Environmental Engineering Reference
In-Depth Information
Table 2.8 Wind conditions for offshore wind turbines to [11] Table 4.2.1
Wind
turbine
class
I
II
III
S
Remarks
V
ref
[m/s]
50
42.5
37.5
site-specific
50-year return wind
10-min average
V
ave
[m/s]
10
8.5
7.5
Annual average wind speed
Category
A
B
C
S
Remarks
Turbulence
intensity
higher moderate
lower
site-specific
I
15,A
[
]
0.18
0.16
0.145
characteristic turbulence
intensity for V
hub
¼
15m/s
a[
]
2
3
3
slope parameter for
turbulence characteristics
2.3.2.2 Determining the wind conditions (wind climate)
The following basic parameters for the wind actions must be determined for the draft
design and the location [11] 4.2.2.2:
- Reference wind speed V
ref
- Annual average wind speed V
ave
- Wind speed distribution
- Wind direction distribution (wind rose)
- Turbulence intensity I
15
for V
hub
¼
15m/s (V
hub
is the 10-min average of wind speed
at hub height)
- Wind shear.
The averaging time used in [11] for the reference wind speed (V
ref
) is 10minutes (see
Table 2.8). The wind conditions (wind climate) may be determined frommeasurements
taken at the location provided the measurement period is at least six months. The
effects of seasonal fluctuations must be taken into account where these have a
substantial effect on the wind climate.
Here, I
15
is the characteristic value of the turbulence intensity (I
15(k)
). It is calculated by
adding the measured standard deviation to the measured mean value (I
15(m)
)ofthe
turbulence intensity. If the standard deviation has not been calculated from measurements,
then the characteristic turbulence intensity for V
hub
¼
15m/s may be calculated as follows:
I
15
ð
k
Þ
1
:
2
I
15
ð
m
Þ
The value I
15(k)
should be determined frommeasured data when wind speeds exceed 10m/s.
In agreement with GL Wind (Germanischer Lloyd WindEnergie GmbH), the relevant
