Thermoelectric Energy Harvesting

Topic Information

Dear Colleagues,

In order to meet the ever-increasing energy demands of our societies in a climate-friendly fashion, we must continue to develop the present energy harvesting and recycling systems while looking for new sustainable solutions. In this regard, the thermoelectric phenomenon can be exploited to convert the large amounts of waste heat generated in our fossil-fuel-based economy (factories, houses, automobiles, etc.) into useful electric power. However, the low efficiency and high cost of conventional thermoelectric materials, together with the poor production scalability of thermoelectric devices, have impeded their mass deployment thus far.

Using novel inorganic materials, nanomaterials, and their hybrids with conductive organic molecules/polymers in thin films or bulk forms has proven to be a promising approach towards enhancing the thermoelectric properties of traditional materials and improving the efficiency of thermoelectric devices. However, the development of novel alloys and composites and the implementation of nanomaterials and organic semiconductors into large-sized real devices are major challenges. Crucial issues to be addressed include the materials’ chemical stability, toxicity, adaptability, scalability, flexibility, and mechanical robustness of the final devices. Toward this end, our Topic seeks to contribute to the thermoelectric energy-harvesting agenda through the most recent scientific and cross-disciplinary findings on thermoelectric materials and devices. We are inviting papers covering innovative scientific/technical developments, reviews, case studies, and analytical/assessment articles from all relevant disciplines.

Prof. Dr. Amir Pakdel
Dr. David Berthebaud
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Energies energies	3.2	5.5	2008	16.1 Days	CHF 2600	Submit
Materials materials	3.4	5.2	2008	13.9 Days	CHF 2600	Submit
Applied Sciences applsci	2.7	4.5	2011	16.9 Days	CHF 2400	Submit
Entropy entropy	2.7	4.7	1999	20.8 Days	CHF 2600	Submit
Nanoenergy Advances nanoenergyadv	-	-	2021	31 Days	CHF 1000	Submit

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29 pages, 66174 KiB  

Open AccessArticle

The Impact of Asymmetric Contact Resistance on the Operating Parameters of Thermoelectric Systems

by Ryszard Buchalik, Grzegorz Nowak and Iwona Nowak

Energies 2024, 17(3), 599; https://doi.org/10.3390/en17030599 - 26 Jan 2024

Viewed by 511

Abstract

This paper presents a simulation model for a system equipped with thermoelectric elements, considering the impact of independent thermal contact resistances on each side of the module. An analytical model was constructed, taking into account the asymmetry of thermal resistances between the generator/cooler [...] Read more.

This paper presents a simulation model for a system equipped with thermoelectric elements, considering the impact of independent thermal contact resistances on each side of the module. An analytical model was constructed, taking into account the asymmetry of thermal resistances between the generator/cooler and the respective heat source/heat sink. A comparative analysis of thermoelectric device operating indicators such as conducted heat, efficiency, and the electricity/cooling power produced was performed. The selection of electrical current in the circuit was analysed based on the maximization of power or efficiency. This paper discusses deviations from ideal conditions, specifically the absence of thermal resistance between the heat source/sink and the thermoelectric junction. The model accurately simulates the operating conditions of the thermoelectric system with a low computational cost. The results indicate that the total thermal resistance, rather than its location, predominantly affects the operation of the thermoelectric generator. However, in cooling operations, the influence of thermal resistance significantly depends on the cooling power demand and temperature. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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18 pages, 6619 KiB  

Open AccessArticle

Effect of Starting Powder Particle Size on the Thermoelectric Properties of Hot-Pressed Bi_0.3Sb_1.7Te₃ Alloys

by Ioanna Ioannou, Panagiotis S. Ioannou, Theodora Kyratsi and John Giapintzakis

Materials 2024, 17(2), 318; https://doi.org/10.3390/ma17020318 - 08 Jan 2024

Cited by 1 | Viewed by 612

Abstract

P-type Bi_0.3Sb_1.7Te₃ polycrystalline pellets were fabricated using different methods: melting and mechanical alloying, followed by hot-press sintering. The effect of starting powder particle size on the thermoelectric properties was investigated in samples prepared using powders of different particle [...] Read more.

P-type Bi_0.3Sb_1.7Te₃ polycrystalline pellets were fabricated using different methods: melting and mechanical alloying, followed by hot-press sintering. The effect of starting powder particle size on the thermoelectric properties was investigated in samples prepared using powders of different particle sizes (with micro- and/or nano-scale dimensions). A peak ZT (350 K) of ~1.13 was recorded for hot-pressed samples prepared from mechanical alloyed powder. Moreover, hot-pressed samples prepared from ≤45 μm powder exhibited similar ZT (~1.1). These high ZT values are attributed both to the presence of high-density grain boundaries, which reduced the lattice thermal conductivity, as well as the formation of antisite defects during milling and grinding, which resulted in lower carrier concentrations and higher Seebeck coefficient values. In addition, Bi_0.3Sb_1.7Te₃ bulk nanocomposites were fabricated in an attempt to further reduce the lattice thermal conductivity. Surprisingly, however, the lattice thermal conductivity showed an unexpected increasing trend in nanocomposite samples. This surprising observation can be attributed to a possible overestimation of the lattice thermal conductivity component by using the conventional Wiedemann–Franz law to estimate the electronic thermal conductivity component, which is known to occur in nanocomposite materials with significant grain boundary electrical resistance. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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12 pages, 8590 KiB  

Open AccessArticle

Development of Transpiration-Type Thermoelectric-Power-Generating Material Using Carbon Nanotube Composite Papers with Capillary Action and Heat of Vaporization

by Yudai Kamekawa, Koya Arai and Takahide Oya

Energies 2023, 16(24), 8032; https://doi.org/10.3390/en16248032 - 12 Dec 2023

Viewed by 760

Abstract

A transpiration-type thermoelectric-power-generating paper based on previously developed carbon nanotube (CNT) composite paper, which is a composite material of CNTs and pulp that can generate thermoelectric power, was developed. The newly developed thermoelectric-power-generating material does not require an external high-temperature heat source due [...] Read more.

