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OBTAINING AND RESEARCHING OF THERMOELECTRIC SEMICONDUCTOR MATERIALS FOR HIGH-EFFICIENTING THERMOELECTRIC GENERATORS WITH AN INCREASED EFFICIENCY COEFFICIENT Nabiev M.B.1, Khomidzhonov Z.M.2, Latipova M.I.3, Abdullaev A.A.4, Ergashev K.R.5, Rakhimov M.F.6 Email: Nabiev17145@scientifictext.ru
'Nabiev Makhmud Bozorovich - Docent;
2Khomidzhonov Zukhriddin Mayrufjon ugli - Assistant;
3Latipova Mukhayyo Ibragimjanovna - Assistant;
4Abdullaev Abduvokhid Abdugappar ugli - Assistant; 5Ergashev Komiljon Ravshan ugli - Assistant;
6Rakhimov Mirkamol Farkhodjon ugli - Assistant, DEPARTMENT OF ELECTRIC POWER, FERGANA POLYTECHNIC INSTITUTE, FERGANA, REPUBLIC OF UZBEKISTAN
Abstract: the article provides general information about the development of the physics of thermoelectric phenomena, as well as thermoelectric materials of direct energy conversion with increased efficiency. The article discusses work to improve the efficiency of thermoelectric materials. The aim of our work is to study the effect of the concentration of dopants and the amount of loss on the change in thermoelectric properties of the Bi2Te3-Bi2Se3 base and doping. The choice of the method for the preparation, purification, alloying, and preparation of thermoelectric substrates Bi2Te3-Bi2Se3 for alloying and ensuring their reproducibility under the pressure of an inert gas is described. Keywords: thermoelectricity, thermoelectric material, generator, organic fuel, autonomous power source, semiconductor, coefficient, thermal energy, physical processes, temperature, physical characteristics, transformation.
ПОЛУЧЕНИЕ И ИССЛЕДОВАНИЕ ТЕРМОЭЛЕКТРИЧЕСКИХ ПОЛУПРОВОДНИКОВЫХ МАТЕРИАЛОВ ДЛЯ ВЫСОКОЭФФЕКТИВНЫХ ТЕРМОЭЛЕКТРИЧЕСКИХ ГЕНЕРАТОРОВ С ПОВЫШЕННЫМ КОЭФФИЦИЕНТОМ ЭФФЕКТИВНОСТИ Набиев М.Б.1, Хамиджонов З.М.2, Латипова М.И.3, Абдуллаев А.А.4, Эргашев К.Р.5, Рахимов М.Ф.6
'Набиев Махмуд Бозорович - кандидат технических наук, доцент;
2Хамиджонов Зухриддин Маьруфжон угли - ассистент;
3Латипова Мухайё Ибрагимжановна - ассистент;
4Абдуллаев Абдувохид Абдугаппар угли - ассистент;
5Эргашев Комилжон Равшан угли - ассистент;
6Рахимов Миркамол Фарходжон угли - ассистент, кафедра электроэнергетики, Ферганский политехнический институт, г. Фергана, Республика Узбекистан
Аннотация: в статье приведены общие сведения о развитии физики термоэлектрических явлений, а также термоэлектрические материалы прямого преобразования энергии с повышенным КПД. В статье рассматриваются работы по повышению эффективности термоэлектрических материалов. Целью нашей работы является исследование влияния концентрации легирующих добавок и количества
потерь на изменение термоэлектрических свойств основы Bi2Te3-Bi2Se3 и легирования. Описан выбор метода получения, очистки, легирования и получения термоэлектрических основ Bi2Te3-Bi2Se3 для легирования и обеспечения их воспроизводимосьти под давлением инертного газа.
Ключевые слова: термоэлектричество, термоэлектрический материал, генератор, органическое топливо, автономный источник энергии, полупроводник, коэффициент, тепловая энергия, физические процессы, температура, физические характеристики, преобразование.
UDC 621.315.6
Until the XXI century, about 60 years ago, the research work of talented scientists led by A.F. Ioffe thermoelectricity triggered to the start of research in the United States, England and France. The development of work in the field of physics of thermoelectric phenomena, construction of thermo elements, synthesis of thermoelectric materials, elaboration and calculation methodically has led to the fact that various types of thermoelectric generators and purposes have already been created, using the heat of radioisotope sources and nuclear reactors, the heat of organic fuels, the sun and exhaust gases of various engines [1]. Currently, thermoelectric generators with power from several watts to several kilowatts are designing, manufacturing and operating as autonomous power sources.
