Fraunhofer Institute for Electron BeamWindows with switchable properties
Over a period of four years, Fraunhofer FEP has coordinated the Horizon 2020 project Switch2Save (Lightweight switchable smart solutions for energy saving large windows and glass facades).
In this project, ten partners from seven European countries came together to develop new approaches for energy-efficient office buildings. The solutions aimed to equip the windows of existing buildings with surfaces that can adapt their properties to external environmental influences. The transparency can be changed so that as much of the incoming sunlight as possible reaches the interior in order to support the heating in cold weather. In the opposite case, on warm summer days, the light is largely prevented from passing through the window, which in turn helps to reduce the load on the air conditioning system. The researchers always kept in mind that the coating solutions can be applied to lightweight and flexible substrates. This means that the coated films can later be easily integrated into existing windows.
This approach was flanked by theoretical considerations. Building simulations for various climatic conditions present in Europe revealed that the new solutions are particularly important for cooling interior spaces. This means that they are primarily important in southern countries, even outside Europe. However, highly insulated buildings with large window areas also have a high cooling requirement in Central and Northern Europe, which is why switchable coatings can also make a contribution to energy efficiency there. This is becoming increasingly important, particularly against the backdrop of global warming.
The Fraunhofer FEP was primarily responsible for the thermochromic coatings. This special variant of switchable windows does not require any additional controls. It reacts solely to the ambient temperature. Here the Fraunhofer FEP has made great technological progress. For the first time, this sophisticated technology has been successfully implemented as a continuous roll-to-roll process. Thanks to sophisticated sensor technology, it was possible to draw conclusions about the subsequent properties of the coatings during the process. Even though thermochromism did not make it into the final demonstrators, important insights were gained into application scenarios and remaining technical challenges.
