Principal And Experimental Research Of Energy Harvesting Devices Based On Piezoelectric Effect

With the rapid advance in the wireless technology and low-power electronics in the past two decades,it becomes possible to utilize energy harvesting devices to support wireless sensor node or low-power electronic devices.At present,harvesting and utilizing various forms of energy(such as thermal energy,solar energy,electromagnetic wave energy,wind energy and mechanical energy,etc.)has been extensively studied.In this dissertation,based on acoustic meta-materials and piezoelectric effect,the various types of acoustic energy piezoelectric generator and the vibration piezoelectric generator were designed and verified,and the theoretical analysis,experimental testing,and performance optimization were performed.The main works and novel researches performed in this dissertation include:1.For infrasound frequency(<20 Hz),a pendulum piezoelectric generator for collecting infrasound frequency vibration energy was designed,which utilizes a simple pendulum structure to absorb infrasound vibration energy and then uses the pendulum to impact the piezoelectric lzod for power generation.Based on the piezoelectric constitutive equations and basic theory of structure vibration,the influence of structural parameters on the piezoelectric generator performance was analyzed briefly.A finite element model with a coupling of impact,vibration,piezoelectricity,and circuit is established and used to analyze the output voltage and power.Finally,the power generation performance of the pendulum piezoelectric generator prototype was experimentally tested.2.Based on the acoustic artificial meta-material theory,the broadband energy harvesting devices were designed to harvest the elastic wave energy in the solid.Two kinds of round acoustic fence(RAF)which are mounted on the surface of solid sheet are proposed and studied.Based on both RAFs,a sound energy harvester is designed to harvest acoustic energy propagating inside a piezoelectric sheet.Elliptical acoustic fence structure,which uses ellipse geometric features,can focus sound waves emitted from one focal to another focal position and improve the energy harvesting efficiency.Moreover,a ring acoustic fence with gaps is proposed to collect acoustic energy in a region of the vibration plate.Compared with the elliptical acoustic fence,this structure is not sensitive to vibration source position,and can work with multiple simultaneous excitation vibration sources.In this paper these two structures were tested and simulated by finite element method.3.Based on the acoustic artificial meta-material theory,the broadband energy harvesting devices were designed to harvest the sound waves energy in the air.For the acoustic waves propagating in the air,an acoustic energy harvester based on subwavelength reflection acoustic grating structure and piezoelectric effect is demonstrated.With the plane-wave expansion method and numerical method,the acoustic characteristics of the reflection acoustic grating are calculated theoretically.The physical mechanism for the abnormal Fabry-Perot resonance has been discussed and the influence of structural parameters has been studied.Based on the above reflecting acoustic grating structure,a sound energy generator which can work in the subwavelength range was designed and tested.Finally,the structure and parameters of the grating have been optimized to improve the working bandwidth of the power generator.4.It has been a challenge to determine the optimal energy-storage capacitance in piezoelectric vibration energy harvesting systems for a given working time.In this dissertation,the optimal value problem of the storage capacitor and its relationship to the generator circuit parameters at a given time charging condition has been studied,where the capacitor is charged by the AC piezoelectric generator via a standard full-wave rectifier.With the PSPICE software and equivalent circuit method,the above problem has been investigated numerically and analytically.By optimizing the capacitance of capacitor,the energy output of the power generator can be improved.The simulation result was verified by experiments.