Parametrical analysis of the design and performance of a solar heat pipe thermoelectric generator unit

This paper describes a solar heat pipe thermoelectric generator (SHP-TEG) unit comprising an evacuated double-skin glass tube, a finned heat pipe and a TEG module. The system takes the advantage of heat pipe to convert the absorbed solar irradiation to a high heat flux to meet the TEG operating requirement. An analytical model of the SHP-TEG unit is presented for the condition of constant solar irradiation, which may lead to different performance characteristics and optimal design parameters compared with the condition of constant temperature difference usually dealt with in other studies. The analytical model presents the complex influence of basic parameters such as solar irradiation, cooling water temperature, thermoelement length and cross-section area and number of thermoelements, etc. on the maximum power output and conversion efficiency of the SHP-TEG. Simulation based on the analytical model has been carried out to study the performance and design optimization of the SHP-TEG.     

Parametric study of heat-transfer design on the thermoelectric generator system

This study developed an integral thermoelectric generator system with high-performance heat transfer and thermoelectric conversion functions, using the metal pin-fin array coupling with the forced convection heat transfer technique to be the heat absorber and heat sink. A one-dimensional steady heat conduction model with internal Joule heat generation and Seebeck effect was proposed to predict the power generation performance of the present thermoelectric system including the heat absorber and heat sink at various operation conditions. Critical heat-transfer parameters on the design of the integral thermoelectric generator system were derived and discussed. Finally, a series of systematical experiments were performed to simulate an integral thermoelectric generator system operating at the exhaust pipe. The experimental results also demonstrated the validity of the proposed theoretical model.     

两级热电热机的有限时间热力学分析

建立了考虑外部传热影响的两级半导体热电热机模型,用有限时间热力学对牛顿传热规律下两级半导体热电热机的性能进行分析,导出了功率、效率与工作电流的一般关系式,得到了两侧换热器的最优面积分配和热电单元数的最优分配,并分析了多种因素对其性能的影响。     

非均质温差发电器的性能分析

建立非均质温差发电器(TEG)理论模型,考虑热电材料的非均质导热系数以及温差发电器与热源间的传热热阻的影响,分析非均质温差发电器的一般性能.讨论热电元件对数、热导率、高温热源温度对非均质温差发电器性能特性的影响.结果表明,相较于均质温差发电器,导热系数不均匀强度越大,非均质温差发电器的最大输出功率和最大效率越高;热电元...     

A numerical model for thermoelectric generator with the parallel-plate heat exchanger

This paper presents a numerical model to predict the performance of thermoelectric generator with the parallel-plate heat exchanger. The model is based on an elemental approach and exhibits its feature in analyzing the temperature change in a thermoelectric generator and concomitantly its performance under operation conditions. The numerical simulated examples are demonstrated for the thermoelectric generator of parallel flow type and counter flow type in this paper. Simulation results show that the variations in temperature of the fluids in the thermoelectric generator are linear. The numerical model developed in this paper may be also applied to further optimization study for thermoelectric generator.     

Effects of different temperature levels at generator and evaporator on the performance of vapour absorption heat transformers

In a vapour absorption heat transformer, heat is input at both the evaporator and the generator, and useful heat is delivered at the highest temperature at the absorber. Based on an earlier thermodynamic analysis by the authors, the effects of heat supply at different temperature levels to the evaporator and generator are studied here. It is observed that, when two heat sources at different temperature levels are interchanged between the evaporator and generator, there is no noticeable change in the system performance. However, for design and operational reasons, it is recommended that the higher temperature heat source be input at the generator.     

Effect of non-uniform illumination on performance of solar thermoelectric generators

Solar thermoelectric generators (STEGs) are heat engines which can generate electricity from concentrated sunlight. The non-uniform illumination caused by the optical concentrator may affect the performance of solar thermoelectric generators. In this paper, a three-dimensional finite element model of solar thermoelectric generators is established. The two-dimensional Gaussian distribution is employed to modify the illumination profiles incident on the thermoelectric generator. Six non-uniformities of solar illumination are investigated while keeping the total energy constant. The influences of non-uniform illumination on the temperature distribution, the voltage distribution, and the maximum output power are respectively discussed. Three thermoelectric generators with 32, 18 and 8 pairs of thermocouples are compared to investigate their capability under non-uniform solar radiation. The result shows that the non-uniformity of the solar illumination has a great effect on the temperature distribution and the voltage distribution. Central thermoelectric legs can achieve a larger temperature difference and generate a larger voltage than peripheral ones. The non-uniform solar illumination will weaken the capability of the TE generator, and the maximum output power decrease by 1.4% among the range of non-uniformity studied in this paper. Reducing the number of the thermoelectric legs for non-uniform solar illumination can greatly increase the performance of the thermoelectric generator.     

