Research On Power Generation Characteristics Of Non-resonant Piezoelectric Stacks

Piezoelectric generating is a new type of clean energy, has great value in MEMS and wireless sensing applications. Piezoelectric vibrator can generally be divided into two vibration modes-31 mode and 33 mode, current literature on the 33 mode is ambiguous, so, piezoelectric generation characteristics on 33 mode was studied in this paper. The output voltage and power equations on 33 mode were derived faring away the resonant frequency based on the third type of piezoelectric equations and voltage source equivalent circuit.The output voltage and power were simulated by MATLAB6.5.1 and the conclusion was drew that the output voltage is proportional to piezoelectric coefficient and exciting force and has positive correlation with patch thickness, excitation frequency and load resistance and has negative correlation with electrode area and dielectric constant. The output power has positive correlation with piezoelectric coefficient, patch thickness, excitation force and frequency and has negative correlation with electrode area and dielectric constant. The power increases first and decreases later along with the increase of load resistance, and there is a ideal load value reaching the maximal power. Performance of piezoelectric stack is similar with single patch, in addition to above, its output has positive correlation with the number of patches.The piezoelectric stack holding device and vibration energy harvesting device were designed. And the performance of the stacks affected by piezoelectric coefficient, patch thickness, excitation frequency, load resistance and electrode area was shown. The experimental results were consistent with the simulation results, which proved the correctness of the equations. Another energy harvesting device excited by feet was designed and a parallel stack was made by four PZT-51 patches, the size was 20mm×20mm×2mm. The results shown that about 170μJ energy was got at once stamp by a person weighing 70kg. The captured energy could light a LED with a simple rectifier and filter circuit as stampede lasted.This paper provides the theoretical basis and experimental guidance for piezoelectric generating technology on 33 mode, and proves it is possible to collect body energy in the movement environment as treadmills.