Thermoelectric Energy Generation Research Articles

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.

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.

Review of polysilicon thermoelectric energy generators

Among the power generation for micro sensor and actuator in wireless sensor network (WSN), Internet of Things (IoT), and wearable devices applications, thermoelectric energy generators (TEGs) that can convert body heat into electricity without moving parts is considered most promising. With the advent of foundry services in IC industry over the past two decades, standard CMOS/BiCMOS process for microprocessors and micro actuators/sensors can be applied as a perfect platform for semiconductor TEGs. Many TEG designs have therefore adopted the mature, reliable, and high yield process, where the polysilicon layers facilitate high integration density of thermocouples on a wafer. This review aims at summarizing the progress of semiconductor TEGs from tailored MEMS process to commercially available standard CMOS/BiCMOS process. By comparing the reports in the open literature, semiconductor TEGs are shown to achieve performance competitive to the bismuth telluride (BiTe)-based TEGs. The performance of a semiconductor TEG can be improved by exploiting configuration design, thermocouple dimension and materials properties in modern silicon processing technology. State-of-the-art polysilicon TEGs have been shown to achieve power factor about 10 -1 ∼10 -2 μW/cm 2 K 2 and voltage factor 10 1 ∼10 2 V/cm 2 K. A 5 × 5 mm 2 TEG chip is capable of delivering more than 3 μW and over 3 V when operating at 10 K temperature difference in body temperature range.

On the Performance of Thermoelectric Energy Generators by Stacked Thermocouples Design in CMOS Process

A semiconductor thermoelectric energy generator (TEG) with a stacked thermocouple design is developed to increase thermocouple density and achieve superior harvesting performance competitive to the BiTe-based TEGs. The stacked thermocouple design is by having the P-polysilicon layer above the N-polysilicon layer, such that the thermocouple has 1/2 footprint compared with the coplanar thermocouple design. For a TEG implemented by the standard complementary metal–oxide–semiconductor (CMOS) process [Taiwan Semiconductor Manufacturing Company (TSMC) 0.35- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> two polysilicon layers and four metal layers (2P4M)], the 64- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}\,\,\times $ </tex-math></inline-formula> 2- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> thermocouple of thickness 0.455 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> (0.275- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> P-thermoleg above 0.180- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> N-thermoleg) can achieve 0.084- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> /cm2K2 power factor and 9.136-V/cm2K voltage factor in analysis and 0.075 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> /cm2K2 and 7.004 V/cm2K in experiment. Both factors are about twice over those of the TEG with coplanar thermocouples, and they are significantly superior to all TEGs with polysilicon thermocouples. The TEG performance can be increased further by stacking more thermocouples and/or by adopting polysilicon layer(s) of higher Seebeck effect. For a TEG with one stacked thermocouple by the CMOS process [TSMC 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> one polysilicon layer and six metal layers (1P6M)], the polysilicon layer of higher thermoelectric conversion efficiency can achieve 0.476- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula> /cm2K2 power factor and 60.811-V/cm2K voltage factor.

Poly(phthalazinone ether ketone) – Poly(3,4-ethylenedioxythiophene) fiber for thermoelectric and hydroelectric energy harvesting

A kind of thermoelectric and hydroelectric energy harvesting fiber made of poly(phthalazinone ether ketone) (PPEK) and poly(3,4-ethylenedioxythiophene) (PEDOT) was prepared by wet-spinning PPEK fiber and in-situ polymerization of PEDOT on PPEK fiber. The crystallinity of the PEDOT component in PPEK-PEDOT fibers increased from 28.2 % to 42.1 % with the molar ratio of 3,4-ethoxylenedioxythiophene (EDOT) and FeCl3 increased from 0.75:1 to 3:1, and the electrical conductivity of PPEK-PEDOT fiber increase from around 0.3 × 10-3 S cm−1 to almost 25.4 × 10-3 S cm−1. Benefiting from the high crystallinity, good electrical conductivity of PPEK-PEDOT fibers and the porous structure inherited from PPEK fibers, PPEK-PEDOT fibers have good thermoelectric and hydroelectric energy harvesting capabilities. PPEK-PEDOT fiber has a tree-like structure with a radial distribution of pores on the fiber cross-section, forming pore channels along the fiber axis direction, which enhanced the hydroelectric energy harvesting properties. PPEK-0.66PEDOT fiber that treated by 2wt% poly(ethylenimine) (PEI) ethanol solution would generate about 1.6 mV thermoelectric voltage with only 2 cm fiber length under the temperature gradient of 21 ℃ and produce ∼ 260 mV hydroelectric voltage under 99 % humidity at 30 ℃. As a whole, the compact and flexible PPEK-PEDOT fiber prepared in this work showed great potential in the field of thermoelectric and hydroelectric energy generation for wearable electronic devices.

