Schwarz, Michael, M.Sc.

A piezoelectric vibration-based energy harvester (PVEH) consists of an electromechanical structure and an electric circuit, influencing each other. Mechanical vibrations excite the electromechanical structure. Due to the piezo-electric properties of the material, the mechanical vibrations generate electrical charge changes, which can be stored as electrical energy by the connected electric circuit. The efficiency of the energy harvester depends on many different factors, as the electro-mechanical coupling coefficient of the material, the relation of the excitation frequency to the resonance frequency of the structure or the suitability of the electric circuit.

Macroscopic simulations based on the finite element (FE) method are a promising tool to better understand and optimize the performance of PVEH. To do this, it is necessary to accurately model the electromechanical structure, the circuit, and the coupling between the two. Using the FE method to simulate the electromechanical structure, in contrast to simplified analytical approaches, allows in particular to consider various nonlinearities, e.g. due to the material bahvior, large deformations, nonlinear damping or nonlinear electric circuits. Other physical couplings such as pyroelectric behavior or more complex materials such as polymer-ceramic composites can also be considered.

The aim of this project is the macroscale modeling and simulation of PVEH. In the first phase of project C, a FE based system simulation approach for nonlinear electromechanical structures coupled to nonlinear electric circuits was developed. Furthermore, an implicit coupling method between a finite element solver and an electronic circuit simulator was introduced, which offers greater freedom regarding the choice of software. In the second phase of the project the developed system simulation approach is extended to nonlinear material behavior of lead-free ferroelectric materials, e.g. BCZT and KNN, or polymer-ceramic composites containing such particles. In the latter case, numerical homogenization is used to determine the macroscopic behavior of the composites.