I'm an engineer student and I'm trying to build such a solar heating system that it is drum with two layers, inner one is a metal (aluminium alloy I'm thinking) water container and outer layer is made of polymer, with air gap in-between. When suns come out, it radiates through the polymer and on the metal layer, heats up the water inside. The air gap severs as an insulation. Could someone with more experience give me some advice on whether this will work? If you reckon this will work, then I will be looking for the material of the two layers The polymer will need to be transparent, low solar radiation resistance, high heat resistance and low conductivity The metal will have to have a shinny surface that absolves solar energy but a relatively low conductivity. Anyone that gives me any insight would be much appreciated.