Thermoelectric Elements Research Articles

Rancang Bangun Pendingin Portable Dengan Menggunakan Konsumsi Daya Rendah

The need for air conditioning is currently increasing its use, especially with the global warming that occurs in every region. But there are still many that take into account the use of electrical power electrical energy required for this air conditioner. Therefore, in this study we will design a cooling device using peltier thermoelectric elements with low power electric power USAge by using 8 peltier elements to be combined in series-parallel to achieve more efficient power. Based on the result of series-parallel combination has been obtained 27,87 electric power. In this research tool more effective for long distance in this case that is 2 meter.

A review of thermoelectric ZnO nanostructured ceramics for energy recovery

The thermoelectric devices have the ability to convert heat energy into electrical energy without required moving components, having good reliability however their performance depends on material selections. The advances in the development of thermoelectric materials have highlighted to increase the technology’s energy efficiency and waste heat recovery potential at elevated temperatures. The fabrication of these thermoelectric materials depends on the type of these materials and the properties using to evaluate these kind of materials such as thermopower (Seebeck effect), electrical and thermal conductivities. Ceramic thermoelectric materials have attracted increased attention as an alternative approach to traditional thermoelectric materials. From these important thermoelectric ceramic materials that can be a candidate for n-type is ZnO doping, which have excellent thermal and chemical stability, as they are promising for high temperature power generator. This review is an effort to study the thermoelectric properties and elements doping related with zinc oxide nano-ceramic materials. Effective ZnO dopants and doping strategies to achieve high electrical and thermal conductivities and high carrier concentration are highlighted in this review to enable the advanced zinc oxide applications in thermoelectric power generation.

The fabrication of nanoscale Bi2Te3/Sb2Te3 multilayer thin film-based thermoelectric power chips

In this paper, we report our method of fabricating nanoscale multilayered Bi2Te3/Sb2Te3 thin film-based integrated thermoelectric devices, and detail the voltage and power produced by the device. The multilayered Bi2Te3/Sb2Te3 thin film was grown via e-beam evaporation; it had 20 alternating Bi2Te3- and Sb2Te3-layers, each layer being 1.5 nm thick. We characterized the film using high-resolution transmission electron microscopy (HRTEM), revealing its excellent cross-sectional structure without any obvious interface defects. The Bi2Te3/Sb2Te3 multilayer films were investigated by synchrotron X-ray scattering. An integrated device including 128 × 256 thermoelectric elements was fabricated from the multilayered film. An open-circuit voltage of 51 mV and a maximum power of 21 nW were produced from this 30 nm-thick Bi2Te3/Sb2Te3 multilayer TE device, and a temperature gradient of about 0.5 K/μm was established across the multilayered film. We found that the nanoscale multilayer structure significantly affects the voltage and power produced. The fabrication of the integrated thermoelectric devices is compatible to that of generating standard integrated circuits (ICs), and is scalable for producing higher voltage and power, or achieving solid-state cooling for on-chip applications.

First-principles simulation on thermoelectric propertiesof transition metal dichalcogenide monolayers

Thermoelectric properties of transition metal dichalcogenide (TMDC) monolayer models, such as Seebeck coefficient and lattice heat capacity, were simulated on the basis of first-principles calculations. The calculated Seebeck coefficients are appropriate for the thermoelectric element of all the TMDC monolayer models introduced in this study. In the MoX2/WX2 (X = S, Se, and Te) heterojunction structure, carrier electrons and holes are respectively distributed in the MoX2 and WX2 regions by adopting a common Fermi energy for both electronic structures. In particular, in the X = Te case, the practical carrier concentration with a large Seebeck coefficient can be evaluated without doping. The lattice heat capacities and their temperature dependence tendencies can be classified on the basis of the minimum frequencies of the optical modes. The quotient of the lattice thermal conductivity over the phonon relaxation time gives the temperature-independent specific values according to the kind of TMDC monolayer.