A transpiration-type thermoelectric-power-generating paper based on previously developed carbon nanotube (CNT) composite paper, which is a composite material of CNTs and pulp that can generate thermoelectric power, was developed. The newly developed thermoelectric-power-generating material does not require an external high-temperature heat source due to the ability of paper to absorb liquid through capillary action and heat of vaporization generated when the liquid evaporates. The aim of this study is to investigate the feasibility of realizing the transpiration-type thermoelectric-power-generating paper. To begin with, the type of paper used as raw material for the composite paper was examined, and the fabrication process was modified in order to obtain more efficient liquid absorption based on capillary action. Then, the absorbing ability of the liquid was evaluated. Next, the feasibility of thermoelectric power generation using the heat of vaporization was confirmed. Moreover, for more efficient thermoelectric conversion, multisheet structures were also studied. Through several experiments, the material’s feasibility was verified, and it was confirmed that more power can be easily obtained through the use of multiple sheets. Specifically, a single sample spontaneously generated a temperature difference of up to 1.7 °C due to the heat of vaporization, generating an electromotive force of 36 $\mathsf{\mu }$V. From the sample with a five-sheet structure, an electromotive force of 356 $\mathsf{\mu }$V was obtained at a temperature difference of 2 °C. This material can be used in watery environments, such as rivers, lakes, and hot springs, and is expected to become a new energy-harvesting device. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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50 pages, 10643 KiB  

Open AccessReview

Thermoelectric Materials and Applications: A Review

by Matteo d’Angelo, Carmen Galassi and Nora Lecis

Energies 2023, 16(17), 6409; https://doi.org/10.3390/en16176409 - 04 Sep 2023

Cited by 6 | Viewed by 4492

Abstract

Solid-state energy conversion has been established as one of the most promising solutions to address the issues related to conventional energy generation. Thermoelectric materials allow direct energy conversion without moving parts and being deprived of greenhouse gases emission, employing lightweight and quiet devices. [...] Read more.

Solid-state energy conversion has been established as one of the most promising solutions to address the issues related to conventional energy generation. Thermoelectric materials allow direct energy conversion without moving parts and being deprived of greenhouse gases emission, employing lightweight and quiet devices. Current applications, main thermoelectric material classes, and manufacturing methods are the topics of this work; the discussion revolves around the crucial need for highly performing materials in the mid-temperature range, and around the development of more scalable fabrication technologies. The different manufacturing methods for thermoelectric bulk materials and films are also discussed. Small-scale technologies are generating increasing interest in research; the high potential of aerosol jet printing is highlighted, stressing the many advantages of this technology. A promising approach to scale the production of miniaturized thermoelectric devices that combines high energy ball milling and aerosol jet printing is proposed in the conclusion. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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Supplementary File 1 (ZIP, 1012 KiB)

14 pages, 5991 KiB  

Open AccessArticle

An Automatic Apparatus for Simultaneous Measurement of Seebeck Coefficient and Electrical Resistivity

by Ruifeng Xiong, Saeed Masoumi and Amir Pakdel

Energies 2023, 16(17), 6319; https://doi.org/10.3390/en16176319 - 31 Aug 2023

Cited by 2 | Viewed by 945

Abstract

A fully automated experimental system was designed for simultaneous measurement of the Seebeck coefficient and electrical resistivity of thermoelectric materials in bulk form. The system incorporates a straightforward and easily fabricated sample holder along with commercially available electronic instrument components. The sample holder [...] Read more.

A fully automated experimental system was designed for simultaneous measurement of the Seebeck coefficient and electrical resistivity of thermoelectric materials in bulk form. The system incorporates a straightforward and easily fabricated sample holder along with commercially available electronic instrument components. The sample holder showcases a compact design that utilizes two Peltier module heaters to induce sample heating and generate the required temperature gradient. System automation and control are achieved through the implementation of a LabView program. The Seebeck voltage and resistance of the sample (under specified temperature conditions) are determined using I–V measurements. The Seebeck voltage and resistance of the sample correspond to the intercept and slope of the I–V characteristic diagram in the four-point probe method, respectively. To verify the accuracy and reliability of the developed apparatus, a variety of experiments were performed on N-type and P-type bismuth telluride samples. The measurement results closely matched those obtained from commercial systems, with an overall data difference of less than 10% for both the Seebeck coefficient and resistivity measurements. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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Supplementary File 1 (ZIP, 1205 KiB)

10 pages, 3558 KiB  

Open AccessArticle

Structural Characterization and Thermoelectric Properties of Br-Doped AgSn_m[Sb_0.8Bi_0.2]Te_2+m Systems

by Daniela Delgado, Silvana Moris, Paulina Valencia-Gálvez, María Luisa López, Inmaculada Álvarez-Serrano, Graeme R. Blake and Antonio Galdámez

Materials 2023, 16(15), 5213; https://doi.org/10.3390/ma16155213 - 25 Jul 2023

Cited by 1 | Viewed by 762

Abstract

Herein, we report the synthesis, structural and microstructural characterization, and thermoelectric properties of AgSn_m[Sb_0.8Bi_0.2]Te_2+m and Br-doped telluride systems. These compounds were prepared by solid-state reaction at high temperature. Powder X-ray diffraction data reveal that these [...] Read more.

