Efficiency Of Thermoelectric Generator Research Articles

Interface kinetic manipulation enabling efficient and reliable Mg3Sb2 thermoelectrics

Development of efficient and reliable thermoelectric generators is vital for the sustainable utilization of energy, yet interfacial losses and failures between the thermoelectric materials and the electrodes pose a significant obstacle. Existing approaches typically rely on thermodynamic equilibrium to obtain effective interfacial barrier layers, which underestimates the critical factors of interfacial reaction and diffusion kinetics. Here, we develop a desirable barrier layer by leveraging the distinct chemical reaction activities and diffusion behaviors during sintering and operation. Titanium foil is identified as a suitable barrier layer for Mg3Sb2-based thermoelectric materials due to the creation of a highly reactive ternary MgTiSb metastable phase during sintering, which then transforms to stable binary Ti-Sb alloys during operation. Additionally, titanium foil is advantageous due to its dense structure, affordability, and ease of manufacturing. The interfacial contact resistivity reaches below 5 μΩ·cm2, resulting in a Mg3Sb2-based module efficiency of up to 11% at a temperature difference of 440 K, which exceeds that of most state-of-the-art medium-temperature thermoelectric modules. Furthermore, the robust Ti foil/Mg3(Sb,Bi)2 joints endow Mg3Sb2-based single-legs as well as modules with negligible degradation over long-term thermal cycles, thereby paving the way for efficient and sustainable waste heat recovery applications.

Two-dimensional BiSbTeX2 (X = S, Se, Te) and their Janus monolayers as efficient thermoelectric materials.

Today, there is a huge need for highly efficient and sustainable energy resources to tackle environmental degradation and energy crisis. We have analyzed the electronic, mechanical and thermoelectric (TE) characteristics of two-dimensional (2D) BiSbTeX2 (X = S, Se and Te) and Janus BiSbTeXY (X/Y = S, Se and Te) monolayers by implementing first principles simulations. These monolayers' dynamic stability and thermal stability have been demonstrated through phonon dispersion spectra and ab initio molecular dynamics (AIMD) simulations, respectively. The band structure of these monolayers can be tuned by applying uniaxial and biaxial strains. The investigated lattice thermal conductivity (κl) for these monolayers lies between 0.23 and 0.37 W m-1 K-1 at 300 K. For a more precise calculation of the scattering rate, we implemented electron-phonon coupling (EPC) and spin-orbit coupling effects to calculate the transport properties. For p(n)-type carriers, the power factor of these monolayers is predicted to be as high as 2.08 × 10-3 W m-1 K-2 and (0.47 × 10-3 W m-1 K-2) at 300 K. The higher thermoelectric figure of merit (ZT) of p-type carriers at 300 K is obtained because of their very low value of κl and high power factor. Our theoretical investigation predicts that these monolayers can be potential candidates for fabricating highly efficient thermoelectric power generators.

Effect of nanofluid cooling on electrical power of solar panel system in existence of TEG implementing magnetic force

This study investigates the efficacy of applying a Lorentz force to improve the efficiency of a photovoltaic-thermal (PVT) system featuring a finned duct, while also addressing challenges associated with dust accumulation. The magnetic field helps to prevent nanoparticle aggregation, enhancing the cooling process. The use of a finned duct combined with a nanofluid as the cooling medium efficiently dissipates excess heat from the silicon layer. Dust accumulation on the glass layer reduces transmissivity, negatively impacting system performance. The magnetic field's interaction with the nanoparticles enhances convective cooling of the upper layer, leading to an overall improvement in performance. Increased pumping power results in higher cooling rates, with improvements of approximately 3.48 % in thermal efficiency (ηth), 75.01 % in thermoelectric generator efficiency (ηTEG), and 39.37 % in photovoltaic efficiency (ηPV). An increase in the Hartmann number (Ha) improves ηth by about 1.87 %, with corresponding enhancements in electrical performance components. A higher concentration of ferrofluid further boosts performance, with the effect being roughly 1.7 times more significant in the absence of MHD compared to when Ha = 97. Dust presence decreases ηth, ηTEG, and ηPV by approximately 9.39 %, 8.55 %, and 25.77 %, respectively. Furthermore, the presence of Ha diminishes the influence of Vin on ηth by around 1.33 %.

