wind turbines are devices that convert kinetic wind energy into electrical energy.
Wind turbines are produced in a variety of vertical and horizontal axes. The smallest turbines are used for applications such as battery charging for additional power for ships or caravans or for turning on traffic alerts. A slightly larger turbine can be used to make contributions to a domestic power supply while reselling unused power to utility suppliers through the power grid. Large turbine arrays, known as wind farms, are becoming an increasingly important source of intermittent renewable energy that is used by many countries as part of a strategy to reduce their dependence on fossil fuels. One assessment states that, in 2009, the wind has "the lowest relative greenhouse gas emissions, the least demand for water consumption and... the most favorable social impact" compared to photovoltaic, hydro, geothermal, coal and gas.
Video Wind turbine
Histori
Wind power may be used in Persia (now Iran) around 500-900 AD. The Windwheel of Hero of Alexandria marks one of the first examples of the wind that powered the engine in history. However, the first practical wind power plant is known to be built in Sistan, Iran's eastern province, from the 7th century. This "Panemone" is a vertical shaft windmill, which has a long vertical drive shaft with a rectangular blade. Made of six to twelve reed-covered screens or duster, this windmill is used to grind grain or draw water, and is used in the grinding and cane industry.
Wind power first appeared in Europe during the Middle Ages. The first historical records of its use in England date from the 11th or 12th century and there are reports of German crusaders who took the skills of making their windmills to Syria around the year 1190. In the 14th century, the Dutch windmill was used to dry the Rhine delta. Sophisticated wind turbines are described by Croatian inventor Fausto Veranzio. In his book Machinae Novae (1595) he describes a vertical axis wind turbine with a curved or V-shaped blade.
The first wind turbine power plant was a battery charging machine that was installed in July 1887 by Scottish academic James Blyth to start his holiday home in Marykirk, Scotland. A few months later the American inventor, Charles F. Brush, was able to build the first wind turbine that operated automatically after consulting with local University professors and colleagues, Jacob S. Gibbs and Brinsley Coleberd, and managed to get a peer-reviewed blueprint for electricity production in Cleveland, Ohio. Although the Blyth turbines are considered uneconomical in the UK, power generation by wind turbines is more cost-effective in countries with widespread populations.
In Denmark in 1900, there were about 2500 windmills for mechanical loads such as pumps and factories, yielding a combined peak power estimate of about 30 MW. The largest engine is in a 24-meter (79 ft) tower with a rotor of 23 meters (75 feet) in diameter. In 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 produced 100,000 farm windmills each year, mostly for water pumping.
In the 1930s, wind generators for electricity were common at farms, mostly in the United States where distribution systems had not yet been installed. In this period, high-tensile steel is cheap, and the generator is placed over a prefabricated open steel grating tower.
The pioneer of the modern horizontal-axis wind generator operated in Yalta, USSR in 1931. It is a 100 kW generator on a 30-meter (98 ft) tower, connected to a local 6.3 kV distribution system. Reported to have an annual capacity factor of 32 percent, not much different from the current wind engine.
In the fall of 1941, the first megawatt class wind turbines were synchronized with the power grid in Vermont. The Smith-Putnam wind turbine only ran for 1,100 hours before it crashed. The unit was not repaired, due to lack of material during the war.
The first wind turbine connected to a power grid to operate in the UK was built by John Brown & amp; The company was in 1951 on the Orkney Islands.
Despite various developments, the development of fossil fuel systems almost entirely eliminates wind turbine systems larger than the size of a supermicro. In the early 1970s, however, anti-nuclear protests in Denmark spurred artisan mechanics to develop microturbines of 22 kW. Organizing owners into associations and cooperatives leads to government lobbying and utilities and provides incentives for larger turbines throughout the 1980s and then. Local activists in Germany, a newborn turbine manufacturer in Spain, and large investors in the United States in the early 1990s then lobbied policies that encouraged industries in those countries. Then companies formed in India and China. In 2012, the Danish company Vestas is the largest wind turbine producer in the world.
