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Advanced Studies of Thermoelectric Systems

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "J: Thermal Management".

Deadline for manuscript submissions: closed (24 October 2023) | Viewed by 12502

Special Issue Editor

1. Department of Electronics, Telecommunications and Energy, Valahia University of Targoviste, 130004 Targoviste, Romania
2. Istituto Nazionale di Ricerca Metrologica—INRIM, 10135 Torino, Italy
Interests: thermoelectric systems; heat and mass transfer; thermal comfort
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

There is an increasing interest today towards green technologies that may reduce the carbon emissions and increase energy efficiency also at small-scale applications such as energy harvesting. Thermoelectric systems based on the Seebeck, Peltier and Thomson effects are gaining interest in a range of applications that includes both power generation and cooling technologies. Thermoelectric generators exploit temperature differences to generate electrical power and contribute to waste heat recovery, electricity generation in extreme environments, micro-generation for sensors, energy harvesting also in association with renewable energy sources, and more. Thermoelectric cooling modules exploit an electrical input to reduce the temperature at the cooling side, with applications to refrigeration, electronic cooling and various other types of coolers. Thermoelectric systems may be less efficient than other technologies used in similar applications, playing a complementary role with respect to these technologies. However, the importance of thermoelectric systems increases when specific conditions are requested, such as operation without noise, application in moving systems or without environmental pollution, and high operational flexibility within energy management systems.

This Special Issue welcomes research contributions that present innovative aspects concerning materials, modelling and applications of thermoelectric systems, as well as review articles focused on the latest trends in the relevant contexts.

Dr. Diana Enescu
Guest Editor

Manuscript Submission Information

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Keywords

  • energy efficiency
  • energy harvesting
  • figure of merit
  • heat transfer
  • heat recovery
  • Peltier effect
  • renewable energy applications
  • Seebeck effect
  • thermoelectric cooling
  • thermoelectric devices
  • thermoelectric materials
  • thermoelectric power generation
  • temperature control
  • thermal modeling
  • thermal performance
  • thermal energy

Published Papers (10 papers)

