Performance Of Thermoelectric Generator Research Articles

Overall performance optimisation of tapered leg geometry based solar thermoelectric generators under isoflux conditions

The performance of thermoelectric devices improves either by changing the thermoelectric material properties or the geometry of the thermoelectric leg. Many research papers show that the tapered leg geometry improves the performance of thermoelectric generators (TEGs). However, they assume isothermal conditions across the hot and cold junctions of both variable area and rectangular area leg-based TEGs. This is rather inaccurate and unrealistic, because when exposed to same heat flux, temperatures vary across the hot and cold junctions of these devices. Scarcely has anything been said pertaining the performance evaluation and optimisation of variable area leg TEGs using realistic isoflux conditions. Therefore, this study presents a thermo-mechanical analysis of variable area and rectangular area leg TEGs, using ANSYS 2020 R2 software, with realistic isoflux boundary conditions instead of previous unrealistic isothermal ones. The leg height, area, external load resistance and optical concentration ratio are optimised. Results indicate that short legs are crucial for maximum power while long legs improve the device efficiencies. Also, although tapered thermoelectric leg TEGs improve the electrical performance of conventional rectangular leg TEGs, they decrease the device mechanical performance and thermodynamic stability. Finally, the optimum ranges in which tapered leg TEG outperforms the conventional device are obtained.

Performance comparison of two micro-channel heat pipe LFPV/T systems plus thermoelectric generators with and without aerogel glazing

A novel photovoltaic/thermal (PV/T) system is designed, which combines Fresnel lens (LF) for linear concentrating, micro-channel heat pipe (MCHP) and thermoelectric generators (TEG) to achieve high electrical and thermal output. Aerogel possesses the characteristic of good heat preservation and thermal insulation, thus, applying transparent aerogel glazing to the LF-PV/T-MCHP-TEG system is proposed, to investigate the effects of the different thicknesses of aerogel on performance and compare the system with the no-aerogel system. The results show that adding aerogel enhanced the thermal performance and TEG's performance. The thermal efficiency of the system with 3 cm aerogel was 25.0% under 800 W/m2 irradiation, 3 concentration ratio, 18 °C ambient temperature, and 15 °C initial water temperature, while that of the no-aerogel system was 23.4%. Besides, using aerogel increased the power of TEG by 6 kJ. Nevertheless, the electrical efficiency of PV and overall efficiency of the LFPV/T-MCHP-TEG system with aerogel were 1.8% and 3.0% lower than those of the no-aerogel system under the same conditions. Therefore, there had to be a trade-off between the benefits of better thermal performance and better electrical performance. Furthermore, the influence of TEG modules, solar irradiation, concentration ratios, initial water temperature, and ambient temperature was also discussed.

Performance analysis and design optimization of a compact thermoelectric generator with T-Shaped configuration

In this study, a compact thermoelectric generator (TEG) configuration composed of T-shaped electrodes and connected P–N thermoelectric legs was developed to improve its performance. Based on the 1D self-consistent numerical model, the electrical impedance matching relations and optimal thermoelectric leg sizes for T-shaped TEG were semi-analytically derived, and demonstrated with a high accurate prediction. The comparison between the developed T-shaped and the conventional π-shaped TEGs was conducted, which indicated that the specific output power was greatly increased by 90.1% under the same given thermal conditions. Furthermore, impacts of the coupled thermal-electrical conditions, thermal conditions and geometric parameters on the performance of T-shaped TEG have been studied in detail. Single-parameter and two-parameter geometric optimizations were also discussed. Then, the optimal geometric size could be obtained under the given heat transfer conditions and external electrical loading. Finally, the optimization of geometric parameters for T-shaped TEG was conducted in different heat transfer conditions. Under the constant heat transfer conditions, the maximum power has improved by 21.9%. The novel structure of the T-shaped TEG proposed could be applied in many application scenarios.

