Smart Material for Efficient Solar Absorption without Overheating

Solar thermal collectors are used to produce hot water and contribute to home heating. During colder seasons all the energy they absorb is helpful, but in summer thermal collectors become overheated and deliver excess heat. Until recently, this overproduction has remained an unresolved problem that can even damage facilities. A team of EPFL researchers has developed a smart material that changes its properties depending on temperature. In the case of overheating during summer, this new material would allow the collector to get rid of excess energy by radiating it. The innovation of this project is the successful combination of an optical selective effect with a thermochromic function - the color reacts and changes with heat, a phase change that occurs at 68° C. The new material developed at the laboratory enables the efficient absorption of solar energy while reducing the impact of overheating.

Transcript

00:00:04 we developed a new material for solar thermal collectors which changes optical properties as a function of temperature usually a solar thermal collector should produce heat for domestic space heating and for hot water production now even in Switzerland we can have several year at times a year the situation when this collector and the whole system it gets too hot this is the situation of

00:00:29 overheating now we want to create an intelligent material which allows us to radiate excesses what we combined is the function of thermochromic behavior and optical selectivity a good soul absorber coating should absorb the solar radiation in the wavelength range between 250 nanometers to two thousand five hundred nanometers fortunately the infrared radiation is not in the same

00:00:55 spectral range this is around eight micron so the solar collectors surface would radiate in the mid infrared range now we can create a surface which is a black body for the solar range and a mirror for the infrared radiation we developed this material for solar thermal collectors however we envisage also other applications it could be on smart windows and in general on smart

00:01:22 building envelopes