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Research

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27 pages, 6225 KiB  
Article
Design of Thermoelectric Generators and Maximum Electrical Power Using Reduced Variables and Machine Learning Approaches
by Alexander Vargas-Almeida, Miguel Angel Olivares-Robles and Andres Alfonso Andrade-Vallejo
Energies 2023, 16(21), 7263; https://0-doi-org.brum.beds.ac.uk/10.3390/en16217263 - 26 Oct 2023
Viewed by 899
Abstract
This work aims to contribute to studies on the geometric optimization of thermoelectric generators (TEGs) through a combination of the reduced variables technique and supervised machine learning. The architecture of the thermoelectric generators studied, one conventional and the [...] Read more.
This work aims to contribute to studies on the geometric optimization of thermoelectric generators (TEGs) through a combination of the reduced variables technique and supervised machine learning. The architecture of the thermoelectric generators studied, one conventional and the other segmented, was determined by calculating the cross-sectional area and length of the legs, and applying reduced variables approximation. With the help of a supervised machine learning algorithm, the values of the thermoelectric properties were predicted, as were those of the maximum electrical power for the other temperature values. This characteristic was an advantage that allowed us to obtain approximate results for the electrical power, adjusting the design of the TEGs when experimental values were not known. The proposed method also made it possible to determine the optimal values of various parameters of the legs, which were the ratio of the cross-sectional areas (Ap/An), the length of the legs (l), and the space between the legs (H). Aspects such as temperature-dependent thermoelectric properties (Seebeck coefficient, electrical resistivity, and thermal conductivity) and the metallic bridge that connects the legs were considered in the calculations for the design of the TEGs, obtaining more realistic models. In the training phase, the algorithm received the parameter (H) and an operating temperature value as input data, to predict the corresponding value of the maximum power produced. This calculation was performed for conventional and segmented systems. Recent advances have opened up the possibility of applying an algorithm for designing conventional and segmented thermocouples based on the reduced variables approach and incorporating a supervised machine learning computational technique. Full article
(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)
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16 pages, 5494 KiB  
Article
Evaluation of Performance and Power Consumption of a Thermoelectric Module-Based Personal Cooling System—A Case Study
by Anna Dąbrowska, Monika Kobus, Łukasz Starzak and Bartosz Pękosławski
Energies 2023, 16(12), 4699; https://0-doi-org.brum.beds.ac.uk/10.3390/en16124699 - 14 Jun 2023
Cited by 2 | Viewed by 995
Abstract
Thermoelectric (TE) technology is promising for reducing thermal discomfort of workers during their routine professional activities. In this manuscript, a preliminary evaluation of a newly developed personal cooling system (PCS) with flexible TE modules is presented based on an analysis of cooling efficiency [...] Read more.
Thermoelectric (TE) technology is promising for reducing thermal discomfort of workers during their routine professional activities. In this manuscript, a preliminary evaluation of a newly developed personal cooling system (PCS) with flexible TE modules is presented based on an analysis of cooling efficiency and power consumption. For this purpose, tests with human participation were performed involving the monitoring of local skin temperature changes and electrical parameters of the controller. Thanks to TE cooling, a significant reduction of local skin temperature was observed at the beginning of the experiment, reaching as much as 6 °C. However, the observed effect systematically became weaker with time, with the temperature difference decreasing to about 3 °C. Cooling efficiency stayed at the same level over the ambient temperature range from 25 °C to 35 °C. The obtained results showed that a proper fitting of the PCS to the human body is a crucial factor influencing the PCS cooling efficiency. Full article
(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)
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9 pages, 1621 KiB  
Article
Influence of Charge Transfer on Thermoelectric Properties of Endohedral Metallofullerene (EMF) Complexes
by Majed Alshammari, Turki Alotaibi, Moteb Alotaibi and Ali K. Ismael
Energies 2023, 16(11), 4342; https://0-doi-org.brum.beds.ac.uk/10.3390/en16114342 - 26 May 2023
Cited by 1 | Viewed by 956
Abstract
A considerable potential advantage of manufacturing electric and thermoelectric devices using endohedral metallofullerenes (EMFs) is their ability to accommodate metallic moieties inside their cavities. Published experimental and theoretical works have explained the usefulness of this resilience feature for improving the electrical conductance and [...] Read more.
A considerable potential advantage of manufacturing electric and thermoelectric devices using endohedral metallofullerenes (EMFs) is their ability to accommodate metallic moieties inside their cavities. Published experimental and theoretical works have explained the usefulness of this resilience feature for improving the electrical conductance and thermopower. Through thorough theoretical investigations of three EMF complexes employing three different metallic moieties involving Sc3C2, Sc3N, and Er3N and their configurations on a gold (111) surface, this research demonstrates that the thermoelectric properties of these molecular complexes can be tuned by taking advantage of the charge transfer from metallic moieties to Ih-C80 cages. Mulliken, Hirshfeld, and Voronoi simulations articulate that the charge migrates from metallic moieties to cages; however, the amount of the transferred charge depends on the nature of the moiety within the complex. Full article
(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)
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10 pages, 4666 KiB  
Article
Experimental Analysis of the Long-Term Stability of Thermoelectric Generators under Thermal Cycling in Air and Argon Atmosphere
