Thermoelectric Energy Generation Research Articles

Enhancing the Performance of Oxide‐Based Transverse Thermoelectric Generators by Optimized Internal Geometry

AbstractIn transverse thermoelectric generators (TTEGs), comprising an artificially anisotropic material formed by a layered and tilted structure of two materials, the induced thermoelectric voltage is generated perpendicular to the applied temperature gradient. The performance of TTEGs composed of alternate layers of La1.99Sr0.01CuO4 (LSCO) and silver (Ag), tilted at an angle φ, with metal‐to‐ceramic thickness ratio νt, is investigated. Improvement in performance is achieved by optimizing the internal geometry parameters, φ and νt of the tilted layered structure. The transverse power factor PFtr and figure‐of‐merit ZtrT of the artificially tilted material composite are analytically calculated and presented in color contours. Experimentally, a power output Pout of 14.5 mW at ΔT = 140 K is measured for a TTEG with φ = 66°, compared to 2.8 mW and 11 mW for generators with φ of 20° and 45°, respectively. Moreover, TTEGs with different values of νt are prepared. Furthermore, transverse multilayer thermoelectric generators (TMLTEG) with output power of 14.3 mW at ΔT = 225 K are fabricated utilizing the ceramic multilayer technology. It is demonstrated that the transverse thermoelectric effect using an artificial anisotropic material consisting of ceramic and metal can be explored for autonomous thermoelectric energy generation for low‐power applications.

Advancement of germanium-based thermoelectric materials: a bibliometric and network analysis

Germanium (Ge)-based thermoelectric materials have proven to be a reliable and sustainable solution for efficient energy harvesting across a wide range of temperatures for an extended period. Numerous investigations have been published addressing the future scope of Ge as a thermoelectric material. This article offers a comprehensive bibliometric analysis of the literature related to Germanium-based thermoelectric energy harvesting (Ge-TEH) materials available on Scopus to identify how this material contributes to thermoelectric energy generation. Methodologies such as citation analysis, co-authorship, and co-occurrence analysis are employed to analyze refined data of ‘1867’ documents using 'Visualization of similarity' (VOS) viewer and Biblioshiny. The analysis shows that Ge-TEH has grown significantly worldwide, especially in the last decade. The social and intellectual networks were generated, and the most influencing countries, sources, and institutions were identified. China and the United States (USA) were found to have the highest number of publications, citations, and collaborations. The keywords analysis reveals that ‘lattice thermal conductivity,’ ‘Germanium,’ ‘Seebeck coefficient,’ ‘spark plasma sintering’, and ‘density functional theory’ are the most occurring words, indicating that the dataset features keywords related to thermoelectric materials and their properties. It also suggests a strong emphasis on fabrication methods for optimizing thermoelectric properties. The mutual relevance and categorical patterns of frequently occurring keywords were studied using a factorial analysis graph. This detailed analysis provides critical findings into the evolution and future scope of the research in Ge-TEH.

Thermoelectric generator for energy production from renewable sources

Thermoelectric generators (TEG) produce electrical energy from a temperature difference between the cold and hot side of TEG modules (Seebeck effect); in principle, they can be used at temperature differences greater than 3 K [1]. Thermoelectric energy generation is primarily known for supplying self-sufficient sensors or in exhaust systems of motor vehicle internal combustion engines [2], where high temperature differences of up to 700 K are used. In this paper, basic investigations are carried out in order to expand the power range of thermoelectric energy generation and their potential for the energy transition. To this end, the area of application should be expanded to include medium and small temperature differences. The output characteristic of a TEG module has a power maximum, which increases quadratically with the temperature difference and linearly with the module area. At a temperature difference of 40 K, an output of 250 W/m2 can be generated. A solar module can generate 150 W/m2 in full sunlight; this output is only available for 12 % of the year given the 1000 full-load hours of sunshine that are usual in our latitudes. A continuous thermoelectric energy source could provide energy all year. Under optimal conditions, an annual usage time of 5000 hours and a service life of 10 years, electricity production costs of around 10 Cents/kWh can be expected [3]. This price is quite comparable to other renewable energy sources (photovoltaics, wind).

