Designing a road energy harvester with multiple piezoelectric cantilever beams and a single tip mass

As the importance of climate change is rising up, there is an attempt to harvest unused energy to reuse it in a form of electricity, which is called energy harvesting. It has a possibility to be applied to a macro-power source such as a road energy harvesting. We have designed a new road energy harvester, in which all the cantilever beams share a single tip mass. This mechanism allows all the beams to have the same bending trajectory and to generate voltages identically. It eliminates the need of multiple rectifying circuits since all the power outputs have the same waveforms and a negative interference barely happens. We have modeled a lab-scale experiment and measured its frequency matching results. The single cantilever beam without any tip mass has a natural frequency of 60 Hz. When the tip mass is attached to the beam, the natural frequency becomes dropped to 6.5 Hz. When three beams are connected together with single tip mass, the frequency becomes a little larger than that of a single beam, which is 15.5 Hz. The major reason of this difference is that the weight of the tip mass cannot be spread evenly to the cantilever beams since they are bulky and has to give more weight to a lower beam. But we can match all the phases of the output powers from each beam. It will help us eliminate unnecessary rectifying circuits and predict an aspect of a beam deflection and its power output.