Subject: Solar pool heating

From: "Serv Adm" <[email-masked]>
Date: Wed, 9 Oct 1996 15:59:31 GMT

I built last year a solar pool heather with 6 4'x8' black Coroplast sheets
(192 sq. fo.) on my roof. Water going out from the pool filter is going
thru
theses panels and going back to the pool. I want to evaluate the efficiency
of my system. Could someone help? Here is a little more info: there are
6000 litres
of water circulating thru the panels in an hour. Water coming out from the
system
is 2 degres (celcius) higher than water going in the panels. How much BTU
my
system is developping?

I live near Montreal (Quebec) Canada.

Philippe Lavoie
[email-masked]

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From: [email-masked] (Andrew McKegney)
Date: Thu, 10 Oct 1996 18:13:04 GMT

>[email-masked]

96:10:10

Dear Philippe

Did you want an answer in US, Imperial, or SI units !<)

Before showing you the calculation, I would like to point out that the
accuracy of both the flow rate through the panels and the temperature
rise across the panels is critical to get an accurate performance
estimate. Being off by one degree C. can represent a 33% - 50%
difference in performance!

First the amount of heat you are collecting = mass flow x speciific
heat x temperature difference.

>From  your numbers (using Imperial units) this becomes

13200 lbs/hr x 1 btu/lb F x 3.6 degrees F. = 47,520 BTU/hr

The estimate of the amount of solar energy the panels are seeing can
only be a guess, because I don't know the angle at which they are
facing the sun, or the time of day. However, making the assumption
they are facing more or less South and at an angle within 30 degrees
of normal to the sun, and that it was a sunny day when you took the
measurements, the calculation would be: area of solar collector x
average insolation of sun (energy of sunshine)

Which becomes:  6 (panels) x 32 ft^2  x 300 BTU/ft^2 hr

Which equals: 192 x 300 = 57,600 BTU/hr

The efficiency of  your solar system is then  output/input =
47,520/57600 = 82.2 %

This is a damn fine number!

Many commercial products would be hard pressed to match this
performance. The design you have is actually the most common of the
commercial products using (custom) extrusions similar to coroplast. I
tried build panels from this material 22 years ago. I could never get
the headers to stick to the board permenantly. Most coroplast is not
designed for long term full-sun exposure. It will likely harden and
become vulnerble to cracking in a couple of years. Until then enjoy
your system and  (note to a fellow Canadian) don't let it freeze.

Andrew McKegney C.E.T.