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Using the constant properties model for accurate performance estimation of thermoelectric generator elements

Ponnusamy, Prasanna and de Boor, Johannes and Müller, Eckhard (2020) Using the constant properties model for accurate performance estimation of thermoelectric generator elements. Applied Energy, 262 (114587). Elsevier. doi: 10.1016/j.apenergy.2020.114587. ISSN 0306-2619.

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Thermoelectric devices convert thermal energy directly into electrical energy or vice versa. Analytically, the performance (efficiency and power output) of a thermoelectric generator can be quickly estimated using a Constant Properties Model (CPM) suggested by Ioffe. However, material properties in general are temperature dependent and the CPM can yield meaningful estimates only if the constant values of the TE properties used in the formulations are physically appropriate. In this study, a comparison of different averaging modes shows that a combination of integral averaging over the temperature scale for the Seebeck coefficient and spatial averages for the electrical and thermal resistivities proves to be the best among the considered approximations to represent the constant property values. However, averaging spatially requires the knowledge of the exact temperature distribution along the length of the thermoelectric leg (temperature profile), which is usually obtained by Finite Element Method (FEM) calculations. Since FEM is costly and time consuming, a fast and easy way of obtaining a well approximated self-consistent temperature profile is used in this study. The relevance, magnitude and the physical origin of the non-linearity of the temperature profile are visualised by separately plotting the individual contributions to the bending of the temperature profile (Joule, Thomson and Fourier heat contributions). On analyzing the temperature profiles for different highly efficient thermoelectric materials, it is found that the non-constancy of the temperature dependence of the thermal conductivity significantly contributes to the deflection of real temperature profiles from a linear one. This mainly explains the considerable discrepancy of CPM results from exact calculations whereas, so far, the neglect of Thomson heat has been assumed to be the main source of discrepancy and several models with Thomson correction factors have been proposed. With our current view, such models cannot completely remove the discrepancy to CPM unless the T profile is taken into account and can lead to unpredictable error for different material cases and temperatures.

Item URL in elib:https://elib.dlr.de/137188/
Document Type:Article
Title:Using the constant properties model for accurate performance estimation of thermoelectric generator elements
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:15 March 2020
Journal or Publication Title:Applied Energy
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1016/j.apenergy.2020.114587
Keywords:TEG performance; Device modeling; Temperature profile; Constant properties model; Fourier heat; Thomson heat
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Space System Technology
DLR - Research area:Raumfahrt
DLR - Program:R SY - Space System Technology
DLR - Research theme (Project):R - Systemtechnologien (old)
Location: Köln-Porz
Institutes and Institutions:Institute of Materials Research > Thermoelectric Materials and Systems
Deposited By: Frank, Adina
Deposited On:06 Nov 2020 10:35
Last Modified:06 Nov 2020 10:35

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