Techno-economic analysis and early-stage structural optimization of floating platforms for offshore wind turbines

Wind energy has the potential to be one of the main drivers in the renewable energy era, however, it still needs to overcome certain challenges for an efficient implementation. Deep water (> 60 m) offshore wind concentrates the major share of wind resource, which is why it is imperative to develop improved technologies for its optimal exploitation. One of the main challenges regarding the implementation of floating offshore wind turbines is the Capex required, where one of the most significant costs is the floating structure that gives buoyancy and stability to the wind turbine. This thesis presents an early stage optimization method for the design of floating structures, however, it is important to conduct additional reliable simulations to validate these results and ensure their effectiveness. The main features that must be taken into account when optimizing a floating structure are mentioned and analysed while iterating diverse geometric configurations. The reference system considered is the "UMaine VolturnUS-S" and the "IEA Wind 15-megawatt offshore reference wind turbine". A static analysis was performed utilizing FEA in ANSYS to assess the loads experienced by the structure under the conditions of the double mean pitch angle. This analysis focused specifically on evaluating the structure’s response to the highest static load it would encounter, which corresponds to the rated wind speed. The study provides valuable insights into the structural behaviour, load-bearing capacity, and stress distribution of the proposed structures. By evaluating the equivalent stresses and total deformation, a comprehensive understanding of their mechanical response is obtained. The geometric iterative code, when optimized for cost, demonstrated a significant reduction of 22.5% in comparison to the original structure. Similarly, when optimized for pitch, the code achieves a 30.5% reduction while ensuring that the structure’s performance remained within acceptable stress limits. The structural improvements were achieved by adjusting the geometric dimensions, internal structure, and thickness distribution.