热电发电机驱动热电热泵联合循环热力学分析

建立了新型的热电发电机驱动热电热泵联合循环模型,基于非平衡热力学理论,对装置性能进行分析,导出了供热率、无量纲供热率和供热系数与热电单元比等参数的解析式,研究了该型装置最大供热率和最大供热系数对应的最优工作电流和最优热电单元分配,分析了发电机高温热源温度、热泵供热空间温度等对装置供热率、供热系数、最优工作电流和最优热电单元分配的影响,并给出了不同发电机热源温度下,供热系数与无量纲供热率的关系曲线.     

联合热电装置极限工作温差研究

基于非平衡热力学理论，对联合半导体热电装置循环模型的工作温差进行研究。分别针对热电发电机驱动热电制冷机和驱动热电热泵两类循环模型，给出了一定热源条件下，装置的极限工作温差同热电单元比的关系，并研究了极限工作温差随发电机高温热源温度的变化规律。     

热电制冷的热力学机理分析研究

把热电制冷的机理与一般相变制冷的机理作比较，分析热电制冷过程的热力学原理。由分析结果得知，在理想工作条件下，电流通过半导体材料进行制冷时，同时存在的帕尔帖效应、汤姆逊效应和傅立叶效应三种效应共同耦合作用的制冷效果可以分解为电子循环与两种不可逆效应的叠加。其中的作用力是二种材料的电子化学势，最大的影响因素是二种不可逆热效应。     

单级热电发电机有效功率性能分析和优化

在已有文献建立的单级多单元热电发电机模型基础上,运用有限时间热力学理论,研究热电发电机有效功率最优性能,推导出有效功率表达式.通过数值计算,比较最大有效功率和最大功率条件下,热电发电机的效率,分析热电单元数和高温热源温度对热电发电机有效功率性能的影响.结果表明,最大有效功率下的效率高于最大功率下的效率;热电单元数和高温...     

水冷式小空间热电制冷器结构设计与性能分析

基于一种不依赖模块规格型号和换热设备几何参数的热电制冷系统分析方法,建立了热电制冷装置有限时间热力学分析模型。针对水冷式小空间热电制冷器的基本结构,构建了一个由8个商用热电制冷片组成的小型热电制冷器,分析了工作电流、填充系数等对制冷性能的影响,与空冷式热电制冷器性能进行了比较,分析了传热条件对装置性能的影响,所得结果可为水冷式小空间热电制冷器的设计与运行提供参考。     

基于热管散热的串联式两级热电制冷器制冷性能综合分析

针对基于热管散热的串联式两级热电制冷器,建立了有限时间热力学模型。通过热阻分析的方法建立了热电制冷器的一维热阻网络图并给出了冷热端热阻的具体计算方法。以制冷率、制冷系数、热力学完善度和极限制冷温差为性能指标,用数值算例的方法研究了工作电流、热电单元分配比、热电单元横截面积、热电单元长度、热管几何参数(冷凝段长度和管芯厚度)和制冷温差等关键参数对热电制冷器综合性能的影响规律。     

两级热电热泵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泵模型，用有限时间热力学对牛顿传热规律下两级半导体热电热泵的性能进行分析，导出了供热率、供热系数与工作电流的一般关系式，得到了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。     

太阳能半导体热电装置尺寸的优化分析

以多P-N结构成的半导体热电装置为研究对象,通过对热电装置模型的简化,并考虑材料参数随温度变化的实际情况,建立了热电效率随尺寸变化的数学模型。分析得出了影响热电装置热电效率的尺寸参数,为优化分析确定了设计变量和状态变量,并使有限元优化分析得到了简化。借助ANSYS优化分析模块,计算出了热电装置的最优化尺寸方案。     

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。     

多级热电发电机特性分析与性能优化

基于非平衡热力学理论,建立多级热电发电机的数值分析模型,以数值算例分析其各级热电单元数相同时的基本输出特性,并在热电单元总数一定的约束下,分别以功率和效率为优化目标,优化热电单元在各级间的配置和工作电流。各级热电单元数相同时,一定工作电流下,由高温侧至低温侧,各级温差呈等差递增分布,功率和效率依次增大,分别存在两个最优工作电流对应最大功率和最大效率。当工作温差和Seebeck系数较小时,各级单元数相同可获得最大功率;当温差或Seebeck系数较大时,热电单元数由高温侧至低温侧依次增大且呈等差分布可获得最大功率;对热电发电机各级配置相等数目的热电单元可获得最大效率。     

Measurements of thermoelectric properties of a thermoelectric cooler

The effective thermoelectric parameters of a single stage cooler were measured as a function of temperature and compared with those of the n and p type materials from which the thermoelements were prepared. The performance of the cooler was calculated by a computerized iterative process using measured parameters and compared with experimentally determined characteristics. The influence of electrical contact resistance on the performance of the cooler is not negligible.     

