Piezoelectric Energy Harvesting under High Pre-Stressed Cyclic Vibrations

The performance of the cymbal transducer under ac force of 70 N with a pre-stress load of 67 N at 100 Hz frequency is reported. At this frequency and force level, 52 mW power was generated from a cymbal measured across a 400 kOhm resistor. The ceramic diameter was fixed at 29 mm and various thicknesses were tested to optimise the performance. The PZT ceramic of 1 mm thickness provided the highest power output with 0.4 mm endcap. In order to accommodate such high dynamic pressure, the transducer and cap materials were modified and the higher piezoelectric voltage constant ceramic provided the higher output power. Electrical output power as a function of applied ac stress magnitude was also computed using FEM analysis and the results were functionally coherent with experiment. The feasibility of using piezoelectric transducers for harvesting energy from high magnitude vibration sources such as automobiles was clearly shown.