An analytical model for performance prediction and optimization of thermoelectric generators with varied leg cross-sections

With the improvement on materials performance gradually reaching its bottleneck, more and more works focus on optimizing the device structures to seek further performance enhancement of thermoelectric (TE) devices. This paper proposed an analytical model to calculate the performance of thermoelectric generators (TEGs) with varied leg cross-sections considering temperature-dependent material properties. The explicit expressions of output power and efficiency are derived and the model is verified by finite element method (FEM). Furthermore, the optimization of leg geometry for higher device performance is performed based on the presented model, the results show that the key to maximum output power is to minimize the leg resistance; and increasing the leg volume may simultaneously raise the output power and efficiency. In addition, we apply the presented model to optimize the leg shape of a commercial TEG module and find that the optimized geometry can simultaneously achieve an enhancement up to 43.1% for output power and 9.67% for efficiency. The presented model thus may be useful in designing high-performance TEGs and shed considerable light on the principles of TEG design.

Performance enhancement of a thermoelectric system with improved natural convection cooling by utilizing the chimney effect

Due to the lack of sufficient auxiliary electrical energy to drive pumps or fans, the cooling of autarkic thermoelectric systems is confined to the natural convection mechanism. This is regarded as a key weakness and inhibits an adequate overall thermoelectric system performance. In order to enhance the performance of thermoelectric generators (TEG) for powering small consumer units like self-sufficient wireless sensor nodes (WSN), this paper presents a heat exchanger concept to improve the cooling of the TEG. The concept comes without any auxiliary energy and is based on utilizing the chimney effect to improve the cooling rate of a simple fin heat exchanger. With this concept it is experimentally proven, that the electrical output power of a TEG can be enhanced up to 46,2% compared to the conventional passive cooling method with a finned heat exchanger. Furthermore, this paper presents a CFD simulation to reveal further design optimization potential for the proposed heat exchanger apparatus.

Annual performance evaluation of thermoelectric generator-assisted building-integrated photovoltaic system with phase change material

Owing to the economic recession due to the Coronavirus disease (COVID-19) pandemic, energy-efficient building retrofitting has been considered as an integrated solution to recover the economy and maintain global greenhouse gas reduction. As part of retrofitting existing building-integrated photovoltaic systems during building renovations, this study evaluated the energy generation potential of a thermoelectric generator-assisted building-integrated photovoltaic system with a phase change material. The combination of a thermoelectric generator and phase change material with photovoltaic systems results in solar cell temperature reduction and additional electricity output owing to the Seebeck effect, increasing the total generated energy from the system. Simulations of the proposed system were performed using MATLAB R2020a, based on transient energy balance equations. The appropriate melting temperature and thickness of the phase change material were derived to maximize the annual electricity generation of the proposed system from simulations of 12 design days in each month. The proposed system with the selected phase change material conditions exhibited a 1.09% annual increase in generation output and 0.91%, −1.32%, 2.25%, and 3.16% generation improvements from spring to winter, compared with the building-integrated photovoltaic system alone. Theoretically, the proposed system is expected to generate 4.47% more energy by minimizing the thermal resistance of the system and improving thermoelectric generator performance.

Thermoelectric performance and stress analysis on wearable thermoelectric generator under bending load

With the growing popularity of flexible micro-electronics and health-monitoring sensors, wearable flexible thermoelectric generators (TEGs) are receiving attention due to their ability to convert body heat into electricity. In this study, a three-dimensional model of wearable TEGs encapsulated in the PDMS material is established based on the nonlinearly coupled thermoelectric transport constitutive law, large deformation of materials, and the 3-parameter Mooney-Rivlin nonlinear hyperelastic constitutive law of polydimethylsiloxane (PDMS) material. The thermoelectric performance and mechanical reliability of the wearable TEG are investigated under the bending load by employing finite element method. A comparison between numerical results and experimental data is conducted for validation of the model. Effects of the leg shape, filling factor and height of the legs are examined on the thermoelectric performance and mechanical reliability of the wearable TEGs. The optimized dimensions of wearable thermoelectric generators are obtained and analyzed. The results show that, thermoelectric performance and flexibility of the wearable TEG can be enhanced by increasing the number of thermocouples in the TEG. The results of this paper provide useful suggestions for the structural design and practical application of wearable TEGs encapsulated in PDMS materials.

