Comparison of Piezoelectric Materials for Vibration Energy Conversion Devices
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Comparison of Piezoelectric Materials for Vibration Energy Conversion Devices Dongna Shen1, Song-Yul Choe2, and Dong-Joo Kim1 1 Materials Research and Education Center, Auburn University, Auburn, AL, 36849 2 Department of Mechanical Engineering, Auburn University, Auburn, AL, 36849
ABSTRACT Piezoelectric materials have been investigated as vibration energy converters to power wireless devices or MEMS devices due to the recent low power requirements of such devices and the advancement in miniaturization technology. Piezoelectric power generation can be an alternative to the traditional power source-battery because of the presence of facile vibration sources in our environment and the potential elimination of the maintenance required for largevolume batteries. To date, Lead Zirconium Titanate (PZT) has been commonly exploited as a piezoelectric material for energy conversion since it can generate higher power densities even at low-g (< 1g) vibration environments. The high fragility of PZT, however, can limit its applicability at high-g conditions. Therefore, other types of piezoelectric materials such as polymers and composites are necessary to investigate the applicability at severe vibration conditions. As piezoelectric materials, ceramic PZT, Polyvinylidene fluoride (PVDF) copolymer, and Macro Fiber Composite (MFC) were utilized in this study. Three piezoelectric power generators based on a cantilever beam structure were designed and fabricated by considering matching the resonant frequency with environmental vibration. Especially, the design of PZT generator was optimized by a compromise between the output power and the maximal g-value without device failure. The energy conversion of all three types of generator devices was systematically evaluated. All three devices were measured to determine if they could generate enough power density to provide electric energy to a wireless sensor or a MEMS device. The PZT device shows the highest output energy density and the PVDF device has the highest durability to operate at high-g vibration conditions. INTRODUCTION The study on power harvesting has been increasing in recent years because the technology could realize completely self-powered wireless devices without any maintenance required. Especially with the developed electronic technology, power consumption of wireless device has been highly reduced due to miniaturization technology. Although solar cell can produce higher power densities, mechanical vibration energy can be an attractive energy source in the ambient without enough light. There are three common mechanisms such as piezoelectric, electromagnetic and electrostatic ones to harvest or convert the vibration energy to electrical energy. Among them, piezoelectric power generation shows advantages over electromagnetic and electrostatic ones, for instance, simplicity, high efficiency, precise control, batch fabricability, etc.
With high coupling coefficient and low cost, ceramic PZT is a common piezoelectric material that has been extensively studied
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