A transparent material has been developed in the US that promises to reduce energy needs while improving comfort inside buildings by controlling solar heating. The material is a glass that contains nanocrystals – tiny particles that react in a specific way to light – and which is adjusted electronically to ensure that just enough light passes through the glass.

Natural light contains more than just the visible spectrum, as we know. Infrared light, with long wavelengths, provides heating, while ultraviolet, at the other end of the spectrum, is what tans skin. Both are relatively easy to block (consider UV protective sunglasses, or intelligent sun shading), but what if you want to adjust the amount of warmth let through a window while keeping it transparent?

To do this, a variable material is needed. Researchers in California and Spain recently published work on a material that can do just that. Building on from work with indium and tin oxide crystals, the team added niobium to create a niobium-oxide glass.

A low voltage passed through the glass had a better than expected result. At voltages between 1,5V and 4V, the glass changes from being transparent (visible and infrared light pass through) and almost opaque (visible and infrared light blocked) and a third setting (blocking only infrared light).

Essentially, what the newly developed glass does is split heat and visible light and give the control to the user. This makes it a very attractive material for use in future design applications. A few snags remain: niobium is expensive, and voltage is required to power the glass, so it is unclear exactly how much energy will be saved in the long run.

The researchers mention some great advantages to this ‘crystal-in-glass’ development. Besides the selective blocking of visible and infrared light and the low voltage required, the optical contrast is five times that of similar materials, meaning that the image through a pane of this glass is less ‘misty’. Also, the nanocrystals are highly stable, meaning that they can be used again and again effectively.

The material is currently being developed by a start-up, Heliotrope. The article in Nature is here. More information is here.

 

Images courtesy of DailyCal, and creative commons.