by Julian Schwab, Christopher Fritscher, Michael Filatov, Martin Kober, Frank Rinderknecht and Tjark Siefkes
Energies 2023, 16(10), 4145; https://0-doi-org.brum.beds.ac.uk/10.3390/en16104145 - 17 May 2023
Viewed by 811
Abstract
It is estimated that 72% of the worldwide primary energy consumption is lost as waste heat. Thermoelectric Generators (TEGs) are a possible solution to convert a part of this energy into electricity and heat for space heating. However, for their deployment a proven [...] Read more.
It is estimated that 72% of the worldwide primary energy consumption is lost as waste heat. Thermoelectric Generators (TEGs) are a possible solution to convert a part of this energy into electricity and heat for space heating. However, for their deployment a proven long-term operation is required. Therefore, this research investigates the long-term stability of TEGs on system level in air and argon atmosphere under thermal cycling up to 543 K. The layout of the examined test objects resembles a TEG in stack design. The results show that the maximal output power of the test object in air reaches a plateau at 57% of the initial power after 50 cycles caused by an increased electrical resistance of the system. Whereas the test object in argon atmosphere shows no significant degradation of electrical power or resistance. The findings represent a step towards the understanding of the long-term stability of TEGs and can be used as a guideline for design decisions. Full article
(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)
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18 pages, 2834 KiB  
Article
Analyzing the Performance of Thermoelectric Generators with Inhomogeneous Legs: Coupled Material–Device Modelling for Mg2X-Based TEG Prototypes
by Julia Camut, Eckhard Müller and Johannes de Boor
Energies 2023, 16(9), 3666; https://0-doi-org.brum.beds.ac.uk/10.3390/en16093666 - 24 Apr 2023
Cited by 5 | Viewed by 1243
Abstract
Thermoelectric generators (TEGs) possess the ability to generate electrical power from heat. As TEGs are operated under a thermal gradient, inhomogeneous material properties—either by design or due to inhomogeneous material degradation under thermal load—are commonly found. However, this cannot be addressed using standard [...] Read more.
Thermoelectric generators (TEGs) possess the ability to generate electrical power from heat. As TEGs are operated under a thermal gradient, inhomogeneous material properties—either by design or due to inhomogeneous material degradation under thermal load—are commonly found. However, this cannot be addressed using standard approaches for performance analysis of TEGs in which spatially homogeneous materials are assumed. Therefore, an innovative method of analysis, which can incorporate inhomogeneous material properties, is presented in this study. This is crucial to understand the measured performance parameters of TEGs and, from this, develop means to improve their longevity. The analysis combines experimental profiling of inhomogeneous material properties, modelling of the material properties using a single parabolic band model, and calculation of device properties using the established Constant Property Model. We compare modeling results assuming homogeneous and inhomogeneous properties to the measurement results of an Mg2(Si,Sn)-based TEG prototype. We find that relevant discrepancies lie in the effective temperature difference across the TE leg, which decreases by ~10%, and in the difference between measured and calculated heat flow, which increases from 2–15% to 9–16% when considering the inhomogeneous material. The approach confirms additional resistances in the TEG as the main performance loss mechanism and allows the accurate calculation of the impact of different improvements on the TEG’s performance. Full article
(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)
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14 pages, 30631 KiB  
Article
Nanostructured Thermoelectric PbTe Thin Films with Ag Addition Deposited by Femtosecond Pulsed Laser Ablation
by Alessandro Bellucci, Stefano Orlando, Luca Medici, Antonio Lettino, Alessio Mezzi, Saulius Kaciulis and Daniele Maria Trucchi
Energies 2023, 16(7), 3216; https://0-doi-org.brum.beds.ac.uk/10.3390/en16073216 - 03 Apr 2023
Viewed by 1019
Abstract
Pulsed laser deposition operated by an ultra-short laser beam was used to grow in a vacuum and at room temperature natively nanostructured thin films of lead telluride (PbTe) for thermoelectric applications. Different percentages of silver (Ag), from 0.5 to 20% of nominal concentration, [...] Read more.
Pulsed laser deposition operated by an ultra-short laser beam was used to grow in a vacuum and at room temperature natively nanostructured thin films of lead telluride (PbTe) for thermoelectric applications. Different percentages of silver (Ag), from 0.5 to 20% of nominal concentration, were added to PbTe deposited on polished technical alumina substrates using a multi-target system. The surface morphology and chemical composition were analyzed by Scanning Electron Microscope and X-ray Photoelectron Spectroscopy, whereas the structural characteristics were investigated by X-ray Diffraction. Electrical resistivity as a function of the sample temperature was measured by the four-point probe method by highlighting a typical semiconducting behavior, apart from the sample with the maximum Ag concentration acting as a degenerate semiconductor, whereas the Seebeck coefficient measurements indicate n-type doping for all the samples. The power factor values (up to 14.9 µW cm−1 K−2 at 540 K for the nominal 10% Ag concentration sample) are competitive for low-power applications on flexible substrates, also presuming the achievement of a large reduction in the thermal conductivity thanks to the native nanostructuring. Full article
(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)
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15 pages, 14124 KiB  
Article
Employing the Peltier Effect to Control Motor Operating Temperatures
by Stephen Lucas, Romeo Marian, Michael Lucas, Titilayo Ogunwa and Javaan Chahl
Energies 2023, 16(5), 2498; https://0-doi-org.brum.beds.ac.uk/10.3390/en16052498 - 06 Mar 2023
Cited by 3 | Viewed by 1243
Abstract
