Wireless power supply refers to a method of power transmission through non-physical contact. It is the third wireless revolution after wireless communications and wireless networks. It is regarded by the industry as a cutting-edge technology with basic application significance. It has a wide range of cross-product applications and is expected to promote breakthroughs and innovations in the communications, electronics, Internet of Things, new energy and other industries across the country and even the world.
Scientists at the Massachusetts Institute of Technology in the United States are developing a new power supply method that uses non-radiative wireless energy transmission to drive electrical appliances, whether they are mobile phones, laptops or digital cameras. If this research Be successful and their chargers can all be retired.
This research began in June 2007, when Marin Soljacic, an associate professor in the Department of Physics at MIT, lost his mobile phone battery, so he decided to join forces with several other teachers and graduate students to prepare for These everyday portable appliances develop a simpler way to power them.
The principle of this technology is actually very simple. The electromagnetic waves we are exposed to every day all carry energy. When radio broadcasts are transmitted, most of the energy is scattered in the air, and this technology uses a non-radioactive field to concentrate this energy. We all know that electromagnetic waves of a specific frequency will cause objects to vibrate. Two objects with the same natural frequency can transmit this vibration and thus transfer energy. We can have an object such as a copper antenna emit electromagnetic waves, and let the receiver receive them and convert them into energy. In theory, all electrical appliances that currently use batteries can be switched to this method of power supply. Of course, at this stage, this kind of transmission is limited to a short distance of a few meters.
As to the impact of the resulting electromagnetic radiation on the human body, researchers are conducting experiments to ultimately meet FCC standards. Developers say that the current radiation level is probably similar to that of an NMR spectrometer and should be within a safe range.
If the test goes well, this wireless power supply technology will have huge room for development. For example, it can lay lines underground and charge the phones in our hands and even the cars in progress at any time. But researchers point out that the technology is still in its infancy and these prospects are still being imagined. Tesla had already built a broadcast tower for wireless power transmission a hundred years ago, and wanted to realize another revolution in power transmission after he invented alternating current, but it was not realized in the end, but at that time his experiments in wireless power transmission had already It worked. It seems that this technology has appeared hundreds of years ago and is almost realized, but why are we still using electrical appliances with a lot of annoying wires? Is this technology lost today? Is it really possible to achieve large-scale wireless power transmission?
The "amplifier transmitter" invented by Tesla is now called a high-power high-frequency transmission line oscillation transformer and is used for wireless power transmission experiments. Tesla used the earth as the inner conductor and the earth's ionosphere as the outer conductor. Through his amplifying transmitter, he used the unique radial electromagnetic wave oscillation mode of this amplifying transmitter to establish an approximately 8 Hz signal between the earth and the ionosphere. Low-frequency vibration uses surface electromagnetic waves surrounding the earth to transmit energy. When there is no power receiving end, the transmitter only exchanges reactive energy with the heaven and earth resonant cavity, and the entire system has very little active power loss. This solution is not only feasible, but also extremely efficient, ecologically safe, and does not interfere with radio communications.
This kind of power transmission does not have very accurate positioning. In other words, any possible device can "take away love" halfway and seize power that originally belongs to others. If this kind of wireless power transmission is to be realized, there is a premise, that is, the power generated by humans has fully satisfied everyone's needs. Otherwise, who will let people use the power in vain? In terms of the current global energy trend, it is even more difficult to achieve. . In addition, political factors are also a big problem.
In terms of prophecy, I personally believe that the only way for mankind to completely escape from the energy dilemma is through controllable nuclear fusion technology. At 21:15 Beijing time on October 24, 2007, the International Thermonuclear Experimental Reactor (ITER) organization French Cadarache was officially established, and China also funded 10% of the project. No one can say exactly when it will be successful, but all the technological powers have invested a lot of money in research, and it is expected to be realized in the next 50 years (this is my guess). If successful, to give a simple example, three percent of the water molecules in sea water are heavy water molecules. So one liter of ordinary seawater can produce the energy of three hundred liters of gasoline using this technology. At that time, this kind of energy broadcast is very likely to cover the whole world, and everyone can receive power wirelessly anytime and anywhere, just like the current mobile phone network.
