Ways to directly convert nuclear fission energy into electrical energy have not yet been found. We still cannot do without an intermediate link - a heat engine. Since its efficiency is always less than one, the “waste” heat needs to be put somewhere. There are no problems with this on land, in water or in the air. In space, there is only one way - thermal radiation. Thus, KNPP cannot do without a “refrigerator-emitter”. The radiation density is proportional to the fourth power of absolute temperature, so the temperature of the radiating refrigerator should be as high as possible. Then it will be possible to reduce the area of the radiating surface and, accordingly, the mass of the power plant. We came up with the idea of using “direct” conversion of nuclear heat into electricity, without a turbine or generator, which seemed more reliable for long-term operation at high temperatures.
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The organizer and first director of the Physico-Technical Institute is Abram Fedorovich Ioffe. |
The trouble with kerosene TEG is its low efficiency (only about 3.5%) and low maximum temperature (350°K). But the simplicity and reliability of these devices attracted developers. Thus, semiconductor converters developed by the group of I.G. Gverdtsiteli at the Sukhumi Institute of Physics and Technology, found application in space installations of the Buk type.
At one time A.F. Ioffe proposed another thermionic converter - a diode in a vacuum. The principle of its operation is as follows: the heated cathode emits electrons, some of them, overcoming the potential of the anode, do work. Much higher efficiency (20–25%) was expected from this device at operating temperatures above 1000°K. In addition, unlike a semiconductor, a vacuum diode is not afraid of neutron radiation, and it can be combined with a nuclear reactor. However, it turned out that it was impossible to implement the idea of Ioffe’s “vacuum” converter. As in an ion propulsion device, in a vacuum converter you need to get rid of the space charge, but this time not ions, but electrons. A.F. Ioffe intended to use micron gaps between the cathode and anode in a vacuum converter, which is practically impossible under conditions of high temperatures and thermal deformations. This is where cesium comes in handy: one cesium ion produced by surface ionization at the cathode compensates for the space charge of about 500 electrons! In essence, a cesium converter is a “reversed” ion propulsion device. The physical processes in them are close.
Nuclear power plant "Buk" with
semiconductor reactor-converter for
radar satellites
Nuclear energy thermionic installation "Topaz".
THERMAL EMISSION CONVERTER
Name of inventor: Prilezhaeva I.N.; Bologov P.M.
Name of the patent holder: State Scientific Center - Physics and Energy Institute
Correspondence address:
Patent start date: 1996.09.18
Purpose: thermionic conversion of thermal energy into electrical energy. The essence of the invention: in a thermionic converter containing multilayer electrodes, at least one layer is made of a hole semiconductor, which is located on the surface of the emitter facing the collector, or on the surface of the collector facing the emitter. Technical result: reduced work function of electrons on the collector, reduced emission of electrons from the surface of the collector, the ability to select a hole semiconductor for different levels that is stable under the operating conditions of the converter.
DESCRIPTION OF THE INVENTION
The invention relates to the field of energy and electronics.
Thermionic heat-to-electricity converters (TECs) have advantages over other converters in the absence of moving parts and high heat release temperatures. These advantages led to the use of nuclear power plants with a TEC-based converter in space on the Kosmos-1818 and Kosmos-1867 satellites in the late 80s. In terrestrial conditions, the use of a low anode cooling temperature is acceptable and a higher efficiency is required. The main ways to increase the efficiency of a TEC at a given temperature range are to reduce the energy losses of emitted electrons on the path between the emitter and the collector and reduce the work function at the collector. The sum of these losses usually exceeds 2V at an operating voltage of the TEC of 0.5V. So far, TEC developers use only 1/5 of the energy of the emitted electron. Research to reduce the energy loss of an emitted electron is ongoing, but it has not been possible to reduce the work function of the collector below 1.7 eV for TEC power plants. The basic solution is the use of cesium in TECs, which forms a plasma in the interelectrode gap of the TEC, which compensates for the blocking space charge of emitted electrons and is sorbed on the emitter and collector, which allows maintaining the output function of the emitter and collector within the limits of energy production with an efficiency of about 10%
As an analogue, we will indicate solutions for regulating metal-semiconductor transitions by doping thin layers. These methods make it possible to reduce the energy barrier between the semiconductor layers and the base metal of the emitter and collector to zero.
As a prototype for the proposed solution, we point out a TEC with a niobium-based collector, saturated in the surface layer with oxygen up to 1%. Cesium sorption on such a collector passes to a significant extent through oxygen, which reduces the work function of the collector to 1.4 eV and accordingly increases the efficiency Disadvantage of the prototype is the instability of the reservoir composition due to the transition of oxygen to other phases. Therefore, this solution has not found industrial application.
The proposed solution makes it possible to reduce the work function of the collector by introducing a thin semiconductor layer that is stable under TEC operating conditions. The use of semiconductor layers makes it possible to regulate the output function over a wide range and will ensure low electrical losses when current flows in the direction normal to the semiconductor layer. A thin layer of semiconductor must be stable under operating conditions and have a chemical affinity for electrons.
The advantages of the proposed TEP over the known ones are:
reduction in the work function of electrons at the collector,
the ability to select a hole semiconductor that is stable under TEC conditions for different temperature levels with optimization in the zone up to 1300 K at the emitter,
reduction of reverse emission from the collector surface,
no short circuit when touching the emitter and collector. 
Example of device implementation (see drawing). On the surface of the metal collector made of molybdenum 4 on the side of the interelectrode gap, a layer of diamond 3 is applied, doped with an acceptor impurity of boron up to 10 (20) at/cm3, which ensures that the Fermi level enters the valence band of the semiconductor. Emitter 1 is made of tungsten, thin layer 2 is made of a hole semiconductor. The interelectrode gap is made of cesium at a pressure of about 1 torr. Emitter temperature up to 2000 K, collector temperature up to 1000 K. The use of a diamond-based hole semiconductor is justified relative to others possible solutions its high stability at high temperatures. If the electrodes accidentally touch, there is no short circuit due to the lack of electronic conductivity in the hole semiconductor. Metal transfer from the emitter (or deposition of a layer during manufacturing) is limited by the Debye radius
An example of the implementation of a device with sodium (or cesium) beta-alumina. The device has a beta-alumina electrode coating according to the figure. Under conditions of excess oxygen and a lack of alkali metal, beta-alumina acquires the properties of a hole semiconductor. Operating temperatures for alumina are designed to be up to 1600 K. A film of beta-alumina 3 is deposited on the collector 4. In the interelectrode gap there is free oxygen and a small amount of alkali metal, but sufficient for the formation of a monolayer (film electrode) on the electrodes. Oxygen does not combine with sodium (cesium) at temperatures above 800 K, which will ensure that emitter 1 is covered with an alkali metal film. The absence of significant alkali metal vapor pressure in the TEC volume (very low alkali metal pressure, the area to the left of the minimum of the Paschen curve) is extremely important for operation powerful batteries TEC, since it will allow you to increase the operating voltage on the battery due to the high breakdown voltage at low alkali metal vapor pressure. Batteries with a power of more than 50 kW require a voltage of more than 100 V, which cannot be achieved in cesium vapor at a pressure of 1-3 torus; “dry electrical insulation” is required. The use of alumina and excess oxygen in the TEC makes the TEC insulation layer dry relative to the battery body. The presence of alkaline steam with a pressure of about torus in the TEC requires the introduction of a second layer of dry insulation and radically complicates the TEC battery.
Nuclear power plants.
Nuclear rocket engines
Nuclear power plants with thermoelectric generators
Since the early sixties, work on new methods of obtaining electrical energy and, in particular, work on the direct conversion of thermal energy into electrical energy based on thermoelectric and thermionic converters.
Interest in these works is due to the fact that such energy conversion methods fundamentally simplify the design of installations, eliminate intermediate stages of energy conversion and make it possible to create compact and lightweight energy installations.
At the same time, the use of nuclear power sources on spacecraft is associated with solving a large complex of safety problems. The first experience in solving these problems in our country was gained when launching spacecraft with radioisotope energy sources.
The development of radioisotope generators has been carried out in Russia since the early 60s. In September 1965, for the first time in Russia, radioisotope thermoelectric generators ( RTG) "Orion-1" with an electrical power of 20 W. The weight of the RTG was 14.8 kg, the design life was 4 months. RTG ampoules containing polonium-210 were designed in accordance with the principle of guaranteed integrity and tightness in all accidents. This principle was justified during launch vehicle accidents in 1969, when, despite the complete destruction of the objects, the fuel block containing 25,000 curies of polonium-210 remained sealed.
In subsequent years, work was carried out aimed at increasing the power and service life of RTGs for lunar rovers and deep space spacecraft. The developed RTG designs differed from each other in the isotopes used, thermoelectric materials, structural forms, etc. This significantly complicated and increased the cost of creating such power plants.
