of wind speed, further reducing theoretical efficiency. In 2001, commercial utility-connected turbines deliver 75% to 80% of the Betz limit of power extractable from the wind, at rated operating speed. [17] [18] [ needs update ]

Efficiency can decrease slightly over time, one of the main reasons being dust and insect carcasses on the blades which alters the aerodynamic profile and essentially reduces 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. [19] Ice accretion on turbine blades has also 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. [20] Vertical turbine designs have much lower efficiency than standard horizontal designs. [21]

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. [22]

Different materials have been found to have varying effects on the efficiency of wind turbines. In an Ege University experiment, three wind turbines (Each with three blades with diameters 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. [23]

Types

The three primary types: VAWT Savonius, HAWT towered; VAWT Darrieus as they appear in operation HAWT and VAWTs in operation medium.gif
The three primary types: VAWT Savonius, HAWT towered; VAWT Darrieus as they appear in operation

Wind turbines can rotate about either a horizontal or a vertical axis, the former being both older and more common. [24] They can also include blades, or be bladeless. [25] Vertical designs produce less power and are less common. [26]

Horizontal axis

Components of a horizontal axis wind turbine (gearbox, rotor shaft and brake assembly) being lifted into position Scout moor gearbox, rotor shaft and brake assembly.jpg
Components of a horizontal axis wind turbine (gearbox, rotor shaft and brake assembly) being lifted into position
A turbine blade convoy passing through Edenfield, England Turbine Blade Convoy Passing through Edenfield.jpg
A turbine blade convoy passing through Edenfield, England
Offshore Horizontal Axis Wind Turbines (HAWTs) at Scroby Sands Wind Farm, England Wind Turbines (5132099985).jpg
Offshore Horizontal Axis Wind Turbines (HAWTs) at Scroby Sands Wind Farm, England
Onshore Horizontal Axis Wind Turbines in Zhangjiakou, China Xi Dian Zi Liang Feng Che .jpg
Onshore Horizontal Axis Wind Turbines in Zhangjiakou, China

Large three-bladed horizontal-axis wind turbines (HAWT) with the blades upwind of the tower produce the overwhelming majority of wind power in the world today. These turbines 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 yaw system. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator. [27] Some turbines use a different type of generator suited to slower rotational speed input. These don't need a gearbox, and are called direct-drive, meaning they couple the rotor directly to the generator with no gearbox in between. While permanent magnet direct-drive generators can be more costly due to the rare earth materials required, these gearless turbines are sometimes preferred over gearbox generators because they "eliminate the gear-speed increaser, which is susceptible to significant accumulated fatigue torque loading, related reliability issues, and maintenance costs." [28] There is also the pseudo direct drive mechanism, which has some advantages over the permanent magnet direct drive mechanism. [29] [30]

The rotor of a gearless wind turbine being set. This particular turbine was prefabricated in Germany, before being shipped to the U.S. for assembly. One Energy Wind for Industry permanent magnet direct-drive generator.jpg
The rotor of a gearless wind turbine being set. This particular turbine was prefabricated in Germany, before being shipped to the U.S. for assembly.

Most horizontal axis turbines have their rotors upwind of the supporting tower. Downwind machines have been built, because they don't need an additional mechanism for keeping them in line with the wind. In high winds, the blades can also be allowed to bend, which reduces their swept area and thus their wind resistance. Despite these advantages, upwind designs are preferred, because the change in loading from the wind as each blade passes behind the supporting tower can cause damage to the turbine.

Turbines used in wind farms 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 20 to 80 meters (66 to 262 ft). The size and height of turbines increase year by year. Offshore wind turbines are built up to 8 MW today and have a blade length up to 80 meters (260 ft). Designs with 10 to 12 MW are in preparation. [31] Usual multi megawatt turbines have tubular steel towers with a height of 70 m to 120 m and in extremes up to 160 m.

Vertical axis

A vertical axis Twisted Savonius type turbine. Twisted Savonius wind turbine in operation@60rpm.gif
A vertical axis Twisted Savonius type turbine.

Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. One advantage of this arrangement is that the turbine does not need to be pointed into the wind to be effective, which is an advantage on a site where the wind direction is highly variable. It is also an advantage when the turbine is integrated into a building because it is inherently less steerable. Also, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, improving accessibility for maintenance. However, these designs produce much less energy averaged over time, which is a major drawback. [26] [32]

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. [33]

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, [34] [35] noise may be a concern and an existing structure may not adequately resist the additional stress.

Subtypes of the vertical axis design include:

Darrieus wind turbine

"Eggbeater" turbines, or Darrieus turbines, were named after the French inventor, Georges Darrieus. [36] They have good efficiency, but produce large torque ripple and cyclical stress on the tower, which contributes to poor reliability. They also 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 three or more blades, which results in greater solidity of the rotor. Solidity is measured by blade area divided by the rotor area. Newer Darrieus type turbines are not held up by guy-wires but have an external superstructure connected to the top bearing. [37]

Giromill

A subtype of Darrieus turbine with straight, as opposed to curved, blades. The cycloturbine variety has variable pitch to reduce the torque pulsation and is self-starting. [38] The advantages of variable pitch are: high starting torque; a wide, relatively flat torque curve; 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. [39]

Savonius wind turbine

These are drag-type devices with two (or more) scoops that are used in anemometers, 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.

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. [40]

Parallel

The parallel turbine is similar to the crossflow fan or centrifugal fan. It uses the ground effect. Vertical axis turbines of this type have been tried for many years: a unit producing 10 kW was built by Israeli wind pioneer Bruce Brill in the 1980s. [41] [ unreliable source? ]

Unconventional types

Counter-rotating wind turbine Counter rotating wind turbine animation.gif
Counter-rotating wind turbine
Highway wind turbine Highway wind turbine.gif
Highway wind turbine

Design and construction

Components of a horizontal-axis wind turbine EERE illust large turbine.gif
Components of a horizontal-axis wind turbine
Inside view of a wind turbine tower, showing the tendon cables. WKA spannglieder.jpg
Inside view of a wind turbine tower, showing the tendon cables.

