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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Will a new energy age come? Electricity without cars. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Alternative energy sources At the beginning of the last century, inventors and scientists were already well aware of the benefits that the widespread use of electricity could provide. However, there were no ways to obtain it cheaply in sufficient quantities for a long time. But in 1821, a curious phenomenon was discovered by the German scientist Seebeck. If we take a closed circuit of two dissimilar conductors soldered together and heat one junction and cool the other, then a current will appear in the circuit. In this surprisingly simple device (they called it a thermoelement), thermal energy, as it were, is directly converted into electrical energy.
In the galvanic cell known long before him, energy was obtained by dissolving the metal in the electrolyte. These substances are quite expensive, and energy was not cheap either. The thermocouple is another matter. He himself is not consumed, and the fuel is quite affordable. Moreover, its junctions can be heated by anything: the sun, volcanic heat, combustion products flying out through the furnace pipe, etc.
Let's take a closer look at some of its properties. A single thermoelement develops a small EMF - tenths, hundredths of a volt. However, its internal resistance is very small, therefore, the current generated can be very large. Such a beautiful experiment has long been known. An electromagnet with an iron core and a winding consisting of ... one turn. But the turn is a bracket made of copper as thick as a finger, closed with a soldered jumper made of bismuth. We heat one end of the junction with an ordinary laboratory burner, and cool the other with water. A current of thousands of amperes arises, and the magnet (with one turn!) Holds grandmother's cast-iron iron.
Low EMF is not a problem, thermoelements are easily connected into a battery with hundreds or thousands of sources connected in series. It looks like an accordion of alternating strips of two metals. A strong current at a moderate voltage of 2-3 volts was the best suited for use in small electroplating workshops. It was produced by thermoelectric generators, resembling a small stove on wood, coal or gas. They were used by handicraftsmen at the beginning of the century. There were also attempts to solve larger problems. So, for example, at the end of the 80s of the last century in Paris, Clouet built a thermoelectric generator that provided energy for 80 Yablochkov's "candles". The efficiency of installations of that time did not exceed 0.3%. It would seem that very little, but all the lost heat could be used to heat the house, heat water or cook food. Heating furnaces with built-in thermoelectric generators were also offered. It is curious that their installation in no way increases fuel consumption for heating. After all, electricity, if it is used up in the same room, will again turn into heat! History decreed otherwise. Electricity turned out to be much more profitable to produce at power plants and centrally distributed to consumers. Even in the last century, the efficiency of power plants was ten times higher than that of thermoelements. However, the elegant simplicity, the reliability brought about by the absence of moving parts, fascinated many. Attempts to increase the efficiency without deep insight into the theory did not lead to serious success. EMF arises as a result of heating the thermoelement legs, but at the same time, a parasitic heat flow arises, flowing uselessly from the hot junction to the cold one. Trying to use it, they began to assemble cascades of thermoelements in which the colder junction of one heats the hot junction of the other. The temperature of the hot junctions at each stage of the cascade decreases. However, by selecting materials that work best in a given temperature range, the efficiency of the entire system can be significantly increased. There is another possibility. It is called heat recovery. Let us direct the air flow along the thermoelectric cascade from the cold end to the hot one. At the same time, it will acquire from the elements part of the heat flowing through them and heat up. After that, we will direct hot air into the furnace and save some fuel. This whole procedure is equivalent to reducing the thermal conductivity of thermoelement materials, and it will be beneficial only if a strictly defined part of the heat is removed from each element. However, regeneration is noticeable only when the thermoelements themselves, included in the cascade, are sufficiently perfect. In the 30s, theoretical work in the field of thermoelectricity was especially intensively carried out in our country. They say there is nothing more practical than a good theory. Academician A.F. Ioffe created a new theory of processes occurring in a solid body. Some reputable scientists took it with hostility, called it "quantum-mechanical subconscious." But in 1940, based on her findings, it was possible to increase the efficiency of the thermoelement by 10 times. This happened due to the replacement of metals by semiconductors - substances with a higher thermoelectric power and low thermal conductivity. At the beginning of the war, a "partisan boiler" was created in Ioffe's laboratory - a thermoelectric generator for powering portable radio stations. It was a kettle, on the bottom of which thermoelements were located outside. Their combustible junctions were in the fire of the fire, and the cold ones, attached to the bottom of the pot, were cooled by water poured into it.
Careful selection of materials, the use of regeneration have made it possible in our time to bring the efficiency of the thermoelement up to 15%. At the beginning of the century, conventional power plants had such efficiency, but now it has more than tripled. There is no place for a thermoelement in large-scale power engineering yet. But there is also a small energy. Several tens of watts are required to power a radio relay station on a mountain top or a sea signal buoy. There are also remote places where people live who need electricity and heat. In such cases, thermoelements heated by gas or liquid fuel are used. It is especially valuable that these devices can be placed in a small underground bunker and left completely unattended, only once a year or less often to replenish the fuel supply. Due to the low power, its consumption at any efficiency turns out to be acceptable, and besides ... there is no choice. Doctors have found a curious application for thermoelectric generators. For more than two decades, thousands of people have been wearing an implanted pacemaker placed under the skin. The source of energy for it is a tiny (with a thimble) battery of hundreds of thermoelements connected in series, heated by the decay of a harmless isotope. A simple operation to replace it is performed every 5-10 years. In Japan, electronic watches are produced, the energy of which is provided by a thermoelement from the heat of the hand. Recently, an Italian company announced the start of work on an electric vehicle with a thermoelectric generator. This current source is much lighter than batteries, so the mileage of a thermoelectric car will be no less than that of a conventional one. (Recall that electric vehicles can travel 150 km on a single charge.) It is believed that through various tricks, fuel consumption can be made acceptable. The main advantages of the new type of crew are absolutely harmless exhaust, noiseless movement, the use of the cheapest liquid (and possibly solid) fuel, and very high reliability. In the 30s, the work carried out in our country on thermoelements was widely known. This is probably why the writer G. Adamov described in his novel "The Secret of Two Oceans" the Pioneer submarine, which received energy from battery cables. So he called thermoelectric generators made in the form of long cables. With the help of a buoy, their hot junctions rose to the upper layers of the ocean, where the temperature reaches 20-25 ° C, and the cold ones were cooled by deep water with a temperature of 1-2 ° C. So the fantastic "Pioneer" is a boat capable of giving a hundred points ahead of the current nuclear, charged his batteries. Is it real? There is no report of direct experiments of this kind in the press. However, something curious came up. A thermoelectric generator with a capacity of 1000 kW has been created, which generates energy from the heat of hot underground sources. The temperature difference between the hot and cold junctions is 23°C, as in the ocean, the specific gravity of 6 kg per 1 kW is much lower than that of conventional submarine power plants. Are we on the threshold of a new energy revolution, a new age of electricity? Author: A. Saveliev
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