Performance investigation of a thermoelectric generator for vehicle exhaust recovery using graded pore density foam metal

Improving the efficiency of thermoelectric generators (TEGs) used to harness residual heat from automobile exhausts is crucial for their widespread adoption. To enhance fluid heat transfer, the Kelvin tetrahedron model is employed for metal foam, and a multiphysical field model of the thermoelectric generator based on metal foam is established. The effects of inserting metal foam with uniform and gradient pore densities into the heat exchanger on the performance of the TEG are investigated. Experimental verification is conducted by constructing a test bench with dimensions identical to those of the model The findings suggest that inserting foam metal significantly enhances the output performance of the TEG, resulting in increases in both output power and efficiency as pore density rises. At Ta = 573 K and ma = 30 g/s, the output power of the TEG with inserted 20 PPI foam metal is enhanced by 140.46 %, while the efficiency experiences a remarkable increase of 197.50 % compared to a smooth pipe. Compared to the performance metrics of uniform foam metal, the positive gradient foam metal exhibits a maximum power increase of 7.89 % and a maximum efficiency increase of 34.46 %, along with an average pressure drop reduction of 27.29 %.

Thermoelectric generator efficiency: An experimental and computational approach to analysing thermoelectric generator performance

TEGs are devices that convert heat directly into electricity through the Seebeck effect, offering a promising solution for waste heat recovery in various industries. In this research, COMSOL Multiphysics 6.0 was used to conduct a comprehensive 3-dimensional computational study of TEGs. Integrating thermal and electrical models in COMSOL facilitates a detailed understanding of the thermoelectric phenomenon. Applying six distinct temperature gradients, temperature and electrical distribution, power output, and efficiency of the TEG was thoroughly analysed. Experimental validation confirms strong agreement between simulation and experimental data, emphasizing accuracy. The average efficiency for the TEG at 1 Ω load is 3.12 %, increasing to 3.62 % for a 2 Ω load. The relative error between the computational model and the experimental model was 5 % for open circuit, 12.56 % for closed circuit at 1 Ω, and 12.14 % for closed circuit at 2 Ω, affirming the accuracy of the computational approach. Therefore, the computational model is validated by experimental results.Moreover, the findings highlight the relationship between external load resistance and power output, revealing that the maximum output power was achieved when the external load resistance matched the internal load resistance at 2 Ω. This work also significantly contributes to advancing the computational modelling of TEGs, validated through rigorous experimental analysis.

Performance analysis and optimization of insulation layers on a novel building-integrated photovoltaic system

Conventional photovoltaic-thermoelectric generator (PV-TEG) systems are hindered by significant heat transfer losses, which impair power generation throughout the year. Addressing this challenge, a novel PV-MCHP-TEG system is proposed, integrating photovoltaic (PV) cell, microchannel heat pipe (MCHP) array, and thermoelectric generator (TEG) module components with strategically placed insulation layers to facilitate year-round, day-and-night power generation. This study primarily investigates the impact of insulation layers on heat transfer processes, employing a comprehensive analysis and optimization approach. Utilizing Simulink software, the multifaceted influence of insulation layer variables, including locations, thicknesses, and materials, on TEG efficiency across various conditions was examined. Further, a comparative analysis was undertaken to evaluate the dynamic payback period across different modes. The optimization of these insulation parameters revealed that incorporating Polyisocyanurate Foam (PIR) as the insulation material in the optimized PV-MCHP-TEG system achieved an efficiency of 19.32 %, marking a 2.41 % improvement over conventional PV-TEG systems without insulation. Furthermore, the dynamic payback period was reduced to 11.34 years, representing a decrease of 1.05 years compared to conventional PV-TEG systems. These findings underscore the potential of our proposed system to outperform existing solutions by optimizing thermal management through insulation, thereby offering a promising avenue for enhancing photovoltaic-thermoelectric energy conversion.

