History of Wind Energy
Wind power is the product of the conversion of kinetic energy of wind into other forms of energy (electrical or mechanical). Today it is mostly converted into electricity through a wind farm, while in the past wind power was immediately used on site as a motive power for industrial and pre-industrial (such as, for example, in windmills). First of all renewable energies for the cost-production, was the first form of renewable energy by man after the discovery of fire.
Towards the end of 2009, the generating capacity of wind turbines worldwide was 157.9 gigawatts, equivalent to 1.5% of the electricity consumed in the world and is growing rapidly, notandosi a doubling in the three years between 2005 and 2008. Some countries have achieved a drag coefficient of wind power is very high (sometimes with government incentives), for example, in 2008, 19% of electricity production reached base from Denmark, 13% of production in Spain and Portugal, 7% in Germany and the Republic of Ireland. In May 2009, eight countries in the world had farms that sell electricity generated aero-reaching commercial profits.
The wind farms are connected to electricity grids, the smaller setups are used to provide electricity to isolated locations. The power companies are increasingly using the system account that energy is to buy the excess energy produced by small domestic wind turbines. For some aspects of wind energy is an attractive source as an alternative to fossil fuel, since it is abundant, renewable, widely distributed, clean and practically does not produce greenhouse gas (if not during the production of basic components, such as aluminum blades). However, the construction of "wind farms" does not receive unanimous consent because of their impact on the landscape and other issues, such as noise and danger of the plants for birds.
The first European windmills carrying water or moving the mill to grind the grain, in the Netherlands were used to pump water from the polders, greatly improving the drainage after the construction of dams. The Dutch were the largest mills of the time, became and remained the symbol of the nation. These mills were made of wooden frames on which was fixed so that formed the canvas sails driven in rotation by the wind.
During the nineteenth century came running thousands of windmills in Europe, in America, especially for irrigation purposes. Later, with the invention of steam engines, were abandoned for the cost of coal, then the cheap.
In the seventies, the rise in energy prices has reawakened interest in the machines that use the power of the wind, so, many countries have increased funding for research and development of wind energy.
Between 2000 and 2006, global installed capacity has quadrupled. In 2005, the new installed capacity was 11,000 megawatts in 2006 and to 15,000 in 2007 to 20,000 megawatts. Despite the economic crisis, 2008 was a record year for wind energy, with over 27,000 megawatts of new capacity installed worldwide. This exponential growth has led to at the end of 2008 a cumulative total capacity of 120,000 megawatts, producing electricity equal to over 1, 5% of global demand for energy , and it is expected that by the end of 2009 , we can get 2%. With these high growth rates it is estimated that every three years can be increased by 1 percentage point coverage of global demand for energy by this source of energy.
Operation And Types
Its use, relatively simple and inexpensive is implemented by means of wind machines divided into two groups according to the type used to form the basis defined wind turbine:
· Vertical axis wind generators are independent of the direction of the wind;
· Horizontal axis wind turbines, in which the rotor orientation (actively or passively) perpendicular to the direction of the wind.
The wind turbines since 1985 have drastically improved the performance, size and cost. These generators are able to switch between production of a few kilowatts to 3 megawatts of power tips for more efficient production and a typical market of 1.5 MW, with a minimum wind speed of 3-4 m / s. A generator is vertical or horizontal position requires a minimum wind speed (cut-in) of 3-5 m / s and delivers the power project at a wind speed of 12-14 m / s. High speed (20-25 m / s speed, cut-off) the wind turbine is stopped by the braking system for safety reasons. The blockage can occur with brakes that lock the rotor or with methods that are based on the phenomenon of stall and "hide the blades in the wind."
There are also mobile generators, blades that follow the inclination of the wind, keeping the amount of electricity produced by, and double-stranded to double the electrical power produced. Wind generators are silent, the main problem is the size of the blades and the lack of generators microprobes not visible to the naked eye that would address the negative impact on the landscape.
The rpm dell'aerogeneratore are highly variable, as is the wind speed, but the grid frequency must be constant at 50 hertz, so the rotors are connected to a series of drives before entering the energy network.
