Small-Scale Wind Energy Harvesting From Flow-Induced Vibrations

Abstract

Significant wind energy exists in the boundary layers around naturally occurring and manmade structures. This energy source has remained largely untapped, even though it presents a significant source of energy for powering wireless devices in built-up areas. This paper discusses a study on harnessing energy from piezoelectric transducers by using bluff body and vortex-induced vibration phenomena induced by low-speed flows. The proposed devices are miniature, scalable, aeroelastic wind harvesters designed for extracting turbulent, low-speed wind energy from the boundary layers around structures. The design configuration consists of a bluff body with a flexible piezoelectric cantilever attached to the trailing edge. In this design, transverse vibrations are induced in the piezoelectric members by alternating vortex shedding. The multi-physics software package COMSOL is used for coupled simulation of the fluid and structural domains, and Matlab is used to couple the structural deformations to the attached power harvesting circuitry. The design and environmental parameters are varied to optimize the configuration and to identify the significant parameters in the design. The lock-in phenomenon, in which the vortex shedding frequency is entrained to the fundamental structural frequency, is exploited to achieve resonance over a range of flow velocities, thus increasing the velocity “bandwidth” of the devices. Simulations are run for different characteristic dimensions or shapes for the bluff body to study the strength and nature of vortex shedding in the presence of vibrating beam sections. The results of parameter variation for the design configuration is presented and discussed with regard to broadband wind energy harvesting.