Multi-criteria decision analysis and experimental study on heat pipe thermoelectric generator for waste heat recovery

In the realm of heat conversion and utilization, gravity heat pipes have garnered significant attention due to their exceptional heat conduction efficiency. As a strategy to effectively enhance the efficiency of thermoelectric generator (TEG) systems through shallow geothermal heat recovery, optimizing the performance of gravity heat pipes holds significant implications for their widespread application in the field of sustainable energy. Experimental evaluations comprehensively assessed the performance of a 6 m gravity heat pipe within a temperature difference power generation system, employing multi-criteria decision-making to test thermal performance, efficiency, reliability, stability, and working fluid studies. The study demonstrates that the heat transfer efficiency of gravity heat pipes is highest under film boiling conditions at 250 °C to 350 °C. By adjusting the inclination angle to 60° to 90° and the filling ratio to 30 %–60 %, the power generation efficiency can be improved to 9.71 %. With an increase in wind speed to 8 m/s, the cold end temperature decreases by 30 %, resulting in a peak power generation efficiency of up to 11.3 %. Additionally, CHIME connection methods reduce energy losses to 8.1 %, providing crucial scientific foundations for the design and optimization of temperature difference power generation systems. These findings not only elucidate the heat transfer mechanisms of gravity heat pipes but also offer technical guidance for efficient energy conversion in thermoelectric generator systems.

Gradient Doping Enables an Extraordinary Efficiency in Thermoelectric PbTe1-xIx.

The conversion efficiency of thermoelectric generators that have to be operated under a temperature difference (ΔT) is mainly determined by material's dimensionless figure of merit (zT). However, maximization of zT at each temperature requires an optimization of carrier concentration (nopt) which strongly depends on the temperature and band parameters. Commonly utilized strategy of chemical doping usually enables a homogeneous carrier concentration throughout the material, leading the maximal zT to be achievable only within a narrow temperature range. In this work, a gradiently doping is successfully realized in PbTe1-xIx using a vertical gradient solidification technique, enabling a spatial gradient in carrier concentration that correspondingly optimizes zT at each portion of the material under its operating temperature. Such a gradient doping results in an extraordinary device efficiency of ≈14% at a ΔT of ≈500K, corresponding to a ≈40% improvement as compared to that of homogeneous doping. Since directional solidification technique commonly enables gradient dopant concentrations in semiconductors, the resultant gradient carrier concentration is illustrated here as an effective approach for advancing thermoelectrics.

A novel strategy of inserting radiation shields to enhance the performance of thermoelectric generator systems for industrial high-temperature heat recovery

Static thermoelectric generator (TEG) systems have been widely used for recovering the high-temperature heat from the industrial sector. To control the heat loss through the gap uncovered by the thermoelectric legs for system performance improvement, a novel strategy of inserting the radiation shields in the gap that introduced additional surface and spacing resistances and regulated the gap radiation loss, was proposed. With a constructed high-fidelity theoretical model which used the finite element method to consider the temperature-dependent properties of the thermoelectric materials, comprehensive comparisons were conducted between the systems with/without radiation shields and using three commonly adopted strategies to evaluate the effectiveness and potential of this strategy. Compared to the base case without radiation shields, inserting one radiation shield with an emissivity of 0.5 enhances the TEG efficiency and system power by 15 % and 9.5 % respectively. The system using the proposed strategy outperforms that using the commonly adopted strategies, especially the strategies of lowering the gap pressure and filling the gap with thermal insulation materials, highlighting the potential of the proposed strategy. Besides, the influences of the shield emissivity and number were studied; from it, less than two radiation shields made by the polished copper are recommended for practical applications.

