资源描述
Thermoelectric power generation, also called thermoelectric power generation, is a kind of green environmental protection.
The thermoelectric power generation technology has the advantages of simple structure, strong and durable, no moving parts, no noise, long service life, etc.. Can make reasonable use of solar energy, geothermal energy, industrial waste heat and low grade energy into electricity. The research of thermoelectric power generation technology began in 1940s. Because of its significant advantages, thermoelectric power generation in aviation, military and other fields has been widely used, the United States, former Soviet Union has developed a thousands of radioisotope or nuclear reactor temperature difference generator used as empty asked, marine equipment of power supply. With the increasing depletion of fossil energy, the United States, Japan, the European Union and other developed countries pay more attention to the research of thermoelectric power generation technology in the civil field, and has made considerable progress. Research in domestic thermal power generation, mainly in electrical theory and thermoelectric materials by research, aimed at temperature hair appliances optimization and provide theoretical guidance for the preparation of thermoelectric materials with excellent properties, although China is the world largest semiconductor thermoelectric device output country, but in the temperature difference hair appliances integrated design and application research is still very lack. Therefore, the study of thermoelectric power generation has a very realistic significance.
Is introduced in this paper principle of thermoelectric technology, reviews the research progress and status quo of domestic and foreign, to common commercial thermoelectric module as an example, the power generation efficiency of thermoelectric power generation in the presence of low, thermoelectricity component and short service life, reliability are analyzed, and countermeasures are put forward. With the improvement of the performance of thermoelectric materials and the increase of the reliability of thermoelectric components, the application of thermoelectric power generation has a broad prospect.
1 working principle
Complete the temperature difference, so that high temperature thermoelectric power is based on thermoelectric material Seebeck effect developed a power generation technology, the P type and N type two kind of different types of thermoelectric materials (P type hole rich materials, N type is electron rich material) is connected to the formation of a PN junction, is placed in a high temperature state, and the other end is formed at low temperature, due to the thermal excitation, p if there exists a locally connected) type material end hole (electron) concentration is higher than that of the low temperature end, so in this concentration gradient driven Bu, holes and electrons to the low temperature side diffusion, resulting in the formation of electric potential thermoelectric materials through the low temperature end of the high temperature end of the input of heat energy directly into electrical energy. A PN junction alone, electromotive force can be formed is very small, and if so many series of PN junctionCome, can get enough high voltage, become a thermoelectric power plant 2 domestic and international thermoelectric power generation technology research progress
2.1 research progress in foreign countries
Since the discovery of the Seebeck effect since 1821 Seebeck, foreign the thermoelectric generation of a large number of studies, in 1947, first the thermoelectric generator available, efficiency is only 1.5%. In 1953, Loffe academician research team successfully developed the use of coal oil lamps, tractor heat as a heat source of thermoelectric power plant, in the use of electricity difficult areas for small power supply. In the sixties of the 20th century, some materials with good thermoelectric properties, the research upsurge of thermoelectric power generation reached a peak, especially the former Soviet Union and the United States, due to the promotion of national defense, military and other special industry, application and development of thermoelectric generation technology rapidly. By the end of 1960s, the former Soviet Union has made more than 1000 radioactive isotope thermoelectric generator (RTG), which is widely used in satellite power supply, beacon and navigation mark, and its average service life is more than 10 years. The United States is also unwilling to lag behind, and its development of the longest RTG workQuestion has been over 30 years. June 1961 U.S. SNAP-3A energy systems put into use, the output power of 2.7 W, power generation efficiency of 5.1%. The RTG} output power, which was used on the launch of Jupiter and Saturn in 1977, has reached 155 W. In early 1980s, the United States completed the development of the 500-1 000 W military thermoelectric generator, and in the late 80's to enter the army equipment. With the energy crisis and environmental pollution, people began to pay attention to the value of thermoelectric power generation in waste heat utilization, many countries have developed thermoelectric technology as a medium and long-term energy development plan. Japan launched a series of to "solid waste combustion energy recovery research program" in the title of the government plan is studied for the solid waste incineration furnace waste heat power generation technology, combining the turbines and thermoelectric generator, to achieve maximum utilization of the heat of the different scale garbage incineration. 