Analysis of Bimorph Piezoelectric Energy Harvester Attached With a Cantilever Beam Under Excitation

Abstract

In this thesis work a cantilever structure based bimorph piezoelectric energy harvester have been designed and analyzed using lead zirconium titanate (PZT 5A) as piezoelectric material and steel as the elastic substrate layer. This energy harvester has one of its end clamped to a vibrating source from where vibration is being induced into the cantilever beam and a proof mass is mounted on top of the other end. The energy harvester model is designed and finite element model (FEM) simulation is done in COMSOL Multiphysics for the conversion of mechanical vibrations to electrical energy. Different structural parameters, including piezoelectric layer thickness, proof mass volume and proof mass material has been changed to increase the output electrical energy while keeping the same resonant frequency. First the frequency response of the device is performed which shows that the resonant frequency occurs at 71 Hz at a peak output voltage of 5.16V for a mechanical input power of 1.25mW resulting in an electrical output power of 1.2mW. Then, with the increase of both the top and bottom piezoelectric layer thickness, it was found that the peak voltage decreases with the increase of resonant frequency. Again with the increase of proof mass volume, it was found that the peak voltage increases with the decrease of resonant frequency. Finally, by increasing both the piezo electric layer thickness 1.33 times of initial value 0.6 mm and proof mass volume 2 times of initial value 95.2mm3, voltage increases to 7.675V from initial value of 5.16V at a fixed resonant frequency of 71hz. Similar results are found at other data points by keeping increment ratio same. A load response analysis for different piezoelectric layer thicknesses was also done. At last after observing the simulation results for different proof mass materials and volume, it was found that it has negligible effect on performance if the mass remains same.