Wind turbine design is a careful balance of cost, energy output, and fatigue life. These factors are balanced using a range of computer modelling techniques. [42]

Components

Wind turbines convert wind energy to electrical energy for distribution. Conventional horizontal axis turbines can be divided into three components:

Nacelle of a wind turbine Badaia - Parque Eolico -BT- 01.jpg
Nacelle of a wind turbine

A 1.5 (MW) wind turbine of a type frequently seen in the United States has a tower 80 meters (260 ft) high. The rotor assembly (blades and hub) weighs 22,000 kilograms (48,000 lb). The nacelle, which contains the generator, weighs 52,000 kilograms (115,000 lb). The concrete base for the tower is constructed using 26,000 kilograms (58,000 lb) reinforcing steel and contains 190 cubic meters (250 cu yd) of concrete. The base is 15 meters (50 ft) in diameter and 2.4 meters (8 ft) thick near the center. [48]

Turbine monitoring and diagnostics

Due to data transmission problems, structural health monitoring of wind turbines is usually performed using several accelerometers and strain gages attached to the nacelle to monitor the gearbox and equipments. Currently, digital image correlation and stereophotogrammetry are used to measure dynamics of wind turbine blades. These methods usually measure displacement and strain to identify location of defects. Dynamic characteristics of non-rotating wind turbines have been measured using digital image correlation and photogrammetry. [49] Three dimensional point tracking has also been used to measure rotating dynamics of wind turbines. [50]

Materials and recent developments

Materials that are typically used for the rotor blades in wind turbines are composites, as they tend to have a high stiffness, high strength, high fatigue resistance, and low weight. [51] Typical resins used for these composites include polyester and epoxy, while glass and carbon fibers have been used for the reinforcing material. [52] Construction may use manual layup techniques or composite resin injection molding. As the price of glass fibers is only about one tenth the price of carbon fiber, glass fiber is still dominant.

New designs

As competition in the wind market increases, companies are seeking ways to draw greater efficiency from their designs. One of the predominant ways wind turbines have gained performance is by increasing rotor diameters, and thus blade length. Retrofitting current turbines with larger blades mitigates the need and risks associated with a system-level redesign. As the size of the blade increases, its tendency to deflect also increases. Thus, from a materials perspective, the stiffness-to-weight is of major importance. As the blades need to function over a 100 million load cycles over a period of 20–25 years, the fatigue life of the blade materials is also of utmost importance. By incorporating carbon fiber into parts of existing blade systems, manufacturers may increase the length of the blades without increasing their overall weight. For instance, the spar cap, a structural element of a turbine blade, commonly experiences high tensile loading, making it an ideal candidate to utilize the enhanced tensile properties of carbon fiber in comparison to glass fiber. [52] Higher stiffness and lower density translates to thinner, lighter blades offering equivalent performance. In a 10 (MW) turbine—which will become more common in offshore systems by 2021—blades may reach over 100 m in length and weigh up to 50 metric tons when fabricated out of glass fiber. A switch to carbon fiber in the structural spar of the blade yields weight savings of 20 to 30 percent, or approximately 15 metric tons. [53]

Materials for blades

Some of the most common materials which are being used for turbine blades now and will be in the future are summarized below:

Glass and carbon fibers

The stiffness of composites is determined by the stiffness of fibers and their volume content. Typically, E-glass fibers are used as main reinforcement in the composites. Typically, the glass/epoxy composites for wind blades contain up to 75% glass by weight. This increases the stiffness, tensile and compression strength. A promising source of the composite materials in the future is glass fibers with modified compositions like S-glass, R-glass etc. Some other special glasses developed by Owens Corning are ECRGLAS, Advantex and most recently WindStrand glass fibers. [54]

Hybrid reinforcements

These include E-glass/carbon, E-glass/aramid and they present an exciting alternative to pure glass or carbon reinforcements. that the full replacement would lead to 80% weight savings, and cost increase by 150%, while a partial (30%) replacement would lead to only 90% cost increase and 50% weight reduction for 8 m turbine. The world currently longest wind turbine rotor blade, the 88.4 m long blade from LM Wind Power is made of carbon/glass hybrid composites. However, additional investigations are required for the optimal composition of the materials [55]

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 interlaminar layers can allow to increase the fatigue resistance, shear or compressive strength as well as fracture toughness of the composites by 30–80%. Research has also shown that the incorporation of small amount of carbon nanotubes/CNT can increase the lifetime up to 1500%.

Costs

While the material cost is significantly lower for all-glass fiber blades than for hybrid glass/carbon fiber blades, there is a potential for tremendous savings in manufacturing costs when labor price is considered. Utilizing carbon fiber enables for simpler designs that use less raw material. The chief manufacturing process in blade fabrication is the layering of plies. By reducing the number of layers of plies, as is enabled by thinner blade design, the cost of labor may be decreased, and in some cases, equate to the cost of labor for glass fiber blades. [56]

Other materials

Materials for wind turbine parts other than the rotor blades (including the rotor hub, gearbox, frame, and tower) are largely composed of steel. Modern turbines use a couple of tons of copper for generators, cables, and such. [57] Smaller wind turbines have begun incorporating more aluminum based alloys into these components in an effort to make the turbines lighter and more efficient, and may continue to be used increasingly if fatigue and strength properties can be improved. Prestressed 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, increasing the demand for magnetic materials in wind turbines. [51] In particular, this would require an increased supply of the rare earth metal neodymium.

