Photovoltaic Modules Fixed with a Linear Adhesive Joint
Individual laminate clamp fixings are frequently adequate for fixing frameless PV modules. This means that in contrast to conventional module frames with a linear support to the glass laminate on all sides, and hence a “gentle" form of mechanical fixing, stress peaks cannot always be avoided. With large-format modules in particular, the interplay between the geometry of the fixing elements and their position on the module offers considerable potential for optimization with respect to a mounting solution that is safe and also efficient in terms of materials. In the light of this, innovative roof- and ground-mounted arrays are increasingly being based on adhesive fixings . Using adhesive for joints involving glass is a method very much suited to this material. It also offers the chance of stiffening a thin module on the back and for leaving the front flat and unobstructed, which is advantageous for photovoltaics as it assists the selfcleaning function, helps to ensure that snow slides off, and avoids microshadows (Fig. 17). However, fundamental research into this innovative type of fixing, for various applications and loads, still has to be carried out. The linear load bearing rails are usually made from galvanized steel, stainless steel or anodized aluminum, and are connected to the back of the PV module with liquid or paste adhesives, e. g., 2-part silicone, or with double-sided adhesive tape, e. g., acrylate foam tape.
In accordance with the existing German testing regulations , the Institute of Building Construction has carried out tests using the example of an
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FIG. 17—PV module with mounting rails fixed to the back of the module with adhesive.
acrylate adhesive tape for attaching the back rail in order to analyze its suitability and significance for this application. Beside thermal analysis methods and tensile tests on dumbbell specimens punched out of the material, in situ specimens were also tested in tension and shear (see, for example, the tensile test specimen in Fig. 18).