Thermoelectric Generator Device Research Articles

Uninterrupted Self‐Generation Thermoelectric Power Device Based on the Radiative Cooling Emitter and Solar Selective Absorber

Self‐generation power devices based on the radiative cooling effect have intense potential applications in the energy conversion field. A selective solar absorber is introduced into thermoelectric generator (TEG) devices based on radiative cooling emitters (RCEs). The self‐generation device can work continuously for 24 h, and the output power is greatly enhanced. The RCE is prepared as a polydimethylsiloxane–Al structure by a simple squeegee method. The solar selective absorber (SSA) of the W–Si–O laminated film is prepared by the magnetron sputtering method. Its working temperature can reach as high as 85 °C under AM1.5 sunlight. The calculation results prove that the selective solar absorber can achieve 1.55 times the net heating power of an ideal blackbody at the same working temperature of 85 °C. The assembled self‐generation power device achieves output powers of 695.1 and 5.23 mW m−2 on clear days and nights, respectively, as well as an output power of 7.64 mW m−2 even in the cloudy daytime. The result of theoretical calculation proves that the addition of SSA can greatly increase the temperature difference and the average working temperature, which improves the efficiency of the TEG and the output power of the device.

High-temperature Bi2Te3 thermoelectric generator fabricated using Cu nanoparticle paste bonding

For the successful commercialization of Bi2Te3-based thermoelectric generator (TEG) devices, not only highly efficient TE materials, but also reliable bonding materials with high thermal stability are essential. In this study, we investigated the application of Cu nanoparticle paste (CNP) bonding for increasing the operating temperature of Bi2Te3-based TEG devices. Six-chip TEG devices were fabricated by joining surface-metalized Bi2Te3-based TE chips and Cu electrodes by CNP bonding. The optimal bonding was achieved when spark plasma sintering was carried out at 310–320 °C and 15 MPa. The 6-chip Bi2Te3-based TEG devices showed a maximum output power of 50–60 mW at the hot-side temperature of 400 °C (∆T= 380 °C) and maintained almost the same output power after five thermal cycles. The scanning electron microscopy images of the thermally cycled electrodes further confirmed the robustness of the Cu nanoparticle joints. This work provides an effective method for joining TE chips and Cu electrodes for high-temperature TEG devices.

Numerical simulation to evaluate the influence of geometric parameters on the physical behavior of heat exchangers

In the present investigation, a methodology was developed by means of numerical simulation for the evaluation of the influence of the geometric parameters of the heat exchangers used in thermoelectric generation devices. The validation of the proposed methodology was carried out through experimental tests on a diesel engine test bench under four load conditions (2 Nm, 4 Nm, 6 Nm, and 8 Nm) and a constant speed of 3600 rpm. The results obtained show that the methodology proposed by means of the numerical simulation presents a high concordance with the behavior described experimentally. The deviation between the simulation predictions and the experimental results was less than 4%. Additionally, it was evidenced that the change in the geometry of the heat exchanger has a considerable impact on the parameters of heat flow and surface temperature. It was shown that a 50% reduction in fin distance causes an increase of 2% and 2.4% in the previous parameters. Through geometric modifications, the electrical power generated increased by 7.9%. In general, the methodology developed through numerical simulation allows the analysis of the physical, thermal, and hydraulic phenomena present in heat exchangers focused on use in thermoelectric devices.

Evaluation of Thermoelectric Generators under Mismatching Conditions

Due to the wide usability of thermoelectric generators (TEG) in the industry and research fields, it is plausible that mismatching conditions are present on the thermal surfaces of a TEG device, which induces negative-performance effects due to uneven surface temperature distributions. For this reason, the objective of this study is to characterize numerically the open-circuit electric output voltage of a TEG device when a mismatching condition is applied to both the cold and hot sides of the selected N and P-type semiconductor material Bi0.4Sb1.6Te3. A validated numerical simulation paired with a parametric study is conducted using the Thermal-Electric module of ANSYS 2020 R1, for which different thermal boundary and mismatching conditions are applied while considering the temperature-dependent thermoelectrical properties of the N and P-type material. The results show an inverse relationship between the open-circuit voltage and the mismatching temperature difference. When a mismatching condition is applied on the hot side of the TEG device, the temperature-dependent electrical resistance has lower values, deriving in higher voltage results (linear tendency) compared to a mismatching condition applied to the cold side (non-linear tendency).

