Performance Of Thermoelectric Modules Research Articles

Maximizing cooling/heating performance of thermoelectric modules across variable thermal loads via optimal control based on COP curves

The thermoelectric module has high potential as a compact electrothermal actuator in the generation of cooling/heating effects without any moving part. However, one difficulty of the design is that the fundamental principles of optimal cooling/heating performance of thermoelectric modules are not yet fully understood and implemented. The purpose of this paper is to propose a mathematical optimization to gain insight and implement the most effective usages. In the proposed analysis, it is found that the coefficients of performance (COP) are dependent on the driving voltage and the ceramic-substrate temperatures of the thermoelectric module at both the cold and hot sides. The thermoelectric properties of a 91.2W thermoelectric module are used to simulate the proposed performance analysis to find the optimal driving voltage at desired operating temperatures at both sides on COP curves. The coefficient of determination R2 of 0.9832 indicates strong agreement on the coefficients of performance between the analysis and the experiments under one hundred thirty-seven operating conditions. With the proposed methodology, the 91.2W thermoelectric module can be operated at the maximum coefficient of performance across variable thermal loads of airflow where the optimal driving voltage is determined from desired operating temperatures at both sides.

Desalination performance evaluation of a solar still enhanced by thermoelectric modules

Water scarcity is a pressing global issue, as a significant portion of the world's water resources remain salty and unsuitable for human consumption. Solar desalination has emerged as a sustainable solution to address this challenge, utilizing solar energy for water decontamination and purification. This study explores the enhancement of solar stills through the integration of thermoelectric (TE) modules, focusing on their impact on desalination performance. The optimal saltwater levels, TE module performance, and the efficiency of the system are identified in this investigation. The results of this study reveal that the integration of TE unit into solar still systems leads to a substantial increase in water production, achieving an impressive 35% improvement in productivity compared to conventional solar stills. The TE modules act as efficient cooling agents, accelerating the condensation process within the system. This improvement has substantial implications for addressing water scarcity in arid regions and providing an eco-friendly solution for freshwater production. By harnessing solar energy and advanced TE technology, the findings of this study underscore the potential of TE-enhanced solar desalination systems in providing sustainable and reliable sources of fresh water, even in areas with limited access to traditional water resources. The successful integration of TE modules into solar stills suggests a promising avenue for future research and development. Further exploration of these systems, optimization of TE module parameters, and increased utilization of renewable energy sources are all steps that can be taken to improve water production efficiency and contribute to water resource sustainability.

Modeling study on the geometric optimization of thermoelectric modules

Abstract The performance of thermoelectric power generators (TEG) primarily depends on the properties of the thermoelectric materials employed. For conventional thermoelectric modules (TEM) utilizing the same material, the geometric parameters also play a significant role in determining TEM performance. As such, optimizing the geometry of TEM can lead to improved performance. In this study, TEM were modeled, designed, fabricated, and tested to investigate the effects of different geometric parameters on their performance. Numerical simulations were conducted under both constant temperature and constant flow boundary conditions, and the results were validated through experimental testing. The simulation results under constant flow boundary conditions exhibited good agreement with the experimental results. The effects of thickness, cross-sectional area, and filling ratio of thermoelectric legs on TEM performance were investigated through numerical simulations and compared with findings from previous studies. It was observed that increasing the cross-sectional area of the thermoelectric legs led to a decrease in the power output of TEM. Conversely, increasing the filling ratio effectively enhanced the TEM's performance. Furthermore, an optimal thermoelectric leg thickness was identified through the numerical simulations that could yield the maximum power output of TEM. The underlying mechanism behind this observation was explained, shedding light on why different reports have identified different optimal thicknesses. Optimizing the thermoelectric leg thickness can help maintain a high effective temperature difference and low internal resistance, which can vary based on the specific type of TEM and the thickness and thermal conductivity of the insulating substrates and copper sheets.