Herein, we report the synthesis, structural and microstructural characterization, and thermoelectric properties of AgSn_m[Sb_0.8Bi_0.2]Te_2+m and Br-doped telluride systems. These compounds were prepared by solid-state reaction at high temperature. Powder X-ray diffraction data reveal that these samples exhibit crystal structures related to the NaCl-type lattice. The microstructures and morphologies are investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), and high-resolution transmission electron microscopy (HRTEM). Positive values of the Seebeck coefficient (S) indicate that the transport properties are dominated by holes. The S of undoped AgSn_m[Sb_0.8Bi_0.2]Te_2+m ranges from +40 to 57 μV·K⁻¹. Br-doped samples with m = 2 show S values of +74 μV·K⁻¹ at RT, and the Seebeck coefficient increases almost linearly with increasing temperature. The total thermal conductivity (κ_tot) monotonically increases with increasing temperature (10–300 K). The κ_tot values of undoped AgSn_m[Sb_0.8Bi_0.2]Te_2+m are ~1.8 W m⁻¹ K⁻¹ (m = 4) and ~1.0 W m⁻¹ K⁻¹ (m = 2) at 300 K. The electrical conductivity (σ) decreases almost linearly with increasing temperature, indicating metal-like behavior. The ZT value increases as a function of temperature. A maximum ZT value of ~0.07 is achieved at room temperature for the Br-doped phase with m = 4. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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Supplementary File 1 (ZIP, 5337 KiB)

12 pages, 5912 KiB  

Open AccessArticle

Investigation of the Effect of Double-Filler Atoms on the Thermoelectric Properties of Ce-YbCo₄Sb₁₂

by Nguyen Vu Binh, Nguyen Van Du, Nayoung Lee, Minji Kang, So Hyeon Ryu, Munhwi Lee, Deokcheol Seo, Woo Hyun Nam, Jong Wook Roh, Soonil Lee, Se Yun Kim, Sang-Mo Koo, Weon Ho Shin and Jung Young Cho

Materials 2023, 16(10), 3819; https://doi.org/10.3390/ma16103819 - 18 May 2023

Viewed by 1095

Abstract

Skutterudite compounds have been studied as potential thermoelectric materials due to their high thermoelectric efficiency, which makes them attractive candidates for applications in thermoelectric power generation. In this study, the effects of double-filling on the thermoelectric properties of the Ce_xYb_0.2−x [...] Read more.

Skutterudite compounds have been studied as potential thermoelectric materials due to their high thermoelectric efficiency, which makes them attractive candidates for applications in thermoelectric power generation. In this study, the effects of double-filling on the thermoelectric properties of the Ce_xYb_0.2−xCo₄Sb₁₂ skutterudite material system were investigated through the process of melt spinning and spark plasma sintering (SPS). By replacing Yb with Ce, the carrier concentration was compensated for by the extra electron from Ce donors, leading to optimized electrical conductivity, Seebeck coefficient, and power factor of the Ce_xYb_0.2−xCo₄Sb₁₂ system. However, at high temperatures, the power factor showed a downturn due to bipolar conduction in the intrinsic conduction regime. The lattice thermal conductivity of the Ce_xYb_0.2−xCo₄Sb₁₂ skutterudite system was clearly suppressed in the range between 0.025 and 0.1 for Ce content, due to the introduction of the dual phonon scattering center from Ce and Yb fillers. The highest ZT value of 1.15 at 750 K was achieved for the Ce_0.05Yb_0.15Co₄Sb₁₂ sample. The thermoelectric properties could be further improved by controlling the secondary phase formation of CoSb₂ in this double-filled skutterudite system. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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15 pages, 4839 KiB  

Open AccessArticle

Investigations on Bi Doped Cu₂Se Prepared by Solid State Reaction Technique for Thermoelectric Applications

by Chaithanya Purushottam Bhat, Anusha, Aninamol Ani, U. Deepika Shanubhogue, P. Poornesh, Ashok Rao and Saikat Chattopadhyay

Energies 2023, 16(7), 3010; https://doi.org/10.3390/en16073010 - 25 Mar 2023

Cited by 2 | Viewed by 1556

Abstract

The influence of Bi doping on the structural and thermoelectric properties of Cu₂Se is presented in this work. Cu_2−xBi_xSe (x = 0.00, 0.004, 0.008, 0.012) samples were prepared using conventional solid-state reaction techniques. According to room temperature [...] Read more.

The influence of Bi doping on the structural and thermoelectric properties of Cu₂Se is presented in this work. Cu_2−xBi_xSe (x = 0.00, 0.004, 0.008, 0.012) samples were prepared using conventional solid-state reaction techniques. According to room temperature XRD results, Cu_2−xBi_xSe samples have a monoclinic crystal structure. Doping Bi to the Cu site acts as a donor, lowering the hole concentration, except for the sample with x = 0.004. The resistivity of the Cu_2−xBi_xSe sample increases with an increase in Bi content. Seebeck coefficient data confirm that the holes are the charge carriers in Cu_2−xBi_xSe samples. At 700 K, the Cu_1.988Bi_0.012Se sample has the highest power factor of 1474 μWm⁻¹K⁻², showing great potential in developing high-performance Cu₂Se based thermoelectric materials. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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12 pages, 3296 KiB  

Open AccessArticle

Application of Thermal Energy Harvesting from Photovoltaic Panels

by Hasan Demir

Energies 2022, 15(21), 8211; https://doi.org/10.3390/en15218211 - 03 Nov 2022

Cited by 2 | Viewed by 1373

Abstract

This paper describes a newly developed system for harvesting thermoelectric energy from photovoltaic panels. This system helps to power monitoring systems for photovoltaic panels (PVs) in locations where there is no energy source using waste thermal energy from PVs exposed to the sun’s [...] Read more.

