Posted by email@example.com on April 4, 2006, 4:32 pm
Later in the season I am going to build a shed by my 16x36 inground
pool and I'll put solar panels on the roof to heat our oh-so-cold pool.
I am desperate to try to get the pool up to temperature early this
season - it is in a very shaded spot and never gets above 75 even mid
summer. Yes, we do have a solar blanket which we leave on whenever we
are not using the pool.
How about this as a cheap interim solution...
Why can't I drop my sump pump in to the pool and attach it to 300' of
black hose. Lay the hose in a sunny area and then have it pump back it
to the pool.?
Is the flow rate just too low to make a difference to a 25,000 gallon
pool? I was thinking that I could at least take the 'chill' off it!!!
Anyone tried this?
Posted by Gary on April 4, 2006, 8:40 pm
300 ft of 3/4(?) OD hose has 19 sqft of surface area.
It might see (1600 BTU/sqft-day)(19sqft) = 30K BTU/day of radiation on a sunny
This will heat 25,000 gallons by:
dT = (30K BTU)(0.5efic(?))/((25K gal)(8.2lb/gal)(1.0BTU/lb-F) = 0.07F/day
The 50% efficiency might be on the optimistic side for a hose lying on the
ground? But, maybe not, if you keep the flow rate up -- the pool water might be
colder than the ground temp -- in which case it would gain heat from the ground
Could you run the water you pump over a large dark surface that drains back into
Maybe some black plastic tarp? You would have to work out some day to get an
even distribution of water -- maybe a PVC pipe with lots of holes as a manifold?
If you covered the 16X36 shed with pool collectors, its 30 times more surface
area than the hose -- I would think that will work much better :-)
"Build It Yourself" Solar Projects
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Posted by firstname.lastname@example.org on April 5, 2006, 1:31 pm
Thanks for the response...maybe I'll buy the solar collectors and just
lay them out on the ground where the shed will be going and plum them
Is it OK just to lay them on the ground or are they much more efficient
if I angle them towards the sun. I'm in NJ if that makes much
I was aiming for a 16x20 shed with just the south side covered in
panels giving me 8x20 of panels. The north side will not get much sun
as there are trees behind that area so it would only be in the sun
until 1:00-ish. I could design the shed to have a non-symmetrical roof
to maybe go for 12x20 of panels if I had to. Using your 19sq ft at 50%
efficiency = 0.07F per day I roughly calculated that 8x20 would raise
the temperate by .58 per day and 12x20 would give me 0.88 per day,
(assuming 50% efficiency which I assume is low for a commercial panel).
I'd have to say that 0.58 per day would be great - 4 degrees a week
would be a huge improvement!
Thanks again for the excellent response.
Posted by Gary on April 5, 2006, 7:27 pm
Horizontal is fine. In mid summer, horizontal is ideal.
They usually recommend a tilt of your latitude -15 degrees for best summer
collection, but for 40 deg lat, horz beats 25 degs in May, June and July by a
little bit. The 25 degree tilt does a little better than horz in Aril and in
Aug, Sept. But, in all cases the differences are pretty small.
I don't see any problem with laying the collectors out on the ground until you
get the shed up, as long as the ground is smooth with no sharp rocks or the
like. Does anyone else see a problem with this?
Rather than using my rough calc to estimate how much collector area you need,
I'd take a look here:
A couple of these sites have pool collector calculators that you can do an
estimate with. As the air temperature gets warmer, the pool collectors should
be quite efficient, since the collector temperature will be cooler than the air
temperature, and losses should be nil.
The Home Power article is quite good, and probably worth the price they charge
for the download.
Maybe you could take some pictures and notes as you go, and send them to
BuildItSolar to add as a project :-)
"Build It Yourself" Solar Projects
Posted by Solar Flare on April 5, 2006, 9:04 pm
Following your inspiration, I just ordered parts for my new "barn"
workshop building including 6 x 4x8' sheets of double walled
polycarbonate for the steep angle of the gambrel roof. I am at 44
degrees and the roof slopes 51 degrees. It will be a skylight for a
year until the piping and ceiling goes in.
One day I hope to formulate a parabolic trough thermal concentrator
for the output of this array to superheat fluid in winter shadier
months. A linear collector in the focus and two more tubes to possibly
run a self adjusting vertical tracker pneumatically or hydraulically
will be the next project on this vein. The mechanics of a 30' long
trough with swivel should be fun.
July by a
Aril and in
than the air