These thermoelectric generators are designed for "small energy" and poses high reliability, ease of operation, durability, as well as high specific energy-weight characteristics. They are using for power supply to facilities remote from power lines, as well as in conditions where only thermoelectric generators can be the only ones possible.[3]
Thermoelectric semiconductor materials for direct energy conversion. The efficiency of thermoelectric generators are still low (2-7%), for this purpose semiconductor thermoelectric materials are used, in which provide the highest coefficient of conversion from heat to electricity. The list of substances having thermoelectric properties are quite large (thousands of alloys and compounds), but only a few of them can be used to convert thermal energy [8]. Modern science is constantly looking for new semiconductor compositions and progress in this area is provided not as much by theory as by practice, due to the complexity of the physical processes that occur in thermoelectric materials.
For practical use in thermal electric generators may be suitable thermoelectric materials capable to convert heat into electricity with an efficiency higher than 0.1% at a temperature difference between hot and cold junctions of thermo elements of the order of 200 - 300 0 С. The best of modern thermoelectric materials allow to obtain efficiency up to 10% with a temperature difference of 500-600 0 C, and a combination of several such materials (layered thermocouples) makes it possible to increase the efficiency up to 20% or more, with a temperature difference of 800 - 1000 0 С. Figure 1 shows the dependence of the efficiency hot junction temperature for some materials. [8]
/ .7 -PbTt
B-tiizTBj
- \ >
\ A / - /jrpmn
i / / /
yy it-i^S-p/
-1-1-
0 XH US iSJii' STO fmrrfG
Fig. 1. Dependency by efficiency thermoelectric material from the temperature of the hot junction
(cold junction temperature 27 0C) [1]
The efficiency of a thermoelectric material depends mainly on its physical characteristics, such as thermoelectric power, electrical conductivity and thermal conductivity [5].
To obtain the maximum figure of merit, it is necessary to minimize the thermal conductivity of the material. A.F. Ioffe proposed to use a system of solid solutions and alloys of various materials to reduce thermal conductivity [1, 2].
The quality factor of thermoelectric material was introduced by A.F.Ioffe as the most universal and complete for evaluating the cost-effectiveness of all types of thermoelectric power plants. The thermoelectric figure of merit Z of a material is determined by a combination of the above characteristics (thermoelectric power (a), electrical conductivity (g) and thermal conductivity (x))
Z = — (1)
x
In addition to these physical characteristics, the practical use of a thermoelectric material substantially depends on a number of technological criteria. This includes the mechanical properties of the material and its ability to withstand repeated heating and cooling. An important condition is the absence of irreversible physicochemical reactions and transformations in the material, which most often occur in the temperature range close to the melting point. Therefore, the temperature of the hot junction of the thermocouple is chosen significantly lower than the melting temperature of the metal [1].
Based on the foregoing, the article discusses the work on improving the efficiency of thermoelectric materials conducted by the author of the article in the direction of producing thermoelectric alloys and ingots for creating thermoelectric generators. The study and study of thermoelectric materials for the production of alloy bases and alloys in some cases makes it possible to expand the interval of their working temperatures and increase the quality factor Z, the efficiency of thermoelectric generators. [4]
A number of well-known classical works on the manufacture of thermo element branches are approved as follows. Purified, synthesized and doped thermoelectric material is used in the branches of thermocouples. There are several methods for manufacturing semiconductor briquettes for thermoelectric generators. The main varieties of these methods are the Chochralski method, the ampoule method, the Bridgman method, and various variations of zone melting methods [2].
We have chosen a method for producing thermoelectric materials in quartz crucibles under inert gas pressure (argon). The aim of our work is to study the influence on the concentration of the dopant and the amount of loss on the change in the thermoelectric properties of the base and doping of Bi2Te3-Bi2Se3. The composition of the solid solution
corresponding to 80 mol% was chosen as the basis. Bi2Te3 and 20 mol% Bi2Se3. Semielements were made from the obtained alloys by powder metallurgy.
In order to obtain highly effective thermoelectric materials, it is necessary to obtain bases, i.e., undoped material with optimal properties [6]. The resulting base for alloying should correspond to a = 2 00 h- 600 0hm" 1 ■ Sim" 1 a = 20 Oh- 2 40—.
deg
The basics were obtained by introducing into the mixture superstoichiometric chalcogen (tellurium, selenium, sulfur). The degree of exposure to chalcogen is found to decrease with increasing serial number in the periodic table. The base suitable for alloying has the properties a = 2 00 ^V/deg. , a = 600 0hm" 1 ■ sim" 1. The concentration of TeJ2 dopant added varies from 0.02% by weight to 0.12% by weight.
