Impedance-based finite element modelling of a highly-coupled and pre-stressed piezoelectric energy harvester

This work presents an experimentally validated impedance-based finite element model (FEM) of a highly-coupled pre-stressed piezoelectric energy harvester (PEH) with piezoelectric multilayer stacks (PMSs). The FEM first simulates the status of the PEH as a result of the static pre-stress. It then analyses the internal impedance$|Z_{in}|$ of the pre-stressed PEH, which is used as the optimal load resistance Ropt for power output generation. The developed FEM is able to precisely predict (1) the maximum power output at each frequency without the tedious load-resistance sweeping approach traditionally used; (2) the dual-power-peaks phenomenon of highly-coupled PEHs, which cannot be observed when using the traditional approach of $R_{opt}=1/\omega C_{P}$. This model provides a useful tool for the design and optimization highly-coupled piezoelectric energy harvesters.