Multi-physics modeling of piezoelectric energy harvesters from vibrations for improved cantilever designs

This study investigated piezoelectric cantilevers for energy harvesting using multi-physics modeling. The cantilevers with multiple degree-of-freedoms (DOFs) were designed with higher potential to match multiple-frequency vibrations of structures. Finite element models (FEMs) of cantilevers with different design parameters were built and verified with laboratory measurements. As results, multiple vibration modes with different bending conditions were captured by FEM outputs under resonant frequencies. The parametric analysis was performed to analyze the effects of cantilever length, width, thickness and mass. It was found that adjusting the cantilever design acquired the resonant frequencies in a wide range of 5 Hz–35 Hz, which potentially fitted the vibration scenario of a typical bridge structure. Under the cantilever design principle proposed in this study, as the DOF was increased, the maximum voltage outputs or the power outputs still remained the same level, respectively at 30 V or 5 mW, with no extra coverage area required from the multiple-DOF cantilever. All trends of resonant frequency changes via design parameter adjustments captured in this study will also serve as references for achieving specific design optimization strategies on the multiple-DOF cantilever designs, which will be varied based on the structure vibration scenarios in the field.