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Designing offshore wind farms requires a thorough understanding of metocean parameters in the area of the site. Site specific metocean studies are carried out to determine the parameters for each project.
COWI has substantial experience in carrying out metocean studies for offshore wind farms and in obtaining upfront certification of the established metocean design parameters (e.g. wind, water levels, waves, currents and sea ice) from accredited certifying agencies.
Using our in-house numerical modelling capabilities, we conduct state-of-the-art numerical modelling studies of waves and hydrodynamics (water levels and currents) to establish long-term time series of metocean conditions at various locations within the offshore wind farm site. Subsequently, advanced statistical analyses are performed to establish the relevant extreme conditions for design.
The metocean studies are normally conducted and reported in accordance with the international standard IEC-61400-3 (2013) "Design requirements for offshore wind turbines".
Meteorological and oceanographic dataThe main site specific meteorological and oceanographic data are gathered and analysed. Furthermore, the influence of sea level rise due to global warming is project specific and should be evaluated during the metocean study.
Wave conditionsWave conditions are determined by use of the spectral wind-wave modelling tool MIKE21 SW. The model predicts the resulting wave climate in coastal and offshore areas based on input of water depths, wind speeds and parameters describing the physics of the wave climate.
Water level variationsTo determine the water level variations MIKE21 Flexible Mesh Hydrodynamic is applied. Water level variations are influenced by tidal variations as well as wind driven storm surges.
Current conditionsCurrent flows are generated either by tidal water level variations or during storm conditions. MIKE21 Hydrodynamic is normally used to study the effect of storms on the water flow or to get a detailed picture of regular tidal currents in the project area.
Ice loading and wind-wave directional misalignment are included in metocean studies along with weather windows and downtime.
Extreme value analysisThe analysis of metocean data includes establishing design parameters based on extreme value analysis of the available data and/or numerical simulations. Such an analysis may also include joint probability.
Thomas GierlevsenProject Director, Marine & Foundation EngineeringTel: +45 5640 email@example.com
Offshore wind farms