Efficiency Of Thermoelectric Generator Research Articles

Effect of thermoelectric modules with different characteristics on the performance of thermoelectric generators inserted in the central flow region with porous foam copper

The recovery and utilization of waste heat by thermoelectric power generation technology can effectively improve energy utilization efficiency and solve the problem of environmental pollution and resource shortage. In this study, a thermoelectric power generation system is established to recover and utilize high temperature waste heat for thermoelectric power generation. In order to improve the conversion efficiency of thermoelectric generator, porous foam copper is inserted into the central flow region of thermoelectric generator to enhance the heat transfer effect at the hot side, and the thermoelectric generator Comprehensive Performance (TEGCP) as a evaluation standard is used to analyze the performance of thermoelectric generator under the porous foam copper central flow region inserted method. The results show that the thermoelectric module with low thermal conductivity and high electrical conductivity can play a better performance in the thermoelectric generator. Moreover, the heat exchange capability of the thermoelectric generator heat exchanger can be significantly increased when the porous foam copper is inserted in the central flow region. Compared with an insert-free thermoelectric generator, the output power of the thermoelectric generator using porous foam copper with high pore density and high volume ratio is increased by 2.3 times. Through the TEGCP that, the use of 15 mm thickness (75 % volume ratio), 20PPI porous foam copper with the module KTGM161-18 and the central flow region inserted method has the best influence of the thermoelectric generator.

Thermal design of solar thermoelectric generator with phase change material for timely and efficient power generation

Solar thermoelectric energy-generation technology is being developed to mitigate the limitations of solar cells. Thermal management is essential to creating highly efficient and stable solar thermoelectric generators (STEGs). Phase change materials (PCMs) can be used to improve the performance of STEGs. In this study, we numerically investigate the heat transfer, thermal energy storage, and thermoelectric energy conversion in an STEG with PCMs (STEG-PCM). Based on a parametric study, we present thermal design guidelines for the configurations of an STEG-PCM and the thermal properties of PCMs by considering both the thermoelectric generation performance and thermal stability of the STEG-PCM. We also show that the PCM-impregnated structure is the most crucial component of the STEG-PCM in the thermal design based on a sensitivity analysis. To find the optimal design of a PCM-impregnated structure, topology optimization is performed for the STEG-PCM focused on daytime thermoelectric generation performance. The topology-optimized PCM-impregnated structure shows a thermoelectric generation performance close to that of an STEG-PCM whose PCM-impregnated structure is assumed to be an ideal mixture of PCM and framework material. This study explains how PCMs affect thermal energy transport and conversion in an STEG and sheds light on a highly efficient and stable STEG system.

Complete magnetic control over the superconducting thermoelectric effect

Giant thermoelectric effects are known to arise at the interface between superconductors and strongly polarized ferromagnets, enabling the construction of efficient thermoelectric generators. We predict that the thermopower of such a generator can be completely controlled by a magnetic input signal: Not only can the thermopower be toggled on and off by rotating a magnet, but it can even be entirely reversed. This in situ control diverges from conventional thermoelectrics, where the thermopower is usually fixed by the device design.

Grading studies for efficient thermoelectric devices using combined 1D material and device modeling

The efficiency at which thermoelectric generators (TEGs) can convert heat into electrical energy is governed by the properties of the employed functional materials. For a given thermoelectric (TE) material, efficiency needs to be maximized by adjusting, e.g., the carrier concentration n. Usually, chemically homogeneous materials with a constant n along the leg are employed to fabricate TEG. However, for most TE materials, the optimum n has a pronounced temperature dependence, typically increasing toward the hot side of the leg. A local variation of n, either continuously (grading) or discontinuously (segmenting), thus has the potential to increase the efficiency of TEGs substantially. Predictions on efficiency gain are challenging, and an adequate physical model for the thermoelectric transport properties in the material as well as the device is required here. To address this challenge, we have combined a two-band model to describe the material properties with a device model based on the solution of the one-dimensional heat equation. Using Mg2Sn as an example, we have adjusted the n profile to maximize the thermoelectric figure of merit locally. We show that this would result in an increase in conversion efficiency by more than 7% for cold and hot side temperatures of 300 and 700 K, respectively. Using a thermoelectric self-compatibility criterion, we verify that the calculated n profile is indeed close to the best possible one. The presented methodology can be transferred to other material systems, and we show that it can also be used to calculate the effect of other, practically more feasible n profiles.

