WIND ENERGY SYSTEMS - Cd3wd

Chapter 2—Wind Characteristics 2–42
Figure 18: y versus x for Kansas City and Dodge City, 1970
A word of caution is appropriate about ignoring data points. Note that we do not want to change
the location of any of the points on Fig. 18. We therefore compute F (u i ),x i ,andy i from the original
data set and do not adjust or renormalize any of these values. The summations of Eqs. 55, 56, and 58
are corrected by running the summation from i =3tow rather than i =1tow, ifu i =1andu i =
2 are ignored. The corrected values for ¯x and ȳ as computed from the summations in Eq. 56 are then
used in Eqs. 55 or 58. If there are no readings at a particular u i , then the summations should just skip
this value of i.
The data for Kansas City were processed for i = 3 to 20 and for Dodge City for i = 3 to 28. These
upper limits include about 99.8 % of the data points and should therefore give adequate results. The
expression for y in Eqs. 55 becomes undefined for F (u) equal to unity so the last data point cannot
be included unless F (u) for this last point is arbitrarily set to something less than unity, say 0.998.
The results for Kansas City are c =7.65knotsandk = 1.776, and c = 11.96 knots and k = 2.110 for
Dodge City. The corresponding best fit lines are shown in Fig. 18. It is evident that these lines fit the
plotted points rather well.
Wind Energy Systems by Dr. Gary L. Johnson November 20, 2001