Impact based frequency increased piezoelectric vibration energy harvester for human motion related environments

This paper presents a frequency increased piezoelectric vibration energy harvesting device where the low frequency periodic impact of a driving beam with a horizontally extended rectangular tip makes two piezoelectric generating beams to vibrate at the same time, with their higher resonant frequencies, producing higher power output. The dimension of the flexible driving beam was 58×4.8×1 mm³ and that of each piezoelectric generating beam with styrene support was 15×3.5×0.8 mm³. Each generating beam of the proposed energy harvester produced a maximum peak output power of 46.51 μW across an optimum resistive load of 200 KΩ under 4 ms^-2 acceleration and was increased up to 129.15 μW while the acceleration was increased up to 6 ms^-2 at an operating frequency of 12.5 Hz. The output of both generating beams with series connection doubled the overall output of the device.