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Thermoelectric generator (TEG) with improved performance is a promising technology in power supply and energy harvesting. Existing studies primarily adopt constant material properties to investigate TEG performance. However, thermoelectric (TE) material properties are subjected to considerable variations with temperature. Thus, reasonable doubts have risen concerning the influence level of temperature-dependent material properties on TEG performance. To solve this problem, an efficient and a comprehensive one-dimensional numerical model is developed to fully consider the third-order polynomial temperature-dependent thermal conductivity, Seebeck coefficient, and electrical resistivity. Control volume and finite difference algorithms are compared, and experiments are conducted to verify the developed numerical model. The temperature distribution along the TE leg obviously differs from the parabolic shape, which is a classic temperature distribution under the assumption of constant material properties. Insights find that the local change rate of thermal conductivity and Thomson effect are the essential reasons for the abovementioned phenomenon. It has been found that Thomson heat is released in the part of the leg near the cold-end, whereas it is absorbed in the remaining parts of the leg near the hot-end. The electric power on the basis of constant material properties is confirmed to be accurate enough by the developed numerical model, but the parabolic shape of the TE efficiency can be only obtained when temperature-dependent material properties are considered. Furthermore, it is wise to improve the TE efficiency by structural optimization. The present work provides an efficient and a comprehensive one-dimensional numerical model to include temperature-dependent material properties. New insights into the temperature and heat flux distribution, Thomson influence, and structural optimization potential are also presented for the in-depth understanding of the TE conversion process. [ABSTRACT FROM AUTHOR]

Rapid development of portable electronics promotes the R&D of micro/miniature power sources with high energy density. The high mass energy density and zero emission characteristic of hydrogen show a huge potential to develop powerful portable hydrogen-based power sources. A miniature hydrogen catalytic combustion powered thermoelectric generator (CCP-TEG) is designed and tested in detail. An outstanding catalytic core is prepared with a newly proposed method on the basis of combining H 2 PtCl 6 solution and foamed transition metal. Such catalytic core is demonstrated to provide high combustion temperature, complete combustion, and sufficient heat flux for power generation. Several parameters including input power, equivalent ratio, cooling mode, and load resistance are investigated to clarify their influences on the combustion temperature, electric power, and various efficiencies (combustion, heat collection, TE, and overall efficiencies) of the hydrogen CCP-TEG. The developed hydrogen CCP-TEG is able to generate an electric power of 20.7 W with an overall efficiency of 2.04%, filling the research gap of generating large electric power (>10 W) with sufficiently high overall efficiency (>2%) in the research field of hydrogen CCP-TEG. The generated electric power and overall efficiency are much higher than those in previous hydrogen CCP-TEGs. The prepared catalytic core remains excellent functionality after running for 30 h, and the combustion temperature is as high as 918 K, which ensures the sufficiently high temperature difference for powerful power generation. This study is conducted to illustrate a concrete method on developing a powerful hydrogen CCP-TEG, and to identify further research directions. [Display omitted] • An outstanding catalytic core for hydrogen combustion is newly prepared. • A hydrogen catalytic-combustion-powered TEG (CCP-TEG) is developed. • An electric power of 20.7 W with an overall efficiency of 2.04% is generated. • The generated electric power is larger than those in previous hydrogen CCP-TEGs. • Detail comparisons and comprehensive discussions are made. [ABSTRACT FROM AUTHOR]

It is vital to supply necessary electric power during natural disasters and in deprived regions. A novel heat collector is proposed to improve the capacity of the stove-powered thermoelectric generator (SPTEG). Enclosed combustion walls are constructed with four W-shape copper plates, and act as a whole to be an exceptional heat collector, which was not previously reported in TEG studies. Forty TE modules are installed and two DC–DC converters are employed to stabilize the electric power. Owing to the novel heat collector, the generated electric power reaches 0.024 W/K per unit temperature difference for an individual TE module, which is 200% higher than the previous record (0.008 W/K) when forty TE modules are incorporated. The proposed SPTEG is able to generate a net electric power of 119 W, which is considerably larger than the previous record (75.2 W). The corresponding TE efficiency reaches 3.12%, which is measured at a temperature difference of 140 °C. The startup performance, power load feature, and cooling water flow rate of the SPTEG are studied in detail. Furthermore, one-dimensional theoretical analyses are conducted to explore the SPTEG performance. The theoretical electric power agrees well with the experimental data when DC–DC converters are not involved. Applying DC–DC converters to stabilize the electric power will alter the impendence of the SPTEG, resulting in much lower electric power output than that without DC–DC converters. [ABSTRACT FROM AUTHOR]