Filtration Gas Combustion in a Porous Ceramic Annular Burner for Thermoelectric Power Conversion

ABSTRACTA numerical study of the combustion of lean methane/air mixtures in a porous media burner is performed using novelty geometry, cylindrical annular space. The combustion process takes place in the porous space located between two pipes, which are filled with alumina beads of 5.6 mm diameter forming a porosity of 0.4. The outer tube diameter of 3.82 cm is isolated; meanwhile the inner tube of 2 cm in diameter is covered by a continuous set of thermoelectric elements (TE) for transforming heat energy into electricity. To achieve and maintain the proper temperature gradient on TE, convective heat losses are considered from the TE. Computer simulations focus on the two-dimensional (2D) temperature analysis and displacement dynamics of the combustion front inside the reactor, depending on the values of the filtration velocity (0.1 to 1.0 m/s), the heat loss coefficient from the internal cylinder (400–1500 W/m2/K), and the fuel equivalence ratio (0.06– 0.5). The conditions that maximized the overall performance of the process of energy conversion are: 0.7 m/s of the filtration velocity, 0.363 of the fuel equivalence ratio and 1500 W/(m2·K) of the heat transfer coefficient from the internal cylinder, to obtain 2.05 V electrical potential, 21 W of electrical power, and 5.64% of the overall process efficiency. The study shows that the cylindrical annular geometry can be used for converting the energy of combustion from lean gas mixtures into electricity, with a performance similar to the specified by manufacturers of thermoelectric elements (TE).

PENGARUH HAMBATAN INTERNAL TERHADAP DAYA OUTPUT ELEMEN TERMOELEKTRIK GENERATOR TIPE 10W-4V-40s

Thermoelectric generator Type 10W-4V-40s powered by Seebeck effect by utilizing temperature difference in both sides of the element. The hot side (Th) of a TEG element is placed on a stand made of Aluminum-Dural material and given a heat source derived from a heater, on the cold side (Tc) TEG element installed heatsink to reduce heat energy through the cold side and keep the temperature low. The measurement of output power (PL) is done by variation of RL from 0 Ω to 20 Ω under temperature difference conditions (ΔT) varies with constant Tc at 30ºC, the result of the research indicates that the output power (PL) of the thermoelectric element is maximum at RL = 1 Ω when the minimum load decreases and is proportional to the increase in RL resistance. The internal resistance value (Rint) of the TEG element increases in proportion to the magnitude of ΔT on both sides of the element, on Tc and Th at room temperature (30ºC) the value of Rint is 0.85 Ω and the maximum value at ΔT = 50ºC is 1,043 Ω. This indicates that the TEG element depends not only on ΔT on both sides of the module, but also depends on the amount of temperature range used.

Stable and low contact resistance electrical contacts for high temperature SiGe thermoelectric generators

The thermal stability and contact resistance of TaAlN thin films as electrical contacts to SiGe thermoelectric elements are reported. We demonstrate that a sharp interface is maintained after the device annealed at 800°C for over 100h, indicating that no interdiffusion takes place between TaAlN and SiGe. A specific contact resistivity of (2.1±1.3)×10−6Ω-cm2 for p-type SiGe and (2.8±1.6)×10−5 Ω-cm2 for n-type SiGe is demonstrated after the high temperature annealing. These results show that TaAlN is a promising contact material for high temperature thermoelectrics such as SiGe.

Transformer-Free, Off-the-Shelf Electrical Interface for Low-Voltage DC Energy Harvesting

Energy harvesting from various ambient energy sources keeps gaining interest to deal with the challenges arising from more and more widespread Internet of Things applications in consumer electronics and industrial applications such as remote sensing. However, available energy is scarce and designers must comply with small size package and thermal dissipation that inevitably lead to compromises. This paper presents a transformer-free and self-powered oscillator that can be directly powered from a very low dc voltage source such as a thermoelectric module and able to deliver dc bias output. Using off-the-shelves parts, such a design is less cumbersome and gives more freedom to designers while tailoring their circuits with respect to their applications. The oscillator consists of a modified Hartley oscillator including a supplementary capacitor that provides a bias voltage in its output. Theoretical analysis is validated through experimental measurements showing that the proposed solution could be deployed in buildings and/or wearable devices as small and cheap complete microgenerators using for example thermoelectric elements or microbial fuel cells.

Free-standing planar thermoelectric microrefrigerators based on nano-grained SiGe thin films for on-chip refrigeration