Maps Wind turbine
Resources
The quantitative measure of wind energy available at any location is called Wind Power Density (WPD). This is the calculation of the average annual power available per square meter of the turbine sweep area, and tabulated for different heights above the ground. The calculation of wind power density includes the effect of wind speed and air density. A color coded map is prepared for a specific area described, for example, as "Mean Annual Power Density at 50 Meters". In the United States, the above calculations are included in the index developed by the National Renewable Energy Laboratory and referred to as "NREL CLASS". The higher the WPD, the higher the grade, which ranges from Class 1 (200 watts per square meter or less at 50 m height) to Class 7 (800 to 2000 W/m 2 ). Commercial wind farms are generally located in areas with Class 3 or higher resources, although remote points in other Class 1 areas may be practical for exploitation.
Wind turbines are classified by wind speeds designed for them, from class I to class IV, with A or B referring to turbulence.
Efficiency
Mass conservation requires that the amount of air entering and leaving the turbine be the same. Thus, Betz's law provides the maximum wind power extraction that wind turbines can achieve as 16/27 (59.3%) of the total kinetic energy of air flowing through the turbine.
Output daya teoritis maksimum dari mesin angin adalah 16/27 kali energi kinetik dari udara yang melewati area disk efektif dari mesin. Jika area efektif dari disk adalah A, dan kecepatan angin v, output daya teoritis maksimum P adalah:
- ,
where is ? is the density of air.
Because of the free wind (no fuel costs), wind efficiency to the rotor (including friction and pull of the rotor blades) is one of many aspects that affect wind end prices. Further inefficiencies, such as gearbox losses, generators and converter losses, reduce the power delivered by wind turbines. To protect the component from improper wear, the extracted power is held constant above the rated operating speed as theoretical power increases on the cube of the wind velocity, which further reduces theoretical efficiency. In 2001, commercial utility-operated turbines generated 75% to 80% of the Betz power limit extracted from the wind, at rated operating speed.
Efficiency can decrease slightly over time, one of the main reasons is the carcass of dust and insects on the propellers that alter the aerodynamic profile and essentially reduce the lift power to drag the airfoil ratio. Analysis of 3128 wind turbines older than 10 years in Denmark showed that half of the turbines did not decrease, while the other half decreased production by 1.2% per year. The vertical turbine design has a much lower efficiency than the standard horizontal design.
Type
Wind turbines can spin either from horizontal or vertical axes, which were previously older and more common. They can also include a knife, or without a blado. The vertical design produces less power and is less common.
Horizontal axis
Large three-blade horizontal axis wind turbine (HAWT), with a knife against the wind from the tower produces the majority of wind power in the world today. This turbine has a main rotor shaft and an electric generator at the top of the tower, and should be directed to the wind. Small turbines are moored by simple wind vanes, while large turbines generally use wind sensors combined with the yaw system. Most have a gearbox, which converts the slow rotation of the blade into a faster rotation that is more suitable for moving the electric generator. Some turbines use different types of generators that are suitable for slower input speeds. It does not require a gearbox, and is called a direct-drive, which means they attach the rotor directly to the generator without the gearbox in between. While permanent magnetic direct-drive generators can be more expensive because rare earth materials are needed, these gearless turbines are sometimes preferred over girboks generators as they "eliminate the increase in gear speed, which is prone to accumulated significant accumulation of torque loads, reliability related issues, and maintenance costs. "
Most horizontal axis turbines have a rotor against the wind direction of the supporting tower. Wind fighting machines have been built, as they do not need additional mechanisms to keep them in line with the wind. In high winds, the propellers can also be bent which reduces their sweep area and thus their wind resistance. Regardless of these advantages, the design of the downwind is preferred, because the charge changes 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. It has low torque ripples, which contribute to good reliability. The blades are usually white for daylight visibility by aircraft and their lengths range from 20 to 80 meters (66 to 262 feet). The size and height of the turbine increase from year to year. Offshore wind turbines are built up to 8MW today and have blade lengths up to 80 meters (260 ft). Typically tubular steel towers of multi megawatt turbines have a height of 70 Ã, m up to 120 Ã, m and at extremes up to 160 Ã, m.
