The energy needed to charge electrical devices is all around us, we just have to find a way to harvest Wi-Fi signals and convert them into power. Now, a team from the University of Washington has developed a system that scavenges the energy from ambient Wi-Fi and uses it as a power source for a battery-free camera.

The new research shows how it’s possible to send power to devices using technology that is already available and present in most of our homes. The team are calling their new approach power-over-Wi-Fi, or PoWiFi, and have used it to power a temperature sensor and a camera. One of several groups of researchers looking at how to use background Wi-Fi to power electronics, they hope that it could help in developing devices that form the “Internet of things.”

As Wi-Fi signals are normally broadcast only in bursts when they are in use, the team had to find a way of overcoming this to give the devices an unbroken power source. They managed to do this by modifying the routers to send out continuous noise when a channel is not being used to send data. This noise could then be harvested by the sensor they developed and converted into a DC current that can charge a battery.

Since the adapted routers only broadcast the noise when the Wi-Fi signals are not sending information, it means that there shouldn’t be a drop in performance of data transmitted to anyone using the Wi-Fi at the same time that it’s being used to charge devices. To test this, the researchers fitted six homes with the remote cameras, and found that there was only a minimal drop in data rates.

The cameras were able to charge through a brick wall and operate up to 5 meters (16.5 feet) away from the router. This could have significant uses for surveillance, though it might need a little more work before it is put to official use, as it could only take one photo every 35 minutes. The temperature sensor was able to function up to 9 meters (29.5 feet) from the router, and could be useful for houses that need them in the attic without the added hassle of having to install power.

Either way, the researchers say that they’ve managed to show proof of concept and that more work will help develop the technology further. They think that this demonstration might enable others to start developing more tech that could then help make the 'Internet of things' a reality.