The relatively low energy intensity, high cost of RTGs, difficulties in solving the problems of using RTGs in space, and successes in the development of power plants based on a nuclear reactor caused the cessation of work on RTGs for space.
The use of thermoelectric and thermionic energy converters in combination with nuclear reactors has made it possible to create a fundamentally new type of installation in which the source of thermal energy - a nuclear reactor and the converter of thermal energy into electrical energy - are combined into a single unit - the reactor-converter.
To experimentally test the possibility of creating a small-sized converter reactor with direct conversion of thermal energy into electrical energy in the USSR, at the institute atomic energy named after I.V. Kurchatov, in collaboration with the Sukhumi Institute of Physics and Technology, the Kharkov Institute of Physics and Technology, and the Podolsk Scientific Research Technological Institute, the experimental installation “Romashka” was built in 1964 and underwent a full cycle of nuclear energy tests. This installation was a high-temperature fast neutron reactor-converter, in which the heat generated in the core was transferred due to the thermal conductivity of materials to a thermoelectric converter located on the outer surface of the reflector, which generated up to 500 W of electrical energy. Unused heat from the converter was radiated into the surrounding space by a finned radiator refrigerator. The Romashka converter reactor, brought to power on August 14, 1964, successfully operated for ~15,000 hours and generated 6,100 kWh of electricity.
The launch and successful testing of the Romashka installation demonstrated that the Soviet Union was the first in the world to create a working high-temperature nuclear reactor-converter, which makes it possible to directly generate electricity without the participation of any moving working bodies or mechanisms, and its ability to operate for a long time has been experimentally demonstrated. Subsequent cutting and study of the state of the elements of the Romashka installation showed that the achieved parameters and service life are not limiting and can be increased through some design improvements and, in particular, the use of flat modular thermionic elements instead of a thermoelectric energy converter located at the boundary of the core and radial reflector.
The completed set of works with the Romashka installation showed its absolute reliability and safety. However, due to the fact that by the time the tests were completed, the BES-5 nuclear power plant of much greater power had been created, further tests of the Romashka installation were stopped. On the basis of the "Romashka" installation, the "Gamma" pilot plant was created - a prototype of an autonomous transportable nuclear power plant "Elena" with an electrical power of up to 500 kW, intended for power supply to remote areas.
Nuclear power plant "BES-5".
Development of our country's first space nuclear power station"BES-5" with a homogeneous fast neutron reactor and a thermoelectric generator (TEG) was carried out in accordance with Resolutions of the CPSU Central Committee and the Council of Ministers of the USSR N 258-110 of March 16, 1961, N 702-295 of July 3, 1962 and N 651-244 dated 8/24/1965 by the cooperation of development organizations of the State Enterprise “Red Star”, State Scientific Center “IPPE”, Scientific and Technical Center “Istok”, Research Institute NPO “Luch”, Russian Scientific Center “Kurchatov Institute”, IPU RAS, etc. The station was developed to power the equipment radar reconnaissance spacecraft at the launch site and during the entire time of the active existence of the spacecraft in a circular orbit with an altitude of about 260 km. As a result of the calculation, design and experimental work done, by 1970, all the fundamental problems in creating the BES-5, generating an output power of 2800 W, with a resource of 1080 hours, had been practically solved.
In the period from 1963 to 1969, testing of the liquid metal circuit, testing of reactorless BES-5 samples with a TEG simulator and operating equipment, and testing of reactorless BES-5 with an operating TEG were carried out. In 1968-1970 full-scale life tests of space nuclear power plants "BES-5" No. 16, 25, 32 with an operating reactor were carried out at the Ts-14E stand. Tests of the N16 nuclear power plant (NPP) were successful, all tasks assigned to the tests were completed in full. The electrical power of the main section of the TEG during testing (1200 hours) decreased by 10% and at the end of the tests amounted to 905 W and 1040 W at temperature levels of 6900C and 7150C, respectively. The neutronic characteristics of the reactor, measured in stationary operating modes, were stable over time and satisfactorily coincided with the calculated values and values experimentally determined on physical assemblies at the Institute of Physics and Power Engineering.
Tests of the N25 nuclear power plant were stopped due to “boiling” of the primary coolant in the reactor zone due to insufficient pressure in the compensation tanks. After calibrating the autonomous neutron source using a newly developed technique using new high-precision equipment, the BES-5 tests were continued on the N32 installation. After successfully reaching the nominal operating mode of the BES-5 power plant N32, a full cycle of field tests was carried out at the stand Ts-14E (SE "Krasnaya Zvezda") in accordance with the program LKI NPP N31. Positive results tests made it possible on October 3, 1970 to launch the BES-5 N31 nuclear power plant as part of the radar reconnaissance spacecraft (Cosmos-367).
Nuclear power plant "BES-5" N 31 worked in orbit for 110 minutes and was put into a "burial" orbit due to the "overshoot" of the temperature of the 1st circuit above the maximum permissible, caused by the melting of the reactor core. Based on the results of the first launch, the sensors and operating logic of the temperature control channel were improved, and the “warm-up” power of the nuclear power plant was reduced from 150% to 115% Nnom.
As a result of bench tests and experimental tests, the following were developed:
Reliable technology for welding and subsequent control of the product, including thermal vacuum tests, which made it possible to ensure a service life of the product up to 1500 hours at design temperatures and ambient pressure 10-5 mmHg. and for 1300 hours when working in radiation fluxes exceeding natural ones;
Methodology for conducting simulation (without a reactor) thermal tests of a product in vacuum chambers;
Methodology for conducting ground tests of a product with a loaded core;
Methodology for conducting field tests.
After 9 launches of the BES-5 nuclear power plant, it was adopted by the USSR Navy in 1975. In total, by the time the BES-5 nuclear power plant was decommissioned (1989), 31 installations had been launched into space.
During the entire period of spacecraft launches with nuclear power plants on board, three most serious accidents occurred.
When launching a spacecraft with the BES-5 N51 nuclear power plant, due to the failure of the after-boost engine, the spacecraft was not launched into the intended orbit and the nuclear power plant with a deeply subcritical reactor fell into the Pacific Ocean.
The largest nuclear power plant accident occurred with the Kosmos-954 spacecraft, launched on September 18, 1977. Due to the depressurization of the instrument compartment of the spacecraft with the BES-5 N58 nuclear power plant on board and the failure of the differential pressure sensors of the secondary circuit, the equipment of the autonomous control system failed, which led to the loss of orientation of the spacecraft, the failure of the command to remove the nuclear power plant from the Earth and system failure automatic removal of nuclear power plants. As a result, the spacecraft with a nuclear power plant entered the atmosphere and disintegrated, scattering thousands of radioactive fragments over 100,000 km2 in the northwestern regions of Canada.
In 1983, due to the failure of the systems of the Cosmos-1402 spacecraft, launched on August 30, 1982, the nuclear power plant returned to the Earth’s atmosphere, which led to the activation of the backup radiation safety system of the nuclear power plant, dissipating the reactor core in the Earth’s atmosphere.
In April 1988, there was a loss of radio contact with Cosmos 1900, launched on December 12, 1987. The lack of communication prevented him from transmitting the command to remove the nuclear power plant, and until mid-September 1987, the spacecraft slowly lost altitude, gradually approaching the Earth. The US space control services were involved in monitoring the position of the spacecraft. Only on September 30, a few days before entering the dense layers of the atmosphere, the protective system was turned on and the satellite was taken into a safe stationary orbit.
During the operation of the installation, on the basis of Resolution of the Central Committee of the CPSU and the Council of Ministers of the USSR N 462-138 dated May 26, 1975, work was carried out to refine and modernize it, related to increasing radiation safety, increasing electrical power at the end of the resource up to 3 kW and increasing the resource up to 6-12 months.
Analysis of flight data showed that the termination of the operation of a spacecraft with a nuclear power plant on board occurred, as a rule, not through the fault of the power plant, with the exception of BES-5 NN 31, 60, 58, 75 and 76. Analysis of negative phenomena that occurred during operation on orbit of the nuclear power plant (failures of pressure and differential pressure sensors in the ZhMK "BES-5" N53 (15.5.1974, "Cosmos-651"), N60 (17.10.1976, "Cosmos-860"), N58 (18.09. 1977, "Cosmos-954"), as well as the reasons that caused them, led to the need for their modifications. Thus, starting with the BES-5 N58 nuclear power plant, improved actuators for driving compensating rods and anti-backlash springs were installed in the actuators. drive of the control rods, the gas pressure in the quenching unit (BG) of the reactor was increased from 760 to 1500 mm Hg. This made it possible to increase the reliability of the operation of the main radiation safety system of the nuclear power plant, significantly reduce reactivity disturbances caused by the operation of the engines of the spacecraft orientation and stabilization system, and reduce short-term ones. surges of current in the ionization chambers when the neutron power target is adjusted from 7.5% to 115%, as well as more reliably control the tightness of the BG during comprehensive checks on Earth (the pressure in the BG dropped to zero due to its leakage when the N52 nuclear power plant entered orbit (December 27. 1973, "Cosmos-626") and N56 (04/07/1975, "Cosmos-724"). In 1985, the operation of two spacecraft ended unexpectedly due to failures in the autonomous control system of the BES-5 nuclear power plant N75 and N76 due to more severe thermal regime operation of the EP-264 device. On the remaining copies of the nuclear power plant, the device was modified. After the incident with the Cosmos-954 spacecraft over Canada, work was intensified on on-board radiation safety systems, both the main one (OSRB), which ensures the “removal” of the nuclear power plant into a “burial” orbit at an altitude of 890 km, and the backup one (DSRB), based on the ejection bundles of fuel rods from the reactor vessel using a piston-type powder pressure accumulator and their subsequent aerodynamic destruction.
