IoT devices could be powered by Wi-Fi radio waves, researchers say

Charging via spare Wi-Fi channels, or through changing ambient temperatures, could provide all the power needed for the minuscule sensors required for the Internet of Things, some scientists think.

Alternative power sources Internet of Things Wi-Fi
UW Today

The University of Washington is placing itself at the forefront of a quest to find ways to power the micro-sensors that will be used for the Internet of Things (IoT).

Scientists at UW are exploring two concepts that, with some development, they think might be ultimately suitable for keeping the devices running.

One is technology that researchers there call PoWi-Fi, or Power over Wi-Fi. It's a way to charge wireless devices through Wi-Fi radio waves.

Another is a potential method for harvesting energy through changing temperature and atmospheric pressure.

Both could be suitable for the micro-sensors needed for the IoT.


The large numbers of sensors proliferating on our internet need powering. What's wrong with common batteries, you might ask?

The problem with that idea is that batteries aren't as chemically advanced as we need them to be. They need changing frequently. That's not a problem when we're dealing with one or two smoke detectors twice a year, say, as we have become used to.

The problem arises when each home or workplace has thousands of sensors, many in hard-to-reach places—as is projected to occur in the next few years.


Are we really going to change the batteries annually in every eco-moisture sensing flower pot in the yard, for example? There could be scores, it could take hours.

Vendors know that for the IoT to become ubiquitous, they'll have to ensure that the tech is easy to work with. Hence the frantic search for micro-power sources and low-power chips. I've written about some of the chips before.

Atmospheric power harvesting

Alternative methods are being investigated. A Dutch builder in the early 17th century invented a clock that was powered by temperature fluctuations and atmospheric pressure, for example.

Then, in 1928, Swiss Jean Leon Reutter built a mechanical pendulum clock that could be run for years with no winding. In that case, too, energy was derived from temperature and atmospheric pressure changes in the environment.

Both clocks are "the inspiration for a group of computer scientists and electrical engineers who hope to harvest power from the air," explained the University of Washington in a press release on its website in September 2014.

Anywhere that temperature changes occur naturally could be used as locations for the power source, according to the report.


The temperature power concept works through bellows filled with temperature-sensitive gas, the researchers say.

The bellows expand and contract as the temperature cools and heats, thus creating kinetic energy. That kinetic energy is converted into electricity to power sensors located on the bellows.

The sensors "can check for water leaks or structural deficiencies in hard-to-reach" areas, for example, the university says.

"A temperature change of only 0.25 degrees Celsius creates enough energy," the university says on the website.

Wireless Wi-Fi charging

That was in 2014. Earlier this year, some other researchers at the same university came up with PoWi-Fi, another IoT-possible power source.

It riffs on the idea that some energy in ambient Wi-Fi signals often gets close to "meeting the operating requirements for some low-power devices," the university said in a separate press release.

In PoWi-Fi, "power packets" are sent on unused Wi-Fi channels.


That technology will be presented this week at the Association for Computing Machinery's CoNEXT 2015 conference in Germany, a powwow on emerging networking experiments and technologies.

The scientists say their technology could be used to run low-power devices, like a VGA camera, from 17-feet away.

And with the temperature idea, that's two possible alternatives on the table.

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