Analysis of Thermal Performance of Bimorph Piezoelectric Energy Harvesters

Abstract

Abstract Temperature gradients haven't been discussed much in the past, but these harvesting systems might be exposed to them. Temperature changes will affect the shape of the piezoelectric layers, so in order to bring the study conditions of these harvesters closer to the real conditions, the effect of temperature gradient should be investigated. The proposed method employs a clamped beam with a three-layer configuration. Two layers of PZT-5H piezoelectric material and a middle layer of aluminum material are used. The base vibrations applied to the harvester beam and the temperature difference between the layers of the harvester will cause mechanical stress in the piezoelectric layers. With the analytical modeling of the governing structural equations and the use of Ohm's and Gauss's laws, as well as considering the temperature difference of the harvester beam surfaces and assuming constant heat transfer without a heat source, coupled mechanical-electrical-thermal differential equations based on Euler-Bernoulli's assumptions are extracted. The results for two symmetric and asymmetric modes have been presented in this work, and temperature changes have been modeled. The results indicate that the best case for harvesting energy is one where the thickness of the piezoelectric layers is twice that of the homogeneous layer, and the best connection is also a series connection. The highest harvested power density corresponds to 70°C.