Thermoelectric generator - is a device that receives the electrical energy from the heat. An excellent source of energy, unfortunately, is characterized by low efficiency. In addition, the DC current is converted transformers.
History of discovery
Seebeck discovered in 1822 year (as other data - from 1820 to 1821), when heated junction of different materials in a closed circuit current flows. conversion efficiency of 3%. Despite such a miserable figure, the result of the first thermoelectric generator competed with steam engines of the time. Experimenting with the plates of antimony and bismuth, Seebeck measurement conducted galvanometer Shveyggera (inductor and magnetic arrow). Therefore, the experiments did not start before September 16, 1820. The apparent insignificance and inexplicable events have forced the scientist to wait. Slowly, examining its own discovery Seebeck made a report about it only in 1823.
By logical reasoning researcher suggested that the earth's magnetism is explained by the difference in temperature between the equator and the poles. The operating principle of a thermoelectric generator explained magnetic polarization. Seebeck investigated weight samples, including semiconductors, and materials are arrayed in a row by the ability to reject magnetic needle. This data is used (in the refined form) and today for the construction of thermoelectric generators. The Seebeck coefficient is measured in mV / K.
As scientists radioactive metals, as Seebeck treated samples. After World War II, when it became known that the United States has a stunning new weapons, there was an order by all means to accelerate the development of nuclear weapons. Prisoners and just experimenters virtually hands colliding pieces of radioactive rocks to achieve a chain reaction. Most soon died.
Seebeck alive. He took his hands bismuth and antimony, short circuit and as Galvani had once watched "animal electricity." Seebeck almost believed in their own wonderful transcendent abilities, but housekeeper made him think that the reason the samples were heated. When the magician's career finally left the hands of the great scientist, he returned finally to physics. It turned out, if the metal dock tightly and heat lamp, the needle deviates even further.
Initially, explanation of the observed effect and gave an unusual called magnetic polarization. From the point of view of modern science is difficult to explain such a position, but if you look through the eyes of his contemporaries... in September 1820 Hans Oersted reported to the scientific community in France and Great Britain on the opening, The revolution in the next 100 years. The scientist did not hurry: noticing strange behavior of marine compass, long studied, evaluated, and then write a few progressive thought contemporaries... Further discoveries fell succession:
- Ohm's law.
A long list of all the inventions the next 15 years, but open Seebeck thermoelectricity was surprising. It is known that Ohm used Georg pair of bismuth and antimony, for output to the known law circuit portion. In the days of the Seebeck existed notion charge, magnetism, electricity, capacity capacitor - and all! Unknown concepts were potential differences, currents, electromagnetic fields and their intensity. This has influenced the name of the opening of the Seebeck.
On the eve of Malus, Fresnel, Jung and Brewster published work on the polarization of light. This phenomenon was investigated on the basis of Iceland spar crystals, then introduced the term axis (from the Greek. - pole-axis). The magnetic poles showed Globe. Not surprisingly, the Seebeck attributed own installation like a strange name. The coil is oriented like a compass needle planet Earth.
During the year, we managed to find the correct explanation. Georg ohms using a thermocouple as a stabilized voltage source for opening the known law: sets a fixed temperature difference across the boiling point of water, and melting ice. It is time to open the era of thermoelectricity.
Thermoelectricity development concept
When it became clear that the heat is not capable of directly converted into magnetism, finally, rejected the idea of forming field of the Earth heat erupting volcanoes and magma boiling inside. Comparing the experiences of Oersted and Seebeck, the scientific community has found the right path. For Georg Ohm thermocouple as a thermoelectric generator was used in the electrolysis (1831). But the term remained unstable. It is believed that the first thermoelectric generators appeared in the second half of the XIX century. Considered a laboratory setup for studying various processes, were called differently.
The postal and telegraph magazine closer to 1899 published an article on the establishment of a battery to supply power 16 candelas of light bulbs. In the furnace the furnace thermocouple placed, with sufficient voltage and current. Combining supply elements in series, the voltage was raised. A parallel connection at increased current. Each thermocouple is constructed by use of Seebeck (antimony - zinc antimonide). Then we have learned Gyulhera battery (presumably in 1898).
The term coined for the battery of Leyden jars (capacitors) Benjamin Franklin.