Vertical axis
The vertical axis wind turbine (or VAWTs) has a vertically arranged main rotor shaft. One advantage of this arrangement is that the turbine does not need to be directed to the wind to be effective, which is an advantage on sites where wind direction varies greatly. This is also an advantage when turbines are integrated into buildings because they are inherently less manageable. Also, the generator and gearbox can be placed near the ground, using the direct drive from the rotor assembly to the ground-based gearbox, increasing accessibility for maintenance. However, this design produces less energy on average over time, which is a major drawback.
Major disadvantages include relatively low rotation speeds with higher torques and hence higher cost of drive train, inherently lower power coefficients, 360 degree rotation of aerofoils in wind flow during each cycle and hence very dynamic loading. on the blades, the pulsed torque generated by some rotor designs on the drive train, and the difficulty of modeling the wind flow accurately and hence the challenge of analyzing and designing the rotor before making a prototype.
When turbines are installed on roofs, buildings generally direct wind to the roof and this can double wind speed in the turbine. If the height of the turbine tower mounted on the roof is approximately 50% of the height of the building, it is close to the optimum for maximum wind energy and minimal wind turbulence. While wind speeds within the built environment are generally much lower than in open countryside, noise may be of concern and existing structures may not be sufficient to withstand additional stress.
Subtypes of vertical axis designs include:
Darrieus wind turbine
The "eggbeater" turbine, or Darrieus turbine, is named after French inventor Georges Darrieus. They have good efficiency, but produce large torsional ripples and cyclic voltages on the tower, which contributes to poor reliability. They also generally require some external power source, or an additional Savonius rotor to start spinning, because the initial torque is very low. Torque ripple is reduced by using three or more blades which produce greater rotor solidity. Solidity is measured by the area of ​​the blade divided by the rotor region. The newer Darrieus turbine type is not held by man-wires but has an external superstructure connected to the upper cushion.
Giromill
The subtype of Darrieus turbine with a straight blade, as opposed to curved. Various cycloturbine has a variable pitch to reduce the torque pulsation and start its own. The advantages of variable pitch are: high initial torque; relatively wide flat torque curve; higher performance coefficients; operating more efficiently in volatile winds; and a lower blade speed ratio that decreases the knot bending stress. Straight, V, or curved blades can be used.
Savonius wind turbine
It is a pull-type device with two (or more) spoons used in anemometers, Flettner ventilation (usually seen on bus roofs and vans), and in some low-efficiency power turbines with high reliability. They always start themselves if there are at least three spoons.
Twisted Savonius is a modified savonius, with long helices to produce a smooth torque. It is often used as a windturbine on the roof and has even been adapted for ships.
Parallel
The parallel turbine is similar to a crossflow fan or centrifugal fan. It uses ground effect. This type of vertical axis turbine has been tried for years: a unit producing 10 kW was built by Israeli wind pioneer Bruce Brill in the 1980s.
Uncommon type
Design and construction
The design of wind turbines is a careful balance between cost, energy output, and fatigue life. These factors are offset using a variety of computer modeling techniques.
Components
Wind turbines convert wind energy into electrical energy for distribution. Conventional horizontal axis turbines can be divided into three components:
- The rotor, which is approximately 20% of wind turbine costs, includes a knife to convert wind energy into low-speed rotational energy.
- The generator, which is approximately 34% of the cost of wind turbines, includes electrical generators, electronic controls, and most likely gear boxes (eg planet gear box), adjustable speed drives or continuous variable transmission components to convert low speed incoming rotations to a high-speed rotation suitable for generating electricity.
- The surrounding structure, which is approximately 15% of the cost of wind turbines, including the tower and rotor yaw mechanisms.
A 1.5 MW wind turbine of a type often seen in the United States has a high 80 meter (260Ã, ft) tower. The rotor assembly (knife and hub) weighs 22,000 kilograms (48,000 pounds). Nacelle, which contains a generator, weighs 52,000 kilograms (Â £ 115,000). The concrete base for the tower was built using 26,000 kilograms (58,000 lb) of reinforcing steel and contained 190 cubic meters (250 cuÃ, yd) of concrete. The base is 15 meters (50Ã, ft) in diameter and 2.4 meters (8Ã, ft) thick near the center.
