Blade Element Calculations - Small Wind Turbines: Analysis, Design, and Application - page 88

Fig. 5.2 a Predicted power
coefficient as a function of tip
speed ratio compared to the
measurements of Anderson
et al. [ 5 ]. b Predicted thrust
coefficient as a function of tip
speed ratio compared to the
measurements of Anderson
et al. [ 5 ]

0.5

(a)

0.4

BET with tip loss
BET without tip loss
measurements

0.3

0.2

4 6 8 10 12 14

Tip speed ratio,

1.1

(b)

1

0.9

0.8

0.7

B ET with tip loss
BET without tip loss
measurements

0.6

0.5

0.4

7 8 9 10 11 12 13 14

Tip speed ratio,

Judging from Fig. 5.2 a, the blade element predictions with tip losses predict the
power to within about 10% and are most accurate around the point of optimum
efficiency. The tip loss correction reduces the power, Fig. 5.2 a, but makes little
difference to the thrust, Fig. 5.2 b. This under-prediction may not be general: the
calculations by Shen et al. [ 1 ] for a different wind turbine over-estimated the