Recycling

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 a thermosetting matrix and glass fibers or a combination of glass and carbon fibers. Thermosetting matrix cannot be remolded to form new composites. So the options are either to reuse the blade and the composite material elements as they are found in the blade or to transform the composite material into a new source of material. In Germany, wind turbine blades are commercially recycled as part of an alternative fuel mix for a cement factory.

Supply

A 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 kW generated. The current material consumption and stock was compared to input materials for various onshore system sizes. In all EU countries the estimates for 2020 exceeded and doubled the values consumed in 2009. These countries would need to expand their resources to be able to meet the estimated demand for 2020. For example, currently the EU has 3% of world supply of fluorspar and it requires 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. In addition, the levels of recycling of these materials is very low and focusing on that could alleviate issues with supply in the future. It is important to note that since most of these valuable materials are also used in other emerging technologies, like LEDs, PVs and LCDs, it is projected that demand for them will continue to increase. [58]

A report by the United States Geological Survey estimated the projected materials requirement in order to fulfill the US commitment to supplying 20% of its electricity from wind power by 2030. They did not address requirements for small turbines or offshore turbines since those were not widely deployed in 2008, when the study was created. They found that there are increases in common materials such as cast iron, steel and concrete that represent 2–3% of the material consumption in 2008. Between 110,000 and 115,000 metric tons of fiber glass would be required annually, equivalent to 14% of consumption in 2008. They did not see a high increase in demand for rare metals compared to available supply, however rare metals that are also being used for other technologies such as batteries which are increasing its global demand need to be taken into account. Land, which might not be considered a material, is an important resource in deploying wind technologies. Reaching the 2030 goal would require 50,000 square kilometers of onshore land area and 11,000 square kilometers of offshore. This is not considered a problem in the US due to its vast area and the ability to use land for farming and grazing. A greater limitation for the technology would be the variability and transmission infrastructure to areas of higher demand. [59]

Permanent magnets for wind turbine generators contain rare earth metals such as Nd, Pr, Tb, and Dy. Systems that use magnetic direct drive turbines require higher amounts of rare metals. Therefore, an increase in wind production would increase the demand for these resources. It is estimated that the additional demand for Nd in 2035 may be 4,000 to 18,000 tons and Dy could see an increase of 200 to 1200 tons. These values represent a quarter to half of current production levels. However, since technologies are developing rapidly, driven by supply and price of materials these estimated levels are extremely uncertain. [60]

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 had been reducing its export quotas of these materials. [61] In recent years, however, other producers have increased production of rare earth minerals and China has removed its reduced export quota on rare earths leading to an increased supply and decreased cost of rare earth minerals, increasing the viability of the implementation of variable speed generators in wind turbines on a large scale. [62]

Due to increased technology and wide implementation, the global glass fiber market might reach US$17.4 billion by 2024, compared to US$8.5 billion in 2014. Since it is the most widely used material for reinforcement in composites around the globe, the expansion of end use applications such as construction, transportation and wind turbines has fueled its popularity. Asia Pacific held the major share of the global market in 2014 with more than 45% volume share. However China is currently the largest producer. The industry receives subsidies from the Chinese government allowing them to export it cheaper to the US and Europe. However, due to the higher demand in the near future some price wars have started to developed to implement anti dumping strategies such as tariffs on Chinese glass fiber. [63]

Wind turbines on public display

The Nordex N50 wind turbine and visitor centre of Lamma Winds in Hong Kong, China Lamma wind turbine.jpg
The Nordex N50 wind turbine and visitor centre of Lamma Winds in Hong Kong, China

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. [64] 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

A small Quietrevolution QR5 Gorlov type vertical axis wind turbine in Bristol, England. Measuring 3 m in diameter and 5 m high, it has a nameplate rating of 6.5 kW to the grid. Quietrevolution Bristol 3513051949.jpg
A small Quietrevolution QR5 Gorlov type vertical axis wind turbine in Bristol, England. Measuring 3 m in diameter and 5 m high, it has a nameplate rating of 6.5 kW to the grid.

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 caravan use. Hybrid solar and wind powered units are increasingly being used for traffic signage, particularly in rural locations, as they avoid the need to lay long cables from the nearest mains connection point. [65] 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. [66] Small units 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, and flaps, and are actively pointed into the wind. Direct drive generators and aeroelastic blades for large wind turbines are being researched.

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 [67] conducted by Charles Meneveau of the Johns Hopkins University, [68] and Johan Meyers of Leuven University in Belgium, based on computer simulations [69] that take into account the detailed interactions among wind turbines (wakes) as well as with the entire turbulent atmospheric boundary layer.

Recent 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. [70]

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. [71] [72]

Modern turbines usually have a small onboard crane for hoisting maintenance tools and minor components. However, large heavy components like generator, gearbox, blades and so on are rarely replaced and a heavy lift external crane is needed in those cases. If the turbine has a difficult access road, a containerized crane can be lifted up by the internal crane to provide heavier lifting. [73]

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

Older turbines were in some early cases not required to be removed when reaching the end of their life. Some still stand, waiting to be recycled or repowered. [74] [75]

A demolition industry develops to recycle offshore turbines at a cost of DKK 2–4 million per (MW), to be guaranteed by the owner. [76]

Comparison with fossil-fuel turbines

Advantages

Wind turbines are generally inexpensive. They will produce electricity at between two and six cents per kilowatt hour, which is one of the lowest-priced renewable energy sources. [77] As technology needed for wind turbines continues to improve, the prices will decrease as well. In addition, there is no competitive market for wind energy, as it does not cost money to get a hold of wind. [77] The main cost of wind turbines are the installation process. The average cost is between $48,000 and $65,000 to install. However, the energy harvested from the turbine will offset the installation cost, as well as provide virtually free energy for years after. [78]

Wind turbines provide a clean energy source, emitting no greenhouse gases and no waste product. Over 1,500 tons of carbon dioxide per year can be eliminated by using a one megawatt turbine instead of one megawatt of energy from a fossil fuel. [79] Being environmentally friendly and green is a large advantage of wind turbines.

