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Ponnusamy P, de Boor J, Müller E. Discrepancy between Constant Properties Model and Temperature-Dependent Material Properties for Performance Estimation of Thermoelectric Generators. Entropy (Basel). 2020;22(10)doi: 10.3390/e22101128.
Ponnusamy, P., de Boor, J., & Müller, E. (2020). Discrepancy between Constant Properties Model and Temperature-Dependent Material Properties for Performance Estimation of Thermoelectric Generators. Entropy (Basel, Switzerland), 22(10), . https://doi.org/10.3390/e22101128
Ponnusamy, Prasanna, et al. "Discrepancy between Constant Properties Model and Temperature-Dependent Material Properties for Performance Estimation of Thermoelectric Generators." Entropy (Basel, Switzerland) vol. 22,10 (2020). doi: https://doi.org/10.3390/e22101128
Ponnusamy P, de Boor J, Müller E. Discrepancy between Constant Properties Model and Temperature-Dependent Material Properties for Performance Estimation of Thermoelectric Generators. Entropy (Basel). 2020 Oct 04;22(10). doi: 10.3390/e22101128. PMID: 33286897; PMCID: PMC7597267.
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Entropy (Basel). 2020 Oct 04;22(10). doi: 10.3390/e22101128.

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

Entropy (Basel, Switzerland)

Prasanna Ponnusamy, Johannes de Boor, Eckhard Müller

Affiliations

  1. Institute of Materials Research, German Aerospace Center (DLR), D-51170 Köln, Germany.
  2. Institute of Inorganic and Analytical Chemistry, Justus Liebig University Gießen, D-35392 Gießen, Germany.

PMID: 33286897 PMCID: PMC7597267 DOI: 10.3390/e22101128

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.

Keywords: Fourier heat; Joule heat; TEG performance; Thomson heat; constant properties model; device modeling; temperature profile

References

  1. Nature. 2014 Apr 17;508(7496):373-7 - PubMed
  2. Nat Commun. 2014 Jul 29;5:4515 - PubMed

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