Société d'Energie Solaire (SES), a Swiss company, has just patented a new system that promises to offer numerous advantages through material savings and automation. It has been shown for the first time at Intersolar 07.
In the new SES process, the strings, instead of being soldered to the peripheral end-ribbon, are folded over the back of the cells, where they are soldered with a simple machine onto a flexible circuit. The circuit substrate is a DuPont™ Tedlar® PVF film laminated with DuPont Teijin Films™ Mylar® PET polyester film; the circuit has special contacts for attachment to the junction box and also serves to insulate the strings from the cells. After lamination, a special junction box, made by Huber & Suhner, is simply placed over the circuit and the connections are soldered.
The junction box is then filled, with reduced use of silicone, sealed and the lid fitted. The box is designed to allow ventilation between itself and the backsheet, so as to prevent heat build-up. SES tried numerous films and film combinations for this printed circuit, says M. Philippe Crisafulli, project manager at SES. "The substrate for this application has to meet many requirements, such as being flexible, having god dimensional stability, offering high UV resistance, accepting printed circuit processes without deformation, withstanding oven curing at 150 degrees celsius, being a good electrical insulator or offering a 25 year guarantee"
"After many false starts, we found that only a combination of the new Tedlar® PV2111, which has improved dimensional stability, together with Mylar® met all these requirements at an acceptable cost. Moreover, each film has to have a certain thickness in the combination. The fact that both of these DuPont films have been proven over the past 25 years in the PV industry also played a role in our choice. DuPont helped us with expert advice during the two years it took to develop our process."
"Our innovation, which can be applied to any type of PV cell, is a significant improvement in panel assembly. With our innovation, the electrical connections are simpler and faster to make. The manufacturing steps are reduced, so throughput is increased. Use of simple robots instead of manual labour increases capital productivity and the reliability of connections. Less silicone encapsulant is needed. Elimination of the peripheral end-ribbon allows a 2 % to 5 % reduction in module area and better aesthetics." added Mr Jean-Christophe Hadorn, SES President.
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