Electrical and thermal optimization of energy-conversion systems based on thermoelectric generators

Thermoelectric generator devices, which convert heat directly into electrical power, have a great potential for energy scavenging and green energy harvesting applications. The exploitation of such a potential requires a proper design of both the electrical circuit that drives the electrical load and the thermal part, in particular when the thermoelectric generator is coupled with the hot and cold heat sources through thermal resistances. We propose a straightforward approach to take into account both thermal and electrical issues, by means of an equivalent electric circuit model that can be solved with widely available simulator programs, such as SPICE. Our approach is shown to be effective for supporting the design and optimization of thermoelectric systems from the point of view of the output power and of the efficiency. In particular, with our model we are able to point out that thermal resistance matching optimizes the thermal fluxes only in first approximation: for a particular case study we find that the optimal module thermal resistance is 20% larger than the contact resistance. We also show that the electrical matching for the maximum output power must be carefully considered for each particular thermoelectric module and load condition.

Conformal High-Power-Density Half-Heusler Thermoelectric Modules: A Pathway toward Practical Power Generators.

Thermoelectric generators (TEGs) exploiting the Seebeck effect provide a promising solution for waste heat recovery. Among the large number of thermoelectric (TE) materials, half-Heusler (hH) alloys are leading candidates for medium- to high-temperature power generation applications. However, the fundamental challenge in this field has been inhomogeneous material properties at large wafer diameters, insufficient power output from the modules, and rigid form factors of TE modules. This has restricted the transition of TEGs in practical applications for over three decades. Here, we successfully demonstrate large diameter wafers with uniform TE properties, high-power conformal hH TE modules for high-temperature application, and their direct integration on flue gas platforms, such as cylindrical tubes, to form large area flexible TEGs. This new conformal architecture design provides a breakthrough toward medium-/high-temperature TEGs over the conventional BiTe- and polymer-based flexible TEG design. A variable fill factor and greater flexibility due to the conformal design result in higher device performance as compared to conventional rigid TEG devices. Modules with 72-couple hH legs exhibit a device high-power-density of 3.13 W cm-2 and a total output power of 56.6 W under a temperature difference of 570 °C. These results provide a promising pathway toward widespread utilization of thermoelectric technology into the waste heat recovery application and will have a significant impact on the development of practical thermal to electrical converters.

Fully printed and flexible carbon nanotube-based thermoelectric generator capable for high-temperature applications

In this study, a fully printed carbon nanotube (CNT) based Thermoelectric Generator (TEG) is successfully fabricated, which exhibits excellent flexibility and remarkable power output, capable of high-temperature operation up to 350 °C. The TEG device can be easily manufactured through ink printing processes of low-cost aqueous single wall carbon nanotube-based (SWCNT) ink with a mask-assisted design. The optimal SWCNT-based thermoelectric (TE) films fabricated on high-temperature resistant polyimide (Kapton) substrate exhibit a remarkable power factor of 493 μW/mK 2 at ΔΤ = 300 K, combined with excellent stability in air. The TEG device is capable to operate at temperatures up to 350 °C in ambient conditions (atmospheric pressure: 1 atm and relative humidity: 50 ± 5%). Together with exceptional stability and flexibility, the produced TEG exhibits thermoelectric performance values among the highest ever reported in the field of carbon-based and printed thermoelectric devices, with i.e. open-circuit voltage V OC = 1.11 V, short-circuit current I SC = 1.67 mA and internal resistance R TEG = 671 Ω at ΔT = 300 K, generating a maximum power output (P max ) of 461 μW. The proposed TEG device architecture is easily scalable, enabling large-scale printing manufacturing opportunities towards highly efficient, high-operating temperature, printed and flexible carbon-based TEGs. • Fully printed, flexible and low-cost carbon-based TEG fabrication. • SWCNT-based printed TE film with power factor PF = 493 μW/mK 2 . • Open circuit voltage: V OC = 1.11 V. • Short circuit current: I SC = 1.67 mA. • Power output: P max = 459 μW.