The kinematics of the wind turbine is characterized by low friction, no heat and a cooling system (oil and water) and a maintenance cost was almost nil. The world's leading manufacturers of wind turbines are German and Danish companies: Vestas, Enercon, Siemens, Gamesa Wind, GE Wind, Nordex, NedWind, Enron Wind. There are about 26 companies that manufacture wind turbines.
A vertical axis wind turbine (VAWT, Vertical Axis Wind Turbines in English) is a type of wind machine characterized by a reduced number of moving parts in its structure, which gives it a high resistance to strong winds, and opportunity to exploit any wind direction without having to constantly refocus. It is a very versatile machine, suitable for home use as the centralized production of electricity in the order of gigawatts (one turbine meet the electricity needs of about 1,000 average homes).
The traditional wind turbines have, almost without exception, the horizontal axis of rotation. This feature is the main limitation to the realization of much larger machines than those currently produced: the static and dynamic requirements that must be respected not to suspect rotors with diameters much greater than 100 meters and height of a tower more than 180 meters. These dimensions relate to machines for exclusive off-shore installation. The machines have the largest on-shore rotor diameter of 70 meters and tower heights of 130 meters. In a car like the radius of the base built over 20 meters. Wind speed increases with distance from the ground, this is the main reason why manufacturers of wind turbine towers in the traditional push shares higher as well. The growth in height, with the diameter of the rotor, which makes it possible static complications are the cause of the machine, which requires complex and expensive foundations and sophisticated strategies of treatment in case of sudden gusts of wind too strong.
Vertical axis wind machines have been designed and built since 1920. The substantially less efficient than those with horizontal axis (30%) has in fact contained use in laboratories. The only industrial installation that exists today is to Altamont Pass in California, produced by FloWind in 1997. The installation is being dismantled because of the economic difficulties of the manufacturer, which is in bankruptcy. We tried to optimize a lot of these machines, making them very competitive, the latest prototype, working in many more hours per year than the horizontal axis, have a greater overall efficiency. Savonius wind turbine is a type of vertical axis wind turbine, used for the conversion of wind torque on a rotating shaft. Devised by the Finnish Sigurd J. Savonius in 1922 and patented in 1929, is one of the simplest turbines.
A horizontal axis wind turbine (HAWT, English Horizontal Axis Wind Turbines) is formed by a steel tower to heights between 60 and 100 meters on top of which is a wrapper (gondola) that contains an electrical generator driven by a rotor blades 20 meters long (usually 2 or 3). It generates an output varies widely, typically 600 kW, equivalent to the electricity needs of 500 families or 1,000 homes. The windmill is a historical example of generating a horizontal axis. As the vertical axis generators also the horizontal axis require a minimum speed of 3.5 m / s and deliver the power of design to a wind speed of 12-14 m / s. At high speeds (20/25 m / s) the wind turbine is stopped by the braking system for safety reasons.
Mini-Turbine And Micro Wind
They are small plants suitable for home use or to supplement the power consumption of small businesses. Usually refers to small wind systems with a nominal power between 20 kW and 200 kW, while microeolico means systems with power ratings below 20 kW. For these small installations the installation price is higher, reaching around € 1500-3000 per kW installed, as the market for this type of system is still underdeveloped, among the cases, the rules and regulations, unlike the Photovoltaic, throughout most of Europe does not support their dissemination, because of the problems of landscape impact of wind turbines. These systems can take advantage of the specific conditions of the site where the installation is done. They are adaptable plants that are able to exploit is that strong winds and they manage to intercept the sudden gusts typical of the Apennines.
The term "offshore wind" means facilities installed a few miles from the coast of seas or lakes, to better utilize the strong currents of exposure to these areas. Spain has carried out a feasibility study for a period of one year throughout the country to determine the areas most ventilated and continuously, and then the candidate sites to install central medium-large size. Spain has extended the measurements by fixed and mobile units also to the entire coast, as well as hills and mountains, preferring the off-shore wind. After widespread MicroPlant in individual homes, and a decentralization of energy, now made a few centralized plants for the production of a few gigawatts per wind farm.
