PURITANISM PAYS:

Windows are critical for improving building energy efficiency. Over a quarter of a building's energy is lost through today's glass-pane windows. Now, drawing inspiration from the color-changing skins of squids and krill, researchers have designed liquid-filled panels that dynamically change how they let light through. Retrofitting windows with these panels could cut the energy costs of heating, cooling, and lighting buildings by well over 40 percent, they say. [...]

The University of Toronto team wanted to make such a dynamic system using simple, low-cost components. They sandwiched together three thin Plexiglass sheets, each containing roughly 2-3mm high channels patterned into it. Through each layer, the researchers pump various fluids: water-based dye solutions or glycerol that absorb light of certain colors; carbon pigment suspensions that control light transmission; and titania nanoparticle suspensions that direct the light passing through. "The net effect on light transmission is through the additive effects of the combined layers," Hatton says.

The researchers conducted experiments and ran whole-building computer simulations to see how the squid-inspired windows improve building energy performance. They calculated estimated annual savings of 75 percent on heating energy, 20 percent on electricity for lighting, and 43 percent on total energy use compared with the best available darkening windows on the market today. The energy saving would be even higher when compared to plain glass windows, he says. The work appears in the journal Proceedings of the National Academy of Sciences.

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