In brief
WiFi-powered charging showed promise in the experiments described in June 2015, but continuous signals and sufficient power remained challenges. Researchers developed software to keep signals flowing, while Ossia’s Cota system offered another approach with potential applications for connected sensors.
Researchers in the United States are studying how to use wireless network signals (WiFi) to charge mobile phones.
They modified electronic devices and wireless routers in test households so that the devices would charge through signals transmitted by the routers over a 24-hour period. The routers could still perform their primary function as normal: providing WiFi.
The principle is similar to the way solar panels convert light into electricity. In this experiment, the equivalent of the “solar panel” is a component called a “rectifier”. It converts energy from the radio waves emitted by the router into a DC voltage. A DC converter then raises the voltage to a usable level, allowing the device to charge.
The experiments demonstrated that the device was viable, but the challenge was how to get the router to supply enough energy continuously. After all, WiFi signals only become more active when people are using the internet, at which point they can be used to charge devices. When nobody is online, no WiFi signals are transmitted, making charging impossible.
To solve this problem, the researchers developed software that sends meaningless data when nobody is using the internet. This provides a continuous stream of signals that can be converted into usable electricity.
However, solving the problem of signal continuity raised another question: “Are WiFi signals powerful enough to fully charge a mobile phone?” In many countries, including the United States, WiFi network power is limited to 1 watt or less, while an iPhone charger requires at least 5 watts. How, then, can charging work?
A company called Ossia proposed a system named Cota and designed a “wireless network hub” that transmits radio waves at wireless network frequencies without sending communication signals. The Cota setup can generate up to 20 watts of power, but can supply only 1 watt to a single mobile phone. With a continuous supply of WiFi signals, it could charge an iPhone countless times in a day.
Commenting on this type of technology, IT researchers at the British consultancy Navigant said: “Many sensors in future cities and smart homes will need this kind of technology. Sensors powered by wireless networks could be used to monitor air quality or the status of systems across an entire city. Removing the need to worry about batteries would eliminate one of the barriers to exploring such technologies.”