Disadvantages

Wind turbines can be very large, reaching over 140 metres (460 ft) tall and with blades 55 metres (60 yd) long, [80] and people have often complained about their visual impact.

Environmental impact of wind power includes effect on wildlife, but can be mitigated if proper monitoring and mitigation strategies are implemented. [81] Thousands of birds, including rare species, have been killed by the blades of wind turbines, [82] though wind turbines contribute relatively insignificantly to anthropogenic avian mortality. For every bird killed by a wind turbine in the US, nearly 500,000 are killed by each of feral cats and buildings. [83] In comparison, conventional coal fired generators contribute significantly more to bird mortality, by incineration when caught in updrafts of smoke stacks and by poisoning with emissions byproducts (including particulates and heavy metals downwind of flue gases). Further, marine life is affected by water intakes of steam turbine cooling towers (heat exchangers) for nuclear and fossil fuel generators, by coal dust deposits in marine ecosystems (e.g. damaging Australia's Great Barrier Reef) and by water acidification from combustion monoxides.

Energy harnessed by wind turbines is intermittent, 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 ridges or bluffs to maximize the access of wind they have, but this also limits the locations where they can be placed. [77] 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. Notably, the relative available output from wind and solar sources is often inversely proportional (balancing)[ citation needed ]. Technology is also being developed to store excess energy, which can then make up for any deficits in supplies.

Records

Fuhrlander Wind Turbine Laasow, in Brandenburg, Germany, among the world's tallest wind turbines Windkraftanlage Laasow.jpg
Fuhrländer Wind Turbine Laasow, in Brandenburg, Germany, among the world's tallest wind turbines
Eole, the largest vertical axis wind turbine, in Cap-Chat, Quebec, Canada Quebecturbine.JPG
Éole, the largest vertical axis wind turbine, in Cap-Chat, Quebec, Canada
Largest capacity conventional drive
See also List of most powerful wind turbines
The Vestas V164 has a rated capacity of 8 MW, [84] later upgraded to 9.5 MW. [85] [86] The wind turbine has an overall height of 220 m (722 ft), a diameter of 164 m (538 ft), is for offshore use, and is the world's largest-capacity wind turbine since its introduction in 2014. The conventional drive train consist of a main gearbox and a medium speed PM generator. Prototype installed in 2014 at the National Test Center Denmark nearby Østerild. Series production began end of 2015.
Largest capacity direct drive
The Enercon E-126 with 7.58 MW and 127 m rotor diameter is the largest direct drive turbine. However, the turbine is the world's most powerful onshore-only wind turbine. The turbine has parted rotor blades with 2 sections for transport. The E-126 was later overtaken by the Siemens SWT-8.0-167-DD (DD being the acronym for "direct drive"), which is the most powerful offshore-only wind turbine. [87]
Largest vertical-axis
Le Nordais wind farm in Cap-Chat, Quebec, has a vertical axis wind turbine (VAWT) named Éole, which is the world's largest at 110 m. [88] It has a nameplate capacity of 3.8 MW. [89]
Largest 1-bladed turbine
The largest single-bladed wind turbine design to be put into complete operation is the MBB Messerschmitt Monopteros M50, with a total power output of no less than 640kW at full capacity. As far as the number of units is concerned, only three ever have been installed at an actual wind park, of which all went to the Jade Wind Park. [90]
Largest 2-bladed turbine
The biggest 2-bladed turbine is built by Mingyang Wind Power in 2013. It is a SCD6.5MW offshore downwind turbine, designed by aerodyn Energiesysteme. [91] [92] [93]
Largest swept area
The turbine with the largest swept area is the Samsung S7.0–171, with a diameter of 171 m, giving a total sweep of 22966 m2.
Tallest
A Nordex 3.3 MW was installed in July 2016. It has a total height of 230m, and a hub height of 164m on 100m concrete tower bottom with steel tubes on top (hybrid tower). [94]
Vestas V164 was the tallest wind turbine, standing in Østerild, Denmark, 220 meters tall, constructed in 2014. It has a steel tube tower.
Highest tower
Fuhrländer installed a 2.5 MW turbine on a 160m lattice tower in 2003 (see Fuhrländer Wind Turbine Laasow and Nowy Tomyśl Wind Turbines).
Most rotors
Lagerwey has build Four-in-One, a multi rotor wind turbine with one tower and four rotors near Maasvlakte.[ citation needed ] In April 2016, Vestas installed a 900 kW four rotor test wind turbine at Risø, made from 4 recycled 225 kW V29 turbines. [95] [96] [97]
Most productive
Four turbines at Rønland Offshore Wind Farm in Denmark share the record for the most productive wind turbines, with each having generated 63.2 GWh by June 2010. [98]
Highest-situated
Since 2013 the world's highest-situated wind turbine was made and installed by WindAid and is located at the base of the Pastoruri Glacier in Peru at 4,877 meters (16,001 ft) above sea level. [99] The site uses the WindAid 2.5 kW wind generator to supply power to a small rural community of micro entrepreneurs who cater to the tourists who come to the Pastoruri glacier. [100]
Largest floating wind turbine
The world's largest floating wind turbine is any of the five 6 MW turbines in the 30 MW Hywind Scotland offshore wind farm. [101]

See also

Related Research Articles

Darrieus wind turbine windmill

The Darrieus wind turbine is a type of vertical axis wind turbine (VAWT) used to generate electricity from the energy carried in the wind. The turbine consists of a number of curved aerofoil blades mounted on a vertical rotating shaft or framework. The curvature of the blades allows the blade to be stressed only in tension at high rotating speeds. There are several closely related wind turbines that use straight blades. This design of wind turbine was patented by Georges Jean Marie Darrieus, a French aeronautical engineer; filing for the patent was October 1, 1926. There are major difficulties in protecting the Darrieus turbine from extreme wind conditions and in making it self-starting.