So in scientific circles series connected thermocouples dubbed thermopile. It is believed that the first device created Oe and Fourier in 1823. They combined Seebeck thermocouple for powerful power source. Further development of the concept was to supply Leopoldo Nobili and Macedonio Melloni: for a series of experiments on the study of the infrared spectrum, they created a thermal multiplier. The idea came both after making progressive changes in the structure Shveyggera (1825).
The idea of the first galvanometer the effect of turns of the wire multiplied by their number. Similarly it is going "heat power" of the thermocouples. The device is intended for the whole study of the infrared spectrum due to the measurement of the produced heat, but later the concept was the basis for the creation of new sources of supply. Indicator termoumnozhitelya became a compass needle.
Timeline of inventions
After the first swallow Seebeck effect has been applied and further. The patent for the use of thermoelectric generators replace conventional taken in 1843 by Moses Poole.
Pergeliometr to measure solar activity
Pergeliometr for measuring solar radiation intensity according to the degree of heating of the thermocouple. Claude Pouillet invented between 1837 and 1838 years device enabled the scientist to calculate with high accuracy the solar constant of 1228 W / sq. m. pergeliometr not originally intended to be used as the thermoelectric generator. Individual achievements serve as a support structure for the further progress of the industry.
We give details of the invention, taken from the research of Dr. Stone's report delivered November 18, 1875. "The alloys exhibit the properties of metals combined powerful than each of the simple materials individually. In the composition of one part and two zinc - antimony difference sample gave 22.7 potentials. The potentials of the components taken separately:
- Antimony - 7 - 10.
- Zinc - 0.2.
The only exception was an alloy of bismuth and tin. When the composition of his 12 to 1, the potential decreases from 35.8 to 13.67. I was fortunate enough to begin studies with a pair of German silver (nickel-rich) and iron. The observed EMF was not great. Then I tried Marcus alloy consisting of 12 parts of antimony, zinc and 5 1 bismuth. The result was fragile and with a pronounced crystalline structure.
To smooth out these shortcomings, added arsenic. As a result, discovered that an alloy of antimony, arsenic, zinc and tin with a small admixture exhibits much greater plasticity in similar thermoelectric properties, which are observed in the alloy Marcus. The second part by a pair of nickel silver. "
Thermopile Marcus was equal to one-twentieth of the Daniell cell, giving 55 mV DC. Negative "a facing" served as an alloy of copper, zinc and nickel in the ratio 10: 6: 6, similar in appearance to a nickel silver; positive - compound of antimony, zinc and bismuth in the ratio 12: 5: 1. According to the «Electricity in The Service of Man», 3rd edition 1896, in May 1864 Marcus won by the Vienna scientific community for a thermoelectric generator. Structured hut thermocouple at the top of the heated metal strip united. The lower part of the cooling water. Unfortunately, the alloys in air rapidly oxidized to a grand increase in ohmic contact resistance.
contribution to Becquerel
It is not known, when was born thermoelectric generator Edmond Becquerel, but historians date the opening for the period 1867-1868 year. Its structure is formed by the transition sulphide copper and nickel silver. In the image: a proximal reservoir pumped cold water into the far - incandescent gas. Voltage thermoelectric generator filmed with spiral terminals.
thermoelectric generator Klemonda
About thermoelectric generators Dr. Stone stated: "The use of iron gives a nice effect that is offset rapid rusting of the product."
- The thermoelectric generator (presumably 1874 issue) Klemonda and Moore constructed of zinc antimonide and pure iron especially for electrolysis purposes. Heated device allowed one hour to obtain about ounce copper, consuming 6 cubic feet of gas. It was used for plating metallic products. Gas regulator thermoelectric generator changes the magnitude of the resulting electrical current. The figure as seen from the top sectors of zinc antimonide, triangular leaf blades - iron.
- In 1789, thermoelectric generator Klemonda appeared much improved. When the internal resistance of 15.5 ohms gave voltage 109 V at a current of 1.75 A, consuming 22 pounds per hour of coal. compounds switching voltage decreased to 54 V. thermoelectric generator current increased to 3.5 A. Heated coal furnace construction height under 2.5 meters in diameter within a meter resembling cooler modern processors contained outside numerous iron wings. Gases pass inside Raskalov zinc antimonide. By individual messages issued thermocouples 20 generator 1 voltage.
- Thermoelectric generator Noah (probably in 1874) is more like a modern turbine thermal power plants in form. The central part of the burner termpopar heated and cooled peripherals through radiation and convection. This relatively small similarity Klemonda generator with internal resistance of 0.2 ohms, calculated on voltage of 2 V and 128 consisting of thermocouples. The efficiency of the thermoelectric generator is greatly reduced Nickel silver intermediate contacts dissipating heat. Modern thermoelectric generators using p-n-transition without intermediate between semiconductors materials.
