CC BY
29SCIENTIFIC PROGRESS VOLUME 2 I ISSUE 6 I 2021 _ISSN: 2181-1601
THERMOELECTRIC GENERATOR FOR RURAL CONDITIONS
A. M. Kasimaxunova Maxsudjon Norbutaev Madinaxon Baratova
Fergana Polytechnic Institute
ABSTRACT
V state izlojeny rezultaty issledovaniya elektrophysicheskix parametersrov i proektirovanie termoelektricheskix generatorov, rasshirenie ego primeneniya s tselyu resheniya problemy ne dostatochnosti energii. Dana recommendation for energy supply of rural population thermoelectric generators, manufactured from materials Bi Te Sb (p -type) and Bi Te Se ( n -type).
Keywords: energy, preobrazovanie, elektrosnabjenie, semiconductor, termoelektricheskaya dobrotnost, technology, furnace, goryachie spai, kholodntie spai, elektroprovodimost, teploprovodnost.
INTRODUCTION
In recent years, the spiritual and physical obsolescence of power transmission lines, which were produced and put into operation half a century ago, has greatly exacerbated the duration of power outages in households living in rural areas in the short term. It is well known that this situation has led to growing public discontent, a sharp deterioration in people's lives, the population being left with the necessary work to be done from evening till midnight, and the level of education of students and schoolchildren due to unprepared classes.
This problem needs to be resolved without delay. Therefore, the issue of using alternative energy, which can be used successfully enough in small energy and is suitable for rural conditions, is becoming a very interesting factor. Of course, it is known that mini solar photovoltaic stations have been recommended and tested in practice by most scientists [1,2]. But this energy is advantageous in that its sources can only be used in the light of light. In addition, they are not yet competitive with alternative energy sources that can generate some electricity in terms of their economic performance [3,4].
In this regard, it is advisable to use thermoelectric generators (TEG) that can convert heat energy directly into electrical energy [6,7]. Research on thermoelectric generators is not extensive in our country. Otherwise, it was natural that it would have been applied to so many industries to this day, and put into mass production. TEGs are also made of materials with semiconducting properties [8,9.], Which are important for their p- and n-conductivity properties. In this paper, information about TEgs created by studying the electrophysical properties of thermoelectric generators by the same authors
is given, without dwelling on the scientific information known to the researchers. Their application has been shown to positively address part of an acute problem in rural life.
EXAMINATION OF THE MATERIAL OF THERMOGENERATORS AND THEIR ELECTROPHYSICAL PARAMETERS
In order to make the planned thermoelectric generator, three compound thermoelectric materials were obtained: BiTeSb (p-type) and BiTeSe (n-type). Its extraction technology was implemented as [ 8 ]. [ 1 and 6 ] to be known, tags out power p and n-type conductivity due to the size of the twigs with a geometric design of the battery after the process of preparation of this material in the selection of technological data, measurement and control works. In the control, the thermoelectric driving coefficient a, the electrical conductivity s, and the thermal conductivity ch were measured.
The main parameter of the collected thermocouples was controlled by thermoelectric efficiency Z Harman method. This method is better than other methods, taking into account the thermal conductivity of the conductors. In the Harman method, the temperature gradient between the welded ends of the battery (i.e., the cold and hot ends) is created using the Pelte effect. When current flows through one end of a battery attached to a copper base, one end of it heats up and the other end cools down. The current absorbed or released as a result of the Pelte effect depends on the first level of the thermal current:
Q = nJ = aTJ ( 1)
This method allows you to measure all thermoelectric parameters
a, a, [j., Z Ba x at the same time [2].
To measure the Z termostabillashtirilgan into the camera installed copper base vacuum [10].The battery under study is placed on a copper base in vacuum. Welding the battery to the base, through heat-conducting ceramics, allows for good thermal contact. Carrying out the measurements in a vacuum prevents the effects that the experimental results show due to the interaction of the thermocouple side surfaces with the environment. All conductors and thermocouples (thermocouples made of chrome-aluminum) are removed from the chamber to the measuring instruments. The temperature of the hot and cold ends, the current flowing through the thermocouples, the voltage drop, and the thermo e.yu.k. Measured using an electronic digital voltmeter of type ^ 68,000.
During the measurements, a direct current from the Baken battery (additional power source!) Was passed through a thermal battery. Once equilibrium was maintained, the temperature difference at the ends of the battery was determined. The U = JR + aAT voltage drop across the battery was measured during current transfer.