2003 November U. S. Department of Energy announced funded Pacific Northwest National Laboratory, Michigan Technology University and other units, focusing on their research in high performance thermoelectric materials and application technology, especially the use of industrial waste heat. In recent years, the utilization of the low grade heat source has become the main direction of the research on the technology of thermal power generation. Maneewan, such as the use of steel plate placed on the roof of the solar collector to absorb the heat and the environment of the temperature difference between power generation, to drive the axial flow wind}) L to guide the natural convection of the roof air, so as to cool the roof. Rida and so on, the thermal side of the thermoelectric generator is connected with the outer wall of the cooking stove in the country, and the cold end is arranged in the air, and the temperature of the furnace wall and the environment are used to generate electricity, and the output power is 4.2W. HASEBE et al. The summer high temperature surface as the heat source, heat exchange tube for the collector. By 19 groups of thermoelectric components. In the heat pipe liquid flow rate is 0.7 L / min, output power of 3.6 w thacher, funded by the U. S. Department of energy and New York State Energy Research and development authority in the development of vehicle exhaust waste heat power generation system, the use of the group of 20 hz-20 thermoelectric module, thermoelectric materials for Bi te based materials, vehicle speed of 112 km / h, maximum temperature difference 174 DEG C, maximum output power of 255 W, 2006, bsst scientists and BMW jointly announced, commercial vehicle temperature difference generator will be put into operation in 2013. Douglas and so on the dynamic change of the heat source, the design of multi module Interaction Loop thermoelectric generator, under the same heat source, the maximum output power increased by 25%.
2.2 domestic research progress
Domestic research on thermoelectric power generation is relatively late, and it is mainly focused on the research of the theory and the preparation of thermoelectric materials. Chen Jincan research group from 1980s began to study the basic theory of thermoelectric generator, the thermoelectric properties of the optimization and analysis, get a lot of meaningful results [no. Qu Jian et al. Li Yudong et al. Analysis of the performance of the low temperature difference generator from the point of view of exergy. Jia Lei et al. The influence of Thompson Ge on the output power of the low temperature and large temperature difference conditions can not be ignored. Jia Yang
Etc. a temperature thermoelectric coupling analysis model, to the numerical calculation method analysis the thermoelectric material parameters and their variation on electrical characteristics of, draw the conclusion, material thermal conductivity, electrical resistivity and Seebeck coefficient on the generator efficiency of conversion are nonlinear, which influence coefficient of thermal conductivity of the most obvious. De Peng, and analysis the thermoelectric thermal environment, loop load resistance parameters and thermoelectric monomers of connection ways of operating performance of the electric appliance, it is concluded that to improve thermoelectric generator at the hot end heat flux or increased cold end of the heat transfer coefficient can increase the electrical output power and the efficiency of thermoelectric conversion of conclusion. Su Jingfang studied the system.
And the environment, system and system of flux relation, properties of the system to make optimization based thermoelectric generator optimization design model, and using VB 6.0 (Microsoft Visual Basic 6.0) language as a development tool, ActiveX Data Object Access database, the preparation of the thermoelectric generator design software. Qian Weiqiang through study on the electrical properties of low grade heat source of small semiconductor temperature difference, summarizes the electromotive force and internal resistance and transmission power parameter changes with the external circuit, temperature, generating module geometry factors. We also study the series and parallel connection thermoelectric module performance. From the point of view of non-equilibrium thermodynamics, the model of the low temperature difference of the single layer and multiple electric appliances in the low temperature and low temperature stability was established. Study on thermoelectric generator in the internal structure and external for the movement of the thermal conditions Bu, combined with experiment, it is concluded that the best matching coefficients, power output and efficiency are with the maximum temperature difference approximate linearly, and points out the power generation efficiency is low in the root the rely on the improvement of the material properties. Just east of theoretical analysis and experimental study combined by simulating the tank vent tube near the area of refrigerating condition, by cooling condition evaluation of infrared stealth effect, it is concluded that to tank exhaust waste heat as the heat source will be the application of thermoelectric technology to the tanks, infrared stealth feasible conclusion.
