Made from tubular steel (shown here), concrete, or steel lattice. Supports the structure of the turbine. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity.
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Produces 60-cycle AC electricity; it is usually an off-the-shelf induction generator.
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Drives the generator.
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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.
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Measures wind direction and communicates with the yaw drive to orient the turbine properly with respect to the wind.
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Measures the wind speed and transmits wind speed data to the controller.
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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 may be damaged by the high winds.
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Connects the low-speed shaft to the high-speed shaft and increases the rotational speeds from about 30-60 rotations per minute (rpm), to about 1,000-1,800 rpm; this is 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.
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Turns the low-speed shaft at about 30-60 rpm.
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Blades and hub together form the rotor.
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Lifts and rotates when wind is blown over them, causing the rotor to spin. Most turbines have either two or three blades.
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Turns (or pitches) blades out of the wind to control the rotor speed, and to keep the rotor from turning in winds that are too high or too low to produce electricity.
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Stops the rotor mechanically, electrically, or hydraulically, in emergencies.
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Orients upwind turbines to keep them facing the wind when the direction changes. Downwind turbines don't require a yaw drive because the wind manually blows the rotor away from it.
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Powers the yaw drive.
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Determines the design of the turbine. Upwind turbines—like the one shown here—face into the wind while downwind turbines face away.