Realizing ultrahigh ZT value and efficiency of the Bi2Te3 thermoelectric module by periodic heating

Thermoelectric power generation is regarded as a promising technology to convert waste heat into electricity. This study aims to address the low conversion efficiency of thermoelectric modules and introduces a novel periodic heating method to enhance their performance. Two new indicators, time average ZTta value and effective conversion efficiency, are introduced to assess the dynamic behavior of thermoelectric modules. A Bi2Te3-based thermoelectric module with n-type Bi2Te3-xSex and p-type BixSb2-xTe3 materials is adopted as the research objective and tested on a designed transient experimental setup. Besides, a transient numerical model is developed to explore the optimal transient heat source and study the effect of various parameters on dynamic behavior. Compared with the steady-state efficiency of 3.76% and ZTta value of 0.78 at a heat supply of 60 W, the time average efficiency and ZTta value are improved by 52.93% and 43.59% respectively using the periodic heating method. Also, a smaller leg height, a larger leg area, more TE couples, and lower thermal conductivity are suggested for improving the dynamic behavior. This work offers a new periodic heating method to improve the output performance of thermoelectric modules, which may promote the broader application of thermoelectric power generation technology.

High-performance tellurium-free thermoelectric module for moderate temperatures using α-MgAgSb/Mg2(Si,Sn)

α-MgAgSb is a promising thermoelectric material with an average figure of merit above unity between room temperature and 573 K, making it attractive for low temperature waste heat recovery or temperature regulation applications. We demonstrate here the first α-MgAgSb/Mg2(Si,Sn)-based thermoelectric module, where Mg2(Si,Sn) was chosen as n-type counterpart due to its excellent thermoelectric properties, low weight, abundant, and eco-friendly constituents. By using this new material combination, a maximum conversion efficiency of 6.4% and maximum power of 0.68 W were achieved for a temperature difference of 275 K, superior to commercially available (Bi,Te,Sb)-based thermoelectric modules. The Constant Property Model was used to check the validity of the measurement results and to identify room for further improvement. The characterization of the prototype shows a relatively good match between measurement and calculation for most of the thermoelectric module performance parameters; however, the measured internal electrical resistance is around 10% higher than the predicted values, indicating opportunities for further enhancement.

Effect analysis on energy conversion enhancement of porous medium micro-combustor and thermoelectric system and its optimization

The energy conversion of micro combustion system has become the main research direction at present. However, due to the small size of micro-combustors, they face challenges such as unstable combustion and difficulty in effectively converting generated thermal energy into usable energy. This work mainly studies the thermoelectric conversion system based on porous medium micro-combustor, which mainly uses the high energy density of micro-combustor to replace the traditional battery energy and improve the working time of small equipment. And this work also establishes the coupling model of porous medium micro combustor and thermoelectric module. By analyzing the performance parameters of the micro thermoelectric system in different flow rate, the results show that at low flow rates, semiconductor materials with better thermoelectric performance, such as Bi2Te3, can be used to improve the energy conversion efficiency of the system. However, the low heat release from combustion leads to lower maximum output power. At high flow rates, there is a significant improvement in the thermoelectric conversion performance of the system, but it is limited by the temperature of the thermoelectric materials. To optimize the impact of these factors on micro-thermoelectric systems, the optimization methods were analyzed as: (1) The temperature uniformity of micro-combustor wall can be improved by using mixture with low equivalence ratio and high flow rate; (2) enhancing the thermal conductivity of the micro-combustor and porous medium to improve the thermal conductivity of micro thermoelectric system; (3) Using CH4-H2 mixed combustion to reduce combustion temperature and ensure that thermoelectric materials work within the normal temperature range; (4) The segmented thermocouple is used to improve the thermoelectric performance of thermoelectric module. The results show that using a mixture with low equivalence ratio and high flow rate can achieve a maximum conversion efficiency of 5.51%. Using mixed combustion to reduce combustion temperature can increase the maximum output power of the system to 57.8 W.

Mechanical behaviour of thermoelectric materials – a perspective

ABSTRACT Research on thermoelectric materials – with their vast potential for applications in solid-state cooling or energy-conversion devices – has so far mainly focused on enhancing their conversion efficiency. However, understanding and tailoring the mechanical performance of thermoelectric modules and devices is crucial for their long-term use, as they are subjected to spatially-complex and time-varying thermomechanical stresses – both internal and external – which may lead to plastic, fatigue and/or creep deformation. This leads to changes in thermoelectric performance, dimensions (via strain accumulation) and mechanical integrity (via crack and pore formation, leading to failure). This review addresses the current understanding of various modes of stress-induced deformation that can take place during extended operation of thermoelectric materials and their impact on the strain (elastic, plastic, and creep), and the associated damage (bloating, fatigue, and fracture). Finally, some new areas of research straddling mechanical and thermoelectric behaviour are identified.