Enercon German company

Enercon GmbH, based in Aurich, Lower Saxony, Germany, is the fourth-largest wind turbine manufacturer in the world and has been the market leader in Germany since the mid-nineties. Enercon has production facilities in Germany, Sweden, Brazil, India, Canada, Turkey and Portugal. In June 2010, Enercon announced that they would be setting up Irish headquarters in Tralee.

Yaw drive

The yaw drive is an important component of the horizontal axis wind turbines' yaw system. To ensure the wind turbine is producing the maximal amount of electric energy at all times, the yaw drive is used to keep the rotor facing into the wind as the wind direction changes. This only applies for wind turbines with a horizontal axis rotor. The wind turbine is said to have a yaw error if the rotor is not aligned to the wind. A yaw error implies that a lower share of the energy in the wind will be running through the rotor area..

Tail rotor small tail-mounted helicopter rotor

The tail rotor is a smaller rotor mounted so that it rotates vertically or near-vertically at the end of the tail of a traditional single-rotor helicopter. The tail rotor's position and distance from the center of gravity allow it to develop thrust in the same direction as the main rotor's rotation, to counter the torque effect created by the main rotor. Tail rotors are simpler than main rotors since they require only collective changes in pitch to vary thrust. The pitch of the tail rotor blades is adjustable by the pilot via the anti-torque pedals, which also provide directional control by allowing the pilot to rotate the helicopter around its vertical axis.

Airborne wind turbine

An airborne wind turbine is a design concept for a wind turbine with a rotor supported in the air without a tower, thus benefiting from more mechanical and aerodynamic options, the higher velocity and persistence of wind at high altitudes, while avoiding the expense of tower construction, or the need for slip rings or yaw mechanism. An electrical generator may be on the ground or airborne. Challenges include safely suspending and maintaining turbines hundreds of meters off the ground in high winds and storms, transferring the harvested and/or generated power back to earth, and interference with aviation.

Small wind turbine wind turbine used for microgeneration

A small wind turbine is a wind turbine used for microgeneration, as opposed to large commercial wind turbines, such as those found in wind farms, with greater individual power output. The Canadian Wind Energy Association (CanWEA) defines "small wind" as ranging from less than 1000 Watt (1 kW) turbines up to 300 kW turbines. The smaller turbines may be as small as a 50 Watt auxiliary power generator for a boat, caravan, or miniature refrigeration unit. The IEC-61400-2:2006 Standard defines small wind turbines as wind turbines with a rotor swept area smaller than 200 m2, generating at a voltage below 1000 Va.c. or 1500 Vd.c.

Doubly-fed electric machines also slip-ring generators are electric motors or electric generators, where both the field magnet windings and armature windings are separately connected to equipment outside the machine.

Wind turbine design

Wind turbine design is the process of defining the form and specifications of a wind turbine to extract energy from the wind. A wind turbine installation consists of the necessary systems needed to capture the wind's energy, point the turbine into the wind, convert mechanical rotation into electrical power, and other systems to start, stop, and control the turbine.

Unconventional wind turbines wind turbine (proposed or realized) that differs significantly from the most common types in use

Unconventional wind turbines are those that differ significantly from the most common types in use.

History of wind power aspect of history

Wind power has been used as long as humans have put sails into the wind. For more than two millennia wind-powered machines have ground grain and pumped water. Wind power was widely available and not confined to the banks of fast-flowing streams, or later, requiring sources of fuel. Wind-powered pumps drained the polders of the Netherlands, and in arid regions such as the American mid-west or the Australian outback, wind pumps provided water for livestock and steam engines.

Windstar turbine

The Windstar vertical-axis turbine is a lift-type device with straight blades attached at each end to a central rotating shaft. Windstar turbines were invented by Robert Nason Thomas and developed by Wind Harvest International, Inc., formerly the Wind Harvest Company, based in Point Reyes, California. Windstar turbines are operated as Linear Array Vortex Turbine Systems (LAVTS). Each rotor unit has a dual braking system of pneumatic disc brakes and blade pitch. All Windstar models use off-the-shelf generators, gearboxes, bearings and other components.

Vertical axis wind turbine type of wind turbine

A vertical-axis wind turbines (VAWT) is a type of wind turbine where the main rotor shaft is set transverse to the wind while the main components are located at the base of the turbine. This arrangement allows the generator and gearbox to be located close to the ground, facilitating service and repair. VAWTs do not need to be pointed into the wind, which removes the need for wind-sensing and orientation mechanisms. Major drawbacks for the early designs included the significant torque variation or "ripple" during each revolution, and the large bending moments on the blades. Later designs addressed the torque ripple issue by sweeping the blades helically.

Vestas V90-3MW three bladed upwind wind turbine generator that uses pitch control and a doubly fed induction generator

The Vestas V90-3MW is a three bladed upwind wind turbine generator that uses pitch control and a doubly fed induction generator. Its manufacturer claims to have installed over 500 units of this type globally since launch.

Flywheel energy storage

Flywheel energy storage (FES) works by accelerating a rotor (flywheel) to a very high speed and maintaining the energy in the system as rotational energy. When energy is extracted from the system, the flywheel's rotational speed is reduced as a consequence of the principle of conservation of energy; adding energy to the system correspondingly results in an increase in the speed of the flywheel.

GE Power's offshore wind business is a joint venture with Alstom, created in 2015 when most of that company's other electrical power and generation assets were acquired. GE's stake in the joint venture is 50 % plus 1 share.

GE Wind Energy is a branch of GE Renewable Energy a subsidiary of General Electric. The company manufactures and sells wind turbines to the international market. In 2016, GE was the second largest wind turbine manufacturer in the world.

