On the development of a semi-submersible offshore floating platform and mooring system for a 13.2 mw wind turbine

Liu, Jinsong, Ph. D.
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Over the past decades, wind energy has emerged as an alternative to conventional power generation that is economical, environmentally friendly, and importantly renewable. Specifically, offshore wind energy is being con- sidered by a number of countries to harness the stronger and more consistent wind resource compared to that over land. To meet the projected “20% energy from wind by 2030” scenario that was announced in 2006, 54 GW of added wind energy capacity needs to come from offshore according to a National Renewable Energy Laboratory (NREL) study. In this study, we discuss the development of a semi-submersible floating offshore platform with a catenary mooring system to support a very large vi 13.2 MW wind turbine with 100 m blades. An iterative design process is applied to baseline models with Froude scaling in order to achieve preliminary static stability. Structural dynamic analyses are performed to investigate the performance of the new model using a finite element method approach for the tower and a boundary integral equation (panel) method for the platform. The steady-state response of the system under uniform wind and regular waves is first studied to evaluate the performance of the integrated system. Response amplitude operators (RAOs) are computed in the time domain using white- noise wave excitation; this serves to highlight nonlinear as well as dynamic characteristics of the system. Finally, the stochastic dynamic response of the system is studied to assess the global performance for sea states defined by wind fields with turbulence and long-crested irregular waves.