Thermo e.yu.k. to determine the value, the current was stopped for a short time (~ 5 sec) and Ua = aAT the value of was recorded.
The formula for calculating the efficiency of batteries has been determined. To do this, write the equation for the heat equilibrium in a single circuit (for example, T s is the temperature at the cold end) :
S 1 n
Qx = x~s*T + -2J2R-aTJ = 0.
(2)
Here
X = (Xn + Xp)NK
(3)
where is the number of pairs of thermocouples in the thermocouple, J is the
current density, R is the internal resistance of the battery, AT is the temperature
difference at the hot and cold ends. The electrical resistance of batteries was determined
by the specific resistances of the materials in them, using the following formula:
i
R = (Pn + Pp)-NyK
Similarly,
a
= (\an\ +
\ap\)K
Battery voltage drop:
Battery efficiency:
U = JR + aAT, ôyHgaH a = , hence (6)
U-JR AT
(4)
(5)
(6)
(7)
where the average values
So,
From formula ( 2 ) we obtain:
a' = \an\ + \ap\ 1 _ 1 1 a' an ap
X Xn + Xp
Z =
N2a'2a'\ _ a2
N2x'f = RXj
S aTx]-\R]2
X- = -2—
A I AT
(8)
(9)
Substituting ( 9 ) into ( 8 ), we obtain:
x
z = -JR-)- (10)
JR'X ' ypT
here
Tr-Tx
1 =
1YPT 2 '
The latter expression is the basic formula for calculating Z in the Harman method. To obtain more accurate results, the measurements are repeated several times, then the results obtained are compared and the average value is calculated:
ZYPT = lm (11)
where m is the number of measurements.
It is important to note that during the measurements, when there was no current in the battery (at equilibrium temperatures), an unnecessary temperature gradient was observed across the sample. The temperature difference between the hot and cold ends is caused by the one-sided welding of the battery to the cooled copper base. Determining the value of the unnecessary temperature gradient at different temperatures of the refrigerator AT', a coefficient was taken into account that took it into account in the calculation. For example, thermo e.yu.k. The following formula was used to calculate:
a = \ (12)
(AT-^)-N v '
where ^ - AT' is the correction (coefficient).
To determine the electrical resistance Rmax of a material, an alternating current is passed through it. In our case, such measurements were made on each of its branches before combining the eight thermocouples into a single battery. Then, by adding these values, the total resistance of the battery was determined. Measurements were made using a millimeter measuring instrument.
R=(Pn + Pp)sN = P*Ns
here
RS
P =TN
Table J shows the values of the main parameters measured in the Harman method.
Table TEG parameters research results
Tg ( O S) Tx ( O S) a ( mkV / grad) X ( MW / cm.K ) U = ocDADT ( mV ) P ( Om.sm ) I (A) SHE IS ( mV ) R ( mOm ) Z tag 10 -3 grad -1
15.0 4.2 448.01 42.44 35.0 2.01 0.41 92.01 147.1 2.28
16.2 4.2 432.01 41.25 32.01 2.10 0.384 88.9 147.3 2.24
16.2 4.5 435.03 42.21 31.31 2,085 0.38 87.5 146 2.08
16.6 4.6 407.02 35.89 32.11 2,125 0.38 89.5 149 2.2
16.6 4.65 407.01 37.4 32.11 2,087 0.379 89.5 146 2.22
25.0 17.8 488.03 24.96 19.01 2.41 0.160 45.4 168 2.63
25.0 17.3 471.02 51.61 19.81 2.38 0.159 45.8 166.4 2.76
25.0 17.9 487.01 24.83 19.12 2.28 0.161 44.1 161 2.78
25.0 16.9 502.01 29.83 24.11 2.21 0.205 54.9 154.4 2.61
25.0 16.0 467.3 26.52 24.33 2.21 0.203 57.01 154.6 2.73
25.0 14.05 443.04 29.71 32.82 2.06 0.33 80.2 143.4 2.51
25.0 14.0 446.03 31.78 33.89 1.98 0.35 82.8 139.4 2.51
25.0 13.0 447.6 30.78 37.61 2,185 0.379 96.01 153.1 2.34
25.0 12.0 440.2 30.84 40.52 2,025 0.42 100.01 141.5 2.50
25.0 9.6 431.4 31.0 45.40 2.03 0.49 115.3 141.6 2.44
25.0 9.3 429.01 31.45 46.42 2.2 0.49 124.01 155 2.27
25.0 8.5 440 31,14 50.02 2.20 0.5 126.7 154.3 2.47
Note: These measurements were made at room temperature.