Porous Thermoelectric Materials for Energy Conversion by Thermoelectrocatalysis

Novel uses of thermoelectric (TE) materials as catalyst and catalyst promoters have been reported recently for a variety of applications such as environmental gas mitigation, battery, and photoreduction of nuclear wastewater. TE Seebeck voltage is found to increase the catalytic activities by tens to hundreds of times, and this effect is termed thermoelectrocatalysis. In these uses, the TE materials are in an open‐circuit configuration, which is different from the usual closed‐circuit configuration in the TE energy generation and cooling devices. A new figure of merit defined as the Seebeck voltage per unit heat loss is proposed for the application of thermoelectrocatalysis. Techniques such as dense bulk porous surface and increased thickness of the TE materials are used for the optimization of the thermoelectrocatalysis of the oxyselenide BiCuSeO for the carbon dioxide hydrogenation reactions.

Orientational Effects and Molecular-Scale Thermoelectricity Control.

The orientational effect concept in a molecular-scale junction is established for asymmetric junctions, which requires the fulfillment of two conditions: (1) design of an asymmetric molecule with strong distinct terminal end groups and (2) construction of a doubly asymmetric junction by placing an asymmetric molecule in an asymmetric junction to form a multicomponent system such as Au/Zn-TPP+M/Au. Here, we demonstrate that molecular-scale junctions that satisfy the conditions of these effects can manifest Seebeck coefficients whose sign fluctuates depending on the orientation of the molecule within the asymmetric junction in a complete theoretical investigation. Three anthracene-based compounds are investigated in three different scenarios, one of which displays a bithermoelectric behavior due to the presence of strong anchor groups, including pyridyl and thioacetate. This bithermoelectricity demonstration implies that if molecules with alternating orientations can be placed between an asymmetric source and drain, they can be potentially utilized for increasing the thermovoltage in molecular-scale thermoelectric energy generators (TEGs).

Assessment of Artificial Anisotropic Materials for Transverse Thermoelectric Generators

By alternately stacking layers of two materials that differ in their Seebeck coefficient and electrical and thermal conductivity, a composite material with artificial anisotropy of thermal and electrical transport properties is formed. Due to the transverse Seebeck effect, a thermoelectric (TE) voltage is generated perpendicular to a temperature gradient ΔT, that is applied at a certain angle φ with respect to the stacked layers (0° < φ < 90°). The TE properties of layered artificial anisotropic materials are described analytically using existing concepts and extending the available definitions to develop a consistent image of anisotropic media for TE energy generation. Based on these analytical descriptions, the TE performance of ceramic oxide–metal composites and transverse TE generators (TTEG) made of them are numerically calculated and presented in contour plots. These so‐called micro‐ and macro‐Babin plots map the influence of internal geometric parameters, i.e., the layer thickness ratio and the angle φ of the applied temperature gradient with respect to the stacked layers. Based on these diagrams, the optimal TTEG geometry can be narrowed down in a simple and fast way. In addition, the diagrams are used for a material screening to evaluate the suitability of different oxide ceramics for use in a TTEG.

Evaluation of energy efficiency of thermoelectric energy generator system with heat pipes, solar tracker, Fresnel lens and nano-particle fluids

This study investigated the limits of electrical energy production from a thermoelectric generator in a high thermal efficiency system using pure water and nanofluids called aluminum oxide and titanium dioxide. It was aim to provide efficient thermal performance by using a Fresnel lens, solar glass tube, heat pipe and tracking system. Experimental measurements were made between 10:00 and 14:00 on July 26 and 27 in 2023. On each measurement day, the system containing pure water and a nanofluid was compared. The values of parameters such as temperature, solar radiation, wind speed and Thermoelectric Generator (TEG) open circuit voltage were measured instantaneously during the measurements. These data were used to calculate thermal resistance, electrical efficiency and output power. The results showed that the open circuit voltage increased with increasing solar radiation and, therefore, hot side temperature. The calculations showed that the highest open circuit voltage of 2.76 V was obtained with the mechanism using pure water as the working fluid. However, the obtained electrical efficiency ηe and output power Pmax values remained at 1.06 % and 1.058 W, respectively. Numerical and Artificial Neural Network (ANN) models are widely used to save time and cost in determining the optimal operating conditions of the TEG. Therefore, in addition to the experimental study, a numerical model consisting of TEG and a cooling system, and an Artificial Neural Network (ANN) model were also developed in this study. The average absolute errors for Computational Fluid Dynamics (CFD) and electrical results were obtained in the numerical model as 3.47 % and 2.97 %, respectively. In addition, the average absolute errors in the ANN model were obtained as 0.6 %, 0.5 % and 0.27 % for water, Al2O3 and TiO2 nanofluids, respectively.

