Thermal performance analysis of an electrochromic vacuum glazing with low emittance coatings

Thermal performance of an electrochromic (EC) vacuum glazing (VG) was modelled under ASTM standard winter conditions. The
EC VG comprised three 0.5 m by 0.5 m glass panes with a 0.12 mm wide evacuated space between two 4 mm thick panes sealed contiguously
by a 6 mm wide indium based edge seal with either one or two low-emittance (low-e) coatings supported by a 0.32 mm diameter
square pillar grid spaced at 25 mm. The third glass pane on which the 0.1 mm thick EC layer was deposited was sealed to the evacuated
glass unit. The whole unit was rebated by 10 mm within a solid wood frame. The low-e coating absorbed 10% of solar energy incident on
it. With the EC VG installed with the EC component facing the outdoor environment, for an incident solar radiation of 300 W m2,
simulations demonstrated that when the EC layer is opaque for winter conditions, the temperature of the inside glass pane is higher than
the indoor air temperature, due to solar radiation absorbed by the low-e coatings and the EC layer, the EC VG is a heat source with heat
transferred from the glazing to the interior environment. When the emittance was lower to 0.02, the outdoor and indoor glass pane temperatures
of the glazing with single and two low-e coatings are very close to each other. For an insolation of 1000 W m2, the outdoor
glass pane temperature exceeds the indoor glass pane temperature, consequentially the outdoor glass pane transfers heat to the indoor
glass pane.