For Havsui, Norway, will be built the largest offshore wind farm in the world, which will provide 1.5 gigawatts of electric power . In the United Kingdom will be carried out an extensive set of generators offshore by 2020 capable of producing enough electricity to power households. The plan provides facilities for 20 gigawatts will be added to the 8 gigawatts already approved plants . In 2008, the Fund reversed the British Crown, which owns the maritime areas of Britain, up to about 20 km from the coast, with the program Clipper's Britannia Project, has decided to invest in large wind turbines off-shore power greater than 5 megawatts .
The floating offshore wind turbines will be installed even in very deep sea sites. Imitating the technology of oil rigs, floating wind turbines are installed offshore and exploit the coastal winds. The project uses a three-point anchoring system (steel cables anchored to the seabed), similar to that used in oil platforms . Hydro, a Norwegian company that operates in the energy sector, has placed a prototype of this turbine near Karmay, an island south east of Norway and possibly near an oil installation with the aim to supply it with renewable energy.
Wind-Hydrogen Hybrid System
Wind energy has an intermittent nature, which has led to many methods of energy storage technologies, including production of hydrogen through water electrolysis. The hydrogen is subsequently used to generate electricity when the energy demand can not be sustained only by the wind. The energy stored in hydrogen is converted into electricity through fuel cells or with a combustion engine connected to an electric generator. In Denmark, in May 2007 was built the first central European wind-hydrogen.
High Altitude Wind
Innovative ideas include the creation of so-called high-altitude wind, which uses high winds quota.Tra projects currently under consideration or under construction include the Kite Wind Generator (which has two main strands of the project: the Stem and KiteGen KiteGen the Carousel) whose operation is based on that of kitesurfing. This system eliminates the static and dynamic problems that prevent the increase in power (ie size) obtained by the traditional wind turbines. The problem of "catching" the wind is solved by the idea of using power kites (Power Kites) in KSU Stem, these airfoils are connected by cables to one or more pairs of motors / generators, which are also used for control of the wing; operation in two stages, in which the airfoil goes up and down in flight.
During the ascending phase, the airfoil exerts traction on the wires, which transfer the motion to the generator: it is the active stage during which energy is produced and, while descending, the generators are being exploited as a driver for the recovery of cables and wing (using about 5% of the energy produced during the previous "active"). In August 2006 the first prototype was built by the name Mobilegen (small, transportable with a normal commercial vehicle), which has already been able to generate a peak of 80 kW of electricity.
It is currently under construction in Sommariva Perno (CN), the first prototype "industrial" pre-series, which is expected to start production of 1 MW to 3 MW to pass finally, when this technology will deliver the full potential expected. In KiteGen Carousel, however, the kites are integral to the perimeter of the turbine. The power kites flying second predetermined trajectories, which allow you to transform the force exerted on the cables in a pair agree overall that rotates the arms of a carousel with a vertical axis. In practice, power kites are the turbine blades, allowing it to rotate around a vertical axis, greatly simplifying the problems of the foundation and stiffness.
The Twind Technology is based on using a pair of balloons stationed at altitudes above 800 meters on the ground and restrained by cables that also function as an element of transmission. When a ball is dragged horizontally by the wind, which pushes on the surface of its canopy, the other ball, sailing closed, is shown on the vertical platform driven by the same cable connected to the first ball. At the end of the unwinding of the cable, came all the way, an automatic mechanism by the end of the wings to sail the first ball and work the opening of the second wing sail, which means that the functions of the two balls are reversed by replicating the same dynamics. This technology enables alternative energy through the continuous movement of the cable attached to two balloons.
Another project is the study Skymill, generator, horizontal axis whose innovation is the placement of the generator, and then the heavier part, directly on the ground. The rotor is instead a height and is connected to the generator via a special cable that transmits the rotation between the two. The rotor, made of very light materials, is supported by the wind itself through a sail along with a balloon that is used only in the total absence of wind or during maintenance operations on the ground to lift or carry the system. This allows you to get to the highest altitudes of horizontal conventional generators and consequently to a greater manufacturability.
