Energy harvesting using an array of multifunctional resonators

Energy harvesting from structural vibrations using an array of multifunctional resonators based on the theory of locally resonant materials is demonstrated. Such locally resonant structures exhibit a stop band for elastic wave propagation. The band gap frequency range depends on the local resonance frequency of the microstructure. One method to realize this is through the use of an array of embedded resonators where the external work done is stored as kinetic energy of the internal mass when the forcing frequency is close to the local resonance frequency. This mechanism can be used to harvest energy by converting the kinetic energy into electrical energy, thus bestowing a multifunctional utility to the structure. We use a spring-loaded magnet enclosed in a capped poly(methyl methacrylate) tube equipped with copper coils to create a unit cell that acts both as a resonator and as a linear generator. Experiments on a serial array of seven unit cells exhibit a band gap between 146.5 (local resonance frequency) and 171 Hz with a peak voltage generation of 3.03 V at steady state. The continuous effective power generated by a single unit cell across a 1-Ω load resistor is 36 mW, indicating the feasibility of constructing vibration isolation structures that can power simple electronic and microelectromechanical systems devices. The applicability of using the device as a transducer to measure the local resonance frequency and the global resonance frequency of the structure is also discussed.