Investigation of a Nonlinear Energy Harvester

The use of nonlinear architectures for energy harvesting can significantly improve the efficiency of the conversion mechanism, as respect to the use of linear devices, especially when the mechanical energy is distributed over a wide frequency bandwidth. This is the case of energy harvesting form wideband vibrations. In this paper, performances of a piezoelectric energy harvester exploiting a snap-through buckling configuration are investigated. The device is supposed to switch between its stable states, where two piezoelectric transducers are positioned to implement the mechanical-to-electric conversion mechanism. A simple theoretical two-state model of the device is presented along with a complete experimental characterization aimed at investigating the mechanical and electrical behaviors of the device. The device is demonstrated to be capable of scavenging energy from vibration sources in the range 0.5-5 Hz, but could be exploited up to 15 Hz with an acceptable loss of efficiency. The bandwidth of the device is compatible with applications where the vibrations occur at low frequencies, e.g., in the case of a running human. In this paper, we demonstrate the viability of our setup for harvesting energy from mechanical vibrations. The device is seen to generate power up to 155 mu W at 5 Hz; the power is sufficient to operate a standard wireless sensor node. The conversion efficiency of the harvester in the range 0.5-5 Hz is from 13% up to 18% with an average of 15%.