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This section introduces wireless power supply technology. Scientists at MIT are developing a new power supply method, which uses non-radioactive wireless energy transmission to drive electrical appliances, whether mobile phones, laptops or digital cameras. If this research is successful, their chargers can be retired.
This research began in June 2007, when Marin Soljacic, an associate professor in the Physics Department of Massachusetts Institute of Technology, was reimbursed for his mobile phone battery, so he made up his mind to develop a simpler power supply method for these daily portable appliances in conjunction with several other teachers and graduate students.
The principle of this technology is actually very simple. The electromagnetic waves we come into contact with every day carry energy. When radio broadcasting is transmitted, most of the energy is dispersed in the air, and this technology uses a non-radioactive field to gather this energy. As we all know, electromagnetic waves with a specific frequency will cause vibration of objects, and two objects with the same natural frequency can transmit this vibration, thus transmitting energy. We can make an object, such as a copper antenna, emit electromagnetic waves, which are received by the receiver and converted into energy. Theoretically, all electrical appliances that use batteries can supply power in this way now. Of course, at this stage, this transmission is only limited to a short distance of several meters.
Regarding the influence of electromagnetic radiation on human body, researchers are conducting experiments to finally meet the requirements of FCC standards. According to the developer, the current radiation level is about the same as that of a nuclear magnetic vibrator and should be within the safe range.
If the experiment is successful, this wireless power supply technology will have a huge development space, such as laying underground lines, charging our mobile phones, and even moving cars at any time. However, the researchers pointed out that the technology is still in its infancy, and these prospects are still under imagination.
Tesla, the pioneer of wireless power supply technology, established a radio tower for wireless power transmission a hundred years ago, trying to realize another power transmission revolution after he invented alternating current, but it didn't happen in the end, but his wireless power transmission experiment was successful at that time. This technology seems to have appeared hundreds of years ago, and it has almost been realized, but why are we still using electrical appliances with many annoying wires? Is this technology lost today? Is it really possible to realize large-scale wireless power transmission?
Tesla invented the "amplifier transmitter", now called the high-power high-frequency transmission line * * * vibration transformer, which is used for wireless transmission test. Tesla regards the earth as an inner conductor and the ionosphere of the earth as an outer conductor. Through his amplifier transmitter, a low-frequency vibration of about 8 Hz is established between the earth and the ionosphere by using the unique radial electromagnetic wave oscillation mode of the amplifier transmitter, and energy is transmitted by using the surface electromagnetic waves around the earth. When there is no power receiving end, the transmitter only exchanges reactive energy with the heaven and earth resonant cavity, and the active loss of the whole system is very small. This scheme is not only feasible, but also efficient, ecologically safe and will not interfere with radio communication.
This kind of power transmission is not very accurate, that is to say, any possible equipment can "snatch love" halfway and take away the power that originally belonged to others. If this kind of wireless power transmission is realized, there is a premise that the power generated by human beings has fully met the needs of all people. Otherwise, as far as the current global energy trend is concerned, it is even more difficult to realize who will use electricity in vain. In addition, political factors are also a big problem.
According to the forecast, personally, the only way for mankind to get rid of the energy dilemma completely at present is through controlled nuclear fusion technology. 2007124 October, Beijing time 2 1: 15, the International Thermonuclear Fusion Experimental Reactor (ITER) was officially built in Catalach, France, and China also contributed 10% of the project. No one can say when it will succeed, but all the powerful countries in science and technology have invested a lot of money in research, which is expected to be realized in the next 50 years (this is also my guess). If successful, for a simple example, water molecules in seawater have 3% of the weight of water molecules. So one liter of ordinary seawater can generate 300 liters of gasoline energy under this technology. By then, this kind of energy broadcast is likely to cover the whole world, and everyone can receive electricity wirelessly anytime and anywhere like the current mobile phone network.
According to the BBC, scientists at the Massachusetts Institute of Technology reported in the latest issue of Science that they successfully lit a 60-watt light bulb more than two meters away from the power supply through electromagnetic induction. Scientists call this technology "wireless power transmission technology". By using the basic physical principles, the laptop can finally be charged "in the air".
The research team experimented with two copper coils with a diameter of 60 cm. One coil is connected to the power supply as a power transmitter, and the other coil is placed two meters away as a power receiver and connected to the light bulb. Scientists use the principle of "* * * vibration". When the power of the transmitter is turned on, both coils vibrate at the frequency of 10 MHz, thus generating a strong electromagnetic field, and the electric vibration from the transmitter can be transmitted to the receiver. Although the two coils are not connected, power can still be supplied from a distance to make the bulb glow. Even if wood, metal or other electrical appliances are placed between the power supply and the light bulb, the light bulb will still glow.