Maximizing Performance of Microelectronic Thermoelectric Generators With Parasitic Thermal and Electrical Resistances

Microelectronic thermoelectric (TE) generators ( $\mu $ TEGs), which are one potential solution to powering energy autonomous integrated circuits (ICs), are often performance limited because of parasitic electrical and thermal resistances in the $\mu $ TEG circuit. Parasitic performance loss can be particularly severe for $\mu $ TEGs using materials with relatively low TE figure-of-merit, such as silicon (Si). In such cases, careful attention must be paid to optimizing the entire $\mu $ TEG circuit, not just the TE material properties. Here, a quantitative model of $\mu $ TEG device performance is developed that includes all significant electrical and thermal parasitics commonly encountered in IC-compatible $\mu $ TEGs. The model gives a pair of coupled quadratic equations that can be analytically or numerically solved to determine power generation and efficiency. For given parasitic resistance and material property values, the model shows that the ratio (called here the packing fraction) of cross-sectional area occupied by TE elements to total cross-sectional area for heat flow per thermopile can be designed to maximize either power or efficiency, but not both simultaneously. For realistic material and device parameters, the optimum packing fraction is often only 1%–10%, lower than what is used in many $\mu $ TEG designs. The model accounts for the reported power generation of some example $\mu $ TEGs and provides guidance toward significant performance improvement.

Performance Analysis of Thermoelectric Generator at Different Hot Surface Temperatures

The most important point in electricity generation with thermoelectric generators (TEG) is to create a temperature difference between its surfaces. The cooling process is usually carried out by liquid coolers or heat sinks. This study aims to examine experimentally and numerically the cooling and electrical conversion performance of TEG with a heat sink having flat fins at different hot surface temperatures, which are 50, 75, 100, 125, and 150°C, respectively. In this context, the experimental and numerical results were compared in terms of surface temperature, voltage, current, and power outputs. It was determined that the electrical performance increased as the hot surface temperature increased. The highest power output was obtained at a hot surface temperature of 150°C, with the value of 1.41 W experimentally and 1.42 W numerically. As a result, the numerical and experimental results were in good agreement both thermally and electrically. After the validation process, the efficiency, power input, and temperature-difference results were given only numerically. In these numerical calculations, it was observed that the efficiency increased with the hot surface temperature, but the increase decreased gradually after the hot surface temperature of 125°C. The results provided beneficial guidelines for the design, modeling, and application of TEGs.

High-performance half-Heusler thermoelectric devices through direct bonding technique

Solid-state thermoelectric generators (TEGs) are promising solution for waste heat recovery. However, they typically suffer from lower conversion efficiency, lack of reliable high temperature device fabrication process and long-term stability. In order to realize high electrical conversion efficiency (ECE) in TEGs, it is critical that in conjunction with high TE materials figure of merit, zT, there is also a reliable TE module fabrication process. This study demonstrates the TEG fabrication process that results in reduced thermal and electrical contact resistances between metal electrodes and TE legs, even at high temperatures (>600 °C). The fabrication approach is demonstrated using p-type ZrCoSb-based and n-type ZrNiSn-based half-Heusler TE materials. High temperature brazing material is used as a filler that enables direct bonding of TE legs to the copper electrode without metallizing legs. This technique improves the TEG performance and stability at high temperatures by minimizing the contact resistance and diffusion at TE leg/electrode interface. The fabricated modules exhibit a high power density of ~11.5 Wcm−2 and an ECE of 9.5% at 670 °C temperature gradient. The module was exposed to longtime soaking at 550 °C in air and was found to exhibit negligible deterioration. These results are highly promising for advancing the TE modules in waste heat recovery applications.