Bismuth telluride based efficient thermoelectric power generator with electrically conducive interfaces for harvesting low-temperature heat

Nearly 50% of the heat released by various sources in the environment is found in the temperature range below 573 K. Thermoelectric generators (TEGs) offer a robust solid-state energy conversion mechanism to harvest this waste heat into useful electrical energy. To develop efficient TEGs, a prerequisite is to couple n - and p -type thermoelectric materials through metallic interconnect, with low specific contact resistivity ( ρ c ). The realization of low ρ c involves several critical factors, such as the chemical and mechanical stability, which should be carefully optimized to achieve consistent TEG performance under long-term operation. In the present work, we have demonstrated the concept of a graded interface layer to realize electrically conducive contacts in mechanically alloyed n -Bi 2 Te 2.7 Se 0.3 and p -Bi 0.5 Sb 1.5 Te 3 thermoelectric material (TM) having moderate figure-of-merit ( zT ). We have reproducibly achieved electric contacts with low ρ c in these materials (∼59-71 μΩ-cm 2 ) using a graded layer of Ni. Using the established approach, the conversion efficiency ( η exp ) of 6.5% (±10%) is demonstrated for the temperature difference (Δ T ) of 270 K. Achieved η exp in the present work matches well with the simulated conversion efficiency ( η sim )∼7.0%, and is one amongst the best-reported efficiencies surpassing the state-of-the-art commercial modules.

Comparison and Parametric Analysis of Thermoelectric Generator System for Industrial Waste Heat Recovery with Three Types of Heat Sinks: Numerical Study

In this study, a fluid–thermal–electrical multiphysics numerical model was developed for the thermal and electrical analyses of a heat sink-based thermoelectric generator (TEG) in a waste heat recovery system used for casting a bronze ingot mold. Moreover, the model was validated based on experimental data. Heat sinks were installed on the hot side of the TEG module to recover the waste heat from the flue gas generated in the casting process. The numerical results of the thermal and electrical characteristics of a plate fin (PF)-based TEG showed good agreement with the experimental findings. Numerical simulations of heat sinks with three different fin structures—PF, cylinder pin fin (CPF), and rectangular pin fin (RPF)—were conducted. The simulated system pressure drop, hot- and cold-side temperature difference in the TEG module, TEG power output, and TEG efficiency were compared for the differently designed fin structures. The results showed that for the same fin area, the CPF heat sink-based TEG system achieved a lower pressure drop, higher power output, and higher efficiency than the other two designs. This was particularly true when the velocity of the flue gas and the fin height exceed 5 m/s and 28.6 mm, respectively. Therefore, for low and high flue gas velocities, PF and CPF heat sinks are recommended as the best choices, respectively.

The impact of Clay as wall material on Thermoelectric power generation and flame–wall interaction

The use of clay as the combustor wall material for direct heat-to-electricity conversion using a Thermoelectric generator (TEG) was evaluated in a side-wall configuration burner. The influence of different fuel blends (Methane, Biogas and Biogas + H2) and flame work conditions in TEG power and efficiency are discussed. Flame–wall interaction (FWI) of the laminar side-wall quenching (SWQ) premixed V-flame was investigated. Heat release rate (HRR) and quenching distances were analysed with the chemiluminescence of excited OH* and CH* radicals. The gases velocity field was studied with Particle Image Velocimetry (PIV). For comparison, a galvanized steel (GS) plate was used in the same working conditions. We found that the efficiency (ηTEG) and electrical power (PTEG) losses between materials increases with flame temperature. Quenching distances (dq) were larger in the flame clay wall interaction. Flame quenching was governed by heat losses independently of the wall but the impact of convection was more significant when using the clay wall.

Micro-scale heat and electricity generation by a hybrid solar collector-chimney, thermoelectric, and wind turbine

In the present study, a hybrid system that is fueled with solar energy is proposed. The system includes a solar air collector, solar chimney, thermoelectric generators, and Savonius wind turbine. The absorber plate and the passing air in the duct of the collector act as the heat source and heat sink of the thermoelectric generators respectively. As the air receives heat, it becomes less dense and goes up in the chimney due to buoyancy and the chimney effect. The chimney provides the required air velocity for the wind turbine. In addition, the hot air can be used for other purposes later, such as heating, or drying processes. The results reveal that the efficiency of solar air collector, thermoelectric generator efficiency, and power coefficient of Savonius wind turbine in a certain hour are 61%, 4.54%, and 19.56%, respectively. The average velocity of outlet air from the chimney is 2.32 m/s which can produce 2.17 W by the wind turbine. Additionally, the economic analysis demonstrated that net present value, and payback are approximately 19,707 $ and 1.34 years. Finally, the environmental analysis showed that this system has the potential to reduce emitted carbon dioxide by 5111 kg/year.