Numerical investigation on cooling performance of multilayer pyramid thermoelectric module

A three-dimensional study on the cooling performance of thermoelectric module consisting of multilayer pyramid thermoelectric legs is investigated numerically. Two physical models were established for comparison, which are rectangular shaped and multilayer pyramid thermoelectric cooling modules, respectively. This study mainly focuses on the effect of leg height, side ratio and the number of leg layers on the cooling performance of thermoelectric module. Generally, the obtained results showed that the multilayer pyramid module has better cooling performance than that of rectangular shaped module. By increasing the values of side ratio and the number of layers, the maximum reduction of the minimum averaged temperature of cold surface reaches 11.25 K compared to the rectangular shaped module. It is also observed that when the values of side ratio and the number of leg layers are low such as 1.5 and 1, the multilayer pyramid module has not very good cooling performance. Finally, a recommended map on the multilayer pyramid module is presented according to side ratio and the number of leg layers for the different heights of thermoelectric legs to evaluate the cooling performance.

Legs Geometry Influence on the Performance of the Thermoelectric Module

The performance of the thermoelectric module highly depends on the geometry of the legs, the module area, and implicitly on the number of the pairs, besides the properties of the materials. The geometry of the legs consists of the shape, the dimensions on three axes, and whether the legs are filled or are hollow. The legs can have one hollow or more, the hole can be from the top to bottom or not. This paper studies and compares the performance of different thermoelectric modules in function of the shape: square, triangular, trapezoid, reverse trapezoid, hourglass, inverse hourglass (filled and with the hollow from the top to the bottom or not), and with different dimensions of the length and width. The simulations are performed using the COMSOL Multiphysics software, where 3D numerical models are developed and solved using the finite element method. The results are compared with others from the specialized literature for a one pair square shape. The current-voltage and power-voltage characteristics have a good matching, which proves the simulations are good and the model can be used for other shapes. A steady-state heating condition is applied to the hot side of the thermoelectric generators, while the cold side is subjected to steady state, natural convection, and forced convection heating conditions. The square shape with an internal hollow is studied first. The best performance when the length and width are 1 mm × 1 mm, 1.5 mm × 1.5 mm, and 2 mm × 2 mm is obtained for the thermoelectric generator with filled square legs. The highest maximum power is obtained for thermoelectric generator with the sizes 2 mm × 2 mm. The gain in power for the square shape in comparison with the worst value of the TEG (Inverse Hourglass for filled and Triangular for hollow) for the three dimensions considered is for those filled 199%, 202%, and 204%, respectively, and for those that are hollow 198%, 232%, and 243%, respectively. The reduction in maximum power is 5%, for the thermoelectric generator with square legs (2 mm × 2 mm) and with hollow legs, in comparison with one filled. The maximum power increases for the thermoelectric generator with square legs which have a hollow interior, in this case 2 mm × 2 mm, with 0.2% and 1% for the thermoelectric generator with sizes of 1 mm × 1 mm. Additionally, the results obtained for the square filled shape are compared with the real ones obtained for a thermoelectric generator with sizes 40 mm × 40 mm × 4 mm. The matching is very good, which confirms that the model can be used for different geometry of the thermoelectric generators in order to help the manufacturers improve their performance.

Effect of thermal cycling with various heating rates on the performance of thermoelectric modules

The thermoelectric module (TEM) offers a method to directly convert heat into electrical energy through the principle of the Seebeck effect. Unstable thermal cycling, however, can affect the performance of the TEM. In this work, the effects of thermal cycling at various heating rates on the electrical output of the thermoelectric system were investigated. An experimental rig was built to adapt the heating process and data measurements. Thermoelectric material was fixed between a heater plate on the hot side and a waterblock on the cold side of the TEM. An electrical power source was used to supply the heat energy in the heater plate to produce various heating rates for 100 cycles. The thermal cycling was controlled carefully. The temperatures of the hot and cold sides of the thermoelectric module were measured via thermocouples that were linked to a data logger for data acquisition. The results showed that an increase in the number of thermal cycles reduced the electrical output of the thermoelectric generator (TEG) system, which is composed of voltage, current, and power. The electrical output, however, increased at a lower heating rate. The increased internal resistance was responsible for the electrical drop.

