Following the hottest summer on record for Europe, many modern buildings – especially those with a lot of glass construction – will require active cooling as well as heating, and by the most energy efficient means possible. The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology (FEP) has come up with a solution: the world’s first thermochromic coating on ultra-thin glass made by a roll-to-roll process that can be scaled for mass production.

The result will be smart windows that can regulate the heat input of solar radiation according to the weather. The invention could reduce the heating and cooling energy needs of buildings and even make mechanical blinds superfluous in future.

There are already some passive technology solutions such as SolarControl and Low-E coatings on the market, but they are not self-adjusting and lead to a permanent change in solar radiation levels. The thermochromic thin glass attached to buildings switches between transmissive and reflective states when it gets warmer than 20°C, or falls below that mark.

"The thermochromic layers change their transmission in the infrared range when a certain temperature is exceeded. The transmission in the visible range remains unchanged,” explains Professor Cindy Steiner, group leader at Fraunhofer FEP, in an article in Innovations Report. “This effectively blocks heat radiation in summer, reducing the need for air conditioning. In winter, heat radiation from the sun is allowed to pass through, resulting in savings in heating energy consumption."

The research team at FEP are working both new build and retrofit projects. For example, in the EU project Switch2Save, they are developing smart coating systems that use the effects of electrochromism (switching of energy transmission by applying a voltage) and thermochromism; and in Flex-G 4.0 they are working on retrofit solutions for existing buildings.