Page 200 - Wind Energy Handbook

174 WIND-TURBINE PERFORMANCE

0.5

0.4

0.3

C P 0.2

0.1

0
0 5 10 15
λ
Figure 4.1 C P – º Performance Curve for a Modern Three-blade Turbine

0.6
Tip losses

Drag losses
0.4 All losses included
No drag or stall losses
No losses at all
C
P Stall
losses
0.2

0
0 2 4 6 8 10 12 14 16
λ
Figure 4.2 C P – º Performance Curve for a Modern Three-blade Turbine Showing Losses

4.1.2 The effect of solidity on performance

At this stage, the other principal parameter to consider is the solidity, defined as
total blade area divided by the swept area. For the three-blade machine above the
solidity is 0.0345 but this can be altered readily by changing its number of blades.
The solidity could also have been changed by changing the blade chord.
The main effects to observe of changing solidity are as follows, see Figure 4.3.