Indium alloy-sealed vacuum glazing development and context

Vacuum glazing consists of two parallel glass sheets with a narrow vacuum gap in between. The sheets are separated by an array of support pillars under the influence of atmospheric pressure imposed on the external surfaces of the two glass sheets. The vacuum gap sealed by a sealant (either solder glass or indium alloy) minimizes the air heat conduction and convection across the glazing. One or two high performance low emittance (low-e) coatings deposited on the internal surface(s) within the vacuum gap reduces the radiative heat transfer to a very low level. The heat transmittance of 0.80 W m−2 K−1 and 0.86 W m−2 K−1 at the central area of vacuum glazing with two low-e coatings and support pillars of 0.25 mm and 0.4 mm in diameter were achieved and experimentally characterized using the guarded hot box calorimeters by the University of Sydney and the University of Ulster, respectively. If combined with solar control glazing such as electrochromic (EC) glazing, it has a great potential to significantly reduce the load of heating in winter and cooling in summer and to provide thermal comfort for the occupants. If combined with the third glass sheet forming a gas filled or second vacuum gap, the heat transmittance will be further reduced. In this work, the basic characteristics and fabrication process of vacuum glazing are reviewed. The potential performance of vacuum glazing, EC vacuum glazing and other hybrid vacuum glazing with second either gas filled gap or vacuum gap are presented.