What keeps the pipes from freezing and bursting on cold no sun days? Do you use a circulation pump to keep the water moving?

Which kind of glass did you use dis you use normal glass or plexiglass

I made a water heating solar system from scratch and it provides about 80% of my hot water.

how much a single unit will cost in Pakistan on delivery? and how much is the single unit production cost?

If you want to support home heating in the day time as I have enjoyed for 12 yrs from solar thermal, only evacuated tube heat pipes combined with a thermal store will work. Flat plate is old out dated boxes of copper absorber plates with a peice of glass that loses the heat. The latest heat pipes have a condensor which stops the hot water tank heating up above 80c, as long as its a vented thermal store. This allows the over sizing of the tube collectors while keeping the thermal store below 300 Litres. Those with a heating need, linked to a back up boiler can then use 100% of day time solar heat into the thermal store direct and then to the radiators or underfloor heating. In the summer months, no worries about over heating the tank, as there is no closed system and no need for replaceing glycol every 1-2 yrs, due to overheating the fluid.

Have you tried Thermodynamic Solar Panel?

No rigid back on the unit

IF you want to make it by yourself just go to InpliX page.