NASA wind turbines

Starting in 1975, NASA managed a program for the United States Department of Energy and the United States Department of Interior to develop utility-scale wind turbines for electric power, in response to the increase in oil prices. A number of the world's largest wind turbines were developed and tested under this pioneering program. The program was an attempt to leap well beyond the then-current state of the art of wind turbine generators, and developed a number of technologies later adopted by the wind turbine industry. The development of the commercial industry however was delayed by a significant decrease in competing energy prices during the 1980s.

The following outline is provided as an overview of and topical guide to wind energy:

Renewable energy sources such as solar, wind, tidal, hydro, biomass, and geothermal have become significant sectors of the energy market. The rapid growth of these sources in the 21st century has been prompted by increasing costs of fossil fuels as well as their environmental impact issues that significantly lowered their use.

Original models of wind turbines were fixed speed turbines; that is, the rotor speed was a constant for all wind speeds. The tip-speed ratio for a wind turbine is given by the following formula:

References

  1. Evans, Annette; Strezov, Vladimir; Evans, Tim (June 2009). "Assessment of sustainability indicators for renewable energy technologies". Renewable and Sustainable Energy Reviews. 13 (5): 1082–1088. doi:10.1016/j.rser.2008.03.008.
  2. Drachmann, A.G. (1961). "Heron's Windmill". Centaurus. 7: 145–151.
  3. Dietrich Lohrmann, "Von der östlichen zur westlichen Windmühle", Archiv für Kulturgeschichte, Vol. 77, Issue 1 (1995), pp. 1–30 (10f.)
  4. Ahmad Y Hassan, Donald Routledge Hill (1986). Islamic Technology: An illustrated history, p. 54. Cambridge University Press. ISBN   0-521-42239-6.
  5. Donald Routledge Hill, "Mechanical Engineering in the Medieval Near East", Scientific American, May 1991, pp. 64–69. (cf. Donald Routledge Hill, Mechanical Engineering)
  6. 1 2 Morthorst, Poul Erik; Redlinger, Robert Y.; Andersen, Per (2002). Wind energy in the 21st century: economics, policy, technology and the changing electricity industry. Houndmills, Basingstoke, Hampshire: Palgrave/UNEP. ISBN   978-0-333-79248-3.
  7. 1 2 3 4 Price, Trevor J. (2004). "Blyth, James (1839–1906)". Oxford Dictionary of National Biography (online ed.). Oxford University Press. doi:10.1093/ref:odnb/100957.(Subscription or UK public library membership required.)
  8. A Wind Energy Pioneer: Charles F. Brush. Danish Wind Industry Association. Archived from the original on 8 September 2008. Retrieved 28 December 2008.
  9. "Quirky old-style contraptions make water from wind on the mesas of West Texas". Archived from the original on 3 February 2008.
  10. Alan Wyatt: Electric Power: Challenges and Choices. Book Press Ltd., Toronto 1986, ISBN   0-920650-00-7
  11. "Bauer, Lucas. "Krasnovsky WIME D-30 – 100,00 kW – Wind turbine"". en.wind-turbine-models.com.
  12. Anon. "Costa Head Experimental Wind Turbine". Orkney Sustainable Energy Website. Orkney Sustainable Energy Ltd. Retrieved 19 December 2010.
  13. "NREL: Dynamic Maps, GIS Data, and Analysis Tools – Wind Maps". Nrel.gov. 3 September 2013. Retrieved 6 November 2013.
  14. Appendix II IEC Classification of Wind Turbines. Wind Resource Assessment and Micro-siting, Science and Engineering. 2015. pp. 269–270. doi:10.1002/9781118900116.app2. ISBN   9781118900116.
  15. "The Physics of Wind Turbines Kira Grogg Carleton College, 2005, p. 8" (PDF). Retrieved 6 November 2013.
  16. "Wind Energy Basics". Bureau of Land Management . Retrieved 23 April 2016.
  17. "Enercon E-family, 330 Kw to 7.5 MW, Wind Turbine Specification" (PDF). Archived from the original (PDF) on 16 May 2011.
  18. Tony Burton et al., (ed), Wind Energy Handbook, John Wiley and Sons 2001 ISBN   0471489972 page 65
  19. Sanne Wittrup. "11 years of wind data shows surprising production decrease" (in Danish) Ingeniøren , 1 November 2013. Retrieved 2 November 2013.
  20. Barber, S.; Wang, Y.; Jafari, S.; Chokani, N.; Abhari, R. S. (2011-01-28). "The Impact of Ice Formation on Wind Turbine Performance and Aerodynamics". Journal of Solar Energy Engineering. 133 (1): 011007–011007–9. doi:10.1115/1.4003187. ISSN   0199-6231.
  21. E. Hau., Wind Turbines: Fundamentals, Technologies, Application, Economics. Springer. Germany. 2006
  22. "ScienceDirect". www.sciencedirect.com. Retrieved 2019-04-04.
  23. Ozdamar, G. (2018). "Numerical Comparison of the Effect of Blade Material on Wind Turbine Efficiency". Acta Physica Polonica A. 134: 156–158. doi:10.12693/APhysPolA.134.156.
  24. "Wind Energy Basics". American Wind Energy Association. Archived from the original on 23 September 2010. Retrieved 24 September 2009.
  25. Elizabeth Stinson (15 May 2015). "The Future of Wind Turbines? No Blades". Wired.
  26. 1 2 Paul Gipe (May 7, 2014). "News & Articles on Household-Size (Small) Wind Turbines". Wind-works.org.
