Study on acoustic energy harvester using a Helmholtz resonator and a cantilever piezoelectric transducer

Aiming at harvesting acoustic energy widely distributed in the environment, an acoustic energy harvester using a Helmholtz resonator (HR) and a cantilever piezoelectric transducer is proposed. The HR amplifies incident sound pressure, the interior sound pressure of HR causes the elastic thin wall to vibrate, the piezoelectric transducer converts vibrational energy to electric energy. A theoretical model of the cubical HR with the elastic wall based on equivalent lumped parameter assumption is developed. The acoustic-mechano-electric performance of the harvester is analyzed by combining the lumped parameter model with the electromechanical characteristics of the piezoelectric transducer, and the influences of sound pressure, acoustic frequencies and load impedances on the output power are investigated. The study results provide a method for optimization design and engineering applications of such harvesters. In the experiment, a sound source emits acoustic energy through an acoustic waveguide, and a prototype produces maximum output power of 240μW for a sound pressure level of the entrance of the HR at 94 dB. This harvester can be applied in not only acoustic self-powered devices but also the active energy supply for low-power electronic devices at long distance.