Rapidly increasing integration density in modern miniaturized microelectronic and optical devices stimulates the demands for low-power and fast-response on-chip refrigeration solutions. Thermoelectric microrefrigerators offer an attractive all-solid-state solution with many prominent merits such as high reliability, quick response, capability of cooling below ambient and good scalability. Conventional thermoelectric microrefrigerators widely adopt integrated-circuit (IC)-incompatible toxic heavy metal compounds such as Bi2Te3 as thermoelectric elements, making them unsuitable for on-chip integration. Here we developed single- and two-stage free-standing planar thermoelectric microrefrigerators based on nanograined SiGe thin films. The novel support-free design and the record high performance of the nanograined SiGe thin films lead to significant improvement in the cooling performance. A maximum cooling temperature of 10.3 K together with a response time of 16 ms has been achieved in the single-stage microrefrigerator with a power consumption of 56 μW near room temperature while a maximum cooling temperature of 11.2 K can be achieved in the two-stage refrigerator with 0.41 mW input power. The cooling temperatures of the SiGe microrefrigerators also improve with the increasing ambient temperature, reaching up to 15 K and 17 K for the single and two-stage microrefrigerators respectively at 340 K. To our best knowledge, this is the highest cooling temperature achieved in Si-based thermoelectric microrefrigerators so far. These SiGe thin-film devices can deliver cooling performances comparable to the records for traditional heavy-metal-based microrefrigerators while providing excellent IC compatibility and almost one to two orders of magnitude higher cooling temperature to power consumption ratios (184 K/mW), making them ideal candidates for low-power on-chip refrigeration.

An effective method of evaluating the device-level thermophysical properties and performance of micro-thermoelectric coolers

Despite the success of achieving thermoelectric materials with high figure of merit, precisely evaluating the performance of micro-thermoelectric coolers remains challenging at the microdevice level because of various interfacial effects and device construction. This study develops a method for the effective evaluation of the device-level thermophysical properties capturing various interfacial and size effects, and establishes a three-dimensional numerical model to evaluate the cooling performance of micro-thermoelectric coolers. The model is validated by the reported experimental data. The impact of interaction between boundary and size effects is captured in the investigation of Seebeck coefficient, thermal conductivity and electricity resistivity of the thermoelectric materials at the device-level. Contact resistances are also considered in analyzing the cooling performance. Results indicate that the device-level figure of merit decreases by 5–18.1% with decreased thermoelectric element thickness from 20 μm to 5 μm. The boundary effects considerably weaken the cooling performance of the microdevice, and a higher heat flux corresponds to a greater impact of boundary effects. Cooling temperature increases by 6.1 K due to the boundary effects when heat flux is 300 W/cm2, while the temperature difference decreases by 17.1%. Finally, the three-dimensional numerical model is performed to evaluate the cooling performance and optimal working condition of the micro-thermoelectric cooler. At heat flux of 300 W/cm2 and 200 W/cm2, the minimum cold side temperatures of 310.7 K and 287.3 K are predicted to be achieved at 11 μm/20 mA (Hte/I), 15 μm/16 mA, respectively.

Potential of energy recuperation in the exhaust gas of state of the art light duty vehicles with thermoelectric elements

About 30% of the fuel energy is lost in combustion engines to the exhaust gas. New development of thermoelectric materials allows to partly recuperating the lost heat. New Half-Heusler materials using only low-priced elements show promising performances for heat conversion in the temperature range of a vehicle exhaust. An investigation of the installation of Half-Heusler-based thermoelectric generators at the manifold and after the exhaust after-treatment system (ATS) of 4 light duty vehicles (2 gasolines and 2 diesels) has been made. Gas temperatures at the manifold and after the ATS were simulated based on measured data. These reach 800 °C and 600 °C respectively during a typical driving cycle. During the WLTC, an average of 100 W of electricity can be generated at the manifold and 30 W after the ATS, without adding specific heat transfer enhancing devices in the exhaust pipe. The geometric dimensions of the TEGs must be adapted in order to match the optimal thermal resistance according to their location in the exhaust and the vehicle type (differing heat flows and temperatures) to recuperate an optimal amount of energy.

Performance analyzes of an integrated phosphoric acid fuel cell and thermoelectric device system for power and cooling cogeneration

In addition to electricity generation, phosphoric acid fuel cell (PAFC) produces a significant amount of waste heat. In this study, a hybrid system mainly consisting of a PAFC, a thermoelectric generator, and a thermoelectric cooler is proposed to recover the produced waste heat aiming for performance enhancement. Considering thermodynamic and electrochemical irreversible losses within the system, an analytical relationship between the dimensionless electric current of the thermoelectric element and the current density of the PAFC is derived. Analytical formulas for power density and efficiency of the hybrid system are derived. The characteristics and the optimum criteria evaluating the performance parameters are revealed for the studied system. Numerical solutions show that the power density and efficiency of the hybrid system allow 2.3% and 2.8% larger than that of a stand-alone PAFC, respectively. The present hybrid system is found to be feasible and effective. Comprehensive parametric studies are conducted to analyze the effects of operating conditions and design parameters on the proposed system. The conclusions drawn can provide theoretical guidance for PAFC performance enhancements and system designs.

