RE: Wireless power transmission (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Tue, 19 Jun 2007 11:10:22 +0100
From: Colin Dancer <colind@xxxxxxxxxxxxxx>
To: 'Tesla list' <tesla@xxxxxxxxxx>
Subject: RE: Wireless power transmission (fwd)


Hi Dave,

Thanks for the reply, but I'm now not quite sure what mechanism you're
suggesting for power transmission.

Originally you were talking about longitudinal waves propagated by
electrostatic repulsion between charged particles (ions) mechanically
vibrating in the free air.  If this was the case you'd definitely be talking
about a plasma wave, because this pretty much the definition of an
electrostatic plasma wave http://en.wikipedia.org/wiki/Waves_in_plasma .
Such a wave might well propagate power a small amount of power beyond the
near field, but even allowing for the increased ion density around a coil,
the damping forces due to the neutral particles in free air totally dominate
the very weak forces between ions.  Your best bet would be a plasma filled
wave guide, but this wouldn't really be "wireless" and even then using
microwaves would probably have much lower loses.

You now seem to be talking about large scale varying electrostatic fields.
Ions might be moved by such a field, but the damping still dominates so they
can't really help it to propagate or "stiffen" the field vibrations.  It's
also the case that to generate a large scale varying electrostatic field
you'll need to move about large amounts of charge to/from somewhere else.
If your "receiver" is closer together than your two charge reservoirs you
might well get a fair degree of capacitive coupling to the vibrating field,
but if it is further away then the charge in the two locations will tend to
cancel out just leaving classis EM radiation to propagate in the far field.


If you want to transfer power over long distances using capacitive coupling
the only suitability sized electrodes would be the earth and the ionosphere,
but losses in such a system would make the system totally non-viable.

So, coming back to your original claim that Tesla discovered some novel
mechanism of wireless power transfer, I think the consensus is that he was a
great visionary who invented many, many wonderful things (polyphase power
probably being the most important) but that in this area he was mistaken.

Having said all that, I am perfectly happy to be proved wrong and look
forward to you producing a new wonder device!

Colin.
---------- Forwarded message ----------
Date: Mon, 18 Jun 2007 21:37:08 -0500
From: David Thomson <dwt@xxxxxxxxxxxx>
To: 'Tesla list' <tesla@xxxxxxxxxx>
Subject: Wireless power transmission

Hi Colin,

> I agree you can get "longitudinal"/compression/sound waves in a plasma 
> (a highly ionized gas).

Yes, we see this on the surface of the Sun.  Scientists can "see" sunspots
on the other side of the Sun by tracking longitudinal waves in the plasma.

> However, this is absolutely _not_ a phenomena you can observe in 
> normal breathable air, because:
> 
> * the density of ions in air is normally very low, typical no more 
> than a few thousand per cubic centimetre
> 
> * the mean free path (the distance an atom/ion/molecule travels before 
> a
> collision) for air at sea level is approx 0.1um.

In normal air, you would be correct.  But in the case of air next to a
wireless power generator, the ion concentration is rather high.  One of the
by-products of a Tesla coil of any type is the production of ions near the
top load.  If you leave the Tesla coil operating for a period of time, it
will fill a space with ions. 

Thus the ion density normally increases near a wireless power transmitter.  

> To get plasma waves in normal pressure air requires near total 
> ionization of the medium (think nuclear fireball or a huge electric 
> arc).

We don't need plasma waves.  All we need is an electrostatic field.  Each
ion will repel every other ion, building up a stiffness in the electrostatic
field.  The stiffness of the electrostatic field can be acoustically
modulated, just as can a wooden reed or a metal bar.  The efficiency of the
wireless power generator will depend partially upon the stiffness of the
surrounding electrostatic field.

> Even if you do manage to build a device to do this to large volumes of 
> air, I recon I'll stick to my wires for energy transmission rather 
> than roasting everyone on the planet.

A stiff ambient electrostatic field occurs naturally in plastic wrap
factories, near waterfalls, just prior to lightning storms, on dry cold
days, and when you pull your clothes out of the dryer.  Nobody gets roasted
in these situations.  The electrostatic field when you take your clothes out
of the dryer will likely be many times stronger than the electrostatic field
needed to transfer small amounts of power across rooms.

I do agree, however, that large scale use of the wireless system Tesla
envisioned is likely to be dangerous to the planet.  Not necessarily because
of heat, but because it will divert the natural flow of Earth's electrical
ground currents, disorient insects and animals, and possibly alter weather
patterns.  There is a lot of technology we can do, but probably ought not
do.  That also goes for some technology we already have in use.

But as experimenters, we should thoroughly investigate each technology and
understand its effects.  Only with proper testing can we determine the
benefits and perils.

I'm positive I have the proper understanding of wireless power transmission
figured out.  Now I just have to finish building a working model, and also
figure out how to combine electromagnetic theory with acoustics in order to
quantify it properly.  There are other interesting things that can be done
with wireless power transmission technology, btw.  I could careless about
sending a few watts of power to my cellphone.  It's the other things you can
do with this that is most interesting.

Dave