3 types of solar collectors.
The vacuum tube type works great. It can reach temperatures above 350° and becomes a good collector. The down side of it is when the snow and/or frost lands on the vacuum tube collector the sun has to warm it up to evaporate the frost, and with heavy snow you will have to clean it off the solar panels manually. If you remember to clean the panel if not this will loss you hours of solar collecting.
Home made solar collectors have a couple of problems: They are not sealed and filled with inert gas (argon gas) there by missing a key way of collecting solar heat. Improper way of winding the tubing inside the panel is another problem.
Flat panels commercially made are a great way to collect heat. You can set the collectors on most any type of roofing system. They also can be joined together for a greater Btu output. The maximum output will yield you any where between 50-70% of your domestic hot water. Having extra cash to go green is great but if you need this to be your main heating unit for hot water or limited location for hot water storage, this is not the system for you at this time I’ll check these systems out every couple of years for better results.