Integrated System Design for a Large Wind Turbine Supported on a Moored Semi-Submersible Platform

Jinsong Liu,Edwin Thomas,Lance Manuel,D Griffith,Matthew Barone,Kelley Ruehl

doi:10.3390/jmse6010009

Abstract

Over the past few 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 considered 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 need 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 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, selected design load cases (DLCs) and the stochastic dynamic response of the system are studied to assess the global performance for sea states defined by wind fields with turbulence and long-crested irregular waves.

Highlights

Over the last few decades, wind has emerged as an attractive alternative to conventional power generation and established itself as a major source of environmentally-friendly and inexhaustible renewable energy
The objective of this study is to develop an integrated system model consisting of a tower, semi-submersible platform and mooring system that can support the Sandia National Laboratories (SNL) 13.2-MW wind turbine, while meeting static and dynamic performance requirements and limiting overall system costs
As demonstrated in the OC4 study [17], the KC number is less than two for the large components of the OC4 DeepCwind semi-submersible platform for almost all sea states except for extreme wave conditions. For these same sea states, we find that potential flow theory is more widely applicable for the 1.5-scaled SNL platform model than was the case for the OC4 DeepCwind platform

Summary

Introduction

Over the last few decades, wind has emerged as an attractive alternative to conventional power generation and established itself as a major source of environmentally-friendly and inexhaustible renewable energy. 54,642 MW of new wind power generation capacity were added in 2016, according to global wind market statistics by the Global Wind Energy Council (GWEC) [1]. A National Renewable Energy Laboratory (NREL) cost study found that, to achieve the 20% target, 54 GW of added power generation capacity would need to come from offshore wind [3]. In deeper waters such as is the case for many U.S offshore wind sites, floating platforms are more feasible and economical as support structures [4]. Three principal floating platform configurations, as shown, classified in terms of how these support structures achieve stability, have been considered They are: 1. Shallow-draft platforms, such as barges with catenary mooring lines, that achieve stability via the extent of their water-plane area

Objectives

Methods

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Conclusion