Everything is smart in today’s world. Smart phones, smart watches, smart televisions, even smart light bulbs. With the advent of Amazon’s Alexa and other networked devices, our entire homes may soon be “smart” as well. For a full smart house, you’ll need smart windows, too! And guess what technology is behind certain types of smart windows? Polymers!
Windows are notorious energy wasters, yet most buildings demand large and plentiful windows; how many buildings have you seen that have entire glass exteriors? This leaves a conundrum: We love the sunlight and views, but have significantly higher heating and cooling costs as a result. Tinting is an imperfect solution, because the windows must maintain some level of transparency, and static tinting is only feasible if the light itself is static, and sunlight is not).
Dynamic tintable windows, or smart windows, are thus a great compromise. According to one article1, “Presently, state-of-the art commercial electrochromic windows seem most promising to reduce cooling loads, heating loads and lighting energy in buildings, where they have been found most reliable and able to modulate the transmittance up to 68 percent of the total solar spectrum.” Electrochromic windows–made from polymers–can change sunlight allowance in response to either an electrical current or changing environmental conditions, basically able to change their tint with the flip of a switch. These allow for transparency while accounting for energy loss or gain by the large glass surface area.
What does it mean for a window to be electrochromic? Electrochromism is when a device can reversibly change its color, triggered by an external energy source. This is a redox reaction. In redox reactions, an electron transfer occurs, so one chemical species is oxidized by losing electrons, and one chemical species is reduced by gaining electrons. This change can cause changes to the species that results in a color change. In the electrochromic windows, this color change persists until a change in the external energy source occurs. Hence, flicking a switch to send electricity through an electrochromic window pane allows the user to control darkening or lightening of a tint.
Electrochromic windows are made with several layers of glass, conducting fluid, ion conductors, electroactive layers, and more conducting film. The electroactive layers, usually made of electrochromic conducting polymers, are what cause the tinting.
Polyaniline, for example, is a conducting polymer which transforms from transparent to violet when in a redox reaction. This polymer in particular is one of the most tested electrochromic materials because of its low cost and ease of processing. Further, polyaniline and hybrid polymers easily change colors when exposed to the proper catalysts, with high electrochromic contrast and fast response times. All of these traits make them ideal for smart windows.
At SGS PSI, we have experience working on a variety of window projects — to include defects and failures. If you are in need of expert analysis, please reach out!
Polymers are the basis of our world, and tapping into their power helps us step into the future. It’s all about using science to create a better world for everyone. Pretty smart, huh?
1 Baetens, R., Jelle, B. P., & Gustavsen, A. (2010). Properties, requirements and possibilities of smart windows for dynamic daylight and solar energy control in buildings: A state-of-the-art review. Solar Energy Materials and Solar Cells, 94(2), 87?105. doi:https://doi.org/10.1016/j.solmat.2009.08.021