Window Material Can Let in Sunshine While Blocking Heat
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It's a hot summer day and you
want to block the heat coming into your home through the windows. But lowering
your blinds means less light, so you will be forced to turn on a lamp.
What if you could block the heat without blocking the
sunlight?
Researchers have developed a material that can do just that.
And, for those living in colder environments, this material can also
switch modes to block the sunlight (and the glare it sometimes comes with)
while still letting in the heat. By using this material in
"smart windows", you could reduce home energy use by taking full
advantage of both the heat and the visible light provided by the sun each day.
The material is a type of dual-band electrochromic material.
"Dual-band" refers to the two types of nanocrystals contained within
the material itself. In this case, the first nanocrystal allows you to
block visible light while the second targets heat-producing infrared light.
"Electrochromic" means that you can flip between light- and
heat-blocking modes using a jolt of electricity.
This material was first described by
researchers, including University of Texas Chemical Engineering Professor Delia Milliron, in an article in
Nature in 2013. This month, Milliron and her team
published a new article in the Journal of the
American Chemical Society, which explores how an advanced
version of this material could be built into a film for use on windows.
According to this paper, a window coating containing a
single component — doped titania nanocrystals - can selectively block visible
light or infrared radiation. It can also switch from heat- to light-blocking
mode using a weak jolt of electricity in a matter of minutes (previous versions
of the material could take hours to switch). All told, this material can block
up to 80% of visible light or 90% of near-infrared light.
According to Milliron, these “advancements show that
sophisticated dynamic control of sunlight is possible.” Furthermore, Milliron
and her colleagues “believe [that their] deliberately crafted nanocrystal-based
materials could meet the performance and cost targets needed to progress toward
commercialization of smart windows.”
Melissa C. Lott is an engineer and
researcher who works at the intersection of energy, environment, technology,
and policy
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