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Soufiane El Oualid

Bio: Soufiane El Oualid is an academic researcher from University of Lorraine. The author has contributed to research in topics: Thermoelectric effect & Thermoelectric materials. The author has an hindex of 3, co-authored 4 publications receiving 15 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, an innovative flexible thermoelectric micro-generators (μ-TEGs) design based on bismuth telluride thin films is presented. And the experimental results show that an output power of 5.5 μW per thermocouple can be generated under a temperature difference of only 5 K, in excellent agreement with predictions based on three-dimensional finite element analyses.
Abstract: The ever-increasing number of connected objects requires novel ways to power them and make them fully autonomous. In this context, photovoltaic, piezoelectric or thermoelectric energy-harvesting technologies show great promises as they make possible the conversion of solar radiation, motion or thermal energy into useful electricity for charging micro-batteries for instance. Thermoelectric micro-generators (μ-TEGs) exhibit several key benefits, making them prime candidates for harvesting any temperature difference between their two exchange surfaces. However, their output power critically depends on the design of the μ-TEG, the minimization of the detrimental influence of the contact resistances and on the coupling of the μ-TEG with the heat source and heat sink. Here, we theoretically and experimentally demonstrate how these inherent difficulties can be mitigated using an innovative flexible μ-TEG design based on bismuth telluride thin films. Our experimental results show that an output power of 5.5 μW per thermocouple can be generated under a temperature difference of only 5 K, in excellent agreement with predictions based on three-dimensional finite element analyses. These remarkable results rank our μ-TEG among the best micro-generators currently available.

30 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used skutterudites as a proof-of-principle for the construction of TEGs with 1 mm-thick metallic layers and achieved a power-density of 7.6 W cm−2 under temperature differences varying between 450 and 630 K.
Abstract: Thermoelectric generators (TEGs) offer a versatile solution to convert low-grade heat into useful electrical power. While reducing the length of the active thermoelectric legs provides an efficient strategy to increase the maximum output power density pmax, both the high electrical contact resistances and thermomechanical stresses are two central issues that have so far prevented a strong reduction in the volume of thermoelectric materials integrated. Here, it is demonstrated that these barriers can be lifted by using a nonconventional architecture of the legs which involves inserting thick metallic layers. Using skutterudites as a proof-of-principle, several single-couple and multi-couple TEGs with skutterudite layers of only 1 mm are fabricated, yielding record pmax ranging from 3.4 up to 7.6 W cm−2 under temperature differences varying between 450 and 630 K. The highest pmax achieved corresponds to a 60-fold increase per unit volume of skutterudites compared to 1 cm long legs. This work establishes thick metallic layers as a robust strategy through which high power density TEGs may be developed.

23 citations

Journal ArticleDOI
TL;DR: 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.

13 citations

Journal ArticleDOI
TL;DR: In this paper, the half-skeleton structure of thermoelectric legs has been used for the mass manufacturing of a mass-manufactured version of thermistors with an average power output of 0.37 W/cm2.

9 citations

Journal ArticleDOI
TL;DR: In this article , the influence of the insertion bias on the thermal conductivity of Mo-based cluster compounds was investigated, and it was shown that insertion bias can influence the thermoelectric properties of cluster compounds.
Abstract: Mo-based cluster compounds form a large class of materials with interesting thermoelectric properties primarily due to their very low lattice thermal conductivity. Here, we investigate the influence of the insertion...

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Journal ArticleDOI
TL;DR: In this article, an analytic approach based on a force-flux formalism was proposed to derive the conditions that permit maximization of both efficiency and power production of a TEG dissipatively coupled to heat reservoirs.
Abstract: We study how maximum output power can be obtained from a thermoelectric generator(TEG) with nonideal heat exchangers. We demonstrate with an analytic approach based on a force-flux formalism that the sole improvement of the intrinsic characteristics of thermoelectric modules including the enhancement of the figure of merit is of limited interest: the constraints imposed by the working conditions of the TEG must be considered on the same footing. Introducing an effective thermal conductance we derive the conditions which permit maximization of both efficiency and power production of the TEG dissipatively coupled to heat reservoirs. Thermal impedance matching must be accounted for as well as electrical impedance matching in order to maximize the output power. Our calculations also show that the thermal impedance does not only depend on the thermal conductivity at zero electrical current: it also depends on the TEG figure of merit. Our analysis thus yields both electrical and thermal conditions permitting optimal use of a thermoelectric generator.

96 citations

Journal ArticleDOI

37 citations

Journal ArticleDOI
TL;DR: In this article, the authors showed the simultaneous enhancement of electrical transport and reduction of phonon propagation in p-type PbTe codoped with Tl and Na and demonstrated that the combination of impurity resonance scattering and crystal lattice softening can be a breakthrough concept for advancing thermoelectrics.
Abstract: In this work, we show the simultaneous enhancement of electrical transport and reduction of phonon propagation in p-type PbTe codoped with Tl and Na. The effective use of advanced electronic structure engineering improves the thermoelectric power factor S2σ over the temperature range from 300 to 825 K. A rise in the Seebeck coefficient S was obtained due to the enhanced effective mass m*, coming from the Tl resonance state in PbTe. Due to the presence of additional carriers brought by Na codoping, electrical conductivity became significantly improved. Furthermore, Tl and Na impurities induced crystal lattice softening, remarkably reducing lattice thermal conductivity, which was confirmed by a measured low speed of sound vm and high internal strain CeXRD. Eventually, the combination of both the attuned electronic structure and the lattice softening effects led to a very high ZT value of up to ∼2.1 for the Pb1-x-yTlxNayTe samples. The estimated energy conversion efficiency shows the extraordinary value of 15.4% (Tc = 300 K, Th = 825 K), due to the significantly improved average thermoelectric figure of merit ZTave = 1.05. This work demonstrates that the combination of impurity resonance scattering and crystal lattice softening can be a breakthrough concept for advancing thermoelectrics.

26 citations

Journal ArticleDOI
TL;DR: In this article , high-TE-performance Bi2Te3-based Peltier devices utilizing thermoelectric (TE) materials are used for precise temperature management in 5G and next-generation communication technologies.
Abstract: Peltier devices utilizing thermoelectric (TE) materials are expected to be used for precise temperature management in 5G and next-generation communication technologies. This demand has driven efforts to develop high-TE-performance Bi2Te3-based...

26 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used skutterudites as a proof-of-principle for the construction of TEGs with 1 mm-thick metallic layers and achieved a power-density of 7.6 W cm−2 under temperature differences varying between 450 and 630 K.
Abstract: Thermoelectric generators (TEGs) offer a versatile solution to convert low-grade heat into useful electrical power. While reducing the length of the active thermoelectric legs provides an efficient strategy to increase the maximum output power density pmax, both the high electrical contact resistances and thermomechanical stresses are two central issues that have so far prevented a strong reduction in the volume of thermoelectric materials integrated. Here, it is demonstrated that these barriers can be lifted by using a nonconventional architecture of the legs which involves inserting thick metallic layers. Using skutterudites as a proof-of-principle, several single-couple and multi-couple TEGs with skutterudite layers of only 1 mm are fabricated, yielding record pmax ranging from 3.4 up to 7.6 W cm−2 under temperature differences varying between 450 and 630 K. The highest pmax achieved corresponds to a 60-fold increase per unit volume of skutterudites compared to 1 cm long legs. This work establishes thick metallic layers as a robust strategy through which high power density TEGs may be developed.

23 citations