Thermoelectric materials for space applications

TLDR: In this article, the authors review the knowledge acquired over the last years on several families of thermoelectric materials, the performances of which are close or even higher than those conventionally used in RTGs to date.

Abstract: Solid-state energy conversion through thermoelectric effects remains the technology of choice for space applications for which, their low energy conversion efficiency is largely outweighed by the reliability and technical requirements of the mission. Radioisotope thermoelectric generators (RTGs) enable the direct conversion of the heat released by nuclear fuel into the electrical power required to energize the scientific instruments. The optimization of the conversion efficiency is intimately connected to the performances of the thermoelectric materials integrated which are governed by the transport properties of these materials. Recent advances in the design of highly efficient thermoelectric materials raise interesting prospects to further enhance the performances of RTGs for future exploratory missions in the Solar system. Here, we briefly review the knowledge acquired over the last years on several families of thermoelectric materials, the performances of which are close or even higher than those conventionally used in RTGs to date. Issues that remain to be solved are further discussed.

Figures

Fig. 3. a) Schematic representation of the variations in the thermopower 𝛼 (in absolute value for n-type compounds) as a function of the carrier concentration 𝑛𝐻/𝑝𝐻 called the IoffePisarenko curve. For conventional impurities (solid blue curve), 𝛼 monotonically decreases with increasing the carrier concentration. For specific impurities inducing the formation of a resonant level, that is, a local distortion of the valence or conduction bands, a clear departure

Fig. 5. Temperature dependence of the dimensionless thermoelectric figure of merit ZT of selected novel families of a) n-type and b) p-type thermoelectric materials that have emerged over the last two decades [1,29-31,54-65].

Fig. 4. Temperature dependence of the dimensionless thermoelectric figure of merit ZT of various state-of-the-art n-type and p-type thermoelectric materials [1,45-52].

Fig. 8. Examples of Mo-X clusters (X = S, Se or Te) of various sizes. Several basic units Mo6X8X6 can be condensed to form longer chain-like clusters that are then arranged to form a three-dimensional framework. In the limit of infinite length, compounds Mo6X6 are obtained.

Full text

HAL Id: hal-03190535
https://hal.univ-lorraine.fr/hal-03190535
Submitted on 18 May 2021
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Thermoelectric materials for space applications
Christophe Candol, Souane El Oualid, Dorra Ibrahim, Shantanu Misra,
Oussama El Hamouli, Adèle Léon, Anne Dauscher, Philippe Masschelein,
Philippe Gall, Patrick Gougeon, et al.
To cite this version:
Christophe Candol, Souane El Oualid, Dorra Ibrahim, Shantanu Misra, Oussama El Hamouli, et
al.. Thermoelectric materials for space applications. CEAS Space Journal, Springer, 2021, 13 (3),
pp.325-340. �10.1007/s12567-021-00351-x�. �hal-03190535�

1
Thermoelectric materials for space applications
Christophe Candolfi
1,*
, Soufiane El Oualid
1
, Dorra Ibrahim
1
, Shantanu Misra
1
, Oussama El
Hamouli
1
, Adèle Léon
1
, Anne Dauscher
1
, Philippe Masschelein
1
, Philippe Gall
2
, Patrick
Gougeon
2
, Christopher Semprimoschnig
3,†
, Bertrand Lenoir
1,*
1
Institut Jean Lamour, UMR 7198 CNRS – Université de Lorraine, Campus ARTEM, 2 allée
André Guinier, BP 50840, 54011 Nancy, France
2
Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS – Université de Rennes 1 –
INSA de Rennes – Ecole Nationale Supérieure de Chimie de Rennes, 11 allée de Beaulieu, CS
50837, 35708 Rennes Cedex, France
3
European Space Agency, ESTEC, P.O. Box 299, Keplerlaan 1, 2200 AG Noordwijk, The
Netherlands
*
Corresponding Authors: christophe.candolfi@univ-lorraine.fr; bertrand.lenoir@uni v-
lorraine.fr
†
C. S. passed away in 2020
Abstract
Solid-state energy conversion through thermoelectric effects remains the technology of choice
for space applications for which, their low energy conversion efficiency is largely outweighed
by the reliability and technical requirements of the mission. Radioisotope thermoelectric
generators (RTGs) enables the direct conversion of the heat released by nuclear fuel into the
electrical power required to energize the scientific instruments. The optimization of the
conversion efficiency is intimately connected to the performances of the thermoelectric
Accepted manuscript

2
materials integrated which are governed by the transport properties of these materials. Recent
advances in the design of highly-efficient thermoelectric materials raise interesting prospects
to further enhance the performances of RTGs for future exploratory missions in the Solar
system. Here, we briefly review the knowledge acquired over the last years on several families
of thermoelectric materials, the performances of which are close or even higher than those
conventionally used in RTGs to date. Issues that remain to be solved are further discussed.
Keywords: Thermoelectric, RTG, Semiconductors, Space mission
Declarations
Funding
European Space Agency (ESA/ESTEC)
Conflicts of Interest
The authors declare no competing financial interest.
Availability of data and material
Not applicable
Code availability
Not applicable
Accepted manuscript

3
1. Introduction
Thermoelectric materials provide an elegant and versatile way to convert a temperature
difference into electrical power (Seebeck effect) or vice versa (Peltier effect) [1-3].
Thermoelectric generators (TEGs, see Fig. 1), in which these materials are integrated, possess
important advantages over other energy conversion technologies. In particular, the TEGs does
not exhibit any moving parts and are thus noise- and vibration-free during operation, conferring
high mechanical reliability with low maintenance levels and hence, long lifetime. These
properties make TEGs fully autonomous and particularly well-suited for operating in isolated
areas on Earth and in the extreme environments of space and other planetary surfaces. These
TEGs can be either scaled up or downsized, offering a high adaptability for a plethora of
applications ranging from waste-heat recovery in various industrial processes to the powering
of autonomous micro-sensors for Internet-of-things (IoT) applications [4-8].
Accepted manuscript

4
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b)
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Accepted manuscript

Frequently asked questions

Q1. What contributions have the authors mentioned in the paper "Thermoelectric materials for space applications" ?

In this paper, a thermoelectric generator with segmented legs is presented, where the n-and p-type legs are brazed on the metallic plates to ensure low electrical contact resistances.