Modeling,experimental study and optimization on low-temperature waste heat thermoelectric generator system

Thermoelectric generation technology, due to its several kinds of merits, especially its promising applications to waste heat recovery, is becoming a noticeable research direction. Based on basic principles of thermoelectric generation technology and finite time thermodynamics, thermoelectric generator system model has been established. In order to investigate viability and further performance of the thermoelectric generator for waste heat recovery in industry area, a low-temperature waste heat thermoelectric generator setup has been constructed. Through the comparison of results between theoretic analysis and experiment, reasonability of this system model has been verified. Testing results and discussion show the promising potential of using thermoelectric generator for low-temperature waste heat recovery, especially in industrial fields. Several suggestions for system performance improvement have been proposed through the analysis on this system model, which guide optimization and modification of this experimental setup. By integrating theoretic analysis and experiment, it is found that besides increasing waste heat temperature and TE modules in series, expanding heat sink surface area in a proper range and enhancing cold-side heat transfer capacity in a proper range can also be employed to enhance performance of this setup.     

Numerical modeling of the performance of thermoelectric module with polydimethylsiloxane encapsulation

This paper presents a 2‐dimensional finite volume model to investigate the performance of thermoelectric module (TEM) with polydimethylsiloxane (PDMS) encapsulation. The voltage and temperature distributions of the TEM under 2 kinds of boundary conditions (constant cold‐side temperature and fixed convection heat transfer coefficient) are studied. To validate the developed model, 2 TEMs with or without PDMS encapsulation are fabricated, and the experimental tests are carried out. Both model predicted and experimentally measured results showed that using flexible PDMS as the encapsulation material for the TEM can lead majority heat flowing through thermoelectric legs and is beneficial for heat harvesting. The geometrical parameters' effects of the PDMS encapsulation and thermoelectric legs are analyzed. Results demonstrated that the usage of larger thermoelectric legs and smaller width of the PDMS encapsulation can generate greater temperature difference and hence improve the voltage of the TEM. Thus, the developed model could be applied for optimal structural design of the flexible TEM with highest performance for heat harvesting.     

Design and testing of a locally made loop-type thermosyphonic heat sink for stove-top thermoelectric generators

The performance of a thermoelectric generator, among other aspects, depends on the use of an effective heat sink. While forced cooling using either air or water (or other coolants) is efficient, it is parasitic on the generated power and/or bulky and inconvenient. Heat pipes are known to be highly effective heat transport devices. Coupled to a thermoelectric generator, these can be used to give acceptable power output. Basing the cooling on water gives low-cost, simplicity, safety, together with good performance. In this work, the design and general performance of a small single-module thermoelectric generator configured for a stovetop waste-heat application and coupled to a locally-made thermosyphonic loop-type heat sink was undertaken. Development and performance cctesting gave mixed results and further numerical and experimental study is under way.     

A solar thermoelectric refrigerator

It is shown that a thermoelectric generator, which draws its heat from the Sun, is a particularly suitable source of electrical power for the operation of a thermoelectric refrigerator. The theory of the combined thermoelectric generator and refrigerator is derived and the ratio of the numbers of thermocouples needed for the two devices is determined. It is found that this ratio can, in principle, be as low as unity, even for unconcentrated solar radiation, though practical considerations indicate that a ratio of 4:1 is preferred in this case. A 4-couple thermoelectric generator has been used to power a single-couple refrigerator. Temperatures below 0°C have been achieved for a temperature difference across the generator of about 40K.     

Modeling, experimental study on the heat transfer characteristics of thermoelectric generator

This paper investigates the heat transfer characteristics of a thermoelectric generator. The influence of heat dissipation intensity to the sub-thermal resistances distribution is experimentally studied. Based on the thermal network analysis and finite time thermodynamics, an analytical model including all thermal resistances (in both thermocouples and external heat exchangers) is developed to predict the performance of the generator. The results show that the computed values of output power agree well with the experimental values. The heat transfer enhancement on the generator cold side greatly reduces the cold side temperature and thermal resistance, and obviously improves the output power. Compare with air natural convection cooling, the main thermal resistance changes from the resistance between the fins and the ambient to the thermal contact resistances between the generator and the heat sink at the conditions of forced convection and water cooling. This study may be guide the optimization of generator structure.     

转炉半导体温差发电系统结构设计及数值模拟

设计了一种回收工业转炉余热的半导体温差发电装置。针对转炉转动的特点，研究设计了风冷式的冷端结构。采用Fluent软件对温度分布及速度分布进行了数值模拟，并对计算结果进行了分析。结果表明，采用风扇顸部冲击冷却的形式可达到良好的效果，可使温差发电元件两端温差高达70℃，满足了半导体温差发电温差基本要求，该设计也满足自带风扇负载的要求。     

Global sensitivity analysis of two-stage thermoelectric refrigeration system based on response variance

In this paper, a mathematical model of two-stage thermoelectric refrigeration system is established considering the influence of external heat transfer and its performance is analysed based on finite-time thermodynamics and Newton's heat transfer law. Taking the cooling capacity and coefficient of performance of the two-stage thermoelectric refrigeration system as separate objective functions, the general relationship between cooling capacity, coefficient of performance, and working design parameters of the system is determined. The influence of the fluctuation of the input design parameters on the output performance parameters is studied using a global sensitivity analysis based on the variance response. The main and total Global sensitivity indices of input parameters that affect the output performance are calculated, and the related sensitivity ranking are obtained. The results can be used to guide the performance analysis and parameter optimization of two-stage thermoelectric refrigeration system in application.     

