Numerical Simulation on Energy Delivery of Heaving Buoy Converter System

Heaving buoy system is proposed to be suitable for small amplitude and short period wave conditions. It is necessary to study the efficiency and energy delivery characteristic of the system as the heaving buoy might be one of the most promising and popular wave energy converters in China. Since the hydraulic system can collect and deliver the energy captured, the array deployment of the buoy is then feasible. Usually, heaving buoy system contains energy capturer, accumulator and electricity generator, which are linked by a hydraulic system. In general, each part of the system is independent, especially the energy accumulator, after which the energy delivery and conversion are not such related to the capturing step. For this reason, the conversion efficiency can be improved by optimizing this energy delivery system when the capturing part performs good enough. The paper simulates the energy delivery process systematically from the input of the energy accumulator to the output of the electricity generator by means of the Simulink in MATLAB. A logical linkage among the accumulator, the hydraulic motor and the generator is established, which determines the numerical relationship between any of the two in simulation. After some necessary cases of calculation, the rule of the energy delivery considering the input and output pressure, hydraulic motor rotation and generator resistance is revealed. It also optimizes the whole heaving buoy system by giving the rational number of accumulators and the releasing strategy of the hydraulic system. Good agreement between the experimental data and the numerical simulation results testify the reliability of the method. The numerical model established could be sued as a guidance of designing the hydraulic system of heaving buoy converter and maybe of other converters which make use of the similar hydraulic system. As the result, it is strongly advised to finely consider the preload and releasing pressure of the accumulator, the rotation speed of the motor, the torque and resistance of the generator, while composing and designing the hydraulic system of the heaving buoy converter.