|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Thermoelectric generators. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Alternative energy sources Thermoelectric generator - a device for direct conversion of thermal energy into electrical energy. Thermoelectric generators are made on the basis of thermoelements. The most efficient thermogenerators use complex semiconductor compounds; their power can reach several tens of watts, efficiency - 20% (with a temperature difference of hot and cold junctions of thermoelements - about 1000 K). This year are especially effective when using the heat released during the operation of rocket engines, nuclear reactors, blast furnaces, etc. The thermoelectric generator is designed to power various radio equipment, communications, lighting and recharge batteries. It converts the heat of domestic sources (kerogas, stove, gas burner, stove, fire) into electrical energy. 1. Solid fuel thermoelectric generators TEG fueled by charcoal and cooled by water or air. The structural diagram is shown in fig. 7.3. Their main characteristics are shown in Table. 7.1.
Table 7.1. Characteristics of TEG on charcoal
TEG with heating of hot junctions by burning charcoal and cooling of cold junctions with boiling water (see Fig. 7.4, 7.5) has a cast-iron furnace 6, in which coal is burned, loaded into hopper 4 through neck 1. Combustion products leave through pipe 2 In the space between the inner casing 3 and the outer casing 5 there is boiling water, which maintains the temperature of the cold junctions of the TEEL at about 100°C. Thermoelements 8 are electrically insulated from the installation structure by thin layers of mica. Thermal contact between casing 3 and TEEL is carried out by a fusible alloy poured between them.
The TEG has two independently operating TEEL batteries: one for powering the heating circuits, the other for powering (with the help of a vibration transducer) the anode and grid circuits. The disadvantages of such a TEEL: the difficulty of making thermal contact between the TEEL and the refrigerator, the presence of boiling water and the difficulty of controlling the coal furnace.
TEG on wood and coal Further development of solid fuel TEGs led to the creation of several more models of larger TEGs with a power of up to 500 W or more. These units were stoves using coal or wood, with thermopiles built into the walls. As an example, we give generators designed for the Far North at 200 and 500 W, operating on any fuel - wood, coal, oil. A 200 W generator consumed about 2 kg of firewood in 1 hour. It was intended to produce electricity, hot water or steam used in animal husbandry. However, TEG operation on coal is unstable due to difficulties in ensuring a uniform fuel supply. The next start-up of the TEG required preliminary cleaning of the furnace, reaching power took a long time, etc. Therefore, the further development of TEG went along the path of using liquid fuel. Intermediate TEGs for solid and liquid fuels The advantages of liquid fuels have led to the emergence of intermediate designs suitable for operation on both liquid and solid fuels. These structures include the one shown in Fig. 7.6 scheme of the TEG installation according to the American patent.
Here, 145 thermoelectric elements made of wire 0,5 mm in diameter are embedded with cold ends into the bottom of a Bakelite cup 5 cm in diameter supported by a tripod. The hot ends of the elements are heated by the flame of a conventional alcohol burner. One branch of TEEL is made of constantan, the other is made of an alloy of nickel (91%) with molybdenum (9%). The output voltage of the generator is 6 V. This circuit is very similar to the TEG-1 circuit, but in a different design: with metal fuel cells and replacing the fire with an alcohol burner. 2. Liquid fuel thermoelectric generators TEG on kerosene of the type TGK-1, TGK-3 and TGK-2-2-TEG on kerosene are based on the use of conventional lighting kerosene lamps as a heat source and, along with generating electricity, are light sources. The design schemes of TGK-1, TGK-3 and TGK-2-2 are the same: incandescent combustion products of kerosene heat hot junctions of TEEL from SbZn and constantan, cold junctions have air cooling fins. The power of TGC-1 is about 1,6 W, TGC-3 is about 3 W. The main characteristics of TGK-3 are shown in Table. 7.2. Table 7.2
On fig. 7.7 shows the TGK-3 generator, which, in its basic design scheme, differs little from the TGK-1, but has more power. This TEG uses a 20-line round-wick kerosene lamp 8 and 7, and a metal heat pipe. 2 and 6 shown in fig. 7.7, has 14 faces for TEEL. Each TEEL block is cooled by one independent double rib 3, as in TGC-1. The height of the TGC-3 from the lower edge of lamp 8 to ring 1 is about 1 m, the radiator diameter is 300 mm. A single charge of the lamp is enough for about 10 hours of operation. The energy generated by TGK-3 is quite enough to power various radio receivers and other devices that consume a voltage of 1 - 2 V at a current of 0,3 - 0,5 A and a voltage of 90 - 120 V at a current of 8 - 11 mA. 3. TEG on gaseous fuel The use of gas simplifies the regulation of the heat input (easily achieved by regulating the gas pressure in the burner), ensures good combustion of the fuel at various temperatures and is not accompanied by the accumulation of slag. All this creates conditions for long-term and stable operation of the TEG. In particular, the fifties are characterized by the construction of pipelines to deliver natural gas and oil over long distances to the centers of consumption. Related to this is the beginning of the widespread use of TEGs running on gaseous fuel in our country for cathodic protection of gas pipelines and other pipelines from corrosion (in areas without power plants), to ensure the safety of pipelines at minimal cost, and also for other purposes. Gas pipelines located in the field of stray currents or in aggressive soils quickly fail as a result of the appearance of shells, fistulas and other damage in places where the insulation of pipelines is broken. The pipeline cathodic protection station is a direct current source with a power of up to 0,5 - 1 kW at 10 - 20 V, the negative pole of which is connected to the gas pipeline with an insulated cable, and the positive pole is grounded. For cathodic protection, several types of TEG have been created in Russia with a power from 10 to 300 W, including TGG-10 and TGG-16. They have one TEEL battery each and operate on gas fuel. Batteries consist of separate sections. The hot junction is pressed against the silumin heat transfer device, and the cold junction is pressed against the cooling aluminum fins. The battery is a cylinder, in the lower part of which a gas burner (PB-40-4) is placed, to which gas is supplied under an overpressure of about 0,015 atm. The TEG unit has a solenoid valve capable of cutting off the fuel supply. Usually, gas is supplied to the TEG from gas pipelines connected to the houses of linemen. The TGG-10 generator basically does not differ in principle from general-purpose generators, it only uses a gas burner instead of a kerosene lamp. The TEG TGG-16 uses an improved method of heat removal from hot gases using perforated disks. The scheme of this TEG is shown in fig. 7.8. These generators are heated to operating temperature in less than 30 minutes. Gas consumption (7000 - 8000 kcal/m) is 0,1 - 0,2 m3/h. Low thermal efficiency in these installations is insignificant, since the gas consumption is negligible, the main thing is reliability and simplicity, low operating costs.
