Environmental Engineering Reference
In-Depth Information
2. The temperature gradient in the shaft wall due to differing climatic conditions is
D
T
¼
15 K
From this we get a thermal expansion gradient:
10
5
e
T
¼a
T
D
T
=
2
¼
15
:
=
2
¼
0
:
075
%
In the absence of specific data, the following standard environmental conditions should
be assumed for offshore wind turbines (see [11] 4.2.4.1):
- Wind turbines are to be designed for ambient temperatures between
20 and
þ
50
C. The following uniform temperature change is to be assumed:
D
T
N
¼
35 K
in relation to a mean temperature of
þ
15
C.
- It must be possible to operate the wind turbine at ambient temperatures between
10
and
þ
40
C.
- Relative humidity of max. 100%
- Unpolluted marine atmosphere
- Intensity of solar irradiation: 1000W/m
2
- Density of air: 1.225 kg/m
3
- Density of water: 1025 kg/m
3
- Salt content of seawater: 3.5%
The lowest seawater temperature may be assumed to be 0
C.
Other assumptions will be necessary for locations with extreme changes of temperature
(see [11] 4.2.4.2) or ice conditions.
2.8 Sea ice
Erecting wind turbines in areas affected by ice formation or drifting ice requires the
effects of these ice conditions to be taken into account by means of the following
properties and statistical data (Table 2.14) [24,26,28]:
Table 2.14 Properties of sea ice [24]
900 kg/m
3
Density
8.84 kN/m
3
Unit weight
2 GPa
a)
Modulus of elasticity
Poisson's ratio
0.33
Friction coefficient - ice-ice
0.1
Dynamic friction coefficient - ice-concrete
0.2
Dynamic friction coefficient - ice-steel
0.1
a)
Figure given in [28]: E
ice
¼
9.5 to 12.0 GPa