Influence of geometric parameter and contact resistances on the thermal-electric behavior of a segmented TEG

Thermoelectric (TE) generation technology plays an increasingly significant role in a global environment. A desirable approach to improve the efficiency of thermoelectric generator (TEG) is to segment the n- and/or p-leg into several parts with different materials for increasing the average thermoelectric figure of merit of the legs, and to operate with a relatively larger temperature gradient. In this study, a three-dimensional model is developed for the performance analysis of a segmented TEG, and the geometric design optimization of the TEG is examined numerically with the use of the temperature-dependent thermoelectric materials. Specifically, the temperature, heat flow, electric potential, electric current and Joule heating in the thermoelectric modules are investigated in detail. Also, the efficiency and effectiveness of the TEG is analyzed with the design variables such as the ratio of cross-sectional area of p-leg and n-leg, the length ratio of different materials in the segmented leg, and the geometry configurations of p- and n-legs. Furthermore, the effect of the contact resistance on the TEG performance is considered. The results show that a proper design of the geometric parameters can lead to an optimal design of thermoelectric generation systems with higher efficiency.

The highly disordered Zintl phase Ca10GdCdSb9 – New example of a p-type semiconductor with remarkable thermoelectric properties

Ca10GdCdSb9 is a new Zintl phase with a large unit cell volume (∼2500 Å3) and a very complex, disordered structure, which can drive the realization of ultralow thermal conductivity in this material. The measured Seebeck coefficient, α, for single-crystalline Ca10GdCdSb9 approaches 350 μV/K at 600 K. The experimentally determined electrical resistivity of Ca10GdCdSb9 is very low, leading to a remarkably high-power factor PF of 23.2 μW/cm·K2 at 460 K. The extraordinary PF value in this material, higher than those of the currently known state-of-the-art materials within the same temperature range, suggests that the Ca10RECdSb9 material system (RE = rare earth metal) could serve as a viable playground to harnessing new efficient thermoelectric generators.

Future Prospect of Rare Earth Element Free Materials for Thermoelectric Generators

Almost all traditional energy sources are on the point of rapid depletion due to over use. There is demand for alternative renewable energy sources, and thermoelectric generators (TEGs) are one of the rising solutions. TEGs are a new class of solid-state devices that transform waste heat energy directly into electricity using Seebeck effect. The efficiency of TEGs is governed by dimensionless quantity called Figure of merit (ZT), which plays an important role to determine the overall sustainability of TEGs. Traditional thermoelectric generators have a poor efficiency (12-20%), which is a disadvantage. To obtain higher value of ZT, the prime emphasis is given towards material engineering as the efficiency solely depends on the materials selection. The investigation is on earth-abundant, cost-effective, low-toxic innovative nanomaterials. In addition, the paper covers various elements for TEGs with prime focus towards rare earth free materials and their emerging trends.

Improving the performance of a solar thermoelectric generator using nano-enhanced variable area pins

Despite the desirable perks offered by solar thermoelectric generators (TEGs), their efficiencies are nowhere close to those of solar photovoltaic systems. This has limited their large-scale reliance for power generation and competitive market advantage. It has been established that the use of variable area pins (VAPs), and nanomaterials, in place of traditional bulk semiconductor materials, have improved the performance of TEGs. However, more work is still needed to further improve the efficiency of TEGs. Therefore, we model a full nano-enhanced VAP TEG module with 127 thermoelectric pairs in three-dimensions using ANSYS 2020 R2. The shortcomings of the previous studies on VAP TEGs are also discussed and addressed. Results indicate that the power density and efficiency of the nano VAP TEG are 12x and 6x higher than that of the traditional bulk semiconductor VAP TEG, respectively.

Multi-criteria evaluation, and dynamic modeling of combining thermal photovoltaic and thermoelectric generators to extend electricity generation at night

Thermoelectric-generator is combined with thermal-photovoltaic in two proposed cycles. The first cycle is an once-through water flow from the collector to the storage tank, and the second one with circulating water from the storage tank to the collector. The thermoelectric-generator extends electricity generation using the stored hot water in the storage tank during the night and also can reduce the size of battery bank and solar panels in off-grid systems. Both cycles are modeled and the thermal-photovoltaic, and thermoelectric-generator models are validated, and good agreement is achieved. The heat source and heat sink fins are designed in details. The thermoelectric-generator efficiency is low due to low temperature of hot water. According to the results, the first cycle is more efficient from the energy, exergy, environmentally, and economic point of views. In addition, both cycles have positive net present value (NPV) for interest rates of less than 10% but the first cycle is more safe for investment because its NPV will be zero at interest rate of 15%. The sensitivity analysis showed that the economics of the cycles is more sensitive to the interest rate. In addition, the first cycle with a photovoltaic thermal (PVT) area of 1.623 m2 reduces carbon dioxide generation of about 365.1 kg per year.