Development and testing of a domestic woodstove thermoelectric generator with natural convection cooling

A thermoelectric generator was fitted to the side of a domestic woodstove. The generator was driven using one or more thermoelectric modules designed to give significant power at a reasonable cost. The thermoelectric generator was air cooled by natural convection using a commercially available heat sink. Testing was undertaken under a controlled woodstove firing rate and temperatures, and open circuit voltages were monitored over extended periods. The maximum steady state matched load power was 4.2 W using a single module. The use of multiple modules with a single heat sink was found to reduce the total power output relative to the single module case as a result of reduced hot to cold surface temperature differences.     

A Finite Volume Analysis of Thermoelectric Generators

ABSTRACT

The electric power produced by a thermoelectric generator (TEG) is strongly influenced by the applied heat sink. While a TEG is aimed at harvesting waste heat, the optimization of the efficiency of the heat sink is a key task for the design of waste heat recovery systems implementing TEG. A TEG model is proposed and implemented in an open source toolbox for field operation and manipulation (OpenFOAM) for the purpose of performing optimizations of the heat sink, using a commercially available TEG as basis. This model includes the multi-physics thermoelectric coupled effects. Conservation principles of energy and current are considered simultaneously. This includes the thermal and electric conduction, Seebeck effect, Peltier effect, Thomson effect, and Joule heating. Particular attention is given to a proper modeling of the boundary conditions. The thermoelectric model is implemented in such a way that it can readily be combined with other physical models in OpenFOAM. The model is validated by comparing the predictions to analytical results, measurements as well as the simulation data of other authors.     

一种新型汽车尾气多通道热能发电系统

根据温差发电原理,设计了一种新型网格状通气管式的温差发电装置,实现对汽车尾气热能的再利用。通过优化温差发电装置的结构,改变了水箱结构,增加了废热通道数量,能够贴更多的温差发电片,从而提高转换效率。通过UG(计算机辅助设计软件)建立汽车尾气温差发电装置的理论模型,经过计算,当温差等于100℃时该装置的转换效率约等于5.67%。与其他温差发电装置进行比较,热油式温差发电器在260℃温差下最大热能转换效率可达4.389%,而汽车尾气温差发电器输出功率随着烟气温度的升高近似成线性递增,热能转换效率较低[1],通过比较得出,本装置不仅提高了转换效率,且达到相同转换效率时所对应的温差值也相应减少。     

Thermal‐hydraulic design features of a micronuclear reactor power source applied for multipurpose

Microheat pipe cooled reactor power source (HRP) designed for space or underwater vehicles meets the future demands, such as safer structure, longer operating time, and fewer mechanical moving parts. In this paper, potassium heat pipe cooled reactor power source system which generates 50 kWe electricity is proposed. The reactor core using uranium nitride fuel is cooled by 37 potassium high‐temperature heat pipes. The shields are designed as tungsten and water, and reactor reactivity is controlled by control drums. The thermoelectric generator (TEG) consists of thermoelectric conversion units and seawater cooler. The thermoelectric conversion units convert thermal energy to electric energy through the high‐performance thermoelectric material. A code applied for designing and analyzing the reactor power system is developed. It consists of multichannel reactor core model, heat pipe model using thermal resistance network, thermoelectric conversion, and thermal conductivity model. Then, the sensitivity analysis is performed on two key parameters including the length of the heat pipe condensation section and the cold junction temperature of the TE cell. Meanwhile, the steady‐state calculations are conducted. Results show that the maximum fuel temperature is 938 K located in the center of reactor core and the outlet temperature of coolant reaches 316 K. Both of them are within the limitation. It is concluded that the preliminary design of HPR design is reasonable and reliable. The designed residual heat removal system has sufficient safety margin to release the decay heat of the reactor. This research provides valuable analysis for the application of micronuclear power source.     

Experimental study on low-temperature waste heat thermoelectric generator

In order to further studies on thermoelectric generation, an experimental thermoelectric generator unit incorporating the commercially available thermoelectric modules with the parallel-plate heat exchanger has been constructed. The experiments are carried out to examine the influences of the main operating conditions, the hot and cold fluid inlet temperatures, flow rates and the load resistance, on the power output and conversion efficiency. The two operation parameters such as the hot fluid inlet temperature and flow rate are found to significantly affect the maximum power output and conversion efficiency. A comparison of the experimental results with those from the previously published numerical model is also presented. The meaningful results obtained here may serve as a good guide for further improving the numerical model and conducting a system level optimization study in the next step. Also, the present study shows the promising potential of using this kind of thermoelectric generator for low-temperature waste heat recovery.     

Thermoelectric generator sandwiched in a crossflow heat exchanger with optimal connectivity between modules

The design of a thermoelectric generator sandwiched in the wall of a crossflow heat exchanger was optimized. A numerical model has been developed and validated. The objective function was the total power output. The design variables were the number of modules and the current in each control volume of the mesh. We also optimize directly the electrical topology of the system. A genetic algorithm was used to perform the optimizations. Complex optimal electrical topologies were achieved due to the non-uniform temperatures distributions in the heat exchanger.