Multi-directional wind energy harvesting based on the coupling effect between a piezoelectric beam and an elastic-supported sphere

A new piezoelectric energy harvester is proposed which employs the coupling effect between a piezoelectric beam and an elastic-supported sphere to capture wind energy from multiple directions. As wind flows across the sphere, it induces vortical vibrations that transfer to the piezoelectric beam, converting wind energy into electricity. A nonlinear coupled dynamic theoretical model based on the Euler-Lagrange equation is developed to study the interactions between the sphere and beam vibrations. The vortex-induced force acting on the sphere is determined, and the dynamic model of the coupled system is validated through experiments. The results show that in order to reach convergence, at least four modes are required in the Galerkin discretization. Moreover, the output performance of the energy harvester strongly depends on the frequency ratio between the sphere and the piezoelectric beam. We find that at a frequency ratio of approximately 1.34, the harvester achieves a maximum average power of 190 µW at a wind speed of 3.90 m/s, with the lock-in region between 2.63 and 5.30 m/s. Subsequently, the impact of wind flow direction on the electrical performance of the energy harvester is investigated in a wind tunnel, by adjusting the angle between the harvester and incoming flows ranging from 0° to 360°. The findings indicate that the harvester maintains strong and consistent performance across variable wind flow directions and speeds. Particularly within the lock-in region, the output voltage fluctuations are below 5.5%, showcasing the robustness of the design. This result points to the potential utility of this novel harvester in complex environments. Our study also provides a theoretical basis for the development of small-scale offshore wind energy harvesting technologies.