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Charging via Wi-Fi could be the future of wireless power

Researchers from the University of Washington have developed a way to power devices using existing Wi-Fi systems.

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    Cellphones pictured charging as a generator circulates power due to a power cut after an earthquake in Kathmandu, Nepal April 29, 2015. Researchers at the University of Washington have developed a way to power small devices using existing Wi-Fi systems, potentially doing away with the need for cables and charging stations.
    Navesh Chitrakar/Reuters/File
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Picture a world where charging stations are obsolete, and tangled cable wires are an unpleasant, but distant, memory.

That world may soon become reality thanks to researchers at the University of Washington (UW), whose “power over Wi-Fi” technology makes it possible to recharge devices wirelessly, through the air, from up to nearly 30 feet away. The idea is to roll communication and power into a single system, utilizing an already existing Wi-Fi network to do away with the inconvenience of plugging in.

“We have a huge Wi-Fi infrastructure already in place,” Vamsi Talla, a researcher who worked on the project, told Popular Science. “If we can repurpose existing infrastructure for power delivery as well, then we can actually enable wireless power delivery in homes and offices.”

“Power over Wi-Fi” uses a harvester that takes radio frequency (RF) power, which Wi-Fi routers already transmit, and transforms it into usable direct current (DC) power. This ability to harness functioning Wi-Fi power makes the UW team's system distinct from existing wireless charging technologies, such as those of Energous, which require their own, dedicated hardware. 

But there’s a limit to how much output a single router can manage at a given time, so the researchers designed software that tricks routers into sending out power signals only when user traffic is below a particular threshold — ensuring both uninterrupted charging and connectivity. 

“If we wanted to just blast as much power as we possibly can, that would kill your Wi-Fi, because you’d have power on the channel all the time,” Bryce Kellogg, who also worked on the project, told Wired.

“We optimized the router so that… Instead of having continuous power on one of your Wi-Fi channels, we split it among your three non-overlapping Wi-Fi channels,” he added. “That allows us to deliver about the same amount of power without impacting any one channel very much.”

The concept of wireless power is a throwback to Nikola Tesla, the Serbian-American inventor, physicist, and electrical engineer best known for designing the alternating current (AC) system for supplying electricity.

Mr. Tesla “dreamed of eliminating wires for both power and communication,” the UW researchers wrote in their paper. But while wireless communication is now well-established, they noted, wireless power has not seen the same success.

The researchers are hoping to change that. Already they’ve tested “power over Wi-Fi” on a camera from 17 feet, on temperature sensors from 20 feet, and on rechargeable batteries from 28 feet — though these experiments have been limited by Federal Communications Commission guidelines that cap router power output at 1 watt.

They also tested the system’s effect on Internet speeds by installing the technology in six Seattle-area homes. Five found that the router’s charging ability did not affect their ability to surf the Web.

The published paper is just the beginning, however. The UW team is currently exploring marketing possibilities and further improvements on the technology; for instance, by streamlining the harvesters to increase their maximum range, Wired reported.

The system also has the potential to help power the Internet of Things: The growing number of ever-smaller, low-power sensors and devices embedded in homes and offices everywhere, the researchers wrote.

“Forget power mats and battery packs; the energy we need is already all around us,” according to Wired. “Now we have a way to harness it — and stay connected, too.”

Mr. Tesla would be proud.

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