Research On Piezoelectric Miniature Energy Harvester

Piezoelectric miniature energy harvester is a novel device that will replace traditional batteries in the future.It has become a research focus in recent years.The energy harvester has a higher power output based on the piezoelectric effect.The energy transmission can be carried out conveniently and safely when the external excitation is sound energy.The research on piezoelectric miniature energy harvesters has begun to take shape,and will soon be used in medical implantation equipment,environmental monitoring and other fields,but there are still many shortcomings that need to be resolved,such as low energy conversion rate and single energy harvesting direction and narrow working frequency band.The main research contents of this paper are as follows:（1）The research background of piezoelectric miniature energy harvesters is introduced.Based on the sound energy as the energy source,the energy harvester is classified according to whether it contains a cavity and the type of cavity,and the current research status at home and abroad is introduced.The advantages of piezoelectric miniature energy harvesters using acoustic energy as the energy source are summarized compared with traditional energy harvesting devices.Moreover,the shortcomings and the improvement of current energy harvesters in practical applications are analyzed.（2）According to the acoustic-electric theory of piezoelectric miniature energy harvester,firstly,the basic theory of piezoelectricity is studied.Secondly,the acoustic energy amplification is analyzed.Using the method of electric-acoustic analogy,the expression of the external excitation on the piezoelectric film is obtained.Thirdly,the expression of the output voltage is obtained by using the lumped parameter model and the distributed parameter model.According to the coupling theory of sound pressure amplification and acoustic-electric conversion,the output voltage,the output power,the resonance frequency and other properties of the energy harvester can be analyzed.（3）A quarter-spherical structure is proposed based on the basic structure of the Helmholtz cavity.Lumped parameter model is used for numerical calculation.Comparing the results of numerical calculation with the results of software simulation,this energy harvester can amplify the sound pressure by 43 times at the acoustic resonance frequency.The simulation result shows that its maximum output voltage is about 28m V at 40.6k Hz.Its frequency band and power density are approximately 470Hz and 12.7（?）Wcm^-2,respectively.Compared with the previous structure,its resonance frequency band and output power density have been significantly improved.（4）An omnidirectional energy harvester is proposed based on a quarter-spherical structure.Compared with a quarter-spherical structure,it can collect sound energy in six directions at the same time.Based on the distributed parameter model and simulation method,the results show that the sound pressure amplification of the energy harvester is about 51,the maximum output voltage at the resonance frequency of 3.5*10⁴Hz is 70.95m V,and the maximum output power is 0.45μW.The effective bandwidth is about 700Hz,and the energy conversion efficiency has reached 23%,which is79.2%and 800%higher than the quarter-spherical structure,respectively.It has a further significant improvement in key parameters.In summary,a quarter-spherical Helmholtz resonant cavity energy harvester and an omnidirectional Helmholtz resonant cavity energy harvester are designed in order to solve a series inherent problems of piezoelectric energy harvesters.The numerical calculation and theoretical simulation research are carried out.The final results show that they have significantly improved the performance of traditional devices in terms of energy harvesting directionality,energy conversion efficiency,and output resonance frequency band.