Application of thermoelectric technology
The earliest temperature difference alternator In 1942 by Former Soviet Union It is successfully developed, and the power generation efficiency is 1.5%~2% Later, the demand for power supply in some special fields greatly stimulated the development of thermoelectric technology Since the 1960s, a number of thermoelectric generators have been successfully used in space shuttles, military and ocean exploration In recent years, with the continuous progress of science and technology, thermoelectric generators are gradually expanding their application fields, not only in military and High-tech In addition, it also shows a good application prospect in civil applications With the approaching energy and environmental crisis, scientists have increased their research efforts in the use of low-grade and waste energy for power generation, and some research results have been industrialized 2.1 Remote space exploration
Since the successful landing of Apollo spacecraft on the moon in 1969, human exploration of space has been going deeper and deeper With the expansion of exploration space, people are targeting more distant planets, even remote space beyond the solar system In a world far away from the sun, dark, cold and empty, the solar radiation is extremely small, and it is difficult for solar cells to work Stable heat source, compact structure, reliable performance and long service life radio isotope Thermoelectric power generation system becomes an ideal choice Using thermoelectric technology, a coin sized Radioisotope heat source It can provide continuous power for more than 20 years, which is unmatched by any other energy technology The National Aeronautics and Space Administration (NASA) has successively used thermoelectric power generation devices with various radioisotopes as heat sources in its Apollo lunar module, Pioneer, Pirate, Voyager, Galileo and Ulysses spacecraft Voyager 1 spacecraft needs 25 years of scientific research in space, and all the electrical energy on the spacecraft is provided by the thermoelectric conversion module Its power generation system includes 1200 thermoelectric generators, which provide heat energy by neutron decay of radioactive fuel Pu-238 The power system has been operating safely for 21 years, and is expected to continue working for 15-20 years Compared with solar cells, radioisotope thermoelectric power generation system not only has the advantages of long life and reliable performance, but also has attractive specific volume and specific weight If the Ulysses spacecraft is designed according to the structure of solar cells, the weight of the solar panels it carries will reach 550 kg, twice the weight of the spacecraft itself, which is difficult for the carrier rocket to load When the thermoelectric power generation system is used, the weight of the generator is only 56 kg, which can fully meet all the power requirements of the spacecraft in navigation, communication and the use of scientific instruments
2.2 Military
Radioisotope generator In addition to playing an important role in the space field, the Navy is its second largest user As early as the early 1980s, the United States completed the development of 500~1000W military thermoelectric generators, which were officially included in military equipment in the late 1980s Its biggest advantage is no sound, no vibration, concealment, and has important applications in submarines, long-distance signal transmission, etc The thermoelectric generator is placed in the deep sea to supply power for the radio signal transmission system The system is an integral part of the U.S. missile positioning system network. Its design working depth is up to 10 kilometers, working power is more than 1W, and its service life is more than 10 years Recently, Hi-Z Company has developed a high-performance micro thermoelectric generation module based on quantum dot principle for the military [14], which is used to supply power for various wireless sensors on board ships These sensors shoulder multiple tasks such as monitoring fracture, corrosion, impact damage and temperature drift. Only the thermoelectric generator can meet its extremely high requirements for power size, weight, leakage and life In order to meet the requirements of the Army for Power supply system The special requirements of the, US Department of Energy The "Energy Harvest Science and Technology Project" was launched The research uses the thermoelectric generation module to collect the body heat of soldiers for battery charging Its short-term goal is to achieve a minimum output of 250 watt hours of electric energy for 12 hour combat tasks. At present, the research project has achieved a number of research results 2.3 Telecommunication, navigation and equipment protection