3. Thermoelectric generators powered by solar energy Solar TEG for space purposes. TEG, the scheme of which is shown in fig. 7.9 is based on the use of small TEEL with a volume of about 2,5 mm3, placed between two parallel plates (for example, metal foil) in an amount of about 3000 pieces. per 1 m2; TEEL are isolated from the plates and connected in series-parallel. In outer space, one plate facing the Sun heats up to 300°C, while the other (cold junctions) has a temperature of about 70°C. Each TEEL in this design can produce a power of about 10 MW with an efficiency of about 2%. 1 m2 of thermoelectric panel of the model weighs 10 kg and can produce approximately 30 - 40 W/m of electricity. Such a solar generator for a spacecraft was made in the form of a cassette with a surface of 30 cm with 12 rows of TEELs, 12 TEELs in each row. It was characterized by the output of 2 W of electricity when heated by the Sun in outer space. Solar TEGs with flat heating surfaces do not make it possible to obtain a good efficiency of TEEL (especially under terrestrial conditions) due to small temperature differences between hot and cold junctions. The best results can be obtained using solar energy concentrators, although this complicates the design.
4. Thermoelectric generators with solar energy concentrators As already noted, the efficiency of TEEL grows in proportion to the temperature difference between the hot and cold junctions and, in addition, to the absolute temperature of the hot junction. Therefore, a noticeable increase in the thermal efficiency of the TEG is achieved by using solar energy concentrators, which make it possible to increase the temperature of the hot junction of the TEEL up to 1000°C. A thermoelectric solar generator with a concentrator is a thermopile installed in the focal zone of a spheroidal or cylindrical mirror (Fig. 7.10). The sun's rays collected by the mirror are directed to the surface of the hot junctions and heat them up. Cold junctions are cooled by air, water radiators or through radiation. Various models of solar TEG with heat concentrators, including those with large and small concentrators, and with heat accumulators have been developed. A serious disadvantage of solar TEGs with energy concentrators is the high cost of the concentrators themselves.
1 - parabolic reflector; 2 - solar heat receiver; 3 - TEEL; 4 - heat sink Thermoelectric generators with some other heat sources The possibility of using other heat sources, both with large and small temperature differences, to generate electricity using TEEL (geothermal water, human body heat, exhaust gases from rocket launchers, etc.) has found its implementation in a number of unique TEG designs. For them, the most suitable thermoelectric materials with high quality factor at low temperatures. Such materials include lead telluride with the addition of 0,1% sodium, the quality factor of which is 0,8-10-3 (deg)-1 at 200°C and 1,410-3 (deg)-1 at 0 ° C. The use of heat from geothermal waters can be of great practical importance. Experimental samples of TEG have been created that are suitable for using the heat of natural hot springs. The insufficiently high thermal efficiency of such a thermoelectric geothermal power plant can be compensated by the simplicity and reliability of the TEG, the ability to operate without maintenance personnel. The heat of the human body can also be used to create a temperature difference between the hot and cold junctions of the TEEL. Such TEGs made from good TEMs are able to provide a power of 0,01 W or more if the temperature difference is about 40 - 50°C. Several dozen miniature TEELs form a flexible bracelet worn on the wrist. Such a TEG can provide power to a transistorized receiver and transmitter, especially in cold climates. Another example of devices of this type is the Japanese solid-state radio receiver, which does not need galvanic batteries or accumulators. There is a thermoelectric device here that provides the necessary electric current if the thermoplate is put on the hand. Author: Magomedov A.M.
Traffic noise delays the growth of chicks
06.05.2024 Wireless speaker Samsung Music Frame HW-LS60D
06.05.2024 A New Way to Control and Manipulate Optical Signals
05.05.2024
▪ ICL5102 - Efficient half-bridge AC-DC converter controller with PFC ▪ Revealed the secret of successful people ▪ The most powerful computer in Europe
▪ section of the site For a beginner radio amateur. Article selection ▪ article Hydroelectric power plant. History of invention and production ▪ article Why are extremely severe punishments called draconian measures? Detailed answer ▪ article Construction electrician. Standard instruction on labor protection
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page