Session: 09-01-09 Wind Energy: Moorings 1

Paper Number: 122874

122874 - Optimal Mooring Pattern for a Semi-Submersible Fowt in a Typhoon Environment 

The scarcity of suitable shallow waters for fixed-bottom offshore wind turbines has prompted developers to explore deeper waters, albeit with caution due to the significant capital expenditure (CAPEX) associated with Floating Offshore Wind Turbines (FOWTs). A major cost component in FOWTs is the mooring system, a concern exacerbated in regions with the presence of typhoons, necessitating a more robust and therefore expensive 3x3 mooring solution compared to 3x1 in areas such as the North Sea. This study tried to propose a 3x2 mooring arrangement tailored for FOWTs in the typhoon region, offering a potential cost reduction of up to one-third compared to the original 3x3 configuration.

To achieve cost savings, an in-depth analysis of spreading angles from 10° to the widest angle of 126° is performed using the pretension-diameter vs offset-tension 3D response surfaces technique. The research reveals that, theoretically, a 60° mooring angle minimizes floater offset with the least tension. However, the discrepancy in safety factors between intact and damaged conditions makes grouped mooring a more cost-effective choice. Utilizing the American Bureau of Shipping (ABS) safety factor, a 10° spread angle mooring system's chain cost emerges as roughly one-fifth cheaper than alternative configurations.

Additionally, the study explores an innovative V-Share mooring [1], wherein a single pile anchor connects to two different columns via two mooring lines. In conclusion, a 3x2 mooring pattern for a 15MW semi-submersible FOWT in typhoon regions might be theoretically achieved on paper. However, it may not be practically achieved, if the size limit of the manufactured chain is taken into account.

Presenting Author: Glib Ivanov National Taiwan University

Presenting Author Biography: Glib IVANOV (雲在天) jumped from Shipbuilding to Floating Wind as he moved from Ukraine to Taiwan. As a Ph.D. student at National Taiwan University, responsible for the TaidaFloat Platform structural design and optimization. His main goal is a green and safe marine environment, so apart from FOWT he conceptualized Ukraine's first fully electric cargo ship.

Authors:

Glib Ivanov National Taiwan University
Yongyan Wu Aker Solutions
Donghui Chen Genesis Engineering
Zhao-Yu Lai National Taiwan University
Jui-Chen Chen National Taiwan University
Nikolai Gladkov Google
Kai-Tung Ma National Taiwan University