The stable performance and maintenance free characteristics of thermoelectric technology make it play an important role in remote areas where power generation and transmission are difficult [15]. It has been used for microwave relay station power supply, remote automatic radio receiver, automatic weather forecast station, unmanned beacon lights, cathodic protection of oil pipes, etc. in polar regions, deserts, forests and other unmanned areas The world's largest thermoelectric generator manufacturer, Global Thermoelectric Inc. of the United States, manufactures thermoelectric power generation equipment for pipeline monitoring, data acquisition, communication and corrosion protection, with an output power of 5000W Since the late 1960s, the former Soviet Union has produced more than 1000 radioisotope thermoelectric motors, which are widely used lighthouse And navigation signs, with an average service life longer than 10 years This type of generator takes Sr90 as the heat source and can stably provide 7~30V, 80W output 2.4 Small power supply
Small size, light weight, no vibration and no noise make the thermoelectric generator very suitable for small power supply (less than 5W) Thermoelectric technology can play a unique role in the short-term micro watt and milliwatt level electric energy required by various unmanned sensors, micro short-range communication devices, micro generators for medical and physiological research, sensing circuits, logic gates and various error correction circuits [16,17] The Hi-Z company manufactures the micro battery that can coordinate the load. Its output power can reach 2.5W and output voltage 3.3V
Integrated universal thermoelectric micro battery with the size of cm2 system study [18]. After three years of project development, some products have entered the practical stage Japan Seiko Instrument Company has developed a watch that uses human body temperature to generate electricity Miniature battery [19]. The battery is made of BiTe bulk material, with a size of 2 mm × 2 mm × 1.3 mm, and consists of 50 pairs of elements in series. A temperature difference of 1K can produce a voltage of 20 mV, and the output power is 1 μ W. Germany D. The output power of T. S company is 10~40 μ W's thin-film thermoelectric generator production occupies a leading position in the world 2.5 Thermoelectric sensor
Recently, based on the Seebeck effect of thermoelectric conversion materials, many new thermoelectric sensors have been successfully developed and used for low-temperature temperature measurement [20], single pixel infrared and X-ray detection [21], hydrogen and other combustible gas leakage detection [22], etc
The Application of Scientists in the Japanese Institute of Industrial Technology Applied Film A thin film thermoelectric hydrogen sensor was prepared [23] Its working principle is Film material Half of the surface is coated with catalyst. When hydrogen is present, the temperature of thermoelectric conversion material coated with catalyst will rise, and then the potential difference will be established at both ends of the device The measurement of voltage signal can not only sense the hydrogen leakage, but also calculate the hydrogen concentration Traditional hydrogen sensors have many shortcomings, such as large volume, heavy weight, complex structure, poor gas selectivity (often with a broad spectrum response to combustible gas), and long response time, which have become increasingly unable to meet the operating requirements In addition, the traditional sensor can reach the peak value only when its sensitivity to gas and temperature are strong (200~400 ℃), which will not only consume additional heating power, but also easily lead to fire The thin film sensor made of thermoelectric conversion materials can work near room temperature with small size, good selectivity and short response time 1% hydrogen content can output 2 mv voltage signal with a response time of 50 s This type of sensor is used in Hydrogen fuel cell System, hydrogenation station Micro Air Vehicle It has a broad application prospect Off, usually at a higher temperature
Germany D T. S. Company has successfully developed micro based on its 235 thermoelectric module infrared sensor [24]. It is used for non-contact temperature measurement, monitoring of household and factory equipment, etc. It has the characteristics of small size (mm3), light weight (mg), no filter window, rapid response, not affected by environmental heat conduction and heat convection, and stable operation under high heat radiation Its F-type thermoelectric infrared sensor is 5.6 mm × 3.1 mm × 0.08 mm in size and 19 mg in weight 2.6 Low grade and waste heat power generation
For a long time, due to the limitation of production cost and conversion efficiency, the application of thermoelectric technology has been limited to high-tech, military and aerospace fields Recently, due to the decreasing amount of fossil energy and the approaching environmental degradation caused by fossil energy combustion, people have realized the importance of using low-grade and waste heat for power generation to solve environmental and energy problems [25] In addition, the universality and cheapness of available heat sources greatly enhance the commercial competitiveness of thermoelectric power generation As we know, power generation cost mainly consists of operating cost and equipment cost The operation cost depends on the conversion efficiency and raw materials, and the equipment cost depends on the device that generates rated output power Although the cost of thermoelectric conversion module is very high, the cost of raw materials for low-grade and waste heat power