Design of nano-structured micro-thermoelectric generator: Load resistance and inflections in the efficiency

Abstract

In recent years the interest for the harvest of energy with micro thermoelectric generators (μTEG) has increased, due to its advantages compared to technologies that use fossil fuels. There are three ways to improve the performance of the device, by modifying its structure, type of material and operation control. In this study, the role of the load resistance RL on the performance of a μTEG with nanostructured materials is investigated. The interaction of the load resistance with the thermoelements exhibits interesting features, arising from the coupling of the temperature-dependent electrical and thermal transport properties at different temperature ranges and the architecture of nanostructured thermoelectric materials. This coupling results in inflections on the efficiency, i.e., maximum and minimum values of the efficiency at higher temperatures, 600-900 K.We show the explicit dependence of the performance of the μTEG in terms of the load resistance and discuss the underlying physics. The unusual features of the efficiency of nanostructured thermoelectric materials are a result of the behavior of the power factor and the nonequilibrium properties of the system. We also analyze the effect of the geometric shape of the thermoelements on the device. We determine the performance of the μTEG, evaluating the generation power and its efficiency. The results show that the efficiency of the device can decrease or increase depending on the value of RL, while the power decreases with an increase of the load resistance.