The performance of the on-board DSRB devices was confirmed in ground conditions and during the control flight tests of the N64 nuclear power plant, launched as part of the Cosmos-1176 spacecraft on April 29, 1980. All subsequent BES-5 nuclear power plants were equipped with DSRB.
In connection with the modernization of the radar reconnaissance spacecraft, the nuclear power plant was modified, characterized by an increased lifespan of up to 6 months. service life and electrical power at the end of life 2400 W. 3 copies were made. Nuclear Power Plant. The first launch of the modernized version of the nuclear power plant was carried out on March 14, 1988 as part of the Cosmos-1932 spacecraft. Despite the fact that the installation worked normally according to the flight program, further operation of the BES-5 nuclear power plant was discontinued. The remaining copy of the nuclear power plant was delivered from 5 NIIP to the Krasnaya Zvezda State Enterprise in 1993 and disposed of.
The decision to stop launching spacecraft with nuclear power plants on board was caused by the relatively low technical characteristics of nuclear power plants and the intensified opposition of the international community to the use of nuclear facilities in space.
Nuclear power plants with thermionic converters
Nuclear power plants "Topaz"
In parallel with the work on creating nuclear power plants with thermoelectric generators, work was carried out on nuclear power plants with thermionic converters that have higher technical characteristics.
The work was carried out by two cooperations of implementing organizations on two types of installations, differing:
The design of the main element of the nuclear power plant - the electricity generating channel (EGC);
The design of the working fluid (cesium) vapor generator. The Topaz-2 nuclear power plant uses a wick-type generator, which ensures constant flow regardless of the coolant temperature;
The Topaz-2 nuclear power plant is intended for use only in radiation-safe orbits and does not have a destruction system. It is not possible to modify it for a backup radiation safety system.
In the Topaz-1 (TEU-5) installation with a thermal reactor-converter and a liquid metal coolant (Na-K), there are 79 EGCs, each of which has 5 thermionic power generating elements (EGE) connected (multi-element EGC), and in the Topaz nuclear power plant -2" (Yenisei) - 37 EGCs, each of which has only one EGE (mono-element EGC).
The design of a single-element EGC makes it possible not to have interelectrode switching in the core, and also to remove gaseous fission products from the cathode volume, which determines their greater reliability and resource capacity; using thermal simulators, monitor the electrical characteristics of nuclear power plants before launch and before loading nuclear fuel; develop full-scale EGCs and thermionic converter reactor (TCR) conversion systems as a whole using electric heating, which reduces the cost and time spent on experimental work. However, the single-element design has a significant drawback, namely that, at the same electrical powers, the current at the output of a single-element EGC is 2-3 times greater than that of a multi-element one, and large electrode thicknesses are required to reduce ohmic losses. This disadvantage of a single-element EGC design is largely determined by the specific electrical power removed from the cathode surface, and in almost specific designs it begins to have a significant effect when the specific electrical power is above 2 W/cm2 for a TRP with a moderator and more than 5 W/cm2 for a TRP with fast neutrons. .
The Topaz-1 nuclear power plant was developed in accordance with the resolution of the Central Committee of the CPSU and the Council of Ministers of the USSR N 702-295 dated July 3, 1962 for radar reconnaissance spacecraft by a cooperation of organizations: the lead developer is the State Enterprise "Red Star", the scientific director is the State Scientific Center "PEI" , co-executors - Research Institute NPO "Luch" and others.
The Topaz-2 nuclear power plant was developed in accordance with the resolution of the Central Committee of the CPSU and the Council of Ministers of the USSR N 715-240 dated July 21, 1967 for a spacecraft system for direct television broadcasting from space by a cooperation of organizations: the lead developer is Energovak-TsKBM, the scientific director is RRC "Kurchatov Institute", co-executors - Research Institute NPO "Luch", etc.
During the development of the Topaz-1 nuclear power plant, a large complex of experimental studies was carried out on individual components, assemblies, thermophysical prototypes of the TRP and thermal simulators of the installation as a whole. More than 50 EGCs have been tested at the AM reactor at the State Research Center "PEI", which has shown their performance within a given resource. The longest duration of reactor tests of the standard design EGC (KET-49) was more than 5000 hours with an average specific power of 2.5 W/cm2 and a maximum cathode temperature of 16000C. The first full-scale ground-based power tests of the Topaz-1 nuclear power plant prototype were carried out at the stand of the State Research Center IPPE in 1970. The product was brought to an electrical power of 10 kW. The tests lasted 150 hours, after which they were suspended due to a leak of the liquid metal coolant. A total of 4 nuclear prototypes of the Topaz-1 nuclear power plant were tested.
The results of ground-based complex tests served as the basis for determining in the Decision of the Commission of the Presidium of the Council of Ministers of the USSR on ERW N 342 dated December 8, 1976, a possible date for conducting flight design tests in 1979-1980. Nuclear power plant "Topaz-1" as part of the experimental spacecraft "Plasma". However, the lack of a backup radiation safety system as part of the nuclear power plant led to the need to develop a new modification of the Plasma spacecraft - the Plasma-A spacecraft and to change, in accordance with the decision of the USSR Committee of Council of Ministers on ERW dated May 23, 1981, the terms and conditions of the LCT: carrying out LCT in a high radiation-safe orbit.
By decision of the State Commission under the Council of Ministers of the USSR on ERW No. 58 dated 02.12.1986, it was decided to conduct a flight test of the Plasma-A spacecraft with the Topaz-1 nuclear power plant. Two copies of the nuclear power plant (N22 and N23) were prepared for the LCT, differing in the material of the EGC cathodes: the cathodes of the N22 product are made of molybdenum, and N23 are made of molybdenum coated with tungsten.
Nuclear power plant N22 was launched into a radiation-safe stationary circular orbit at an altitude of 800 km on February 2, 1987 and operated in orbit as part of the Plasma-A (Cosmos-1818) spacecraft for 142 days. The correspondence of the characteristics of the nuclear power plant during a given three-month resource is shown.
Nuclear power plant N23 was launched into a radiation-safe stationary circular orbit at an altitude of 800 km on July 10, 1987 and operated in orbit as part of the Plasma-A spacecraft (Cosmos-1867) for 343 days. The compliance of the characteristics of the nuclear power plant during six months of operation is shown. Subsequently, over the next six months, the power of the nuclear power plant gradually decreased due to degradation processes in the RP, but was sufficient to power all spacecraft systems (at the end of stationary operation it amounted to 2.73 kW).
The cessation of operation of the nuclear power plant in both cases was caused mainly by the end of the reserves of the working fluid (cesium) and the release of hydrogen from the moderator cavity, which was a catalyst for degradation processes in the RP. Replacing a set of EGCs with emitter units made of monocrystalline molybdenum in NPP N22 with a set of EGCs with tungsten coatings in NPP N23 led to an increase in efficiency. Nuclear power plants by 1.05-1.07 times.
In parallel with the work on the Topaz-1 nuclear power plant, work was carried out to create the Topaz-2 nuclear power plant. During the work, more than 18 full-scale head units of the power plant were manufactured and tested, 7 of which (Ya-20, Ya-23, E-31, Ya-24, Ya-81, Ya-82, E-38) passed nuclear power tests . Lifetime nuclear power tests of the first prototypes (Ya-20, Ya-23, E-31, Ya-24) showed that the chosen design of the EGC does not meet the resource requirements. An increase in the diameter of the EGC cathodes was discovered due to swelling of the fuel cores under the influence of fission fragments, which led to short circuits of individual EGCs during testing and a drop in the total electrical power of the RP. It was also found that due to surface changes in the properties of the cathode-anode electrode pair and an increase in the reduced emissivity factor, the resource reduction in the electrical power of the EGC was 3% per 1000 hours.