Experimental investigations on the performance of thermoelectric generator as energy conversion system

Energy conversion system based on thermoelectric generator that utilized the residual heat of condenser as heat energy resource and water circulation as a cooling system has been designed. Thermoelectric generator functions as a heat-to-electricity energy conversion by using temperature difference between the two sides of the thermoelectric 4 x 4 x 0.3 cm TEG SP1848 module has been used as a thermoelectric generator that can hold back the temperature up to 125°C. The conductance value of TEG SP1848 is 0.0025 W/K. The important part of energy conversion systems are thermoelectric generator configuration, conductor and cooling system. Conductor is the component which functions as heat transfer media from condenser pipe to thermoelectric generator. The diameter of the condenser pipe in this study was 4.2 cm. The function of cooling system is cooling up the thermoelectric generator cold side in order to enhance the temperature difference between cold side and hot side. The cooling system that used in this research is water cooling that consisting of a water pump, water block, radiator, fan and water. The collecting data has been done by using series configuration of thermoelectric generator and varying the temperature of 40°C -110°C and the resistance of 10Ω-200Ω. The best resistance that can produce the greatest power is 39 Ω. The hot side temperature that can produce the greatest power in this study is 110 °C. The average of power and efficiency of energy conversion system was 0.129 W and 2%.

Numerical investigation on the dynamic response characteristics of a thermoelectric generator module under transient temperature excitations

In this work, a three-dimensional transient numerical model of a thermoelectric generator module considering the temperature-dependent properties and the topological connection of load resistance is proposed to study its dynamic response characteristics. The dynamic output power and conversion efficiency of the thermoelectric generator module under steady and different transient temperature excitations are compared and studied. A time delay exists in the output response of the thermoelectric generator module, and the time delay increases when the temperature rate increases. When the heat source temperature changes rapidly, the corresponding output power, conversion efficiency, and other thermal responses will show a more stable change trend. Moreover, the dynamic response characteristic of the output power is synchronous with that of the conversion efficiency. The periodic temperature excitation may amplify the output power, where the average output power of the sine and triangle waves are 4.93% and 2.82% respectively higher than the steady-state output power. However, the average conversion efficiency of both is almost identical to the steady-state conversion efficiency. The proposed model contributes to predicting the dynamic performance of thermoelectric generators, and can be further extended to the whole thermoelectric generator system.

Performance Optimization of Thermoelectric Generators using Taguchi Method

The thermoelectric generators (TEGs) are devices that are utilized to convert the heat energy into electrical energy directly and the working principle of this device is based on See beck effect. Thermoelectric power production is a smart method for the direct translation of heat energy into an electrical one. This work explores a method to get the optimum process parameters on the performance of various TEGs by finding the conversion efficiency to recover the waste heat and converts it into electricity. For this purpose, an experimental setup was designed and fabricated to determine the performance of TEGs. The TEGs made by Bismuth Telluride (Bi2Te3), Lead Telluride (PbTe), and Aluminium Oxide (Al2O3) were taken for the performance analysis. The process variables are heat input, TEG material and temperature difference. The experiments were conducted by using Taguchi’s L9 orthogonal array to reduce the number of experiments. The results found that the heat input of 90W, TEG material of Bi2Te3 and the temperature difference of 75°C gives the maximum conversion efficiency of 2.45% from thermal to electrical energy. The statistical analysis of variance (ANOVA) showed that the most influential parameter on the performance of TEGs was heat input. The R2 and R2 (adj) values were found to be 93.25% and 86.50%, this shows that the developed model is significant and can predict the optimal solution.

