Design Optimization and Coupled Dynamics Analysis of an Offshore Wind Turbine with a Single Swivel Connected Tether

Jieyan Chen,Chengxi Li

doi:10.3390/en13143526

Abstract

The increased interest in renewable wind energy has stimulated many offshore wind turbine concepts. This paper presents a design optimization and a coupled dynamics analysis of a platform with a single tether anchored to the seabed supported for a 5 MW baseline wind turbine. The design is based on a concept named SWAY. We conduct a parametric optimization process that accounts for important design considerations in the static and dynamic view, such as the stability, natural frequency, performance requirements, and cost feasibility. Through these optimization processes, we obtain and present the optimized model. We then establish the fully coupled aero-hydro-servo-elastic model by the time-domain simulation tool FAST (Fatigue, Aerodynamics, Structures, and Turbulence) with the hydrodynamic coefficients from an indoor program HydroGen. We conduct extensive time-domain simulations with various wind and wave conditions to explore the effects of wind speed and wave significant height on the dynamic performance of the optimized SWAY model in various water depths. The swivel connection between the platform and tether is the most special design for the SWAY model. Thus, we compare the performance of models with different tether connection designs, based on the platform motions, nacelle velocity, nacelle accelerations, resonant behaviors, and the damping of the coupled systems. The results of these comparisons demonstrate the advantage of the optimized SWAY model with the swivel connection. From these analyses, we prove that the optimized SWAY model is a good candidate for deep water deployment.

Highlights

Nonrenewable energy resources, such as coal, natural gas, and oil, are primary sources of energy.these fossil fuels continue to be depleted, and are harmful to the environment
The wind conditions and the corresponding thrust and moment used for optimization is based on the rated wind conditions and the corresponding thrust and moment used for optimization is based on the rated conditions for the National Renewable Energy Laboratory (NREL) 5 MW wind turbine [16]
Since the SWAY system is a floating offshore wind turbines (FOWT) for deepwater offshore locations in 100–400 m water depths, we model and examine two more cases with 100 m and 300 m water depths, to explore the platform response, as well as the wind turbine performance in different water depths

Summary

Introduction

Nonrenewable energy resources, such as coal, natural gas, and oil, are primary sources of energy. These fossil fuels continue to be depleted, and are harmful to the environment. Among the different kinds of wind turbines, oceanic floating offshore wind turbines (FOWT) are an excellent solution to avoid interference with life on the land and achieve higher energy efficiency due to the steadier and higher annual mean offshore wind velocity. Different types of upper wind turbine models have been proposed and used in many studies, such as the National Renewable Energy Laboratory (NREL) 10-MW wind turbine [4,5,6] and NREL 5-MW wind turbine [7,8,9,10]. Combining the Energies 2020, 13, 3526; doi:10.3390/en13143526 www.mdpi.com/journal/energies

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Conclusion