cell phones powered by conversation?

[Amby 490]

Chatty teenagers could be the world's next renewable energy source.

Scientists from Korea have turned the main ingredient of calamine lotion into a tiny material that converts sound waves into electricity. The research could lead to panels that can charge a cell phone from a conversation or provide a boost of energy to the nation's electrical grid generated by the noise during rush hour traffic.

"Just as speakers transform electric signals into sound, the opposite process — of turning sound into a source of electrical power — is possible," said Young Jun Park and Sang-Woo Kim, the two corresponding authors of a new article in the journal Advanced Materials.

"Sound power can be used for various novel applications including mobile phones that can be charged during conversations and sound-insulating walls near highways that generate electricity from the sound of passing vehicles," the co-authors added.

Harvesting energy from phone calls and passing cars is based on materials known as piezoelectrics. When bent, a piezoelectric material turns that mechanical energy into electricity.

Lots of materials are piezoelectric: cane sugar, quartz and even dried bone creates an electrical charge when stressed. For decades, scientists have pumped electricity into piezoelectric materials for use in environmental sensors, speakers and other devices.

Over the last few years, however, scientists have made dramatic advances in getting electricity out of piezoelectric devices. Most of these devices, which are not yet available for consumer purchase, would generate power as a person walks, runs or, in this case, talks. The U.S. Army is even looking at partially powering some vehicles by channeling the physical impact of a bullet into a small electrical current.

The Korean scientists, however, want to harness a different kind of power source: sound waves.

Using zinc oxide, the main ingredient in calamine lotion, Young Jun Park, Sang-Woo Kim and their colleagues created a field of nanowires sandwiched between two electrodes. The researchers blasted that sandwich with sound waves, which at 100 decibels were not quite as loud as a rock concert. A normal conversation is about 60-70 decibels.

The sound waves produced a mild electrical current of about 50 millivolts. The average cell phone requires a few volts to operate, several times the power this technology can currently produce.

The new research is interesting, said Michael McAlpine, a scientist at Princeton University who also builds energy harvesting devices.

"But the real question though is whether there is enough ambient noise to act as a power source as for a cell phone," said McAlpine. A consumer probably wouldn't want to attend a rock concert or stand next to a passing train to charge their cell phone.

The Korean scientists agree: 50 millivolts is not a lot of power, but they also say their research is proof of concept. As they continue their work, they expect to get a higher power output.

http://www.msnbc.msn.com/id/39155886/ns/technology_and_science-science/

[one...two...tree 2,762]

Wow! That's putting money where your mouth is!

[SMR 368]

Actually, 50 mV is not any power. It's a voltage. When articles try to sound technical but demonstrate a basic lack of understanding of the technology being discussed, it just sounds ridiculous.

And this really isn't just nitpicky because with these types of technologies, the issue is not if you can generate the voltage but rather can you provide the current. Piezoelectrics can easily provide a lot more than 50 mV of voltage, provided you don't try to pull any current. But if you try to pull current, the source impedance will kill your voltage and you get practically no power.

Piezoelectrics may be reasonable for small applications like cell phones where portability is important. However, for things like gathering energy from highway noise it really isn't practical. These devices are difficult to make and require energy and resources in production. It's unlikely you could recover the energy used in production within the lifetime of the device. That's not the issue with cell phones since it's great if you don't have to plug in, even if you didn't actually save any energy. With highway walls, not so much.

[Hilarious Clinton 452]

The navy has used sound powered phones for years.

[mawilson 2,133]

Not going to work for me, unfortunately, since I mostly use my phone to check email, play games and browse the web.

[Amby 490]

my phone battery would never die!