Model development and preliminary study of the concentrated-radiative cooling based thermoelectric generator

Photovoltaic (PV) cells, widely adopted in solar energy applications, achieve a maximum efficiency of only 30 % and remain inactive during nighttime. In contrast, solar-thermal power generation has surpassed 50 % efficiency. To address these limitations, we introduce the Solar- Radiative cooling -Thermoelectric system (Solar-RC-TE), integrating solar energy, radiative cooling (RC), and thermoelectric power generation. This system enhances energy density, reduces consumption, lowers costs, and minimizes environmental impact while enabling nighttime power generation. For the optimization of the Solar-RC-TE model to further improve power generation efficiency, we employ the comprehensive three-dimensional methodology of COMSOL, considering material properties, structural configurations, and environmental factors. Research findings reveal that a 710 mm × 710 mm radiative cooling film can generate 386.12 mV of voltage on the thermoelectric generator (TEG). Environmental factors, such as increased solar irradiance, lead to temperature elevation, affecting efficiency. Overheating and higher wind speeds also contribute to decreased TEG efficiency. Regarding materials, improving the thermoelectric figure of merit (ZT) and film emissivity positively impact power generation efficiency. Elevating the film emissivity from 0.7 to 0.89 significantly enhances performance by 1.2 %. These outcomes provide a tangible and practical solution for addressing energy crises and environmental concerns.

Investigating thin-film thermoelectric generators: Leg shape, TEG configuration, and contact resistance analysis

Thermoelectric generators (TEGs) are made of parallel p-type and n-type semiconducting legs which can directly convert temperature gradients into electricity. Theoretical studies have extensively explored the impact of the thermoelectric (TE) leg size and shape on the conversion efficiency of such bulk TEGs. However, in recent years, geometrically thin and film-shaped TEGs have gained attention for integration into wearable and flexible electronic devices, tapping into body heat as a power source. There is currently a lack of research on film-shaped TEGs, particularly regarding the performance of asymmetric TE leg shapes. This study investigates seven different TE leg shapes in thin-film TEGs, analyzing their electrical performance using COMSOL Multiphysics software. Results show that certain asymmetric TE leg shapes can yield over a 30% improvement in the produced open circuit voltage, as compared to conventional rectangular-shape TE legs. Furthermore, various configurations of thin-film TEGs were designed and analyzed, aiming to maximize device output power. Additionally, the study delves into the influence of electrical contact resistance on the performance of the optimal asymmetric TEGs. The proposed thin TE leg shapes and TEG configurations ae easily manufacturable and scalable using printing technology.

Innovative design for thermoelectric power generation: Two-stage thermoelectric generator with variable twist ratio twisted tapes optimizing maximum output

In recent years, considerable effort has been dedicated to the development of highly efficient thermoelectric generators for waste heat recovery and thermoelectric power generation. In this study, we present employing twisted tapes with variable twist ratio to enhance thermal energy extraction efficiency, coupled with two-stage thermoelectric modules for heat-to-electricity conversion, resulting in a substantial increase in the power output of the thermoelectric generator. We established an experimental system that validated the superior power generation and heat recovery characteristics of the two-stage thermoelectric generator. Building upon these findings, we propose further optimizing the variable twist ratio twisted tapes to enhance the power output. We investigated the impact of tape pitch ratio, twist ratio, and twist ratio variation range on thermoelectric performance. Experimental results indicate that the influence of flow instability is more pronounced than that of swirl intensity, and twist tapes with the maximum twist ratio variation rate yield the highest net output power. Compared to an unmodified thermoelectric generator, the two-stage thermoelectric generator employing twist tapes with a twist ratio increase from π to 3π achieves a maximum net output power gain of up to 100%. These findings provide a practical framework for integrating innovative power generation modules and optimized heat exchanger designs into the application of waste heat recovery thermoelectric generators, marking a significant advancement in the field of thermoelectric generators.

