WIND ENERGY SYSTEMS - Cd3wd

Chapter 4—Wind Turbine Power 4–50
Figure 30: Torque versus rotational speed for low-solidity 10-m-diameter two-bladed propeller.
model discussed in Chapter 2 to find the average pressure.
2. An anemometer mounted on the nacelle of an operating downwind propeller type turbine
measures an average wind speed of 10 m/s. Estimate the undisturbed wind speed,
assuming this anemometer measures the same wind speed as seen by the propeller.
3. The Sandia 17-m turbine has a diameter of 16.7 m, an area of 187 m 2 , and is spinning
at 42 r/min. The ambient temperature is 15 o C and the pressure is 83 kPa. For each of
the wind speeds 5, 7, 12, and 16 m/s,
(a) Find the tip speed ratio.
(b) Find the coefficient of performance from Fig. 9.
(c) Find the predicted mechanical power output. Compare these values with those
given on Fig. 10.
4. An electric utility decides to add 50 MW of wind generation to its system. If the
individual units are to be rated at 2 MW in a 13-m/s wind at standard conditions and
have efficiencies C pR = 0.32, η mR = 0.94, and η gR = 0.96, what is the required swept
area A of each rotor? What is the rotor diameter, if the rotor is a two bladed horizontal
axis propeller?
Wind Energy Systems by Dr. Gary L. Johnson November 21, 2001