To eliminate the listed design shortcomings, the Research Institute NPO "Luch" developed and tested an improved EGC, in which the following design and technological solutions were implemented:
New fixatives made of scandium oxide have been introduced into the MEZ, which are more resistant to cesium vapor compared to fixatives made of aluminum oxide;
The technology for applying tungsten coating to the emitter has been improved to prevent peeling of the coating (switching to chloride technology for applying a single-crystal coating);
The hole in the fuel has been enlarged to cover the entire length of the core and the diameter of the hole has been increased to reduce swelling of the fuel;
Increased MEZ;
A single crystal of molybdenum doped with niobium is introduced into the emitter.
During thermal tests with electric heating of one of the samples of the improved EGC, a service life of more than 22,500 hours was achieved.
In addition, in order to increase the operating life of the installation to 1.5 years, a new modernized reactor design was created with an increased number of EGCs in the core (from 31 to 37). 10 copies of the head blocks of such a nuclear power plant were manufactured (V-71 - for cold and dynamic tests with subsequent electrical power tests at the Baikal-1 complex stand; Ya-81, E-37, Ya-82 - for nuclear power plants lasting up to 1.5 years; E-39, E-40, E-41 - for LKI, E-38 - as a reserve; During testing of the Ya-24 sample, a lifespan of nuclear testing of a full-scale prototype of a space nuclear power plant, unprecedented in domestic and foreign practice, was achieved - 12,500 hours.
Due to the cessation of work on the spacecraft for which the Topaz-2 nuclear power plant was intended, work on the nuclear power plant was stopped at the stage of ground testing.
Russian-American cooperation on Topaz-type nuclear power plants.
A new stage in the activities of Russian organizations was Russian-American cooperation in the field of space nuclear energy.
The first official materials with brief information about the BES-5 power plant were transferred to the American side in connection with the incident with the Cosmos-954 satellite, which took place over Canada in 1978, then detailed information about the installation was transmitted during incidents with satellites. Cosmos-1402" in 1983 and "Cosmos-1900" in 1988.
Great interest among American specialists was aroused by the reports of Academician N.N. Ponomarev-Stepnov. and director of the State Enterprise "Red Star" Gryaznov G.M. on the results of tests of the Topaz nuclear power plant at an international symposium in Albuquerque (USA) in 1989. And in April 1989 at the IAE named after. I.V. Kurchatov held negotiations with representatives of Space Power Inc. (SPI) of Soviet developers of nuclear power plants (IAE named after I.V. Kurchatov, NPO "Red Star", TsKBM, NPO "Luch", IPPE). The negotiations concerned the possibility of cooperation in the field of space nuclear power plants for civil commercial applications and the use for these purposes of the experience and groundwork available in the USSR in the creation and full-scale testing of space thermionic nuclear power plants. During the negotiations, possible areas of civilian commercial use of such nuclear power plants as an alternative to solar power plants were discussed.
Materials transferred to the American side related to the successful tests in space of the Topol nuclear power plant (Topaz-1) in 1977-1978, as well as a visit by American specialists Russian companies convinced US specialists of Russia's undeniable priority in this area, and therefore a number of American companies showed interest in the scientific and commercial use for peaceful purposes of Russia's existing thermionic nuclear power plants.
In January-March 1991, a demonstration of the Topaz-2 nuclear power plant model (without nuclear fuel) was held at the VIII US Symposium on Space Nuclear Power (Albuquerque) and at the Soviet-American Scientific and Technical Symposium and Exhibition "Science- Cosmos-Conversion" at the University of Maryland. The demonstration caused big interest specialists and the public, is highly appreciated both in terms of the technological achievements of the USSR and the USSR’s readiness to participate in international cooperation in this area.
The main developers of the "Topaz-2" installation - TsKBM, RRC "KI" and Research Institute NPO "Luch" together with NIITP and GMP "NP Energotech" on the Russian side and International Scientific Products (ISP) on the American side, established a Russian-American joint venture "International Energy Technologies" (JV "INERTEC"). At the first stage of its activities, it was proposed to conduct demonstration tests in the United States on stands with electric heating of an experimental sample and components of the Topaz-2 installation without nuclear fuel. The Cabinet of Ministers of the USSR (N PP-15495 dated May 16, 1991) gave consent to conduct tests. The work was supported by special decisions of the US administration.
For testing, in the period 1991-1992, the American side was given two samples of the head unit of the Topaz-2 nuclear power plant - V-71 (working) and Ya-21U (reserve), previously tested in Russia, and the Baikal test bench.
The first stage of testing was carried out in November 1992 by the joint venture INERTEC under contract No. SP-1145/5474, concluded with ISP with the participation of specialists from the TSET (Termionic System Evaluation Test) group. At the Baikal stand in Albuquerque (USA), tests of the B-71 product were carried out in the scope of two complete test cycles “start-up-stop” in order to confirm the specified parameters. Tests of the installation sample and its separate EGC were completed in full and successfully: their performance was confirmed, the characteristics specified by the Test Program were obtained, and American personnel were trained. “The forecast of the obtained characteristics showed that under normal conditions the Topaz-2 installation with the characteristics of B-71 can provide electrical power at the terminals of the working section of the reactor of 4.5-6.0 kW at a coolant temperature at the reactor outlet of up to 5700C” ( from the test report).
The purpose of the second stage of testing was to obtain experimental information on the Topaz-2 installation as a control object and a source of electricity during tests with electric heating in a vacuum chamber and to train American specialists. The tests are carried out by the TSET group with the participation of Russian specialists, American and Russian researchers.
After the successful completion of the first stage of work, the American side proposed preparing flight demonstration tests of the Topaz-2 installation together with an electric propulsion module based on various types of electric propulsion engines on a US spacecraft and signed a contract for the participation of Russian enterprises in the development of space nuclear thermionic installations with increased ( up to 40 kW) electrical power. The operation of nuclear power plants must be carried out in high orbits, where radiation safety for the Earth's population is fully guaranteed. Funding for this work will be provided by the American side from government sources.
To conduct flight tests of the Topaz-2 installation as part of the American spacecraft, the developers of the installation in 1994-1995. delivered to the USA four experimental samples of the Topaz-2 installation (of which samples E-43, E-44 - for flight tests and E-40, E-41 for testing docking with the spacecraft). In addition, it is planned to use two experimental models of the Topaz-2 installation, previously delivered to the United States, for ground tests. The use of Topaz-2 installations for flight tests is planned under the conditions of return (except for those launched into space) of Topaz-2 installations after the completion of the program to Russia without dismantling and excluding direct use of the installations for military purposes.
Despite the fact that, due to a sharp reduction in funding for work in the field of space nuclear power, R&D work on the creation of nuclear power plants was stopped, the activities of development organizations since 1992 are aimed mainly at preserving the achieved scientific and technical groundwork, test bench base and carrying out work on testing of the main elements of nuclear power plants. At the same time, the positive test results of the Topaz-1 and Topaz-2 nuclear power plants proved the fundamental possibility of creating energy systems in space with a power of 10-100 or more kilowatts and laid the foundation for the development of projects for a number of thermionic installations with a power of 10-15, 25, 50 and 100-150 kW.
Space nuclear power plant projects
During the creation of the BES and Topaz nuclear power plants, a number of plant designs with improved characteristics were prepared on their basis.
The preliminary design for a modified Topaz-1 nuclear power plant was developed by the Krasnaya Zvezda State Enterprise in accordance with the Decree of the USSR Council of Ministers on ERW N 223 dated August 21, 1974. This installation was an accelerated version of the Topaz-1 nuclear power plant. The increase in power was achieved through the introduction of one additional EGC, the use of an induction electromagnetic pump instead of a conduction pump, and the introduction of security electrodes into the EGC. The installation, unlike the Topaz-1 nuclear power plant, was equipped with a redundant safety system, a refrigerator-radiator on heat pipes, a closed cesium system with cesium regeneration, and an optimized electrical switching circuit.
Based on the developments of the Romashka reactor, in 1976 Energovak-TsKBM prepared technical proposals for the Zarya-1 thermoelectric nuclear power plant for optical-electronic reconnaissance (OER) spacecraft. The Zarya-1 nuclear power plant differs from the BES in the level of electrical power (5.8 kW versus 2.9 kW) and increased service life (4320 hours versus 1100 hours).
The scientific and technical groundwork in terms of creating TEG and TEP for reactor nuclear power plants made it possible to develop in 1978 a preliminary design of two versions of the Zarya-2 nuclear power plant for the OER spacecraft with an electrical power of 24 kW and a service life of 10,000 hours. The inclusion of a thermoelectric generator in the FMC of the thermionic nuclear power plant of the Topaz-1 type made it possible to solve the problem of quickly (10 minutes after the command to launch the nuclear power plant) providing electricity to the spacecraft equipment and the installation’s own needs in comparison with the time the Topaz-1 nuclear power plant reached the nominal mode electrical power (after 60 minutes). At the same time, this solution made it possible to reduce the required capacity of the batteries, an acute shortage of which was felt during the creation of Topaz-1. A distinctive feature of the second version of the Zarya-2 nuclear power plant is that the high output power is ensured by the use of forced EGCs with a guard electrode.
