Colour changing roof
Using a phase changing polymer gel, the light energy transmission properties of the roofing material can be controlled. On a hot day the material becomes white, reflecting all wavelengths of light. On a cool day the material is transparent which allows our heat absorbing backing to conduct heat into the home.
The roofing system is based on a polymer gel which phase separates at a pre-determined temperature. Although most of the testing has been done with a gel that transitions around room temperature, they are able to select from a wide variety of transition temperatures ranging from approximately 0 to 100 degrees Celsius and beyond. When the polymer phase separates from the gel, the solution becomes a mixture of polymer and solvent and because the polymer and solvent have different refractive indices the mixture becomes strongly scattering (white colored). When the mixture cools below the transition temperature the polymer re-dissolves in the liquid and the solution is clear and colorless.
Source: thermeleon.comAdded: 27 May 2010