Structural optimization of an offshore wind turbine floating foundation with Finite Element Analysis

Wind power has established itself as a viable renewable energy source, offering a sustainable alternative to fossil fuels and contributing significantly to the reduction of greenhouse gas emissions. Among the various implementations of wind energy, Offshore Wind Turbines (OWTs) have gained prominence due to their higher efficiency and ability to access more consistent wind resources compared to their onshore counterparts. Recent technological advancements have fueled a rapid global increase in the installation of Offshore Wind Farms, particularly Floating Offshore Wind Turbines (FOWTs), which can be deployed in deeper waters where traditional fixed-bottom structures are not feasible. However, the design and deployment of FOWTs present unique challenges, especially in the areas of structural integrity, cost-efficiency, and environmental impact. Engineers face significant technical and economic hurdles when developing reliable floating platforms that can endure harsh marine conditions while maintaining long-term viability. This thesis focuses on the analysis and structural optimization of the Tension Leg Platform (TLP) type of FOWT, which is known for its high stability due to the tensioned mooring system. The objective of this work is to perform a comprehensive structural optimization of the TLP platform using finite element methods (FEM). The analysis includes evaluating the hydrodynamic and aerodynamic loads, the effects of static and dynamic forces, and the interaction between the turbine and mooring system. OpenFAST software is employed to simulate the complex static and dynamic behavior of the wind turbine, including tower loads and the distribution of forces across the mooring lines. This thesis also considers the integration of hydrostatic pressure, turbine weight, static aerodynamic thrust, and mooring loads into the structural analysis to ensure a realistic and robust platform design. A key aspect of the study is the implementation of a single-objective optimization algorithm that aims to minimize the mass of the platform while adhering to constraints on mechanical stress and buckling instability. Special attention is paid to the placement and configuration of internal stiffeners within the platform to enhance structural performance. Additionally, while the primary focus remains on structural optimization, the thesis briefly addresses the design considerations of the anchoring system and conducts a preliminary cost analysis of the platform. The results of this study demonstrate that careful optimization of stiffener locations can significantly reduce the global mass of the platform while maintaining structural integrity under operational loads. Furthermore, insights into the relationship between platform geometry, load distribution, and overall material usage are provided, offering valuable guidance for future design improvements and cost reduction strategies in the development of FOWTs.