Multi-scale CuS-rGO pyramidal photothermal structure for highly efficient solar-driven water evaporation and thermoelectric power generation

Integrated water evaporation and thermoelectric power generation system (IWETPGS) has been recognized to be a promising strategy for the utilization of solar energy. Herein, we developed a new type of IWETPGS with multi-scale pyramidal photothermal structures. They featured three-dimensional pyramidal structures with microscale gradient porous copper foams, as well as micro/nanoscale CuS nanowires and reduced graphene oxide (rGO) composite materials. They combined the merits of efficient multiple refraction and absorption of light, broad-spectrum absorption capabilities of rGO and high near-infrared extinction coefficient of CuS, as well as fast water transportation by gradient porous matrix. These photothermal structures induced a photothermal conversion efficiency of 97.6%. An IWETPGS integrating these structures with a thermoelectric generator (TEG) and microchannel heat sink was developed, and outstanding evaporation and output power performance were obtained simultaneously with an evaporation rate of 2.29 kg/m2h and maximum output power of 1.32 W/m2 under 1 sun illumination. Outdoor tests showed that an average daily water production of 12.1 kg/m2 and a maximum power generation of 5.55 W/m2 was obtained. This work provides a high-performance multi-scale CuS-rGO pyramidal photothermal structure to achieve freshwater and thermoelectric power co-generation, which provides potential opportunities for freshwater and electricity supply in remote areas.

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.

Impacts of distributed thermal and electric contact resistance on performance and geometric optimization of thermoelectric generators

Thermal and electric contact resistance (TCR/ECR) critically impact performance and geometric optimization of thermoelectric generators (TEGs). However, conventional treatments usually ignored or simplified them as lumped variables, neglecting their actual distributions across the TEG system. In this study, we proposed a multi-physical model to characterize TEG performance with explicitly specifying TCRs/ECRs at different TEG interfaces (locations). The numerical results show that the lumped-variabletreatment led to maximal overestimations of 16.9 % and 24.5 % in the TEG output power and efficiency, respectively, compared to the results with distributed TCR in this article. Importantly, it also reveals that the TEG performance was susceptible to the TCR location—the interfaces on the cold side exerted more negative impacts than those on the hot side. Furthermore, reducing both TCR and ECR could improve TEG performance and reducing TCR is more effective. It is shown that an 80 % reduction in TCR increased the maximum TEG output power by 35.6 %, while the same reduction percentage in ECR only improved it by 8.8 %. As to geometric optimization, an optimal TE leg height equal to 0.6 mm was obtained for the maximum output power. This contrasts with previous studies without considering TCR and ECR, which always favoured shorter heights. As for copper electrodes, their optimal heights were in the range of 0.2–0.4 mm corresponding to the maximum efficiency, far smaller than those (0.7–1.2 mm) obtained when TCR/ECR were neglected. The latter even further resulted in a reduction in the maximum efficiency by more than 1 % compared to its true peak. In this study, all these numerical results clearly elucidate the important impacts of distributed TCR and ECR on TEG performance, and provide a comprehensive and balanced guideline for TEG design.

Optimization of Heat Sink Geometry for Improved Thermoelectric Generator Efficiency

Optimization of Heat Sink Geometry for Improved Thermoelectric Generator Efficiency

Effect of heat dissipation on the performance of thermoelectric generator

Thermoelectric generators (TEGs) can directly convert heat into electricity with the advantages of ultra-silence, fast response, and high-power density, but the practical application is limited by their low conversion efficiency. We find that the heat dissipation caused by heat convection and heat exchange is an important factor in inhibiting the conversion efficiency. To reveal the effect of heat dissipation on the performance of TEGs, the theoretical model for the thermal-electric coupling of TEGs is built, while experimental research is taken to determine key parameters of heat transfer in theory and to verify theoretical models. Results show that both heat convection and heat exchange in TEGs severely inhibit the conversion efficiency by improving the heat consumption, but have no effect on the output power for a determined temperature gradient. According to theoretical results, the size of TEG is designed to improve the conversion efficiency by suppressing the impact of heat dissipation, while a vacuum encapsulation is proven to have the ability to eliminate both heat convection and heat exchange. As a result, the conversion efficiency of a Bi2Te3-based TEG is improved by 52% from the commercial TEGs. These findings provide a theoretical basis and guidance for obtaining high-performance TEGs.

Maximum power and the corresponding efficiency for a Carnot-like thermoelectric cycle based on fluctuation theorem.