Optimization of hybridization strategy for improving the efficiency of thermoelectric generator to recover automobile exhaust waste heat

This paper investigates the existing efficiency formulations of a thermoelectric generator (TEG) and compares them with overall efficiency formulation (η overall). As TEG efficiency is the key factor in TEG performance, η overall formulation is validated and compared to the maximum efficiency (η max) formulation with consideration of temperature independent figure of merit (ZT). We have found that the (η max - η overall) is minimum (1.5%) at low temperature difference (100 K) and it increases (up to 12.67%) when temperature difference increases (up to 800 K). η overall is close to η max at low temperature difference but when temperature difference increases, η overall shows the overestimation of the efficiency results. Compatibility factor is the crucial factor for effective hybridization and segmentation of thermoelectric materials. Thermoelectric materials of Half-heusler alloys of Hf0.75Zr0.25Ni0.9Pd0.1Sn0.975Sb0.025 and FeV1.2−xTixSb (x = 0.4) are considered for the p-n couple and TEG module design. The exhaust thermoelectric generator (ETEG) system consisting of 56 TEG modules is proposed to recover the automobile exhaust waste heat. Output power of 51.52 W is obtained from the ETEG system at a temperature difference of 458 K. At a temperature difference of 800 K (when cold end temperature is fixed at 315 K and hot end temperature vary up to 1115 K), the ETEG system can achieve 75.8 W of power. This ETEG system also provides an additional advantage in the life increment of the muffler due to a reduction in peak temperature. The overall efficiency of the proposed ETEG system is found to be 7.81%.

First principles study of monolayer Sb2S2Te and a mathematical model of a thin-film thermoelectric generator with maximum power point tracing

The result of the structural, electronic and thermoelectric performance of monolayer Sb2S2Te, which is a bran-new material, is calculated by using the method of full-potential linearized augmented plane-wave (FP-LAPW), and the exchange-correlation potential selected in this paper is generalized gradient approximation (GGA) scheme. There are no negative frequencies in the calculated phonon spectra, which demonstrates that dynamics of monolayer Sb2S2Te is stable in theory. The average value of lattice thermal conductivity (κl) is smaller than that of other thermoelectric (TE) materials, and monolayer Sb2S2Te has larger figure of merit (ZT) comparing with other well-known materials. According to the TE parameters (Seebeck coefficient S, electrical conductivity σ, electronic thermal conductivity κe and lattice thermal conductivity κl) of monolayer Sb2S2Te, an idealized model of thermoelectric generator (TEG) and a realistic model of maximum power point tracking (MPPT) are built. In addition, this paper studies the influence of different temperature zones, different temperature differences, cross sectional area, height and the number of P–N junction on output power and conversion efficiency of TEG. The results of physical calculation and simulation models show that the conversion efficiency of TEG of monolayer Sb2S2Te is larger than or close to that of other well-known materials, and the tracking accuracy of MPPT proposed in this paper is higher than or close to that of other researches.

Thermal-hydraulic analysis of heat pipe reactor experimental device with thermoelectric generators

Heat pipe reactor relies on heat pipes to transfer the fission energy generated in the core to the secondary loop or thermoelectric conversion system. In our group's design, thermoelectric generators (TEGs) are selected to convert fission energy to electricity. In this paper, we established a heat pipe reactor experimental device with TEGs. To verify the heat transfer performance of the heat pipes and the thermoelectric conversion efficiency of TEGs, steady-state experiments were carried out. The minimum temperature drop between the evaporator and condenser sections of heat pipes can reach 6.4 °C. The maximum output power of TEGs can go 74.4 W. The thermoelectric conversion efficiency is about 8.0%. The Computational Fluid Dynamics (CFD) method is used to simulate the steady-state operation of the experimental device. After comparing the simulation results with the experimental data, the temperature error of the heat pipes is less than 26.8 °C, and the temperature error of the TEGs is less than 17.3 °C. A CFD simulation method for heat pipe reactor steady-state operation is presented based on the verification and validation.