In 1978, the Krasnaya Zvezda State Enterprise developed technical proposals for 2 versions of the Zarya-3 space nuclear power propulsion system with an electrical power of 24.4 kW and a service life of 1.15 years. It was intended, among other alternative options, to create thrust impulses for correcting the orbit of the OER spacecraft and power supply for special equipment. The first option is a modification of the Topaz-1 nuclear power plant in terms of the use of a built-in RP and EGC (similar to the RP of the Zarya-2 installation) and an autonomous liquid propellant rocket engine. Another option was fundamentally different from the Topaz-1 nuclear power plant in the presence of a fast neutron reactor, carried out by TEC with heat pipes and liquid propellant engines, and the fuel rods and TEPs were combined into steam-electric generating channels.
Work on the Topaz and Zarya installations was stopped due to the lack of their connection to a specific spacecraft.
In the period 1981-1986. In Russia, a large amount of design and experimental work was carried out, indicating the fundamental possibility of increasing the resource of nuclear power plants to 3-5 years and electrical power to 600 kW.
As a result of these studies, a standard-size range of thermionic RPs was developed based on the EGC prototype of the EGC NPP "Topaz-1" with a power of 10-15, 25, 50 and 100-150 kW. Development of nuclear power plants of the "Acacia" type and the nuclear electric rocket engine "Hercules"
THERMAL EMISSION CONVERTERS - THE WAY TO THE ENERGY INDUSTRY OF THE FUTURE
The information agency “GATEWAY-YEKATERINBURG” disseminated information about the creation of a thermionic converter of thermal energy into electrical energy (TEC) with a very high conversion coefficient (CT) - up to 80-82%. At first, this seemed unlikely to me, but after ordering a technical description of the converter from the developers and reading it, the author concluded that it is quite possible to achieve such a CP in practice, and as part of a unit, the CP can reach a value of 95-97%.
Based on the above, I would like to speculate in this article about promising schemes for the use of TEC in traditional and non-traditional energy.
With the current traditional energy supply scheme, several types of energy are supplied to each residential property: electricity, heat, network gas, hot water.
By placing a TEP-based micro-CHP at every residential property, we will move on to a progressive scheme of decentralized energy supply with a high CIT. This scheme works as follows: network gas enters the micro-CHP, where it is burned in an external furnace. Gases heated in the furnace to a temperature of 1650-1700 o C enter the TEP, where direct conversion of thermal energy into electrical energy (constant voltage) occurs. Next, the gases, cooled to a temperature of 250-300 o C, enter the heat exchanger, where cold tap water is heated for the hot water supply of the facility. At the same time, 70-75% of gas energy is spent on generating electricity and 25-20% on producing hot water. The main part of direct voltage electricity is spent on heating the facility, lighting, electric stoves, some household appliances operating on direct current (for example, refrigerators), part of it, having passed through an autonomous inverter, and, having received the parameters of a standard network, is spent on household appliances operating on alternating current. In the future, the whole household appliances can be switched to DC power, which will significantly reduce the harmful effects of electromagnetic radiation on humans. To increase the reliability of energy supply, it is necessary to have a supply of liquid fuel or a gas tank with liquefied gas. By removing gas pipelines and gas stoves from apartments and placing a micro-CHP on the roof of a building, you can dramatically increase the safety of using network gas.
Installing rooftop micro-CHPs at residential properties will allow them to supply only one type of energy carrier - network natural gas (in the future - hydrogen), and the money saved can be invested in the manufacture of gas pipelines from modern high-strength composite materials.
Now let's talk a little about the economics of this proposal.
Specific capital costs for an autonomous energy supply SYSTEM for a residential facility, including TEP, heat exchanger, inverter, emergency fuel supply system, electric heating system, etc. According to rough calculations, will be about
10,000 rub/kW. The average selling price for electricity will be about 15 kopecks/kWh.
Specific capital costs for a centralized energy supply SYSTEM for a residential facility, including a centralized source of thermal energy and hot water, heating mains, power generating and transforming facilities, power lines, etc. according to some sources, according to the most conservative estimates, about 15,000 rubles/kW. The payment for electricity for the population already ranges from 30 to 60 kopecks per kWh, while this money does not cover not only the full selling price, but even the cost only partially.
Installation of similar autonomous systems energy supply at industrial facilities also promises significant benefits.
If we leave the traditional water heating system at residential and industrial facilities, and install hydrodynamic energy converters with a conversion coefficient of 300% or higher in micro-CHPs based on thermal power plants, this will reduce fuel costs for heating needs by 2-2.5 times and in general gas consumption for energy needs is 3.5-4 times.
This, in turn, increases the period of depletion of natural gas reserves by tens of years, which gives an additional time head start to scientific minds for the development of highly efficient non-traditional energy converters (sun, physical vacuum, etc.).
Now let’s talk about the use of TEC in non-traditional energy, or more precisely in solar energy.
A modern solar power plant should be located in an area with maximum solar energy arrival in terms of time and power. It converts solar energy into electrical energy, with the help of which hydrogen is obtained from water and transmitted through a pipeline system to consumers. Transferring energy in the form of hydrogen rather than electricity becomes more profitable at distances exceeding 500-600 km.
A solar power plant consists of a large number of energy modules, each of which consists of a conversion module, an electrolyser and auxiliary equipment. Since each energy module has a complete hydrogen production cycle and small price, then the construction of such a station can begin with small investments, gradually increasing its productivity.
Each conversion module mainly consists of solar collector(TVVC) with parabolic-cylindrical concentrators, a thermionic converter (TEC) and a circulation fan. The conversion coefficient of such a module can reach 70-75%. The thermal coefficient of modern electrolysers reaches 95%, i.e. the overall efficiency of the energy module can reach 70%.
If we compare the performance of a solar power station based on TEC and TVVC with the performance of a solar power station based on silicon batteries, the following will be revealed: the specific capital costs of the first station are an order of magnitude lower than those of the second; The area of land occupied by the first station is 5-6 times less than the second.
Since solar power plants have an unstable operating cycle, the question naturally arises about some method of accumulating hydrogen to ensure consumer operation at night and when it is cloudy on the territory of the power station. Now scientists and engineers are actively developing various types of hydrogen batteries. I would like to draw your attention to the following: when transferring energy in the form of hydrogen, pipelines of large cross-section and long length will be used. The network of these pipelines can be used to store hydrogen. Thus, a pipeline with an internal diameter of 1000 mm and a length of 1500 km at a pressure of 75 atm contains about 8,000 tons of hydrogen, which can ensure the operation of energy facilities using thermal power plants with a total capacity of about 8 GW within 24 hours.
Based on the fact that modern electrolysers allow the production of hydrogen at sufficient high pressures(up to 100 atm), then the need for gas compressors at the beginning of the gas pipeline disappears. Metal hydride thermosorption compressors (MTSC) can be recommended as main booster compressor stations. Their work is based on the ability of metal hydrides to absorb hydrogen at low temperatures, and at moderately high temperatures to release hydrogen at significant pressures. For example, at a pressure of 3 atm and room temperature, misch metal absorbs hydrogen quite quickly, and when heated to a temperature of 250-260 o C, hydrogen can be released already at a pressure of about 100 atm. MTSK are static devices, they have no moving parts, they are completely sealed, which ensures their high safety, reliability and efficiency.
For some US states, the average annual solar energy output per square meter is 1500 kWh, i.e. A solar power plant with an active area of 10 square kilometers and CP = 70% can generate 10.5 * 10 9 kWh of electricity or about 2.1 million tons of hydrogen per year. For the United States, the ideal location for a solar power plant would be the so-called “valley of death” (360 days a year – sunny).
For central Russia, the average annual arrival of solar radiant energy per square meter, according to some data, is 500 kWh, i.e. the same station can generate 3.5 * 10 9 kWh of electricity or about 0.7 million tons of hydrogen per year. For comparison, electricity generation in 2000 by JSC Kirovenergo was 3.56*10 9 kWh, JSC Omskenergo - 6.198*10 9, JSC Ivenergo - 1.352*10 9.
Further, hydrogen produced at solar power plants can be supplied through a pipeline system to consumers, who can use it to generate electricity in thermal power plants, or directly - in chemical processes
And in conclusion about possible financing of this project. The first, state-owned, is through the sale of part of the quotas for CO 2 emissions into the atmosphere (recently, due to a decrease in production volumes, Russia, according to the Kyoto Protocol, has not used these quotas in full).
The second one is private. At the first stage of the project (production of small energy systems for individual use), a competent investor, even without drawing up a detailed economic justification, can see the high profitability of this production.
