An Internally Resonant Tunable Generator for Wave Energy Harvesting

Abstract

This work exploits a two-to-one internal resonance energy pump to design a wave energy absorber with improved bandwidth capabilities. The proposed absorber consists of two coupled (primary and auxiliary) oscillators. The primary oscillator is a partially submerged buoy whose stiffness results from the hydrostatic force. The auxiliary oscillator, which consists of a mass and a nonlinear spring, is mounted inside the buoy and has its frequency tuned to the dominant frequency in the sea wave spectrum and to half the natural frequency of the primary oscillator. When the buoy is subjected to the low-frequency wave excitation, the auxiliary oscillator resonates with the wave excitation and starts to move. Energy is then channeled to the primary oscillator through the two-to-one internal resonance energy pump. Experimental results performed using an electrodynamic shaker to simulate the sea waves demonstrate that the voltage output of the proposed absorber has a wider frequency bandwidth and is less sensitive to variations in the frequency of excitation.