Study On The Structural Design And Selection Of Floating Foundation Of Offshore Wind Turbine

During the past decade, the demand for clean renewable energy continues to risedrastically in China and other countries. Wind energy in the ocean can possibly be one ofthose future renewable clean energy sources as long it is economically feasible andtechnologically manageable. So far, most of the offshore wind farm research has been limitedto fixed platforms in shallow-water areas. In the water depth deeper than30m, however,floating-type wind farms tend to be more feasible.Offshore floating wind turbine system consists of floating foundation, wind turbine andmooring system. In the entire operational life cycle, the system withstands large wind loads inaddition to extreme wave loads. Therefore, it is necessary to design and choose a betterfloating foundation to ensure performance and reliability of wind turbine. Meanwhile, themooring system must be designed to have sufficient reliability to position the system becauseof nonlinear coupled effect between floating platform and mooring system. This thesis aimsto design efficient and reliable floating foundation and mooring system. Based on the3-Dpotential flow theory, this thesis does research and analysis about performance of floatingoffshore wind turbine and coupled effect of wind turbine, foundation and mooring system bymeans of numerical simulation.This thesis firstly descripes the research status of offshore floating wind turbine.According to the marine environment and design requirements, three kinds of floatingfoundation are proposed including SEMI, SPAR and TLP platform and correspondingmooring system. Taking TLP platform for example, the thesis presents the static analysis andobtains the restoring coefficients of floater. Building three coupled numerical models,uncoupled, hull/mooring coupled and wind turbine/hull/mooring coupled model, simulationsof offshore floating wind turbine in rated condition, cut-out condition and extreme conditionare presented. Dynamic function of mooring system and wind turbine on foundation areobtained. Through statistical analysis of historical results, comparisons of three kinds offloating foundation for offshore wind turbine are made. Considering the various factors in thegiven water depth, OWT-TLP platform is identified as the best of all.A steel structural design is created based on the geometry and loading of the TLP forextreme condition. The design is based on similar system analysis, American Bureau of shipping rules and American Petroleum Institute recommended pratices. The design isverified using Finite Element Analysis. The results of this work show that the design istechnically feasible from a structural integrity, performance and producibility standpoint.