Electrical insulation failure is the most common failure mechanism in electrical machines (motors and generators). High temperatures and/or temperature gradients (HTTG) are the main drivers of insulation failure in electrical machines. HTTG combine with and augment other destructive effects from over-voltage, to voltage [...] Read more.
Electrical insulation failure is the most common failure mechanism in electrical machines (motors and generators). High temperatures and/or temperature gradients (HTTG) are the main drivers of insulation failure in electrical machines. HTTG combine with and augment other destructive effects from over-voltage, to voltage transients, overload and load variations, poor construction techniques, and thermal cycling. These operating conditions cause insulation damage that leads to electrical insulation failure. The insulation failure process is greatly accelerated by pollutants and moisture absorption. A simple and robust way to reduce HTTG and moisture adsorption is by maintaining constant internal temperatures. The current method to maintain elevated internal temperatures and reduce condensation issues is by internal electrical heating elements. This paper examines the effectiveness of applying thermoelectric coolers (TECs), solid-state heat pumps (Peltier devices), as heaters to raise a motor’s internal temperature by pumping heat into the motor core rather than heating the internal air. TEC technology is relatively new, and the application of TECs to heat a motor’s internal volume has not previously been explored. In this paper, we explore the hypothesis that TECs can pump heat into a motor when out of service, reducing the HTTG by maintaining high winding slot temperatures and eliminating condensation issues. This paper describes a test motor setup with simple resistive heating (traditional method), compared with the application of TECs with heat sinks, heat pipes, and a water circulation heat exchanger, to gauge the capability of TECs to heat the inner core or winding area. In this paper, we demonstrate the full integration of TECs into a motor. The results show that each of the systems incorporating the TECs would effectively pump heat into the core and keep the winding hot, eliminating condensation issues and water ingress due to thermal cycling. Full article
(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)
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15 pages, 3418 KiB  
Article
Design Modifications for a Thermoelectric Distiller with Feedback Control
by Mohammad Tariq Nasir, Diaa Afaneh and Salah Abdallah
Energies 2022, 15(24), 9612; https://0-doi-org.brum.beds.ac.uk/10.3390/en15249612 - 18 Dec 2022
Viewed by 1117
Abstract
In this paper, a modified design for a thermoelectric distiller is proposed, constructed, and tested. The design modifications include adding an inclined cover for the thermoelectric module and a cooling fan. The thermoelectric module and the fan were operated by an open loop [...] Read more.
In this paper, a modified design for a thermoelectric distiller is proposed, constructed, and tested. The design modifications include adding an inclined cover for the thermoelectric module and a cooling fan. The thermoelectric module and the fan were operated by an open loop or a feedback control to have the desired productivity. As the distiller productivity depends on the operating conditions, these operating conditions are investigated to find the best performance with the highest pure water productivity. Furthermore. a comparison between the closed and the open loop for driving the cooling fan with different operating conditions is conducted. In this work, the mathematical model of the proposed distiller is derived. Experimental results illustrate the robustness of the proposed approach and they show that the suggested thermoelectric distiller with feedback control, for both cases with MPC and PID controllers, can increase pure water productivity by up to 150% when compared with the open loop thermoelectric distiller. Full article
(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)
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21 pages, 12124 KiB  
Article
Thermoelectric Performance Evaluation and Optimization in a Concentric Annular Thermoelectric Generator under Different Cooling Methods
by Wenlong Yang, Wenchao Zhu, Yang Yang, Liang Huang, Ying Shi and Changjun Xie
Energies 2022, 15(6), 2231; https://0-doi-org.brum.beds.ac.uk/10.3390/en15062231 - 18 Mar 2022
Cited by 8 | Viewed by 2272
Abstract
To ensure effective heat recovery of thermoelectric generators, a cooling system is necessary to maintain the working temperature difference of the thermoelectric couples, which decreases continuously due to thermal diffusion. In order to evaluate and improve the thermoelectric performance of a concentric annular [...] Read more.
To ensure effective heat recovery of thermoelectric generators, a cooling system is necessary to maintain the working temperature difference of the thermoelectric couples, which decreases continuously due to thermal diffusion. In order to evaluate and improve the thermoelectric performance of a concentric annular thermoelectric generator under various cooling methods, a comprehensive numerical model of the thermo-fluid-electric multi-physics field for an annular thermoelectric generator with a concentric annular heat exchanger was developed using the finite-element method. The effects of four cooling methods and different exhaust parameters on the thermoelectric performance were investigated. The results show that, in comparison to the cocurrent cooling pattern, the countercurrent cooling pattern effectively reduces temperature distribution non-uniformity and hence increases the maximum output power; however, it requires more thermoelectric semiconductor materials. Furthermore, when using the cocurrent air-cooling method, high exhaust temperatures may result in lower output power; high exhaust mass flow rates result in high exhaust resistance and reduce system net power. The maximum net power output Pnet = 432.42 W was obtained using the countercurrent water-cooling, corresponding to an optimal thermoelectric semiconductor volume of 9.06 × 10−4 m3; when compared to cocurrent water-cooling, the maximum net power increased by 8.9%, but the optimal thermoelectric semiconductor volume increased by 21.4%. Full article
(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)
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Review

