Structural optimisation of a semisubmersible floating platform for offshore wind turbines

Wind energy is currently a crucial player in the global transition toward sustainable and renewable energy sources. With the new geopolitical strategies, the focus on renewable energy intensifies, bringing out the role of wind energy and the investment in offshore wind turbine energy sector in order to secure a diversified and sustainable energy future. This thesis presents a structural optimisation of a semi-submersible floating platform for offshore wind turbines following the novel methodology introduced in the study "Definition of a reference model for structural finite element analysis of an offshore wind turbine floating foundation". Firstly, an overview of wind energy is presented, with a special focus on the evolution of offshore wind energy and the new trends due to the latest plans and agreements. The thesis continues by introducing offshore wind turbines, their components and typology. A background review regarding the important structural, aerodynamics and hydrodynamics is presented followed with the introduction of the reference system considered which is the UMaine VolturnUS-S and the IEA Wind 15-MW offshore reference wind turbine. The system is presented with the explanation of the novel methodology, system description, simulation and optimisation process, which defines an objective function to be iteratively minimized to optimise the surface groups thicknesses of the elements that compose the system to obtain a functional semi-submerges floating platform. After simulating and optimising a first case system, it was found that the optimised system is not functional because of the structural steel mass surpassing the allowable mass for the system floatation. This is due to critical weak points in the structure with high equivalent von Misses stress needing high thicknesses. An implementation of internal reinforcement elements is then studied for a second case study, obtaining a platform with radial stiffeners in the top and the bottom of the main column
Outgoing