Over the last decades, a number of researchers have focused on the conversion of available energy usually dissipated in the form of heat, i.e., energy from oscillating structures, into electric energy, providing an alternative power supply for low-power devices. One of the most promising and frequently encountered ways to achieve this goal seems to be via electromechanical energy conversion employing piezoelectric composite strips and plates undergoing mechanical vibrations. Current research attention is focused upon nonlinear piezoelectric energy harvesters (PEH) based on buckled (monostable and bistable configurations) strips and plates. These configurations are deemed to be efficient in electromechanical energy conversion within a broadband vibration frequency range. However, from the aspect of simulation capabilities, most works are based on simplified nonlinear models (Duffing oscillators, and single-mode vibrating systems), which predict the dynamic behavior of the harvesting device but lack accuracy.This research work focuses on the application of a computational tool based on coupled electromechanical nonlinear structural mechanics to provide robust predictions for the nonlinear dynamic response of vibrating piezoelectric buckled plates and strips. Subsequently, the coupled electromechanical model which includes the structure and a piezoelectric element connected to an electric circuit will realistically simulate the oscillatory response of the structure. This model will provide accurate simulations of the complex nonlinear dynamic behavior and electromechanical efficiency of PEH, enabling detailed tailoring of its structural and operational parameters according to the application operational conditions aiming at maximum system energy conversion efficiency. Studies of the current work will focus on the presence of resistive and inductive loads connected to the piezoelectric terminals, as the means for enhanced electromechanical coupling and energy harvesting.The proposed PEH setup will be investigated experimentally also. The first objective of this study will be to validate the numerical models. Three different harvesting circuits will be tested on the experimental set up quantifying the available power on the circuit outputs based on various operational conditions. The harvesting circuits include (i) an in-house circuit consisting of a diode rectifier, a capacitor charging from accumulating electric current and a load with a switch that discharges the capacitor, (ii) a custom circuit including a full-wave rectifier connected to a commercial ultralow-power, high-efficiency energy harvester, and battery charger, implementing the maximum power point tracking function (MPPT) and integrating the switching elements of a buck-boost converter and, (iii) an off-the-shelf commercial harvesting module.

Computational and Experimental Efficiency Investigation of Nonlinear Energy Harvesting Systems Based on Monostable and Bistable Piezoelectric Beams

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2021/volume/85499

ASME 2021 Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS2021)

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