Solar Control - Barriers to the Sun
Intensive research over several decades has equipped the float process with ingenious ways of controlling solar energy for greater comfort and economy. Ingredients can readily be added to the melter to control the wavelength and percentage of radiation transmitted or absorbed by the finished product. Cobalt and nickel, ferrous and ferric iron, cerium and titanium are all used to control transmission of infrared or ultraviolet waves to differing degrees and with differing visual effects.
Coatings on the glass are another way of modifying the solar control properties. In the early 1980s Pilkington developed technology for coating plates of glass off-line, using a vacuum coating technology called sputtering. A target material is bombarded by ions from a glowing plasma and atoms ejected from the surface are deposited to form a coating on the glass.
Multi-layer coatings using different materials are needed for the highest optical performance. Computer modelling now means the optical properties of coatings containing seven or more layers can be predicted, with only minimal experimental trials needed before full scale production. High performance solar control coatings can now be produced, based on ultra-thin metallic silver layers sandwiched between oxide layers, which combine high near-infrared heat reflection with high visible transmission.
In the late 1980s Pilkington researchers developed an alternative coating technology using chemical vapour deposition which, although not able to achieve the outstanding solar control performance of the sputtered product, produced a more abrasion resistant glass which was easier to handle and install.
The challenge now facing researchers is to develop products that further extend the properties that can be offered to the market.