微小型热电发电器建模及优化设计研究

微小型热电发电器由于尺寸较小,接触内阻以及结构的覆盖层、导流层等对输出功率和热电转换效率都有不可忽视的影响。结合上述因素,并考虑到汤姆孙效应,建立了微小型热电发电器输出功率和效率的数学计算模型。并以最大功率或者最大质量(体积)比功率为目标函数,对最大功率时的负载电阻、电偶臂对数和电偶臂长度等性能参数进行了优化分析,得到了相应的计算公式,为进一步的设计提出了理论指导,并通过实验进行了性能分析验证。最后分析了微小型热电发电器新的加工工艺和发展动向。     

ZT值温度依存性对温差发电器热电性能的影响

为了评估热电材料ZT值温度依存性对热电发电器性能的影响,基于HZ-20商用热电材料的热物性参数,分别采用定物性与变物性的计算方法,对温差发电器在具有不同热源温度下的工作性能进行理论研究。研究结果表明,当采用定物性方法计算时(即不考虑ZT值温度依存性),输出功率及相应转换效率的计算值都较采用变物性计算时存在一定的偏差。当半导体热端温度低于定物性计算时采用的定性温度值时,偏差很小,但随着半导体热端温度的继续增加,偏差则越来越大,高热端温度下计算得到的计算偏差达30%左右。因此,热电材料ZT值温度依存性对温差发电器热电性能的影响不容忽视。     

前景广阔的热电材料

热电材料是一种利用固体内部载流子运动实现热能和电能直接相互转换的功能材料.人们对热电材料的认识具有悠久的历史.     

21世纪的发电器

２１世纪的发电器傅黎燃料电池是２１世纪的一种重要发电器，其中以陶瓷或氧化固体燃料电池最有希望成为高效、低污染的发电装置。为此，澳大利亚五个主要财团建立了陶瓷燃料电池公司。陶瓷燃料电池是一种电化学器件，它直接把燃料，如气化煤、天然气转化为电，且不受势力...     

基于余热回收的半导体温差发电模型及数值模拟

本文提出一种改进的半导体温差发电模型,在温差发电器热端加上矩形格栅,并将这种格栅近似看作黑体,同时进一步运用FLUENT软件对该半导体温差发电系统的流场、温度场进行了数值仿真计算,并对仿真结果进行分析。结果表明该模型确实能够提高温差发电器的热端温度、冷端与热端的温差,使大量余热得到有效的利用;冷热端的温差比无格栅时提高了49.33%。模拟结果还表明格栅的几何尺寸选取对温差发电器热端的温度及冷热端温差有一定的影响。     

温差发电器应用于火力发电厂的分析

火力发电厂用锅炉吸收热能发电,而锅炉这一特殊结构部件既可以为热电效应为基础的温差发电器提供热源,也可以为其提供冷源,这为温差发电器应用于火力发电厂创造了条件。本文对应用温差发电器的可能性以及应用后火力发电厂的效率进行了分析,结论是可以提高火力发电厂效率,提出了锅炉各个温度区域如何应用热电器件的方法,并对在锅炉中应用温差发电器应该考虑的问题进行了分析。     

深空探测用斯特林发电器的发展

自由活塞斯特林循环动态发电技术具有效率高、寿命长、结构紧凑等诸多特点,目前受到深空探测电源系统的高度重视。随着影响发电器性能的各种关键技术逐步得到解决,斯特林发电器各方面性能已经有了很大提高,航天大国已经此项技术列为应用计划。主要介绍了国外空间斯特林发电器的发展历程、关键技术,为国内开展这方面工作提供有益参考。     

车用内置式温差发电器换热性能的数值模拟

本文针对提出的一种内置高强度温差发电器的结构,采用FLUENT软件对其对流换热系数、速度模量、径向速度进行分析,并和平板式温差发电器进行对比.结果表明提出的新结构在壁面换热方面优于平板式温差发电器,在节能应用中有很大潜力.     

电站锅炉炉膛中温差发电器的应用

对锅炉炉膛应用温差发电器后火力发电厂的效率进行了分析，结论是可以提高火力发电厂效率；对其应用结构进行了设计，并对锅炉炉膛中应用温差发电器应该考虑的一些问题进行了分析和讨论。     

具有PCM的汽车尾气温差发电器的变工况模拟

以内燃机为动力的汽车尾气余热具有高度瞬变特性,而温差发电器(termoelectric generator,TEG)往往对温度的变化较为敏感,针对这一矛盾,在尾气管道和热电模块之间添加相变材料层以减缓尾气温度波动对热电模块性能的影响。通过模拟计算的方法,比较了变工况条件下,相变材料层的添加对热电模块热端平均温度、输出电压等因素的影响。结果表明,相变材料(phase change materia,PCM)的添加对热电模块热端温度波动起到了良好的缓冲作用,大大提高了TEG输出电压的稳定性。     

Assessment of geothermal energy use with thermoelectric generator for hydrogen production

In this work, a new model for producing hydrogen from a low enthalpy geothermal source was presented. Thermal energy from geothermal sources can be converted into electric power by using thermoelectric modules instead of Organic Rankine Cycle (ORC) machines, especially for low geothermal temperatures. This electrical energy uses the water electrolysis process to produce hydrogen. Simulation and experiments for the thermoelectric module in this system were undertaken to assess the efficiency of these models. TRNSYS software is used to simulate the system in Hammam Righa spa, the temperature of this spring is 70 °C. Obtained results reveal that in hammam righa spa in Algeria, 0.5652 Kg hydrogen per square meter of thermoelectric generator (TEG) can be produced in one year.     