I would like to have a modest hope that Russia (including private business) will not step on the same rake again - it will find a way to finance this project in the required amount and will not once again force developers to sell this technology to already developed countries, after which it will be forced to buy equipment using this technology in these countries at exorbitant prices.
Basic methods and methods of converting electrical energy into heat classified as follows. A distinction is made between direct and indirect electrical heating.
At direct electric heating the conversion of electrical energy into thermal energy occurs as a result of the passage of electric current directly through a heated body or medium (metal, water, milk, soil, etc.). At indirect electric heating An electric current passes through a special heating device (heating element), from which heat is transferred to the heated body or medium through thermal conductivity, convection or radiation.
There are several types of conversion of electrical energy into thermal energy, which determine ways electric heating.
The flow of electric current through electrically conductive solids or liquid media is accompanied by the release of heat. According to the Joule-Lenz law, the amount of heat is Q=I 2 Rt, where Q is the amount of heat, J; I - silatok, A; R - body or medium resistance, Ohm; t - current flow time, s.
Resistance heating can be carried out by contact and electrode methods.
Contact method used for heating metals both by the principle of direct electric heating, for example in electric contact welding machines, and by the principle of indirect electric heating - in heating elements.
Electrode method used for heating non-metallic conductive materials and media: water, milk, succulent feed, soil, etc. The heated material or medium is placed between the electrodes, to which an alternating voltage is applied.
Electric current flowing through the material between the electrodes heats it. Ordinary (non-distilled) water conducts electric current, since it always contains a certain amount of salts, alkalis or acids, which dissociate into ions that are carriers of electrical charges, that is, electric current. The nature of the electrical conductivity of milk and other liquids, soil, succulent feed, etc. is similar.
Direct electrode heating is carried out only with alternating current, since direct current causes electrolysis of the heated material and its deterioration.
Electric heating by resistance found wide application in production due to its simplicity, reliability, versatility and low cost of heating devices.
Electric arc heating
IN electric arc occurring between two electrodes in a gaseous medium, electrical energy is converted into thermal energy.
To start the arc, the electrodes connected to the power source are touched momentarily and then slowly pulled apart. The contact resistance at the moment of spreading the electrodes is strongly heated by the current passing through it. Free electrons, constantly moving in the metal, accelerate their movement with increasing temperature at the point of contact of the electrodes.
As the temperature rises, the speed of free electrons increases so much that they break away from the metal of the electrodes and fly into the air. As they move, they collide with air molecules and split them into positively and negatively charged ions. The air space between the electrodes is ionized, which becomes electrically conductive.
Under the influence of the source voltage, positive ions rush to the negative pole (cathode), and negative ions to the positive pole (anode), thereby forming a long discharge - an electric arc, accompanied by the release of heat. The temperature of the arc is not the same in its different parts and for metal electrodes is: at the cathode - about 2400 °C, at the anode - about 2600 °C, in the center of the arc - about 6000 - 7000 °C.
There are direct and indirect electric arc heating. Basics practical use finds direct electric arc heating in electric arc welding installations. In indirect heating installations, the arc is used as powerful source infrared rays.
If a piece of metal is placed in an alternating magnetic field, then a variable e will be induced in it. d.s, under the influence of which eddy currents will arise in the metal. The passage of these currents in the metal will cause it to heat up. This method of heating metal is called induction. The device of some induction heaters based on the use of the phenomenon of surface effect and proximity effect.
For induction heating, industrial (50 Hz) and high frequency currents (8-10 kHz, 70-500 kHz) are used. Induction heating of metal bodies (parts, workpieces) is most widespread in mechanical engineering and equipment repair, as well as for hardening metal parts. The induction method can also be used to heat water, soil, concrete and pasteurize milk.
Dielectric heating
The physical essence of dielectric heating is as follows. IN solids and liquid media with poor electrical conductivity (dielectrics) placed in a rapidly varying electric field, electrical energy is converted into thermal energy.
Any dielectric contains electric charges connected by intermolecular forces. These charges are called bound in contrast to free charges in conductive materials. Under the influence of an electric field, bound charges are oriented or displaced in the direction of the field. The displacement of bound charges under the influence of an external electric field is called polarization.
In an alternating electric field, there is a continuous movement of charges, and, consequently, of molecules associated with them by intermolecular forces. The energy expended by the source to polarize the molecules of nonconducting materials is released in the form of heat. Some non-conducting materials contain a small amount of free charges, which under the influence of an electric field create a small conduction current, which contributes to the release of additional heat in the material.
During dielectric heating, the material to be heated is placed between metal electrodes - capacitor plates, to which a high frequency voltage (0.5 - 20 MHz and higher) is supplied from a special high-frequency generator. The installation for dielectric heating consists of a high-frequency tube generator, a power transformer and drying device with electrodes.
High-frequency dielectric heating is a promising heating method and is mainly used for drying and heat treatment of wood, paper, food and feed (drying grain, vegetables and fruits), pasteurization and sterilization of milk, etc.
Electron beam (electronic) heating
When a flow of electrons (electron beam), accelerated in an electric field, meets a heated body, electrical energy is converted into thermal energy. A feature of electronic heating is its high energy concentration density, amounting to 5x10 8 kW/cm2, which is several thousand times higher than with electric arc heating. Electronic heating is used in industry for welding very small parts and smelting ultra-pure metals.
In addition to the considered methods of electric heating, it is also used in production and everyday life. infrared heating(irradiation).
As you know, all bodies consist of molecules, and these molecules are not at rest, but are constantly moving. The higher the temperature of a body, the faster the movement of the molecules of the substance of this body. When electric current passes through a conductor, electrons collide with the moving molecules of the conductor and increase their movement, which leads to heating of the conductor.
An increase in the temperature of the conductor occurs as a result of the conversion of electrical energy into thermal energy. Previously (see § 13) an expression was obtained for the work of electric current (electric energy)
A = I 2 rt joules.
This dependence was initially (in 1841) established as a result of experiments by the English physicist Joule and somewhat later (in 1844) independently by the Russian academician Lenz.
In order for the amount of thermal energy received to be expressed in calories, it is necessary to additionally enter a factor of 0.24, since 1 J = 0.24 cal. Then Q = 0.24I 2 rt. This equation expresses the Joule-Lenz law.
Emilius Christianovich Lenz (1804-1865) established the laws of the thermal action of current, generalized experiments on electromagnetic induction, presenting this generalization in the form of the “Lenz rule”. In his works on the theory of electrical machines, Lenz described the phenomenon of "armature reaction" in machines direct current, proved the principle of reversibility of electric machines. Lenz, working with Jacobi, studied the force of attraction of electromagnets and established the dependence of the magnetic moment on the magnetizing force.
Thus, the amount of heat generated by the current when passing through a conductor depends on the resistance r of the conductor itself, the square of the current I 2 and the duration of its passage t.
Example 1. Determine how much heat a current of 6 A will generate when passing through a conductor with a resistance of 2 ohms for 3 minutes.
Q = I 2 rt = 36 ⋅ 2 ⋅ 180 = 12960 J.
The formula for the Joule-Lenz law can be written as follows.
I suggest in this topic to find the most best option homemade device, to convert heat into electrical energy.
From my experience I will say the following:
There are 3 main options:
1. Steam piston engine
2. Steam turbine
3. Stirling
4. Peltier modulesHaving sifted through a lot of material and watched a lot of homemade videos from YouTube, I came to the conclusion that the most optimal, and with a long service life, are converters based on the basics of serial Peltier modules.
(although I used to have a different opinion and said that all these were the machinations of the world’s oil conspirators)I'll keep it short:
1. Can be made from a production engine by modifying the camshaft of the intake and exhaust valves. It's not difficult to get high power. There are problems with lubrication.
2. A steam turbine, better and easier to manufacture than a piston engine, has a longer service life, and repairs consist mainly of replacing bearings. It can be made from a serial automobile turbine, or a Tesla turbine can be machined. I saw it on YouTube homemade installations with a power of about 1 kilowatt already at the output of the generator. It’s clear that for such a power of steam, the turbine needs much more steam than what comes from the kettle.
****
In general for steam installations:
A steam boiler is very explosive. But you can make a steam generator using tubes, then it’s not so dangerous. There are difficulties with recirculation; you need a radiator or heat exchanger for the heating system of the house and a pump pumping cooled steam or already water into the evaporator for steam generation. It’s not entirely clear where to get this pump, because... it must pump return flow into the steam generator under high pressure; in turbines a small centrifugal one is installed on the shaft.The heat source itself for the steam generator must be adjustable, its power must be within the specified limits, and it is clear that waste heat less than 100C cannot be used. Needs constant monitoring technical condition steam generator so that it is not “gobbled up” by corrosion, so that the tube with superheated steam does not get torn off anywhere, come up with protection, etc....
