© EControl-Glas

Schoolchildren in the Bavarian town of Cham always keep their cool – even when the sun is beating down on their classrooms. The classroom windows are made of electrically switchable EControl® glass, which, depending on the season and the time of day, can be rendered transparent or partially opaque by applying a small electric current. This system guarantees complete control at all times and eliminates the cost of running an air-conditioning system. So even in summer, the rooms do not overheat in direct sunlight.

The window panes, with their variable light and solar energy transmission properties, were developed by EControl Glas GmbH & Co. KG, a company based in Plauen, Saxony. Essentially, smart windows are based on the same double glazing principle as conventional solar control or thermal glazing. The difference is that the outer pane is made of a controllable electrochromic composite, behind which there is an ion-conducting polymer film. The cavity between the panes is gas-filled, and the inner pane has a thermal insulation coating. The ion-conducting polymer film turns blue when charged with an electric current, allowing both light and heat transmission to be regulated either in five preset stages or continuously. The change of color is triggered by the release of electric charges that provoke a visual reaction in the coating. The electrode layer consists of nanomaterials with a thickness of 20 to 50 nanometers.