Wind turbines convert the kinetic energy from wind into mechanical energy. When used with an electrical generator, the rotation of the wind turbine’s blades turns a shaft to produce electricity. There are two basic types of wind turbines: horizontal-axis and vertical-axis. Horizontal-axis wind turbines (HAWT) are the most popular type. They have two or three wing-shaped blades. Two-bladed turbines are operated downwind, with the blades facing away from the wind. By contrast, three-bladed devices are operated upwind. Vertical-axis wind turbines (VAHT) are shaped like an eggbeater and use one or more propellers or aerofoils. The Darrieus turbine is a type of VAHT in which the aerofoils are arranged symmetrically with a zero rigging angle. Although vertical turbines are limited by physical stress, they offer a wide range of operating speeds and easy access to the generator, which is located at the base of the turbine.

Wind turbines contain many parts. The anemometer tracks wind speeds and transfers measurements from the wind vane to the controller, a component which starts the turbine at wind speeds between 8 to 16 miles per hour (mph) and shuts off the turbine at about 65 mph. Gears connect the low-speed shaft to the high-speed shaft and increase the turbine’s rotational speeds from about 30 to 60 rotations per minutes (rpm) to about 1200 to 1500 rpm. With upwind turbines, motor-powered yaw drives are used to keep the rotor facing the wind. Mechanical, electrical, or hydraulic disc brakes can be used to stop the rotor in the event of an emergency. Typically, the gearbox, generator, blades, hub and other components are encased in a nacelle or protective casing.

Selecting wind turbines requires an analysis of specifications, features, and predicted energy production. Product specifications for wind turbines include orientation, number of blades, blade direction, rotor diameter, rated power, maximum power, and temperature range. Cut-in wind speed, cut-out wind speed, rated wind speed, and furling wind speed are additional considerations. In terms of features, wind turbines may provide overspeed protection and blade pitch control. Options include low-end boost, slow-mode operation, electric braking, timed battery equalization, and polarity checking. Predicted energy production can be expressed in tabular format with wind speeds taken at the top of the tower and wind speeds taken at 10 meters (m). The United States Department of Energy (US-DOE) specifies seven wind power classes.

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NREL: Wind Research Home Page Much of the wind industry's success can be attributed to the research conducted at NREL's National Wind Technology Center (NWTC). Funded by the U.S. See National Renewable Energy Laboratory Information

Wind turbine - Wikipedia, the free encyclopedia Wind turbines History Design Manufacturers

Wind and Hydropower Technologies Program: How Wind Turbines... How Wind Turbines Work Wind is a form of solar energy.

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