http://tech.yahoo.com/blogs/null/143945
Nokia builds cell phone that recharges itself with radio waves
Prototype Nokia phone recharges without wires
Pardon
the cliche, but it’s one of the holiest of Holy Grails of technology:
Wireless power. And while early lab experiments have been able to
“beam” electricity a few feet to power a light bulb, the day when our
laptops and cell phones can charge without having to plug them in to a
wall socket still seems decades in the future.
Nokia, however,
has taken another baby step in that direction with the invention of a
cell phone that recharges itself using a unique system: It harvest
ambient radio waves from the air, and turns that energy into usable
power. Enough, at least, to keep a cell phone from running out of juice.
While
“traditional” (if there is such a thing) wireless power systems are
specifically designed with a transmitter and receiver in mind, Nokia’s
system isn’t finicky about where it gets its wireless waves. TV, radio,
other mobile phone systems — all of this stuff just bounces around the
air and most of it is wasted, absorbed into the environment or
scattered into the ether. Nokia picks up all the bits and pieces of
these waves and uses the collected electromagnetic energy to create
electrical current, then uses that to recharge the phone’s battery. A
huge range of frequencies can be utilized by the system (there’s no
other way, really, as the energy in any given wave is infinitesimal).
It’s the same idea that Tesla was exploring 100 years ago, just on a
tiny scale.
Mind you, harvesting ambient electromagnetic energy
is never going to offer enough electricity to power your whole house or
office, but it just might be enough to keep a cell phone alive and
kicking. Currently Nokia is able to harvest all of 5 milliwatts from
the air; the goal is to increase that to 20 milliwatts in the short
term and 50 milliwatts down the line. That wouldn’t be enough to keep
the phone alive during an active call, but would be enough to slowly
recharge the cell phone battery while it’s in standby mode,
theoretically offering infinite power — provided you’re not stuck deep
underground where radio waves can’t penetrate.Nokia says it hopes to
commercialize the technology in three to five years.