Role of Structures on Thermal Conductivity in Thermoelectric Materials

Godart, C.; Gonçalves, A.P.; Lopes, Elsa B.; Villeroy, Benjamin

doi:10.1007/978-90-481-2892-1_2

“…One can engineer band gaps in the phonon spectrum by drilling regularly spaced holes in the material to make a phononic crystal (see for example [71,72]). One can make a highly disordered material known as a phonon glass or at least sufficiently disorder to reduce the phonon conduction by a significant factor (see for example [73][74][75]). A strategy which makes particular sense for the refrigeration of micronsized samples to temperatures below that of current cryogenics is to suspend the sample being refrigerated.…”

Section: Heat Carried By Phonons and Photonsmentioning

confidence: 99%

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

Benenti,

Casati,

Saito

et al. 2016

Preprint

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In recent years, the study of heat to work conversion has been re-invigorated by nanotechnology. Steady-state devices do this conversion without any macroscopic moving parts, through steady-state flows of microscopic particles such as electrons, photons, phonons, etc. This review aims to introduce some of the theories used to describe these steady-state flows in a variety of mesoscopic or nanoscale systems. These theories are introduced in the context of idealized machines which convert heat into electrical power (heat-engines) or convert electrical power into a heat flow (refrigerators). In this sense, the machines could be categorized as thermoelectrics, although this should be understood to include photovoltaics when the heat source is the sun. As quantum mechanics is important for most such machines, they fall into the field of quantum thermodynamics. In many cases, the machines we consider have few degrees of freedom, however the reservoirs of heat and work that they interact with are assumed to be macroscopic. This review discusses different theories which can take into account different aspects of mesoscopic and nanoscale physics, such as coherent quantum transport, magnetic-field induced effects (including topological ones such as the quantum Hall effect), and single electron charging effects. It discusses the efficiency of thermoelectric conversion, and the thermoelectric figure of merit. More specifically, the theories presented are (i) linear response theory with or without magnetic fields, (ii) Landauer scattering theory in the linear response regime and far from equilibrium, (iii) Green-Kubo formula for strongly interacting systems within the linear response regime, (iv) rate equation analysis for small quantum machines with or without interaction effects, (v) stochastic thermodynamic for fluctuating small systems. In all cases, we place particular emphasis on the fundamental questions about the bounds on ideal machines. Can magnetic-fields change the bounds on power or efficiency? What is the relationship between quantum theories of transport and the laws of thermodynamics? Does quantum mechanics place fundamental bounds on heat to work conversion which are absent in the thermodynamics of classical systems?

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“…From the beginning of the 1990s a renewal of interest in thermoelectric (TE) appeared, due to environmental concern with refrigerant gas and greenhouse effects, as well as the need to develop alternative energy sources [14].…”

Section: Introductionmentioning

confidence: 99%

Enhanced Efficiency of Thermoelectric Generator by Optimizing Mechanical and Electrical Structures

Chen

¹

,

Li

²

,

Liu

³

et al. 2017

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Much attention has been paid to the application of low temperature thermal resources, especially for power generation in recent years. Most of the current commercialized thermal (including geothermal) power-generation technologies convert thermal energy to electric energy indirectly, that is, making mechanical work before producing electricity. Technology using a thermoelectric generator (TEG), however, can directly transform thermal energy into electricity through the Seebeck effect. TEG technology has many advantages such as compactness, quietness, and reliability because there are no moving parts. One of the biggest disadvantages of TEGs is the low efficiency from thermal to electric energy. For this reason, we redesigned and modified our previous 1 KW (at a temperature difference of around 120 • C) TEG system. The output power of the system was improved significantly, about 34.6% greater; the instantaneous efficiency of the TEG system could reach about 6.5%. Laboratory experiments have been conducted to measure the output power at different conditions: different connection modes between TEG modules, different mechanical structures, and different temperature differences between hot and cold sides. The TEG apparatus has been tested and the data have been presented. This kind of TEG power system can be applied in many thermal and geothermal sites with low temperature resources, including oil fields where fossil and geothermal energies are coproduced.

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“…One can engineer band gaps in the phonon spectrum by drilling regularly spaced holes in the material to make a phononic crystal (see for example [71,72]). One can make a highly disordered material known as a phonon glass or at least sufficiently disorder to reduce the phonon conduction by a significant factor (see for example [73][74][75]). A strategy which makes particular sense for the refrigeration of micronsized samples to temperatures below that of current cryogenics is to suspend the sample being refrigerated.…”

Section: Heat Carried By Phonons and Photonsmentioning

confidence: 99%

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

Benenti

¹

,

Casati

²

,

Saito

³

et al. 2017

View full text Add to dashboard Cite

In recent years, the study of heat to work conversion has been re-invigorated by nanotechnology. Steady-state devices do this conversion without any macroscopic moving parts, through steady-state flows of microscopic particles such as electrons, photons, phonons, etc. This review aims to introduce some of the theories used to describe these steady-state flows in a variety of mesoscopic or nanoscale systems. These theories are introduced in the context of idealized machines which convert heat into electrical power (heat-engines) or convert electrical power into a heat flow (refrigerators). In this sense, the machines could be categorized as thermoelectrics, although this should be understood to include photovoltaics when the heat source is the sun. As quantum mechanics is important for most such machines, they fall into the field of quantum thermodynamics. In many cases, the machines we consider have few degrees of freedom, however the reservoirs of heat and work that they interact with are assumed to be macroscopic. This review discusses different theories which can take into account different aspects of mesoscopic and nanoscale physics, such as coherent quantum transport, magnetic-field induced effects (including topological ones such as the quantum Hall effect), and single electron charging effects. It discusses the efficiency of thermoelectric conversion, and the thermoelectric figure of merit. More specifically, the theories presented are (i) linear response theory with or without magnetic fields, (ii) Landauer scattering theory in the linear response regime and far from equilibrium, (iii) Green-Kubo formula for strongly interacting systems within the linear response regime, (iv) rate equation analysis for small quantum machines with or without interaction effects, (v) stochastic thermodynamic for fluctuating small systems. In all cases, we place particular emphasis on the fundamental questions about the bounds on ideal machines. Can magnetic-fields change the bounds on power or efficiency? What is the relationship between quantum theories of transport and the laws of thermodynamics? Does quantum mechanics place fundamental bounds on heat to work conversion which are absent in the thermodynamics of classical systems?

show abstract

Role of Structures on Thermal Conductivity in Thermoelectric Materials

Cited by 11 publications

References 85 publications

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

Enhanced Efficiency of Thermoelectric Generator by Optimizing Mechanical and Electrical Structures

Fundamental aspects of steady-state conversion of heat to work at the nanoscale

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