Here, we investigate the maximum power and efficiency of thermoelectric generators through devising a set of protocols for the isothermal and adiabatic processes of thermoelectricity to build a Carnot-like thermoelectric cycle, with the analysis based on fluctuation theorem. The Carnot efficiency can be readily obtained for the quasistatic thermoelectric cycle with vanishing power. The maximum power-efficiency pair of the finite-time thermoelectric cycle is derived, which is found to have the identical form to that of Brownian motors characterized by the stochastic thermodynamics. However, it is of significant discrepancy compared to the linear-irreversible and endoreversible-thermodynamics based formulations. The distinction with the linear-irreversible-thermodynamics case could result from the difference in the definitions of Peltier and Seebeck coefficients in the thermoelectric cycle. As for the endoreversible thermodynamics, we argue the applicability of endoreversibility could be questionable for analyzing the Carnot-like thermoelectric cycle, due to the incompatibility of the endoreversible hypothesis that attributes the irreversibility to finite heat transfer with thermal reservoirs, though the distinction in the mathematical expressions can vanish with the assumption that the ratio of thermoelectric power factors at the high and low temperatures (γ) is equal to the square root of the temperature ratio, γ=sqrt[T_{L}/T_{H}] (this condition could significantly deviate from the practical case). Last, utilizing our models as a concise tool to evaluate the maximum power-efficiency pairs of realistic thermoelectric material, we present a case study on the n-type silicon.

An experimental study on the performance of TEGs using uniform flow distribution heat exchanger for low-grade thermal energy recovery

Low-temperature thermal energy (<100 °C) is widely present in energy systems and nature, and its utilization is of great significance for energy conservation and carbon reduction. Thermoelectric generator (TEG), without refrigerant and moving parts, can directly convert low-temperature thermal energy into high-grade electricity through the Seebeck effect. One of the biggest defects of TEG is the low efficiency from thermal to electricity. To improve the efficiency of TEG, a staggered fin was arranged in the main flow area for the heat exchanger. Meanwhile, a header with pin-finned and variable triangle geometry is applied in the inlet and outlet of heat exchange to uniform fluid flow. A TEG experimental system containing the heat exchanger whose header with pin-finned and variable triangle geometry was built to evaluate the output performance at variable load resistance, hot and cold source temperature, flow rate, flow direction, and electrically connected array configurations. Moreover, experimental results were compared with other literature. When the inlet hot and cold source temperatures are 40.8–81.0 °C and 20.0–30.0 °C, the TEG system could generate around 0.6–18.8 W with a flow rate of 5 L/min. The TEG system has relative high output performance and a low flow resistance compared to other literatures, and it is the potential to recover low-grade thermal energy recovery.

Enhancing Ocean Thermal Energy Conversion Performance: Optimized Thermoelectric Generator-Integrated Heat Exchangers with Longitudinal Vortex Generators

The effective utilization of renewable energy has become critical to technological advancement for the energetic transition from fossil fuels to clean and sustainable sources. Ocean Thermal Energy Conversion (OTEC) technology, which generates electricity by leveraging the temperature differential between surface and deep ocean waters, enables stable power generation around the clock. In this domain, the combination of thermoelectric generators (TEGs) and heat exchangers has exhibited immense potential for ameliorating the deficiencies of conventional OTEC. This study uses finite element numerical simulation of the COMSOL5.5 software to investigate the fluid dynamics characteristics of heat exchangers with flat fins and different types of longitudinal vortex generators (LVGs) under the same number of fins. This research encompasses heat exchangers with rectangular, triangular, and trapezoidal LVGs. Concurrently, the analysis examines how the vortices generated by the LVGs influence the thermoelectric performance of the TEGs. The results demonstrate that heat exchangers integrating flat fins and LVGs can enhance the power generation efficiency of TEGs. However, the pumping power required by the LVGs constrains the thermoelectric conversion efficiency. Compared to rectangular and triangular LVGs, trapezoidal LVGs achieve a superior balance between output and pumping power. Heat exchangers utilizing trapezoidal LVGs can attain the highest TEG thermoelectric conversion efficiency with a specific seawater flow velocity. Overall, these findings provide valuable reference information for applying TEGs and heat exchangers in OTEC design.