generation is very small, nearly zero, and the operating cost is very low, so the total cost of power generation is reduced, making thermoelectric power generation can compete with existing power generation methods commercially In recent years, Japan has carried out a series of government plans entitled "Research Plan on Energy Recovery from Solid Waste Combustion" to study waste heat power generation technology for solid waste incinerators, combine turbine generators and thermoelectric generators, achieve maximum utilization of waste incineration heat of different scales, and make waste truly available resources [26] Following Japan, the US Department of Energy announced funding in November 2003 the pacific ocean Northwest National Laboratory, Michigan Technical University Pittsburgh PPG Process Co., Ltd. and other units mainly support their development of high-performance thermoelectric conversion materials and application technologies. Their main applications are exhaust heat in industrial production and waste heat and waste heat utilization in other components To produce a benefit of 250 billion yuan However, the marketization, specialization and industrialization of garbage power generation in China have just started. In order to mobilize more social forces to participate in garbage power generation, the State Council recently formulated a series of Comprehensive utilization of resources It is hoped that this preferential policy can promote the development of this technology (3) Automobile waste heat
With the continuous improvement of people's living standards, cars, as an important means of transportation for modern families, have begun to enter the homes of ordinary people The automobile not only brings convenience to people's life, but also promotes the continuous progress of social economy However, with the increasing popularity of automobiles, people's demand for energy, especially oil and natural gas, is growing, which further accelerates the deterioration of the global energy problem At the same time, the environmental pollution caused by automobile exhaust also has a certain impact on the world environment The energy loss caused by automobile exhaust, cooling water, lubricating oil and thermal radiation accounts for a large proportion of gasoline combustion energy. For example, the energy loss of ordinary family cars at normal speed is 20~30 kW. Scientists have been trying to apply thermoelectric technology to environment-friendly vehicles, and provide auxiliary power for vehicles by using the waste heat of automobile exhaust and the residual heat of engines In this way, not only the comprehensive performance of the vehicle can be greatly improved and the energy consumption of the engine can be reduced, but also the emissions of pollutants in the exhaust can be reduced, killing three birds with one stone According to theoretical research, if thermoelectric technology can be applied to vehicles, it is expected to save 20% of fuel, which is enough to provide electrical energy for a medium-sized vehicle [29] Japan has developed a small thermoelectric generator using automobile exhaust for power generation, with a power of 100W, which can save fuel by 5% [30] The United States also recently announced the successful trial production of 1000W power generator based on tail gas of large trucks [31, 32] It shows that the thermoelectric generator installed on the Mack diesel engine in the United States looks like a vertical muffler in appearance
(4) Natural heat
Solar radiation heat, ocean temperature difference heat, geothermal and other natural heat are the most ideal power energy that nature endows mankind with inexhaustible Traditional natural thermal power generation uses heat engine, generator or steam generator
Steam turbine as prime mover, such a system can obtain good technical and economic indicators only in the occasion of large capacity power generation At present, the international goal is to turn to direct power generation devices (such as thermoelectric conversion modules) that have no moving parts, are silent and do not need maintenance, and replace the above energy conversion components with them, greatly simplifying the structure of energy conversion components of existing natural thermal power generation systems, and obtaining considerable economic benefits Professor Stevens of Mississippi State University in the United States conducted research on power generation using the temperature difference between the surface and the ground [33] This mode has the characteristics of stable performance, long life, no sound radiation, invisibility, continuous operation at night and in harsh environments [font=verdana], etc. It can be widely used for small remote sensing and communication devices that have been unattended for a long time. Its initial design power is 100 mW
(5) Other scattered heat sources
Recently, Professor Rowe of Cardiff University demonstrated that a color TV can work continuously for one hour by using the residual heat of the residual water in the bathtub after a person's bath to generate electricity. If the system can operate for three years, the cost of generating electricity is equivalent to that of conventional energy power companies