This paper describes a newly developed system for harvesting thermoelectric energy from photovoltaic panels. This system helps to power monitoring systems for photovoltaic panels (PVs) in locations where there is no energy source using waste thermal energy from PVs exposed to the sun’s rays. In the study described here, the thermal energy from a PV panel was captured and transferred to a thermoelectric generator (TEG). A temperature gradient was created by reducing the temperature using an aluminium heat sink in ambient weather conditions. This temperature gradient was used to generate electricity via two TEGs. In field tests carried out in April, in Aksaray province in central Turkey, the maximum temperature gradient due to solar radiation was measured as 21.08 °C. The harvested energy was increased to a usable level of 4.1 V using a DC-to-DC converter and stored in a li-ion rechargeable battery. The maximum charge current level of the battery was 147 µA. The maximum harvested energy was 458.64 mW, and a stable level of around 350 mW was achieved. The experimental operation of the prototype system was carried out in stable weather conditions; however, weather and climatic conditions greatly affect levels of energy harvested as a result of changing temperature gradients. The energy obtained with the prototype may reduce the battery maintenance costs of PV monitoring systems and lead to the development of new such systems which cannot presently be used due to a lack of energy. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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10 pages, 1622 KiB  

Open AccessArticle

Thermoelectric Micro-Scale Generation by Carbonaceous Devices

by Francesco Miccio

Energies 2022, 15(21), 8105; https://doi.org/10.3390/en15218105 - 31 Oct 2022

Viewed by 979

Abstract

The paper reports on research focused on the use of largely available carbonaceous materials, such as graphite, carbon black and chars, as thermoelectric materials for micro-generation at high temperature. The key feature is the possibility to ignite the thermoelectric device to self-sustain electric [...] Read more.

The paper reports on research focused on the use of largely available carbonaceous materials, such as graphite, carbon black and chars, as thermoelectric materials for micro-generation at high temperature. The key feature is the possibility to ignite the thermoelectric device to self-sustain electric generation. The results of the tests performed with such materials, under both cold and hot conditions, showed that a significant change of the electromotive force, with absolute increase up to three orders of magnitude, occurred under hot conditions with flame irradiation, achieving measured values of electromotive force up to 55 mV, in the best case. Monoliths based on biomass chars and covered with a layer of gunpowder gave rise to similar variation of the Seebeck coefficient, as the case of the flame exposed samples. This result confirms the basic idea of the investigation and the possibility of generating an electrical peak in a self-sufficient combustion thermoelectric device with power up to 1.0 W. A theoretical assessment has been proposed to provide an interpretation of the observed phenomenology, which is related to the non-linear dependence of the material properties on temperature, in particular the Seebeck coefficient and thermal conductivity. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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Supplementary File 1 (ZIP, 209 KiB)

12 pages, 3609 KiB  

Open AccessArticle

First-Principles Study of Silicon–Tin Alloys as a High-Temperature Thermoelectric Material

by Shan Huang, Suiting Ning and Rui Xiong

Materials 2022, 15(12), 4107; https://doi.org/10.3390/ma15124107 - 09 Jun 2022

Cited by 3 | Viewed by 1846

Abstract

Silicon–germanium (SiGe) alloys have sparked a great deal of attention due to their exceptional high-temperature thermoelectric properties. Significant effort has been expended in the quest for high-temperature thermoelectric materials. Combining density functional theory and electron–phonon coupling theory, it was discovered that silicon–tin (SiSn) [...] Read more.

Silicon–germanium (SiGe) alloys have sparked a great deal of attention due to their exceptional high-temperature thermoelectric properties. Significant effort has been expended in the quest for high-temperature thermoelectric materials. Combining density functional theory and electron–phonon coupling theory, it was discovered that silicon–tin (SiSn) alloys have remarkable high-temperature thermoelectric performance. SiSn alloys have a figure of merit above 2.0 at 800 K, resulting from their high conduction band convergence and low lattice thermal conductivity. Further evaluations reveal that Si_0.75Sn_0.25 is the best choice for developing the optimum ratio as a thermoelectric material. These findings will provide a basis for further studies on SiSn alloys as a potential new class of high-performance thermoelectric materials. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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7 pages, 1874 KiB  

Open AccessArticle

Europium Clustering and Glassy Magnetic Behavior in Inorganic Clathrate-VIII Eu₈Ga₁₆Ge₃₀

by Nicolás Pérez, Manaswini Sahoo, Gabi Schierning, Kornelius Nielsch and George S. Nolas

Materials 2022, 15(10), 3439; https://doi.org/10.3390/ma15103439 - 10 May 2022

Cited by 1 | Viewed by 1425

Abstract

The temperature- and field-dependent, electrical and thermal properties of inorganic clathrate-VIII Eu₈Ga₁₆Ge₃₀ were investigated. The type VIII clathrates were obtained from the melt of elements as reported previously. Specifically, the electrical resistivity data show hysteretic magnetoresistance at low [...] Read more.

