Low-frequency, broadband piezoelectric vibration energy harvester with folded trapezoidal beam.

To efficiently scavenge the energy from low-frequency ambient vibrations, this paper proposed a piezoelectric energy harvester (PEH) with a six-segment folded trapezoidal beam. The new configuration provides the PEH with a lower natural resonant frequency and closer resonance peaks, which makes the harvester suitable to daily vibrations with more functioning resonance modals. Meanwhile, the folded geometry extends the whole length of beam, and then induce a larger strain in the clamped end, leading to a more favorable output voltage. The experimental results show that the proposed structure obtains 5 resonant peaks in 0-30 Hz and an operating bandwidth of 11 Hz. The highest open-circuit output voltage is 20.78 V, and the optimized output power is 217.201 µW.