  27. "Wind Turbine Components". Danish Wind Industry Association. 10 May 2003. Archived from the original on 7 June 2008.
  28. G. Bywaters; P. Mattila; D. Costin; J. Stowell; V. John; S. Hoskins; J. Lynch; T. Cole; A. Cate; C. Badger; B. Freeman (October 2007). "Northern Power NW 1500 Direct-Drive Generator" (PDF). National Renewable Energy Laboratory. p. iii.
  29. Magnetic Pseudo direct drive generator
  30. Innwind: Overview of the project and research
  31. "MHI Vestas Launches World's First* 10 Megawatt Wind Turbine". 26 September 2018.
  32. Michael Barnard (7 April 2014). "Vertical Axis Wind Turbines: Great In 1890, Also-rans In 2014". CleanTechnica.
  33. Michael C Brower; Nicholas M Robinson; Erik Hale (May 2010). "Wind Flow Modeling Uncertainty" (PDF). AWS Truepower. Archived from the original on 2013-05-02.CS1 maint: Unfit url (link)
  34. Hugh Piggott (6 January 2007). "Windspeed in the city – reality versus the DTI database". Scoraigwind.com. Retrieved 6 November 2013.
  35. "Urban Wind Turbines" (PDF).
  36. "Vertical-Axis Wind Turbines". Symscape. 7 July 2008. Retrieved 6 November 2013.
  37. Exploit Nature-Renewable Energy Technologies by Gurmit Singh, Aditya Books, pp 378
  38. Eric Eggleston & AWEA Staff. "What Are Vertical-Axis Wind Turbines (VAWTs)?". American Wind Energy Association. Archived from the original on 3 April 2005.
  39. Marloff, R.H. (January 1978). "Stresses in turbine-blade tenons subjected to bending". Experimental Mechanics. 18 (1): 19–24. doi:10.1007/BF02326553.
  40. Rob Varnon (2 December 2010). "Derecktor converting boat into hybrid passenger ferry". Connecticut Post. Retrieved 25 April 2012.
  41. "Modular wind energy device – Brill, Bruce I". Freepatentsonline.com. 19 November 2002. Retrieved 6 November 2013.
  42. Hewitt, Sam; Margetts, Lee & Revell, Alistair (18 April 2017). "Building a digital wind farm". Archives of Computational Methods in Engineering . 25 (4): 879–899. doi:10.1007/s11831-017-9222-7. PMID   30443152.
  43. Navid Goudarzi (June 2013). "A Review on the Development of the Wind Turbine Generators across the World". International Journal of Dynamics and Control. 1 (2): 192–202. doi:10.1007/s40435-013-0016-y.
  44. Navid Goudarzi; Weidong Zhu (November 2012). "A Review of the Development of Wind Turbine Generators Across the World". ASME 2012 International Mechanical Engineering Congress and Exposition. 4 – Paper No: IMECE2012-88615: 1257–1265.
  45. "Hansen W4 series". Hansentransmissions.com. Archived from the original on 15 March 2012. Retrieved 6 November 2013.
  46. John Gardner; Nathaniel Haro & Todd Haynes (October 2011). "Active Drivetrain Control to Improve Energy Capture of Wind Turbines" (PDF). Boise State University. Retrieved 28 February 2012.
  47. ""Wind Turbine Design Cost and Scaling Model", Technical Report NREL/TP-500-40566, December, 2006, page 35, 36" (PDF). Retrieved 6 November 2013.
  48. "Pomeroy Wind Farm" (PDF). Archived from the original (PDF) on 15 July 2011.
  49. Baqersad, Javad; Niezrecki, Christopher; Avitabile, Peter (2015). "Full-field dynamic strain prediction on a wind turbine using displacements of optical targets measured by stereophotogrammetry". Mechanical Systems and Signal Processing. 62–63: 284–295. Bibcode:2015MSSP...62..284B. doi:10.1016/j.ymssp.2015.03.021.
  50. Using Stereophotogrammetry to Measure Vibrations of a Rotating Wind Turbine
  51. 1 2 Ancona, Dan; Jim, McVeigh. "Wind Turbine – Materials and Manufacturing Fact Sheet". CiteSeerX   10.1.1.464.5842 .
  52. 1 2 Watson, James; Serrano, Juan (September 2010). "Composite Materials for Wind Blades". Wind Systems. Retrieved 6 November 2016.
  53. "Wind turbine blades: Glass vs. carbon fiber". www.compositesworld.com. Retrieved 12 November 2016.
  54. "Materials and Innovations for Large Blade Structures: Research Opportunities in Wind Energy Technology" (PDF). windpower.sandia.gov.
  55. "Wind Power Monthly Webpage".
  56. Ong, Cheng-Huat & Tsai, Stephen W. (2000). "The Use of Carbon Fibers in Wind Turbine Blade Design" (PDF). energy.sandia.gov.
  57. 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; "Archived copy". Archived from the original on 26 November 2012. Retrieved 12 December 2012.CS1 maint: Archived copy as title (link)
  58. Kim, Junbeum; Guillaume, Bertrand; Chung, Jinwook; Hwang, Yongwoo (2015-02-01). "Critical and precious materials consumption and requirement in wind energy system in the EU 27". Applied Energy. 139: 327–334. doi:10.1016/j.apenergy.2014.11.003. ISSN   0306-2619.
  59. Wilburn, D.R.—Wind Energy in the United States and Materials Required for the Land-Based Turbine Industry From 2010 Through 2030—SIR 2011–5036
  60. Buchholz, Peter; Brandenburg, Torsten (2018-01-01). "Demand, Supply, and Price Trends for Mineral Raw Materials Relevant to the Renewable Energy Transition Wind Energy, Solar Photovoltaic Energy, and Energy Storage". Chemie Ingenieur Technik. 90 (1–2): 141–153. doi:10.1002/cite.201700098. ISSN   1522-2640.
