Magnetically frequency-modulated piezoelectric energy harvester for ultra-low-frequency wave motion

In this paper, a magnetically frequency modulated piezoelectric energy harvester (MFPEH) for ultra-low-frequency wave motion is proposed. The MFPEH employs multiple sets of magnets coupled to achieve optimal electrical output at ultra-low-frequency excitation (<2 Hz). A straight rack and pinion drive converts the vertical motion of the float into rotational motion, and magnets on the rotor provide excitation to the piezoelectric cantilever. As a result, the MFPEH converts random wave motion into steady rotational motion. The MFPEH uses a rational combination of multiple sets of magnets and frequency modulation by magnetic coupling, which greatly improves the output performance. This paper describes the key factors affecting the output performance of MFPEH. An experimental system simulating a wave environment is designed and constructed. Under the most effective experimental parameters, the MFPEH achieves an optimal power of 32.76 mW. In a real wave environment, the MFPEH was able to illuminate 85 LEDs and power a thermohygrometer for normal operation. These results validate the potential of the MFPEH to power small electronic devices.