Study On Mechanical Properties And Energy Harvesting Of Beam-type Vibration Energy Harvester Based On Zinc Oxide

Zinc oxide(ZnO)film is a typical wide band gap semiconductor with higher melting point,higher thermal stability and chemical stability than third-generation semiconductor materials,hence ZnO has a natural advantage in the field of photovoltaic devices.Compared with other piezoelectric materials,zinc oxide is more in line with the green ecological background as its smaller internal resistance,less energy consumption and non-toxic.Whereas,there are few researches on vibration energy collectors using zinc oxide as a piezoelectric element,and the theory is not mature in domestic.This paper studies the vibration energy harvester of cantilever beam structure based on zinc oxide film.(1)The corresponding piezoelectric equation is determined according to the piezoelectric effect,the electromechanical conversion mode of the piezoelectric crystal and the relevant boundary conditions.The model of the piezoelectric energy harvesting system is established by combining the “spring-damping-mass” vibration model and piezoelectric equation.Then,we can conclude that the relationship between the voltage generated by the piezoelectric element and the amplitude of the applied vibration.The influence of the modal frequency of the cantilever beam,the damping of the system and the physical properties of ZnO on the output voltage at both ends of the piezoelectric element is analyzed.(2)Based on the cantilever beam vibration energy harvester,the relevant dimensions and harmonic response results of the vibration energy harvester are obtained by piezoelectric coupling analysis.In order to determine the optimal zinc oxide film thickness and the optimal sinusoidal excitation level,thereby improving the conversion efficiency of the vibration energy collector.(3)The properties of zinc oxide thin films prepared under different process parameters were investigated.The surface morphology and the intensity of crystal axis orientation growth of the zinc oxide film were tested.The influence of different process parameters on the grain diameter of zinc oxide film and the relative strength of c-axis orientation was analyzed.The vibration energy collection experiment system was designed to reveal the influence of different performances of zinc oxide film on the voltage output and power output of the vibration energy harvester.(4)The relationship between the output power of the traditional energy harvesting circuit(SEH)and the load is derived,and the reasons for the obvious defects of the traditional energy harvesting circuit are analyzed.The switching circuit is designed according to the resonance characteristics and the electrical characteristics of the semiconductor device,and an improved synchronous charge extraction(SCE)circuit is proposed.The output power curve of the improved SCE circuit is obtained by using MULTISIM simulation analysis.According to the energy harvesting experimental system designed in this paper,the output power of the improved SCE circuit is tested.The results show that the output power is 3.6 times of the SEH output power,and the output power decreases from 15.4% to 1.1% with load fluctuation.Effectively solve the power supply problem of micro power components.