Thermoelectric generator (TEG) technologies and applications

• The state-of-the-art of thermoelectric generators is reviewed comprehensively. • The materials used in TEGs, Figure of Merit, improvement techniques are introduced. • Different configurations of experimental set-ups and prototypes are explored. • The performance of TEGs is investigated with different simulation software packages. Nowadays humans are facing difficult issues, such as increasing power costs, environmental pollution and global warming. In order to reduce their consequences, scientists are concentrating on improving power generators focused on energy harvesting. Thermoelectric generators (TEGs) have demonstrated their capacity to transform thermal energy directly into electric power through the Seebeck effect. Due to the unique advantages they present, thermoelectric systems have emerged during the last decade as a promising alternative among other technologies for green power production. In this regard, thermoelectric device output prediction is important both for determining the future use of this new technology and for specifying the key design parameters of thermoelectric generators and systems. Moreover, TEGs are environmentally safe, work quietly as they do not include mechanical mechanisms or rotating elements and can be manufactured on a broad variety of substrates such as silicon, polymers and ceramics. In addition, TEGs are position-independent, have a long working life and are ideal for bulk and compact applications. Furthermore, Thermoelectric generators have been found as a viable solution for direct generation of electricity from waste heat in industrial processes. This paper presents in-depth analysis of TEGs, beginning with a comprehensive overview of their working principles such as the Seebeck effect, the Peltier effect, the Thomson effect and Joule heating with their applications, materials used, Figure of Merit, improvement techniques including different thermoelectric material arrangements and technologies used and substrate types. Moreover, performance simulation examples such as COMSOL Multiphysics and ANSYS-Computational Fluid Dynamics are investigated.

Performance enhancement of a thermoelectric harvester with a PCM/Metal foam composite

The present numerical investigation examines the performance improvement of thermoelectric generators (TEGs) by using phase change materials (PCM) and porous medium. Due to the high latent heat of PCMs, both sides of the TEG were filled with paraffin RT35 (on the cold-side) and paraffin RT69 (on the hot-side). The PCM in the cold-side of the TEG was used as a heat-sink whereas the PCM in hot-side of the TEG was used to reduce the output voltage fluctuations. Since the system was periodically subjected to heat flux from an external heat source, the paraffin in the hot-side of the TEG was also used to generate a continuous thermal heat when the heat source was cut-off. To increase the thermal conductivity of the phase change material, this investigation studied the effect of using the copper porous medium with different porosities (0.80, 0.90, and 0.95) and three different pores per inches (PPI) as 10, 20, and 40. The results show that the use of porous on the cold-side of the TEG produces more electrical energy and output voltage compared to (i) having porous medium on the hot-side and (ii) using PCM without porous medium on both sides of the thermoelectric generator. Furthermore, the results indicated that the TEG performance enhanced by increasing PPI and reducing porosity. As a result, by increasing the PPI from 10 to 40 (at 0.80 porosity) and by reducing porosity from 0.95 to 0.80 (at PPI 20), the electricity generated increases by 13.57 and 5.36%, respectively.

Optimization of Power and Efficiency in a segmented legs STEG using the Taguchi method

In the recent times, many researchers have concentrated on the development of thermoelectric materials with higher values of figure of merits to enhance the conversion efficiency. It have been observed in some of the previous studies that the figure of merit and hence, the performance of thermoelectric modules can be enhanced using the module with segmented legs of two or more thermoelectric materials. In this study, the application of segmented thermoelectric modules in a solar assisted thermoelectric generator have been presented. PbTe and BiTe alloys are used in the segmented module. Except the figure of merit, the performance of thermoelectric generator is also dependent on temperatures across modules, load resistance and various design parameters such as leg geometries, cross sectional area of legs etc. So, Taguchi method of optimization was employed using five factors and five levels design to optimize the power and conversion efficiency. The power and efficiencies are mathematically calculated at different combinations according to L25 orthogonal array. The maximum power output is predicted up to 31.52 W and conversion efficiency up to 14.61% using The Taguchi analysis. Analysis of Variance method is also used to analyze general linear model which results into the estimation of contribution percentages of each factor on the power and efficiency.

