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Discrepancy between Constant Properties Model and Temperature-Dependent Material Properties for Performance Estimation of Thermoelectric Generators

Ponnusamy, Prasanna and de Boor, Johannes and Müller, Eckhard (2020) Discrepancy between Constant Properties Model and Temperature-Dependent Material Properties for Performance Estimation of Thermoelectric Generators. Entropy, 22 (1128). Multidisciplinary Digital Publishing Institute (MDPI). doi: 10.3390/e22101128. ISSN 1099-4300.

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Abstract

The efficiency of a thermoelectric (TE) generator for the conversion of thermal energy into electrical energy can be easily but roughly estimated using a constant properties model (CPM) developed by Ioffe. However, material properties are, in general, temperature (T)-dependent and the CPM yields meaningful estimates only if physically appropriate averages, i.e., spatial averages for thermal and electrical resistivities and the temperature average (TAv) for the Seebeck coefficient (α), are used. Even though the use of αTAv compensates for the absence of Thomson heat in the CPM in the overall heat balance, we find that the CPM still overestimates performance (e.g., by up to 6% for PbTe) for many materials. The deviation originates from an asymmetric distribution of internally released Joule heat to either side of the TE leg and the distribution of internally released Thomson heat between the hot and cold side. The Thomson heat distribution differs from a complete compensation of the corresponding Peltier heat balance in the CPM. Both effects are estimated quantitatively here, showing that both may reach the same order of magnitude, but which one dominates varies from case to case, depending on the specific temperature characteristics of the thermoelectric properties. The role of the Thomson heat distribution is illustrated by a discussion of the transport entropy flow based on the α(T) plot. The changes in the lateral distribution of the internal heat lead to a difference in the heat input, the optimum current and thus of the efficiency of the CPM compared to the real case, while the estimate of generated power at maximum efficiency remains less affected as it is bound to the deviation of the optimum current, which is mostly <1%. This deviation can be corrected to a large extent by estimating the lateral Thomson heat distribution and the asymmetry of the Joule heat distribution. A simple guiding rule for the former is found

Item URL in elib:https://elib.dlr.de/137150/
Document Type:Article
Title:Discrepancy between Constant Properties Model and Temperature-Dependent Material Properties for Performance Estimation of Thermoelectric Generators
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Ponnusamy, Prasannagerman aerospace center, institute of materials research, köln, germanyUNSPECIFIED
de Boor, JohannesGerman aerospace center, institute of materials research, köln, germanyhttps://orcid.org/0000-0002-1868-3167
Müller, EckhardGerman aerospace center, Institute of materials research, Köln, Germany and Institute for inorganic and analytical chemistry, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 58, 35392 Gießen, GermanyUNSPECIFIED
Date:4 October 2020
Journal or Publication Title:Entropy
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:22
DOI :10.3390/e22101128
Publisher:Multidisciplinary Digital Publishing Institute (MDPI)
ISSN:1099-4300
Status:Published
Keywords:TEG performance; device modeling; temperature profile; constant properties model; Fourier heat; Thomson heat; Joule heat
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Transport
HGF - Program Themes:Road Transport
DLR - Research area:Transport
DLR - Program:V ST Straßenverkehr
DLR - Research theme (Project):V - NGC Antriebssystem und Energiemanagement
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > Thermoelectric Materials and Systems
Deposited By: Frank, Adina
Deposited On:06 Nov 2020 09:43
Last Modified:06 Nov 2020 09:43

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