Photo credit: The UW team used ambient signals from this Wi-Fi router to power sensors in a low-resolution camera and other devices. Dennis Wise/University of Washington Engineers from the University of Washington have discovered how to use the untapped energy transmitted by Wi-Fi routers to power devices. The technology is called Power over Wi-Fi (PoWiFi) and the final paper will be presented next month at the CoNEXT 2015 meeting in Germany.
PoWiFi's prototype combines a Wi-Fi transmission strategy that delivers power on multiple channels, and antennae that can be attached to devices and harvest energy from the multiple channels simultaneously and turn it into DC current.
The radio waves emitted by Wi-Fi routers transmit about 1 watt of power – the maximum allowed by the FCC – which is used to carry data to devices. In comparison, a typical smartphone charge requires 5 watts of power. Routers send signals intermittently when data is requested by a device, so the team developed an optimized version that sends out power packets continuously over the channels not used by the data.
"For the first time we've shown that you can use Wi-Fi devices to power the sensors in cameras and other devices," said lead author Vamsi Talla, in a statement. "We also made a system that can co-exist as a Wi-Fi router and a power source — it doesn't degrade the quality of your Wi-Fi signals while it's powering devices."
Earlier in the year, we reported that this technology was able to power a small grey-scale camera positioned 5 meters (17 feet) from the router. In the past months, the team has conducted more proof-of-concept experiments and show that PoWiFi is able to recharge the battery of a Jawbone Up24, a wearable activity tracker, from 0 to 41 percent in 2.5 hours. The technology doesn't compare yet to traditional charging methods, which can fully charge this device in 80 minutes.
The researchers tested this technology in six different homes to investigate the possible deterioration of Internet speed. None of the users noticed any changes in how quickly a video would stream or a web page would load.
Although these experiments are really promising, the devices used only needed small amounts of power. Before Wi-Fi charging becomes readily available, there are significant improvements needed to guarantee stability and reliability from the router, as well as being able to integrate the charging antenna directly into devices. Furthermore, as you can see from the image, at the moment the antennae are fairly sizeable.
The team is hopeful that all these obstacles can be overcome. "In the future, PoWi-Fi could leverage technology power scaling to further improve the efficiency of the system to enable operation at larger distances and power numerous more sensors and applications," said co-author Shyam Gollakota, assistant professor of computer science and engineering at the University of Washington.
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