Abstract
In recent years the interest for the harvest of energy with micro thermoelectric generators (TEG) 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 on the performance of a TEG 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 TEG 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 TEG, 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 , while the power decreases with an increase of the load resistance.
Highlights
The thermoelectric generating devices are solid-state devices with significant advantages, since it is an energy harvester without either moving parts or the need for continuous maintenance, making it a sustainable and environmentally friendly alternative
The maximum output power was obtained with R L = 0.24 Ω for the rectangular shape and R L = 0.28 Ω for the trapezoidal shape. These results show the effect of the geometric shape of the thermoelements in the μTEG on the maximum efficiency and power with different values of load resistance
The interaction between μTEG and load resistance plays an important role in the optimization of a design, since it has been shown that its performance depends on the relationship between R L and its internal resistance
Summary
The thermoelectric generating devices are solid-state devices with significant advantages, since it is an energy harvester without either moving parts or the need for continuous maintenance, making it a sustainable and environmentally friendly alternative. The efficiency of the thermoelectric generators (TEG) is around 5 percent [1]. Many methods to increase the efficiency of thermoelectric devices focuses on the manipulation of materials to optimize the figure of merit (ZT). The approach is based on optimizing the materials by improving the power factor, that is, increasing the Seebeck coefficient without overshadowing the electrical conductivity. This can be done with the modification of the structure of the band by degeneration of many valleys, Entropy 2019, 21, 224; doi:10.3390/e21030224 www.mdpi.com/journal/entropy
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