Apparent wind in knots and degrees. Note that a number of additional factors come into play when converting the measurements from the masthead anemometer into the true wind if a high degree of accuracy is required, including the following: In the presence of a current, the true wind is considered to be that measured on the craft drifting with the water over the bottom, and wind with respect to the sea bed as the "ground" or "geographical wind". The apparent wind on board (a boat) is often quoted as a speed measured by a masthead transducer containing an anemometer and wind vane
Variable speed wind turbine Variable speed wind turbine Original models of wind turbines were fixed speed turbines; that is, the rotor speed was a constant for all wind speeds. The tip-speed ratio for a wind turbine is given by the following formula: formula_1 where formula_2 is the rotor speed (in radians per second), formula_3 is the length of a blade, and formula_4 is the wind speed. That is to say, for a fixed-speed wind turbine, the value of the tip-speed ratio is only changed by wind speed variations. In reference to a formula_5-formula_6 graph, which illustrates the relationship between Tip-speed ratio and efficiency, it