Date of Award

12-2013

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Civil Engineering

Advisor

Andrew J. Goupee

Second Committee Member

Habib Joseph Dagher

Third Committee Member

Roberto Lopez-Anido

Abstract

In this thesis a number of investigations are conducted into the use of a composite material wind turbine tower on an offshore floating platform. The use of a composite wind turbine tower is expected to substantially reduce mass and cost when compared to a steel design. Composite material towers are investigated on three different platforms, the OC3 Hywind Spar, the VolturnUS 1:8-scale semi-submersible and the 6 MW VolturnUS semi-submersible. Over the course of these investigations, a number of design and analysis tools are developed and linked to efficiently optimize and analyze a composite tower for use on a floating support structure. A methodology for obtaining a wind turbine tower with a minimum mass is developed utilizing a genetic algorithm optimization technique. Using the optimization tools, the use of a steel tower is investigated as well as the use of a sandwich panel versus a solid shell tower design. These tools are employed to compare composite towers to steel alternatives for both the OC3 Hywind system and the 6 MW VoltumUS system. In both cases it was found that the steel tower had significantly greater mass than a composite tower that meets all of the required design criteria. In addition to these numerical studies, a composite wind turbine tower was designed for the 20 kW VolturnUS 1:8 structure. An overview of the analysis, design and testing program that lead to the structure’s successful deployment is presented. The results of this thesis demonstrate the significant potential of utilizing composite materials for offshore floating wind turbine towers.

The thesis is organized in the following manner: Chapter 1 presents an introduction, and provides background and motivation for the subsequent research. In Chapter 2 a study on the use of a composite tower on the OC3 Hywind Spar and a literature review for composite FRP materials in an offshore environment is presented. In Chapter 3 an overview of the VolturnUS 1:8-scale composite tower analysis, design and testing program is presented. In Chapter 4 the tower optimization and analysis methodology is presented and a number of case studies using the optimization tool are analyzed. Finally, Chapter 5 presents conclusions of the work presented in the thesis and provides recommendations for future work.

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