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Re: Inverse Square 'law' Re: About wireless energy transfer
Original poster: Ed Phillips <evp@xxxxxxxxxxx>
>...Inverse Square 'law'...
Welllllll.
And i am NOT proposing New Physics.
Really.
8)>>
"inverse quare' is The Law FOR OMNIDIRECTIONAL sources.
Each unit radius out from the source the energy gets
'spread more widely', becomes 'thinner'. (To put it in
non mathematical terms.)
However.
Ponder, please, a 'Very Well Collimated' beam.
Parallel. BIG 'reflector', meaured in wavelengths.
The beam (laser, microwave) does not get bigger.
I believe this was the concept for the 'rectenna'
driven concept.
Now no real beam will beperfect, but, maybe,
close enough for 'all practical purposes'.
best
dwp"
You have of course moved from "non radiative" transfer to
conventional radiation but the point is worth discussing. As you
point out, "no real beam will be perfect". In the case of the "well
collimated beam" there will be a region (usually called the "far
field") determined by the wavelength and the dimensions of the
antenna beyond which propagation DOES follow an "inverse square law"
of received energy PER UNIT AREA of receiver. If the receiving
antenna is made big enough to intercept ALL of the transmitted power
then the "efficiency" is high but the dimensions involved really
preclude serious consideration of such "energy beaming" or at least
make it incredibly expensive if long distances are involved. People
have proposed the idea to provide microwave power to high-altitude
airships and there is at present at least one outfit trying to get
someone to pay them to develop a system.
The "rectenna" is the "receiving end" of such a scheme and
involves the use of distributed rectifiers throughout the
structure. Some workers have claimed efficiencies as high as 80% for
such a device.
Proponents of using an orbiting array of solar panels whose output
drives a microwave transmitter composed of many distributed magnetron
amplifiers would use such a receiver. The whole subjected has been
treated seriously in the literature and there are many publications
which discuss "real" systems. They involve antennas with dimensions
of the order of several miles on both the transmit and receive ends
of the link. There are so many practical problems with the idea that
I think it will always remain in the talking stage although some
short-range relatively low-power demos have been made.
Ed