Stochasticity of natural processes concerning loads exerted on offshore wind turbines

Sofia Vrettou; Theano Iliopoulou, and Demetris Koutsoyiannis

The tendency to avoid non-renewable sources in electricity production has led –among other alternative models of energy production- to the rapid growth of offshore wind farms. With regard to the structural design of the offshore wind turbines, international standards for the design of the turbines, suggest that the forces executed on the turbine’s pile, primarily induced by wind and waves, should be calculated by using dynamic models and short-term simulations of the natural parameters. However, due to the stochastic nature of wind and wave generated forces, such dynamic procedures and the short-term approach fail to accurately calculate or either - in the desired scenario - predict the exerted loads. On the other hand, stochastic methods do take into account characteristics of natural processes such as long-term persistence that are crucial in designing the turbines. In this work we aim to estimate the uncertainty in exerted forces using Hurst-Kolmogorov stochastic models and compare the results with those calculated using deterministic methods. A key objective is to examine how the fatigue of the structures is affected by the stochasticity of natural processes.