ETME 491 Fall 2015
Classroom Problems Set #2
Save to an EXCEL file, submit problem set to the indicated D2L Dropbox by the end of class
1. Specs for a 50 KW-rated turbine are shown on the following page. As shown on these
specs, the turbine has a 19.2 meter rotor diameter. The included annual energy production
chart estimates annual energy production for certain average wind speeds:
a. At 8.5 m/s average wind speed at hub-height, the manufacturer’s annual energy
production estimate is 273,000 kWh/yr. For 100% availability, find the capacity factor.
b. Compare this 273,000 kWh/yr annual energy output value with the ideal annual energy
output using the Carlin method @ this same wind speed. (ref: equation 2.82)
2.
The “constant speed with stall control” design of the turbine (above) limits rotor
rotational speed to 43 RPM. Plot tip speed ratio versus wind speed, for wind speeds ranging
from cut-in speed to cut-out speed.
3.
Find Cpmax for this turbine, using λ calculated from the (fixed) 43 RPM value and
three wind speeds:
(a) cut-in wind speed,
(b) 20 m/s wind speed, and
(c) cut-out wind speed.
(ref: Equation 3.40, for ideal assumptions )
4.
Solve for Cpmax for this 3-blade turbine at a 20 m/s wind speed, with lift/drag ratio
Cl/Cd = 100, and for Cl/Cd = 25. Compare your result to Figure 3.34. (Are you in the
ballpark?!)
(ref: Equation 3.145 )