Analyses of Power Output of Piezoelectric Energy-Harvesting Devices Directly Connected to a Load Resistor Using a Coupled Piezoelectric-Circuit Finite Element Method

A coupled piezoelectric-circuit finite element model (CPC-FEM) is proposed for the first time to study the power output of a vibration-based piezoelectric vibration-based piezoelectric energy harvesting devices (EHDs) that is directly connected to a resistive load. Special focus is given to the effect of the resistive load value on the vibrational amplitude of the piezoelectric EHDs, and thus on the current, voltage, and power generated by the EHDs. In the literature, these outputs are widely assumed to be independent of the resistive load value for the reduction in complexity of modelling and simulation. The presented CPC-FEM uses a cantilever with sandwich structure and a seismic mass attached to the tip to study the following load characteristics of the EHD as a result of changing the resistive load value: (1) the electric outputs of the EHD: current through and voltage across the resistive load, (2) the power dissipated by the resistive load, (3) the vibration amplitude of tip displacement of the cantilever, and (4) the shift in resonant frequency of the cantilever. Investigation results shows significant dependences of the vibration characteristics of the piezoelectric EHDs on the externally connected resistive load are found, rather than independence as previously assumed in most literature. The CPC-FEM is capable of predicting the generated power output of the EHDs with different resistive load value while simultaneously calculating the effect of the resistive load value on the vibration amplitude. The CPC-FEM is invaluable for validating the performance of designed EHDs before fabrication and testing, thereby reducing the recurring costs associated with repeat fabrication and trials. In addition, the proposed CPC-FEM is potentially useful in device designs optimisations for maximal power generation.