By Laura Ojea
There are other alternatives, such as installing awnings or drawing curtains or blinds in sales, that can block the entry of the sun and the heat it produces, but a group of engineers from the Massachusetts Institute of Technology has launched an alternative solution. These are photosensitive windows that self-darken with light.
So-called “self-shading” windows have coatings that can change color when there are light changes or when someone flips a switch. There are a few different varieties of these materials - some are photosensitive, which means that they change when the light around them changes, like some brands of glasses that are made from this material. Others are thermochromic, which means that they change with temperature.
Then there are the materials that change when an electrical charge is applied, and they are useful because they can be changed on demand. Some companies market "privacy windows" that can be turned from transparent to frosted glass with just a switch.
But these electrochromic windows have some limitations, according to Mircea Dinca, a professor of chemistry at the Massachusetts Institute of Technology. They can take several minutes to change color and current designs also cannot darken to a totally opaque shade. For this reason, Dinca ensures that it has developed a design that can darken completely at a much faster speed.
Electrochromic windows are made up of several layers of different compounds. There is an electrochromic layer itself and a complete layer of the ions. When voltage is applied, ions move within the electrochromic layer and react with the material, forcing the color to change. This part of the process is what slows down the transition.
But the new design they propose uses organometallic scaffolds, which can transmit ions much faster. The team has also been able to combine two layers of different colors - green and red - that combine to make a shadow almost completely impossible to see through, and in addition, they have worked with different configurations so that they can be produced. various shades.
The research has been funded by the Masdar Institute, based in the United Arab Emirates, and the United States Department of Energy.
Solutions like these could greatly reduce the demand for air conditioning, which is currently booming around the world, as countries become prosperous enough to provide these systems. Americans spend $ 11 billion a year on air conditioning alone in addition to the 100 million tons of carbon emissions that are emitted into the atmosphere from extra electricity consumption.
In addition, the use of air conditioners can raise the outside temperature, contributing to the phenomenon known as the urban heat island effect. This creates a kind of self-boosting cycle, in which the heat from the air conditioners is released, temperatures rise and therefore the need to use more air conditioning.
The Energy Newspaper