In 2008, the United States of America has brought the new installed capacity over 8,300 megawatts (the previous world record, also held by the U.S., was 5,200 megawatts in 2007), making it the world leader in wind power with a accumulated more than 25,000 megawatts, was previously the leader of Germany, now in second place with a total capacity of 23,900 megawatts being installed 1,665 megawatts in 2008, in line with the previous year when they were installed in 1667.
Spain holds the third position worldwide with 16,700 megawatts of combined power and 1,600 MW installed in 2008 has decreased compared to 2007 where he had produced over 3600. On the night of November 5, 2009, Aeolus-electric power production has reached 45% of the total production of electricity in Spain. China has almost doubled since 2007, the newly installed capacity, rising from 3,600 megawatts to 6,300 in 2008, representing the second world record after the U.S., enabling China to surpass India and to attest to the fourth position with 12,200 megawatts total. India is in fifth place with a combined capacity of close to 10,000 megawatts, 1,800 megawatts installed in 2008 in line 2007, when he was installed in 1700.
The U.S., Germany, Spain, China and India alone account for more than 70% of global wind power. In 2009, the newly installed power in Italy was 1100 MW of 950 for France and the United Kingdom of 836. These three countries are located respectively in sixth, seventh and eighth place with a combined capacity of 4850 megawatts (Italy) , 3400 megawatts (France) and 3200 megawatts (United Kingdom) . In Denmark, the electricity produced with this system has reached 23% of Italy, Spain 9% and 7% in Germany .
The installation cost is about € 1.5 per watt (for comparison, a photovoltaic system will cost about € 5 per watt). For the turbines there were significant increases due to rising raw material costs. In 2008, the land cost is € 1.38 million per megawatt, with an increase of 74% over the last three years. Off shore the cost is € 2.23 million, an increase of 48% over the last three anni.Nel world and particularly in the United States the cost of turbines is declining rapidly for several reasons including increased competition. They came in the second half of 2010 average prices for large orders of less than € 1 million per megawatt. After years in which the cost has gone up, now (2010/2011) we are dealing with falling prices.
For Italy, these prices do not correspond to reality. The ANEV published prices equal to 1.59 million euro per megawatt. The cost of production varies depending on the average wind speed in the area, and is optimal when the area will have twenty fairly constant with an average speed exceeding 5 meters per second (18 km / h). According to the report by the International Energy Agency in 2005, the average production cost of wind energy is about $ 90 per megawatt hour, compared with about 35 of nuclear energy. The cost does not take into account the burdens due to the solution of some technical problems that renewable sources are in most cases, such as the need to provide back-up generating capacity needed to ensure the provision of electricity in case there is no wind.
The cost of installation in Italy, referring to installations with a rated output greater than 600 kilowatts, varies between 1500 and 2000 euro per kilowatt-hour , and the price varies depending on the complexity of the orography of the land where the plant is installed, the class of machine has been installed, the difficulty of connecting to the mains. A power of 10 MW, connected to the network at high voltage, would cost between 15 and 20 million €, while for a power plant connected to the network of medium voltage (3-4 MW), the cost is compressed between 1.2 and 1, 5 million euro per megawatt. The only items of expenditure relate to the total installation and maintenance, since there are no supply costs of producing energy source. In relation to the area occupied, a wind farm does not take away the opportunity to continue the previous activities on that land (sheep, etc.)..
In the U.S. the cost of installed power plants to micro-wind and mini-wind turbines ranging from 3000 to $ 5000 per kilowatt . Very often, domestic turbines are installed in inappropriate places and positions, resulting in low yields (5-20%), however in general, to greater heights it has a higher capacity factor.
If a user such as a house or agricultural land install a 20 kW wind turbine (with a total cost of generator, tower and connection of about 40,000 to 100,000 €) and this provides an output equal to 20% of the rated power will an actual cost of € 40,000 to 100,000 for 4 kW average power of the actual average (10,000 to 25,000 € / kW). This cost of the average power is approximately 2-10 times that of nuclear energy (The mini-wind does not benefit from mass production, also requires a lot of maintenance and the cost of electricity actually produced from wind tends to be even less convenient), but not for users domestic industry may be acceptable as it allows energy self-sufficiency. With the energy bill may be recovered in 5000 to 10,000 € per year, if the device is placed in a proper, on a very high pylon.