Performance evaluation and improvement of thermoelectric generators (TEG): Fin installation and compromise optimization

How to improve the performance of thermoelectric generators is an important issue to recover waste heat and convert it into green power, which is conducive to practicing net-zero carbon dioxide emissions. The heat transfer and power generation of a thermoelectric module (TEM) under the influence of fin installation is investigated by three-dimensional fully numerical simulations where vehicle exhaust waste heat is harvested. This study considers a TEM in a hot channel without fins as well as with plate fins and square pin fins, while a cold channel is used to cool the TEM. The results show that installing plate fins or square pin fins can drastically intensify waste heat harvest, and the optimal number of square pin fins is 78 which increases the output power of the TEM by 24.14% compared to the plate fins. A compromise method in terms of heat flow rate ratio and heat flow rate ratio per unit area of square pin fins is conducted, which simultaneously considers the TEM’s output power and material cost. As a result, it is found that the optimal number of square pin fins is 54. The influences of the temperature and mass flow rate of the hot fluid on TEM performance are also evaluated, and the results indicate that the former has a pronounced impact whereas the latter is relatively unimportant. Installing more square pin fins gives rise to a higher pressure drop. Nevertheless, the net output power of the TEM increases with increasing the number of square pin fins and the highest value occurs at 78.

Power generation of thermoelectric generator with plate fins for recovering low-temperature waste heat

Low-temperature waste heat has great potential for renewable power because it accounts for around 60% of total industrial waste heat. This study develops a model of integrating thermoelectric generation, computational fluid dynamics, and plate fins to figure out a low-temperature waste heat recovery system for power generation. The effect of the number of partitions of a thermoelectric module on its performance is examined, and the results show that a single module without a partition can provide accurate predictions. Four different combinations between wastewater and air in the hot and cold channels under three different Reynolds numbers (i.e., Re = 10, 100, and 1,000) on thermoelectric modules’ performance suggest that only combining hot wastewater and cooling water can contribute electricity to a certain extent. By installing fins with a number range of 0–27, it indicates that fin installation can dramatically intensify heat transfer and thermoelectric modules’ performance. The optimal number of fins at Re = 10 and 100 is 21, whereas it is 27 at Re = 1,000. The maximum total output power and mean conversion efficiency are 0.411 W and 0.95%, respectively, with 27 fins at Re = 1,000. These values account for 105.5% and 43.94% improvements when compared to the TEMs without fins. Even though installing fins increases the pressure drop in the channel, its value is much smaller than the generated power (less than1%). The developed method in this study can be used to efficiently and accurately predict the performance of thermoelectric modules, and obtained results have provided practical insights into the design of low-temperature waste heat recovery systems for green power generation.

Algorithm for monitoring the operability of Peltier thermoelectric modules based on the identification of transients

The work is devoted to the development and research of an algorithm for identifying transients in order to monitor the performance of Peltier thermoelectric modules (TEMs). The paper presents the main expressions for the analysis of heat transfer in TEM, as well as a block diagram of the algorithm for identifying the performance of TEM based on the comparison between the time constants of the tested and the reference module according to the Student’s criterion. The proposed method was tested experimentally by comparing the time constants of the correct and defective modules 1MS06-030-05. The experiment showed a significant difference between the duration of the transition process of the correct module (0.7 s) and defective module (0.4 s) with a mean square error of 0.07 s and a significance level of <0.001. In the future, it is planned to develop software based on this algorithm, as well as examine the proposed method by testing a wide class of TEMs.

