Study On The Wave Energy Conversion Characteristics Of An Array Of Floating Point Absorbers

As a new type of renewable energy resource,wave energy has a large potential and a broad application prospect.A variety of wave energy converters have been developed and utilized to generate electricity and/or desalinate sea water.In these converters,a floating point absorber has been paid much attention as its small size,high efficiency,flexibile layout,and convenient application.In order to developand exploit the wave energy resources in the sea efficiently,it is necessary to assess the resources subtly and comprehensively,to study the operating characteristics of different floating point absorbers with the purpose of optimizing the floating point absorbers,and to evaluate the operational characteristics of the point absorber array with the aim of maximizing the wave energy conversion ratio within a specific sea area.Therefore,it is of grest significance tostudy on the wave energy conversion characteristics of the array of floating point absorbers for wave enegy development.Several research methods are applied,including numerical modelling and physical experiments,to investigate the assessment of wave energy resources,the wave energy converting characteristics of the floating point absorber and the operating characteristics of the array of floating point absorbers in this dissertation.As s preliminary step,the third generation of wave model is applied to perform a thorough assessment on the wave energy resources in the sea around the Zhaitang Island,Yellow Sea.Statistic data shows that the wave energy varies both in spatial and temporal distribution,while the average annual wave power is 1.054 kW/m and the wave power is higher during winter and spring.Meanwhile,the field measurements are utilized to validate the numerical wave model,and supply field test data.Different measurement technologies have been developed so far and the measuring buoys are one of the most popular ones,so physical model tests are conducted to investigate the measuring performance of 2 types of measuring buoys under regular and irregular waves.Furthermore,the fluid-structure-power take off numerical model is utilized to simulate the floating point absorbers,aiming to investigate how the geometry of the floater,draft and damping coefficient impact the hydrodynamic characteristics and the wave power absorption of the point absorbers.The optimization is also conducted on floaters in different shapes,and the simulation shows that the peak values of the capture width ratio of the floaters are independent of the bottom geometry of the floaters,while the cone-bottom floater shows wider capture frequency width.The optimized floater then is simulated under the coupled wave and current,in order to make a thorough study about the effect of the current on the hydrodynamic response of the floaters.The numerical simulation results show that the bigger the current velocity is,the smaller the heave motion and the capture width ratio of the floater are.The existence of current decreases the heave motion amplitude,the heave velocity and the capture width ratio of the floater in dependent of the current direction.Eventually,the frequency-domain and time-domain analysis with the assumption of linear potential theory are applied to simulate the array of wave energy point converters,under regular and irregular wave conditions respectively.The hydrodynamic response and the wave power capture width ration of the array are calculated and compared with those parameters of the single oscillating floater.For the wave power absorption,the array of the point converters show bigger captured wave power and higher efficient and use ratio on absorb the wave power distributed along in the wave propagating direction.