Experimental investigation on performance improvement of cantilever piezoelectric energy harvesters via escapement mechanism from extremely Low-Frequency excitations

In this paper, we first design a frequency tuning device that enables the piezoelectric cantilever to operate under extremely low-frequency (below 2 Hz) excitations. Our design is mainly composed of three sections: coil spring for energy conversion and storage, escapement mechanism for frequency tuning, and piezoelectric cantilever for power generation. The prototype is capable of converting random excitation into regulated high-frequency oscillations, rendering the PEH to perform continuous high output voltage and attain low matched impedance. In experiments, this device successfully tuned the 0.75 Hz excitation into a 12.15 Hz oscillation, which is 0.68 Hz lower than the resonant frequency of the PEH. With this frequency tuning design, the performance of the PEH is less dependent on the external excitation. The instantaneous output power from the PEH on the frequency tuning device is 38.12 mu W under 1 Hz excitation, which is 91 % of the output power of the same PEH vibrating under 0.35 g acceleration, 13.2 Hz harmonic excitation. Our design can be of great significance when harnessing energy from extremely low-frequency excitation such as ocean waves.

Automated summary

The frequency tuning device successfully converts 0.75 Hz excitation into a 12.15 Hz oscillation, 0.68 Hz lower than the resonant frequency of the PEH. This design reduces the dependence of the PEH's performance on external excitation and can significantly improve energy harnessing from extremely low-frequency sources like ocean waves.