According to the British Broadcasting Corporation, scientists from the Massachusetts Institute of Technology in the United States reported in the latest issue of Science magazine that through electromagnetic induction, they successfully lit up lights two meters away from the power source through the air. How far away is a 60-watt light bulb. Scientists call this technology "wireless power transmission technology". By utilizing basic physical principles, laptops can eventually be charged "over the air".
The research team used two copper coils with a diameter of 60 centimeters to conduct experiments. One coil was connected to the power supply as the power transmitter, and the other as the power receiver was placed two meters away and connected to a light bulb. Scientists used the principle of "magnetic vibration". When the power supply side is turned on, both coils vibrate at a frequency of 10 MHz, thus generating a strong electromagnetic field. The electric vibrations emitted by the power supply side can be transmitted to Power receiving party. Although the two coils are not connected, they can still provide power through the air and make the light bulb shine. Even if wood, metal, or other electrical appliances are placed between the power source and the bulb, the bulb will still glow.
Researchers said that the body's response to electric fields is strong, but the body's response to magnetic fields is almost non-existent, so this system will not affect human health. Some researchers say that further experiments are needed before it can be truly applied in daily life.
Kong Li, director of the Institute of Electrical Engineering of the Chinese Academy of Sciences, believes that wireless power transmission is a special power supply method that is different from wired transmission. Electromagnetic waves can propagate in space, so it is possible to light up lights through wireless power transmission as reported in the report.
There are roughly two methods to achieve wireless power transmission. One is the electromagnetic induction method of two coils used by researchers in the report, and the other is to emit electrical energy in the form of laser or microwave to The remote receiving antenna then acts on the load through rectification, modulation, etc.
The principle of wireless power transmission is not difficult to understand, but it has not been well applied. Because electromagnetic waves are transmitted in free space, the energy is not easy to concentrate and has poor directionality. Especially microwaves, which diffuse in space, make the originally small energy deplete faster. Therefore, wireless transmission is difficult to transmit a large amount of energy, has low power, poor overall efficiency, and will cause great electromagnetic pollution to the space.
As a scientific research, studying wireless power transmission technology may lead to the development of other scientific and technological fields, but this technology is only suitable for some specific occasions, such as energy transmission between satellites and man-made aircraft. Use wireless methods.
As for domestic wireless power transmission research, everyone understands the principles, but because the efficiency is too low and there are too few reasonable use occasions, not many people are doing research. There is a question of rational use of science and technology. Wireless power transmission can be used for some special purposes, but if it is used for long-distance ground power 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, Japan's Showa Aircraft Industry Corporation exhibited a non-contact power supply system. This system transmits power wirelessly based on the principle of electromagnetic induction. The two induction coils can be placed adjacent to each other on the left or right or corresponding to the top and bottom.
The principle of electromagnetic induction technology used by this technology is not much different from what middle school students learn in textbooks. It can provide power transmission at a distance of about 10 centimeters.
However, placing it in a horizontal position may cause some electrical energy to be lost, and the coil itself will generate heat.
Due to patent issues, Showa Aircraft Industry did not disclose specific implementation details. However, the company claims that this power supply system can provide a transmission efficiency of more than 90%. In addition, the company can also achieve power transmission between two coils at a distance of more than 60 centimeters.
The company demonstrated lighting up 10 100W incandescent lamps at a distance of 60 centimeters and placing a metal frying pan between the two coils, proving that the frying pan produced no heat. The size of the two transmission coils is 50x50 cm and the thickness is 5 cm.
Showa Aircraft Industry Co., Ltd. said that this system can charge electric vehicles, or provide auxiliary power supply for refrigerated trucks that need power supply when they stop and rest at convenience stores.