Advanced Technologies for Smart Windows.

tempered ultra-thin glass membranes

1 The idea behind

The weight of a window could be reduced by 50 per cent through the use of tempered ultra-thin glass membranes as middle or inner pane within a triple or quadruple IG-unit (down to ~0.9mm). But todays tempered glass applications like solar modules or other weight and transmission sensitive applications are based on thinnest commercial available glass – 3.0 mm.
The reason is simply the physical limit on conventional tempering furnaces based on ceramic rollers as transport system; these rollers are arranged in a certain minimum distance but still glass with a temperature close to Tg (at 650 °C) tends to deformation when passing the free space between the rollers, thus creating so-called roller waves in tempered glass, being visible as uneven deflection known from reflecting facades [1].
A new approach of air cushion transportation within tempering furnaces enables tempering of thin glasses without any roller waves, proven today already in glass thicknesses down to 1.8 mm. These thin glasses are used preferably in new solar module applications, enabling weight reduction as well as higher transmission. This technology is patent pending by LiSEC and a few installations within Europe and Asia are already existent.
Tempered thin glass opens up new unparalleled possibilities.  Lightweight, flexible and durable glass units without optical distortions and lower stress for the spacer system are ideally suited for use in modern architecture with highly energy-efficient windows/facades. Using tempered thin glass allows for considerably lighter modules with remarkably better thermal insulation values and increased lifespan.

[1]    A. Aronen et al. Proceedings of the ASME 2011 International Mechanical Engineering Congress & Exposition IMECE2011


2 Advantages

Due to the reduced thickness this developments allow to save energy for the tempering of up to 40%. The LiSEC air cushion system is ideal for surface-treated or double-sided coated glass sheets. The required energy is controlled by the air volume and can be immediately adjusted to a wide range of glass properties. (e.g. ultra clear, Low-E, Suncoat, enamel, etc.). No contact is made, which means there is no wear. Ceramic is a highly wear-resistant material. It distinguish from conventional roller furnaces by

  • The glass surface is not touched
  • Air cushions are used instead of ceramic rollers
  • Maximum convection in the circulation system
  • Symmetrical energy input


The utilization of ultra-thin tempered glass membranes within highly energy efficient windows shows following advantages:

  • Lower breakage losses due to thin glass sheets of enormous strength and flexibility
  • Lower distortions in façade in the event of alternating climate loads due to adjustment of the inner panes to gas volume changes (while the outer pane remains in plane, because the outer pane is thicker in order to be able to carry the wind loads)
  • Lower stress on spacer bars while climatic loads due to flexible adjustment to gas volume
  • Lower loads on fittings and frames due to weight reduction
  • Improved working conditions for window construction employees
  • Higher transmission (+1% for each mm glass thickness saved) (less absorption through thinner glass)


3 Results

With a new air cushion tempering furnace LiSEC demonstrated in experiments that the glass thickness could be reduced down to ~ 0.9 mm. The membrane effect of the flexible tempered thin glass sheet in the unit considerably reduces optical distortions of the thicker exterior glass (thickness regarding wind loads). Even with large temperature changes, the structure compensates for pressure fluctuations occurring in the unit.

 

 

4 Conctact

Markus Jandl
LiSEC
markus.jandl@lisec.com 
+43 7477 405
www.lisec.com