Investigation of temperature gradient between ambient air and soil to power up wireless sensor network device using a thermoelectric generator

This paper proposes a study of an energy harvesting system for powering wireless sensor network (WSN) devices. The thermal energy harvesting system used is based on the thermal energy source between ambient air at the soil surface with five depth levels. Measurement was taken for 46 days in a garden area located in Melaka, Malaysia. A feasibility study of soil temperature measurement to obtain a temperature gradient can be used for harvesting by using thermoelectric generators (TEG) modules. Then, the efficiency of TEG with several different configurations based on temperature gradient data has been tested in the laboratory. The results revealed that the depth of soil 6 cm between sensors 1 and 3 will gave the best representation of level average temperature different around 1 ℃. Based on the temperature gradient data, the combination of three TEG SP1848 in a series connection with DC-DC step-up circuit DC1664 will produce an optimum voltage output of about 3 V. This output voltage is enough to operate low power IoT device derived from thermal energy.

Research on Module Layout and Module Coverage of an Automobile Exhaust Thermoelectric Power Generation System

Due to the low efficiency of thermoelectric generators (TEGs), many scholars have focused on the structural optimization of TEGs rather than on the optimization of the layout of thermoelectric modules. We aimed to investigate the effect of module layout on the output power of an automotive exhaust thermoelectric power generation system. The module spacing and module coverage ratio were compared under different working conditions based on a numerical simulation. The results show that, under high-temperature conditions, when the module spacing expands from 5 mm to 35 mm, the output power growth rate of modules of different sizes ranges between 8% and 9%. Moreover, under low-temperature conditions, a high coverage ratio of modules will not increase the total output power but, instead, make it decline. In fact, choosing a larger-size module can improve the temperature uniformity, thereby increasing the output power of the automotive thermoelectric power generation system. Hence, the present study has verified that, under different working conditions, different module layouts and module coverage ratios have an impact on the output power of the thermoelectric power generation system, which sheds new light on the improvement of automotive thermoelectric power generation systems.

Effect of Surfactants on the Thermoelectric Performance of Double‐Walled Carbon Nanotubes

Thermoelectrics are a promising solution to the recovery of some of the 60% of the worldwide energy wasted as heat. However, their conversion efficiency is low and the best performing materials are brittle, toxic, and made of expensive ceramics. The challenge in developing better performing materials is in disrupting the electrical vs thermal conductivity correlation, to achieve low thermal conductivity simultaneously with a high electrical conductivity. Carbon nanotubes allow for the decoupling of the electronic density of states from the phonon density of states and this paper shows that flexible, thin films of double‐walled carbon nanotube (DWCNT) can form effective n‐ and p‐doped semiconductors that can achieve a combined Seebeck coefficient of 157.6 µV K−1, the highest reported for a single DWCNT device to date. This is achieved through selected surfactant doping, whose role is correlated with the length of the hydrocarbon chain of the hydrophobic tail group of the surfactant’s molecules. CNTs functionalized with Triton X‐405 show the highest output power consisting of a single junction of p‐ and n‐type thermoelectric elements, reaching as high as 67 nW for a 45 K temperature gradient. Thus enabling flexible, cheaper, and more efficient thermoelectric generators through the use of functionalized CNTs.

Thermoelectric and electrical characteristics of SmS ceramic samples after exposure to a pulsed magnetic field

Samarium monosulfide (SmS) is a promising material for creating thermoelectric generators (TEG), gas sensors and strain gauges. Despite the high values of the generated thermo electromotive force (TEMF) (α ≈ 170–350 μV/K), methods for increasing the efficiency of TEGs based on SmS are of considerable interest. One of these methods can be short-term effects of magnetic fields, including pulsed ones, on these materials. The action of a pulsed magnetic field (PMF) leading to an increase in TEMF (UT) of SmS ceramic samples is found. Samples that are not subjected to high frequency currents (HFC) annealing show an increase in UT of 44.54%–62.18% (from 11.9 to 17.2–19.3 mV). The conductivity (σ) of the samples is ∼ 22 Ω−1/cm and is insensitive to short-term exposure to a PMF. Samples that undergo HFC annealing show an increase in UT of 23.47%–41.31% (from 21.3 to 26.3–30.1 mV) after exposure to a PMF. The conductivity of the samples is ∼ 15 Ω−1/cm and after a short exposure to the PMF is changing non-monotonically, with an increase in the overall instability. The difference in the values of UT and σ can be explained by presence of an ordered grain structure and a significant amount of the Sm2O2S phase in the samples subjected to HFC annealing. Possible mechanisms of the observed changes are discussed.