All-Oxide p-n Junction Thermoelectric Generator Based on SnOx and ZnO Thin Films.

Achieving thermoelectric devices with high performance based on low-cost and nontoxic materials is extremely challenging. Moreover, as we move toward an Internet-of-Things society, a miniaturized local power source such as a thermoelectric generator (TEG) is desired to power increasing numbers of wireless sensors. Therefore, in this work, an all-oxide p-n junction TEG composed of low-cost, abundant, and nontoxic materials, such as n-type ZnO and p-type SnOx thin films, deposited on borosilicate glass substrate is proposed. A type II heterojunction between SnOx and ZnO films was predicted by density functional theory (DFT) calculations and confirmed experimentally by X-ray photoelectron spectroscopy (XPS). Moreover, scanning transmission electron microscopy (STEM) combined with energy-dispersive X-ray spectroscopy (EDS) show a sharp interface between the SnOx and ZnO layers, confirming the high quality of the p-n junction even after annealing at 523 K. ZnO and SnOx thin films exhibit Seebeck coefficients (α) of ∼121 and ∼258 μV/K, respectively, at 298 K, resulting in power factors (PF) of 180 μW/m K2 (for ZnO) and 37 μW/m K2 (for SnOx). Moreover, the thermal conductivities of ZnO and SnOx films are 8.7 and 1.24 W/m K, respectively, at 298 K, with no significant changes until 575 K. The four pairs all-oxide TEG generated a maximum power output (Pout) of 1.8 nW (≈126 μW/cm2) at a temperature difference of 160 K. The output voltage (Vout) and output current (Iout) at the maximum power output of the TEG are 124 mV and 0.0146 μA, respectively. This work paves the way for achieving a high-performance TEG device based on oxide thin films.

Electrical and Thermal Optimization of Energy-Conversion Systems Based on Thermoelectric Generators

Thermoelectric generator devices, which convert heat directly into electrical power, have a great potential for energy scavenging and green energy harvesting applications. The exploitation of such a potential requires a proper design of both the electrical circuit that drives the electrical load and the thermal part, in particular when the thermoelectric generator is coupled with the hot and cold heat sources through thermal resistances. We propose a straightforward approach to take into account both thermal and electrical issues, by means of an equivalent electric circuit model that can be solved with widely available simulator programs, such as SPICE. Our approach is shown to be effective for supporting the design and optimization of thermoelectric systems from the point of view of the output power and of the efficiency. In particular, with our model we are able to point out that thermal resistance matching optimizes the thermal fluxes only in first approximation. We also show that the electrical matching for the maximum output power must be carefully considered for each particular thermoelectric module and load condition.

Fast and Accurate Performance Prediction and Optimization of Thermoelectric Generators with Deep Neural Networks

AbstractPredicting the performance of thermoelectric generators (TEGs) is an essential part of designing high‐performance TEGs. However, due to the complexity of the TEG system, the existing methods are either time‐consuming or not precise enough, inconvenient for device optimization. In this paper, the deep learning (DL) method to fast and accurately get the performance of TEG devices is presented. First, the key features of a typical TEG device are captured and the training dataset is prepared based on the extracted features and finite element simulations. Next, a proper deep neural network architecture is acquired and the model is trained to converge at a low loss. Finally, the experimental data is used to validate the generalization ability of the presented model. Besides, the device optimization based on the DL solution is performed and an output power enhancement of up to 182% is achieved for the authors’ sample module. The presented DL solution thus can be well applied in designing or optimizing high‐performance TEGs. Furthermore, the established framework also sheds considerable light on applying the DL approach to solve general engineering problems.

