Sustainability and waste reduction. These are the objectives behind the new window coverings developed by researchers from Fraunhofer, the German organization specializing in technology development, as part of the “Switch2Save” project. These “smart” coatings for glass windows darken in the sun and use electrochromic and thermochromic materials that react to electricity and heat. In buildings with large glass facades, it prevents the rooms from overheating due to solar radiation, thus reducing the demand for energy-intensive air conditioning.
According to the German Environment Agency, buildings are responsible for around 30 percent of the country’s CO2 emissions and 35 percent of its final energy consumption. These coatings can be a forward-looking choice to reduce the impact on the environment.
“The electrochromic coating is applied to a transparent, conductive film which can then be “switched on”. Applying an electrical voltage triggers the transfer of ions and electrons, which darkens the coating and tints the window. On the other hand, thermochromic coating works passively. When a certain ambient temperature is reached, it reflects the heat radiation of sun”, explains Dr. Marco Schott, Group Manager of Electrochromic Systems at Fraunhofer ISC.
With electrochromic elements, sensors can be used to measure factors such as brightness and temperature, sending the results to control systems. This sends a current or voltage pulse to the conductive film, triggering the window to darken. The surface of the glass gradually darkens whenever the temperature or brightness level becomes too high. This stops rooms from becoming overheated and reduces the need for air conditioning, which is particularly useful in sunnier climes and buildings with large, glazed façades. It also serves as anti-glare protection on sunny days. On cloudy days and in the evening the windows will be kept in bright state.
