Performance Measurement of Piezoelectric Energy Harvester with Permanent Magnet Assembly for Wearable Devices

Vibration-based energy harvester, such as piezoelectric energy harvesters (PEH), can adequately convert kinetic energy from ambient vibration to electrical energy, especially in micro-scale energy harvesting. However, these piezoelectric energy harvesters only produce desirable power output when the piezoelectric beam was vibrated at its resonance, which is usually above 50 Hz. This is considerably high for wearable devices applications, which generally operate at a vibration of less than 30 Hz. This project investigates the performance of a piezoelectric energy harvester that utilizes the magnetic interaction of its proof mass to adjust its resonant frequency. By mounting permanent magnets (NdFeB) at the tip of the beam as proof mass and placing other permanent magnets at the top and bottom of the proof mass at various distances and polarity, attractive magnetic interaction has overall best performances compared to without magnetic and repulsion magnetic interaction, which reduced the resonant frequency to 15 Hz. Without compromising the generated voltage and power output, this work has shown that energy could be harvested from a low vibration input source, that is deemed useful for powering wearable devices.