High performance scalable and cost-effective thermoelectric devices fabricated using energy efficient methods and naturally occuring materials

Various printing methods have recently been employed to manufacture thermoelectric generators. While providing a scalable alternative to manufacturing thermoelectric generators, these printing techniques consume excessive energy by using long-duration and high-temperature sintering to reduce the interfacial connections and grain boundaries between thermoelectric particles. We report an inexpensive and energy-saving technique for fabricating thermoelectric generator devices that can be employed for low-waste heat applications. This technique involves a synergistic approach, using a small amount of binder (0.05 wt%), a heterogenous distribution of thermoelectric particles of varying size, low temperature (120 °C) and short duration (30 min) curing, and application of uniaxial mechanical pressure (200 MPa) to reduce the grain boundaries and interfacial connection and to enhance electrical conductivity of thermoelectric composite films and thermoelements. In this work, we present a thermoelectric prototype fabricated on gold-coated Kevlar substrate using p-type chitosan-100 mesh Bi0.5Sb1.5Te3 and n-type chitosan-100 mesh Bi composite inks. The dimension of a single thermoelement was 6.5 mm × 2.3 mm × 150 µm. The 9-couple planar device was able to produce a power output of 73 µW at a voltage of 26 mV, and at a current of 2.8 mA at a temperature difference of 40 K, which is sufficient to power wireless sensor devices. Using energy-efficient methods and naturally occurring materials (Bi and chitosan), this device achieved a power density of 566 µW/cm2 for a temperature difference of 40 K matching the best reported power densities of printed thermoelectric devices fabricated using high temperature and long duration.

A high performance flexible and robust printed thermoelectric generator based on hybridized Te nanowires with PEDOT:PSS

In this work, we demonstrate a water-based scalable synthetic method of Te nanowires (NWs) and formulation of hybrid thermoelectric (TE) inks utilizing poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), towards the fabrication of high performance and flexible printed thermoelectric generators (TEGs). X-Ray diffraction (XRD) and Raman spectra confirm the high crystallinity of Te NWs nanocrystals with hexagonal lattice. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) illustrated the microstructural features of the produced nanostructures, as well as the monocrystalline nature of the synthesized Te NWs. Hall-effect measurements determined the carrier density and mobility of Te NWs and their hybrid materials. According to the thermoelectric response and best power factor (PF) of the hybrid inks measured in solid-state of pre-fabricated films (max. PF = 102.42 μW/m K2), a flexible TEG has been fabricated with a power output (Pout) of ~ 4.5 µW upon being exposed to ΔT = 100 K. The fabricated TEG demonstrated herein can be produced in a continuous and scalable roll-to-roll (R2R) printing process using i.e. slot die, gravure, etc. printing technologies towards the realization of large scale flexible TEG production and future large scale thermal energy harvesting by printed TEG devices.

Performance assessment of thermoelectric self-cooling systems for electronic devices

Due to the development of high-performance electronic devices, there exists a continuous need for effective and efficient cooling systems capable of removing large amounts of heat. A thermoelectric self-cooling system with forced air cooling based on a finned plate heat sink (case-a) and a water cooling based on a microchannel heat sink (case-b) is evaluated through a thermodynamic model. This article investigates the effect of the thermoelement geometry concerning its length and cross-section on the cooling capability of a self-cooling system for a wide range of heat fluxes (10 W to 200 W). Also, the effect of the efficiency related to the DC/DC converter between the thermoelectric generator and pumping devices is included in the analyses. The results show that shorter thermoelements with bigger cross-sections contribute to lower global thermal resistance and lower overheating of the electronic device. However, through the aspect ratio of the thermoelements (δ = cross-section/length), a practical limit was found defining how much shorter the thermoelement must be to satisfy a temperature constraint through the self-cooling condition for different fill factors, which corresponds to δ≤20. Beyond this limit, the performance of the self-cooling system is affected by the low conversion of heat into electricity used to run the pumping devices. The results also demonstrate for δ = 20 and fill factor equal to 0.95, that the temperature constraint (373 K) is satisfied for a heat flux equal to 124 W (case-a) and 173 W (case-b) when the efficiency of the DC/DC converter is 10%. Instead, a DC/DC converter with the highest efficiency (95%) rises the heat flux to 161 W (case-a) and 200 W (case-b), satisfying the constraint. Finally, this article summarizes the maximum heat flux for different thermoelements aspect ratios (δ ≤ 20) and fill factors where the self-cooling system for both cases satisfies a temperature constraint.

