MM wrote:

On Sun, 22 Jun 2008 14:44:17 +0100, (Steve Firth)
wrote:

MM wrote:

I've
now stuck an advert in Freecycle for an old loft galvanised tank. (My
old one in Bucks would have been ideal.)

FFS, why not use a hot water cylinder?

"FFS"? Is this really necessary?

It makes more sense than using something that is not designed for the
job. I don't understand your approach to making a solar collector and
hot water store.

FWIW, my first experiment was with a 1 metre square single-panel
radiator. I painted the radiator with matt black using a high
temperature paint, and built an enclosure using aluminium extrusions and
aluminium sheet. I insulated the rear of the panel using urethane foam
and fitted a glass sheet to the front of the panel. Connections to the
top and bottom of the panel were done using hose tails.

This used as a thermal syphon or in conjunction with a 12V pump and 20W
solar panel set up to recirculate water provided enough hot water for
three people to shower and wash dishes/clothes. One a clear sunny day
the temperature of the water got high enough to soften the hose used and
to deform the first container I used. I changed to using a polypropylene
container which is the sort of "plastic" container referred to by
Hansen, which melts at 130°C and is therefore safeish to use with solar
hot water. Polypropylene is an expensive material and if I had to pay
for the container it would have been a silly price. The container had a
screw lid wich I fitted with a vent and I insulted the body of the
container.

If you don't have a tank with a lid, you will lose heat almost as fast
as you collect it by evaporation from the surface of the water. If you
don't have insulation the tank will cool rapidly. Your "serpent" is
woefully undersized and IMO you have done little or no research before
starting your project.