Improving low-frequency piezoelectric energy harvesting performance with novel X-structured harvesters

Vibration energy harvesting systems via an X-structure coupled with piezoelectric patches of special arrangements are investigated in this study. Two piezoelectric harvesters are specially installed on the X-shaped structure to explore potential benefits that the X-shaped structure could provide, and each piezoelectric pad has two layers composed of a polyvinyl chloride base patch and a micro-fibre composite patch. The theoretical analysis and experiment results indicate that the energy harvesting performance of the proposed novel arrangements of the piezoelectric harvesters can be enhanced especially in low-frequency range (below 10 Hz), compared with conventional cantilevered piezoelectric harvesters. More and higher energy harvesting peaks can be created and the effective harvesting frequency band can be obviously enlarged by expanding it to low-frequency range with the proposed methods. The X-structure-based generators can enable piezoelectric materials to harvest power from low-frequency vibration sources due to its advantages in designable equivalent nonlinear stiffness, which can be easily tuned by adjusting the key structural parameters. The design and results would provide an innovative solution and insight for smart piezoelectric materials to improve the energy harvesting efficiency in the low-frequency range including small-scale ocean wave power harvesting, human motion power and animal kinetic power harvesting, etc.