solar water heating

ok, so i'm trying to figure out the best way to heat water.

i created a box with 2x4 a 4x8 sheet of ply, a 4x8 sheet of insulation, and a 4x8 bi-wall polycarbonate. with a 100 foot hose wound about on the inside.(Picture below)

so my question is is this the best method.

instead of a reflective surface in the box should i have a black surface. or should i keep the reflective and change the transparent sheet for a black surface or should they both be black.

thanks for any help. Phil

I use solar hot water most of the year.
I would add a lot more tubing to the system and also run a manifold to ensure no air bubbles block the flow.

Flat plate solar hot water collector design

Thanks John, the flow is pretty good. its connected to a 400 GPH pump. i could add another 100 ft of hose with out any problem as there is plenty of empty space in there.

all i'm using this for is to heat up the water in the pond. not so much for the summer time, as being in the green house will do that, but gaining a little extra heat for the fish in the winter could make all the difference.

Might search for images for DIY pool heater.

The usual arrangement calls for a rather tight coil of tubing, but without the Polycarbonate. The polycarbonate would have to help on cooler days. I think you want the sun to hit either the tubing or fins attached to the tubing as heating up the air space will cause a loss of heat out though the polycarbonate and back in the form of hot air inside the collector cooling off.

That looks rather well built!
For recommendations on improving it, try the Biild It Solar website.