Harvesting vibration energy through a cantilever beam with enhanced harvesting capability

Piezoelectric energy harvester (PEH) is being world widely studied by many researchers due to their excellent advantages over batteries. Therefore, how to improve the capability of energy harvesting has become a hot research topic. In this study, based on the theory that the electromechanical coupling coefficient is proportional to the difference of mode shape slopes at the two ends of a piezoelectric sheet made of macro fiber composite, a modified cantilever structure consisting of two segments is proposed. The piezoelectric sheet is affixed on the segment close to the fixed end, while the segment containing the free end is rotated by 90 degrees along its axial direction. The mode shape of the cantilever structure is calculated based on the Euler-Bernoulli beam theory. Prototypes of the conventional and modified PEHs are fabricated and tested. Compared to the conventional one, the experimental result of the modified PEH demonstrates that the electromechanical coupling coefficient is enhanced by 600%, and the output power is increased by more than 300%. The proposed PEH is simple, highly efficient, and easy-realized.