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Mobile phones charged by the power of speech

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September 20, 2010

Harnessing sound energy from conversations could one day help recharge mobile phones ((Ima...

Harnessing sound energy from conversations could one day help recharge mobile phones ((Image: -Tripp- via Flickr)

In the search for alternative energy sources there's one form of energy you don't hear much about, which is ironic because I'm referring to sound energy. Sound energy is the energy produced by sound vibrations as they travel through a specific medium. Speakers use electricity to generate sound waves and now scientists from Korea have used zinc oxide, the main ingredient of calamine lotion, to do the reverse - convert sound waves into electricity. They hope ultimately the technology could be used to convert ambient noise to power a mobile phone or generate energy for the national grid from rush hour traffic.

Piezoelectrics are materials capable of turning mechanical energy into electricity, and can be substances as simple as cane sugar, bones, or quartz. Much research in this field has been focused on transforming the movement of a person running, or even the impact of a bullet, into a small electrical current, but although these advanced applications are not yet available in consumer products, scientists have been using piezoelectric materials in environmental sensors and speakers for years.

The Korean researchers were interested in reversing this process however. "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, authors of the article in journal Advanced Materials.

Piezoelectrics create an electrical charge under stress, and thus zinc oxide, the main ingredient of calamine lotion, was bent into a field of nanowires sandwiched between two electrodes. The researchers subjected the sandwich to sound waves of 100 decibels which produced an electrical current of about 50 millivolts.

On average, a mobile phone operates using a few volts, and as a normal conversation is conducted at about 60-70 decibels it's clear the technology falls some way short of being genuinely useful yet, but the researchers are optimistic that given time they can improve the electric yield. They hope future applications could include mobile phone charging from conversations, or sound-insulating walls near highways that boost the national grid using energy generated from rush hour traffic noise. However, with the increasing popularity of near silent electric vehicles there might be a decreasing window of opportunity for that particular application.

Via: Discovery News

9 Comments

Thanks for the interest in this article! If anyone's interested in more about the science behind this story, we've set the original scientific paper free to access for the next few weeks; you can find it here: http://www.materialsviews.com/details/news/843529/Self-Powered_Cell_Phones_Piezoelectrics_in_Action.html

Adrian Miller

Advanced Materials

AdrianMiller
21st September, 2010 @ 01:15 am PDT

Piezoelectric is a very interesting field that seems to be growing significantly. It is an interesting approach to use sound to create electricity. This article brings out quite an interesting point about rush hour traffic noise and emerging near silent electric cars. I do still believe that there is potential for this technology maybe not quite for it to be placed around highways but instead looking at placing it at major train stations where you can get high levels of noise from all of the commuters and trains themselves. This may not produce enough electricity to full remove this site from the electrical grid but it might be a great way to supplement other sources of electricity like solar, wind, hydro etc. Other source of great noise could be airports or even sport stadiums.

Noise converting piezoelectric devices sound like a great idea but would it not be perhaps more energy efficient to use piezoelectric devices that convert pressure into electricity that can be build into the floor of as mentioned above public train/bus stations, airports etc. practically any place where you have a large volume of human traffic walking across a floor surface? Another area that might be good would parts of highway that can be used to supplement electric grid just from the pressure of cars going across the road especially during the rush hour.

Let me know what you think of this.

Thanks,

Milan Sedoglavich

Milan Sedoglavich
21st September, 2010 @ 05:09 pm PDT

Good idea, but with phone big like that, I wonder who wants to use it?

nobody
21st September, 2010 @ 06:05 pm PDT

Why choose a picture of an early 1990's cell phone to illustrate an article about a new technology?

Voice power, what's old is new again! In the early days of telephones the power of a person's voice moving the coil in a dynamic microphone* is what provided the power.

Call distance was limited and amplifiers (which were called relays) were soon developed to boost the signal strength.

Sound powered phones are still used in some emergency and military applications because they work when there's no power. http://en.wikipedia.org/wiki/Sound-powered_telephone

Some of the old phones with the hand cranked magneto had wet cell, then later dry cell, batteries in their boxes to provide power. The magneto only provided the power to ring the bell. For a party line, the magneto had to ring all the bells on the line, which is why they generated 100 volts AC or more.

So this outfit is dinking around with piezoelectric materials (which have long been used as high frequency tweeter speakers with a ceramic piezo disc bonded to the back side of a thin steel disc) when there's already a long proven technology for extracting power from the human voice. I'd like to see them design a little dynamic microphone to fit into a cell phone right next to the common electret (often mis-named condenser) microphone. The output from the dynamic mic could be used just for power.

*A dynamic microphone is simply a small speaker used in reverse, with the coil design optimized for producing enough power to be amplified. A headphone speaker can be used as a microphone with a microphone jack compatible with dynamic microphones. You can plug a dynamic microphone into a headphone jack and listen to it, though they're usually not very loud and turning the volume way up can damage it.

Facebook User
21st September, 2010 @ 08:28 pm PDT

your work is so good for me to do my project in a perfect manner i expected you to do this work regularly "ALL THE BEST"

Facebook User
22nd December, 2010 @ 07:16 am PST

Everyday alternative energy generation appears in press. What will happen to Future of Conventional Energy?

JA
27th June, 2011 @ 07:36 am PDT

O/p of this circuit is quiet low..So can u tell me how to increase o/p so that it can power mobile...Can u also tell me about alternate of Piezoelectric technology which can be used to generate electricity..

Abhishek Singh
7th July, 2011 @ 02:04 am PDT

Is it possible to convert sound into electricity without input supply?

Mithun Chandramohan
14th September, 2011 @ 04:44 am PDT

is it really possible to convert sound energy to electrical energy....from the sound obtained on conversation

Prasanth Vangavolu
31st March, 2012 @ 09:57 am PDT
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