Making a city “smart” usually involves blanketing it in sensors that can measure everything from air pollution to traffic. Smart home? More sensors. One problem, of course, is that all of these sensors need a source of power to keep working. It may one day be possible to charge them via something that’s already pervasive–Wi-Fi.
Researchers at the University of Washington are testing a new method for harvesting power through the air, using radio frequency signals sent through Wi-Fi routers. By tweaking the software inside a standard router, they were able to make it charge small devices without noticeably slowing down the browsing speed.
“There’s several different benefits in different applications,” says Joshua Smith, a computer science and electrical engineer professor who heads the university’s Sensor Systems Laboratory. “If you never need to get access to a battery to replace it, you can do something like seal it in a wall. That also applies to implanted devices inside the body–where right now you have to do surgery to change the battery.”
At this point, the technology is limited to charging sensors or small batteries, partly because current routers only put out a small amount of power. But the researchers say that eventually it’s conceivable it could also charge more complex gadgets like phones.
“You probably can’t power today’s phone this way,” says Smith. “But with future phones that have improved energy efficiency and maybe special modes to support this kind of operation, you can imagine operating them off of these wireless networks.”
It’s arguable that we might not want to charge phones this way, despite the convenience, because it wastes more power than plugging into the wall. Still, Smith points out that one of the reasons this is possible at all is that the energy efficiency of microelectronics keeps improving exponentially.
“The energy required is getting smaller and smaller,” he says. “That helps with the overall efficiency of the system.”
The researchers are not the only ones working on transmitting power through the air; Energous, a startup launching a product next year, has another device that can also charge electronics through radio frequency waves. The company’s, however, doesn’t have the advantage of using Wi-Fi networks that already exist everywhere.
At the University of Washington, the next step will be tweaking routers further so they only put out extra power when needed–right now, their system sends out power whether a device needs it or not.