Design, Numerical Modelling and Analysis of a Semi-submersible Floater Supporting the DTU 10MW Wind Turbine.

In recent years, the demand for renewable energy has increased significantly because of its lower environmental impact than conventional energy technologies. Wind power is one of the most important sources of renewable energy produced nowadays. As land based turbines have reached their maximum potential, recent market trends are moving into deeper waters with higher capacity turbines. The design of a floating offshore wind turbine (FOWT) foundation poses few technical challenges. Floating stability, favourable motion characteristics and introduction of cost effective solutions to name a few. Moreover, as deep water offshore designs are still at an early stage of development, numerical modelling of the coupled dynamic behaviour also remains one of the key issues. This work presents the design of a semi-submersible floater that can support the generic, publicly available DTU 10MW RWT. The design is developed from NREL 5MW WindFloat and verified with detail stability analysis in GHS, rigid body motions and wave frequency loads are calculated using Wadam. The interaction between wind loads on the pitch controlled rotor and motions of the floating structure are captured by coupled aero-hydro-servo-elastic simulations in Simo- Riflex-AeroDyn (SRA). Platform and turbine responses are compared against a Spar and TLP supporting the same wind turbine for identical environmental conditions. Based on simulation results, it is found that the semi-submersible platform has satisfactory responses in different operational and in extreme wind condition. The design is proved to have the lowest displacement (and draft) compare to the Spar and TLP which will allow the semi-submersible platform to employ equally in intermediate and deep water offshore