The temperature- and field-dependent, electrical and thermal properties of inorganic clathrate-VIII Eu₈Ga₁₆Ge₃₀ were investigated. The type VIII clathrates were obtained from the melt of elements as reported previously. Specifically, the electrical resistivity data show hysteretic magnetoresistance at low temperatures, and the Seebeck coefficient and Hall data indicate magnetic interactions that affect the electronic structure in this material. Heat capacity and thermal conductivity data corroborate these findings and reveal the complex behavior due to Eu²⁺ magnetic ordering and clustering from approximately 13 to 4 K. Moreover, the low-frequency dynamic response indicates Eu₈Ga₁₆Ge₃₀ to be a glassy magnetic system. In addition to advancing our fundamental understanding of the physical properties of this material, our results can be used to further the research for potential applications of interest in the fields of magnetocalorics or thermoelectrics. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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Supplementary File 1 (ZIP, 110102 KiB)

18 pages, 6153 KiB  

Open AccessArticle

Ionic Gelatin-Based Flexible Thermoelectric Generator with Scalability for Human Body Heat Harvesting

by Shucheng Wang, Liuyang Han, Hanxiao Liu, Ying Dong and Xiaohao Wang

Energies 2022, 15(9), 3441; https://doi.org/10.3390/en15093441 - 08 May 2022

Cited by 4 | Viewed by 2115

Abstract

The prosperity of intelligent wearables brings an increasingly critical problem of power supply. Regular rechargeable lithium or disposable button batteries have some problems, such as limited capacity, frequent replacement, environmental pollution, etc. Wearable energy harvester (WEH) can fundamentally solve these problems. Among WEHs, [...] Read more.

The prosperity of intelligent wearables brings an increasingly critical problem of power supply. Regular rechargeable lithium or disposable button batteries have some problems, such as limited capacity, frequent replacement, environmental pollution, etc. Wearable energy harvester (WEH) can fundamentally solve these problems. Among WEHs, thermoelectric generator (TEG) is a promising option due to its independence of light condition or the motion of the wearer, and thermoelectric conversion (TEC) has the characteristics of quietness and continuity. Therefore, TEG has become a suitable choice for harvesting low-grade heat energy such as human body heat. Ionic thermoelectric gel (iTEG) has the advantages of a large Seebeck coefficient, freely defined shape and size, low processing cost, wide material sources, easy encapsulation, etc. In this paper, the gelatin-based iTEG is regulated and optimized by silica nanoparticles (SiO₂ NPs). The optimal compound quantity of SiO₂ NPs is determined, and the optimization mechanism is discussed through a series of characterization tests. Based on the iTEG, a kind of scalable flexible TEGs is proposed, and its preparation method is described in detail. A small wristband TEG (STEG) was made, and its Seebeck coefficient is 74.5 mV/K. Its bendability and stretchability were verified, and the impedance matching experiment was carried out. By charging a capacitor, the STEG successfully lights up an LED at a temperature difference (ΔT) of ~15.5 K. Subsequently, a large extended oversleeve TEG (LTEG) was prepared, and a set of heat sinks was added at the cooling end of the LTEG. Being worn on a volunteer’s forearm, the LTEG output a voltage of more than 3 V at ~20 °C. Through storing the converted energy in a capacitor, the LTEG directly drove a calculator without a DC–DC booster. The proposed iTEG and TEGs in this paper have the prospect of mass production, extending to people’s clothes, harvesting human body heat and directly powering wearable electronics. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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18 pages, 5003 KiB  

Open AccessArticle

Advantage of a Thermoelectric Generator with Hybridization of Segmented Materials and Irregularly Variable Cross-Section Design

by Ye-Qi Zhang, Jiao Sun, Guang-Xu Wang and Tian-Hu Wang

Energies 2022, 15(8), 2944; https://doi.org/10.3390/en15082944 - 17 Apr 2022

Cited by 7 | Viewed by 2193

Abstract

As a direct energy converter between heat and electricity, thermoelectric generators (TEGs) have potential applications including recovery of waste heat, and solar thermoelectric power generation. Geometric parameter and material are two critical factors to improve the TEG performance. However, the strategies base on [...] Read more.

As a direct energy converter between heat and electricity, thermoelectric generators (TEGs) have potential applications including recovery of waste heat, and solar thermoelectric power generation. Geometric parameter and material are two critical factors to improve the TEG performance. However, the strategies base on structure design and material development are always separated. There are limited studies on the effects of consolidating them simultaneously. Here, an idea of segmented material coupled with irregularly variable cross-section design was conceived to further improve the TEG output power. The performance of TEGs with rectangular leg, segmented leg, variable cross-sectional leg, and the new design are compared. The coupling effects between various mechanisms are revealed, which are responsible for the superior performance provided by the developed design. Based on this knowledge, a multiparameters optimization was performed through the genetic algorithm to reach the optimal combination of design parameters. The results show that, with a constraint of certain material volume, the optimal performance of the TEG can be further enhanced by coupling segmented material and irregularly variable cross-section design. An improvement of 51.71% was achieved when compared with the conventional counterpart. This work offers a simple route to enhance the TEG performance when the device materials are specified, without an increase in the cost of manufacturing. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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12 pages, 6286 KiB  

Open AccessArticle

Reclaiming Power Potential from Low Temperature Waste Heat by Thermomagnetic Heat Engines

by Yeongmin Kim, Muhammad Uzair Mehmood, Hyun Joo Han, Yu Jin Kim, Seung Jin Oh and Sang-Hoon Lim

Energies 2022, 15(8), 2817; https://doi.org/10.3390/en15082817 - 12 Apr 2022

Cited by 2 | Viewed by 1834

Abstract

Thermomagnetic heat engines were designed, constructed, and tested, where numbers of gadolinium (Gd) blocks were used to exploit low temperature waste heat. Gadolinium is a rare earth material whose magnetic property changes with temperature, altering between ferromagnetic and paramagnetic. A motion develops in [...] Read more.

