MadSci Network: Physics

Re: Can you ¨harvest¨energy emitted by Wi-Fi antennas?

Date: Thu Oct 21 11:47:52 2004
Posted By: Donald Howard, Nuclear Engineering, Retired
Area of science: Physics
ID: 1098346148.Ph

"The birth of an idea is a happy moment in which everything apppears 
possible and reality has not yet entered into the problem," sayeth Rudolph 
Diesel many years ago.

Possible, probable, practical:  It is certainly possible to radiate 
information.  We've been doing that since Marconi invented the AM radio.  
So it is possible to transmit power through the air in the same way Wi-Fi 
transmits information, but it is not practical to transfer, say, enough 
power to run the fan on a desk-top computer.  Radiating appreciable power 
is wasteful.  

Energy radiates from an antenna, or from the Sun, in all directions unless 
constrained somewhat by the shape of the antenna dish.  Even then, large 
amounts of that energy can and will be absorbed by the air, far more than 
would be absorbed when wires are used to transmit power.  Have you ever 
noticed that the air inside a microwave oven that's been run for a while 
is hot?  

As for designing such a system, [i.e., the min volts, min watts, min 
distance, etc.], since it's never been done, it would require what's 
called a "Developmental Program."  That means that you guess at those 
parameters and go with trial-and-error until you find the combination that 
works best.  That's a lengthy and expensive process much like what is done 
in developing a new drug. 

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