This part could wireless charge all your devices

What if your smartphone or laptop starts charging as soon as you walk through the door? Researchers have developed a specially constructed part that can transmit power to a variety of electronic devices inside, charge phones and power home appliances without outlets or batteries.

This system “allows safe, high-power wireless energy transfer in large volumes,” says Takuya Sasatani, project assistant professor at the University of Tokyo Graduate School of Engineering and lead author of the new study. which was published this week in Natural electronics. The piece is based on the same phenomenon as short-range wireless phone chargers: a metal coil, placed in a magnetic field, will produce an electric current.

Existing commercial charging docks use electricity from a wall outlet to produce a magnetic field in a small area. Most recent smartphones are equipped with a metal coil, and when such a model) is placed on the dock, the interaction generates enough current to supply the phone’s battery. But today’s commercial products have a very limited range. If you lift a phone from the dock or put it in a thick case, wireless power transfer stops. But if a magnetic field filled an entire room, any phone inside would have access to wireless power.

“The prospect of having a room where a variety of devices could be powered anywhere is really compelling and exciting,” says Joshua Smith, professor of computer science and electrical engineering at the University of Washington, who is not did not participate in the new study. . “And this document takes another step to make that possible.”

Credit: Takuya Sasatani, et al., Natural electronics

In the study, the researchers describe a custom test room of about 18 cubic meters (roughly the equivalent of a small cargo container), which Sasatani built from conductive aluminum panels with a metal pole in the middle. The team outfitted the room with a cordless lamp and fan, as well as more down-to-earth items including a chair, table and bookshelf. When the researchers passed an electric current through the walls and pole in a set pattern, it generated a three-dimensional magnetic field in space. In fact, they designed the setup to generate two distinct fields: one that fills the center of the room and another that covers the corners, allowing all devices in the space to charge without encountering dead spots.

By performing simulations and measurements, Sasatani and his co-authors found that their method could deliver 50 watts of power throughout the room, powering up every receiver-coil-equipped device they tested: a smartphone, a light bulb and a fan. . However, some energy was lost during the transfer. Delivery efficiency ranged from a minimum of 37.1% to a maximum of approximately 90%, depending on the strength of the magnetic field at specific points in the room, as well as the orientation of the device .

Without precautions, passing current through the metal walls of the room would generally fill it with two types of waves: electric and magnetic. This poses a problem, as electric fields can produce heat in biological tissues and pose a hazard to humans. The team therefore embedded capacitors, devices that store electrical energy, into the walls. “It confines safe magnetic fields within the volume of the room while confining dangerous parts inside all components embedded inside the walls,” says Sasatani.

The researchers also tested the room’s safety by running computer simulations, measuring what the human body would be exposed to in a digital model of the powered room. Authorities such as the Federal Communications Commission have set standards for the amount of electromagnetic radiation to which the human body can be safely exposed, and the simulation suggested that the energy absorption in the test room would remain well below acceptable limits. “We’re not saying in general that this technology is safe for all uses, we’re still exploring it,” says study co-author Alanson Sample, an associate professor in the Department of Electrical Engineering and Computer Science at the University. ‘University of Michigan. “But it gives us some confidence… that there’s still plenty of room for us well below that power threshold, where we can still charge your cellphone as easily as you walk into a room, without having to worry about these security issues.

Beyond phones, Sample suggests that a dedicated wireless charging room would allow a variety of electronic devices – sensors, mobile robots or even medical implants – to run in the background, charging without a wired connection and leaving the humans largely ignore them. The technique could also be applied to more specialized situations. “I can imagine this being really useful for highly instrumented and expensive spaces like, say, an operating room,” Smith says, “where you can imagine various instruments and devices can just be powered without the need for cords “.

But these applications are still far in the future. “It’s just too cumbersome to put aluminum foil all over your walls – that advantage doesn’t make sense yet,” says Sample. “We have just developed a completely new technique. Now we have to figure out how to make it practical. He plans to continue his research to find out if coating existing rooms with a conductive material or building specialized walls containing conductive layers could enable building code-compliant wireless charging rooms. Meanwhile, Sasatani hopes to improve the efficiency of power transmission in the room and eliminate persistent points that the load does not reach.

Wireless charging is an extremely competitive concept, with several start-ups vying to transmit energy via electromagnetism, lasers or sound waves. “A lot of people are interested in beamforming-type approaches, where you actually generate a propagating radio wave and steer it,” Smith says. “The advantage of the approach here in this article is that the fields are predominantly magnetic, which is safer and allows for higher power for the same level of safety, compared to actual transmission of a radio wave. propagating, where you have roughly equal electric and magnetic fields.” On the other hand, he points out, a charging beam wouldn’t require a custom-built piece of metal with a pole in the middle. Each technique can have their own uses.

“There are other charging mechanisms that are farther out, which give you much longer range,” says Sample. “But there’s really no mechanism that gives you, say, 10 watts of power anywhere in a space.”

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