Bio-Inspired Window Panes Show High Levels of Efficiency

As newer and better technology continues to come to the market, an emerging trend in design is to turn toward Mother Nature for inspiration, which is exactly what a group of engineers did when developing a new model for more energy efficient windows.

By creating an artificial vascular network, researchers from Harvard University and the University of Toronto were able to construct a window pane that cuts down on heat loss during the winter and could help keep buildings cool in the summer.

The bio-inspired vascular network is a clear sheet of flexible material that is bonded to regular window glass panes. The sheets are made of a material called polydimethylsiloxane, and contain tiny channels through which room-temperature water flows.

In the laboratory, the design has achieved 7 to 9 degrees Celsius of cooling and is effective both at small and large scales, said University of Toronto engineering and materials science professor Ben Hatton.

"Our results show that an artificial vascular network within a transparent layer, composed of channels on the micrometer to millimeter scale, and extending over the surface of a window, offers an additional and novel cooling mechanism for building windows and a new thermal control tool for building design," Hatton said.

He also noted that as the water flows through the panels, it gets hotter, and this hot water could be used to supply heated water to an existing hot water system or to a heat storage system.

Windows are a major source of building energy cost, accounting for as much as 40 percent of the cost, Hatton said. In attempting to design a more efficient window pane, he turned to nature for inspiration.

"In contrast to man-made thermal control systems, living organisms have evolved an entirely different and highly efficient mechanism to control temperature that is based on the design of internal vascular networks," he said. "For example, blood vessels dilate to increase blood flow close to the skin surface to increase convective heat transfer, whereas they constrict and limit flow when our skin is exposed to cold."

Hatton added that the vascular technique could increase the efficiency of solar panels.

A paper detailing Hatton and his colleagues' research is published in the journal Solar Energy Materials and Solar Cells