Effects of Temperature Dependent Thermal Properties and the Side Leg Heat Dissipation on the Performance of the Thermoelectric Generator

The temperature dependent properties and the side leg heat dissipation have serious effects on the output power and efficiency of the thermoelectric generator (TEG). In this paper, a novel steady-state one-dimensional model was developed considering temperature dependence of the properties and the side leg heat dissipation to study TEG performance. The numerical results of the model were compared with the available experimental data and models. The comparison reveals that the deviations for output power and efficiency of TEG are about 3.0 ~ 12.0% and 0.9~17.5% respectively, when the temperature difference between the hot and cold side is within 68 ~ 149 K (The hot side temperature is within 362~452 K). The deviation between the others model and the experimental data exceeds 20% when temperature difference exceeds 103 K. When the temperature difference is above 103 K, the temperature dependent properties and side leg heat dissipation have a pronounced effect on TEG performance. While, the two factors have no obvious influence on TEG efficiency prediction, when temperature difference is below 68 K. The numerical results show that the most influence factor leading to temperature and heat flux non-uniform is the temperature-dependent of material, and followed by Thomson heat and Joule heat.

The Influence of Peltier Effect on the Exergy of Thermoelectric Cooler-Thermoelectric Generator System and Performance Improvement of System

The Influence of Peltier Effect on the Exergy of Thermoelectric Cooler-Thermoelectric Generator System and Performance Improvement of System

Improving transient performance of thermoelectric generator by integrating phase change material

Thermoelectric generator (TEG) based on Seebeck effect, which is well regarded as an effective way for waste heat recovery, has stepped into vision of automotive researchers in the past decades in terms of electricity generation from vehicle exhaust gases. Various driving conditions of the vehicles and fluctuating temperature of the exhaust gases are crucial factors that obstruct the development of automotive TEG. In this study, a novel concept of integrating phase change material (PCM) with TEG for improving transient performance and total efficiency is presented. PCM, as a commonly utilized material for thermal energy storage, reduces the impact of exhaust gas temperature fluctuations on the automotive TEG, thereby improving the efficiency under various driving conditions. According to the thermal properties of the exhaust gases, Pentaerythritol (PE) is selected as the appropriate PCM for the automotive TEG, because of the suitable temperature range for phase transition and extremely low rate of volume change during the phase transition (due to its solid-solid phase change). Experiments are conducted to explore the feasibility of PE integrating with TEG and the capability of improving transient performance of TEG. Results showed that the improvement of open circuit voltage and power output are 0.7% and 1.16%, respectively. The present study provided a guideline for the design and further research of PCM integrated automotive TEG.

Thermoelectric power generator: Field test at Bottle Rock geothermal power plant

There have been many reports on laboratory experiments measuring TEG (thermoelectric generator) power output at different flow rates of water, different temperatures, and other different conditions, but there have been few field tests utilizing geothermal wells. To this end, we designed a geothermal-TEG apparatus that has a six-layer modularized design to allow expanded power production by increasing the number of layers. After demonstrating the TEG's performance in the laboratory, we tested the apparatus in the field at a well located in the Bottle Rock geothermal field in The Geysers, CA, USA. The whole six-layer TEG device could generate about 500 W electricity with a temperature difference of about 152 °C between the hot and cold fluid manifolds, while each individual TEG chip could generate about 3.9 W. The steam pressure at the inlet of the TEG apparatus was about 122 psi, close to the wellhead pressure of 125 psi. After optimizing the field infrastructure, the TEG device could generate electricity without any leak at the wellhead pressure of 125 psi and the temperature over 176 °C (349 °F). The field test of the six-layer TEG device at Bottle Rock geothermal power plant was considered successful, and plans have begun to design and build a TEG device that could produce power up to 20 kW.