An effective Seebeck coefficient obtained by experimental results of a thermoelectric generator module

This article proposes a concept of “effective Seebeck coefficient”, which discusses the inconsistency between the theoretical Seebeck coefficient and the measured one. The inconsistency can be explained via contact effect and thermal resistor network. Two different clamping forces are applied to the TEG module to observe the contact effect. Throughout the experiments, the electric resistance seems insensitive to the clamping force; somehow the thermal contact effect dominates the TEG module performance. In addition, a thermal resistor network, which is used to calculate the exact temperature difference traverse the TE ingot, has been constructed. After applying a suitable clamping pressure and modifying the actual ΔT with thermal resistor network, the “effective Seebeck coefficient” has been proposed. Notably, this proposed value is very helpful for better understanding characteristics of the behavior of the TEG module operating in the actual conditions we provided, and it can be used to predict the performance of the TEG module under any other condition.     

Effect of irreversibilities on the performance of a thermoelectric generator

Using an externally and internally irreversible heat engine model, the maximum power and thermal efficiency at maximum power output have been determined for a thermoelectric generator. The irreversibilities can be characterized by a single parameter named the device-design parameter. The efficiency and power decrease with an increase of the device-design parameter which appears in the equations for maximum power and efficiency.     

Design of a thermoelectric generator with fast transient response

Thermoelectric modules are currently used both in Peltier cooling and in Seebeck mode for electricity generation. The developments experienced in both cases depend essentially on two factors: the thermoelectric properties of the materials that form these elements (mainly semiconductors), and the external structure of the semiconductors. Figure of Merit Z is currently the best way of measuring the efficiency of semiconductors, as it relates to the intrinsic parameters of the semiconductor: Seebeck coefficient, thermal resistance, and thermal conductivity. When it comes to evaluating the complete structure, the Coefficient of Performance (COP) is used, relating the electrical power to the thermal power of the module. This paper develops a Thermoelectric Generator (TEG) structure which allows minimising the response time of the thermoelectric device, obtaining short working cycles and, therefore, a higher working frequency.     

Investigation on a mini-CPC hybrid solar thermoelectric generator unit

A hybrid solar hot water and Bi₂Te₃-based thermoelectric generator (TEG) unit using a heat pipe evacuated tube collector with mini-compound parabolic concentrator (mini-CPC) is proposed. In this unit, the heat from the heat pipe evacuated tube solar collector is transferred to the hot side of TEG. Simultaneously, water cooling is used at the cold side to maintain the temperature difference. Electricity is generated by TEG and the remaining heat is transferred to water at the same time. This paper investigates how to convert excess solar heat into electricity more effectively. A mathematical model regarding this unit is developed and validated. It is found that the mini-CPC can significantly improve the electrical efficiency. The optimal thermal conductance of TEG is determined, which could make the best use of excess solar heat. The excess solar heat can be effectively converted into electricity when ZT of Bi₂Te₃ can be improved from 100 °C to 200 °C. Using TEG with ZT = 1.0 and a geometrical concentrating ratio at 0.92, electrical and thermal efficiencies of this system are predicted to be 3.3% and 48.6% when solar radiation and water temperature are 800 Wm⁻² and 20 °C, respectively.     

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.     

Experimental and analytical study on thermoelectric self cooling of devices

This paper presents and studies the novel concept of thermoelectric self cooling, which can be introduced as the cooling and temperature control of a device using thermoelectric technology without electricity consumption.For this study, it is designed a device endowed with an internal heat source. Subsequently, a commonly used cooling system is attached to the device and the thermal performance is statistically assessed. Afterwards, it is developed and studied a thermoelectric self cooling system appropriate for the device.Experimental and analytical results show that the thermal resistance between the heat source and the environment reduced by 25-30% when the thermoelectric self cooling system is installed, and indicates the promising applicability of this technology to devices that generate large amounts of heat, such as electrical power converters, transformers and control systems. Likewise, it was statistically proved that the thermoelectric self cooling system leads to significant reductions in the temperature difference between the heat source and the environment, and, what is more, this reduction increases as the heat flow generated by the heat source increases, which makes evident the fact that thermoelectric self cooling systems work as temperature controllers.     

Flexible thermoelectric generator for ambient assisted living wearable biometric sensors

In this work we proposed design, fabrication and functional characterization of a very low cost energy autonomous, maintenance free, flexible and wearable micro thermoelectric generator (μTEG), finalized to power very low consumption electronics ambient assisted living (AAL) applications. The prototype, integrating an array of 100 thin films thermocouples of Sb₂Te₃ and Bi₂Te₃, generates, at 40 °C, an open circuit output voltage of 430 mV and an electrical output power up to 32 nW with matched load. In real operation conditions of prototype, which are believed to be very close to a thermal gradient of 15 °C, the device generates an open circuit output voltage of about 160 mV, with an electrical output power up to 4.18 nW.In the first part of work, deposition investigation Sb₂Te₃ and Bi₂Te₃ thin films alloys on Kapton HN polyimide foil by RF magnetron co-sputtering technique is discussed. Deposition parameters have been optimized to gain perfect stoichiometric ratio and high thermoelectric power factor; fabricated thermogenerator has been tested at low gradient conditioned to evaluate applications like human skin wearable power generator for ambient assisted living applications.     

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.     

Development of a powerful miniature hydrogen catalytic combustion powered thermoelectric generator

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 H₂PtCl₆ 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.