Dual Resonator-Type Electromagnetic Energy Harvester for Structural Health Monitoring of Bridges

Abstract

A dual resonator with electromagnetic transduction was developed to harvest bridge vibration energy at low acceleration and low frequency. The harvester had two cantilever beams: one to carry magnets and the other to carry the coil. The coil was held by the coil holder on the coil-beam in a vertical direction to have a poling direction of magnets perpendicular to it. The device was characterized in-lab and in real bridge environment. In in-lab experimentation at acceleration. In the lab, at acceleration of 0.07 g, the harvester produced 2.7 V voltage and 13 mW power (555 Ω optimal load resistance) output at the first resonant frequency of 3.2 Hz, and output voltage of 3.1 V and 7.8 mW power (at optimal load resistance of 1,200 Ω) at the second resonant frequency of 4.2 Hz. Furthermore, when the voltage was rectified from AC to DC and at 100 kΩ optimal load resistance, 0.5 g acceleration, the output voltage of 19.4 V and power of 3.764 mW was available at 3.2 Hz frequency. A battery was also charged with the DC output of the harvester. Moreover, the real bridge environment characterization tests were made on two prestressed I-section concrete bridges. The harvester on one bridge location produced a peak load voltage of 0.27 V and a peak power of 0.13 mW at resistive load of 555 Ω and 0.024 g peak bridge acceleration. At the second bridge, where the peak acceleration was 0.017 g, the harvester successfully generated a load voltage of 0.32 V and power of 0.18 mW.