真乄科技業的頂尖投資團隊

Wi-Fi訊號除了用來上網，將來還能用來充電！美國有工程師將「環繞反向散射」（ambient backscatter）技術應用在路由器，將Wi-Fi信號轉化成電力，讓5米以外的相機也有足夠的電力運作，同時不會干擾上網速度。

英國《每日郵報》報導，美國華盛頓大學研究團隊，去年8月率先公佈「環繞反向散射」技術，而首席工程師格拉科塔（Shyam Gollakota），先前出席舊金山「EmTech Digital」大會時，展出套用此技術的原型路由器「PoWiFi」。

格拉科塔帶領研究小組，透過「PoWiFi」路由器釋放無線電波，然後利用整流器轉化成直流電壓，為2個沒有電池的相機和溫度感應器提供電力，其中相機更距離路由器足有5米。

另外，研究小組亦在六個住宅安裝「PoWiFi」路由器，並要求住戶利用它上網，結果發現過半數參與測試的住戶，在使用「PoWiFi」時，並無發現網路出現減速情況。

不過此款路由器未來若投產，更強的電磁波是否會危害人體仍有待檢驗。

Wi-Fi allows us to connect to the Internet by transmitting data through the air itself, but what if it could be used to power our devices wirelessly as well? Scientists at the University of Washington are currently working to make it happen.

PoWiFi, short for power over Wi-Fi, tricks routers into sending out a constant signal that’s captured and converted into DC power by a harvester.

Wi-Fi already transmits a small amount of power to carry data, up to 1 watt by FCC guidelines, compared to the 5 watt output of a typical Android or iPhone charger. This technology captures that power that’s already being sent, and puts it to work.

PoWiFi tricks routers into sending out a constant signal that’s captured and converted into DC power.

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

Using PoWiFi, researchers were able to charge a super capacitor connected to a small camera, located 17 feet from the router; every 35 minutes, the super capacitor collected enough energy over Wi-Fi, enabling the camera to take a picture. They were also able to charge a small fitness tracker to 41 percent of its battery power in 2.5 hours.

The low, 1-watt power output of a router limits what can be run on PoWiFi, making it unsuitable for cell phones, says Dr. Mehdi Kiani, assistant professor of electrical engineering at Pennsylvania State University, but he says the technology has interesting uses for powering other low-energy devices.

This technology isn’t new. Companies like Energous have already brought products to market that send power over similar Wi-Fi signals, and they claim to be able to charge cell phones. Yet the novel feature of PoWiFi is the ability to harness power with pre-existing hardware, and the University of Washington team says their routers transmit both power and data in the same signal.

To test potential effects on Internet speed, the researchers outfitted six Seattle homes with active PoWiFi routers and asked the users to surf the web as they usually would. Four of six users found no difference, and one found their Internet actually improved--though the researchers noted that the PoWifi router was a better model than their previous router.

資料來源:蘋果日報

資料來源:http://www.frandroid.com/comment-faire/reseauetwifi/wi-fi/287896_powifi-wifi-recharger-batteries