- Portable thermoelectric generator Hawke (probably in 1874) is designed for 110 mV (one tenth Daniell cell) and included 30 thermocouples with halves united platinum wire length 1.2 inches. Bunsen burner is strongly reminiscent and cold end immersed in water. The design is strongly reminiscent invention Noe and less Klemonda. The key difference lies in the commercial production of products for the mass range of consumers. Generators sold two and three, placed on a uniform basis.
- Coal thermoelectric generator invented by Harry Barringer and copyrights are secured by the patent US434428 by 1890.
Last year of the invented in the XIX century. Historians date it to 1898. 50 thermocouples allowed voltage of 1.5 V at a current of 3 A and the internal resistance of 0.5 ohms. For these purposes is spent every hour 5 cubic feet of gas. According to researchers, the instrument would produce a good three times with identical flow rate.
Natural experiment showed an average life of 200 hours, although one sample spent 500 finally found a copy, who served for two years. In 1903, a magazine published information about public trials Gyulhera battery. During the lit burner thermocouple warmed until the voltage reached to 3.5 V. Then turn off the device and viewed on characteristics after termination of the gas supply. If the voltage drops to 1.5 V, the current stopped abruptly. Output:
- stable thermal stresses that due to the considerable thermal inertia. Temperature changes occur slowly, gently lowered voltage during cooling.
However, a similar notice more Poggendorff, advised George Omu use thermocouple instead of the voltaic pile. Gyulhera battery proved popular in the early XX century. For example, Lihaysky University reports that a new metallurgical laboratory in 1905 bought three thermopile Scott and one - Gyulhera.
The design resembles an outdated heating radiator today. These are found in public buildings, constructed and equipped in the USSR. This portable device: on each side is a T-shaped handle for transportation.
Portable thermoelectric generator Sudras resembles in appearance the oil filter of the truck. To obtain the heat required to ignite the gas burner. It remained extremely little information about the device. In the editions of 1898 found a joint trial information products with the aforementioned text:
"Professor Kolrauh observed in 70 that the thermoelectric generator voltage dependent on the number of pairs included in series. This is confirmed by experiments on structures Klemonda, Noe and Sudras, manufactured and sold over the past 20 years. They provide 2, 4, 6 and 8 volts, having, respectively, 36, 72, 108 and 144 pairs in the composition. It is seen that the voltage exactly proportional to the total number. Sudras constructed instance, consists of 720 members. As you might expect, the resulting voltage was 40 V, the ability to support combustion of the discharge lamp. "
The note stated that the novice electrician has the right to take the photo submitted to the sample for example a commercially successful product. Thermoelectric generator Shudr manufactured in sizes 6, for currents of 1.3 - 2.5 A at a voltage of 3 - 8.5 V, depending on the size and number of elements.
In XX century the majority of thermoelectric generators supplied with the patent, and the fuel gas has become. A feature of the period considered in theory attempts to explain the observed phenomenon. The first calculated the efficiency of thermoelectric generators Reilly, although the result was wrong. In 1909 and 1911 attempts were made to give a theoretical study of materials: Altenkirch showed that thermoelectric materials should have a large Seebeck coefficient and low ohmic contact resistance for reduce heat losses.
Funny, but used today to create powerful devices semiconductors remained outside Seebeck interests entirely focus on pure metals and alloys. In these materials, according to the Wiedemann-Franz law-Lorentz relation to the heat conduction of electric considered constant. Suitable metals for thermocouples recognized metals, where the Seebeck coefficient maximum.
Significant developments in the field of synthesis occurred in the period of the 30th year of semiconductors with the values of Seebeck coefficient exceeding 100 mV / K. As a result, after the Second World War (1947) appeared on the scene generator M. Telkes with an efficiency of 5%. A couple of years loffe developed the theory of semiconductor thermocouples. Unfortunately, the interests of the great powers disagreed, did not immediately realize that semiconductors pose great potential. In 1956 godu Joffe and colleagues showed that too large ratio of thermal and electrical conductivity is decreased melting materials with different compounds. Due to the large military value, many developments have remained under wraps, for example, RCA study.
