What if your smartphone or laptop began charging the moment you entered the room?
Researchers have created a specifically designed room that can send electricity to a range of electronic devices within it, allowing them to charge phones and operate home appliances without the use of plugs or batteries.
According to Takuya Sasatani, a project assistant professor at the University of Tokyo’s Graduate School of Engineering and lead author of the new work, which was published this week in Nature Electronics, this method “enables safe and high-power wireless power transfer in enormous quantities.”
The room works on the same principle as short-range wireless phone chargers: an electric current is generated by a metal coil positioned in a magnetic field.
Existing commercial charging docks generate a magnetic field in a small area using electricity from a wall socket.
Most modern smartphones have a metal coil, and when one of these models is docked, the interaction generates enough current to charge the phone’s battery.
Commercial products, on the other hand, have a fairly limited range nowadays.
The wireless power transmission stops if you lift a phone from the dock or wrap it in a protective case. However, if a magnetic field covering the entire room, any phone within it would be able to receive wireless power.
“The thought of having a room where a variety of gadgets might easily accept electricity anywhere is incredibly intriguing and exciting,” says Joshua Smith, a University of Washington professor of computer science and electrical engineering who was not involved in the current study. “And this paper is another step in the right direction.”
The researchers describe a special test chamber that Sasatani made out of conductive aluminum sheets with a metal pole running down the center, measuring around 18 cubic meters (about similar to a small freight container).
A wirelessly powered lamp and fan, as well as more practical goods like a chair, table, and bookshelf, were provided by the team.
The researchers created a three-dimensional magnetic field within the area by running an electric current through the walls and poles in a certain way.
The system was meant to generate two different fields: one that occupies the middle of the room and another that covers the corners, allowing any device within the space to charge without experiencing dead spots.
Sasatani and his co-authors discovered that their technology could transfer 50 watts of electricity throughout the room, powering all of the devices they tested that had a receiving coil: a smartphone, a light bulb, and a fan, through simulations and measurements.
However, some energy was lost during the transfer. Depending on the strength of the magnetic field at certain spots in the room, as well as the direction of the device, delivery efficiency ranged from 37.1 percent to almost 90 percent.
Running electricity through the room’s metal walls without precautions would normally fill it with two types of waves: electric and magnetic.
This is a problem since electric fields can induce heat in biological tissues, putting people at risk.
As a result, the crew installed capacitors in the walls, which are devices that store electric energy. Sasatani adds, “It confines the safe magnetic fields within the room volume while limiting hazardous sections inside all the components implanted inside the walls.”
The safety of the room was also tested using computer simulations, which measured the amount of radiation that a human body would be exposed to in a digital replica of the powered room.
The Federal Communications Commission, for example, has established guidelines for how much electromagnetic radiation the human body can safely be subjected to, and the simulation revealed that energy absorption in the test room would be considerably below permitted levels.
Alanson Sample, an associate professor in the University of Michigan’s electrical engineering and computer science department, adds, “We’re not saying this technology is safe under all uses—we’re still experimenting.”
“But it gives us some confidence… that there is still plenty of room below that threshold of power, where we can charge your phone just as readily as you walk into a room, without having to worry about those safety issues.”
A specialized wireless charging room, according to Sample, would allow a variety of electronic devices—sensors, mobile robots, and even medical implants—to operate in the background, recharging themselves without a cable connection and allowing humans to largely ignore them.
The method could be used in more specialized scenarios as well.
“I can see this being incredibly beneficial for highly instrumented, expensive environments like an operating room,” Smith adds, “where you could picture having multiple equipment and devices just be able to be powered without needing cords.”
However, those applications are still a long way off.
“Putting aluminum sheets all over your walls is just too inconvenient—that advantage doesn’t make sense yet,” Sample adds. “We’ve just come up with a brand-new method. Now we just have to figure out how to make it work.”
He intends to continue his investigation into whether coating existing rooms with conductive material or constructing customized walls with conductive layers could allow the construction of wireless charging rooms that are also code-compliant.
Meanwhile, Sasatani intends to increase power transmission efficiency in the space and eliminate any residual areas where the charge does not reach.
Multiple start-ups are vying to send electricity via electromagnetism, lasers, or sound waves, making wireless charging a very competitive proposition.
“A lot of people are interested in beam-forming approaches,” Smith says, “where you generate a propagating radio wave and steer it around.”
“The advantage of the technique in this study is that the fields are largely magnetic, which is safer and allows for higher power for the same degree of safety, compared to sending a propagating radio wave, where the electric and magnetic fields are nearly equal.”
A charging beam, on the other hand, would not necessitate a custom-built metal room with a pole running down the center, as he points out. Each approach may have its own set of applications.
“There are other charging systems that are more far-field and give you a lot greater range,” Sample explains. “However, there isn’t a device that will provide you with, say, 10 watts of power anyplace in a space.”
THE AUTHOR IS : Sophie Bushwick is an associate editor covering technology at Scientific American.