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Brief history Windmills have been around since the Middle Ages. The first recorded evidence of windmills being used for pumping water and grinding grain was in 7 AD in Persia. Then China got a hold of the idea and it spread to Asia, Africa, and the Mediterranean. The European mill appears to have developed independently from the others because the design is so different. The predecessor to our modern windmill dates back to France in 1105 and England in 1180. In the 14th century, the Dutch took windmills to a whole new level with their \u201ctower\u201d mills using canvas sails stretched across four wooden lattice frames like a big X. Their objective was moving enormous amounts of water into higher basins and canals. By the end of the 16th century thousands of windmills were pumping and grinding in western Europe. By the late 19th century, the count was 30,000\u2014and, miraculously, there was still enough wind to go around.
wind power Wind power uses wind turbines which have their own generator built in. A wind turbine looks like a windmill with three blades. When the wind blows, the windmill rotates and the turbine generates electricity
How it Works Wind power uses the same concepts as most other energy sources, using some force to turn a turbine. The turbine will then transfer its energy into a generator where electricity will be produced. The force to turn the turbine in wind energy comes from wind. Traditionally, wind power could only be harnessed in high speed wind locations, where wind is annually over 13mph, but due to new technology and increased efficiency in generators, even lower speed winds can produce cost efficient wind power. These newer technologies include smart windmills where the pitch of the blade can be varied with the strength of the wind to achieve better efficiency.
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How Wind Turbines Work Wind is a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetation. Humans use this wind flow, or motion energy, for many purposes: sailing, flying a kite, and even generating electricity.
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The terms wind energy or wind power describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a generator can convert this mechanical power into electricity.
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So how do wind turbines make electricity? Simply stated, a wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity. Take a look inside a wind turbine to see the various parts. View the wind turbine animation to see how a wind turbine works.
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Inside the Wind Turbine
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Anemometer: Measures the wind speed and transmits wind speed data to the controller. Blades: Most turbines have either two or three blades. Wind blowing over the blades causes the blades to "lift" and rotate. Brake: A disc brake, which can be applied mechanically, electrically, or hydraulically to stop the rotor in emergencies. Controller: The controller starts up the machine at wind speeds of about 8 to 16 miles per hour (mph) and shuts off the machine at about 55 mph. Turbines do not operate at wind speeds above about 55 mph because they might be damaged by the high winds. Gear box: Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from about 30 to 60 rotations per minute (rpm) to about 1000 to 1800 rpm, the rotational speed required by most generators to produce electricity. The gear box is a costly (and heavy) part of the wind turbine and engineers are exploring "direct-drive" generators that operate at lower rotational speeds and don't need gear boxes. Generator: Usually an off-the-shelf induction generator that produces 60-cycle AC electricity. High-speed shaft: Drives the generator. Low-speed shaft: The rotor turns the low-speed shaft at about 30 to 60 rotations per minute. Nacelle: The nacelle sits atop the tower and contains the gear box, low- and high-speed shafts, generator, controller, and brake. Some nacelles are large enough for a helicopter to land on. Pitch: Blades are turned, or pitched, out of the wind to control the rotor speed and keep the rotor from turning in winds that are too high or too low to produce electricity. Rotor: The blades and the hub together are called the rotor. Tower: Towers are made from tubular steel (shown here), concrete, or steel lattice. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity. Wind direction: This is an "upwind" turbine, so-called because it operates facing into the wind. Other turbines are designed to run "downwind," facing away from the wind. Wind vane: Measures wind direction and communicates with the yaw drive to orient the turbine properly with respect to the wind. Yaw drive: Upwind turbines face into the wind; the yaw drive is used to keep the rotor facing into the wind as the wind direction changes. Downwind turbines don't require a yaw drive, the wind blows the rotor downwind. Yaw motor: Powers the yaw drive
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The most efficient modern wind machines have 2 or 3 blades like the propeller of an aircraft. An electricity generator is located inside the head of the machine.The head also rotates to keep the blades pointed into the wind.
•One design of a modern windmill has two curved blades that spin on a vertical axis • strong cables act as “guy ropes” to anchor the mill and keep it upright.
