Investigating the Characteristics of Helmholtz Resonator Energy Harvesting

Abstract

The objective of this thesis is to develop further understanding of the trends and behavior of Helmholtz energy harvesters, which operate by converting wind-driven pressure oscillations within a Helmholtz resonator into electricity through the deformation of a piezoelectric disk. Discrepancies found in earlier work done by Emile Oshima and Michael Rodriguez are investigated to better predict performance at the design level and improve power generation capabilities. Previous design procedures were unable to accurately predict the resonator frequency, which is necessary to maximize power generation from the harvester.

Modification of the harvester designed by Rodriguez resulted in a maximum power generation of 1.58 W/m^2 at a jet velocity of 4.4 m/s. The prototype designed with the new methodology reached a maximum of 2.13 W/m^2 at the same jet velocity. This is a 35% increase from the modified version of Rodriguez's harvester to the new one. Relative to the peak power density achieved by Rodriguez's investigations, the updated prototype showed a 163% increase. The design methodology successfully predicted the resonant frequency of the new prototype for certain cases, although prediction accuracy varied with circuit resistance. Initial conclusions point to the interactions between circuit resistance, piezoelectric rigidity, and the piezo's natural frequency as the causes for this discrepancy.