Thermomagnetic heat engines were designed, constructed, and tested, where numbers of gadolinium (Gd) blocks were used to exploit low temperature waste heat. Gadolinium is a rare earth material whose magnetic property changes with temperature, altering between ferromagnetic and paramagnetic. A motion develops in the thermomagnetic heat engine as Gd blocks are exposed to different temperatures causing changes in their magnetic property. A change in the magnetic property of any Gd block is directly related to the resultant torque driving the thermomagnetic heat engine for power production. Among heat engines studied to date, the cylindrical thermomagnetic heat engine was able to develop a maximum mechanical power of 1.1 W at a temperature difference of 45 °C between hot and cold thermal resources. Furthermore, depending on the effectiveness of an electromagnetic generator (EMG) combined with a triboelectric nanogenerator (TENG), the electric power output can be notably improved. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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34 pages, 8508 KiB  

Open AccessReview

Towards Integration of Two-Dimensional Hexagonal Boron Nitride (2D h-BN) in Energy Conversion and Storage Devices

by Shayan Angizi, Sayed Ali Ahmad Alem and Amir Pakdel

Energies 2022, 15(3), 1162; https://doi.org/10.3390/en15031162 - 04 Feb 2022

Cited by 20 | Viewed by 4284

Abstract

The prominence of two-dimensional hexagonal boron nitride (2D h-BN) nanomaterials in the energy industry has recently grown rapidly due to their broad applications in newly developed energy systems. This was necessitated as a response to the demand for mechanically and chemically stable platforms [...] Read more.

The prominence of two-dimensional hexagonal boron nitride (2D h-BN) nanomaterials in the energy industry has recently grown rapidly due to their broad applications in newly developed energy systems. This was necessitated as a response to the demand for mechanically and chemically stable platforms with superior thermal conductivity for incorporation in next-generation energy devices. Conventionally, the electrical insulation and surface inertness of 2D h-BN limited their large integration in the energy industry. However, progress on surface modification, doping, tailoring the edge chemistry, and hybridization with other nanomaterials paved the way to go beyond those conventional characteristics. The current application range, from various energy conversion methods (e.g., thermoelectrics) to energy storage (e.g., batteries), demonstrates the versatility of 2D h-BN nanomaterials for the future energy industry. In this review, the most recent research breakthroughs on 2D h-BN nanomaterials used in energy-based applications are discussed, and future opportunities and challenges are assessed. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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15 pages, 5524 KiB  

Open AccessArticle

Research on Module Layout and Module Coverage of an Automobile Exhaust Thermoelectric Power Generation System

by Weiqi Zhou, Jiasheng Yang, Qing Qin, Jiahao Zhu, Shiyu Xu, Ding Luo and Ruochen Wang

Energies 2022, 15(3), 987; https://doi.org/10.3390/en15030987 - 28 Jan 2022

Cited by 4 | Viewed by 2095

Abstract

Due to the low efficiency of thermoelectric generators (TEGs), many scholars have focused on the structural optimization of TEGs rather than on the optimization of the layout of thermoelectric modules. We aimed to investigate the effect of module layout on the output power [...] Read more.

Due to the low efficiency of thermoelectric generators (TEGs), many scholars have focused on the structural optimization of TEGs rather than on the optimization of the layout of thermoelectric modules. We aimed to investigate the effect of module layout on the output power of an automotive exhaust thermoelectric power generation system. The module spacing and module coverage ratio were compared under different working conditions based on a numerical simulation. The results show that, under high-temperature conditions, when the module spacing expands from 5 mm to 35 mm, the output power growth rate of modules of different sizes ranges between 8% and 9%. Moreover, under low-temperature conditions, a high coverage ratio of modules will not increase the total output power but, instead, make it decline. In fact, choosing a larger-size module can improve the temperature uniformity, thereby increasing the output power of the automotive thermoelectric power generation system. Hence, the present study has verified that, under different working conditions, different module layouts and module coverage ratios have an impact on the output power of the thermoelectric power generation system, which sheds new light on the improvement of automotive thermoelectric power generation systems. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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9 pages, 396 KiB  

Open AccessArticle

Work Measurement in OPEN Quantum System

by Youyang Xu

Entropy 2022, 24(2), 180; https://doi.org/10.3390/e24020180 - 25 Jan 2022

Cited by 1 | Viewed by 1906

Abstract

Work is an important quantity in thermodynamics. In a closed quanutm system, the two-point energy measurements can be applied to measure the work but cannot be utilized in an open quantum system. With the two-point energy measurements, it has been shown that the [...] Read more.

Work is an important quantity in thermodynamics. In a closed quanutm system, the two-point energy measurements can be applied to measure the work but cannot be utilized in an open quantum system. With the two-point energy measurements, it has been shown that the work fluctuation satisfies the Jarzynski equality. We propose a scheme to measure the work in an open quantum system through the technique of reservoir engineering. Based on this scheme, we show that the work fluctuation in open quantum system may violate the Jarzynski equality. We apply our scheme to a two-level atom coupled to an engineered reservoir and numerically justify the general results, especially demonstrating that the second law of thermodynamics can be violated. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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Supplementary material:
Supplementary File 1 (ZIP, 1525 KiB)

15 pages, 4396 KiB  

Open AccessArticle

Impact of the Dopant Species on the Thermomechanical Material Properties of Thermoelectric Mg₂Si_0.3Sn_0.7

by Gustavo Castillo-Hernández, Eckhard Müller and Johannes de Boor

Materials 2022, 15(3), 779; https://doi.org/10.3390/ma15030779 - 20 Jan 2022

Cited by 5 | Viewed by 1584

Abstract

Thermoelectric generators are an excellent option for waste heat reuse. Materials for such devices have seen their thermoelectric properties improving constantly. The functioning of a generator, however, does not only depend on thermoelectric properties. Thermal and mechanical properties play a decisive role in [...] Read more.

