Passive self-aligning of a floating offshore wind turbine

The development of floating offshore wind turbines opens the way for various new design types, and the platform, tower and turbine can benefit from its floating foundation. Self-aligning platforms, where the entire structure follows the wind direction are a promising concept. A single point mooring with turret system allows for free rotation around the vertical axis. Aerodynamic forces of rotor and tower induce the self-aligning moment. In the present study, the operating principle of a passive platform design with airfoil-shaped tower and downwind rotor is analyzed under steady conditions using a boundary element method (BEM). Rotor cone angle and the tower dimensions have a major influence on the yawing moment. They must be large enough to dominate the hydrodynamic forces induced by seaway and current. The passive self-aligning capability is shown in an integrated simulation for various current velocities and wind-current offset angles.The authors kindly thank the Federal Ministry for Economic Affairs and Energy of Germany (BMWi) for financially supporting the HySToH project [03SX409A-F]. The authors also kindly thank our project partners CRUSE Offshore GmbH, aerodyn engineering gmbh, JÖRSS {BLUNCK { ORDEMANN GmbH, DNV GL and the Institute for Ship Structural Design and Analysis at the Hamburg University of Technology for the excellent cooperation