An electromagnetic-piezoelectric high-efficiency hybrid wave energy harvester with direction self-adaptive characteristics based on an asymmetric rotating pendulum

Wave energy is limited in its widespread application due to its ultra-low frequency and directional randomness. Meanwhile, most existing hybrid wave energy harvesting technologies are merely simple integrations of multiple energy capture units. Therefore, this paper proposes an electromagnetic-piezoelectric high-efficiency hybrid wave energy harvester with direction self-adaptive characteristics based on an asymmetric rotating pendulum. Utilizing the asymmetric rotating pendulum and nonlinear magnetic repulsion force converts low-frequency, multi-directional wave motion into the rapid rotational motion of the asymmetric rotating pendulum and high-frequency vibration of the generator beam. Meanwhile, the rotational response characteristics of the asymmetric rotating pendulum and the traditional single pendulum were theoretically compared and analyzed, the nonlinear magnetic repulsion force was simulated and analyzed, and the efficient recombination performance of the proposed harvester was experimentally verified. Finally, the experimental results indicate that the maximum output power of the proposed harvester is 4.09 mW, which can charge a 0.66 F capacitor to 3 V within 100 min and drive a low-power temperature and humidity sensor to operate continuously for 80 min. The proposed energy harvester can effectively collect low-frequency, multi-directional wave energy, providing a feasible solution for powering low-power electronic devices.