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 R opt 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.