Solar Hot Water Panel – Home built

I have been playing around with a thermosiphoning solar hot water panel. A thermosiphoning panel is usually at ground level and uses the principal that hot water rises and cold water sinks to push the water upwards into a tank instead of an electric pump. All of our solar hot water panels are roof mounted and require an electric pump to circulate the water so I thought it was about time to give the thermosiphoning thing a whirl.
We have used an old window that was removed from the kitchen and painted it black.
Black painted plywood is the backing that the black hose is mounted on.
The hose used is cheap black hose from a hardware shop with lots and lots of elbow/corner connectors. The hose is cut into lengths and the connectors allow it to turn corners easily.
There has been a hole drilled at diagonal corners, one for the cold inlet at the bottom (side) and one at the top(side) for the hot outlet which will in theory go into a hot water cylinder.
As this hot water is only being used to circulate through the biodigester there is no cold feed but if it was hooked up to a hotwater cylinder with a cold inlet tap then you could have a brass non return valve on the cold inlet so only cold water can go into that hose.
Call me stupid but I cannot get the photo of the cold water return to rotate so it looks a bit odd and complicated.
Technically the solar panel should be more at ground level as at the mo the hot water needs to go downwards which negates the theory of thermosiphoning. Hopefully it might give you some ideas for stuff lying about the place though.
Cheers Carolann