Search

The effect of Thomson heating on semiconductor medium is studied. Analytical discussions in the presence of thermoelectricity and magnetic field, in the context of photothermal transport process, are made. The interactions between plasma, thermoelectric, magnetic and elastic waves are taken into consideration. The governing equations are investigated in two-dimensional deformations of a homogenous, isotropic medium. The density of charge is taken only as a function of time of the induced electric current. The normal mode technique is used to obtain the physical quantities field under investigation. Some electro-mechanical loads and thermal effect through recombination process are applied at the free surface of semiconductor elastic medium. The distributions of physical fields in this phenomenon are discussed and represented graphically. The results have been discussed under the effects of thermoelectric parameter and Thomson parameter. [ABSTRACT FROM AUTHOR]

The effect of Thomson heating of semiconductor medium is studied. Analytical discussions are made in the presence of thermoelectricity theory and magnetic field in context of Photothermal transport process. The interactions between plasma, thermoelectric, electromagnetic and elastic waves are taken into consideration. The governing equations are investigated in two dimensional deformations of homogenous, isotropic medium. The density of charge is taken as a function of time only of the induced electric current. The normal mode technique is used to obtain the physical quantities field under investigation. Some electro-mechanical loads and thermal effect through recombination process are applied on the free surface of semiconductor elastic medium. The distributions of physical fields in this phenomenon are discussed and represented graphically. The results have been discussed under the effect of thermoelectric parameter and Thomson parameter. [ABSTRACT FROM AUTHOR]

Described herein is a detailed and comprehensive multiphysics model of a thermoelectric generator (TEG). The one-dimensional model uses electrical–thermal analogies solved for transient response using SPICE. There are many advantages and applications of thermoelectric generators. Wider use and application advancements are generally limited by the tools available for engineering and scientific studies. Currently, available modeling tools are limited by some combination of speed, platform capabilities, or missing physics that are not used or assumed to be negligible. The TEG module model herein is made up of two sub-models, the thermoelement model and the non-thermoelement model. Rather than a lumped thermoelement model, the model herein makes use of distributed physics that include the following: Thomson effect, temperature dependence, mass, Joule heat, thermal resistance, Seebeck effect, and electrical resistance. The non-thermoelement model takes into account temperature dependence and simulates Joule heat generation, thermal resistances, thermal and electrical interface resistances, and mass for and between the ceramic, copper, and solder. The comprehensive model herein was correlated to experimental data that simultaneously varied electrical current and hot and cold side temperatures with time. Very minimal adjustments to reported thermoelectric properties were required to almost perfectly match the experimental transient power output. The effects of the non-thermoelement model, distributed Thomson effect model and distributed temperature dependent property model were quantified. The model ran very quickly, taking 2.5 real-time seconds to run a 4000 s transient simulation. [ABSTRACT FROM AUTHOR]

The semi-analytical methods of thermoelectric energy conversion efficiency calculation based on the cumulative properties approach and reduced variables approach are compared for 21 high performance thermoelectric materials. Both approaches account for the temperature dependence of the material properties as well as the Thomson effect, thus the predicted conversion efficiencies are generally lower than that based on the conventional thermoelectric figure of merit ZT for nearly all of the materials evaluated. The two methods also predict material energy conversion efficiencies that are in very good agreement which each other, even for large temperature differences (average percent difference of 4% with maximum observed deviation of 11%). The tradeoff between obtaining a reliable assessment of a material’s potential for thermoelectric applications and the complexity of implementation of the three models, as well as the advantages of using more accurate modeling approaches in evaluating new thermoelectric materials, are highlighted. [ABSTRACT FROM AUTHOR]

