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[DPRG] Solar still

Subject: [DPRG] Solar still
From: Kipton Moravec kip at kdream.com
Date: Sun Dec 22 11:33:01 CST 2002

Heating a swimming pool is much easier than the requirements for a solar
still.   The temperature you need is much lower, so the quality of the
heater can be lower (and cheaper).

There are two components to pool heating.  1 Heating the water. 2 preventing
it from cooling.  Most people concentrate on Heating and ignore the Cooling.

In Michigan we were able to extend the season a month in both directions
with a solar pool cover and no heater.  There are two kinds of solar pool
covers.  One that looks like bubble wrap and the other that is denser and
white, and not very thick.  1/8" or so.

The Non-bubble wrap kind is a little more money, but lasts a lot longer.
The idea is that in the fall and spring the days are warm, but the nights
are cold.  The temperature at night drops the pool temperature faster than
the day temperature can warm it.

The pool cover also helps prevent evaporation which also cools the pool
water.  There are pool chemicals available that help slow down the
evaporation by putting some kind of invisible film on the surface of the
water that makes it harder for the water to evaporate. I have heard people
say it works, but I have not tried it.

==========================

One site says the solar pool heater needs to be 50% to 80% of the surface
area of the pool.  Using that as a guideline you can buy panels, or make
them.

The store bought panels are usually 4x8 or 4x10 plastic.  They have a big
pipe at the top and bottom, and a bunch of smaller pipes connecting top and
bottom.  The colder water from the filter goes in the bottom and out the top
to the pool inlets.

If you want to do it yourself you can use PVC pipe and paint it black or use
irrigation hose (already black)  Both are cheap.  Calculate the surface area
you need from the pipe you are using and you have how much you need.

There are ways to make it better, but it adds cost.

You can substitute surface area with reflectors.  Instead of say 3 4x8
panels of pipes, you could have 1 4x8 pipe and 2+ 4x8 reflectors. (it is not
100% efficient so 1:1 is not correct. (That is what they have to do for
getting higher temperatures.)  But then you may have to follow the sun with
the reflectors to keep the sun on the panels.

You can also put plastic over the pipes to trap the heat from the sun on the
roof so more will transfer to the pipes.  I do not know how to do this so it
is not an eyesore for the neighbors,  If the back of your house faces south
this may be an option.  If the front of the house faces south the curb value
of the house will go down.

I don't know how it is in California, but if all the backyards have fences
like here you could run the pipes / panels on a south facing fence.  It is
not as efficient having it straight up and down, as opposed to a slanted
roof, so you will need more surface area, but it is easier to get to and
will not be seen as much by the neighbors.  If your south facing fence is in
the shade then it will not work unless the leaves are gone.


Kip




----- Original Message -----
>From: "Ed Okerson" <eokerson at texasconnect.net>
To: "DPRG List" <dprglist at dprg.org>
Sent: Saturday, December 21, 2002 6:11 PM
Subject: [DPRG] Solar still


> Sorry about the non-roboticcs post, but I remember some time back a
> discussion here about solar stills.  As I recall, some were interested in
> using them to smelt aluminum, or other metals.  Has anyone ever considered
> using one to heat water?  I was thinking about an economical pool heater
> design.  The typical solar pool heater only extends the swimming season by
> a week or two, at a cost of a few thousand dollars.  If I am going to put
> that kind of cash into a solar system, I want to swim a lot more than a
> couple of more weeks.  Does anyone have any data on how to calculate the
> potential heating capacity of these things?
>
> Ed Okerson
>
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> DPRGlist at dprg.org
> http://nimon.ncc.com/mailman/listinfo/dprglist
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