Design, Modeling, and Simulation of Piezoelectric and Magnetoelectric Devices for Multimodal Energy Harvesting Applications

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Chen, Nan
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Middle Tennessee State University
The power consumption of electronic devices reduces as the size of these devices shrinks [1]. Today most portable and wearable devices are still powered by batteries. Researchers have been considering various renewable energy sources include solar, wind, tidal, and mechanical vibrations [1]. The application demands the electronic devices being used in any weather conditions, anytime, and anywhere [1]. Mechanical vibrations are abundantly available in structures such as bridges, machinery, engines, and aircraft. Hence, several researchers have been developing self-powered MEMS (Microelectromechanical Systems): energy harvesters which are made of piezoelectric materials or magnetostrictive materials to provide power for low power electric devices at the mW or μW level using mechanical vibrations [1] [2]. All piezoelectric materials and magnetostrictive materials have a Curie temperature. When the operating temperature is higher than the Curie temperature, piezoelectric and magnetoelectric materials lose the ability to generate electric power from mechanical vibration or magnetic fields in an environment [2] as the aligned electric and magnetic dipole moments become disordered by the thermal disturbance. The Curie temperature of the piezoelectric materials and magnetoelectric (ME) materials can be as high as 40 ~ 180 °C for the PZT based piezoelectric materials and up to 680 °C for Fe based magnetostrictive materials [2]. Given the fact that the Curie temperature of piezoelectric and magnetoelectric materials is much higher than the normal operating temperature range of batteries, composite piezoelectric and magnetoelectric energy harvesters are more suitable to operate in extreme environments in terms of wider operating temperature range. To answer the question of how to harvest energy from a broad range of mechanical vibrations in an environment, we have developed multiple stages of the research proposal to address the challenges in designing various multimodal energy harvester devices. These designs include piezoelectric harvesters through a multi-beam approach, a one-piece trapezoidal approach, and a two-piece trapezoidal approach using our composite piezoelectric material. Full-width half-maximum (FWHM) bandwidth is one of the methods to benchmark the vibration bandwidth of our piezoelectric and magnetoelectric (ME) vibration energy harvesters (VEH). Our piezoelectric and magnetoelectric (ME) VEH models are simulated using COMSOL Multiphysics software. COMSOL Multiphysics is a commercial finite element analysis computer simulation software that specializes in solving two or more coupled multi-physics problems and is widely used in engineering fields, research & product development, and academic communities. We expanded our research from a simple rectangular bimorph model to the multi-beam model and nonlinear models, and we demonstrate the wider band of the device. We further developed nonlinear shapes such as the trapezoids to investigate the frequency bandwidth of the device. The one-piece trapezoidal model was expanded to a two-piece trapezoidal beam harvester model to demonstrate that the two-piece trapezoidal piezoelectric cantilever can achieve a broader vibration frequency response. The two-piece trapezoidal piezoelectric composite beam design resulted in a broader bandwidth of 5.6 Hz while generating a maximum power density of 16.81 mW/cm3, whereas the one-piece trapezoidal beam generated a maximum power density 10.37 mW/cm3 with a bandwidth 2.9 Hz in our previous work [3] [4]. These results helped us to design for broader band piezoelectric and ME energy harvesters with higher electric power density. For single ME rectangle energy harvesters, the peak electric power reaches 8.99 mW and peak electric power density at 192 mW/cm3 via the optimal resistor of 0.5 MΩ. For the one-piece trapezoidal ME energy harvesters, we saw the peak electric power reaching 37.1 mW and peak electric power density of 56.2 mW/cm3 with an optimal resistance of 0.013 MΩ. In this work, we have advanced our research from composite piezoelectric beam models to novel trapezoidal magnetoelectric composite beam designs for harvesting not only vibration energy but also magnetic energy from the surrounding environment.
Bimorph, Broadband, Energy harvester, Magnetoelectric, Piezoelectric, Polycrystalline, Computer science