Thermoelectric generators are an excellent option for waste heat reuse. Materials for such devices have seen their thermoelectric properties improving constantly. The functioning of a generator, however, does not only depend on thermoelectric properties. Thermal and mechanical properties play a decisive role in the feasibility of any thermoelectric generator. To shed light on the properties exhibited by thermoelectric materials, we present the temperature dependent characterization of Young’s modulus and coefficient of thermal expansion for Mg₂Si_0.3Sn_0.7. Comparing undoped to Bi-doped n-type and Li-doped p-type material, we investigated the influence of doping in the relevant temperature regime and found the influences to be minor, proving similar properties for n- and p-type. We found a Young’s modulus of 84 GPa for the p-type and 83 GPa for the n-type, similar to that of the undoped compound with 85 GPa. The thermal expansion coefficients of undoped, as well as n- and p-type were equally similar with values ranging from 16.5 to 17.5 × 10⁻⁶ 1/K. A phase analysis was performed to further compare the two materials, finding a similar phase distribution and microstructure. Finally, using the gathered data, estimations on the possible thermally induced stresses under a temperature difference are provided to evaluate the relevance of knowing temperature dependent thermal and mechanical properties. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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25 pages, 8202 KiB  

Open AccessArticle

Development of a Thermal Energy Harvesting Converter with Multiple Inputs and an Isolated Output

by Yeu-Torng Yau, Kuo-Ing Hwu and Jenn-Jong Shieh

Energies 2022, 15(1), 273; https://doi.org/10.3390/en15010273 - 31 Dec 2021

Cited by 1 | Viewed by 1734

Abstract

In this paper, an isolated multi-input single-output (MISO) converter is developed and applied to a thermoelectric energy conversion system to harvest thermal energy. The thermoelectric generators have individual maximum power point tracking functions. Furthermore, such a converter has a high step-up voltage conversion [...] Read more.

In this paper, an isolated multi-input single-output (MISO) converter is developed and applied to a thermoelectric energy conversion system to harvest thermal energy. The thermoelectric generators have individual maximum power point tracking functions. Furthermore, such a converter has a high step-up voltage conversion ratio. In addition, the presented converter is imposed on the thermoelectric energy conversion system with the three-point weighting strategy adopted to realize the maximum power point tracking (MPPT). In this paper, the basic principles of this converter are first described and analyzed, and finally some simulated and experimental results are offered to verify the feasibility and effectiveness of such a thermal energy harvesting system. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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15 pages, 5906 KiB  

Open AccessArticle

Corrosion Behavior in Volcanic Soils: In Search of Candidate Materials for Thermoelectric Devices

by Carlos Berlanga-Labari, Leyre Catalán, José F. Palacio, Gurutze Pérez and David Astrain

Materials 2021, 14(24), 7657; https://doi.org/10.3390/ma14247657 - 12 Dec 2021

Cited by 2 | Viewed by 1957

Abstract

Thermoelectric generators have emerged as an excellent solution for the energy supply of volcanic monitoring stations due to their compactness and continuous power generation. Nevertheless, in order to become a completely viable solution, it is necessary to ensure that their materials are able [...] Read more.

Thermoelectric generators have emerged as an excellent solution for the energy supply of volcanic monitoring stations due to their compactness and continuous power generation. Nevertheless, in order to become a completely viable solution, it is necessary to ensure that their materials are able to resist in the acidic environment characteristic of volcanoes. Hence, the main objective of this work is to study the resistance to corrosion of six different metallic materials that are candidates for use in the heat exchangers. For this purpose, the metal probes have been buried for one year in the soil of the Teide volcano (Spain) and their corrosion behavior has been evaluated by using different techniques (OM, SEM, and XRD). The results have shown excessive corrosion damage to the copper, brass, and galvanized steel tubes. After evaluating the corrosion behavior and thermoelectric performance, AISI 304 and AISI 316 stainless steels are proposed for use as heat exchangers in thermoelectric devices in volcanic environments. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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29 pages, 13044 KiB  

Open AccessReview

Water-Cooled Thermoelectric Generators for Improved Net Output Power: A Review

by Björn Pfeiffelmann, Ali Cemal Benim and Franz Joos

Energies 2021, 14(24), 8329; https://doi.org/10.3390/en14248329 - 10 Dec 2021

Cited by 13 | Viewed by 3088

Abstract

Thermoelectric generators (TEGs) have the ability to convert waste heat into electrical energy under unfavorable conditions and are becoming increasingly popular in academia, but have not yet achieved a broad commercial success, due to the still comparably low efficiency. To increase the efficiency [...] Read more.

Thermoelectric generators (TEGs) have the ability to convert waste heat into electrical energy under unfavorable conditions and are becoming increasingly popular in academia, but have not yet achieved a broad commercial success, due to the still comparably low efficiency. To increase the efficiency and economic viability of TEGs, research is performed on the materials on one hand and on the system connection on the other. In the latter case, the net output power of the cooling system plays a key role. At first glance, passive cooling seems preferable to active cooling because it does not affect the net electrical output power. However, as shown in the present review, the active cooling is to be preferred for net output power. The situation is similar in air and water-cooling. Even though air-cooling is easier to set up, the water-cooling should be preferred to achieve higher net output power. It is shown that microchannel cooling has similar hydraulic performance to conventional cooling and inserts increase the net output power of TEG. As the review reveals that active water-cooling should be the method of choice to achieve high net output power, it also shows that a careful optimization is necessary to exploit the potential. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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Supplementary material:
Supplementary File 1 (ZIP, 507 KiB)

11 pages, 2243 KiB  

Open AccessArticle

Composites between Perovskite and Layered Co-Based Oxides for Modification of the Thermoelectric Efficiency

by Sonya Harizanova, Eric Faulques, Benoit Corraze, Christophe Payen, Marcin Zając, Dorota Wilgocka-Ślęzak, Józef Korecki, Genoveva Atanasova and Radostina Stoyanova

Materials 2021, 14(22), 7019; https://doi.org/10.3390/ma14227019 - 19 Nov 2021

Cited by 4 | Viewed by 1820

Abstract

The common approach to modify the thermoelectric activity of oxides is based on the concept of selective metal substitution. Herein, we demonstrate an alternative approach based on the formation of multiphase composites, at which the individual components have distinctions in the electric and [...] Read more.

