What if your smartphone or laptop starts charging as soon as you enter the door?Researchers have developed a purpose-built room that can Various electronic devices that transfer energy to it, It can charge mobile phones and power home appliances without plugs or batteries.
Takuya Sasatani, a project assistant professor at the Graduate School of Engineering at the University of Tokyo and the lead author of the new study, said the system “achieves safe and high-power massive wireless power transmission,” which was published this week Natural electronicsThe room relies on the same phenomenon as a short-range wireless phone charger: a metal coil placed in a magnetic field generates an electric current.
Existing commercial charging docks use power from a wall socket to generate a magnetic field in a small area. Most of the latest smartphones are equipped with a metal coil, and when such a model is placed on the base, the interaction will generate enough current to power the phone battery. But the range of commercial products today is very limited. If you remove the phone from the base or wrap it in a protective cover that is too thick, wireless power transmission will stop. But if the magnetic field fills the entire room, then any phone inside can use wireless power.
Joshua Smith, a professor of computer science and electrical engineering at the University of Washington, who was not involved in the new research, said: “The prospect of having a room that can power various devices anywhere is really exciting and exciting.” “And this paper is another step towards achieving this goal.”
In this study, the researchers described a custom test chamber of about 18 cubic meters (about the equivalent of a small freight container), which was built by Sasatani with conductive aluminum plates with a metal rod in the middle. The team equipped the room with wirelessly powered lights and fans, as well as more mundane items, including chairs, tables, and bookshelves. When researchers pass current through walls and poles in a fixed pattern, it generates a three-dimensional magnetic field in space. In fact, they designed the setup to generate two separate fields: one fills the center of the room, and the other covers the corners, allowing any device in the space to charge without encountering dead spots.
Through simulations and measurements, Sasatani and his co-authors found that their method can provide 50 watts of power in the entire room, turning on all the devices equipped with the receiving coils they tested: smartphones, light bulbs, and fans. However, in the transfer Some energy was lost in the process. The transmission efficiency varies from as low as 37.1% to as high as about 90%, depending on the magnetic field strength at a specific point in the room and the orientation of the device.
Without precautions, the metal walls of the room are filled with two types of waves when electricity flows through them: electric waves and magnetic waves. This poses a problem because electric fields generate heat in biological tissues and pose a danger to humans. Therefore, the team embedded a capacitor in the wall, a device that stores electrical energy. “It confines the safe magnetic field to the volume of the room, while confining hazardous components to all components embedded in the wall,” Sasatani explains.
The researchers also tested the safety of the room by running computer simulations, measuring the environment that the human body would come into contact with in the digital model of the power room.Authorities such as Federal Communications Commission A standard has been established for how much electromagnetic radiation the human body can safely be exposed to, and simulations have shown that the energy absorption in the test chamber will be far below the acceptable limit. “We are not saying in general that this technology is safe for all uses-we are still exploring,” said research co-author Alanson Sample, an associate professor in the Department of Electrical Engineering and Computer Science at the University of Michigan. “But it gave us some confidence… We still have many places that can be far below this power threshold, where we can still charge our phones as easily as walking into a room without worrying about those safety issues. .”
In addition to mobile phones, Sample also stated that a dedicated wireless charging room can allow various electronic devices-sensors, mobile robots and even medical implants-to run in the background, charging themselves without a wired connection, allowing humans Ignore them to a large extent. This technique can also be applied to more professional situations. “I can imagine this is very useful for highly instrumented, expensive spaces, such as operating rooms,” Smith said, “where you can imagine all kinds of instruments and equipment that can be powered without a power cord.”
But these applications are still in the foreseeable future. “Putting aluminum panels on the wall is really troublesome-this benefit doesn’t make sense yet,” Sample said. “We have just developed a brand new technology. Now we have to find a way to make it practical.” He plans to continue to study whether coating existing rooms with conductive materials or constructing special walls with conductive layers can build wireless charging rooms that also comply with building codes. . At the same time, Sasatani hopes to improve the efficiency of power transmission in the room and eliminate any residual points that cannot be reached by electric charges.
Wireless charging is a very competitive concept, and many start-ups are competing to transmit electricity through electromagnetic, laser or acoustic waves. “A lot of people are interested in beamforming methods, in which you actually generate a propagating radio wave and control it,” Smith said. “The advantage of the method in this article is that the magnetic field is mainly a magnetic field. Compared with the actual transmission and propagation of radio waves, it is safer and allows higher power at the same safety level, where you have roughly equal electric and magnetic fields. On the other hand, he pointed out that the charging beam does not require a custom metal room with a pole in the middle. Each technology may have its own purpose.
“There are other far-field charging mechanisms that can provide you with greater distances,” Sample said. “But there is actually no mechanism that can provide you with 10 watts of power anywhere in the space.”