3.1 generation efficiency
At present, the efficiency of thermoelectric power generation is generally 5%-7%, far less than 40% of thermal power generation. The main reason is that the performance of thermoelectric materials is not good, on the other hand is the matching of electrical appliances factory.
3.1.1 thermoelectric materials
Thermoelectric materials, as the core part of thermoelectric devices, directly determine the performance of the device. The optimal value of ZT is the most important parameter to measure the performance of thermoelectric materials. The higher the ZT value, the better the thermoelectric properties of the materials, the higher the energy conversion efficiency. Bi2T3; room temperature ZT value of about 1, is the most widely used thermoelectric materials. But the thermoelectric power generation efficiency of Bi2T3 materials is still less than 10%. If the ZT value of the material can be increased to about 3, the difference in temperature will be comparable to that of the conventional power generation. Therefore, people are actively looking for and development of high merit of new thermoelectric materials, the present research hotspots: cobalt based oxide thermoelectric materials, quasi crystal materials, superlattice thermoelectric materials, nano thermoelectric materials. Terasaki discovered for the first time NaCo2O4 single crystal at room temperature Bu has a higher Seebeck coefficient, low resistivity and low thermal conductivity, this caused people's attention, but NaCo2O4 in air deliquescent and more than 1 073 K volatile, so people look to another drill based oxides of Ca-Co-O system. The Funahashi study predicts: Ca2Co2O5 in T = 873 K, ZT=1.2 2.7. Quasi crystalline thermoelectric materials in 1984 by Shechtman and other first found that in recent years caused concern. This kind of material has good thermodynamic stability, high resistivity, and has a negative coefficient of thermal conductivity, so the conductive performance is good, and the thermal conductivity is low. A quasi crystalline thermoelectric material with ZT=1.6 at room temperature was predicted. The superlattice is a multi layer heterogeneous structure formed by the periodic alternating growth of two kinds of semiconductor single crystal films, and each layer contains several or even several layers. Due to the special structure and semiconductor super lattice electrons (or holes) energy will appear new quantization, resulting in the increase of the density of States and therefore superlattice material with many new features. Venkatasubramanian and other metal organic compounds
Gas phase deposition (MOCVE) method to prepare Bi-Te based alloy film, ZT value reached 2.4 300K. Dresselhaus of Bi nanowires and quantum well system after a large number of studies predicted that the quantum confinement effect can be obtained by superlattice ZT value of more than 3 of the material. Nano thermoelectric materials is another hot research topic in the field of thermoelectric materials, and the achievements are outstanding in the field of Zhejiang University. Zhao Xinbing and other research found that the traditional Bi-Te based thermoelectric materials to add 15% containing Bi2T3; nanotube powder, can make the thermoelectric properties of materials increased by about 20%. Cao, ZT=1.28 (Bi, Sb) 2Te3 were obtained by hydrothermal synthesis. ZHAO and so on through the nanometer powder doping, the ZT value is prepared to exceed 1.5 of the Bi2Te3-Sb2Te3 and GeTe-AgSbTe2 nano structure materials.
3.1.2 matching problem
Output power and power generation efficiency of thermoelectric generator and high temperature end temperature (Th). Low temperature (Tc), thermoelectric power generation circuit current (I), load resistance (R), electrical resistance (R) and other factors are closely related. Under different conditions, the difference of the performance of the thermoelectric generator is great. Qu Jian and other applications of finite
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