Environmental Engineering Reference
In-Depth Information
Fig. 2.8 Comparison of dynamic pressures taking into account the gust response according to DIN
1055-4 [12] and DIN 1056 [13]
The simplified calculation is on the safe side for the example shown in Figure 2.8.
2.3.2 Wind loads for offshore wind turbines
2.3.2.1 Classi
cation of wind turbines
The definition of a wind turbine class is practical for designing the machinery (rotor -
topsides structure) of an offshore wind turbine [11].
The values for the wind speed and turbulence intensity parameters should represent the
characteristics of numerous different locations, the aim being to determine clearly
defined levels of robustness (Table 2.8).
The design of the tower and foundation (support structure) for an offshore wind turbine
must be based on the representative environmental conditions - including the sea
conditions - at the respective location.
The design working life of an offshore wind turbine should be at least 20 years.
A rotor (turbine) designed according to one of the wind turbine classes given in
Table 2.8 can withstand environmental conditions in which the 10-min average of the
extreme wind speed for a 50-year return period is not greater than the given reference
wind speed (V
ref
) at hub height.
The average wind speed (V
ave
) is the statistical mean of the momentary wind speed
values averaged over a certain period - ranging from a few seconds to several years.
In [11] V
ave
is the annual average wind speed over many years. This value is used in the
Weibull or Rayleigh functions for the wind speed distributions.
