MadSci Network: Engineering

Re: Would it be possible to provide wireless power to a device?

Date: Sun Jul 6 18:24:01 2003
Posted By: Gary Treistman, Undergraduate, Gen. Knowl. Dept., Programming Technologies
Area of science: Engineering
ID: 1056732535.Eg

It certainly is possible to transmit power over the air; obviously the 
first one commonly used is plain old light, as in solar cells. The same 
idea can apply to almost any other energy dense electromagnetic 
radiation, like microwaves.

Alternately in close proximity (up to 5 feet) straight induction of a
changing magnetic field (where the first order field effects are
transferred) is commonly used to power/charge devices.
In these scenarios, you aren't practically sending 12V or any other 
specific voltage, rather you are transferring energy, which can then be 
converted to whatever voltage you may need.

These are probably the most common/practical methods of xferring power 
over the air.

I cannot give you a ready source for information, but this is so common 
that a simple Internet search using terms: "power" "distribution" "remote"
"telepower" "energy" "plugless", should give you a start.
Madministrator Note:  A main issue with providing power wirelessly is that 
RF and Microwave power transmission tends to be reduced with distance, 
following the famous "inverse square law".  For example, a 40 Watt 
transmission from a Cellular Transmission station will be  generally be 
reduced to the microwatt range when it reaches a cellular phone a mile 
away or so.  Unfortunately, a few microwatts don't do much in terms of 
providing power to a device.  

Power through a transmission line - through power lines and such - tend 
to drop off more linearly with distance rather than following an inverse 
square law, because the power does not spread over a spherical area but 
moves linearly down the power line.  Laser light similarly does not spread 
as severely because it is has so much directionality, being focused in a 
very thin beam. - Eric Maass

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