On the optimization of piezoelectric vibration energy harvester

Piezoelectric vibration energy harvesting has attracted increasing attention in the last decade, and one of the major challenges is concerning the design of these harvesters. Most researchers optimize the piezoelectric vibration energy harvester at constant excitation acceleration. However, in practical applications, the allowable stress of the cantilevered piezoelectric vibration energy harvester limits the maximum displacement of the cantilever. Thus, both the maximum displacement of the cantilever and the excitation acceleration should be considered when the piezoelectric vibration energy harvester is optimized. In this article, the damping ratio and electromechanical coefficient are optimized for maximum power output. The results show that the electromechanical conversion efficiency is not more than 50%. The results also show that the piezoelectric vibration energy harvester with low damping ratio does not always have high power output, which challenges previous literature suggestion that lower damping ratio tends to higher power output. And the analysis of the electromechanical coefficient shows that the power output decreases beyond an optimal electromechanical coefficient, which is consistent with the previous findings.