Black TiO2-infused polydimethylsiloxane composites for efficient solar-assisted water evaporation and thermoelectric energy generation

Solar assisted interfacial water evaporation through the strategic localization of solar- thermal energy conversion by relying on the air–water interface has garnered significant interest owing to its enhanced efficiency in a variety of applications, from water purification to energy generation. Nevertheless, achieving utterly improved thermal management to enhance the efficiency of solar heat consumption is still quite complex. Herein, we created special composites of black titanium dioxide and polydimethylsiloxane (B-TiO2/PDMS) aiming effectively harvest a broad range of spectrum of solar radiation for the benefit of improving energy production and aid for water purification. The B-TiO2/PDMS sponge possesses an impressive optical to thermal transformation as an outcome, keeping a constant surface temperature of 66 °C, as opposed to 41.6 °C for PDMS sponge at typical 1 sun intensity for 10 min. This solar evaporation system constitutes a greater evaporation rate of 1.39 Kg m−2h−1 with a photothermal conversion efficiency of 70.8 % under 1 sun illumination. To accomplish integrated thermoelectric power generation during solar evaporation, the thermoelectric (TE) module is used as an insulating medium, succeeding an optimal yield of 30 mV under 1 sun. Furthermore, the as prepared B-TiO2/PDMS sponge achieved notable mechanical resilience and incredible adaptability, offering a viable approach for thermal management and cooperative way to utilize solar powered evaporation to produce potable water and energy.

Exceptional Thermoelectric Performance of Cu2(Zn,Fe,Cd)SnS4 Thin Films.

High-quality Cu2(Zn,Fe,Cd)SnS4 (CZFCTS) thin films based on the parent CZTS were prepared by aerosol-assisted chemical vapor deposition (AACVD). Substitution of Zn by Fe and Cd significantly improved the electrical transport properties, and monophasic CZFCTS thin films exhibited a maximum power factor (PF) of ∼0.22 μW cm-1 K-2 at 575 K. The quality and performance of the CZFCTS thin films were further improved by postdeposition annealing. CZFCTS thin films annealed for 24 h showed a significantly enhanced maximum PF of ∼2.4 μW cm-1 K-2 at 575 K. This is higher than all reported values for single-phase quaternary sulfide (Cu2BSnS4, B = Mn, Fe, Co, Ni) thin films and even exceeds the PF for most polycrystalline bulk materials of these sulfides. Density functional theory (DFT) calculations were performed to understand the impact of Cd and Fe substitution on the electronic properties of CZTS. It was predicted that CZFCTS would have a smaller band gap than CZTS and a higher density of states (DoS) near the Fermi level. The thermal conductivity and thermoelectric figure of merit (zT) of the CZFCTS thin films have been evaluated, yielding an estimated maximum zT range of 0.18-0.69 at 550 K. The simple processing route and improved thermoelectric performance make CZFCTS thin films extremely promising for thermoelectric energy generation.

Comparative analysis of numerical models of plate-fin heat sinks with forced convection for thermoelectric energy generation

Plate-fin heat sinks under forced convection are economical dissipaters employed in a wide variety of sectors. These types of heat sinks are commonly used in power generation by means of commercial thermoelectric generator modules. The design of the heat sink is a key factor in these power generation systems since it greatly affects the efficiency of the direct conversion from heat into electrical energy. Here, we analyse several numerical models of plate-fin heat sinks under forced convection with and without air flow bypass. The predictions of both hydraulic and thermal parts of these models are compared with our own experimental data. Results reveal that Lindstedt and Karvinen model (2012) is the more accurate one, with discrepancies with respect to measurements below 12% for most of the cases studied.