Modern generator is concluded between a sandwich of ceramic plates ingot p and n semiconductors. When creating a desired temperature differential device produces energy. Ceramics is considered worthy electrical insulator but conducts heat, proving successful said structure. The vacuum on one side Heatable sun and on the other - cooled gloss stars thermoelectric generator fantastic shows the temperature difference between the surfaces. Which naturally will increase the power output. Therefore, it is a good source of nutrition, easy and convenient for any space objects.
In the early 60's from outer space thermoelectricity slowly descended to earth. Preferred fields of medicine and began to study the planet's surface (including minerals). The key advantages of the new technology began to ease, reliability, no moving parts, quiet and disadvantages - a considerable cost and low efficiency (earlier 5%). The approximate calculation of the feasibility of using new materials:
- The presence of air is assumed to reflect the hydrocarbon.
- On moving objects in the first place saves space. In this case the energy density of the liquid fuel 50 times higher lead accumulators or batteries.
- Consequently, when the efficiency of the thermoelectric semiconductors than 2% of their use becomes warranted. And oil is burned slowly, reducing the total weight of the object.
In some cases, heating thermoelectric generator manages to carry radioactive isotopes, opening new horizons. Such a source was used on the Voyager (1977) and worked for over 17 years. With the rising prices of oil (crisis of 1973), the US government turned its attention to new energy sources: waste water discharge powerful enterprises having huge potential. The studies addressed interesting things: semiconductor superconductivity at relatively high temperatures (150 - 170 K) to improve properties of the thermocouples. Later efforts focused on bringing to the condition of the element base of germanium and silicon.
Open today thermoelectric materials conventionally divided into three groups of operating temperature:
- Bismuth telluride and alloys show best quality indicators at 450 K.
- Tellurides and lead alloys exhibit reduced performance, but at temperatures of 1000 - 1300 K.
- Finally, silicon and germanium compositions have low efficiency, but a well-established manufacturing techniques. Operate at temperatures 1000 - 1300 K.
Design of the XX century
Thermoelectric generator Termattaiks 1925 is characterized by complex pronunciation for the name and on the front panel contains a voltmeter to check the voltage. Strictness by the fact of: the device is a battery charger for lead-acid batteries of 6.3 V. It is meant the possibility of using a thermoelectric generator directly as the means for heating the cathodes of electron tubes.
The front panel knob is supplying combustion gases to influence the output voltage. Some authors suggest large fluctuations, but the text has already expressed the view of acceptable stability of thermoelectric generators. Consequently, the possibility of their use in the context of the observation made obvious.
Amateur Wireless magazine suggested that the thermoelectric generator is good enough to power the portable amateur radio station in the campaigns and expeditions. In the absence of electricity, it is obtained in limited amounts, burning oil, gas, coal, wood.
Expressed above idea of radio power from any fuel implemented already in the 30s of the thermoelectric generator. A company The Cardiff Gas Light & Coke released the relevant advertising. The inscription "thermoelectric generator" for the first time is worth. Previous samples stubbornly termed in the literature batteries, batteries or remained without a title. Reklamka says, when the energy runs out, the gas stream allows to listen to the latest radio broadcast anywhere in the world. Such times: Dose of coal, and the news is always there.
This thermoelectric generator is a portable unit receiver power and provides a display cathode voltage of 2 V at an output current of 0.5 A and a voltage diagram 120 V at current consumption 10 mA. The informational note to the leaflet states that the thermocouple does not give a lot of stress, but to get more wire connections, it remains possible to obtain a satisfactory result.
The most successful materials for the thermoelectric generator are considered, according to the manufacturer, a combination of nickel-nichrome. Seebeck coefficient for them is 40 mV / K, with a working temperature up to 1000 K. Warming up the receiver, the voltage reached 40 mV. If thermocouples 50 connected in series, forms 2, which is enough for heating the cathodes of the electron tubes. 120 In 3000 obtained the inclusion of thermocouples in a single chain.
Presented at the picture kerosene lamp surrounded by a shade of the thermoelectric generator is developed under the direction of Ioffe. This product is post-Stalin era, dated 1959 year, allows you to simultaneously listen to the radio and record confidential summaries. A true friend of the underground worker. Thermoelectric generator produces voltage amplitude for heating the filament of 1.5 V at a current of 125 mA, the entire device 90 feeds the voltage at a current of 12 mA.
Good news! In 2005, Jason Hopkins proved that the efficiency of the thermoelectric generator is able to get closer to the ideal. We are waiting for new products in this area.