A wave energy harvester based on coaxial mechanical motion rectifier and variable inertia flywheel

The wave energy harvester has been employed to power marine devices. For the wave energy harvester based on mechanical motion rectifier, the output power and efficiency are limited due to low inertia-damping ratio and perpendicular motion transformation. A coaxial mechanical motion rectifier with the function of increasing transmission ratio is designed based on a planetary gear train and four one-way clutches, and the input and output shafts are arranged coaxially. A variable inertia flywheel is incorporated in the wave energy harvester to extend the overrunning phase by slowing down the velocity attenuation of the generator. The wheel in variable inertia flywheel is reduced to four cantilever sliders to decrease the starting torque. The dynamics model of the wave energy harvester considering the meshing and overrunning phases is investigated due to the introduction of variable inertia flywheel. The input force and output voltage are simulated with sinusoidal displacement input after obtaining the angular velocity of generator with variable inertia flywheel. A maximum efficiency of 51.54% and average output power of 1.17 W on Instron machine are achieved, while a maximum output power of 3.35 W in ocean tests is obtained. The experiments verify that the design of coaxial mechanical motion rectifier and variable inertia flywheel is beneficial to improving the output power and efficiency.