The distributed backup power source is vitally important under emergency conditions. Micro combustion powered thermoelectric generator (μ-CPTEG) is a promising candidate as a distributed backup power source. This study innovatively designed an all-in-one configuration to develop an efficient, standalone, and silent μ-CPTEG. The newly proposed all-in-one configuration organically integrates air-preheating, fuel premixing, low-noise combustion, efficient heat collection, and smooth heat compensation and spreading. Such an all-in-one configuration creates a standalone μ-CPTEG with an overall efficiency greater than 4.2 %, which is much larger than those in previous standalone μ-CPTEGs. The present μ-CPTEG incorporates 8 TE modules, and generates an electric power of 53.2 W with a running sound pressure level of 48 dB. Such performance indicates that the average electric power per TE module reaches 6.65 W, corresponding to a TE potential release level of 80.7 % systematically. The overall efficiency, as well as the efficiency of heat recovery, combustion, heat collection, TE and combined heat and power, are explored in detail. Comprehensive discussions are conducted to uncover the dense fog of releasing the TE potential at a systematic level in an μ-CPTEG. The present study provides a concrete method to develop a powerful, standalone, and silent μ-CPTEG. • Powerful, standalone, and silent μ-CPTEG is developed by a new technical framework. • An electric power of 53.2 W with an overall efficiency of 4.2 % is generated. • The running sound pressure level is 48 dB. • The performance is much better than previous standalone μ-CPTEGs. • The energy conversion density of propane by the μ-CPTEG reaches 271 Wh/kg. [ABSTRACT FROM AUTHOR]

Nowadays, with the emergence of high-performance thermoelectric (TE) modules and the continuous optimization of generator structures, hydrocarbon combustion powered mini-/meso-/micro-scale thermoelectric generator (HCP- m -TEG) has shown an energy density not second to that of lithium batteries. This means that HCP- m -TEG now has potential value in some specific commercial fields. However, the single-digit electric power output and over-miniaturized structure of most existing HCP- m -TEGs result in narrow application scenarios. To obtain higher energy density and electric power output, this study constructs a novel compact high-performance HCP- m -TEG prototype based on swirl burner. The total volume and weight of the HCP- m -TEG prototype are only 863.65 cm3 and 2.470 kg. The experimental results show that under extreme, safe, and long-term operating conditions, the electrical power and overall efficiency of the prototype reach 76.93 W-3.81 %, 69.58 W-3.73 %, and 56.21 W-3.29 %, respectively. Compared to previous work, this prototype has achieved excellent energy density. Moreover, the emission, modularity and the practical plans of the prototype are fully discussed. The emission of this prototype is comparable to residential stoves, which ensure safety. By combining different numbers of generation units, several potential application modes can be developed. Overall, this prototype provides a high energy density HCP- m -TEG structure with broad commercial potential. • A novel compact HCP- m -TEG prototype based on swirl burner is constructed. • Featuring extreme compactness, high performance, lightweight and modular design. • The max electric power of 76.93 W with an overall efficiency of 3.81 % is generated. • Providing a foundation unit for HCP- m -TEG commercial applications. [ABSTRACT FROM AUTHOR]

Portable power source attracts great interest recently due to the fast development of electronics. Micro thermoelectric generator (TEG) powered by hydrocarbon fuels is such a potential solution among several possible roadmaps. Efficiency and environmentally friendliness are two major concerns with respect to the abovementioned micro TEG, inevitably involving a complete, clean, and silent combustion technique and excellent heat collection performance. A high capacity, non-premix, and miniature swirl combustor with a special reserved gas channel, incorporated with Swiss-Roll and serpentine heat collectors, is newly designed to initially provide a solution for the abovementioned concerns. The novelty of the present study is to provide a concert method to obtain a swirl-combustion-powered micro TEG with sufficient high systematic efficiency, ultra-clean emissions, and low noise-level. The maximum systematic efficiency is 3.47% at the input power of 673 W, which is 15.6% larger than that (3.01% at 600 W) in an only previous swirl-combustion-powered micro TEG. Combustion efficiency, heat collection efficiency, noise level, CO concentration, and NO pollution reach 98.2%, 92.1%, 61 dB, 32 ppm, and 4 ppm, respectively. Comprehensive discussions on the underlying mechanism to improve the micro TEG performance are performed, and detail comparisons on various aspects with previous studies are made. • Newly designed miniature swirl combustor has a large capacity up to 47.6 MW/m3. • Complete combustion, ultra-clean emission, and 61 dB noise-level are reached. • CO and NO emissions are lower than 32 ppm and 4 ppm, respectively. • Swiss-Roll, serpentine channel, and pin fins are deeply integrated in line. • Heat collection and systematic efficiencies reach 92.1% and 3.47%, respectively. [ABSTRACT FROM AUTHOR]