Thermoelectric Energy Harvesting from Single-Walled Carbon Nanotube Alkali-Activated Nanocomposites Produced from Industrial Waste Materials.

A waste-originated one-part alkali-activated nanocomposite is introduced herein as a novel thermoelectric material. For this purpose, single-walled carbon nanotubes (SWCNTs) were utilized as nanoinclusions to create an electrically conductive network within the investigated alkali-activated construction material. Thermoelectric and microstructure characteristics of SWCNT-alkali-activated nanocomposites were assessed after 28 days. Nanocomposites with 1.0 wt.% SWCNTs exhibited a multifunctional behavior, a combination of structural load-bearing, electrical conductivity, and thermoelectric response. These nanocomposites (1.0 wt.%) achieved the highest thermoelectric performance in terms of power factor (PF), compared to the lower SWCNTs’ incorporations, namely 0.1 and 0.5 wt.%. The measured electrical conductivity (σ) and Seebeck coefficient (S) were 1660 S·m−1 and 15.8 µV·K−1, respectively, which led to a power factor of 0.414 μW·m−1·K−2. Consequently, they have been utilized as the building block of a thermoelectric generator (TEG) device, which demonstrated a maximum power output (Pout) of 0.695 µW, with a power density (PD) of 372 nW·m−2, upon exposure to a temperature gradient of 60 K. The presented SWCNT-alkali-activated nanocomposites could establish the pathway towards waste thermal energy harvesting and future sustainable civil engineering structures.

Highly Stretchable PU Ionogels with Self-Healing Capability for a Flexible Thermoelectric Generator.

With the development of thermoelectric (TE) generator, the flexible, stretchable, self-healable, and wearable TE devices have aroused great interest. Therefore, we designed a self-healable and stretchable polyurethane (PU) ionogel, composed of polyurethane main chains with double bonds in the side, cross-linkers (BDB) and nonconjugated ionic liquids (EMIM:DCA). The PU ionogels with 30 wt % ILs have a high mechanical stretchability (300%), good tensile strength (1.61 MPa), and suitable Young's modulus (0.79 MPa). The proposed materials also exhibited an excellent ionic figure of merit (ZTi) of 0.99 ± 0.3, as well as rapid self-healability in the absence of any external stimuli. The thermoelectric capability of PU ionogels kept stable under the severe condition (50% strain) and during self-healing process, which is rarely reported in recent studies. Furthermore, a stretchable and self-healable ionic thermoelectric capacitor device is also fabricated by the PU ionogels, which can efficiently convert heat into electricity.

Modeling of Thermal Integration of a Catalytic Microcombustor with a Thermoelectric for Power Generation Applications

Power generation from coupled devices employing combustion in microreactors is generating interest for portable or decentralized energy demands. We develop a model framework to predict the performance of an integrated catalytic microreactor–thermoelectric generator (TEG) device, using CFD. A strategy for modeling a standalone TEG module is proposed and validated first, followed by thermally integrating it with a microreactor. The concepts of 1D global energy conservation with lumped treatment of the electrical properties are used to develop the TEG model. Multiple thermocouples, consisting of p- and n-type semiconductors connected in series, are modeled as a single block. The properties of the Seebeck coefficient, internal resistance, and thermal conductance are aggregated for the entire block and estimated as polynomial functions of temperature. These parameters can be estimated from manufacturer data. The source terms for Seebeck, Peltier, Thomson, and Joule’s effects are incorporated into the energy conservation equation to model the TEG at steady state. The TEG model is validated with experiments in the literature. The catalytic combustion of hydrogen in a microreactor is validated independently and is subsequently used for modeling a catalytic microreactor integrated with a TEG module for power generation. The power extracted by various load resistances from the coupled device, at multiple values of inlet flow rates, is calculated and shows a good comparison with experimental data in the literature.

