Hybrid vibro-acoustic energy harvesting using electromagnetic transduction for autonomous condition monitoring system

Condition monitoring systems (CMS) play a significant role in enhancing performance and lowering failure losses in any industrial setup. Appropriate wireless sensor nodes (WSNs) used in CMS will permit the user to check the live status of machines, however, these WSNs are facing the periodic replacement and recharging problems of batteries. Energy harvesters, used to scavenge ambient energy, are viable alternatives to batteries for achieving the self-sustained long-term operation of WSNs. Ambient vibration and acoustic energies are abundantly available in the industrial environment. The currently available energy harvesters are utilizing only vibration or acoustic energy, however, research on harvesters using both vibration and acoustic sources is missing. We present a new hybrid vibro-acoustic energy harvester (HVA-EH) using electromagnetic transduction, where the power to the WSNs can be harvested from both vibration and acoustic sources simultaneously. The architecture, working principle, fabrication, and experimentation of the HVA-EH are discussed. The HVA-EH was operated at a low vibration and acoustic frequencies and low acceleration and sound pressure levels (SPL). At matching impedance, the maximum power generated by the HVA-EH under vibration energy at zero SPL is 372 μW at acceleration level of 0.3 g and under acoustic energy at zero acceleration level is 271 μW under SPL of 130 dB. While, under a hybrid environment, the HVA-EH generates maximum power of 153 μW, 361 μW, and 656 μW at vibration levels of 0.1 g, 0.2 g, and 0.3 g respectively, under SPL of 130 dB at 2nd acoustic mode (495 Hz). The results are promising and the ability of harvesting low-frequency sound and vibration simultaneously makes the HVA-EH an energy efficient system. Furthermore, this study demonstrates the possibility of new solutions to the problems of WSNs utilizing both sound and vibration energy resources.