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29 pages, 1618 KiB  
Review
Heat Transfer Mechanisms and Contributions of Wearable Thermoelectrics to Personal Thermal Management
by Diana Enescu
Energies 2024, 17(2), 285; https://0-doi-org.brum.beds.ac.uk/10.3390/en17020285 - 05 Jan 2024
Viewed by 908
Abstract
Thermoelectricity can assist in creating comfortable thermal environments through wearable solutions and local applications that keep the temperature comfortable around individuals. In the analysis of an indoor environment, thermal comfort depends on the global characteristics of the indoor volume and on the local [...] Read more.
Thermoelectricity can assist in creating comfortable thermal environments through wearable solutions and local applications that keep the temperature comfortable around individuals. In the analysis of an indoor environment, thermal comfort depends on the global characteristics of the indoor volume and on the local thermal environment where the individuals develop their activity. This paper addresses the heat transfer mechanisms that refer to individuals, which operate in their working ambient when wearable thermoelectric solutions are used for enhancing heating or cooling within the local environment. After recalling the characteristics of the thermoelectric generators and illustrating the heat transfer mechanisms between the human body and the environment, the interactions between wearable thermoelectric generators and the human skin are discussed, considering the analytical representations of the thermal phenomena. The wearable solutions with thermoelectric generators for personal thermal management are then categorized by considering active and passive thermal management methods, natural and assisted heat exchange, autonomous and nonautonomous devices, and direct or indirect contact with the human body. Full article
(This article belongs to the Special Issue Advanced Studies of Thermoelectric Systems)
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