• An analytical design model for waste heat thermoelectric generator is developed. • The developed model interlinks the material, device, and system levels. • The developed model is verified by experiments and the accuracy is 15.3%. • The designed experimental prototype with 24 modules has excellent performance. • The prototype generates an electric power of 96.6 W with a pressure drop of 375 Pa. Low conversion efficiency of power systems and carbon emission induced climate crisis boost extensive investigations on waste heat utilization, particularly studies of converting waste heat into high-grade electric energy. Thermoelectric generator (TEG) is such a potential solution to abovementioned technical demand. An analytical design model for waste heat TEG, interlinking the underlying three different levels (material, device, and system), is not reported yet though a large number of previous researches intensively studied various important aspects of waste heat TEG with theoretical, numerical and experimental methods. The analytical design model, firstly developed in this work, constructs a straightforward but thoughtful bridge to interlink material, device, and system levels of waste heat TEG, providing multilevel-coupled heat collection surface area, expected electric power outcome, and resulting pressure drop. A high performance customized waste heat TEG can be readily obtained using the present analytical design model with necessary boundary inputs. The effectiveness and accuracy are verified through experimental data. A waste heat TEG prototype with 24 TE modules, exactly machined and assembled according to the developed analytical design model, shows superior performance when compared to previous TEGs. The abovementioned TEG generates an electric power of 96.6 W with a pressure drop of 375 Pa under the exhaust gas temperature of 648 K. Comprehensive discussions are presented to indicate limitations and applications of the developed analytical design model. [ABSTRACT FROM AUTHOR]

In order to utilize waste heat from passenger vehicles by a thermoelectric generator (TEG), a lab-scale TEG with a sufficient low-pressure drop was designed and tested. The waste heat from a 2.0 L petrol engine was simulated by using an air-circulation channel with an adjustable electric heater and a speed control motor. The TEG consisted of an integrated molding designed aluminum-finned heat collector, twenty thermoelectric modules, and a set of water-cooled heat sinks. Experiments were conducted in terms of power load feature, pressure drop, heat collection efficiency, thermoelectric efficiency and overall efficiency. It was found that the hot-end temperature was much lower (46.9%) than the flue gas temperature because the trade-off between fin area and pressure drop had to be considered. The obtained maximum electric power was 36.4 W, and the corresponding pressure drop was 36 Pa. The corresponding heat collection efficiency was 46.5%, and the thermoelectric efficiency was 2.88%, which agreed well with the theoretical prediction of 3.38%. As a result, an overall efficiency of 1.21% was reached. The present work firstly demonstrated a waste-heat-recovering TEG prototype with a balanced overall efficiency of over 1%, and a pressure drop of less than 50 Pa. On the other hand, the maximum electric power was difficult to fully extract. The charging power to a battery with a maximum power point tracking direct current–direct current converter was experimentally verified to work at a much higher conversion efficiency (15.3% higher) than regular converters. [ABSTRACT FROM AUTHOR]

