Optimization of piezoelectric devices for energy harvesting

The field of the energy harvesting experienced a constant growth in the last years, due to the possibility of developing standing-alone wireless portable devices with extended life. In this context, piezoelectric materials appear to be particularly effective for the development of harvesters able to scavenge energy from ambient vibrations. In this paper a piezoactuated cantilever beam used for energy harvesting purposes is considered, extracting energy from a vibration source applied at the clamped boundary. An electric circuit containing a resistor and an inductor, connected to the piezoelectric electrodes, is optimized for extracting the maximum electric power for any frequency of the vibration source. The inductance is used to compensate the presence of a mistuning between the vibration source and the cantilever resonance frequency. Proposed analysis shows that a single inductance is effective only when the harvester can be treated essentially as a single-degree-of-freedom structure. For harvesters with multiple degrees-offreedom a single inductance is not sufficient to provide broadband functionality to the device, and the use of a multiresonant electric circuit appears to be necessary.