Subject: Solar Water Heating

From: dale <[email-masked]>
Date: Wed, 20 Mar 1996 08:43:23 +0000

Sometime this summer I hope to begin building some log cabins at our 
children¹s farm camp. I would like include some solar energy features in 
these cabins. 

One system I am interested in is a solar water heater, to be used both 
for heating water for baths and also possibly providing warmth in 
certain parts of the house during the day or to a hot tub, etc.
 
I would like to use long coils of black hose as the primary collector. 

The problem is that in a cold climate, we are in NE Poland,  the water 
can freeze in the pipes during the winter. Most systems compensate for 
this by an elaborate and expensive dual (alcohol-water) system or an 
expensive insulated glass system. I would like to do with with a simpler 
system, and my idea is to place the absorption coils inside the house, 
in a sera (glass sun porch) attached to the south end of the house. The 
porch would not be heated as thoroughly as the rest of the house, just 
keep above freezing during the winter, unless the sun warmes it further.  

Another idea is to use as the primary heat absorbing coils, a black 
plastic hose that could handle the expansion that would occur when the 
water froze. In this case, only the pump would have to be protected from 
freezing by keeping it indoors. 

Further, I would like to pump the water in this system with a low 
voltage water pump that could be connected directly to a set of solar 
cells without any intervening battery. After all there is no sense 
pumping water when there is no sun. Does such a pump exist?

 Finally, is there any reason why the system shouldn¹t drain from the 
collector coils whenever the system shuts down, thereby providing 
further protection from freezing?

Using one, or a combination of these ideas, I would hope to be able to 
construct a very inexpensive system.

Can anyone suggest how much and what kind of hose would be required for 
such a system? Are there charts available for calculating this?

Can anyone recommend a good book on this subject?

Is there anyone who has any experience with this sort of system. What 
problems might you foresee? And does anyone know of a pump that could be 
driven directly from solar cells without intervening batteries or 
electronics?

Any comments would be appreciated.

Dale

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From: [email-masked] (Andrew MacMillen)
Date: Wed, 20 Mar 1996 07:41:42 -0800

In article <[email-masked]>, dale <[email-masked]> wrote:

> Finally, is there any reason why the system shouldn=B9t drain from the =
>>collector coils whenever the system shuts down, thereby providing =

That's a fairly normal practice for cold winter systems; some even have
auto drain systems.

>problems might you foresee? And does anyone know of a pump that could be =
>driven directly from solar cells without intervening batteries or =
>electronics?

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From: "Brian A. Rock" <[email-masked]>
Date: Thu, 21 Mar 1996 08:32:21 -0800

> I would like to use long coils of black hose as the primary collector.

In the U.S., black plastic tubing is not rated for hot water use.  It 
also becomes brittle over time when exposed to the sun.

There are many books available on the topic.  One that uses a practical 
approach is "How to Solarize Your House" by Dean and Hedden.  It was 
published by Scribners, but is out of print.  Maybe you can find it in a 
large library.

Good luck with your project.

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From: [email-masked] (Bo Atkinson)
Date: Thu, 21 Mar 1996 14:58:20 GMT

In article <[email-masked]>, dale ([email-masked]) writes:
>Sometime this summer I hope to begin building some log cabins at our....
>One system I am interested in is a solar water heater, to be used both....
>can freeze in the pipes during the winter. Most systems compensate for....
>Any comments would be appreciated.  Dale

Hello There,

I have happily heated domestic water using "black hose" (.5" or 1cm black ABS
plastic) coils for 21 yrs., here in Maine, USA, Lat  44+. Polands Lat 54+ may receive
less sun but appears to be a warmer climate growing zone, according plant books,
so low cost solar should work there. I wrote a detailed description of my low cost
solar/ water heating research in a journal called  "Home Power, issue #36, Aug-Sep
'93, (cover story) .... (HP Magazine, POB 520, Ashland, OR 97520, without recent
issues I don't know email address,  tel:916-475-0830).

This magazine has countless references regarding your interests, and last time I
checked, consecutive issues are available on CD ROM.

Essentially, I find that ordinary attics are remarkable solar collectors and filling an
attic with evenly spaced coils of tubing produce heated water.  I use preasurized cold
water from a deep well pump/ and house tank to supply water to collector... A
thermostatic valve on hot end controls hot flow to an insulated hot storage tank in
attic, (similar to car thermostat, but with lower temperature design). Hot water lines
distribute  water to house by gravity.  My attic happens to be a greenhouse as well,
and is dome shaped for wide solar angle. The condensation on cold end is trivial if
you can stand a few stains, (or catch with plastic sheet)...  5 months of the year 
produce unassisted, abundant hot water, (needing no futher heating).

