Electrochromic glass essentially uses electric charge to switch a window from allowing sunlight in to blocking it out. Some have estimated that such “smart windows” could cut lighting needs by about 20 percent and the cooling load by 25 percent at peak times.
Now researchers at the University of Texas Austin have found a way to make them even better. They developed a novel nanostructure architectcure for electrochromic materials that enables a highly selective cool mode and warm mode—something thought to be impossible a few years back.
In research published in the journal Nano Letters, the University of Texas researchers along with scientists at Lawrence Berkeley National Laboratory were able to get nanostructured electrochromic materials to control 90 percent of the near-infrared (NIR) light and 80 percent of the visible light. What’s more, it only requires a few minutes to switch between these two modes, whereas previously reported materials took hours to make this transition.
“We believe our new architected nanocomposite could be seen as a model material, establishing the ideal design for a dual-band electrochromic material,” said Delia Milliron, a professor at the University of Texas who led the research, in a press release. “This material could be ideal for application as a smart electrochromic window for buildings.”
The researchers were able to achieve the faster switching by creating a porous interpenetrating network in a two-component composite material. The architecture of this network created channels, through which electronic and ionic changes could propagate.
The next step in this two-component nanocomposite material will be to find a cheaper and easier way of producing it. However, the researchers are also looking into achieving the same effects but with a material that uses a single component.
Toward that end, Milliron and her colleagues demonstrated that coating containing only doped titania nanocrystals allowed for dynamic control of solar radiation transmission. They published those results in the Journal of the American Chemical Society.
So, in practice, it would be possible to control the window by putting it in the so-called “warm mode” so that the visible light could be blocked while the NIR light could enter. This would be very useful in the winter when you want the heat of the sun without being blinded by it.
“We believe our deliberately crafted nanocrystal-based materials could meet the performance and cost targets needed to progress toward commercialization of smart windows,” added Milliron. Which is good for her, as she’s the chief scientific officer and cofounder of electrochromic materials startup Heliotrope Technologies.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.