The Combined Impacts of Leg Geometry Configuration and Multi-Staging on the Exergetic Performance of Thermoelectric Modules in a Solar Thermoelectric Generator

Abstract The performance of thermoelectric generators (TEGs) can be improved either by the adoption of multi-stage or tapered leg configuration. So far, a hybrid device that simultaneously uses both multi-staging and tapered leg geometry to improve its performance has not been conceived. Thus, we present a thermodynamic modeling and optimization of a two-stage thermoelectric generator (TTEG) with tapered leg geometries using ansys 2020 r2 software. The optimized parameters include the leg height, area, concentrated solar radiation, and external load resistance. First, the X-leg TEG only improves the performance of the trapezoidal leg TEG below a leg height of 3 mm. Beyond 3 mm, the performance of both TEGs become very similar. Long thermoelectric legs provide higher efficiencies, while short legs generate maximum power densities. To obtain maximum efficiencies, the initial leg height of the thermoelectric legs, 1.62 mm, is increased by 517.28%, while the initial leg area, 1.96 mm2, is decreased by 64.29%. Also, the proposed TTEG with tapered legs (trapezoidal and X-legs) improves the exergetic efficiency of the base case, single-stage rectangular leg TEG, by 16.7%. Furthermore, the use of tapered leg TEGs, in single and multi-stage arrangements, reduces the exergy conversion index of conventional rectangular leg TEGs by 1.89% and 0.98%, respectively. Finally, the use of tapered legs and multi-stage configurations increases the thermodynamic irreversibilities of conventional rectangular leg TEGs, thus reducing their thermodynamic stability.

Towards tellurium-free thermoelectric modules for power generation from low-grade heat

Thermoelectric technology converts heat into electricity directly and is a promising source of clean electricity. Commercial thermoelectric modules have relied on Bi2Te3-based compounds because of their unparalleled thermoelectric properties at temperatures associated with low-grade heat (<550 K). However, the scarcity of elemental Te greatly limits the applicability of such modules. Here we report the performance of thermoelectric modules assembled from Bi2Te3-substitute compounds, including p-type MgAgSb and n-type Mg3(Sb,Bi)2, by using a simple, versatile, and thus scalable processing routine. For a temperature difference of ~250 K, whereas a single-stage module displayed a conversion efficiency of ~6.5%, a module using segmented n-type legs displayed a record efficiency of ~7.0% that is comparable to the state-of-the-art Bi2Te3-based thermoelectric modules. Our work demonstrates the feasibility and scalability of high-performance thermoelectric modules based on sustainable elements for recovering low-grade heat.

Numerical Investigation of the Effect of Cooling and Heating Conditions on the Performance of Thermoelectric Module

Today, the need for energy increases, and fossil fuel resources run out rapidly so energy costs also increase rapidly. The most important feature of fossil fuels is that they consist of hydrocarbon and organic substances containing high levels of carbon. This causes great harm to the world and humanity. In the face of this dangerous situation, world states look for new and clean energy sources. As a result, the trend towards renewable energy sources increases rapidly. In this context, TE (thermoelectric) module is an important source to convert heat to electrical energy. The amount of electricity generation from heat depends on the temperature difference between surfaces of the TE module. The electrical power obtained from heat increases with the increase of temperature difference. This work aims to investigate numerically the heat transfer and electricity generation performance of a 〖Bi〗_2 〖Te〗_3-based TE module embedded with cylindrical pin-fin heat sink under the different hot surface and air temperature conditions with different air velocities. The results were evaluated and discussed with parameters such as temperature distribution, power input, power output, voltage output, current output, temperature difference, total thermal resistance, conversion efficiency and Nusselt number according to Reynolds numbers. In all analyses, it was observed that performance of the heat transfer and electricity generation of the TE module increase with the increase in Reynolds number. The highest conversion efficiency was obtained generally at surface temperatures of 200℃, specifically at air temperature of 5℃ and the Reynolds number of 20000. In addition, it was observed that the temperature difference between the surfaces of the TE module is not sufficient alone to give good performance and besides, it is necessary to keep the cold surface at low temperature.

