Static and Fatigue Analysis of Wind Turbine Towers Made in Composite Materials

In the context of the increase of the energy demand, the offshore wind industry is developing larger floating platform to produce more electricity and to minimize the levelized cost of energy (LCOE). The target is to install 20MW power turbine and more at sea, but the size of the platform, of the tower and of the turbine will significantly increase. The change of scale will lead to huge dimensions and heavy weight that will contribute to an increase of the cost for the installation and for the mooring. A solution to reduce the weight of the structure of Floating Offshore Wind Turbine (FOWT) has been investigated within the European Research project FIBREGY and consists in replacing steel by composite materials. The overall objective of the FIBREGY project is to enable the extensive use of Fibre Reinforced Plastic (FRP) materials in the structure of the next generation of large Offshore Wind and Tidal Power (OWTP) platforms. This paper aims to present the results obtained for FOWT towers made in carbon fibres. Firstly, the calculation methodology developed during the FIBREGY project to evaluate loads applied to a FOWT will be detailed. This methodology is based on Bureau Veritas software programs and particularly on OPERA, a hydro-aero-mooring coupled dynamic calculation tool. Then, numerical simulations performed with ultimate loads in static and cyclic loads for the fatigue analysis will be detailed. Stresses will be compared with criteria determined within the project for such application as well as the fatigue life. Finally, the design of tower will be optimised in considering the damage in fatigue, the static stresses, the maximal deflections and the buckling.