What differentiates solar glass from architectural glass (window glass):
Solar glass is generally produced from the same raw materials as architectural glass, however there are significant differences:
The raw materials for solar glass have to be free from colouring oxides. In particular, iron oxide should only be present in very low concentrations. Iron oxide give glass a green taint and absorbs energy which is then no longer available for conversion into electrical or thermal energy.
The composition of the glass has to be carefully chosen so that long term durability (> 25 years), without changes in the optical and technical characteristics, can be guaranteed. An unsuitable glass composition could, in challenging circumstances (such as high humidity and high local temperature) lead to corrosion of the glass in a short time and hence lead to a reduction in transmission.
In order to guarantee the long term strength (flexural strength, resistance to hailstorms) the edge working needs to be of the highest quality and the glass has to undergo a special heat treatment (tempering process, “strengthening process”).
The edge working is of significantly more importance than is generally thought of in the industry: the standard configuration of the grinded glass edges of each GMB solar glass is optimised for this reason. The particular form of the C-edge plays a significant contribution to installation in PV modules and thermal collectors.
Structured glass – flat glass
Flat glass is usually produced by means of the float process (so-called float glass). After the smelting process, the glass “swims” of molten tin and so creates the flat and hence reflecting surface. The tin bath, which is so to speak the “forming of the surface” in the float process, requires large amounts of electrical energy.
Structured glass is usually produced using two forming smelters in a rolling process (so-called rolled glass). Hereby the top or bottom cylinder can have different surfaces. The rolling process requires a mere fraction of the amount of energy which is needed for the float process.
The rolling process was used in the past for the production of ornamental glass, hence for the manufacture of decorative glass for architectural use. A modern solar glass factory has, however, nothing to do with the classical production of ornamental glass.
The structures of GMB solar glass (SINA, CONE, ASTRA) have been designed for different applications and optimised respectively as such (see product presentation)
The concentrated dazzling is significantly reduced in comparison to flat glass (float glass). The reflection of structured surfaces leads to reflection patterns of various forms. In the case of smooth surfaces the reflection of an individual module or collector is concentrated on a narrow area (sketch). Structured glass is usually referred to as “dazzle-free” glass.
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