On the modelling of a floating offshore wind turbine

The location of wind turbines on floating structures offshore would allow an immense resource to be tapped without the drawbacks large developments can have on public opinion. There are, however, potentially significant technical and cost drawbacks. This article describes the theory and results of research work aimed at developing analytical tools for evaluating the performance of floating offshore wind farms. The principal problem addressed here is the development of analytical tools for modelling the turbine loads and fatigue damage due to the vessel motion. The effect that the motion would have on the wind turbine is found by calculating the aerodynamic and inertial loads on the blades in a two-dimensional state domain representing the blade and the vessel motion respectively. Using a double Fourier transform, discrete deterministic frequency spectra of the loads are found and the fatigue damage is evaluated. Undertaking the calculations for vessel motion in each degree of freedom allows appropriate weightings to be developed, which can be used for the optimization of candidate supporting vessels by evaluating the motion response directly. Copyright (C) 2003 John Wiley Sons, Ltd.