Comparison between MEMS and Meso Scale Piezoelectric Energy Harvesters

Abstract

Manufacture of piezoelectric energy harvesters typically assumes bulk piezoelectric material for the transducer until the reduction in size of the device prevents this. However when designing piezoelectric harvesters, the complete system must be taken into account including the transducer, power circuit, and battery, as these will impose restrictions on what can be achieved. Therefore a comparison between MEMS and meso-scale piezoelectric energy harvesting systems using a fully parametrised model is required. The comparison was restricted to a piezoelectric beam with a mass at the end connected to a single supply pre-biasing circuit to provide the optimal damping force and rectification. A buck converter was used to transfer extracted energy to a 1.5V battery. The results indicate that for devices with a volume side length less than 16.25 mm, no device using meso-scale properties can be made to resonant at 100 Hz or less due to the length and stiffness of the beam. Whereas above this limit, the voltage required to damp devices with MEMS scale properties causes a breakdown in the dielectric. We present a comparison of the theoretical limits of MEMS and meso-scale piezoelectric harvesters to provide design insight for future devices to maximise power generation.