For the economic optimization of the system micro or mini-wind is necessary to choose an appropriate height of the axis of the blades (the ideal is between 30 and 100 meters in the plain, but may be less on a hill). The areas where it was measured more consistently than twenty economically exploitable Sardinia, Sicily, the Tuscan-Emilian Apennines, the Apennine Mountains in Basilicata and in the border between Campania, Calabria, Molise, Puglia .
Are being developed new systems of wind turbines "roof" of low-cost ($ 500) and low yield (40,000 kWh per month) as that of Chad Maglaque, which does not need an expensive inverter and therefore can be connected to the network power supply, other electrical equipment directly supplying low .
The maximum efficiency of a wind farm can be calculated using Betz's Law, which shows that the maximum power that a generator can produce any (such as a windmill) and 59.3% of that possessed by the wind that goes through. This efficiency is the maximum attainable, and a wind turbine with an efficiency of 40% to 50% is considered excellent.
Wind power plants allow large economies of scale that reduce the cost of the kilowatt-hour electricity with the use of long blades and efficient than the production of several megawatts each. Increased electric power in terms of megawatts means big savings in production costs, but also bigger blades and visible from great distances, with a greater environmental impact on the landscape. A green, in an attempt to camouflage the wind turbines within the landscape, at least in part mitigates this problem, given the heights of the plants. For this reason, despite this greater economy and efficiency of plants for large-scale, mostly it is decided for a compromise between the economic return, which leads to larger systems, and landscape impact.
· Since, for reasons of safety and efficiency, wind generators can only operate in certain wind conditions, wind energy is produced intermittently, and therefore is not programmable. This situation makes the wind industry can not fully replace traditional sources such as fossil fuels or hydro, for which the power output is constant or controlled directly as needed. Wind energy is therefore mainly the scope of its integration with existing networks .
· On land, the most windy and therefore more suitable for wind installations are usually peaks, the ridges of hills and mountains or the coast. Modern plants, although they are also aesthetically valuable, because of their large size are visible from great distances and can cause a disturbance of the landscape. However, the wind installations are fully reversible (low cost of dismantling, complete restoration of the existing environmental conditions and lack of permanent alteration of the landscape), unlike other types of such thermoelectric power plants, nuclear and hydroelectric power, the impact of environmental, aesthetic and ecological, is in fact irreversible for the high cost (dams, nuclear facilities) and for a long time (radioactive waste).
· The mortality risk from impact to migratory birds is certainly realistic, particularly for larger systems. It was however noted a mortality rate much lower than that normally resulting from the windows of buildings and cars.
· The sound of a wind turbine, mainly due to the incident wind on the blades, according to some studies favor, in residents of homes in the immediate vicinity, the so-called "wind turbine syndrome," a set of neurological disorders in the background.
· The authorities responsible for air traffic control in some countries argue that the plants can interfere with the activity of the radar, and because the high RCS (Radar Cross Section) radar echo of the towers would be difficult to remove, and because the blades in continuous rotation could be mistaken for aircraft movement. Constitute a danger for drivers who rely on night vision systems (infrared or light intensifier. They are mostly bad weather radars.
· The extreme variability of the wind resource implies the need to support thermal plants using coal, oil or natural gas to meet the need for peak power.
· You do not experience a variability of costs due to rising fuel prices.
· Once you determine the cost of construction of the plant is impracticable to determine the amortization period (a large electrical system will begin to be paid only over the building after about 6-10 years, accumulating interest of 24-50% compared to the initial investment) .
· The size of wind farms are easily scalable in power, particularly suited to meet the demand for small towns and sparsely populated provinces.
· The costs of maintenance and decommissioning are relatively low, many components are recyclable and reusable.
· Does not produce the greenhouse gas CO2, except in minimal amounts in respect of construction of the plant.
· The wind is a renewable resource, energy, and for the whole world was estimated at around 870 TW / year, for the most part not economically exploitable.
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