Energy Harvesting Utilizing Single Crystal PMN-PT Material and Application to a Self-Powered Accelerometer

This study investigates the performance of an energy harvester (EH) utilizing a single crystal lead magnesium niobate-lead titanate (PMN-PT) material via analysis and experiment. The EH, intended to convert mechanical energy at a harmonic frequency such as from a fixed revolutions per minute (RPM) rotating machine, was composed of a cantilever beam having a single crystal PMN-PT patch, a tip mass, a rectifier, and an electric load. The fundamental frequency of the EH was finely adjusted via moving a tip mass spanwise. The analysis was used to select an optimal EH configuration based on a weight constraint (less than 200 g) and a narrow band frequency range (nominally 60 Hz). The analysis and performance were validated experimentally for different excitation levels. The harvested dc power was measured for low acceleration levels of 0.05–0.2 g (where $1g=9.81m/s2$⁠) typical of rotating machinery. The maximum dc power generated was 19 mW for an excitation of 0.2 g. The measured power density (i.e., maximum dc power over total device volume) and measured specific power (i.e., maximum dc power over total device mass) of the energy harvester were 0.73 mW/cc and 0.096 mW/g, respectively. The EH developed in this study was compared with other configurations and types via metrics of mean square acceleration weighted power (MSAP) and MSAP density. Charging performance of the single crystal PMN-PT based EH was evaluated by recharging a battery. In addition, the effect of the capacitance of the rectifier circuit on charging time was also investigated. Finally, the EH was also used to drive an accelerometer using only energy that was harvested from ambient vibration. The accelerometer was continuously and successfully operated when the persistent excitation level exceeded 0.1 g.