Mechanical Motion Rectifier Based Efficient Power Takeoff for Ocean Wave Energy Harvesting

This paper proposes a novel mechanical-motion-rectifier (MMR) based power-takeoff (PTO) for ocean wave energy harvesting. The proposed PTO directly converts irregular oscillatory wave motion into regular unidirectional rotation of the generator. It is mainly composed of two ball screws, three bevel gears, two one-way clutches, and a generator. The two one-way clutches and the bevel gears change the bi-directional rotation of the two ball screws into unidirectional ration of the generator. The MMR rectifies the irregular reciprocating motion into unidirectional rotation; similar to the way the electric voltage rectifier regulates an AC voltage. The proposed PTO can be integrated into a heaving point wave energy converter (WEC). The dynamics and modelling of the PTO are presented. The frequency-domain dynamics of the WEC are then formulated for operating condition and control. The power generation capability of the proposed WEC has been evaluated in MATLAB and WAMIT. The simulation results demonstrate that the power generation capability can be improved by using the MMR method.