• Most wind machines being used today are the horizontal-axis type. • Horizontal-axis wind machines have blades like airplane propellers . • A typical horizontal wind machine stands as tall as a 20-story building and has three blades that span 200 feet across. • The largest wind machines in the world have blades longer than a football field! Wind machines stand tall and wide to capture more wind
Vertical-axis • Vertical–axis wind machines have blades that go from top to bottom and the most common type (Darrieus wind turbine) looks like a giant two-bladed egg beaters. • The type of vertical wind machine typically stands 100 feet tall and 50 feet wide. • Vertical-axis wind machines make up only a very small percent of the wind machines used today.
•High Torque •Low Velocity •High Solidity •Water Pumping
•High Velocity •Low Torque •Low Solidity •Electricity
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Materials
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Raw Materials
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Windmills can be made with a variety of materials. Post mills are made almost entirely of wood. A lightweight wood, like balsa wood, is used for the fan blades and a stronger, heavier wood is used for the rest of the structure. The wood is coated with paint or a resin to protect it from the outside environment. The smock and tower mills, built by the Dutch and British prior to the twentieth century, use many of the same materials used for the construction of houses including wood, bricks and stones.
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The main body of the fan-type mills is made with galvanized steel. This process of treating steel makes it weather resistant and strong. The blades of the fan are made with a lightweight, galvanized steel or aluminum.
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One of the strongest and stiffest construction materials available for wind turbine blades is carbon-fibre in an epoxy resin matrix. However, this is very expensive and can only be used by some blade manufactures for highly loaded parts of the rotor blades - when stiffness is critical. Modern rotor blades (up to 126 m (413 ft) diameter) are made of lightweight glass reinforced plastic (GRP) with an epoxy or polyester resin matrix. Smaller blades can sometimes be made from aluminum however GRP is the most common material for modern wind turbine blades. In sum, wind turbine blades can be made from a wide variety of materials, though some are more effective than others.
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Wood and canvas sails were originally used on early windmills due to being cheap and easily manufactured. Unfortunately, they require much maintenance over their service life. Also, they have a relatively high drag (low aerodynamic efficiency) for the force they capture. For these reasons they were superseded with solid airfoils.
Disadvantages
Advantages Wind is free, meaning that wind farms need no fuel.
It produce no waste or greenhouse gases, making them great for the environment.
Wind is also a renewable resource; therefore it won’t run out like coal or other fossil fuels.
Wind farms can also be tourist attractions, generating more revenue that way, and helping the wind farm out.
Wind power is also quite useful for supplying power to remote areas, meaning it can go where other power sources cannot. Wind farms are also quite useful in the fact that the land under the wind towers can still be used for farming.
disadvantages
• They include the unpredictable behavior of wind. • The unsightliness of the wind towers. • Birds are sometimes killed in the blades. • Wind power can also effect television reception. • It can be somewhat noisy for an entire wind farm.
Windmills in the Philippines
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Power-generating windmills in Bangui Bay, Ilocos Norte, northern Philippines. Photo: AFP
Windmills in the Philippines •
Located at Bangui Bay, in the Ilocos Norte province of the northern Philippines, this wind farm is the first source of clean energy to be introduced to the many-islanded nation of 84 million folks, thus far reliant upon oil and gas for their needs.
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The project is the work of a private company, Northwind Power Development Corp, which is run by a Danish fellow and who received the bulk of its funding through no-interest loans provided by the Danish government.
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15 turbines, standing on 23 story high masts, starting pumping out juice back in May and now provide 24.75 megawatts of power, 40% of the supply in the Ilocos Norte province. The boost in electricity supply has provided power to many in the region for the first time.
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Costing more than 48 million dollars, which translates into about 2 million dollars per megawatt, is more than double the start-up cost of a normal power plant running on conventional fossil fuel and would not have been viable without the interest-free loans from the Danish International Development Agency.
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Since the project has been completed, Niels Jacobsen, the president and CEO of the company has had government and stateowned power company officials from across the country requesting help to try and replicate these windmills throughout the country.
principles
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Transmission (mechanics)
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Using the principle of mechanical advantage, transmissions provide a torque-speed conversion (commonly known as "gear reduction" or "speed reduction") from a higher speed motor to a slower but more forceful output.