Turbine monitoring and diagnostics
Due to data transmission problems, structural monitoring of the wind turbine's health is usually done using some accelerometers and strain gages attached to the nacelle to monitor gearboxes and equipment. Currently, digital image correlations and stereophotogrammetry are used to measure the dynamics of wind turbine blades. These methods usually measure the displacement and strain to identify the location of the defect. The dynamic characteristics of non-rotating wind turbines have been measured using digital image correlation and photogrammetry. Three-dimensional point tracking has also been used to measure the dynamics of wind turbine spinning.
Recent materials and developments
The materials normally used for rotor blades in wind turbines are composites, as they tend to have high stiffness, high strength, high fatigue, and low weight. Resins used for this composite include polyester and epoxy, while glass and carbon fiber have been used for reinforcing materials. Construction can use manual layup techniques or composite resin injection molds. Since the price of glass fibers is only about one tenth of the price of carbon fiber, glass fibers are still dominant.
New design
As competition in the wind market increases, companies are looking for ways to attract greater efficiency from their designs. One of the main ways wind turbines have gained performance is by increasing the diameter of the rotor, and thus the length of the blades. Current turbine strengthening with larger blades reduces the needs and risks associated with system-level redesign. As the size of the blade increases, its tendency to deflect also increases. So, from a material point of view, stiffness-to-weight is very important. Since the propeller must function more than 100 million load cycles over a period of 20-25 years, the knife fatigue life is also very important. By incorporating carbon fiber into parts of the existing blade system, the manufacturer can increase the blade length without increasing the overall weight. For example, the spar cap, the structural element of the turbine blades, generally has a high tensile load, making it an ideal candidate for utilizing enhanced carbon fiber tensile properties compared to glass fibers. Higher stiffness and lower density translates into thinner and lighter blades that offer equivalent performance. In a 10-MW turbine - which will become more common in offshore systems by 2021 - blades can reach over 100 m in length and weigh up to 50 m metric when fabricated from glass fibers. A switch to the carbon fiber inside the structural lane of the blade produces a weight savings of 20 to 30 percent, or about 15 metric tons.
Materials for knives
Some of the most common materials used for turbine blades now and will be in the future are summarized below:
Glass and carbon fiber
The composite stiffness is determined by the stiffness of the fiber and its volume content. Typically, E-glass fibers are used as the main reinforcement in composites. Typically, glass/epoxy composites for wind blades contain up to 75% by weight of glass. It increases stiffness, tensile strength and compression. A promising source of future composite materials is glass fibers with modified compositions such as S-glass, R-glass, etc. Some other special glasses developed by Owens Corning are ECRGLAS, Advantex and the most recent WindStrand glass fibers.
Hybrid hybrid
These include E-glass/carbon, E-glass/aramid and they present an attractive alternative to pure glass or carbon reinforcements. that full replacement will lead to 80% weight savings, and a 150% cost increase, while partial replacement (30%) will lead to only a 90% cost increase and 50% weight reduction for 8 m turbines. The world is currently the longest wind turbine rotor blade, 88.4 m long blade of LM Wind Power made of carbon/glass hybrid composite. However, additional investigation is required for optimal ingredient composition
Polymers and nano-engineered composites
The addition of small amounts (0.5 wt.%) Of nanoreinforcement (carbon nanotubes or nanoclay in composite polymer matrix, fiber sizing or interlaminar coatings may allow to increase fatigue, shear or compressive strength and fracture toughness of composites by 30 -80% shows that the incorporation of small amounts of carbon nanotubes/CNTs can increase the life span by up to 1500%.
Cost
While material costs are significantly higher for all glass fibers than glass/carbon fiber hybrids, there is the potential for remarkable savings in production costs when the price of labor is considered. Utilizing carbon fiber allows simpler designs that use less raw material. The main manufacturing process in blade fabrication is coating layer. By reducing the number of layers of layers, as made possible by thinner blade designs, labor costs may decrease, and in some cases, the equivalent of labor costs for glass fiber blades.
Other materials
Materials for wind turbine parts other than rotor blades (including rotor hubs, gearboxes, frames, and towers) are mostly steel. Modern turbines use several tons of copper for generators, cables, and such. The smaller wind turbines have begun to incorporate more aluminum-based alloys into these components in an effort to make the turbines lighter and more efficient, and can continue to be used increasingly if the fatigue and property strength can be improved. Prestressed concrete has been increasingly used for tower materials, but it still requires a lot of reinforcing steel to meet the needs of turbine power. In addition, the step-up gearbox is increasingly replaced by variable speed generators, increasing the demand for magnetic materials in wind turbines. In particular, this will require an increase in the supply of rare earth metal neodymium.
