Tuesday, December 2, 2008

Self-charging cell phones?

I guess this would be the 21st century equivalent of the self-winding watch: a charging circuit that uses tiny piezoelectrics to power electronic devices such as cell phones and mp3 players by grabbing the energy from sound waves in the air.
"When materials are brought down to the nanoscale dimension, their properties for some performance characteristics dramatically change," said [Texas A&M ChemEng prof. Tahir] Cagin who is a past recipient of the prestigious Feynman Prize in Nanotechnology. "One such example is with piezoelectric materials. We have demonstrated that when you go to a particular length scale – between 20 and 23 nanometers – you actually improve the energy-harvesting capacity by 100 percent."

How much energy would be saved if we could unplug all the wall warts that we use to power our electronics? One estimate says they use more than 58 billion kilowatt-hours, wasting $3.5 billion annually in standby losses alone (because they typically draw 3-4 watts of power even when they're not being used) and consuming the output of 10 large power plants - and that's just in the United States.

Of course we can avoid the standby losses by unplugging the damn things when we aren't using them, or by using the more modern "switching mode" power supplies, which only draw current when they're actually being used; but it would be even better if our electronic devices could just convert ambient noise to the juice they need to power themselves.