# Wind Turbine Lab Report

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FIXEDSPEEDVERSUSVARIABLESPEED The aerodynamic efficiency of a wind turbine depends on many elements of rotor design. Airfoil shape, chord length, blade length, blade twist, revolutions per minute (rpm), and angle of attack, are all elements that must be optimized for the expected wind conditions. The design of the airfoil and its angle of attack are critical to the power-producing capacity of the rotor. Each airfoil has an optimum angle of attack to produce an optimum liftto-drag ratio (the point at which the airfoil will have its optimum performance). 3 For a better understanding of how all these factors affect turbine operating modes, we will next provide a brief wind energy tutorial. Figure 5.0a shows the power (rate of flow of…show more content…
By imagining tip speed ratio lines drawn with other slopes on either side of 7, one can see that, even if a turbine operates at variable speed along those lines, a given wind will produce less power from this machine than for the optimal ratio of 7. The other line, λ = 13, divides the positive or power-producing region from the negative or power-consuming (fan) region. Thus, this line defines therunaway speed of a wind turbine, because it gives the unloaded rotor speed for each wind speed. The rotor tips will be traveling thirteen times faster than the wind speed. Finally, this projection shows one way to compare performance of variable- and constant-speed operation. Suppose this wind turbine is operating at a constant speed of 40 rpm and the wind speed is 3 meters per second (m/s). The contours indicate that the machine will be producing less than one kilowatt of power. If the wind suddenly increases to 6 m/s but the machine is constrained to remain at 40 rpm, the operating point has only moved up one level of power. If, on the other hand, the machine had been allowed to increase speed and follow the λ = 7 locus, the operating point will have moved upward three power contour levels for the same 6 m/s