Acoustic-Based Electrodynamic Energy Harvester for Wireless Sensor Nodes Application

An electrodynamic harvester for scavenging acoustic energy is reported in this paper. The working principle, fabrication and characterization of the harvester are discussed. The developed harvester consists of an Helmholtz resonator, flexible membrane, moving magnets and a fixed wound coil. The harvester is characterized under acoustic energy at different sound pressure levels (SPL’s) and is subjected to both increasing frequency sweep (IFS) and decreasing frequency sweep (DFS). At resonance and under 120 dB SPL, the harvester produced a maximum load rms voltage of 315 mV at 66 Ω load resistance. The experimental results showed the maximum power delivered to load is 1503.4 μW at 120 dB SPL, that leads to a maximum power density of 191.4 μW/cm for the developed harvester. The energy harvester is also characterized in open air with a large speaker as an acoustic source. Moreover, the harvester generated a load voltage of about 30 mV when subjected to the acoustical noise of a household electrical generator.