Coupled Wind And Wave Anslysis Of A New Combined Floating Wind Turbine And Wave Energy Converter System

As the important physical foundation of human existence,energy plays an integral role in the historical development process of the human society.With the aggravation of the energy crisis,increasingly prominent of the environment issue,the wave of the worldwide development of renewable energy has been popularized.Wind and wave power cause more and more concerns increasingly.Due to natural correlation,ocean wave energy may also be considerable where the offshore wind energy resource is rich.This paper deals with a novel concept by combining a tension leg platform-type floating wind turbine and a heave-type wave energy converter that is referred as the ‘TWWC'(TLP-WT-WEC-Combination)system herein.The wind turbine generates energy from wind while the WEC slides along the TLP to transform into wave energy by the relative heave motions through a power take off(PTO)system from waves.The wind turbine and the WEC not only sharing the same supporting structure system and cables in the view of cost reduction,but also utilizing the area of the ocean more efficiently.the practical applications of this new integrated structural system will solve the electricity problem of islands and large man-made islands in the South China Sea effectively,providing technical support for realizing the construction of marine powerful nation.The conceptual design and preliminary optimization have been completed firstly,which is premised on obtaining the maximum transient wave power.Taking into account the effects of different diameters,different shapes,different PTO parameters and wave periods on the performance of the WEC's wave energy production under typical wave cases have been investigated,the hydrodynamic panel model of the TWWC system has been established based on the potential fluid theory using AQWA code.Then the aerodynamic loads of the wind turbine are simplified based on the design data of NREL 5MW wind turbine(the thrust-wind speed fitting function)while taking account into the influence of relative incident wind speed caused by the real-time motion of the TLP,so that the wind-wave loads coupled numerical model of TWWC system to be built in the time domain optimally.This section focus on the dynamic responses and wind-wave output power of the TWWC system under typical operational coupled wind and wave sea cases and the responses of the floating wind turbine(FWT)alone with those of the FWT in the TWWC have been compared.Choosing the critical design property index as the main research objects,including the displacements of the TWWC system in surge,heave and pitch,tether force,nacelle's acceleration,relative heave velocity,relative heave displacement and contact force between the WEC and tower.which will provide scientific references for the structure design.Considering the extreme ocean environment condition in the South China Sea finally,the safety performance of the TWWC system were proposed to be investigated in extreme conditions.PTO damping force and tether force will be taken into account emphatically.The investigation is conducted by comparing different survival strategies acting on the TWWC system result in the extreme values of responses Consummating and checking the safety performance of the TWWC system in extreme conditions and an exploratory optimized survival solution has been proposed to withstand the load effects imposed by extreme environmental conditions.