Piezoelectric type acoustic energy harvester with a tapered Helmholtz cavity for improved performance

Abstract

This paper reports an improved acoustic energy harvester with a tapered Helmholtz cavity. The harvester consists of a bimorph piezoelectric composite plate and a Helmholtz resonator (HR) with a tapered cavity. The architecture, operational mechanism, fabrication, and characterization of the harvesters are described. The harvesters are tested under sinusoidal sound pressure levels (SPLs) inside a lab as well as random SPLs in a real ambient acoustical environment. When a harvester with a tapered HR and without proof mass attached to its piezoelectric plate is characterized at a sinusoidal SPL of 130 dB, a maximum power of 90.6 μW is delivered to 1 kΩ load. In comparison, a similar harvester with a cylindrical shape HR produced a maximum power of 51.4 μW under the similar acoustic conditions. It is found that 76.26% increase in power is achieved with the tapered cavity for the HR. Furthermore, due to the attachment of a proof mass (0.84 g) with the harvester, its power production capability is further increased by 103.3%, from 90.6 to 184.18 μW. Moreover, in a real environment, the maximum voltage amplitudes of about 260 and 280 mV are produced by the harvester when placed in the surrounding of a motorbike and domestic electric generator, respectively.