The Application of Thermomechanical Dynamics (TMD) to Thermoelectric Energy Generation by Employing a Low Temperature Stirling Engine

The Application of Thermomechanical Dynamics (TMD) to Thermoelectric Energy Generation by Employing a Low Temperature Stirling Engine

An Introduction to Consumptive Use of Water in South Carolina

Effective water resource management requires understanding the supply of and the demand for water. In South Carolina, as in other places, water demand is often determined using total withdrawal volumes. However, the volume of water that is withdrawn can be significantly different from the volume that is actually consumed, which becomes unavailable for downstream uses. Water used for energy generation is commonly excluded from evaluations of total withdrawal volume because it is often assumed to be no or low consumptive use, meaning much of the withdrawn water is returned to the source and remains available for downstream uses. Additionally, energy production withdrawal volumes may be significantly higher than other sectors’ usage and make it difficult to further compare water use of other sectors. Consumptive use volumes are not readily available for South Carolina and can be challenging to determine. However, estimates of consumptive use could allow more meaningful comparisons between water use sectors’ impacts. The objective of this short communication is to briefly discuss data sources, outline two relatively simple methods for calculating consumptive use with available data, identify challenges and opportunities for additional research, and provide preliminary estimates of consumptive water use volumes per water use sectors in South Carolina. Expanded discussion of consumptive water use of thermoelectric energy generation is included due to the significant total water withdrawals and unique challenges with calculating consumptive use of this sector. These results inform water resource planning and identify additional research opportunities.

Design and analysis of thermoelectric energy harvester with 85.6% peak end-to-end efficiency and 38 mV self-startup using 4.13 mΩ/°C indirect temperature dependent MPPT

We present an efficient power management system (PMS) to harvest energy from thermoelectric energy generators (TEGs) via indirect temperature tracking. The PMS includes a power converter with an indirect temperature-dependent (ITD) maximum power point tracking (MPPT) controller and two complementary self-startups. The ITD-MPPT controller consists of an ITD input sampling circuit (ITD-ISC) and an ITD impedance matching circuit (ITD-IMC). The ITD-ISC detects and samples the TEG voltage (VTEG) under dynamically varying temperature gradients. The ITD-ISC removes unnecessary detachments of the converter from multi-mode reconfigurable TEGs to recover the otherwise wasted power using an adaptive input sampling (AIS) technique. The ITD-IMC adjusts the on-time of the power switch to control the input impedance (RIN) of the converter with a relatively high resolution of 4.13 mΩ/°C. This approach provides an ultrawide range source tracking from 2 Ω to 200 Ω. We also present a precision zero current switching (ZCS) controller to manage the on-time of the two power switches simultaneously. Two complementary self-startup components are realized using transformer-based (TSC) and charge-pump-based startup circuits (CSC). Integrated circuits for the PMS are fabricated using 180 nm and 28 nm CMOS processes for high efficiency and low voltage, respectively. The measurements indicate that the proposed PMS achieves an end-to-end efficiency (ηEE) above 80% over a wide source VTEG range (100 mV – 450 mV). The peak ηEE of 85.6% is achieved for VTEG = 200 mV, demonstrating the high-performance MPPT using indirect temperature tracking. TSC and CSC demonstrate successful self-startups at input voltages of 38 mV and 200 mV, respectively, thus providing reliable startup methods for various renewable energy sources.

Parametric study and sensitivity analysis on thermoelectric energy generation of building integrated photovoltaic facades in various climatic zones of China

Building Integrated Photovoltaic facades (BIPV facades) represent state-of-the-art building envelope systems generating both electrical and thermal energy. While previous research predominantly focused on electricity generation, this study investigated impact of important design parameters on all useful thermoelectric energy, including electricity, air heat gains, and indoor heat dissipation. A novel BIPV facade model has been developed in TRNSYSvalidated by extensive long-term experimental data. Through numerical simulations conducted across different climatic zones in China, parameters impact regularities were investigated with sensitivity analysis. Results revealed that influence of parameters on electricity generation is relatively modest, with sensitivity indices ranging from 0 % to 2.4 %. BIPV facade height and building insulation U-value impact demonstrate monodirectional linear pattern, while air channel width impact exhibits extremums. For all climatic zones, both electricity generation and air heat gains are most sensitive to air channel width, with sensitivity index ranging from 1.2 % to 2.4 % and 38.3 %–42.3 %, respectively. Sensitivity index of indoor heat gains to air channel width decreases from 51.2 % to 20.9 % from north to south, while sensitivity to building insulation U-value increases from 23.8 % to 85.3 %. Research provides innovative perspective on the design of BIPV facades for comprehensive thermoelectric energy utilization with design parameter priority clarified.

