Re: Water capacitor, was: Re: General Questions

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jason Johnson by way of Terry Fritz <twftesla-at-uswest-dot-net>" <hvjjohnson13-at-hotmail-dot-com>

Comments interspersed


> Back to the topic.  I actually started a thread titled "Pure water
capacitor"
> around Feb 2000.  Being an engineering physics major, I had access to a
near
> limitless supply of 10Mohm/cm water from the chem dpt.  One of the
chem/physics
> profs (a "physical chemist") and I worked out some rough calcs, and
decided
> that it was more than doable using the available resources.  We didn't
work out
> any force equations, though - only breakdown/resistance calcs.

I would worry more about the breakdown/capacitance/resistance type
calculations first. At least until a experimental unit is built. "I" would
imagine that the force exerted on the unit would be dependent upon many
things, such as operating frequency, pulse rise time, current, voltage, just
to name a few. In the tank circuit of a tesla coil these forces may be
trivial and easily overcome or they may play a signifigant role in designing
and construction of a water-capacitor unit, just to withstand them. (I
myself am leaning towards the trivial side, at least for the kinds of
dimensions and requirements I'm thinking about, kinda on another hunch).

>
> The problem is that a "Walmart-quality" purifier probably isn't good
enough.  A
> Britta pitcher/filter isn't going to work, and the deionized water (also a
> Walmart product) probably will not, either.  But that's more guess-work
than
> fact.  I suppose if a large space is used between plates, then lower
"quality"
> water is needed....  My calcs were to use two 1/4" aluminum plates 16"x16"
> spaced 1/8".  It would have worked in theory (for a resonant cap, I
think).

I agree. The Walmart deionizer and/or deionized water probably wouldn't work
well enough to use in our application as a tank cap, and maybe not even
enough to show the principal behind a pure water cap. This is also guesswork
on my part I have no idea what type of purity a walmart deionizer is capable
of, but this doesn't mean that water capacitor research is out of the reach
of the ordinary garage hobbiest! Check out
http://www.labx-dot-com/v2/rframe.cfm?adclass=Water%20Purification this is one
category on LABX that has just what we need and at a reasonable price if one
wants to wait a while checking out various posts and placing a want ad or
two. Of particular interest on this page is item # 80351 listed as a
BARNSTEAD BANTAM DEIONIZER. This deionizer can produce very pure water from
plain tap water and if used in combination with some already semi-purified
water can put out 19-38 liters per hour of up to 18,000,000 Ohm/cm water. It
sold for 20.00!! Too bad I missed by a few days!

>
> The other problem is actually getting the parts clean.  EVERYTHING that
goes
> into the water (including the "tub") must be THOROUGHLY washed.  This
means
> soap and water, alcohol, MANY rinses, and then just letting things soak
for
> several weeks, and changing the water every day.  The problem is that only
a
> VERY few particles are needed to destroy the insulating properties of the
> water. Soaking allows the "crud" to leech out of the plastic, metal, etc.

Agreed. Very, very clean conditions need to be acheived and the cap would
need to be sealed for continued operation. With enough patience this could
be achieved by the average hobbiest. But if anyone has access to a clean
room at NASA or a semiconductor manufacturer it would be a tad easier.

>
> Also, the cap must have a top, so that dirt, dust, and other "stuff" can't
> contaminate the water.

Definately.

>
> I remember doing a lot of thinking/designing, but decided to abandon it
for the
> MMC (and a good choice, I'd say).  The problem was that I'd never really
know
> without doing it, and I didn't feel like "wasting" a month and many $$$ on
> parts (the Al and heavy plastic enclosure had to be purchased) only to
have it
> fail.  Plus I didn't want it to work, then fail a year down the road when
> "crud" had leeched from the plastic and/or aluminum.

Obviously some research needs to be done in this area, before everyone jumps
in. Like I said, it may not work at all or to such a limited degree that it
wouldn't be worth it to go past the initial research state.

>
> I'd love to see someone actually do some testing (and I know I don't have
the
> time between school projects, job hunting (anyone need a semi-experienced,
> entry-level mechanical design engineer in the Milwaukee, WI or Kalamazoo,
MI
> area?), etc).

Well consider me on it. I don't know how fast my research will go, it
depends on how steady of a cash flow I can stir up for this project as an
unemployed (well at least for the time being) 15 year old.

Regards,
Jason Johnson

>
> My two cents
>
> Mark B.
>
>