Design and experimental research of test platform for characterizing a thermoelectric generator based on STM32

In order to solve the problem of low utilization rate of industrial low-grade thermal energy and actively implement the national policy of energy conservation and emission reduction, a low-temperature differential Thermoelectric generator device is designed and implemented based on the thermoelectric effect. According to the basic heat flow method of thermodynamics, the vertical installation sequence of the instrument is determined, and the simulated heat source is carried out in the laboratory. DJR-G type silicon rubber heater is used as the heating device, the fin radiator is used as the radiator and combined with the insulation layer to build the Thermoelectric generator test platform. STM32 microcontroller is the main control core of the instrument; tec1-12708t200 thermoelectric module is the power generation carrier; the main output characteristic parameters of the instrument are displayed on LCD in real time, and the change curve of the output parameters is monitored on the upper computer in real time. The experimental data show that when the load resistance is 2.5 Ω, it matches the equivalent resistance, and its output power reaches the maximum value; when the cold end of the Thermoelectric generator device is effectively cooled, its output power will increase by 0.1W. The conclusion shows that the instrument can effectively realize the Thermoelectric generator function and improve the utilization rate of low-grade thermal energy.

High-performance cement/SWCNT thermoelectric nanocomposites and a structural thermoelectric generator device towards large-scale thermal energy harvesting

For the first time, the thermoelectric properties of cement/single-walled carbon nanotube (SWCNT) nanocomposites with over 3, 7, 14 and 28 days of hydration are reported, while a thermoelectric generator device (TEG) is fabricated utilising the material with the highest achieved power factor (PF).

A Robust System for Thermoelectric Device Characterization

Due to the large reduction in fossil fuel reservoirs, the consequent cost increase of deepwater extraction, and the emission of pollutants, there is a constant search for alternative ways to obtain clean energy at a lower cost. Among those sources, we focus on the energy produced by thermoelectric materials. In this work, we present a new system for the characterization of thermoelectric generation devices. Such a system performs measurements of electrical resistivity, Seebeck coefficient, and thermal conductivity in a single setup. With this, it is possible to reduce the systematic errors in the figure of merit $ZT$ and the cost of the equipment. Our equipment, together with the developed software, presented excellent results and analyses, and with that, it proves to be a robust alternative for the characterization of commercial thermoelectric devices, and of laboratory thin film thermoelectric materials.

Experimental investigation of thermoelectric generator system

This was accomplished by mathematical models for the dependent Pi terms in the quantitative data-based modelling. This aims to use dimensionless analysis to figure out what factors influence the efficiency of a thermoelectric generator device (TEG). Simple mathematical models were developed based on actual experiments in this research work to predict the pattern of voltage, current, and power generated in TEG modules. These mathematical models are one of the most effective ways to explain experimental findings and gain a better understanding of the experimental method under study. We often find ourselves in the situation of having to verify if data matches an equation while testing mathematical models against data. Experimental studies rely on experimental principles to explain which components are the most relevant, and they are based on observation to draw conclusions on how an experimental system performs well or not. Making the necessary observations without disrupting the experimental setup, however, can be difficult. The aim of this study is to see how the independent variables affect the dependent or response variable. An artificial neural network is used to model the mathematical formulation of the device that includes the TEG module (ANN). By intentionally making local changes in their thermoelectric generator experimental set-up, this experimental modelling and ANN simulation approach allows them to obtain a system-wide view. The development of logarithmic best fit mathematical models is used to evaluate the effects of the experiments. Different scatter graphs were plotted in this study to show the output of the dependent variable current ΠD2 (experimental, model, and ANN) vs. the independent variable relative to the heat source Π1.