Materials

Transparent insulating aerogel brewed up from beer by-product

Transparent insulating aerogel...
Researcher Qingkun Liu holds up samples of the new transparent aerogel, which could make windows better insulators
Researcher Qingkun Liu holds up samples of the new transparent aerogel, which could make windows better insulators
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The new transparent aerogel is settled on a pane of glass in a tub
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The new transparent aerogel is settled on a pane of glass in a tub
Researcher Qingkun Liu holding up cellulose, which has been produced from beer wort and is used to make the new transparent aerogel
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Researcher Qingkun Liu holding up cellulose, which has been produced from beer wort and is used to make the new transparent aerogel
The transparent aerogel is made using a beer by-product known as beer wort
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The transparent aerogel is made using a beer by-product known as beer wort
Researcher Qingkun Liu holds up samples of the new transparent aerogel, which could make windows better insulators
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Researcher Qingkun Liu holds up samples of the new transparent aerogel, which could make windows better insulators

Made up of over 90 percent air by weight, aerogels are the lightest materials in existence and among the best thermal insulators. But their cloudy appearance means they don't lend themselves well to windows, which are one of the worst offenders for letting heat escape a building. Now, researchers at Colorado University Boulder have found a way to make them transparent, recycling a beer by-product in the process.

Trapped air is key to thermal insulators. Clothes keep you warm by trapping air close to your skin where your body heat warms it up, and materials like wool and goose down feel warmer because their higher surface area can hold more air. Since aerogels are mostly air, that makes them terrific insulators, and they've been put to work in bricks, tiny houses and winter jackets.

But the very structure that makes them great insulators makes them terrible windows. Aerogels have a crisscrossing structure of solid material that creates billions of pores to hold air, but that also scatters a lot of light, giving them a cloudy look sometimes called "frozen smoke."

So the CU Boulder team set out to develop a more transparent aerogel that could be fitted over windows, letting light pass through while keeping heat in. To do so, the researchers turned to cellulose, a common plant sugar that can be manipulated so its molecules link up in a uniform lattice pattern.

The transparent aerogel is made using a beer by-product known as beer wort
The transparent aerogel is made using a beer by-product known as beer wort

But it's where the team sourced this cellulose that's particularly clever – liquid waste from the beer-brewing process. The horribly unappetizing by-product known as beer wort is normally just discarded, but the researchers found they could use it to produce cellulose for their aerogel.

First, they collected tubs of the stuff from local breweries. Then, they added specialized bacteria that can create cellulose from beer wort over about two weeks. With the material in hand, the team can then induce the cellulose to self-assemble into nanofibers to make the gel. The end result is a thin film that's transparent and highly heat-resistant.

The team says that the transparent aerogel could be most useful as a film that sticks over existing windows to greatly improve their thermal insulation, in turn making heating more efficient and less expensive.

"Windows are incredibly expensive to replace," says Andrew Hess, co-author of the study. "We're envisioning a retrofitting product that would basically be a peel-and-stick film that a consumer would buy at Home Depot. We also see our technology being enabling for so many other applications, including smart clothes, for insulating cars and protecting firefighters."

The new transparent aerogel is settled on a pane of glass in a tub
The new transparent aerogel is settled on a pane of glass in a tub

But these applications might not be limited to Earth either – a few months ago the team won NASA's 2018 iTech competition, pitching the aerogel as an insulator for otherworldly windows.

"Transparency is an enabling feature because you can use this gel in windows, and you could use it in extraterrestrial habitats," says Ivan Smalyukh, corresponding author of the study. "You could harvest sunlight through that thermally insulating material and store the energy inside, protecting yourself from those big oscillations in temperature that you have on Mars or on the moon."

The research was published in the journal Nano Energy. The team demonstrates the fabrication process in the video below.

Source: CU Boulder

From beer to windows

6 comments
Techtwit
Interesting article, but "wort" is not an unpleasant by-product of the brewing process, it is the high strength sugar solution run off from the malt/liquor mix which is then boiled in the copper/kettle then fermented to produce beer. I really am not happy at somebody trying to convert my beer into somebody else's windows. Imagine going out for a "pane" instead of a "brew"?
J4rH43d
N-o-o-o-! Beer wort is not a waste product. It is the liquid that is boiled (brewed) with hops to become beer. It is NOT discarded. Perhaps someone misheard a description when editing this article. Now, the spent hops is mostly cellulose and is left behind when the beer wort is drained, chilled, and fermented to become beer. Could the actual souce of the cellulose be spent hops?
StWils
Once again, whoever wrote this piece skipped over a fairly obvious set of questions. First, how much insulation value in how thin a sheet? Second, how expensive is this stuff? Third, how long is it likely to last? Fourth, how soon is this likely to hit the market? These are all fairly obvious questions that you people routinely gloss over or just do not ask about. Please fix this shortcoming.
calee
Seconding the 'by-product' note. Wort is simply unfermented beer. The original article by the CU Boulder team also used an incorrect description. Without wort, there would be no beer.
Douglas Bennett Rogers
The highest and best use of aerogel is to form the crust of the air core planet!
Jean Lamb
I want the cost to come down--what's wrong with windows that are R50?