Rolled Glass
The rolling process is used for the manufacture of solar panel glass, patterned flat glass and wired glass. A continuous stream of molten glass is poured between water-cooled rollers.
Rolled glass is increasingly used in PV modules and thermal collectors because of its higher transmittance. There is little cost difference between rolled and float glass.
Rolled glass is special due to its macroscopic structure. The higher the transmittance the better and today high performance low iron rolled glass will reach typically 91% transmittance.
It is also possible to introduce a surface structure on the surface of the glass. Different surface structures are chosen depending on the intended application.
A burred surface structure is often used to enhance adhesive strength between EVA and glass in PV applications. Structured glass is used in both PV and thermo solar applications.
Patterned glass is made in a single pass process in which glass flows to the rollers at a temperature of about 1050°C. The bottom cast iron or stainless steel roller is engraved with the negative of the pattern; the top roller is smooth. Thickness is controlled by adjustment of the gap between the rollers. The ribbon leaves the rollers at about 850°C and is supported over a series of water cooled steel rollers to the annealing lehr. After annealing the glass is cut to size.
Wired glass is made in a double pass process. The process uses two independently driven pairs of water cooled forming rollers each fed with a separate flow of molten glass from a common melting furnace. The first pair of rollers produces a continuous ribbon of glass, half the thickness of the end product. This is overlaid with a wire mesh. A second feed of glass, to give a ribbon the same thickness as the first, is then added and, with the wire mesh “sandwiched”, the ribbon passes through the second pair of rollers which form the final ribbon of wired glass. After annealing, the ribbon is cut by special cutting and snapping arrangements.