Easy- vertical- drain- out   sounds desirable, but my oldest ABS pipe has already
sustained 15 years of freeze-thaw without draining, durring winter. Pipe which has
been damaged by over bending durring installation, or other abuse does develope
leaks. Joints between pipes  are also more susceptible to freeze damage. I spend a
few hours every spring on maintenance. But my less-abused sections of pipe never
leaked from frost damage, even with countless freeze thaw cycles durring 15
winters.  Freeze-thaw does remove mineralization build up, like "cadiovascular
plaque removal". Also unpreasurized water storage bleeds off those bad tasting
disolved gases, which makes hard, rural water taste better.  Avoid poorly made
iron tanks, they rust out.

One entertaining response I received was that this was simmilar to an already,   time
honored method for heating water on thifty ships in the southern Pacific Rim. It's too
bad free marketers so often overlook common sense, they dare not promote this low cost
approach to solar...  it's not even recognized by zoning codes, beware of tort laws!   

Bo Atkinson

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From: [email-masked] (Godfather)
Date: 22 Mar 96 00:45:52 -0500

> also becomes brittle over time when exposed to the sun.

something else you might consider is a highly conductive metal (such as copper)
as i have seen in many books.  just a thought.

jason

----------------

Jason E. Burk
Ball State University
First-year Architecture
email:  [email-masked]
http://bsuvc.bsu.edu/~01jeburk/index.html

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From: George <[email-masked]>
Date: Sun, 31 Mar 1996 08:50:18 -0800

> as i have seen in many books.  just a thought.

How about this,,,

Take a 6' by 6' piece of ground dig 4" deep
lay copper pipe up down up down in rows bent appropiately
fill with concrete
paint flat black
pry up end and place so sun can strike it
connect your hose to the copper tube

every inch of this would collect heat and disperse into the 
concrete and water passing through the slab would suck the 
heat out....

just a idea for CHEAP solar heat

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From: [email-masked] (Nick Pine)
Date: 31 Mar 1996 18:17:31 -0500

>How about this,,,

Very clever :-) I've never seen anyone suggest doing this sort of thing. 

>Take a 6' by 6' piece of ground dig 4" deep

6 x 6' seems a little small, and 4" seems a bit thick. How about 8 x 8,
and 2" thick? 

>lay copper pipe up down up down in rows bent appropiately

Seems to me that some sort of plastic pipe would work well here too,
with chicken wire on both sides...

>paint flat black

OK.

>pry up end and place so sun can strike it

That might be hard to do, as you describe it. Concrete weighs about
150 pounds per cubic foot, so a 6 x 6 x 4" slab of it would weigh
150 x 6 x 6 x 4/12 = 1800 pounds. Seems like this would be easier if you
put a layer of polyethylene on the ground first to act as a "mold release,"
or put a board or two underneath before pouring, to help pry it up.

And what about insulation or glazing? Seems like this would work
better with a transparent plastic cover, backed up to a straw bale/
EPDM rubber lined water tank.

Nick

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From: RICKY D VAN MATRE <[email-masked]>
Date: Wed, 3 Apr 1996 18:17:26 -0700

> or put a board or two underneath before pouring, to help pry it up.

That's easy, use a car jack to lift it off the ground.

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From: [email-masked] (Curlyindy)
Date: 6 Apr 1996 16:31:42 -0500

Yes, several commercially available benign tubings exist which would be
far more flexible and durable if not as efficient at conduction.

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From: [email-masked](Joe Hindorff)
Date: 1 Apr 1996 05:37:12 GMT

On Mar 31, 1996 08:50:18 in article <Re: Solar Water Heating>, 'George
<[email-masked]>' wrote: 
> 
>How about this,,, 
> 
>Take a 6' by 6' piece of ground dig 4" deep lay copper pipe up down up
down in  
>rows bent appropiately fill with concrete 
>paint flat black 
>pry up end and place so sun can strike it connect your hose to the copper
tube 
> 
>every inch of this would collect heat and disperse into the concrete and
water  
>passing through the slab would suck the heat out.... 
> 
 
George: 
 
You might want to check out Frank Lloyd Wright's experience with radiant
floor heating before you use this for a long term solution.  I think that
Mr. Wright used copper pipes in concrete floors in the 50's, and found that
they would only last a few years due to a chemical reaction between the
concrete and copper. 
 
Joe