The optimal thermoelectric properties of alloys for thermoelectric generators are obtained by introducing 0.08 wt.% TeJ2 into the charge of the indicated composition. The properties of the semi-elements obtained from such ingots are as follows: a = 1 000 o hm " 1 ■ cm" 1, a = 1 5 0 ^V / deg.[3]
The research results are shown in Figure 2
s.
Ohm1, Sim1, k = £
1600 1400 1200 1000 800 600 400 200
0.02 0.04 0.06 0.08 0.1 012
_IeJ2, n %
Fig. 2. Studies of the influence of the concentration of the dopant and the amount of loss on the change in the thermoelectric properties of the base Bi2Te3-Bi2Se3
The average integral value of the quality factor of the material lies in the temperature range from 200С to 3000С (Z=1,5^0-3 deg-1).
Список литературы /References
1. Ioffe A.F. Poluprovodnikovyye termoelementy. M.-L., Izdatel'stvo RAN, 1956. S. 13-41.
2. Usmonov Y.A., Nabiyev M., Akhmedov T., Nabiyeva N., Yuldasheva I.I. // Aktual'nyye voprosy vysshego professional'nogo obrazovaniya, sbornik nauchnykh trudov Mezhdunarodnoy nauchno-metodicheskoy konferentsii, Ufa, Izdatel'stvo UGNTU, 2017. S. 108-112.
jiV
3. Kasimakhunova A.M., Olimov Sh.A., Mamadalieva L.K., Norbutaev М. // Photo Thermal Generator of Selective Radiation Structural and Energetic Features. Journal of Applied Mathematics and Physics. Scientific Research Publishing, 2019. 6.27. Volume 7. № 06. S. 126.
4. Rahimov Mirkamol, Xamidjonov Zuriddin //Увеличение эффективности турбогенераторов теплового электрического центра // Journal of Technical sciences. № 3, 2019. S. 10-13.
5. Zhabborov T.K., Nasretdinova F.N., Boynazarov B.B., Ergashev K.R., Elektricheskiye tsepi, soderzhashchiye nelineynyye elementy i metody ikh raschota.// Vestnik nauki i obrazovaniya. № 19 (73). Chast' 2, 2019. S. 10-12.
6. Eraliyev A.Kh., Hamidjonov Z.M., Rakhimov M.F., Abdullaev A.A. // Increasing efficiency of turbo generators in heat electric centers // European Science, 2019. № 6 (48). S. 36-40.
7. Zhabborov T.K., Nasretdinova F.N., Nazirzhonova SH.S., Khomidzhonov Z.M., Rakhimov M.F., Boynazarov B.B. // Ispol'zovanie sistemy askue dlya povysheniya Enepgeticheskoy effektivnosti ppotsessov analiza potpebleniya elektpoenepgii // Vestnik nauki i obrazovaniya, 2019. № 19 (73). Chast' 2.
ENERGY SAVING THROUGH THE USE OF ALTERNATIVE
ENERGY SOURCES Norkhojaeva N.N.1, Sobirov M.N.2 Email: Norkhoj aeva17@scientifictext.ru
1Norkhojaeva Nargiza Nosirovna - Senior Teacher; 2Sobirov Murodiljohn Nusrotillo o 'g 'li - Teacher, ELECTRIC ENGINEERING, ELECTRIC MECHANICS AND ELECTRIC TECHNOLOGIES DEPARTMENT, POWER ENGINEERING FACULTY, FERGHANA POLYTECHNIC INSTITUTE, FERGHANA, REPUBLIC OF UZBEKISTAN
Abstract: the article under discussion discusses energy saving through the use of alternative energy sources. The authors of the article consider that in today's world, the condition for the preservation and development of civilization on Earth has become the provision of mankind with sufficient fuel and energy. Limited reserves of traditionally fuel and energy resources made us turn to energy saving as one of the main elements of the modern concept of global energy development. Energy saving means rational use of energy at all levels of energy transformation - from primary energy production to consumption of all types of energy by end users. Energy saving measures can be different. One of the most effective ways to increase the efficiency of energy use - In the modern world, the condition for the preservation and development of civilization on Earth has become the provision of mankind with a sufficient amount of fuel and energy. Technologies of energy saving not only give considerable reduction of expenses on power expenses, but also have obvious ecological pluses.
Keywords: alternative, energy saving, use, energy, technology, application, modern, method, efficiency, resources, user, fuel, energy.