Revealing Low Thermal Conductivity of Germanium Tin Semiconductor at Room Temperature

AbstractThe low thermal conductivity of a material is a key essential parameter for its potential application in high‐performance thermoelectric devices. Unprecedently low thermal conductivity of germanium tin (Ge1−xSnx) semiconductor thin film is experimentally obtained at room temperature. The thermal conductivity decreases with increasing Sn concentration in the relaxed Ge1−xSnx binary alloy, which is explained mainly by increasing the interatomic distance between atoms via alloying. A pronounced decrease of thermal conductivity, by over 20 times, from 58 W m−1K−1 in Ge to ≈2.5 W m−1K−1 in relaxed Ge1−xSnx, with Sn content up to 9% is observed. This thermal conductivity is just ≈2 times higher than that of the state‐of‐the‐art thermoelectric material, Bismuth Selenium Telluride. Ge1−xSnx, in contrast, is a non‐toxic Group‐IV semiconductor material, that is epitaxially grown on a standard silicon wafer up to 300 mm diameter using the semiconductor industry standard epitaxial growth technique. As a result, it can lead to the creation of a long‐awaited high‐performance low‐cost thermoelectric energy generator for room‐temperature applications in human's daily life and would make a substantial contribution toward global efforts in CO2 emission‐free and green electricity generation.

Inside Front Cover

In this critical review, the authors explore electrical doping strategies of metal‐halide perovskites, which remains as a fundamental challenge. These challenges can potentially become a key to achieving efficient thermoelectric energy generation with this emerging class of materials. image

A Thermoelectric Energy Generator With High-Density Stacked Thermocouples by Standard BiCMOS Process

A Thermoelectric Energy Generator With High-Density Stacked Thermocouples by Standard BiCMOS Process

Performance analysis of thermoelectric energy generator with stacked polysilicon germanium thermocouples

Performance analysis of thermoelectric energy generator with stacked polysilicon germanium thermocouples

Epitaxial tin selenide thin film thermoelectrics

To enable the realization of miniaturized thermoelectric energy generation (TEG) devices for autonomous wireless sensors, high-quality thin film architectures are required. Although tin selenide (SnSe) has been identified as a promising thermoelectric material exhibiting ZT values up to 2.6 at 923 K for single crystals, most thin film studies evaluated polycrystalline or textured SnSe samples. Here, we have explored for the first time the impact of epitaxial alignment of the orthorhombic SnSe crystal structure on an orthorhombic DyScO3 substrate, in strong contrast to the few previous studies on cubic substrates. The achieved (100)-oriented single crystalline SnSe thin films exhibit the formation of two SnSe domain types. The in-plane electrical conductivity along the (b,c)-plane shows an abrupt increase above 400 K instead of the typical steady increase. The in-plane Seebeck coefficients exhibit very similar values as single crystals, leading to a maximum power factor of about 6.0 μW·K−2·cm−1. For these SnSe thin films, exhibiting two domain variants with in-plane alignment of the (b,c)-plane, a typical low thermal conductivity is expected, demonstrating the effectiveness of epitaxial alignment to enhance thermoelectric performance and to enable the realization of miniaturized thermoelectric energy generation (TEG) devices for autonomous wireless sensors.

Copper Iodide on Spacer Fabrics as Textile Thermoelectric Device for Energy Generation.

The integration of electronic functionalities into textiles for use as wearable sensors, energy harvesters, or coolers has become increasingly important in recent years. A special focus is on efficient thermoelectric materials. Copper iodide as a p-type thermoelectrically active, nontoxic material is attractive for energy harvesting and energy generation because of its transparency and possible high-power factor. The deposition of CuI on polyester spacer fabrics by wet chemical processes represents a great potential for use in textile industry for example as flexible thermoelectric energy generators in the leisure or industrial sector as well as in medical technologies. The deposited material on polyester yarn is investigated by electron microscopy, x-ray diffraction and by thermoelectric measurements. The Seebeck coefficient was observed between 112 and 153 µV/K in a temperature range between 30 °C and 90 °C. It is demonstrated that the maximum output power reached 99 nW at temperature difference of 65.5 K with respect to room temperature for a single textile element. However, several elements can be connected in series and the output power can be linear upscaled. Thus, CuI coated on 3D spacer fabrics can be attractive to fabricate thermoelectric devices especially in the lower temperature range for textile medical or leisure applications.