Aerodynamically Induced Yaw Behaviour for Floating Wind Turbines
Master thesis
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https://hdl.handle.net/11250/3066255Utgivelsesdato
2022Metadata
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- Master's theses (RealTek) [1723]
Sammendrag
The demand for more renewable energy grows stronger by the day. The world is experiencing more pollution and environmental damages from human activity than everbefore. One of the possible solutions to produce more sustainable energy is offshorewind energy, more specifically floating wind energy. When transferring wind turbinesto the sea, far from shore, they will be less intrusive on society as well as the wind isstronger and more constant.This thesis dives deeper into the aerodynamically induced yaw motion of a wind turbinefloater. It also attempts to explain the underlying physics based on wind direction, windspeed and yaw stiffness provided by the mooring lines.To describe the fundamental mechanics, a static yaw system based on wind directionsand rotor plane-angle for a wind turbine floater is presented. To find the combinationof wind directions and -speed that causes large yaw rotations, numerical time-domainsimulations are conducted in SIMA. A model of the INO WINDMOOR 12 MW turbine,using a semi-submersible floater is used in the study. This floating wind turbine issubjected to constant wind intensity with varying wind speeds and wind directions.This numerical study consists of two approaches: one analysis with a rotating floater,where platform yaw has been the output parameter, and one analysis fixing the floaterand calculating the platform yaw moment based on internal forces. The internal forcesare generated by the thrustforce acting on the turbine. Platform rotation and platformyaw moment is then matched and compared by using a non-linear mooring stiffnesscurve.From the simulations it was observed a quite good correlation for the platform yawbetween the two analysis for wind speeds in the operational domain (0-25 m/s). Forwind speeds above 25 m/s, in the idling phase, a larger deviance was observed. Therotating floater experienced large rotations for some wind directions when subjected toan extreme case of 45 m/s. The fixed floater on the other hand, was unable to capture this self-reinforcing unstable yaw effect, which was observed for the rotating floater.