WindFloat FC: A Four-Column Floating Wind Turbine Foundation - Part I - Global Sizing and Global Performance Analysis

Abstract As the floating wind industry transitions from pre-commercial to utility-scale projects, wind turbine generator (WTG) ratings of 15 MW and beyond are increasingly being considered. With this growth, some WTG original equipment manufacturers (OEMs) are expressing a preference for platforms operating in the stiff-stiff eigenfrequency (EF) regime, where the first coupled tower-platform frequency is above the nominal 3P frequency of the WTG. Central column platform designs, such as the WindFloat® FC, are emerging as optimal solutions to achieve this new requirement. WindFloat FC was introduced in 2024 by Principle Power to address the growing demands of upcoming utility-scale floating offshore wind projects. In addition to its technical advancements, the WindFloat FC emphasizes standardization and industrialization to streamline fabrication, reduce costs, and accelerate deployment at scale. This paper presents a methodology to rapidly estimate the first tower dominated eigenfrequency of a coupled wind turbine and platform system. This process is efficient and accurate enough to use inside parametric global sizing studies early in the design process. This provides the ability to consider the coupled tower eigenfrequency as a performance metric to set the principal dimensions of a floating foundation. Validation of this rapid eigenfrequency estimation methodology is provided by comparing results to modal analysis results from an ANSYS shell model. A case study presents results of a parametric sizing survey performed on the WindFloat FC platform. A brief summary of the stability and global performance analysis performed on this design is presented. This work is complemented by another paper in these proceedings, which delves into the Structural Design and Analysis of the WindFloat FC platform.