Optimization of Power and Efficiency in a segmented legs STEG using the Taguchi method

In the recent times, many researchers have concentrated on the development of thermoelectric materials with higher values of figure of merits to enhance the conversion efficiency. It have been observed in some of the previous studies that the figure of merit and hence, the performance of thermoelectric modules can be enhanced using the module with segmented legs of two or more thermoelectric materials. In this study, the application of segmented thermoelectric modules in a solar assisted thermoelectric generator have been presented. PbTe and BiTe alloys are used in the segmented module. Except the figure of merit, the performance of thermoelectric generator is also dependent on temperatures across modules, load resistance and various design parameters such as leg geometries, cross sectional area of legs etc. So, Taguchi method of optimization was employed using five factors and five levels design to optimize the power and conversion efficiency. The power and efficiencies are mathematically calculated at different combinations according to L25 orthogonal array. The maximum power output is predicted up to 31.52 W and conversion efficiency up to 14.61% using The Taguchi analysis. Analysis of Variance method is also used to analyze general linear model which results into the estimation of contribution percentages of each factor on the power and efficiency.

Study of the Thomson effect on the performance of thermoelectric modules with application to the energy recovery

This paper analyzes the impact of the Thomson effect on the performance of thermoelectric modules. For this, different mathematical models are carried out that involves the relationship between temperature and the seebeck coefficient. These mathematical models are based on the equations that describe thermoelectric effects and are solved using finite element methods. Through linear and polynomial functions of the seebeck coefficient, the different behaviors that can occur in the Thomson coefficient and their effect on the power and efficiency of thermoelectric modules are analyzed. The results show that by not considering the Thomson effect, there is a variation of 31% and 32% in the power and efficiency of the thermoelectric module when the temperature conditions change, which makes it difficult to estimate the performance of the module. This problem can be solved by considering the Thomson effect since it predicts an approximately constant value of electrical power and efficiency for a wide temperature range. For the analyzed conditions, power and efficiency of 5.25 W and 13%, respectively, were observed. The proposed methodology allows an adequate estimation to determine the performance of the modules. Therefore, it could be implemented to search for materials that provide better thermoelectric characteristics.

Investigation into the use of thermoelectric modules as an alternative to conventional fluxmeters: Application to convective and radiative heat flux in buildings

The aim of the present work is to propose a methodology for the use of thermoelectric modules (TEM) as an alternative to conventional heat flux sensors, for estimating convective and radiative heat flux. In this experimental study, the performance of TEMs as heat flux sensors is compared to that of the heat flux sensor (HFS), a type of conventional heat flux sensor, based on the premise that the HFS has been proven to perform acceptably in heat flux measurement. The interest of this comparison arises from the cost and sensitivity of the TEM with respect to the HFS. A simple measurement device is proposed, consisting of heat flux and temperature sensors with a general formulation for decoupling the convective and radiative parts. This methodology is implemented in two cases (low and high thermal stress). The radiative part is found to be the same by using the TEM and the HFS in both cases. However, the convective part measured by the TEM is found to be about 2.5 times larger than the HFS measurements in case of low thermal stress, and 1.6 times larger for tin case of high thermal stress. To explain this difference, the extended surface approximation was employed. This approximation indicates that the convective heat flux estimated from the TEM is always expected to be 1.6 and 1.4 times larger than that from the HFS for the low and high thermal stresses respectively, when their thermoelectric properties and geometry are taken into account.

Exhaust waste energy recovery using Otto-ATEG-Stirling engine combined cycle

In the present study, using the Stirling cycle and thermoelectric modules, the exhaust heat dissipation of a gasoline engine was recovered. In this regard, a gasoline engine, a Stirling engine, and a commercial thermoelectric module were first modeled and validated. In order to benefit from the Stirling engine along with the gasoline engine, it was necessary to redesign the Stirling engine heater to suit the needs of the project. The designed heater is a shell and tube heat exchanger, and on its shell, there are places to install thermoelectric modules. In Ansys CFX software, the performance of this heat exchanger was analyzed and its performance was evaluated. The results illustrated the maximum pressure drop is about 2.63 mbar. Also, the net power generated by the module set is in the range of 223–528 W, and the Stirling engine power for the temperature range of 358 °C − 535 °C was reported to be 1.8–6.8 kW. In total, the combined cycle power and efficiency increased by about 7% and 2.5% respectively. Finally, the analysis showed that fuel consumption has decreased by about 8% and about 0.7% of this amount was related to the performance of thermoelectric modules.