In this work, the influences of the Thomson effect and the geometry of the p-type segmented leg on the performance of a segmented thermoelectric microcooler (STEMC) were examined. The effects of geometry and the material configuration of the p-type segmented leg on the cooling power (Qc) and coefficient of performance (COP) were investigated. The influence of the cross-sectional area ratio of the two joined segments on the device performance was also evaluated. We analyzed a one-dimensional p-type segmented leg model composed of two different semiconductor materials, Bi2Te3 and (Bi0.5Sb0.5)2Te3. Considering the three most common p-type leg geometries, we studied both single-material systems (using the same material for both segments) and segmented systems (using different materials for each segment). The COP, Qc and temperature profile were evaluated for each of the modeled geometric configurations under a fixed temperature gradient of ΔT = 30 K. The performances of the STEMC were evaluated using two models, namely the constant-properties material (CPM) and temperature-dependent properties material (TDPM) models, considering the thermal conductivity (κ(T)), electrical conductivity (σ(T)) and Seebeck coefficient (α(T)). We considered the influence of the Thomson effect on COP and Qc using the TDPM model. The results revealed the optimal material configurations for use in each segment of the p-type leg. According to the proposed geometric models, the optimal leg geometry and electrical current for maximum performance were determined. After consideration of the Thomson effect, the STEMC system was found to deliver a maximum cooling power that was 5.10% higher than that of the single-material system. The results showed that the inverse system (where the material with a higher Seebeck coefficient is used for the first segment) delivered a higher performance than the direct system, with improvements in the COP and Qc of 6.67% and 29.25%, respectively. Finally, analysis of the relationship between the areas of the STEMC segments demonstrated that increasing the cross-sectional area in the second segment led to improvements in the COP and Qc of 16.67% and 8.03%, respectively. [ABSTRACT FROM AUTHOR]

In recent years the interest for the harvest of energy with micro thermoelectric generators ( μ TEG) has increased, due to its advantages compared to technologies that use fossil fuels. There are three ways to improve the performance of the device, by modifying its structure, type of material and operation control. In this study, the role of the load resistance R L on the performance of a μ TEG with nanostructured materials is investigated. The interaction of the load resistance with the thermoelements exhibits interesting features, arising from the coupling of the temperature-dependent electrical and thermal transport properties at different temperature ranges and the architecture of nanostructured thermoelectric materials. This coupling results in inflections on the efficiency, i.e., maximum and minimum values of the efficiency at higher temperatures, 600⁻900 K. We show the explicit dependence of the performance of the μ TEG in terms of the load resistance and discuss the underlying physics. The unusual features of the efficiency of nanostructured thermoelectric materials are a result of the behavior of the power factor and the nonequilibrium properties of the system. We also analyze the effect of the geometric shape of the thermoelements on the device. We determine the performance of the μ TEG, evaluating the generation power and its efficiency. The results show that the efficiency of the device can decrease or increase depending on the value of R L , while the power decreases with an increase of the load resistance.

Thermoelectric effects are envisioned to reduce programming currents in nanopillar phase-change memory (PCM) cells. However, due to the inherent symmetry in such a structure, the contribution due to thermoelectric effects on programming currents is minimal. In this paper, we propose a hybrid PCM structure, which incorporates a twofold asymmetry specifically aimed to favorably enhance the thermoelectric effects. The first asymmetry is introduced via an interface layer of low thermal conductivity and high negative Seebeck coefficient, such as polycrystalline SiGe, between the bottom electrode contact and the active region comprising the phase-change material. This results in an enhanced Peltier heating of the active material. The second one is introduced structurally via a taper that results in an angle-dependent Thomson heating within the active region. Various device geometries are analyzed using 2-D-axis-symmetric simulations to predict the effect on programming currents as well as for different thicknesses of the interface layer. A programming current reduction of up to 60% is predicted for specific cell geometries. Remarkably, we find that due to an interplay of Thomson cooling in the electrode and the asymmetric heating profile inside the active region, the predicted programming current reduction is resilient to fabrication variability. [ABSTRACT FROM PUBLISHER]

