Environmental Engineering Reference
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Table 6-4. Wake Deficit Parameters Derived from HAWT Field Test Profiles
[data from Faxen 1978]
Parameter
Test No. 1
Test No. 2
Turbine:
Free-stream wind speed (m/s)
6.9
8.2
Power output (kW)
16
35
Power density
1
(W/m
2
)
60
132
Wake:
Wake-to-rotor area ratio
» 4.0
» 4.0
Centerline velocity deficit (m/s)
0.84
2.09
Average velocity deficit (m/s)
0.23
0.58
Normalized Wake:
Deficit-to-free stream wind speed
ratios
Centerline
0.122
0.255
Average
0.034
0.071
Average-to-centerline deficit ratio
0.28
0.28
Deficit-to-power density ratios
Centerline (m/s)/(W/m
2
)
0.0139
0.0155
Average (m/s)/(W/m
2
)
0.0039
0.0044
1
Rotor swept area = 270 m
3
Figure 6-20. Schematic plan view of the Mod-2 HAWT test site near Goldendale, Wash-
ington, during wake effect tests using an energy method.
Unit 2 is operated intermittently
to change the energy output of Unit 1. Energy output of Unit 3 is used as a control, to elimi-
nate wind variability effects. [Neustadter and Spera 1984]
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