Investigation of prototype thermoelectric domestic-ventilator

Applications of thermoelectrics had been enlarged from conventional single refrigeration or generation to waste heat recovery with tough energy consumption of the world. With improvement of living standard more and more domestic air-conditioners are used in Chinese families now. Percentage of power consumption of domestic air-conditioner caused by heat load of fresh air supply increased after SARS, which could be prevented efficiently with sufficient fresh air supply, broke out in China in 2003. A novel prototype thermoelectric domestic-ventilator with heat recovery of exhaust of air-conditioned room had been made in Hunan University thermoelectric lab. A thermoelectric heat exchanger and a flat-fin cross flow heat exchanger were integrated in this ventilator. This ventilator was investigated and its cooling (and heating) performance were evaluated in terms of the coefficient of performance, cooling and heating powers, and being handled temperature difference of fresh air. The coefficient of performance of this ventilator was found to be over 2.5 in the whole experiment. The optimal working parameters of this ventilator were studied in this paper. The potential improvements in performances and market prospects were also discussed in this work.     

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.     

Analytical model of parallel thermoelectric generator

The paper studied the performances of parallel thermoelectric generator (TEG) by theoretical analysis and experimental test. An analytical model of parallel TEG was developed by theoretical analysis and calculation, based on thermodynamics theory, semiconductor thermoelectric theory and law of conservation of energy. Approximate expressions of output power and current of parallel TEG were deduced by the analytical model. An experimental system was built to verify the model. The results indicate that only when all of the thermoelectric modules (TE modules) in the parallel TEG have the same inherent parameters and working conditions, the parallel properties of the TEG are the same as that of common DC power. The existence of contact resistance is just like the increase of the TE module’s internal resistance, which leads to the deceases of output power. The thermal contact resistance reduces the output power by reducing the temperature difference between the two sides of the thermocouples. The results derived from the model are basically consistent with the experimental results, the model is suitable for the performance researching and designing of parallel TEG.     

Technical efficiency of thermoelectric power plants

This paper analyses the technical efficiency of Portuguese thermoelectric power generating plants with a two-stage procedure. In the first stage, the plants' relative technical efficiency is estimated with DEA (data envelopment analysis) to establish which plants perform most efficiently. These plants could serve as peers to help improve performance of the least efficient plants. The paper ranks these plants according to their relative efficiency for the period 1996–2004. In a second stage, the Simar and Wilson [Simar, L., Wilson, P.W., 2007. Estimation and inference in two-stage, semi-parametric models of production processes. Journal of Econometrics 136, 1–34] bootstrapped procedure is adopted to estimate the efficiency drivers. Economic implications arising from the study are considered.     

High temperature solar thermoelectric generator

The performance of a sintered SiGe thermoelectric generator is assessed by computing power output per unit area and the efficiency of thermoelectric conversion. Previously developed high temperature solar energy absorbers were used. The power output and efficiency are considerably improved by using a water- or vapour-cooled heat sink in place of a radiative heat sink. The power density in the thermoelectric generator compares well with those in photovoltaic heterojunction cells using concentrated solar energy.     

Experimental evaluation of prototype thermoelectric domestic-refrigerators

A number of prototype thermoelectric refrigerators are investigated and their cooling performances evaluated in terms of the coefficient-of-performance, heat-pumping capacity and cooling-down rate. The coefficient-of-performance of a thermoelectric refrigerator is found to be around 0.3–0.5 for a typical operating temperature at 5 °C with ambient at 25 °C. The potential improvement in the cooling performance of a thermoelectric refrigerator is also investigated employing a realistic model, with experimental data obtained from this work. The results show that an increase in its COP is possible through improvements in module contact resistances, thermal interfaces and the effectiveness of heat exchangers.     

Fiber-based flexible thermoelectric power generator

Flexible thermoelectric power generators fabricated by evaporating thin films on flexible fiber substrates are demonstrated to be feasible candidates for waste heat recovery. An open circuit voltage of 19.6 μV K per thermocouple junction is measured for Ni–Ag thin films, and a maximum power of 2 nW for 7 couples at ΔT = 6.6 K is measured. Heat transfer analysis is used to project performance for several other material systems, with a predicted power output of 1 μW per couple for Bi₂Te₃/Sb₂Te₃-based fiber coatings with a hot junction temperature of 100 °C. Considering the performance of woven thermoelectric cloths or fiber composites, relevant properties and dimensions of individual thermoelectric fibers are optimized.     

Developments in semiconductor thermoelectric materials

A surge in interest in developing alternative renewable energy technologies has been observed in recent years. In particular, thermoelectrics has drawn attention because thermoelectric effects enable direct conversion between thermal and electrical energy, and provide power generation and refrigeration alternatives. During the past decade, the performance of thermoelectric materials has been considerably improved; however, many challenges continue to exist. Developing thermoelectric materials with superior performance means tailoring interconnected thermoelectric physical parameters-electrical conductivities, Seebeck coefficients, and thermal conductivities for a crystalline system. The objectives of this paper are to introduce the recent developments in semiconductor thermoelectric materials, and briefly summarize the applications of such materials.