>A french experiment back in the '90 if I don't mistake
> has transferred some KW on a top of a mounain
> using a 10Ghz beam.

A major difference is that the magnetic field doesn't do something 
until you do something to it so there is no power drawn until you 
"tap" it. With RF you send out the power and then try and reacquire 
it.

Based on my own practical experience I'd guesstimate that it wouldn't 
be hard to get over 80% efficient and should be possible to get above 
90%.

My own system never required high efficiency - transferring enough 
power was the aim. I had a number of small movable "stations" that 
were placed next to the transmission loop and which not only picked up 
a few Watts of power each but could also perform bidirectional 
signalling across the loop at a net rate of AFAIR over 100 kbps. The 
latter was far harder to achieve than the power transfer. I still have 
a 100mm loop running around part of my section (and enclosing my house 
from the concept demonstrator. This was not a 100m circumference loop 
as far as signal was concerned - there is a go and return conductor 
and the loop sides are only about 10mm apart - 10mm x 100m loop :-).

Worked well. Still have all the bits. Client took out patents but was 
unable to successfully commercialise the niche market area that he was 
targeting.

Note that what is generally called IPT (Inductive Power Transfer) is 
many many decades old and in current use in industry. What these 
people are doing looks essentially identical to what I did and other 
people do.


        Russell.




-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist