This is a nice simple idea from Deane that appears to work very
well.
Details:
I had been heating my above ground 24 foot x 4 foot swimming pool in NH with
some eight 4x10 roof mounted pool collectors. The roof faced west and had a 20
degree slope. Needless to say early mornings and spring output weren't great.
One day I decided to paint the vertical south exterior wall of the pool
black. Boy did that help. First the wall was exposed to the April sun
much more directly and throughout the day. Second the heat transfer to the
pool was great because the sun struck the black metal pool wall directly
and the only thing between the heated wall and the water was the very thin
20 mill pool liner. In spring the object is to get the water up from
freezing so the pool wall barely runs above ambient air during the day
resulting in near zero loss back to the air.
In my case I doubt the addition of a glazing would help much although it
might be worth it as the pool temp rises to swimming level.
Of courses the losses were the same. In summary the cheap black paint
extended the season 3 weeks on either end.
Imagine the effect if all above ground pools came with black exterior walls.
Even better if they were selective.
Further in summer the south wall of the pool got less sunlight so didn't
overheat.
An estimate for the heat gain for the black wall:
Use 60 days of which 30 are sunny ( say May and September which actually
have exactly 30 days!) . About 6 hours per day at 90 efficiency, so
330 btuh x.9 eff x 6 hours x 60 days x .5 sunny = 60000 btu per
sq.ft, or about 1 gal of fuel oil or 1 therm of gas burnt in the
typicallly inefficient pool heater or about $3 for each sq.ft.
A 24 x 4 pool has about 100 sq.ft of Southish wall so worth about $300
per year.
Note I had thought the original blue wall of the pool was reasonably
absorptive, but the black really improved performance. So, maybe the
gain was half that. a reflector or white stone around the south ground
might add 50%
Deane
September 12, 2011
You can ask Deane questions at: deaneg AT hotmail DOT com (change AT to @
and DOT to a period)
Another suggestion from Deane:
Another suggestion is that for pools at latitudes above
25, it is often a good option to mount the panels vertically for the
aforementioned reasons of facing the sun more directly in April and May and Sept
and October than the typical 5/12 pitch roof. I have 4 vertical panels on my
in ground pool system in FL ( my above ground system is in NH) . They are
also more sheltered from the wind ( which really counts on pool panels) and take
advantage of ground reflection from concrete or seashells. In the north snow
helps with that. I believe I get more output from the 4 wall panels than the 6
roof panels in January when it is most needed.
While Deane painted his pool wall black, which is most efficient, any DARK
shade would work nearly as well.
