An advanced folded piezoelectric vibration energy harvester with low resonant frequency and high power density

This paper reports an advanced folded piezoelectric vibration energy harvester (PVEH) that has excellent power generation performance at the former two-order resonant frequencies. Its volume is ∼1 cm3 and its mass is less than 5 g. Extending piezoelectric transducer sheets can effectively avoid stress concentration and greatly improve the power generation performance of the device. Besides, by adjusting the height–length ratio of the folded structure under 0.35, the device can generate power effectively in the former two vibration modes. Finite element simulation analysis by COMSOL Multiphasic was performed to fabricate and test a series of PVEHs. Their resonant frequencies and peak output powers were analyzed. The advanced folded PVEH can harvest energy effectively at the former two resonant frequencies: 58 Hz and 136 Hz. A multi-line classical energy harvesting circuit is designed to harvest the energy generated by all bimorph beams. Under 0.4 g excitation acceleration, the two peak output voltages of the energy harvesting circuit are 19.4 V and 6.32 V and the two peak output powers of the energy harvesting circuit are 336.04 µW and 77.07 µW. In the former two-order vibration modes, the power densities are 2.1 mW/cm3/g2 and 0.48 mW/cm3/g2, respectively.