
281Renewable Electricity
the output of two sites decreases with the distance between them, but
increases with the time span considered. Thus, by using wind from multi-
ple geographically dispersed sites, a utility can easily reduce the short-term
uctuations in wind generation, but will nd it more difcult to smooth
out the daily wind generation. Figure 7.20 shows how the coefcient of
0
0.2
0.4
0.6
0.8
0 100 200 300400 50
0600
Distance (km)
Correlation coefficient
4 hour average
12 hour
1 hour average
30 minute average
5 minute average
2 hour average
FIGURE 7.19
Impact of geographic diversity on variability in wind generation. (From Ernst, B., et al.,
Shor ...