Research on Key Technologies of Marine Wave Energy and Wind Energy Complementary Power Generation System

Author:Xie Dian

Supervisor:Gu Yujiong


Degree Year:2018





It’s valuable to develop wave energy and offshore wind energy,but some problems such as high investment and low stability will appear when single energy is utilized.A more reasonable solution is to exploit one specific energy with others assisting.Such a integrated energy system incorporating vertical-axis wind turbine and array buoy wave energy generator was introduced in detail in this paper.And key technical issues through the system were deeply discussed,which mainly included the performance of vertical-axis wind turbine,hydrodynamic performance of array buoy,transmission characteristics of hydraulic system,system control strategy and so on.The major research methods contained theoretical research,simulation and experiment.First of all,mathematical models of swing-arm buoy,vertical-axis wind turbine and hydraulic transmission system were developed.The force formulation,motion equation,shaft force equation,power output equation and efficiency equation of energy capture are derived from frequency domain and time domain according to potential flow theory.Two methods to solve aerodynamic performance of wind turbine were presented in this paper:one is numerical solution based on multiple stream-tube theory,the other is CFD emulation method.And the mathematical models involved in the two methods were analyzed.Response characteristics of crucial components as hydraulic cylinder,hydraulic pump,hydraulic motor,energy storage etc.were studied.Then,mathematical description of hydraulic drive chain individually comprised in the wind turbine,wave generator and coupled wind-wave hybrid system was given.Next,the research on hydrodynamic performance of wave trapping device was studied,which contained:the analysis of marine experiments conducted by array buoy wave erergy generator which adopts cylinder buoy based on the Marine Renewable Energy Special Fund Project;further optimization was carried out on the basis of the cylindrical buoy.The shape of the buoy,the initial draft depth,the wave incident angle,and the influence of the PTO on the buoy’s motion response and the capture width ratio are discussed;the influence of the spacing and arrangement of the array buoys on the motion response of each buoy was studied and compared with the single buoy motion,which provided the basis for the optimal layout of the array buoys.Then,the aerodynamic performance optimization of vertical axis wind turbines was studied,and its start-up performance and wind energy utilization characteristics are analyzed based on the marine experiments data of an H-type wind turbine.A kind of helical wind turbine which is formed by bending the blades of H-shaped wind rotor was proposed based on former research.The aerodynamic characteristics of helical wind turbine was researched by MATLAB programming based on flow tube model.Afterwards,through the CFD numerical simulation with higher computational accuracy,the influence of the number of blades,chord length and ratio of height to diameter on the variation of wind energy utilization coefficient and torque coefficient of helical wind turbine was studied.In addition,the optimized wind rotor was compared with the H-type wind rotor with same swept area,and the optimized wind rotor ’s stress situation was more uniform,which can avoid the dead spots in the static start-up process and prolong the life of the wind turbine.At last,in view of the shortages of the wind power generation subsystem and the wave energy generation subsystem operating respectively and power superposition performed in the back power system,which exists in troditional wind-wave hybrid system.And then a system energy integration scheme of wind and wave energy coupling,hydraulic motor and generator miniaturization and modular configuration was proposed.Different operation strategies are adopted according to different working conditions:1)Hydraulic oil of branches is gathered all the way when wind and wave energy is small,driving the same one hydraulic motor and then driving generator,which contributes to increase of single generation power,efficiency and stability;2)When wind and wave energy deviates a little from nominal condition,individual independent power generation,absorbing the short pressure fluctuation with hydraulic accumulator and the speed regulating circuit are applied to carry on power tracing operation mode.3)When the wind and wave energy power is higher than the nominal working condition,reserved hydraulic motor and generator are started to fully convert the wave and wind energy from the energy capture device to the electric power,avoiding hydraulic overflow and some degree of abandoned wind wave phenomenon.In this paper,the basic information of the prototype of the array buoy wave energy generator and the H-type vertical axis wind turbine was fully listed in appendix Ⅰ.Based on the research of this paper,the design and construction of some experimental prototypes have been completed,which were written in appendix Ⅱ.