ETME 491
Wind Energy Engineering
Fall 2015
Test #1
Save results to a (single) file. Microsoft EXCEL is recommended. Clearly label the
work performed for each numbered problem. SAVE OFTEN!! Submit test problem
file to the D2L Dropbox prior to the end of class.
Please refer to the supplied Northern Power NPS 100C-24 wind turbine brochure:
1. The annual energy production estimates are provided on page (4) of the brochure, for
average wind speeds of 5.0, 5.5, 6.0, 6.5, 7.0, and 7.5 m/s.
Create a well-labeled table showing (a) the ideal annual energy output using the Carlin
method (ref: equation 2.82), and (b) turbine capacity factor at each of these six wind
speeds. Assume 100% availability.
2. The turbine is available for purchase with tower (hub) heights of 37m, 29m, or 22m. The
rated wind speed for this turbine is 12 m/s. If the turbine experiences this 12 m/s wind
speed at the tallest hub height of 37m, what wind speeds are predicted at each of the
other two hub heights? Display your results in a well-labeled table, where you
(a) Obtain your power law exponent using the “Counihan method” (ref: equation
2.38), with the surface roughness zo value obtained from Table 2.2 for fallow
field terrain.
(b) Obtain your power law exponent using the “Justus method” (ref: equation
2.37.)
3. Published power output at the rated 12 m/s speed is predicted at 94.7 kW. From the
Power Curve provided, approximately what power output could be expected at the wind
speeds you found for the 29m and 22m heights?
4. The energy production numbers on page (4) of the brochure are based on Rayleigh
Wind Distribution assumptions, and standard air density of 1.225 kg/m3. Plot both the
Rayleigh Probability Density Function and Rayleigh Cumulative Distribution Function
graphs for a 7.5 m/s average wind speed.
5. Based on the 7.5 m/s average wind speed probability results of problem 4, what is the
probability that the wind speed will exceed the cutout speed of the turbine?
6. The blade design uses an airfoil with lift coefficient Cl= 1.4450, and drag coefficient Cd=
0.0014. If the turbine rotates at 40 rpm at a 12 m/s wind speed, solve for the maximum
achievable power coefficient Cpmax. (ref: equation 3.145.)