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Solar Pool Heating

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Posted by Alysa on February 25, 2008, 4:27 am
 
Hello all,

I have been reading many many posts on the subject of solar pool
heating to decide how viable this really is for my future pool.  I
live in the South Orlando, Fl area and am hoping to extend my swimming
season with solar.  Growing up we had a pool that was outside and
unheated.  I recall that we weren't able to get in the pool until
pretty far in the swimming season since it took so long for the sun to
heat up the water to a reasonable temperature, think I recall the June
timeframe.  My husband also grew up with a pool that was the same way
and says he recalls they didn't get in until the pool was above 85
degrees but they were in Hollywood, Fl.  We currently have domestic
hot water and have been very happy with it, I also grew up with this
at my parent's.  Anyways I digress.  We are going to have 434 sq ft
surface area and I believe it was 25,000 gallons of water and it will
be in a screened enclosure.  The solar company that our pool builder
works with would be using the Heliocol panels that have the tubes that
the water runs through.  They guarantee that the pool will above 82
degrees from March through the end of November.  They would install 7
(4 X 12) panels minimum, we can choose 8 he said to make sure to limit
the recovery timre.  I am curious to hear from anyone that has solar
installed on their pool whether these timeframes are realistic,
whether this temperature is a reasonable expectation and if the pool
is truly usable at this temperature.  I saw back on January 25, 07
that donhdoyle@yahoo.com got the same type of system installed but I
missed it if he  posted any updates after this about the performance
of his system.

Now based on my experience with solar already over the years I am sold
on this.  Free heating for the pool, how can you turn this down??  Our
pool builder keeps trying to talk us out of it saying that we are not
going to be happy with the results.  He says we are going to have to
use the solar blanket (which you really should be using anyways), that
it is going to take us too long to recover with solar so it won't
extend our season by much and that if we plan to use the pool in the
evenings that we will quickly find the pool is going to get too cold
once the sun sets.  He keeps insisting that someone spending this
money on the pool shouldn't care about spending $0 in electric for 4
months should be a concern.  I don't think it is going to be only 4
months of the year, only $0 and why should I be wasting electricity
when it is not necessary and I can put my roof to work.


Thanks so much,

Alysa

Posted by nicksanspam on February 25, 2008, 1:35 pm
 


NREL says 990 Btu/ft^2 of solar energy falls on the ground and 1240, 610,
270, and 610 fall on south, east, north, and west walls on an average 57.5 F
January day with a 68.0 max and a humidity ratio w = 0.0078 pounds of water
per pound of dry air in Daytona Beach.


With a 25K/7.48/434 = 7.7' average depth? Or more surface or less water?


With a roof?


Lots of web site testimonials, but no cost or performance information...


Why not all year?


... 1 ft^2 of unglazed collector at an atn(1240/990) = 51 degree tilt (closer
to vertical) would receive sqrt(990^2+1240^2)^2 = 1587 Btu/day in January. At
temp T (F), it might lose 8h(T-63)1ft^2xU2 = 16T-1008, for a gain of 16(162-T)
Btu/day, so a 32'x32'x8' tall R1 room with vinyl curtains and greenhouse poly
film over a sawtooth roof (or something like the 106610C $K Sunburst Dome with
a $00 10-year clear vinyl cover at http://www.farmtek.com ) might collect
0.9x32x8(1240+610+270+610)+8x4x12x16(162-T) = 24h(T-57.5)1024ft^2/R1 and
keep the pool T = 98.9 F.


Not required, with an airtight enclosure, eg rolldown vinyl curtains.


Tell him the pool's time constant would be RC = 25000x8.33/1024 = 203 hours,
approximately, so it might cool from 98.9 to 57.5+(98.9-57.5)e^(-16h/203h)
= 95.8 over 16 hours at night.


With no cover and no vinyl curtains, keeping the pool 85 F with a pool vapor
pressure Pw = e^(17.863-9621/(460+85)) = 1.233 "Hg and an air vapor pressure
Pa = 29.921/(1+0.62198/w) = 0.371 "Hg would require about 24hx100(Pw-Pa)434
= 900K Btu/day, ie 30x900K/3412 = 7902 kWh/month worth $90 at 10 cents/kWh.

Maybe you should find another builder :-)

Nick


Posted by Madhav \"Mr. Nepal\" Acharya on February 25, 2008, 4:09 pm
 On 25 Feb 2008 08:35:43 -0500, nicksanspam@ece.villanova.edu wrote:


No, ok alright ok no is 98.8, you wring, i calkulate
--
skype:mranep
cell:813-610-2978; work:813-386-4500; work2:813-915-1663
Motto: Why face the world myself when my wife's skirt, it is so dark and
comfy under it?
Proclamation: "A man can have sex with sheep, cows and camels and so on.
However, he should kill the animal after he has his orgasm. He should
not sell the meat to the people in Nepal; Ok I did so beat me with a
Yeti dick.




Posted by Alysa on February 28, 2008, 4:56 pm
 On Feb 25, 8:35 am, nicksans...@ece.villanova.edu wrote:

Ok I must be completely off on the gallons, could have sworn that's
what was discussed.  I know my sq ft of surface area is correct.  But
it will be a sports styled pool that is 3 1/2 feet on each end and 6
feet in the middle which made it hard to calculate the gallons from my
end.  I will double check on this.

Well I actually hadn't thought about a roof until I started reading
the posts in the group here.  It was just supposed to be screening,
not even sure my HOA would allow a roof but now I am considering.


These panels are apparently the reason that they offer the guarantee,
the owner of the company insists these perform significantly better
than the regular panels, but I would have been game to do it with the
regular panels also.

He explained that with the screen enclosure (w/o roof or vinyl
curtains) that the solar could only be guaranteed to heat the water 15
degrees above the temperature outside.  At the time I had looked at
the residential enclosures from Four Seasons & Tempo and the cost was
so outrageous that I abandoned the idea.  Didn't realize it could be
done more cost effectively and I will have to look into this.


This is very impressive.


This is also what the solar company told us.  The pool company pointed
out to me that the solar guy has 11 panels on his own pool and
religiously uses the solar blanket.  I am not opposed to using it,
just not sure how required it was.

This is pretty much what my point to the pool builder was also.  He
has a heat pump on his pool and thinks it is the greatest thing in the
world, but points out that the solar company keeps trying to convince
him to consider trying solar on his own pool.  Well I think this
solidifies this for me I was sold on the solar all along.  Thank you
Nick for all the help.


Posted by Madhav \"Mr. Nepal\" Acharya on March 8, 2008, 9:08 pm
 On Thu, 28 Feb 2008 08:56:04 -0800 (PST), Alysa wrote:


ok alright what answer he wrng?
--
skype:mranep
cell:813-610-2978; work:813-386-4500; work2:813-915-1663
Motto: Why face the world myself when my wife's skirt, it is so dark and
comfy under it?
Proclamation: "A man can have sex with sheep, cows and camels and so on.
However, he should kill the animal after he has his orgasm. He should
not sell the meat to the people in Nepal; Ok I did so beat me with a
Yeti dick.




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