Recycling
The interest of recycling blades varies in different markets and depends on waste laws and the local economy. Challenges in recycling blades are related to composite materials, made of thermosetting matrices and glass fibers or a combination of glass and carbon fiber. Thermoset matrices can not be reworked to form new composites. So the choice is to reuse knives and composite material elements such as those found in knives or to convert composite materials into new sources of material. In Germany, wind turbine blades are commercially recycled as part of an alternative fuel mixture for cement plants.
Supply
A study of trends in material consumption and requirements for wind energy in Europe found that larger turbines had higher noble metal consumption but lower material input per kW was produced. Current material and stock consumption compared to input materials for various sizes of land systems. In all EU countries, the forecast for 2020 has exceeded and doubled the value consumed in 2009. These countries need to expand their resources to meet demand forecasts for 2020. For example, currently the EU has a 3% world fluorspar supply and that requires 14% by 2020. Globally, major exporting countries are South Africa, Mexico, and China. This is similar to other important and valuable materials needed for energy systems such as magnesium, silver and indium. In addition, the recycling rates of these materials are very low and focus on what can reduce future supply problems. It is important to note that since most of these valuable materials are also used in other emerging technologies, such as LEDs, PVs and LCDs, it is projected that their demand will continue to increase.
A report by the United States Geological Survey estimates material needs projected to meet US commitments to supply 20% of its electricity from wind power by 2030. They do not address the requirements for small turbines or offshore turbines because they were not widely used in 2008, when the study created. They found that there was an increase in common materials such as cast iron, steel and concrete representing 2-3% of material consumption in 2008. Between 110,000 and 115,000 metric tons of glass fiber will be required each year, equivalent to 14% consumption. in 2008. They do not see a high demand increase for rare metals compared to available supplies, but it is important to take into account that rare metals are also used for other technologies such as batteries that increase their global demand. Lastly, while the land may not be regarded as material, it is an important source in spreading wind technology. Achieving the 2030 goal will require 50,000 square kilometers of terrestrial land and 11,000 square kilometers offshore. This does not take into consideration the problem in the US because of its vastness and the ability to use land for agriculture and grazing. A greater limitation for technology will be the variability and transmission infrastructure for higher demand areas.
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 a higher amount of rare metals. Therefore, an increase in wind production will increase the demand for this resource. It is estimated that additional demand for Nd in 2035 may be 4,000 to 18,000 tonnes and Dy could see an increase of 200 to 1200 tonnes. These values ​​represent a quarter to a half of current production levels. However, as technology evolves, driven by inventories and material prices, this rate of estimate is highly uncertain but remains to be monitored.
Reliance on rare earth minerals for components has staked cost and price volatility since China has become a major producer of rare earth minerals (96% in 2009) and has reduced export quotas of these materials. However, in recent years, other producers have increased the production of rare earth minerals and China has reduced its reduced export quota on rare earths leading to increased supply and decreased rare earth mineral costs, increasing the viability of applying variable speed generators in large-scale wind turbines.
Due to technological improvements and widespread implementation, the global glass fiber market may reach US $ 17.4 billion by 2024, compared to US $ 8.5 billion in 2014. Since this is the most widely used material for reinforcement in composites across world, the expansion of end-use applications such as construction, transportation and wind turbines has fueled its popularity. Asia Pacific holds a major share of the global market in 2014 with more than 45% share of volume. But China is currently the largest producer. The industry received subsidies from the Chinese government that allowed them to export them cheaper to the US and Europe. However, due to higher demand in the near future some price wars have begun to be developed to implement anti-dumping strategies such as tariffs on Chinese glass fibers.
Wind turbine on public display
Some areas have exploited the properties of wind turbines that attract attention by placing them in public places, either with a visitor center around their base, or by looking at more distant areas. Wind turbines are generally of conventional horizontal axis, three-bladed design, and generate power to feed the power grid, but wind turbines also serve the unconventional role of technology demonstrations, public relations, and education.