Enhanced Thermoelectric Properties of F4TCNQ Doped P3HT and Its Use as a Binder for Sb2Te3 Based Printed Thermoelectric Films

Flexible thermoelectric generators (FTEGs) are emerging energy harvesting devices that have generated recent research interest because of their scalability and low cost. The fabrication of FTEGs requires printing of thermoelectric elements on flexible substrates. The low thermal conductivity, solution processability, and low cost of polymers make them an attractive choice for flexible devices. A major challenge in their adoption is their very low electrical conductivity. The electrical conductivity of conjugated polymers can be improved by doping and addition of active particles. This article describes enhancements in the thermoelectric properties of poly(3-hexylthiophene) (P3HT) polymer using 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) as a dopant. The highest electrical conductivity obtained was 1.6 S/cm for 17 wt % dopant in the polymer. The highest Seebeck coefficient (102 μV/K) and power factor (1.6 μW/mK2) were also obtained for the same dopant concentration. As a result of using o...

Theoretical and Experimental Temperature Distribution along a Plate

Existing equations for the temperature distribution along a plate produced by a point heat source are analyzed. Experimental values are compared with theoretical results from a formula employed in the development of a thermoelectric element for borehole use. On that basis, the influence of the heat-transfer coefficient on the calculated temperature distribution is established. In order to ensure agreement between the distribution calculated by the proposed formula and the experimental distribution, the value of the heat-transfer must be corrected.

Numerical Study on Geometric Parameter effects of Power Generation Performances for Segmented Thermoelectric Generator

Thermoelectric generator (TEG) is a promising option in waste heat recovery with various advantages including nonmoving components, very low operating noise and overall high stability. However, low power generation efficiency of TEGs is still concerned for application in wider fields. The objective of the present study is to investigate the parameters affecting the performance and efficiency of segmented TEG. The physical parameters including length ratio, length-to-area ratio and thickness of conducting plate were considered. In addition, the effect of varying hot side temperature was analyzed. Performance of segmented TEG was compared based on the power generation and conversion efficiency. The results of the investigation showed that increasing Bi2Te3 length in the segmented TEG made up of Bi2Te3 and SiGe increased the maximum power generation and efficiency. As length-to-area ratio increased, the power generation decreased, however, efficiency increased slightly. In addition, as the hot side temperature increased from 150[Formula: see text]C to 650[Formula: see text]C, the power generation and efficiency both increased. Power generation and efficiency of segmented TEG increased when the conducting plate thickness was increased. The power generation and efficiency were 39.2% and 51.9% higher for TEG with asymmetrical element than TEG with symmetrical element showing that asymmetrical element would be better option for same thermoelectric element volume.

Fabrication and Testing of a Tubular Thermoelectric Module Based on Oxide Elements

A thermoelectric module with a tubular design, considered as particularly promising for energy recovery from hot exhaust gases of vehicles was fabricated and successfully tested under laboratory condition. The module included 24 functional oxide elements synthesized by conventional methods. Elements of p-type were made of cobalt-based oxide Ca2.7Bi0.3Co4O9, while n-type elements were produced from manganese-based oxide CaMn0.95Ta0.05O3. The module was assembled using silver paste and clamping mechanisms, with the thermoelectric elements electrically connected in series by metal plates (copper, silver) and placed around the hot tube. The output power of 138 mW was achieved under a temperature gradient of 430°C with a hot side temperature of 514°C. The tested module is characterized by an advantageous manufacturing factor of 0.87 at the contact resistance of 0.44 Ω, but a relatively low output power density per volume and per mass. Possible means by which the module’s operational characteristics could be improved are considered.

System-level Pareto frontiers for on-chip thermoelectric coolers

The continuous rise in heat dissipation of integrated circuits necessitates advanced thermal solutions to ensure system reliability and efficiency. Thermoelectric coolers are among the most promising techniques for dealing with localized on-chip hot spots. This study focuses on establishing a holistic optimization methodology for such thermoelectric coolers, in which a thermoelectric element’s thickness and the electrical current are optimized to minimize source temperature with respect to ambient, when the thermal and electrical parasitic effects are considered. It is found that when element thickness and electrical current are optimized for a given system architecture, a “heat flux vs. temperature difference” Pareto frontier curve is obtained, indicating that there is an optimum thickness and a corresponding optimum current that maximize the achievable temperature reduction while removing a particular heat flux. This methodology also provides the possible system level ΔT’s that can be achieved for a range of heat fluxes, defining the upper limits of thermoelectric cooling for that architecture. In this study, use was made of an extensive analytical model, which was verified using commercially available finite element analysis software. Through the optimization process, 3 pairs of master curves were generated, which were then used to compose the Pareto frontier for any given system architecture. Finally, a case study was performed to provide an in-depth demonstration of the optimization procedure for an example application.