The researchers said that the human body has a strong response to the electric field, but little response to the magnetic field, so this system will not affect human health. Some researchers say that further experiments are needed before it can be really applied to life.
Kong Li, director of Institute of Electrical Engineering, Chinese Academy of Sciences, believes that wireless power transmission is a special power supply mode different from wired transmission. Electromagnetic waves can travel in space, so it is possible to light electric lights by wireless transmission, as reported.
There are two ways to realize the wireless power transmission, one is the electromagnetic induction of two coils proposed by researchers in the report, and the other is to transmit the electric energy to a remote receiving antenna in the form of laser or microwave, and then act on the load after rectification and modulation.
The principle of wireless power transmission is not difficult to understand, but it has not been well applied. Because electromagnetic waves propagate in free space, the energy is not easy to concentrate and the directionality is poor, especially microwave, which diffuses in space, making the original little energy fail faster. Therefore, wireless transmission is difficult to transmit a large amount of energy, with low power and poor overall efficiency, and it will cause great electromagnetic pollution to space.
As a scientific research, the research on wireless energy transmission technology may promote the development of other scientific and technological fields, but this technology is only suitable for some specific occasions, such as the energy transmission between satellites and artificial aircraft can be carried out wirelessly.
Everyone knows the principle of wireless power transmission in China, but few people study it because of its low efficiency and few occasions for rational use. There is a problem of rational use of science and technology. Wireless transmission can be used for some special purposes, but if it is used as long-distance ground transmission or long-term charging of household appliances, I think it may not be practical.
At the AT International 2009 exhibition held in Yokohama, Japan, Showa Aircraft Industry Corporation of Japan exhibited a non-contact power supply system. Based on the principle of electromagnetic induction, the system can transmit electric energy wirelessly. The two induction coils may be placed adjacent to each other on the left and right sides, or correspond to each other up and down.
The principle of electromagnetic induction technology used in this technology is not much different from what middle school students learn in textbooks. Power transmission can be provided at a position around 10 cm. However, placing it in a horizontal position may lose some electric energy and the coil itself will heat up.
Because of the patent problem, Showa Aircraft Industry Company did not disclose the specific implementation details. However, the company claims that this power supply system can provide more than 90% transmission efficiency, and in addition, the company can realize power transmission with the distance between two coils above 60 cm.
The company demonstrated that 100W 10 incandescent lamp was irradiated at a distance of 60 cm, and a metal frying pan was placed between the two coils, which proved that the frying pan did not generate heat. The size of the two transmitting coils is 50x50 and the thickness is 5cm.
Showa Aircraft Industry Co., Ltd. said that this system can charge electric vehicles or provide auxiliary power for refrigerated trucks with power supply needs when parking in convenience stores.
In fact, the concept of wireless power supply technology has existed for many years, and many experts hope to make a breakthrough here. Basically, wireless power supply technology can adopt the following methods:
Electromagnetic coupling Electromagnetic coupling is familiar to power supply engineers, and transformers use this principle to transfer energy. If the two windings of the transformer are separated, it is wireless power supply in a sense. The charging of electric toothbrush is a typical case, but the electromagnetic coupling method has great disadvantages. Without a magnetic core with high magnetic permeability as a medium, the magnetic field lines will be seriously dispersed in the air, which will lead to the decrease of transmission efficiency, especially when the two coils are far away. So it is not suitable for high-power and long-distance wireless power supply.
Photoelectric coupling converts electric energy into light energy, such as laser, which is transmitted to the destination and then converted into electric energy. This wireless power supply technology is intuitive, and photoelectric conversion technology is widely used. However, there is a defect in the transmission path of light, that is, there can be no obstacles on the transmission path. Therefore, this technology also has great application defects.
Electromagnetic vibration The word electromagnetic vibration is a bit strange. It is said that its principle is similar to sound wave vibration. The two media have the same vibration frequency, so they can be used to transfer energy. WiTricity technology adopts this principle. They call it radiation-free electromagnetic vibration. Of course, this may not mean that this technology has no radiation, but it is very different from our usual concept of electromagnetic radiation.
According to the report of American Physicist Organization Network on July 2 1 day (Beijing time), several research groups are trying to use radio waves to provide energy for low-energy micro devices. With the help of this technology, Duke University in the United States has developed a helmet with sound reminding function.
China pioneer Haier China
Haier's concept of "tailless TV" does not need power, signal and network cables. Haier said that the product uses wireless power transmission technology in cooperation with MIT.
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