****3. Stirling, I’m still finalizing it, despite its simplicity, and a bunch of revised can engines, assembled in a couple of hours, on YouTube.
I’ll tell you from my own experience - doing Stirling is a thankless task. It turned out to be SO difficult to make this engine practical, a lot of material is wasted, serial parts from different mechanisms are not so suitable... There are problems with its tightness, because... I don’t make a thing so that it rotates beautifully for a couple of hours and then breaks all the bushings. In short, it is difficult and difficult.
Of the ready-made Stirling generators that I found on the Internet, I saw devices that were quite large and difficult to manufacture, with a large number of rubbing elements (and therefore short-lived). Their power was about
0.045 - 2 cotton wool!, and the size turned out to be half the system unit (it depends on who). Those. it is difficult and ineffective. Low-calorie heat can be utilized from +owls, it can be made from tin cans, a balloon, and show the children, there are many options for execution. Well, not as dangerous as steam installations, although under high pressure and temperature the lubricant can explode (detonate), this also needs to be taken into account.4. Peltier. It is easy to make a ThermoElectric Generator based on them, i.e. we put it on radiators, or whatever, and remove the electricity. With smooth temperature increases and compliance with temperature conditions, I consider the resource of this type of converters to be the longest among the listed installations. Low-calorie heat can be recovered. According to videos from YouTube, Peltiers are clearly superior to homemade sterlings in terms of power. But they are far from steam turbines; for 1 kW the unit will turn out to be quite impressive in size and price.
The most important thing is that you don’t need to look at cryotherm’s websites, they charge prices just like non-native ones, sometimes I think that they even slyly put their branded stickers on Chinese modules. In short, for example, in our Ukraine, the Chinese TEC1-12710 module costs 70g (about 9 dollars), I actually saw these same modules on Ebay for 1 buck, but I still didn’t understand how to pay for them, if they died, tell me, who knows and actually bought them on the Internet, please. In short, 70 grams each, from us, I’ve already ordered a couple, they’ll deliver them after New Year’s Eve, I’ll experiment.
The conversion of electrical energy into heat or electric heating has four main types, according to which industrial electric furnaces are classified; 1) electric heating through resistance; 2) arc electric heating; 3) mixed electric heating; 4) induction heating.
Electric heating of metallurgical furnaces has significant advantages compared to heating as a result of combustion of carbonaceous fuel: the ability to obtain very high temperatures of up to 3000°C or more with the concentration of high temperature zones in certain areas of the working space of the furnaces; ease and smoothness of regulation of the value and distribution of temperature in the working space; cleanliness of the working space and the ability to avoid contamination with ash, sulfur, gases and various impurities: low loss of metals with slag, dust, gases and fumes; high thermal efficiency, reaching 70-85%; small amount of gases and dust; possibility of complex mechanization and automation; culture and cleanliness of workplaces; the ability to use any gas environment and vacuum.
The disadvantages of electric heating include: high electricity consumption, which significantly exceeds consumption in other sectors of the national economy, and design limitations of productivity and power for some types of electric furnaces. in the future, due to an increase in the capacity and number of power plants, a decrease in the cost of electricity and an increase in the power and productivity of electric furnaces, the listed disadvantages will lose their significance.
The total active or watt power of a three-phase electric furnace installation P is determined by the formula
Electric heating through resistance
This type of electric heating has several varieties. Based on the method of heat generation, a distinction is made between indirect and direct heating; highest value and indirect heating is widespread in furnace technology, characterized by the fact that heat is released in special heating elements (resistances) and is transferred from them to the material being processed by heat transfer. Based on the temperature of the furnace working space, heating is distinguished; low temperature in the range of 100-700°, medium temperature 700-1200° and high temperature 1200-2000°.
With low-temperature heating, the heat exchange between the heater and the material by convection, which is intensified in every possible way by forced circulation at high speeds of gas or air inside the liver, is very important. With medium and high temperature heating, especially in the absence forced circulation gases, the main amount of heat is transferred from heaters to the materials being processed by radiation. For electric resistance furnaces, high temperature heating is of only limited importance.
Electrical resistance heating has found its greatest application for drying and firing materials, heating and heat treatment of metals and alloys, melting low-melting metals - tin, lead, zinc, aluminum, magnesium and their alloys, as well as for laboratory and household needs. Since, however, when indirect heating the size of the heating elements increases, and their placement in the working space of the furnace turns out to be difficult; the upper limit of the power of electric resistance furnaces is limited to 600-2000 kW.
For the normal process of converting electrical energy into heat and long-term stable operation, heating elements must have the following qualities: high electrical resistivity, allowing sufficient cross section elements and their limited length; small electrical temperature coefficient, limiting the difference in electrical resistance of the heated and cold heater, constancy electrical properties in time; heat resistance and non-oxidation; heat resistance, i.e. sufficient mechanical strength at high temperatures; constancy of linear dimensions; good workability of the material (weldability, ductility, etc.). These requirements are best met by alloys of nickel, chromium, iron (nichrome, fechral and heat-resistant steel), used in resistance electric furnaces in the form of wire or tape, and carbon materials used in the form of carbon, graphite or carborundum rods.
The determination of the dimensions of heating elements can be scientifically justified by the joint solution of two basic equations that describe the essence of the work of heaters - the power equation and the heat transfer equation. Since the heating element is integral part electrical purpose, then to obtain required power it must have certain dimensions and resistance. On the other hand, all the thermal energy obtained in the heating element as a result of the conversion of electricity must be transferred by heat transfer to the processed materials and the furnace lining, for which it is necessary to have a certain surface, temperature and heat transfer coefficient. If the heat transfer of the heating element does not correspond to the heat release occurring in it, the element will overheat, and its temperature may exceed the permissible limits for the material, which will lead to destruction of the heater.
Based on the solution of the power equation for heating elements of any shape and material, a general formula is derived
When calculating the dimensions of the heater, the value of w must exactly correspond to its specific heat transfer, which is found by solving the corresponding heat transfer equation of the heater, masonry and material A.D. Svenchansky analyzed the heat transfer conditions for various real heaters and compiled graphs and tables with which you can find the value of w.
Electric arc heating
This type of electric heating is used in high temperature electric ovens high power mainly for melting various materials. If an arc burns between the electrode and the material processed in the furnace, then such furnaces are called direct-action furnaces with a dependent arc: open - visible (Fig. 20, a) or closed - invisible arc immersed in a layer of charge or melt (Fig. 20, b ). If the arc burns between the electrodes and does not directly come into contact with the materials and products processed in the furnace, then such furnaces are called indirect furnaces with an independent arc (Fig. 20, c). Direct arc furnaces have the highest thermal efficiency, especially with a closed arc, since they have the best conditions for heat exchange between the arc and the material, allowing the material to be heated quickly and with limited heat losses to very high temperatures. high temperature.
Direct arc furnaces are most widely used for the smelting of steel and ferroalloys, smelting and refining of copper and nickel and processing of various ore raw materials. When melting metals or alloys with high (metallic) electrical conductivity, you can only work with an open arc burning on the surface of the material, since immersing the electrodes in the material layer will lead to a short circuit. Closed arc operation is possible when the materials and products being processed have limited (non-metallic) electrical conductivity. Indirect arc furnaces are used in cases where the contact of the processed material with the arc deteriorates the quality of the products or increases losses, for example, when melting some non-ferrous metals and alloys (brass, bronze, etc.). It should be especially emphasized that electric arc heating, unlike resistance heating, does not have any restrictions on the total power of the furnaces.
Electric arc heating consists of the process of converting electricity into heat, which occurs in a burning arc, and the process of heat exchange between the arc, the material and the lining. The description of the laws of the first process is the subject of the so-called theory of the arc and especially the arc alternating current high power. A significant contribution to the development of arc theory was made by V.V. Petrov, V.F. Mitkevich, S.I. Telny, I.T. Zherdev, K.K. Khrenov, G.A. Sisoyan and others. The issues of heat exchange between the arc, material and lining were dealt with by D.A. Diomidovsky, N.V. Okorokov and others.
An electric arc can be produced using direct or alternating current, but all industrial furnaces usually operate on alternating current. For stable arc burning and limiting current surges during short circuits in series with it in electrical circuit an inductive reactance is switched on, absorbing a small fraction of the active power. With alternating current, during each half-cycle the network voltage and current reach a maximum and pass through zero. In Fig. 21, a shows the theoretical curves of the instantaneous value of the current and arc voltage Id and Ud and the supply voltage Uist. When the source voltage begins to increase after crossing zero, the arc is ignited only when the ignition voltage U1 is reached. From this moment, a current appears in the circuit, increasing along a periodic curve that is different from a sinusoid. The arc extinguishes at the attenuation voltage, i.e., before the source voltage crosses zero, and at this moment the current stops. After crossing zero, all the described phenomena are repeated. Thus, the current in the arc flows intermittently and the arc either lights up or goes out. The duration of interruptions in arc burning depends on many factors and, in particular, on the material of the electrodes, the degree of heating of the furnace space, etc. It is clear that an intermittent arc reduces the efficiency of arc heating and therefore conditions must be created that ensure continuous burning AC arcs. The main means for continuous burning of an alternating current arc is the sequential inclusion of inductive reactance in the arc circuit, as can be seen from Fig. 21, b and c.