  61. Wilburn, David. "Wind Energy in the United States and Materials Required for the Land-Based Wind Turbine Industry From 2010 Through 2030" (PDF). U.S. Department of the Interior.
  62. Yap, Chui-Wei. "China Ends Rare-Earth Minerals Export Quotas". wsg.com.
  63. "Glass fiber market to reach to US$17 billion by 2024". Reinforced Plastics. 60 (4): 188–189. 2016-07-01. doi:10.1016/j.repl.2016.07.006. ISSN   0034-3617.
  64. Young, Kathryn (3 August 2007). "Canada wind farms blow away turbine tourists". Edmonton Journal . Archived from the original on 25 April 2009. Retrieved 6 September 2008.
  65. Anon. "Solar & Wind Powered Sign Lighting". Energy Development Cooperative Ltd. Retrieved 19 October 2013.
  66. Small Wind, U.S. Department of Energy National Renewable Energy Laboratory website
  67. Meyers, Johan (2011). "Optimal turbine spacing in fully developed wind farm boundary layers". Wind Energy. 15 (2): 305–317. Bibcode:2012WiEn...15..305M. doi:10.1002/we.469.
  68. "New study yields better turbine spacing for large wind farms". Johns Hopkins University. 18 January 2011. Retrieved 6 November 2013.
  69. M. Calaf; C. Meneveau; J. Meyers (2010). "Large eddy simulation study of fully developed wind-turbine array boundary layers". Phys. Fluids. 22 (1): 015110–015110–16. Bibcode:2010PhFl...22a5110C. doi:10.1063/1.3291077.
  70. Dabiri, J. Potential order-of-magnitude enhancement of wind farm power density via counter-rotating vertical-axis wind turbine arrays (2011), J. Renewable Sustainable Energy 3, 043104
  71. G.J.W. van Bussel, PhD; M.B. Zaaijer, MSc Reliability, Availability and Maintenance aspects of large-scale offshore wind farms page 2 Delft University of Technology , 2001.
  72. "Iberwind builds on 98% availability with fresh yaw, blade gains". 15 February 2016. Retrieved 30 May 2016.
  73. Morten Lund (30 May 2016). "Dansk firma sætter prisbelønnet selvhejsende kran i serieproduktion". Ingeniøren . Retrieved 30 May 2016.
  74. Jeremy Fugleberg (8 May 2014). "Abandoned Dreams of Wind and Light". Atlas Obscura. Retrieved 30 May 2016.
  75. Tom Gray (11 March 2013). "Fact check: About those 'abandoned' turbines …". American Wind Energy Association . Retrieved 30 May 2016.
  76. "Aldrende havmølleparker åbner marked for klog nedrivning". Ingeniøren. Retrieved 20 May 2016.
  77. 1 2 3 "Advantages and Disadvantages of Wind Energy – Clean Energy Ideas". Clean Energy Ideas. 2013-06-19. Retrieved 2017-05-10.
  78. "Residential Wind Energy Systems – Bergey Wind PowerBergey Wind Power". bergey.com. Retrieved 2017-05-10.
  79. "About Wind Energy: Factsheets and Statistics". www.pawindenergynow.org. Retrieved 2017-05-10.
  80. "Turbine Size". Fraunhofer Wind Monitor.
  81. Parisé, J.; Walker, T. R. (2017). "Industrial wind turbine post-construction bird and bat monitoring: A policy framework for Canada". Journal of Environmental Management. 201: 252–259. Bibcode:2013JEnvM.127..300K. doi:10.1016/j.jenvman.2017.06.052. PMID   28672197.
  82. Hosansky, David (April 1, 2011). "Wind Power: Is wind energy good for the environment?". CQ Researcher.
  83. Sovacool, B. K. (2013). "The avian benefits of wind energy: A 2009 update". Renewable Energy. 49: 19–24. doi:10.1016/j.renene.2012.01.074.
  84. Wittrup, Sanne. "Power from Vestas' giant turbine" (in Danish. English translation ). Ingeniøren , 28 January 2014. Retrieved 28 January 2014.
  85. "The world's most powerful available wind turbine gets major power boost | MHI Vestas Offshore". www.mhivestasoffshore.com. 2018. Retrieved 22 September 2018.
  86. "MHI Vestas launches 9.5MW V164 turbine in London". www.mhivestasoffshore.com. Retrieved 22 September 2018.
  87. http://www.windpowermonthly.com/article/1401293/siemens-confirms-8mw-turbine
  88. "Visits : Big wind turbine". Archived from the original on 1 May 2010. Retrieved 17 April 2010.
  89. "Wind Energy Power Plants in Canada – other provinces". 5 June 2010. Retrieved 24 August 2010.
  90. https://en.wind-turbine-models.com/turbines/319-mbb-messerschmitt-monopteros-m50
  91. http://www.windpoweroffshore.com/article/1207686/close---aerodyns-6mw-offshore-turbine-design
  92. http://www.windpowermonthly.com/article/1188373/ming-yang-install-65mw-offshore-turbine
  93. David Weston. "Aerodyn 6MW connected to grid" 12 March 2015. Archive
  94. http://www.windpowermonthly.com/article/1400374/nordex-installs-230-metre-onshore-turbine
  95. "EXCLUSIVE: Vestas tests four-rotor concept turbine". Windpower Monthly . Retrieved 20 April 2016.
  96. Sanne Wittrup. "Vestas rejser usædvanlig ny multirotor-vindmølle". Ingeniøren . Retrieved 20 April 2016.
  97. Video of quadrotor on YouTube
  98. "Surpassing Matilda: record-breaking Danish wind turbines" . Retrieved 26 July 2010.
  99. http://www.guinnessworldrecords.com/world-records/highest-altitude-wind-generator
  100. http://www.lehighvalleylive.com/bethlehem/index.ssf/2013/08/northampton_community_college_53.html
  101. https://www.bbc.com/news/uk-scotland-scotland-business-34694463

Further reading