Watery windows mimic blood vessels to boost building efficiency

Watery windows mimic blood ves...
Does water hold the key to more efficient windows? (Photo: Nathan Larkin)
Does water hold the key to more efficient windows? (Photo: Nathan Larkin)
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Does water hold the key to more efficient windows? (Photo: Nathan Larkin)
Does water hold the key to more efficient windows? (Photo: Nathan Larkin)

Researchers at the University of Toronto say they can improve the energy of efficiency buildings by fitting window panes with tiny channels of water. The scientists says that these channels, inspired by vascular systems in nature such as the network of blood vessels in the human body, can provide 7º to 9º C of cooling in the summer, and reduce heat loss during winter.

The researchers developed a sheet of transparent flexible polymer with a "cooling layer" of clear silicone, inside which there are the tiny channels with a cross section 1 or 2 mm high and 100 micrometers across. Through these, room temperature water was circulated to and from an external source at a rate of 2 ml per minute.

The sheet was applied to a model window 10 x 10 cm (3.9 x 3.9 in) in size, an analyzed with an infrared camera. The researchers say that the temperature of the window, which had been artificially heated, was reduced by 7º to 9º C. Because the temperature of the water is lower relative to the window, it is able to absorb heat energy and take it away. The process would be the opposite during the winter, when room temperature water would supply heat to the rest of the window. In either case the idea is that the window would become a more effective barrier to convective heat transfer, making the building more energy efficient.

When filled with water, the researchers say that the channels are "not clearly visible," but that when filled with a different liquid which refracts light a similar amount to the surrounding material, they become almost invisible. They suggest that different liquids could be used for various aesthetic effects such as altering color and transparency.

The researchers were inspired by vascular systems in nature such as blood vessels in the human body which can expand and contract to increase or reduce heat loss when too warm or cold. The technology may also be applicable to photovoltaic solar panels which are more efficient at lower temperatures.

The team's research was published recently in the journal Solar Energy Materials & Solar Cells.

Source: University of Toronto

goes back to my thoughts of spraying the roof and sides of house with water on the hot days to decreasing the cooling load requirements (evaporative cooling effect).
Like the closed loop system approach, but suspect at some point a heat exchanger may be required. Alternate liquid fills is a cool aesthetic approach.
Great idea. And if you let the green slime build up naturally in the channels it will form a natural insulation - very green.
Good god, don't give the big property owners and new ideas about completely sealing these already "sick" buildings. As it is the windows don't open and air conditioning costs are so carefully measured that they charge for turning on the air flow should a tenant want to work on the weekend. What's next, space station air locks? Until air (and people) filtration systems advance substantially, getting fresh air from a single vent placed near back ally garbage containers and temporary parking for deliveries is the biggest concern; followed closely by total building air replacement cycle - not unlike your average airline flight.
Don Duncan
Mirmillion: Air lock entries are very practical in extreme climate. In winter they can be used as mud rooms.
I thought the latest glazing could be made reflective or not by passing a current thru it. Isn't IR radiation transmission more important than R value?
Layne Nelson
Is this for our health or energy?