Continuum Theory and Modeling of Thermoelectric Elements E-Book

• Herausgeber: Wiley-VCH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 602

Veröffentlichungsjahr: 2015

Beschreibung

Sound knowledge of the latest research results in the thermodynamics and design of thermoelectric devices, providing a solid foundation for thermoelectric element and module design in the technical development process and thus serving as an indispensable tool for any application development. The text is aimed mainly at the project developer in the field of thermoelectric technology, both in academia and industry, as well as at graduate and advanced undergraduate students. Some core sections address the specialist in the field of thermoelectric energy conversion, providing detailed discussion of key points with regard to optimization. The international team of authors with experience in thermoelectrics research represents such institutes as EnsiCaen Université de Paris, JPL, CalTech, and the German Aerospace Center.

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Guide

Table of Contents

Preface

Begin Reading

List of Illustrations

Chapter 1: Thermodynamics and Thermoelectricity

Figure 1.1 Two branches of physics combined.

Figure 1.2 Schematics of Seebeck's classical experiment.

Figure 1.3 Schematics for the Peltier effect.

Figure 1.4 Schematics of the Thomson effect.

Figure 1.5 The name givers of galvanomagnetic and thermomagnetic effects. In addition, Albert Freiherr von Ettingshausen (1850–1932) and Sylvestre Anatole Leduc (1856–1937) have to be mentioned.

Figure 1.6 Schematics of the different effects: (a) transversal effects, (b) longitudinal effects in a transverse field, and (c) longitudinal effects in a longitudinal field (adapted from Figure 154–156 in Ref. [76], pp. 311–312]).

Figure 1.7 Transversal thermogalvanomagnetic effects. The coefficients are positive if the effects have the same directions as shown in the schematics (adapted from Ref. [152], Figure 4-1, p. 83]).

Figure 1.8 Effects and their causes: Four galvanomagnetic and thermomagnetic effects (require a magnetic field) and two TE effects and their correlations (adapted from Ref. [229], p. 126]).

Figure 1.9 Galvanomagnetic and thermomagnetic effects (adapted from Ref. [217], Figure 9.66, p. 846]).

Figure 1.10 Carnot engine.

Figure 1.11 Schematic of a thermoelectric cell with a charged gas.

Figure 1.12 Schematic view of the basic entropy per carrier calculation.

Figure 1.13 Dependence of the chemical potential on the applied temperature as calculated within a parabolic two-band semiconductor model without approximation [solid lines, using Eq. (1.34) and within the Sommerfeld approximation [dotted lines, using Eq. (1.33). The temperature-dependent chemical potential is calculated for three different charge carrier concentrations. An incomplete description within the Sommerfeld approximation can be clearly seen for charge carrier concentrations below . For the sake of clarity, the effective masses of the conduction band edge and valence band edge are assumed to be identical (). The band gap (light gray shaded area) is chosen to be 100 meV.

Figure 1.14 Thermodynamic system: (a), reversible; (b) fully dissipative, (c) reversible in parallel with a pure leakage. The latter case obtains a correct model of the thermodynamic fluid and its convective contribution (), and the leakages, lattice and conductive contribution of the fluid ().

Figure 1.15 Comparison between steam and thermoelectric engine.

Figure 1.16 Thermoelectric applications: (a) thermogenerator (TEG), (b) TE cooler (TEC), (c) TE heater (TEH), see Figure 1.18 for details.

Figure 1.17 plot versus for three different values of . Three different modes appear: (a) TEH mode, (b) traditional TEC mode, (c) TEG mode. The optimal working conditions are also given.

Figure 1.18 Current–voltage response. TEH: (a), Regulation: (b), TEG: (c), TEC: (d).

Chapter 2: Continuum Theory of TE Elements

Figure 2.1 Unified 1D model of a thermoelectric element: lower temperature profile: cooling operation (= TEC with ); upper temperature profile: thermoelectric generator (= TEG with ). Bowing of the profile is indicated qualitatively. Typically, the bowing in the TEG case is weak due to relatively lower current in efficient operation, compared to the TEC. The arrows for and indicate the actual gradient and flow direction of positive magnitude. Analytically all vectors are counted positive in -direction, whereas the magnitude of the flow vectors with left-headed arrows adopts negative numerical values in the 1D formulae.

Figure 2.2 Single element device consisting of one thermoelectric leg. The three working modes are: a) TEG, b) Cooler, c) Heater.

Figure 2.3 Contributions in a TEG (CPM).

Figure 2.4 Performance parameters of a TEG in dependence on the load ratio . (a) Output voltage; (b) Output current; (c) Output power.

Figure 2.5 The efficiency of a TEG in dependence on the load ratio. and results in a temperature difference of , a Carnot efficiency , and an average temperature . The numerical example shown in the graph is for ().

Figure 2.6 Contributions in a TEC (CPM).

Figure 2.7 Performance of a TEG element in dependence on the electrical current density for the variation of and . Maximum values are shown with large dots. As there are two optimum current densities, the small dots represent the performance value for the “other” optimum current density, that is, or , respectively. The dashed and dotted–dashed lines serve as guidelines for the corresponding values. (a) Power output density – variation of ; (b) Power output density – variation of ; (c) Efficiency – variation of ; (d) Efficiency – variation of .