Thermal image of a building
Ivan Smalyuf
See-through airgel made of wood can displace the air in double-glazed windows and insulate just like walls.
Windows with air trapped between the panes of glass can be insulated better by increasing the number of glass panels or by increasing the width of the air gap, but this can affect visual quality. There is a nature. As the convection becomes easier to circulate, the insulation effect increases.
To address this, Ivan Smalyukh and his colleagues at the University of Colorado Boulder used cellulose nanofibers to create aerogels. Aerogels are solid gels containing pockets of gas that may perform better than air in double glazing.
Mr Smalyukh said: “You can think of it as a window pillow because it keeps the heat where you need it and at the same time you can see inside.”
To make the airgel, they first suspended cellulose nanofibers from wood in water, then replaced the water with ethanol. We then increased the temperature and pressure to dry the airgel, replacing the ethanol-filled pockets within the material with air, and added a silicon compound on the surface to make it water-repellent and prevent condensation when used on windows.
Small pockets of air embedded in airgel mean they can be used to fill larger spaces without the convective effects that air alone can provide. An airgel filling about 2.5 cm wide can insulate a window as well as a wall.
“This is a very good development that can be easily adopted as a retrofit to existing windows,” says Steve Eichhorn of the University of Bristol, UK. “Reduced heat transfer and the additional benefits of retained transparency and low haze make this material truly outstanding, all using a sustainable material, cellulose.”
Scale-up presents challenges, but viable processes for producing cellulose nanofibers at scale already exist, says Eichhorn.
topic:
- material/
- energy efficiency
