Vacuum glazing has been on the market for over a decade, but its performance is poor, and its cost too high for wide adoption. Both issues stem from the use of a hard glass edge seal, which requires a high temperature manufacturing process, and which does not flex to accommodate outer pane contraction in winter weather. Lack of a low-cost, flexible seal has prevented successful commercialization of vacuum glazing for over three decades. A metal foil edge seal offers a promising alternative. V-Glass has demonstrated the ability to ultrasonically weld aluminum foil directly to bare window glass, a room- temperature process that also promises to be low in cost. One hurdle remains: frequent sticking of foil to sonotrode, resulting in tearing and perforation. Building upon the prior V-Glass work, this project seeks to identify a sonotrode material and welding parameters which can create a continuous hermetic edge seal between metal foil and bare glass. A subaward will be made to Edison Welding Institute to identify improvements in sonotrode material and welding process, using helium leak testing to measure hermeticity of metal-to- glass seals produced. V-Glass will then use this improved welding process to manufacture prototypes which will be subjected to several months of cyclic thermal testing. If the dew point inside the glazing remains below -40F, the seal has successfully prevented moisture entry. Commercial Applications/Benefits Demonstration of a robust and low-cost manufacturing process for flexible metal foil seals for vacuum glazing will facilitate further private sector investment in a high risk/high reward technology. Once commercialized, such glazing will enable production of high performance windows (R10 or better) for the same cost. Not only will this will secure for the U.S. a dominant position in a global market totaling $8 billion per year, but can eventually reduce total US energy use (and greenhouse gas emissions) as much as 5% while improving comfort.