A generalized finite-time thermodynamic model of irreversible multi-element thermoelectric generator is established taking into account inner and external factors. The inner effects include Seebeck effect, Fourier effect, Joule effect and Thomson effect. The irreversibility is caused by the finite-rate heat transfer between the heat reservoirs and the device. The theoretical iterative functions of the hot and cold junction temperatures and energy equations are obtained. The model is applied to the analysis of a multi-element thermoelectric generator, which is made of typical thermoelectric materials. It is found that, for given other parameters, there is an optimal electrical current, an optimal length of thermoelectric elements and an optimal ratio of thermal conductance allocation corresponding to the maximum power output. Thus, internal and external simultaneous multivariable optimizations are performed for a maximum power output. The effects of several important parameters on the optimal variables are analyzed in detail. The comparison between the optimized power and the non-optimized power shows that the multivariable optimization is necessary and effective for various working conditions. The model and optimization conclusions obtained herein can be applied to not only the analysis and optimization but also the design of thermoelectric generators. [ABSTRACT FROM AUTHOR]

Abstract: Most thermoelectric device modeling neglects the non-linear Thomson effect in order to develop a closed-form solution to the governing heat equation. This simplified solution is beneficial for system modeling and optimization when more intensive numerical techniques are prohibitive. An averaged Seebeck coefficient is often used in conjunction with the closed-form solution to incorporate approximately the effect of this neglected term (termed the “standard model”). While the standard model has been accepted in the past for materials under small temperature gradients and relatively constant Seebeck coefficient, there has not been a systematic assessment of validity of this modeling approach, especially for emerging materials and large temperature gradients. This work rigorously demonstrates the accuracy and limitations of the standard model through analytical derivation and comparison with an efficient numerical solution. It is proven that the standard model produces the exact module output power if an integral-averaged Seebeck coefficient is used, and also that the standard model provides a reasonably-accurate estimation of module efficiency, despite its limiting assumptions. These findings prove that the standard model in fact incorporates the Thomson effect with sufficient accuracy that it may be used to simulate and optimize thermoelectric systems as an alternative to computationally expensive numerical simulations. [Copyright &y& Elsevier]

Thermoelectric (TE) materials play an important role in energy production and utilization, but the temperature dependence of material properties makes theoretical analysis challenging. In this work, the TE differential equation is solved by introducing the volume average of TE material parameters, and a simplified TE element model is established for a TE element with a linear temperature profile. The temperature dependence of the Seebeck coefficient, electrical resistivity and thermal conductivity are incorporated into the thermal conductivity equation, and the TE conversion efficiency is solved. This proposed model is applied to a high-performance N-type half-Heusler alloy, and the obtained maximum conversion efficiency agrees well with the numerical results (with relative error 1.36%) for an average temperature T m = 510 K and temperature difference Δ T = 440 K. The results confirm that the proposed model, which incorporates the Thomson effect, is simple and accurate, providing valuable guidance for optimal performance design of TE devices. • Putting volume average properties makes TE non-linear model to a linear one. • Conversion efficiency of the proposed model agrees well with the numerical result. • The effect of coefficients on η demonstrates the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

In recent years the interest for the harvest of energy with micro thermoelectric generators (μ TEG) has increased, due to its advantages compared to technologies that use fossil fuels. There are three ways to improve the performance of the device, by modifying its structure, type of material and operation control. In this study, the role of the load resistance R L on the performance of a μ TEG with nanostructured materials is investigated. The interaction of the load resistance with the thermoelements exhibits interesting features, arising from the coupling of the temperature-dependent electrical and thermal transport properties at different temperature ranges and the architecture of nanostructured thermoelectric materials. This coupling results in inflections on the efficiency, i.e., maximum and minimum values of the efficiency at higher temperatures, 600–900 K. We show the explicit dependence of the performance of the μ TEG in terms of the load resistance and discuss the underlying physics. The unusual features of the efficiency of nanostructured thermoelectric materials are a result of the behavior of the power factor and the nonequilibrium properties of the system. We also analyze the effect of the geometric shape of the thermoelements on the device. We determine the performance of the μ TEG, evaluating the generation power and its efficiency. The results show that the efficiency of the device can decrease or increase depending on the value of R L , while the power decreases with an increase of the load resistance. [ABSTRACT FROM AUTHOR]