New and Recent Results for Thermoelectric Energy Conversion in Graded Alloys at Nanoscale.

In this article, we review the main features of nonlocal and nonlinear heat transport in nanosystems and analyze some celebrated differential equations which describe this phenomenon. Then, we present a new heat-transport equation arising within the so-called thermomass theory of heat conduction. We illustrate how such a theory can be applied to the analysis of the efficiency of a thermoelectric energy generator constituted by a Silicon–Germanium alloy, as the application and new results for a nanowire of length nm, are presented as well. The thermal conductivity of the nanowire as a function of composition and temperature is determined in light of the experimental data. Additionally, the best-fit curve is obtained. The dependency of the thermoelectric efficiency of the system on both the composition and the difference of temperature applied to its ends is investigated. For the temperatures K, K, and K, we calculate the values of the composition corresponding to the optimal efficiency, as well as the optimal values of the thermal conductivity. Finally, these new results are compared with recent ones obtained for a system of length mm, in order to point out the benefits due to the miniaturization in thermoelectric energy conversion.

Development of thermoelectric energy generator with high area density stacked polysilicon thermocouples

A semiconductor thermoelectric energy generator (TEG) with thermocouples in high area density is proposed in this work. Different from the common TEGs with co-planar thermocouples, the high area density is achieved by placing the P-thermoleg above the N-thermoleg into a stacked thermocouple, which is then insulated above and below by double cavity to retain sufficient thermal gradient. The TEG voltage factor is therefore increased by a factor of 2. For a TEG implemented by standard CMOS process (TSMC D35 2P4M), simulation shows that the stacked thermocouple of size 58 × 2 × 0.180 µm P-type thermoleg above 64 × 2 × 0.275 µm N-type thermoleg can reach optimal performance. Measurement results of a 5 × 5 mm2 TEG chip by semiconductor foundry service confirm the power factor of 0.075 μW/cm2K2 and the voltage factor of 7.004 V/cm2K are 1.7 x and 2.5 x, respectively, of that in TEG with co-planar thermocouples. This performance is the best of all TEGs with polysilicon thermocouples by standard CMOS process.

Anharmonic effects on lattice dynamics and thermal transport of two-dimensional InTe monolayer

The lattice thermal conductivity (κl) plays a key role in the performance of thermoelectric (TE) materials, where the lower values lead to higher figure of merit values. Two-dimensional (2D) group III-VI monolayers such as InTe are promising materials for TE energy generation owing to their low κl that lead to high TE figure of merit values. In this work, we investigate the influence of the lattice anharmonicity on the lattice thermal conductivity of InTe monolayer. The thermodynamic parameters are calculated by using the self-consistent phonon (SCP) theory. The κl value of the InTe monolayer is obtained to be 0.30 Wm−1 K−1 by using the standard Boltzmann transport equation (BTE) approach, while it is 3.58 Wm−1 K−1 by using SCP + BTE approach. These results confirm the importance of the anharmonic effects on the κl value, where it was found to be significantly higher (91%) using the SCP + BTE approach than that obtained using the standard BTE approach.

The Disk-Magnet Electromagnetic Induction Applied to Thermoelectric Energy Conversions

The thermoelectric energy conversion technique by employing the Disk-Magnet Electromagnetic Induction (DM-EMI) and improved DM-EMIs is shown, and possible applications to heat engines as one of the energy harvesting technologies are also discussed. The idea is induced by integrating irreversible thermodynamical mechanism of a water drinking bird with that of a Stirling engine, resulting in thermoelectric energy generation different from conventional heat engines. The current thermoelectric energy conversion with DM-EMI can be applied to wide ranges of temperature differences. The mechanism of DM-EMI energy converter is examined in terms of axial flux magnetic lines and categorized as the axial flux generator. It is useful for practical applications to macroscopic heat engines such as wind, geothermal, thermal and nuclear power turbines and heat-dissipation lines, for supporting thermoelectric energy conversions. The technique of DM-EMI will contribute to environmental problems to maintain clean and susceptible energy as one of the energy harvesting technologies.

Performance Analysis of Thermoelectric Energy Generator with Stacked Polysilicon Germanium Thermocouples

Performance Analysis of Thermoelectric Energy Generator with Stacked Polysilicon Germanium Thermocouples

Development of Thermoelectric Energy Generator with High Area Density Stacked Polysilicon Thermocouples

Development of Thermoelectric Energy Generator with High Area Density Stacked Polysilicon Thermocouples