Piezoelectric vibration energy harvester with two-stage force amplification

A novel portable energy harvester using 3-3 mode piezoelectric stack with two-stage force amplification is proposed. It can obtain 21 times force amplification with 18% energy transmission ratio and generate electrical energy up to 79 times more than one piezoelectric ceramic of lead zirconate titanate (PZT) stack. Dynamic experiments demonstrate that the harvester with one-and two-stage force amplification can generate the maximum electrical power of 74.9mW/g(2) from one PZT stack at resonance frequency 235Hz with matching resistance of 268Ohms and 2642mW/g(2) from three PZT stacks at resonance frequency 37Hz with match resistance of 1722Ohm under 100g proof mass and 0.1g acceleration. Theoretical electromechanical modeling is established to reveal the working mechanism of force amplification and to predict electricity generation. Comparison of the predicted electricity with experimental results verified effectiveness of electromechanical modeling and optimization design methodology with consideration of tradeoff among force magnification ratio, energy transmission efficiency, and maximum stress. This piezoelectric energy harvester using two-stage force amplification can not only significantly improve power generation but also reduce the resonance frequency Moreover, the resonance frequency can also be adjusted by adjusting the mass load, by which a two-stage energy harvester can be applied to meet requirements of various bandwidths in low-frequency range.