Improved one-dimensional model of piezoelectric laminates for energy harvesters including three dimensional effects

The application of piezoelectric composites in energy harvesters is continuously increasing even at the microscale, with the immediate corollary of a fundamental need for improved computational tools for optimization of performances at the design level. In this paper, a refined, yet simple model is proposed with the aim of providing fast and insightful solutions to the multi-physics problem of energy harvesting via piezoelectric layered structures. The main objective is to retain a simple structural model (Euler–Bernoulli beam), with the inclusion of effects connected to the actual three-dimensional shape of the device. A thorough presentation of the analytical model is presented, along with its validation by comparison with the results of fully 3D computations

Advanced Model for Fast Assessment of Piezoelectric Micro Energy Harvesters

The purpose of this work is to present recent advances in modeling and design of piezoelectric energy harvesters, in the framework of micro-electro-mechanical systems (MEMS). More specifically, the case of inertial energy harvesting is considered, in the sense that the kinetic energy due to environmental vibration is transformed into electrical energy by means of piezoelectric transduction. The execution of numerical analyses is greatly important in order to predict the actual behavior of MEMS devices and to carry out the optimization process. In the common practice, the results are obtained by means of burdensome 3D finite element analyses (FEA). The case of beams could be treated by applying 1D models, which can enormously reduce the computational burden with obvious benefits in the case of repeated analyses. Unfortunately, the presence of piezoelectric coupling may entail some serious issues in view of its intrinsically three-dimensional behavior. In this paper, a refined, yet simple, model is proposed with the objective of retaining the Euler-Bernoulli beam model, with the inclusion of effects connected to the actual three-dimensional shape of the device. The proposed model is adopted to evaluate the performances of realistic harvesters, both in the case of harmonic excitation and for impulsive loads

Experimental verification of a bridge-shaped, nonlinear vibration energy harvester

This paper reports a comprehensive modeling and experimental characterization of a bridge shaped nonlinear energy harvester. A doubly clamped beam at large deflection requires stretching strain in addition to the bending strain to be geometrically compatible, which stiffens the beam as the beam deflects and transforms the dynamics to a nonlinear regime. The Duffing mode non-linear resonance widens the frequency bandwidth significantly at higher frequencies than the linear resonant frequency. The modeling includes a nonlinear measure of strain coupled with piezoelectric constitutive equations which end up in nonlinear coupling terms in the equations of motion. The main result supports that the power generation is bounded by the mechanical damping for both linear and nonlinear harvesters. Modeling also shows the power generation is over a wider bandwidth in the nonlinear case. A prototype is manufactured and tested to measure the power generation at different load resistances and acceleration amplitudes. The prototype shows a nonlinear behavior with well-matched experimental data to the modeling

Modeling of a Bridge-Shaped Nonlinear Piezoelectric Energy Harvester

Abstract: Piezoelectric microelectromechanical systems (MEMS) energy harvesting is an attractive technology for harvesting small energy from ambient vibrations. Increasing the operating frequency bandwidth of such devices is one of the major challenges to be solved for real-world applications. A MEMS-scale doubly clamped nonlinear beam resonator has demonstrated very wide bandwidth and high-power density among the energy harvesters reported. In this paper, a first complete theoretical discussion of nonlinear resonance-based piezoelectric energy harvesting is provided. The sectional behavior of the beam has been studied through the Classical Lamination Theory (CLT) specifically modified to introduce the piezoelectric coupling and nonlinear Green-Lagrange strain tensor. A lumped parameter model has been built through Rayleigh–Ritz method and the resulting nonlinear coupled equations have been solved in the frequency domain through the Harmonic Balance Method (HBM). Finally, the influence of external load resistance on the dynamic behavior has been studied. The theoretical model shows that nonlinear resonant harvesters have much wider power bandwidth than that of linear resonators but their maximum power is still bounded by the mechanical damping as is the case for linear resonating harvesters. ©2014Eniac joint undertaking, project Lab4MEMS (grant n°325622

Piezoelectric Transducer for an Energy-Harvesting System

A piezoelectric transducer for energy-harvesting systems includes a substrate, a piezoelectric cantilever element, a first magnetic element, and a second magnetic element, mobile with respect to the first magnetic element. The first magnetic element is coupled to the piezoelectric cantllever element. The first magnetic element and the second magnetic element are set in such a way that, in response to relative movements between the first magnetic element and the second magnetic element through an interval of relative positions, the first magnetic element and the second magnetic element approach one another without coming into direct contact, and the interaction between the first magnetic element and the second magnetic element determines application of a force pulse on the piezoelectric cantilever element