Session: Construction & Industrialization

Paper Number: 165399

165399 - A Parametric Dimensional and Structural Iteration Study for the Floating Wind Turbine Support Structures 

Abstract: 

In recent years, various research and development (R&D) efforts have been conducted to realize large-scale commercial floating offshore wind farms. In Japan, a government-led project named “Green Innovation Fund Projects” has been launched and R&D has begun for cost reductions for offshore wind power generation. It is essential to reduce the cost of each facility for commercialization. When reducing the cost of substructures, it is important to design the lightest possible substructure that meets the required hydrostatic and hydrodynamic performance, considering the wind turbine and site-specific conditions. However, estimating the weight of a substructure in consideration of its structural strength requires a significant amount of time and effort. Especially in the conceptual design phase, it is a challenge to estimate the weight in a short span of time in order to improve the accuracy of the evaluation of the substructure concept and optimization of its shape.
In this study, a system to pursue lighter substructure by high-speed iterative calculations from the viewpoints of dimension and structural strength is constructed, and we tried reducing the weight of the substructure using the system.
This system, called Substructure Iteration System (SIS) in this study, can evaluate and compare the overall performance of multiple substructure specifications in terms of cost, stability and motion performance. SIS calculates substructure’s specification (hull steel weight, center of gravity and buoyancy, the height of metacenter, the amount and place of water ballast, etc.) and substructure’s performance (stability and motion performance) by inputting the shape and dimensions of the substructure. A parametric study is performed on the dimensions of each part of the substructure to find the dimensions that provide sufficient stability and reduce its hull steel weight.
A Morison-based numerical model composed of cylindrical beams is automatically generated for the substructure. Using this model, the system performs a time-domain integrated load analysis (ILA). In addition, calculation of the motion response amplitude operator (RAO), inclining tests, modal analyses and fatigue load simulations will be performed if necessary.
By referring to the maximum load applied to each beam from the ILA results, the required thickness of hull and weight per unit length of each beam composing the substructure are calculated. The dimensions of the substructure are optimized by iterating the system (re-entering these data to the system and conducting the parametric study and ILA again).
Next, we used the built system to actually reduce the weight of the substructure by iteration. The assumed wind turbine and the substructure were an IEA 15 MW wind turbine + Volturn US-S and we reproduced the substructure and the wind turbine on SIS. We also performed an ILA to confirm and compare the loads applied to each beam in the substructure. Afterwards, we tried optimizing the dimensions of the substructure and reducing its hull steel weight by iterative calculation. As a result, it was shown that the weight of the substructure could be reduced by two approaches: modification of the dimensions of the substructure and modification of the structural strength (or hull thickness) distribution.
This research is being conducted as part of the Green Innovation Fund Project’s R&D project.
 

Presenting Author: Shunsuke Nishimura Japan Marine United Corporation

Presenting Author Biography: Shunsuke Nishimura is a naval architect in Japan Marine United Co. He has been involved in substructure design for FOWT for five years, particularly optimizing the geometry and dimensions of it.

Authors:

Shunsuke Nishimura Japan Marine United Corporation
Haruki Yoshimoto Japan Marine United Corporation
Ken Kamizawa Japan Marine United Corporation
Ryo Matsuoka Nihon Ship Yard Corporation