Session: 06-01-01 Computational Mechanics and Design Applications

Submission Number: 180984

Hydrodynamic Stability of a Two-Body Platform for a 22 MW Wind Turbine 

To reduce the levelized cost of offshore wind development, the International Energy Agency (IEA) has recently introduced a 22 MW reference wind turbine mounted on a baseline semi-submersible platform similar to the VolturnUS-S design, situated in deep sea to harness abundant wind energy. However, the harsh conditions of the deep sea are prone to threaten the towing stability and operational reliability of floating wind turbines. To address this issue, this study first designs a novel two-body floating platform named NewSemi, consisting of an upper float, a lower ballast, and a suspension system with multiple tension tendons. By adjusting the ballast weight and the length of the suspension tendons, the NewSemi platform can significantly change its overall draft and center of gravity, enabling wet towing without water depth constraints while enhancing self-righting capability at the operational site. Subsequently, a numerical model of the NewSemi floating wind turbine, affected by combined wind, wave, and current loads, is established. Utilizing the open-source software OpenFAST in conjunction with WAMIT, a fully coupled aero-hydro-servo-elastic-mooring time-domain analysis is conducted under sea states corresponding to one-year and fifty-year return periods. The impacts of the upper float shape and lower ballast mass on the hydrodynamic characteristics are discussed, followed by the optimization of the number and layout of the tension tendons using intelligent algorithms. Finally, the performance of the optimized NewSemi platform is compared to that of the original semi-submersible platform in terms of static stability, natural period, dynamic stability, tower base bending moment, maximum tension in the mooring chain, and economic viability. The results demonstrate that the NewSemi platform meets international standards for hydrodynamic response under both normal and extreme conditions, outperforming the original semi-submersible platform. This study provides valuable insights into the hydrodynamic characteristics of two-body floating platforms and presents an alternative design option for large wind turbine deployments.

Presenting Author: Huaxiao Wu Tsinghua Shenzhen International Graduate School

Presenting Author Biography: PhD student at Tsinghua University, studying floating structure design and optimization.

Authors:

Huaxiao Wu Tsinghua Shenzhen International Graduate School
Sunwei Li Tsinghua Shenzhen International Graduate School
Bin Peng Tsinghua Shenzhen International Graduate School