Tag Archives: Guillermo Garcia

Smarter ‘smart’ windows

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It seems to me we may have to find a new way to discuss ‘smart’ windows as there’s only one more category after the comparative  ‘smarter’ and that’s the superlative ‘smartest’. Lawrence Berkeley National Laboratory (Berkeley Lab), please, let’s stop the madness now! That said, the Berkeley Lab issued an Aug. 14, 2013 news release  (also on EurekAlert) about it’s latest work on raising the IQ of smart windows,

Researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have designed a new material to make smart windows even smarter. The material is a thin coating of nanocrystals embedded in glass that can dynamically modify sunlight as it passes through a window. Unlike existing technologies, the coating provides selective control over visible light and heat-producing near-infrared (NIR) light, so windows can maximize both energy savings and occupant comfort in a wide range of climates.

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Milliron’s research group is already well known for their smart-window technology that blocks NIR without blocking visible light. The technology hinges on an electrochromic effect, where a small jolt of electricity switches the material between NIR-transmitting and NIR-blocking states. This new work takes their approach to the next level by providing independent control over both visible and NIR light. The innovation was recently recognized with a 2013 R&D 100 Award and the researchers are in the early stages of commercializing their technology.

Independent control over NIR light means that occupants can have natural lighting indoors without unwanted thermal gain, reducing the need for both air-conditioning and artificial lighting. The same window can also be switched to a dark mode, blocking both light and heat, or to a bright, fully transparent mode.

“We’re very excited about the combination of unique optical function with the low-cost and environmentally friendly processing technique,” said Llordés, a project scientist working with Milliron. “That’s what turns this ‘universal smart window’ concept into a promising competitive technology.”

Here’s the specific technology that’s been developed, from the news release,

At the heart of their technology is a new “designer” electrochromic material, made from nanocrystals of indium tin oxide embedded in a glassy matrix of niobium oxide. The resulting composite material combines two distinct functionalities—one providing control over visible light and the other, control over NIR—but it is more than the sum of its parts. The researchers found a synergistic interaction in the tiny region where glassy matrix meets nanocrystal that increases the potency of the electrochromic effect, which means they can use thinner coatings without compromising performance. The key is that the way atoms connect across the nanocrystal-glass interface causes a structural rearrangement in the glass matrix. The interaction opens up space inside the glass, allowing charge to move in and out more readily. Beyond electrochromic windows, this discovery suggests new opportunities for battery materials where transport of ions through electrodes can be a challenge.

I notice they’re using indium, one of the ‘rare earths’. Last I heard, China, one of the main sources for ‘rare earths’, was limiting its exports so this seems like an odd choice of material. Perhaps now they’ve proved this can be done,  they’ll research for easily available substitutes. Here’s a link to and a citation for the published paper,

Tunable near-infrared and visible-light transmittance in nanocrystal-in-glass composites by Anna Llordés, Guillermo Garcia, Jaume Gazquez, & Delia J. Milliron. Nature 500, 323–326 (15 August 2013) doi:10.1038/nature12398 Published online 14 August 2013

Finally, the researchers have provided an illustration of indium tin oxide nanocrystals,

Nanocrystals of indium tin oxide (shown here in blue) embedded in a glassy matrix of niobium oxide (green) form a composite material that can switch between NIR-transmitting and NIR-blocking states with a small jolt of electricity. A synergistic interaction in the region where glassy matrix meets nanocrystal increases the potency of the electrochromic effect. Courtesy Berkeley Lab

Nanocrystals of indium tin oxide (shown here in blue) embedded in a glassy matrix of niobium oxide (green) form a composite material that can switch between NIR-transmitting and NIR-blocking states with a small jolt of electricity. A synergistic interaction in the region where glassy matrix meets nanocrystal increases the potency of the electrochromic effect. Courtesy Berkeley Lab

The latest in smart windows

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At last there’s a new development in smart windows giving me fresh hope that I will see these in my lifetime. From the Sept. 6, 2011 news item on Nanowerk,

Researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have unveiled a semiconductor nanocrystal coating material capable of controlling heat from the sun while remaining transparent (“Dynamically Modulating the Surface Plasmon Resonance of Doped Semiconductor Nanocrystals”). Based on electrochromic materials, which use a jolt of electric charge to tint a clear window, this breakthrough technology is the first to selectively control the amount of near infrared radiation. This radiation, which leads to heating, passes through the film without affecting its visible transmittance. Such a dynamic system could add a critical energy-saving dimension to “smart window” coatings.

“To have a transparent electrochromic material that can change its transmittance in the infrared portion of sunlight is completely unprecedented,” says Delia Milliron, director of the Inorganic Nanostructures Facility with Berkeley Lab’s Molecular Foundry, who led this research.

These kinds of coatings offer substantive energy savings. A lot of people don’t realize that buildings account for approximately 40% of the carbon emissions in the US. A smart window could theoretically lower the use of air conditioning and lighting by as much as 49% and 51% respectively according to the authors of the news item. I have seen similarly high numbers elsewhere so I am inclined to believe them.

Here’s what I think is the nifty part,

“Traditional electrochromic windows cannot selectively control the amount of visible and near infrared light that transmits through the film. When operated, these windows can either block both regions of light or let them in simultaneously,” says Guillermo Garcia, a graduate student researcher at the Foundry. “This work represents a stepping stone to the ideal smart window, which would be able to selectively choose which region of sunlight is needed to optimize the temperature inside a building.”

And then there’s the robot,

“Our ability to leverage plasmons in doped semiconductors with a very sensitive switching response in the near-infrared region also brings to mind applications in telecommunications,” Milliron adds. “We’ve also brought this synthesis into WANDA, our nanocrystal robot, which means we will be able to provide materials for a wide variety of user projects. “

I don’t see anything which indicates when this might be commercially available.

This latest development reminded me of Switch Materials, the Canadian smart window company that’s located in the Vancouver region. I last wrote about them in my May 14, 2010 posting and thought I’d check them out again. They have a new look on their website and a number of headings for different categories of purchasers such as architects, manufacturers, owners, etc. There’s also a list of the various media outlets that have featured the company. Strangely, there’s no mention of any customers and other than a very general description heavily weighted towards the advantages of the technology I was not able to find much detail about the technology. That’s also true of the news item but I expect more from a company website, especially a company offering an emerging technology. Finally, I was not able to discover how to purchase the product other than contacting a general phone number or sending a general inquiry to info@switchmaterials.com.