Researchers seek to harvest radio waves for extra smartphone battery power

New technology promises to allow smartphones to run longer, not by improving battery tech, but by converting wasted radio signals into power.

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All of the recent hoop-la about extending smartphone battery life with special metals, using graphite batteries to charge a device in seconds, and even power-reducing microprocessors, could well be moot.

Researchers at Ohio State University think that the way to extend battery life is not by improving battery tech—something we've found hard to do in comparison with other tech innovations—but by using the existing energy that's already found in the device that goes to waste.

The reason: the radio signals emitted by a smartphone are a form of power.

So harvest the stray signals, convert it all to DC, and squirt it back into the phone in the form of electricity, the researchers say.

Existing batteries could last 30% longer with this kind of boost, they say.

Recycle the radio waves

"When we communicate with a cell tower or Wi-Fi router, so much energy goes to waste," says Chi-Chih Chen, a professor of electrical and computer engineering at the university, who's been working on the project.

Nearly 97% of cell phone signals never reach a destination and are simply lost in thin air, the researchers say. Much of it can't be recaptured, but some can, and those lost milliwatts can extend the battery life, if they're re-used as a kind of battery extender.


Harnessing existing radio signals is not a completely new idea. Radio signals have been used to charge some sensors, like thermometers. But the Ohio State scientists say that their system is more "powerful and efficient," according to an article published by Ohio State University's newsroom.

Unlike other efforts, their system harvests the energy from the source by harnessing it from the air. The system can collect milliwatts, rather than the smaller amounts obtained by other systems.

Smartphones need more power than sensors. That's why the other systems don't work on a smartphone, they say.

High-frequency alternating current

The group's idea is quite simple. Radio waves are a form of high-frequency alternating current (AC) anyway. So once you've grabbed that AC power, all you have to do is convert it into DC, the electrical system which powers devices like phones.

Getting it, though, is one of the hardest elements to achieve, because you don't want to siphon off so much power that you compromise the phone call or data session.

However, there's often plenty of excess power emitted from a cellphone because, despite signal processing like beamforming, phones send their signals in all directions.

Form factor

Form factor for the necessary equipment is a cellphone-case type appendage, but the team hopes to ultimately make it fit in a skin that sticks directly to the phone.

They say that there's no reason the technology couldn't be built directly into devices, either.


Nikola labs is the Kickstarter startup that the university associates are forming to market the invention. They reckon the yet to-be crowdfunded device will cost $100 when it's ready.


Copyright © 2015 IDG Communications, Inc.

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