Preparation of NiSi2 and application to thermoelectric silicide elements used as electrodes

ABSTRACTWe applied NiSi2 as an electrode for thermoelectric modules because NiSi2 has high electric conductivity and is expected to suppress the inter-diffusion of Si from MgSi2 and higher manganese silicide (HMS). The thermal expansion coefficient of NiSi2 is close to that of Mg2Si but differs from that of HMS. Therefore, to reduce thermal stress, we tried to insert a buffer layer consisting of HMS and NiSi2 for the interface between the HMS sintered body and the NiSi2 electrode. The NiSi2 was prepared by using spark plasma sintering (SPS) equipment. NiSi2 electrodes and gradients were formed and connected with the HMS by SPS treatment. Crack-free bonding was achieved by inserting gradients consisting of HMS and NiSi2. The inserted composite buffer layer reduced interface stress and interface resistance between HMS and NiSi2.

Duration of Thermal Stability and Mechanical Properties of Mg2Si/Cu Thermoelectric Joints

Preparing an effective and long-term reliable contact between a thermoelectric (TE) element and its electrode is a key issue in integrating TE elements into practical devices. In this work, Cu electrodes were bonded to Mg2Si by using the spark plasma sintering (SPS) technique. To investigate their thermal stability, Mg2Si/Cu joints were annealed in vacuum at different temperatures (500°C, 550°C, and 580°C) for different durations (24 h, 48 h, and 72 h). Scanning electron microscopy (SEM) images illustrated that an intermediate layer with thickness of approximately 10 μm developed between Mg2Si and Cu during the sintering process. Electron probe microanalysis (EPMA) indicated that Mg, Si, and Cu diffused into each other and formed a τ3-phase at the interlayer. After annealing at 500°C for 72 h, the Mg2Si/Cu joints still possessed good adhesion and showed no cracks; the thickness and the elemental fractions within the interlayer did not show an obvious difference due to the thermal treatment. The electrical contact resistance increased slightly while the shear strength of the Mg2Si/Cu joints decreased with increasing aging time. However, when increasing the annealing temperature to 550°C, cracks developed along the boundary of the intermediate layer close to the Cu layer. Severer cracks were observed with higher aging temperature of 580°C. Therefore, it is evident that the Mg2Si/Cu joints exhibited good thermal reliability with stable microstructure, relatively unchanged electrical contact, and sufficient bonding strength at operating temperatures below 500°C.

Enhancement of reproducibility and reliability in a high-performance flexible thermoelectric generator using screen-printed materials

Flexible thermoelectric generators (f-TEGs) have recently attracted significant attention because they can be applied to non-flat surfaces and used as semi-permanent power sources. The use of screen printing to fabricate f-TEGs would enable large-scale, mass production. To realize this aim, several hundred pairs of thermoelectric (TE) materials formed by screen printing must all exhibit uniform TE properties. However, parameter deviation commonly occurs in such batches because the materials formed by screen printing are usually crystallized in a large furnace or chamber. We report here a new crystallization process that avoids these problems while improving the output characteristics of the f-TEGs, using screen printed thermoelectric elements (sp-TEs). The sp-TEs were formed with a paste containing an excess of tellurium, which allowed a single-step crystallization process to be developed. The simplified process improved the low density associated with conventional sp-TE fabrication (to 6.23 g cm−3 for Bi.5Sb1.5Te3 and 6.43 g cm−3 for Bi2Te2.7Se.3), and reduced the deviation in TE parameters (Seebeck coefficient, electrical and thermal conductivity) to less than half of the conventional range. As a result, the highest material figure of merit (ZTMAT) values among sp-TEs was achieved for both p-type sp-TE (0.93 ± 0.020) and n-type (0.64 ± 0.025) at room temperature. F-TEGs consisting of 200 couples of the improved sp-TEs produced an output power density of 5.23 ± 0.2 mW/cm2 at a temperature difference (ΔT) of 25 K, demonstrating the feasibility of mass producing high-output f-TEGs with reliability and reproducibility.