Design Of Piezoelectric Stack-Buzzer Composite Energy Harvester

Using piezoelectric energy harvesting technology to convert vibration energy in the environment into electrical energy to supply power to sensor nodes is an effective way to extend the life of sensor nodes.The common vibration in the environment has the characteristics of low frequency and low vibration acceleration.Due to the large rigidity and high natural frequency of the piezoelectric stack energy harvester,it is difficult to resonate under low frequency vibration conditions,and the electromechanical conversion efficiency is low.In this paper,a piezoelectric stack-buzzer composite energy harvester is designed and manufactured:the buzzer not only collects vibration energy,but also acts as a spring,which can make the composite energy harvester resonate under low-frequency vibration,amplify the force of the stack,and improve the electromechanical conversion efficiency of the piezoelectric stack.The influence of the structural parameters of the composite energy harvester on the energy harvesting characteristics is studied from the theory and simulation aspects.The voltage and power of the composite energy harvester are deduced when open circuit and external resistance are connected,and the theoretical model of the composite energy harvester installed on the ideal exciter and the electric vibration exciter is established.Then,the finite element simulation of the stacked energy harvester and the composite energy harvester was carried out.Through theoretical analysis and finite element simulation,the effects of the area and height of the bottom of the stack,the thickness and number of layers of piezoelectric ceramics,the mass and stiffness of the energy harvester,and the damping ratio parameters on the energy harvesting characteristics of the energy harvester are studied.A composite energy harvester was fabricated and the effects of geometric parameters of the energy harvester and the external load on the energy harvester characteristics were studied by experiments on the vibration exciter,and the parameters of the energy harvester were identified.The effect of the mass and buzzer at the top of the composite energy harvester on the open circuit voltage of the energy harvester was studied.the load voltages of the stack and buzzer in the composite energy harvester were measured,the experiment showed that the load power of the stack and buzzer was 3.5 μW and 4.3 m W at matching resistance of 3 MΩ and 35kΩ,respectively.According to the experimental data of the energy harvester installed on the vibration exciter,the parameters of the vibration exciter and the energy harvester were identified,and the energy harvesting characteristics of the energy harvester installed on the ideal vibrating body with constant acceleration were predicted.A Synchronous Electric Charge Extraction(SECE)circuit and an energy management circuit based on the LTC3129-1 chip were fabricated,and energy harvester experiments were carried out on the excitation platform and the actual motor.The experiment on the excitation platform shows that the energy collection efficiency of the SECE circuit after optimization is26%.Under the condition of 1 g vibration acceleration,the power of the composite energy harvester with the energy management circuit is 4.79 m W,which realizes continuous power supply for Mijia Bluetooth thermometer and hygrometer.Experiments on the building heating water pump motor show that the energy collected by the composite energy harvester can intermittent power the Mijia thermometer and hygrometer under 0.02 g vibration acceleration.