Small wind turbine
Small wind turbines can be used for a variety of applications including residential or offshore, telecom towers, offshore platforms, rural schools and clinics, remote monitoring and other energy-intensive purposes where there is no power grid, or where the grid is unstable. Small wind turbines may be small like fifty watt generators for boat or caravan use. Solar-powered units and hybrid winds are increasingly being used for traffic signs, especially in rural locations, as they do not need to install long cables from the nearest electrical connection point. The US Department of Energy's National Renewable Energy Laboratory (NREL) defines a small wind turbine as smaller than or equal to 100 kilowatts. Small units often have direct propulsion generators, direct current, aeroelastic blades, lifelong pads, and use propellers for wind direction.
Bigger and more expensive turbines generally have powered trains, alternating current, flaps, and are actively directed to the wind. Direct drive generators and aeroelastic blades for large wind turbines are being investigated.
Wind turbine spacing
In most horizontal turbine wind turbines, a distance of about 6-10 times the diameter of the rotor is often highly respected. However, for large wind farms, a distance of about 15 rotor diameters should be more economical, taking into account wind turbines and typical land costs. This conclusion has been reached by research by Charles Meneveau of Johns Hopkins University, and Johan Meyers of Leuven University in Belgium, based on computer simulations that take into account the detailed interactions between wind turbines (wakes) as well as with the entire turbulent layer of atmospheric boundaries.
Recent research by John Dabiri of Caltech suggests that vertical wind turbines can be placed much more closely together as long as alternating rotation patterns are made allowing blades from neighboring turbines to move in the same direction as they approach each other.
Operability
Maintenance
Wind turbines require regular maintenance to remain reliable and available, in the best turbines available to generate energy 98% of the time.
Modern turbines usually have small onboard cranes to lift maintenance equipment and small components. However, large heavy components such as generators, gearboxes, knives and so on are rarely replaced and external heavy lift cranes are required in such cases. If the turbine has a difficult access road, the wrapped crane can be lifted by an internal crane to provide a heavier load.
Repowering
Installation of new wind turbines can be controversial. An alternative is repowering, in which existing wind turbines are replaced with larger, stronger ones, sometimes in smaller quantities while maintaining or increasing capacity.
Demolition
Older turbines in some early cases need not be removed when reaching the end of their lives. Some are still standing, waiting to be recycled or reparations.
The demolition industry is developing to recycle offshore turbines at a cost of DKK 2-4 million per MW, which will be guaranteed by the owners.
Comparison with fossil fuel turbines
Benefits
Wind turbines are generally not expensive. They will generate electricity between two and six cents per kilowatt hour, which is one of the lowest-cost renewable energy sources. And since the technology needed for wind turbines continues to rise, prices will also fall. In addition, there is no competitive market for wind energy, because it does not cost to get the wind. The main cost of wind turbines is 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 cost of installation, as well as provide free energy almost for many years afterwards.
The wind turbine provides a clean energy source, does not emit greenhouse gases and there is no waste product. More than 1,500 tons of carbon dioxide per year can be removed using a one megawatt turbine instead of one megawatt of energy from fossil fuels. Being environmentally friendly and green is a great advantage of wind turbines.
Losses
The wind turbine can be very large, reaching over 140 meters (460 feet) and with a 55-meter (60-year-old) blade, and people often complain about the visual impact.
The environmental impacts of wind power include effects on wildlife, but can be mitigated if proper monitoring and mitigation strategies are implemented. Thousands of birds, including endangered species, have been killed by wind turbine blades, although wind turbines contribute relatively insignificantly to the deaths of anthropogenic poultry. For every bird that is killed by wind turbines in the US, nearly 500,000 are killed by individual cats and wild buildings. In comparison, conventional coal generators contribute more to bird death, with incineration when trapped in smoke pile rises and by poisoning emission by-products (including heavy metal particles and heavy metals from flue gas). Furthermore, marine life is influenced by the introduction of water from steam turbine cooling towers (heat exchangers) to nuclear and fossil fuel generators, by coal dust deposits in marine ecosystems (eg damage to Australia's Great Barrier Reef) and by water acidification from burning of monoxide.
Source of the article : Wikipedia
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