A Multi-Mechanisms Composite Frequency Up-Conversion Energy Harvester

In this paper, a novel broadband hybrid piezoelectric-electromagnetic-electrostatic energy harvester with frequency up-conversion is proposed to improve the harvesting bandwidth and energy conversion efficiency. The designed device generates vibration energy with much higher frequency than ambient vibration frequency, which uses the magnet to impact periodically on the piezoelectric cantilever with the top electrode of electrostatic element. The dynamic model of the hybrid energy harvester is established, and performances are experimental tested under the sinusoidal excitation and practical application environment. The results show that multi-mechanisms composite structure can realize the complementary advantages of electrostatic-piezoelectric-electromagnetic mechanisms and improve the energy conversion efficiency effectively compared with a single harvesting mechanism. The fabricated harvester can output electric energy in the frequency range of 1–38 Hz, which significantly reduces frequency dependence, and the maximum power is measured to be 11.7 mW and 12 mW during cycling and walking respectively, which is the sum of the power generated by three different elements. Furthermore, the fabricated prototype can also light up six light-emitting diodes (LEDs) simultaneously when handy shaking.