• A mesoscale combustor-powered TEG was designed and optimized. • The contradiction between Bi 2 Te 3 availability and low-temperature limit was solved. • An electric power of 30.7 W was generated with an overall efficiency of 3.21%. • The (EFS / ef TE,max) at P in metrics was proposed to evaluate different TEGs. • The obtained metrics (75.9%/4.23%) at 957 W is higher than previous reports. The recent development of potable power sources is of considerable interest. A mesoscale combustor-powered thermoelectric generator integrated with a mesoscale stagnation-point reverse-flow combustor and a built-in heat exchanger was designed and optimized in this work to augment electric power and overall efficiency. The mesoscale combustor can run at a volumetric heat load of 72 MW/m3. The thickness of heat spreader, input power, equivalent ratio, fuel types, and heat exchanger channel types were explored to optimize the system performance. The optimized electric power of 30.7 W obtained at an overall efficiency of 3.21% was larger than the previous record of 18.1 W at an overall efficiency of 3.01% in 2015. The proposed thermoelectric generator, which was conducted with 13.2 kg of methane, reached an energy density of 300 Wh/kg. The novel design provided a concrete way to solve the contradiction between the availability of Bi 2 Te 3 -based thermoelectric module and its relatively low working temperature. Additionally, a new metrics, which is defined as (EFS / ef TE,max) at P in , was firstly proposed to evaluate various thermoelectric generators, in which different thermoelectric materials, combustion types, and input powers could be involved. The proposed metrics correlates the overall, running thermoelectric, maximum thermoelectric, combustion (reaction), and heat collection efficiencies under different input powers. The power of this metrics was comprehensively discussed by deducing the running thermoelectric efficiencies of various previous works and presenting the performance comparisons of different previous thermoelectric generators. The obtained metrics, that is, (75.9%/4.23%) at 957 W in this work was higher than those in previous studies. [ABSTRACT FROM AUTHOR]

• A mesoscale combustor-powered TEG was designed and tested. • Electric power of 25.7 W was generated with an overall efficiency of 2.69%. • Serpentine channels were designed to enhance heat collection from flue gases. • The proposed parameter EFS reached 81.8% and it is higher than previous reports. Small-scale power sources for portable electronic equipment have been attracting considerable attention in recent years. This paper presents the design and experimental tests of a mesoscale combustor-powered thermoelectric (TE) generator (TEG) with enhanced heat collection. The TE effect, combustion, heat collection efficiencies, and lean blowout (LBO) are investigated in detail. A parameter named system effectiveness (EFS), which is the ratio of overall efficiency to TE efficiency, is proposed to evaluate the performance of combustor-powered TEGs. The obtained electric power of 25.7 W, with an overall efficiency of 2.69%, is higher than previous results. The corresponding hot-end temperature changes from 236 °C to 152 °C along with the flue gas direction, indicating noticeable temperature variation despite the use of pure copper. EFS reaches 81.8%, which is higher than previous reports, and validates that the present TEG is well-designed. The LBO of the combustor is 0.63, and the pressure drop is 463 Pa when the input power is 957 W. Detailed discussions and comparisons with previous studies reveal that the enhanced heat collection design is essential for increasing the residence time of flue gases and EFS. [ABSTRACT FROM AUTHOR]

A compact water-cooled thermoelectric generator (TEG) based on a portable gas stove was designed and analyzed to supply electricity in off-grid scenarios. The TEG incorporates a newly designed heat collector, eight thermoelectric (TE) modules, and a radiator to ensure its portability (5.9 kg) and sufficiency of electric power (12.9 W). Detailed measurements and discussions on power load feature and TE efficiency are presented. Experiments showed that the power generation capability of the proposed TEG is compromised by its compactness over previous water-cooled TEGs. A theoretical model incorporated with heat leaks from various origins has been developed to illustrate that the designed TEG exerts the potential of every TE module, and to reveal the proportion of various heat fluxes. The predicted electric power, various heat fluxes, and TE efficiency agree well with experimental data. The limitations of TE efficiency and the nonlinearity caused by Joule heat are discussed quantitatively. [ABSTRACT FROM AUTHOR]

In order to provide heat and electricity under emergency conditions in off-grid areas, a stove-powered thermoelectric generator (STEG) was designed and optimized. No battery was incorporated, ensuring it would work anytime, anywhere, as long as combustible materials were provided. The startup performance, power load feature and thermoelectric (TE) efficiency were investigated in detail. Furthermore, the heat-conducting plate thickness, cooling fan selection, heat sink dimension and TE module configuration were optimized. The heat flow method was employed to determine the TE efficiency, which was compared to the predicted data. Results showed that the STEG can supply clean-and-warm air (625 W) and electricity (8.25 W at 5 V) continuously at a temperature difference of 148 °C, and the corresponding TE efficiency was measured to be 2.31%. Optimization showed that the choice of heat-conducting plate thickness, heat sink dimensions and cooling fan were inter-dependent, and the TE module configuration affected both the startup process and the power output. [ABSTRACT FROM AUTHOR]