Yell Phone: Using Speech to Recharge Portable Gadgets

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Engineers in South Korea are working on a system that converts sound to energy, with one potential real-world application of the technology being cell phones that recharge themselves as people speak into them.

We won’t see a fully functioning solution like this in the near future, but the team demonstrated that “a prototype of the technology was able to convert sound of around 100 decibels – the equivalent of noisy traffic – to generate 50 millivolts of electricity,” according to the Telegraph.

Project head Dr. Sang-Woo Kim hopes to make the technology more efficient so that it someday can provide more power at quieter sound levels, but said that even as it stands now, “Our current output performance can be applied to various electronic devices with low-power consumption such as self-powered sensors and body-implantable tiny devices.”

The actual process by which sound is converted to energy under this system seems relatively straightforward. According to the Telegraph:

“The technology uses tiny strands of zinc oxide sandwiched between two electrodes. A sound absorbing pad on top vibrates when sound waves hit it, causing the tiny zinc oxide wires to compress and release. This movement generates an electrical current that can then be used to charge a battery.”

The concept behind this technology – the piezoelectric effect – has existed for a while, with kinetic wristwatches (like several that Seiko sells) being one of the better real-world examples today. A kinetic watch has a little weight in it that oscillates as you move your arm around, and that oscillation gets converted to energy that’s stored and used to power the watch.

This system developed by these South Korean engineers looks like it may leverage the same type of oscillation, except that it’s created by sound vibrations instead of physical movement. It’ll likely be a long, long time before we’ll ever be able to completely power a phone like this, though.

If you can’t wait that long, you can always pick up one of these wind-up phone chargers for around $20. I’ve used a couple of them and they do indeed work, although you only get about half a minute of battery life for every minute worth of spinning—no need to find an outlet, though.

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