Abstract :
In this study, solar control coatings were prepared by sequential depositions of thin films of ZnS (40nm)–CuS
(150nm) and ZnS (40nm)–Bi2S3 (75nm)–CuS (150nm) from chemical baths on 3mm thick commercial sheet glass.
These were laminated to 3mm thick clear glass or commercially available SnO2 based heat mirror coating of sheet
resistance 15X on float glass of 3mm thickness using a poly(ethylene vinyl acetate), EVA, sheet of 0.36mm thickness
in a vacuum process at 120 C for 30min. In total, the thickness of the glazing was 6.35mm. The glazings possess visible
transmittance, weighted for D65 solar spectra and sensitivity of the human eye for daylight vision, of 36% or 14% with
solar absorptance of 71% or 78% depending on the coating type, i.e ZnS–CuS or ZnS–Bi2S3–CuS-heat mirror respectively.
The solar heat gain coefficient (SHGC) was evaluated for these glazings at exterior temperatures of 15 and 32 C
for an exterior convective heat transfer coefficient (hex) of 6–100Wm 2K 1 using a mathematical model. The model
predicts the extent of reduction in SHGC through the presence of the heat mirror coating as a function of hex and hence
helps to decide on the relative benefit, which may be derived through their use in different locations. Though the deposition
technique mentioned here involves longer duration compared with vacuum techniques, it may be developed into a
low throughput, low-capital alternate technology for small-scale production.
2004 Elsevier Ltd. All rights reserved.