The study of the differential equation of an alternating current arc, which has active and inductive resistance in the circuit, determined the ratio of the values of inductive X and active R resistance, ensuring continuous arcing at given source voltages Uist and arc Ud (Fig. 22).
The efficiency of arc heating depends to a very large extent on electric mode burning arc and, first of all, on voltage and current values.
At present, a scientifically based method for determining the most advantageous voltage for powering arc furnaces has not yet been created. Therefore, the voltage is selected according to factory practice in the range from 100 to 600 V, with higher voltages usually adopted for high-power arc furnaces and for furnaces with a closed arc. The relationship between the maximum operating voltage Uline and the rated power of the furnace Pnom is usually expressed by the empirical formula
where k and n are empirical coefficients that have different values depending on the type of furnace and the nature of the process. For example, for arc steel-smelting furnaces k = 15; n = 0.33. Working at a higher voltage is more rational, as it reduces electricity losses and increases the length and thermal radiation of the arc. The upper voltage limit (600 V) is mainly determined by the conditions of electrical insulation of the furnace and the safety of operating personnel.
After determining the voltage value, the choice of other indicators of the electrical mode of an electric furnace installation with arc heating - optimal current strength, cos φ and efficiency - is made according to its operating characteristics. The performance characteristics of arc furnaces are determined by constructing pie charts: for existing factory furnaces they are taken from nature, for newly designed furnaces - according to calculated data.
For the theory of arc heating and the calculation of arc furnaces, the process of heat exchange between the burning arc and the materials processed in the furnace is of great importance. However, the theory of heat transfer in the working space of arc furnaces is still in its infancy. initial stage its development and requires further in-depth development.
Mixed electric heating
This type of heating, which is the result of combined heat release in an electric arc and in the resistance of a layer of charge or melts, is of primary importance for ore-thermal furnaces that smelt ferroalloys, cast iron and process ore raw materials and intermediate products of non-ferrous metallurgy and the chemical industry.
in the most complex case, the electric current passing through the arc and layers of charge, slag and metal is converted into thermal energy Qarc, Qcharge, Qslag, Qmetal, furnace Рtotal represents the sum of the listed heat releases. The principle diagram for calculating all these heat releases and their connection with the geometry of the hearth of ore-thermal furnaces was at one time illuminated by the author, but for an accurate calculation of heat releases there is still a lot of data missing thermal characteristics arc, electrical resistance of the charge and melts, shape and size of conductive sections, etc. Accordingly, the method proposed by the author for calculating ore-thermal electric furnaces is still indicative in nature and has limited application.
For non-ferrous metallurgy, ore-thermal furnaces operating with electrodes immersed in thick layer slag, in which mixed electric heating occurs, consisting of two main components: Qarc and Qslag.
M.S. Maksimenko proposed dividing all electrothermal processes into two main groups; 1) processes in which the fraction of energy absorbed in the arc p is greater than the fraction of energy absorbed in the charge and melts 2) processes in which p
Induction electric heating
Induction electric heating is carried out according to the principle of a transformer, in which the secondary winding is short-circuited. itself, as a result of which the induced electric current is converted into thermal energy. The role of the secondary winding is usually played by the heated material itself. Electrical energy supplied to the primary winding (inductor) makes a complex transition into the energy of a rapidly varying magnetic field, which, in turn, is again converted into electrical energy in the secondary circuit, which is converted here due to the resistance of the circuit into thermal energy. If the heated material is ferromagnetic, that part of the energy of the alternating magnetic field is converted into thermal energy directly, without converting into electrical energy.
Two types of induction furnaces are most widespread in technology: 1) furnaces with an iron core; 2) furnaces without a core - high-frequency.
Iron core furnaces have schematic diagram(Fig. 23, a), similar to the circuit of a conventional transformer, in which the primary winding is mounted on an iron core, and the secondary winding is represented by a closed ring of molten metal, i.e., combined with the load. As a result of vigorous circulation, the metal heated in the annular channel rises upward into working space furnace and, in contact with the charge located there, heats and melts it.
Furnaces without a core, in their diagram, represent an air transformer (Fig. 23, b), the primary winding of which is a copper coil - an inductor, and the secondary winding is the metal charge itself loaded into the crucible.
The effective value of the induced electromotive force E. in, depends on the amplitude value of the useful magnetic flux fm, vb, alternating current frequency f, per/sec, the number of turns of the winding w, and is expressed by the formula
In furnaces with an iron core, the value is quite large due to the concentration of the useful magnetic flux in the core, while in furnaces without a core the value is small due to large magnetic dispersion. As a result, in induction furnaces with an iron core, the required value of electromotive force E is easily achieved using alternating current with normal and reduced frequencies (f The main advantages of induction heating are the following: heat release directly in the mass of the heated material, which reduces the role of heat exchange processes, ensures more uniform heating of the material and significantly increases the thermal efficiency of induction furnaces; exceptional cleanliness of the furnace working space (due to the absence of fuel combustion products, heating element materials and electrodes that pollute it), which makes it possible to obtain especially pure metals and alloys; air and melting in a vacuum or in a gas protective atmosphere; the possibility of obtaining very high temperatures, limited only by the properties of the heated material and refractory masonry; vigorous mixing of melts by electromagnetic and thermal flows, allowing to obtain uniform alloys; chemical composition; high specific productivity of induction furnaces; high heating and melting speed; small losses of metals from waste; high technical standards of furnace units, absence of dust and gases.
The disadvantages of induction heating include: reduced power factor, since for furnaces with an iron core cos φ = 0.3/0.8 and for coreless furnaces cos φ = 0.03/0.1; limited size, power and capacity of induction furnaces compared to other units; the complexity of the electrical equipment of coreless furnaces, requiring special high-frequency alternating current sources and capacitor banks of significant capacity; limited durability of the lining of the channels of furnaces with an iron core and the crucibles of coreless furnaces: low heating temperature of the slag.
The advantages of induction heating have led to its widespread use. Iron core induction furnaces are currently the main unit for melting and casting non-ferrous metals and producing non-ferrous alloys. Coreless induction furnaces are used for melting non-ferrous and precious metals and for producing high-quality steel castings. In the metallurgy of copper, nickel and zinc, induction furnaces operating at final stages are also used. Induction heating is widely used in machine-building plants during heat treatment of various metal blanks and products.
The theory of iron core induction furnaces is based on the theory of single-phase two-winding iron core transformer. The difference between a conventional transformer and an induction furnace with an iron core is that in a transformer the secondary winding and the consumption network (load) are located at a considerable distance from one another, and in an induction furnace the secondary winding is combined with the load and is represented by a ring of molten metal.
The converted power Ppr can be expressed through the secondary current I2 and the actual active resistance of the metal in channel r2 by the formula
Power lost in the inductor ( electrical losses) Rel, expressed through the primary current I1 and the actual active resistance of the inductor winding
The total active (watt) power of an induction furnace with an iron core P will be
In the theory of induction furnaces without an iron core, these furnaces are considered as air transformers, in which, as a result of the absence of a closed iron magnetic circuit, magnetic fluxes pass through the processed charge and through the air.
The frequency f of the alternating current supplying the inductor depends on the capacity (power) of the induction furnace and the resistivity of the processed charge p2. Research shows that the larger the furnace capacity and its dimensions, in particular the diameter of the charge d, cm, and the smaller resistivity molten metal p2. ohm/cm3, the lower the minimum frequency fmin, Hz; this dependence is expressed by the formula
Each furnace capacity and resistance corresponds to a specific optimal frequency supply current at which the efficiency of the furnace reaches its maximum possible value. For high-capacity (power) coreless furnaces, it turned out to be possible to use a lower frequency of alternating current, down to the normal 50 Hz.
The active power of a coreless furnace Pa consists of the power converted in the charge and the power lost in the inductor, and is expressed by the formula
Based on the laws of the processes of fuel combustion and the conversion of electrical energy into heat, the following most important tasks on theory, operation and design of metallurgical furnaces:
a) choice of heating system for furnaces (carbon fuel or electricity);
b) selection of the type and grade of fuel and its combustion system;
c) selection of parameters of electricity and the system for converting it into thermal energy;
d) calculations of fuel combustion processes;
e) selection and calculation of combustion devices;
f) calculation and design of electric furnaces.
