Abstract
An initial design of the platform for the moderate water depth (100 m) is performed by upscaling of an existing 5 MW braceless semi-submersible platform design to support the DTU (Danish University of Science and Technology) 10 MW wind turbine. To investigate the dynamic characteristics of the ultra-large semi-submersible floating offshore wind turbine (FOWT), an aero-hydro-servo-elastic numerical modeling is applied to carry out the fully coupled time-domain simulation analysis. The motion responses of the ultra-large semi-submersible FOWT are presented and discussed for selected environmental conditions. Based on the quasi-static and dynamic analysis methods, the influence of the dynamic effects of the mooring lines on the platform motion responses and mooring line tension responses are discussed. Subsequently, the difference in the motion responses and structural dynamics of the DTU 10 MW and NREL (National Renewable Energy Laboratory) 5 MW FOWT is studied due to the difference in turbine properties. The simulation results reveal that the excitation of the low-frequency wind loads on the surge and pitch motions, the tower-base fore-aft bending moments and the mooring line tension response becomes more prominent when the size of the wind turbine increases, but the excitation action of the 3P effect on the structural dynamics of the 5 MW FOWT is more obvious than those of the 10 MW FOWT.
Highlights
Over the past few decades, offshore wind energy has emerged as an attractive alternative to conventional power generation and established itself as a major source of environmentally-friendly, inexhaustible, economical, and importantly renewable energy [1]
A floating structure can be used as an alternative from an economic perspective [4], such as spar-buoys [5], semi-submersible [6], barges [7], and tension leg platforms (TLP) [8], which have the advantages of reduced noise during installation, no required scour protection, and cheap anchor installation for the mooring system
The floating offshore wind turbine (FOWT) is a rigid and flexible hybrid multi-body system with the complex interaction of wind turbine-tower-support platform-mooring system, which makes the analysis of the dynamic characteristics of the FOWT system extremely complex and challenging [9]
Summary
Over the past few decades, offshore wind energy has emerged as an attractive alternative to conventional power generation and established itself as a major source of environmentally-friendly, inexhaustible, economical, and importantly renewable energy [1]. Owing to the ultra-large wind turbine requirements of larger support structures, Xue [18], Tian [19], and Islam [20] formulated a preliminary design of a floater to support the 10 MW wind turbine by upscaling the existing 5 MW OC3-Hywind, MIT-TLP, and WindFloat concepts This design satisfied the basic requirements of hydrostatic stability and dynamic properties of the 10 MW FOWTs. Xu et al [21] considered the DTU 10 MW wind turbine as the research object and used FAST to analyze the dynamic characteristics of the OC3-Hywind Spar-type FOWT under the joint action of the wind-wave-induced loads. The difference in the motion responses and structural dynamics of the NREL 5 MW and DTU 10 MW FOWTs is studied due to the complexity of the dynamic characteristics and coupling mechanism of the ultra-large FOWTs, which can provide a reference for the design and engineering practices of the ultra-large FOWTs
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