Technology of connecting TEG to a heat source
The prepared thermoelectric generator consists of a total of 6 4 thermocouples, the geometric dimensions of which are as follows: p - and n - branches are equilateral 4
x 4 mm along the cross sections, height 14 mm. The thermocouples are connected in parallel and in series so that the output voltage is 12 V , and the power corresponds to the loading current to which it is connected. When the temperature difference between the hot and cold ends of the TEG is AT =110 o C, the electric power is 25 W. The battery (1 ) cost-saving of 15 to 12 and 3 W li can provide electric power to the lights. It should be noted that it is possible to change the voltage
and current values of 24 V by changing the wiring diagrams of such generators.
The finished thermocouple is welded to a material with good thermal conductivity but insulating properties in terms of electrical conductivity, and then fastened to the furnace shell using bolts. The large size of the plate surface allows the heat from the oven surface to be less, or more concentrated.
Figure 1. Connect the TEG to the round shaped oven.
However, in any case, the plate surface must be larger than the surface of the TEG hot ends. This situation makes room for the fastening bolts. Thermoelectric generators of this design can be attached to the furnace structure of any shape by simple installation work (Fig. 2).
Figure 2. Connecting a TEG to a rectangular TEG.
CONCLUSION
Based on the work done and their results, it is possible to draw the following conclusions. Thermoelectric generators are one of the most important alternative energy sources today, and it is important to implement them in our country. Because using them to get electricity from a heat source is not a problem. In winter, about 50% of the population likes wood, coal, and even tappi (dung). The heat generated by them easily creates the temperature difference required for the TEGs, forming them along the branches. The battery can provide optimal operating mode if it is made of low temperature materials. In addition, it has mechanical strength. Long service life. It is convenient to adjust the geometric dimensions to the surface of the oven. It can also be
SCIENTIFIC PROGRESS VOLUME 2 I ISSUE 6 I 2021 _ISSN: 2181-1601
removed and transported when needed. It can be attached to the stove mainly in winter and can also be used as a charging source in summer.
REFERENCES
[1].A.V.Vasilev, A.P.Landsman, Semiconductor fotopreobrazovateli. Izd-vo Sovetskoe radio, Moscow, 1975. 248 p.
[2]. N. Kolodinskaya, Solnechnaya energetika v Rossii i v mire. RB. RU. Longrid y, November 25, 2020y.
[3]. S.S.Dasheev, E.A.Mal y shev. Solnechnaya energetika: sostoyanie i perspektivy, Vestnik nauki i obrazovaniya, Chast 1, 2018g.
[4]. AMKasimakhunova, Sh.A.Olimov, R.Nurdinova, Tahir Iqbal, LKMamadalieva, Highly Efficient Conversion of Solar Energy by the Photoelectric Converter and a Thermoelectric Converter, Journal of Applied Mathematics and Physics, 2018, 6,1-10. http : // www . scirp . org / journal / jamp USA.
[5].A.V.Kvitko, G.S.Otmaxov. Perspectives and features of operation of solar power plants. Bulletin of Science and Education, 2017 Chast 3.
[6]. A.F.Ioffe. Energeticheskie osnovy thermoelektricheskix batteries from semiconductors. Izd-vo An USSR, M.-L. 1950
[7]. Bulat LP, Osvensky VB, Pivovarov GI, Snarskii AA, Tatyanin EV, Tay AA // Proc. 6th European Conference on Thermoelectrics, July 2 - 4, 2008. - Paris (France). - P. I2 -1 - I2 - 6.
[8]. Bulat LP, Drabkin I.A., Pivovarov GI, Osvensky VB On thermoelectric properties of nanoscale materials // Journ. of Thermoelectricity. - 2008. - No. 4. - P. 27 - 33.
[9]. L.P. Bulat, E.K. Iordanishvili, A.A. Pustovalov, M.I. Fedorov. Thermoelectricity in Russia: history and sovremennoe sostoyanie. See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/282868212. ISSN 1726-7692 Thermoelectricity №4, 2009. Str.3-26.
[10]. A.M.Kasimaxunova, S.I.Zokirov. Photothermoelectric batteries, Monograph. "Classic" publishing house, 2021. 156p.
