Glass in Solar Technology

Photovoltaic Modules Mounted with Adhesive Point Fixings

Solar technology, like glass in building, is making use of ever larger glass for­mats [53]. Correspondingly higher component weights call for improvements to the fixings. The comparison between positive connection, nonpositive connec­tion, and material bond frequently results in a decision in favor of adhesives because of the many advantages. New developments for point, linear, and pla­nar adhesive joints in solar technology are presented below.

Essentially influenced by the progress in coating technology, very large pho­tovoltaic (PV) modules are now being produced which can no longer be secured with conventional clamp fixings.

An adhesive point fixing for fitting on the back of thin-film PV modules has been developed within the scope of a research project [54]. This fixing (Fig. 15) can be adapted to suit the supporting frameworks of various manufacturers available on the market. The adhesive used can carry the structural and dynamic loads acting on the joints for the duration of the anticipated service life of a PV module.

Selected adhesives are characterized in the laboratory. Following initial tests on fixings with preliminary dimensions, the suitability of the optimized fix­ing is tested according to DIN EN 61646 [55]. The pneumatic testing apparatus (Fig. 16) enables the evaluation of the mechanical load-carrying capacity of PV modules, also when subjected to rapidly changing loading cycles. The fatigue behavior of the adhesive joint and the fixing is estimated with the help of

FIG. 15—Prototype of an adhesive point fixing.

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FIG. 16—Pneumatic testing apparatus.

dynamic tests. The material parameters determined in the laboratory and the experience gained with small-scale specimens is incorporated in the optimiza­tion. The tests, including accelerated aging methods and in conjunction with the fixing material selected, back up the permanent properties of the adhesives. Furthermore, studies are carried out to optimize the adhesive parameters, e. g., surface preparation, application, and curing.