New wireless devices need no power supply, can harvest energy from TV towers

Wireless devices and sensors capable of sending and receiving data may soon be able to also harvest the power they need, right from the air, thanks to the radio waves that already emanate from cellphone and TV towers.

To really take advantage of the coming "Internet of Things", a whole lot of sensors and microcomputers will be needed, all of which will require some method of being powered, preferably without needing any cords or wires. And while putting a battery onboard the device is one solution, it also creates another issue, which is the need to replace or recharge all of those batteries at certain points in their life. But a new breakthrough from engineers at the University of Washington could help to do away with the need for a battery for some wireless devices altogether.

The team at UW has developed a technique they call "ambient backscatter", which can let devices use the cellular and TV transmissions already being broadcast around us, reflecting those signals to send and receive their own data to similar devices, without the need for a battery or other power source.

“We can repurpose wireless signals that are already around us into both a source of power and a communication medium. It’s hopefully going to have applications in a number of areas including wearable computing, smart homes and self-sustaining sensor networks.” - Shyam Gollakota, lead researcher and UW assistant professor of computer science and engineering

“Our devices form a network out of thin air. You can reflect these signals slightly to create a Morse code of communication between battery-free devices.” - Joshua Smith, co-author and a UW associate professor of computer science and engineering and of electrical engineering

To test the ambient backscatter technology, the researchers set up a small testing network in Seattle, and the devices were able to communicate with each other, as sensors would in a real-world application, even up to 6.5 miles away from a TV tower.

The future of the Internet of Things might get a jumpstart with the ability to use wireless power transmission for its sensors and microcomputers, because removing the need for a power source will greatly increase the possibilities for connected devices.

It's possible that small sensors could be built right into any device or structure, without the need for later access to replace the batteries, or built with a very tiny physical footprint to be placed in hard to reach places. For example, building these into some of our urban infrastructure, such as bridges, tunnels, subways, etc., could allow for real-time monitoring of the conditions or integrity of the structures, without requiring a remote power source.

Researchers also noted that the technology could be built into devices that also have an onboard battery, such as cellphones, so that even if that battery were to die, text messages could still be sent using ambient backscatter, powered by a TV tower.

New wireless devices need no power supply, can harvest energy from TV towers
In the future, some sensors and devices may not need an onboard power source, but instead be able to get the energy they need from the radio waves that already blanket our built environment.

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