The common approach to modify the thermoelectric activity of oxides is based on the concept of selective metal substitution. Herein, we demonstrate an alternative approach based on the formation of multiphase composites, at which the individual components have distinctions in the electric and thermal conductivities. The proof-of-concept includes the formation of multiphase composites between well-defined thermoelectric Co-based oxides: Ni, Fe co-substituted perovskite, LaCo_0.8Ni_0.1Fe_0.1O₃ (LCO), and misfit layered Ca₃Co₄O₉. The interfacial chemical and electrical properties of composites are probed with the means of SEM, PEEM/XAS, and XPS tools, as well as the magnetic susceptibility measurements. The thermoelectric power of the multiphase composites is evaluated by the dimensionless figure of merit, ZT, calculated from the independently measured electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (λ). It has been demonstrated that the magnitude’s electric and thermal conductivities depend more significantly on the composite interfaces than the Seebeck coefficient values. As a result, the highest thermoelectric activity is observed at the composite richer on the perovskite (i.e., ZT = 0.34 at 298 K). Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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21 pages, 6695 KiB  

Open AccessReview

Thermal Management Systems and Waste Heat Recycling by Thermoelectric Generators—An Overview

by Sadeq Hooshmand Zaferani, Mehdi Jafarian, Daryoosh Vashaee and Reza Ghomashchi

Energies 2021, 14(18), 5646; https://doi.org/10.3390/en14185646 - 08 Sep 2021

Cited by 23 | Viewed by 4470

Abstract

With the fast evolution in greenhouse gas (GHG) emissions (e.g., ${\mathrm{CO}}_2$,${\mathrm{N}}_2\mathrm{O}$) caused by fossil fuel combustion and global warming, climate change has been identified as a critical threat to the sustainable development of human society, public [...] Read more.

With the fast evolution in greenhouse gas (GHG) emissions (e.g., ${\mathrm{CO}}_2$,${\mathrm{N}}_2\mathrm{O}$) caused by fossil fuel combustion and global warming, climate change has been identified as a critical threat to the sustainable development of human society, public health, and the environment. To reduce GHG emissions, besides minimizing waste heat production at the source, an integrated approach should be adopted for waste heat management, namely, waste heat collection and recycling. One solution to enable waste heat capture and conversion into useful energy forms (e.g., electricity) is employing solid-state energy converters, such as thermoelectric generators (TEGs). The simplicity of thermoelectric generators enables them to be applied in various industries, specifically those that generate heat as the primary waste product at a temperature of several hundred degrees. Nevertheless, thermoelectric generators can be used over a broad range of temperatures for various applications; for example, at low temperatures for human body heat harvesting, at mid-temperature for automobile exhaust recovery systems, and at high temperatures for cement industries, concentrated solar heat exchangers, or NASA exploration rovers. We present the trends in the development of thermoelectric devices used for thermal management and waste heat recovery. In addition, a brief account is presented on the scientific development of TE materials with the various approaches implemented to improve the conversion efficiency of thermoelectric compounds through manipulation of Figure of Merit, a unitless factor indicative of TE conversion efficiency. Finally, as a case study, work on waste heat recovery from rotary cement kiln reactors is evaluated and discussed. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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13 pages, 2943 KiB  

Open AccessArticle

Structural Design Optimization of Micro-Thermoelectric Generator for Wearable Biomedical Devices

by Amit Tanwar, Swatchith Lal and Kafil M. Razeeb

Energies 2021, 14(8), 2339; https://doi.org/10.3390/en14082339 - 20 Apr 2021

Cited by 21 | Viewed by 3333

Abstract

Wearable sensors to monitor vital health are becoming increasingly popular both in our daily lives and in medical diagnostics. The human body being a huge source of thermal energy makes it interesting to harvest this energy to power such wearables. Thermoelectric devices are [...] Read more.

Wearable sensors to monitor vital health are becoming increasingly popular both in our daily lives and in medical diagnostics. The human body being a huge source of thermal energy makes it interesting to harvest this energy to power such wearables. Thermoelectric devices are capable of converting the abundantly available body heat into useful electrical energy using the Seebeck effect. However, high thermal resistance between the skin and the device leads to low-temperature gradients (2–10 K), making it difficult to generate useful power by this device. This study focuses on the design optimization of the micro-thermoelectric generator for such low-temperature applications and investigates the role of structural geometries in enhancing the overall power output. Electroplated p-type bismuth antimony telluride (BiSbTe) and n-type copper telluride (CuTe) materials’ properties are used in this study. All the simulations and design optimizations were completed following microfabrication constraints along with realistic temperature gradient scenarios. A series of structural optimizations were performed including the thermoelectric pillar geometries, interconnect contact material layers and fill factor of the overall device. The optimized structural design of the micro-thermoelectric device footprint of 4.5 × 3.5 mm², with 240 thermoelectric leg pairs, showcased a maximum power output of 0.796 mW and 3.18 mW when subjected to the low-temperature gradient of 5 K and 10 K, respectively. These output power values have high potential to pave the way of realizing future wearable devices. Full article

(This article belongs to the Topic Thermoelectric Energy Harvesting)

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