Investigation on Resonance Response of Mass-Adjustable Float in Wave Energy Conversion System

In the floating wave power system, when the natural frequency of the float coincides with the wave frequency, the system would theoretically work in the resonance state, which consequently makes the capture efficiency of wave energy conversion device reach the maximum. The natural frequency of the float is related to many parameters, including the float size and shape, float stiffness, float mass, float additional mass, etc. The variation of float mass might cause other parameters, like draught, additional mass and hydrodynamic coefficients, to change. This is one of the important reason why there is still no efficient and accurate method for mass adjustment. In order to solve this problem, a mass-adjustable float is designed, and a new optimization calculation method for the float based on the high-order polynomial fitting theory is proposed. The optimized method combines the advantages of boundary element analysis and numerical calculation. It introduces an additional coefficient K related to the wave frequency and the draught of the float to optimize the Hooft's approximate equation between the additional mass and the float size. This optimized method can greatly improve the computational efficiency without reducing calculation accuracy. Finally, the heaving response of the mass-adjustable floats at different wave frequencies are calculated in AQWA, which verifies that the mass-adjustable floats have higher wave capture efficiency than ordinary floats. (C) 2019 The Authors. Published by Elsevier Ltd.