First Field Test
March 3, 2014 was one more cold day of winter for Wisconsin, nearly zero degrees. A prototype V-Glass vacuum window was installed in the testing window of Room 104 of the Technology Innovation Center building. This prototype was "actively pumped", that is, it was connected to a vacuum pump. When the pump was off, there was no vacuum between the panes, but with the pump on, almost all the gas molecules in the space between the panes were removed, creating a substantial vacuum.
The chart above shows temperature data collected by a V-Glass-designed data acquisition system. One data point is taken every 5 minutes.
The blue line is the inside air temperature.
The violet line is the outside air temperature.
The green line is the inside pane temperature.
The red line is the outside pane temperature.
The yellow line is the outside light level, showing not only the distinction between day and night, but also indicating whether the window is exposed to direct sunlight, shadow or overcast conditions.
In the morning, the vacuum pump was off, and the space between the panes contained air at atmospheric pressure, providing almost no insulation. The inside and outside panes were at the same temperature, almost midway between room temperature and the frigid outdoor temperature.
At about 2:30 in the afternoon, the vacuum pump was turned on. The space between the panes was evacuated, which instantly stopped much of the convective and conductive heat loss from the inside to the outside pane. The chart shows the result: a large pane-to-pane temperature difference. The inside pane became much warmer, and the outside pane became much colder.
If you've ever felt the inside window pane on a winter day, it probably has felt cold. The inside pane of a V-Glass vacuum insulating glass unit will feel warm.