Harvesting airflow energy from circular cylinder wake via a thin polyvinylidene fluoride film

Abstract

To improve the characteristics of airflow energy harvesting, this paper presents a new piezoelectric wind energy harvester (PWEH), in which a polyvinylidene fluoride (PVDF) film was directly located in the wake of the circular cylinder. Four important parameters were independently varied for detailed experimental investigations: wind speed, spacing ratio for the distance between the center of the circular cylinder and the tip of the PVDF film to the circular cylinder diameter, diameter of the circular cylinder, and load resistance. The results indicated that the designed PWEH performed optimally with the occurrence of resonance, maintaining a relatively high output when significantly exceeding the resonance wind speed. The PVDF film inhibited the vortex shedding of the circular cylinder, which weakened with increasing spacing ratio. The optimum value of the spacing ratio should be approximately 2.5, which yields an effective coupling between the vortex and structure. The diameter of the circular cylinder played an important role in determining the output power. The match between the load resistance and PWEH also contributed to the high-level performance. Moreover, with an increase in the diameter of the circular cylinder, the increasing blockage ratio unexpectedly enhanced the vortex shedding frequency and decreased the theoretical resonance wind speed, which provided a new orientation for improving the performance of such PWEHs.