Saturday, 7 July 2012

Innovative prototype

As you can read in the history of PPG [1], the idea of coupling multiple panes spaced a few millimeters existed already in the 40s, initially using air in the chamber. Then the use of inert gases such as argon, Krypton (but only in the most important) has been implemented as well as creating a vacuum between the panes (optimal solution but hardly used).
There are innovative devices, one of them from BEET/project_page:
The system consists of a reversible window frame holding two glazing components: a transparent glazing that provides a weatherproof seal, and an absorptive glazing having top and bottom vent openings for airflow. While the airflow may be natural or mechanically-driven, the window frame can be rotated so that the absorptive glazing is either on the interior (for space heating in winter) or on the exterior (for reducing unwanted-heat in summer).
Taken from [2]
The development test was conducted in Hong Kong, where best solution is "summer mode", with a reduction of heat transfer equal to about 70%.

Taken from [2]

Since the heat extraction capability of flowing water is much better than flowing air, there is a version with water into the chamber.
In addition to reducing the transmission of the incoming heat in the building, this has other advantages, including the possibility of obtaining a pre-heating of the water. For this reason its possible use in a pool that has large windows, for example, fascinates me.

You can read the full discussion on [3]. It requires knowledge of fluid mechanics to analyze the motions of the water flow, but it's a very interesting article, also because of the tests and comparisons using different glass types in the assembly.

[3] Chow Tin-Tai, Li Chunying, Lin Zhang. Innovative solar windows for cooling demand climate. Solar Energy Materials and Solar Cells, 94(2), 2010, 212-220.

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