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solar trickle or full solar pipes?

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Posted by dold on July 9, 2012, 9:57 pm
 
I've been thinking of using a patio cover as a solar water heater for my
pool.
I just want shade, not a complete cover.
The cover would be about 25'x14'.  I have a 32x12 pool 3.5 feet deep.

I thought I might run some 3/4" black PVC on the 25 foot length, which
could give me 30-50 parallel runs.  but I wonder which of three possible
water flows would be best:

control the flow rate at the uphill end, so the tubes are partially filled
control the flow rate at the downhill hend so the tubes are filled.
cut the tubes in half and have an exposed trickle flow to the lower end.


--
Clarence A Dold - Hidden Valley Lake, CA, USA  GPS: 38.8,-122.5

Posted by Ecnerwal on July 10, 2012, 12:35 am
 
wrote:


Clear tubing would be better at collecting heat to the water than black,
I think. Black will probably hold up longer though, so it might well be
better in the long run. Put up some 50% or 70% or 90% greenhouse
shadecloth for your awning, depending how shady you want it to be, and
run the tubes on top of it.

Full would be best, trickle would be better if your structure can't
support the weight of full tubes (or use smaller, full, tubes) and
cutting them in half is counterproductive - evaporative cooling and loss
of water, not to mention a huge pain to cut. Plastic does not conduct
heat all that well, so if you have a trickle of water in the bottom of
the tube, and the sun is heating the top of the tube, you'll get poor
transfer of heat to the water.

Parallel flow can be tricky. In theory you balance the input and output
and the flows balance - practice and theory are the same in theory, and
often different in practice.

--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.

Posted by v8z on July 10, 2012, 1:43 pm
 

I would recommend a closed system, with a horizontal manifold at top and
bottom, and the collector tubes running vertically between them.  The
manifolds could be constructed of short lengths of pipe combined with T's.
Feed from the bottom and collect at the top.  Fully fill the tubes, and
control flow so at full sun, the tubes feel just cool to the touch.  That
way you know you're extracting as uch heat as is being absorbed.

Lots of ideas and information on DIY solar pool heaters can be found at
http://www.builditsolar.com/Projects/PoolHeating/pool_heating.htm



Posted by dold on July 16, 2012, 3:33 pm
 

No trees.  
The location would be the center of the U shaped house
http://cdold.home.mchsi.com/Solar-generation_files/image001.jpg  The cover
would be shading the windows visible through the arches.


I've looked at BuildItSolar several times, and I should probably just pick
a style and do it.


--
Clarence A Dold - Hidden Valley Lake, CA, USA  GPS: 38.8,-122.5

Posted by dold on July 16, 2012, 3:38 pm
 
No trees.  The cover would be shading the windows visible in the center of
the u shaped house
http://cdold.home.mchsi.com/Solar-generation_files/image001.jpg


I have visited BuildItSolar several times.  I just need to go ahead and do
something.  


--
Clarence A Dold - Hidden Valley Lake, CA, USA  GPS: 38.8,-122.5

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