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Many machine topologies could be classified by the primary force used to extract the energy. For example, a Savonious wind turbine is a drag-based machine, while a Darrieus wind turbine and conventional horizontal-axis wind turbines are lift-based machines. Drag-based machines are conceptually simple, yet suffer from poor efficiency.
According to Betz's law, no wind turbine of any mechanism can capture more than 16/27 (59.3%) of the kinetic energy in wind. The factor 16/27 (0.593) is known as Betz's coefficient. Practical utility-scale wind turbines achieve at peak 75–80% of the Betz limit. [2] [3] The Betz limit is based on an open-disk actuator.
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USCGC Eastwind (WAGB-279) was a Wind-class icebreaker that was built for the United States Coast Guard. Completed in time to see action in World War II, she continued in USCG service under the same name until decommissioned in 1968.
Wind turbine design is the process of defining the form and specifications of a wind turbine to extract energy from the wind. [181] A wind turbine installation consists of the necessary systems needed to capture the wind's energy, point the turbine into the wind, convert mechanical rotation into electrical power , and other systems to start ...
The extreme wind speeds are based on the 3 second average wind speed. Turbulence is measured at 15 m/s wind speed. This is the definition in IEC 61400-1 edition 2. For U.S. waters however, several hurricanes have already exceeded wind class Ia with speeds above the 70 m/s (156 mph), and efforts are being made to provide suitable standards. [8]
Wind farm – group of wind turbines in the same location used to produce electric power. A large wind farm may consist of several hundred individual wind turbines, and cover an extended area of hundreds of square miles, but the land between the turbines may be used for agricultural or other purposes. A wind farm may also be located offshore.
The wind profile power law relationship is = where is the wind speed (in metres per second) at height (in metres), and is the known wind speed at a reference height .The exponent is an empirically derived coefficient that varies dependent upon the stability of the atmosphere.