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June 2008

The sun shines on solar power - More efficient production methods for the solar modules


With installed capacities currently growing almost exponentially around the globe, it is extremely important to develop more efficient production methods for the solar modules that are essential to this ever more attractive market.

When manufacturing solar cells, embedding films are used to secure the all-important silicon wafers between glass and substrate. With films made from the Bayer MaterialScience thermoplastic polyurethane Desmopan® the need for time-consuming crosslinking of the embedding material dispenses. This significantly improves the capacity utilization of high-tech vacuum laminators. They can even be replaced by simpler roll laminators.
There is definite room for improvement here, as employees of Bayer MaterialScience were recently able to demonstrate. Light-resistant thermoplastic polyurethanes (TPUs) make it much easier to manufacture solar modules. A film made from Desmopan® has been developed in collaboration with ETIMEX-Primary Packaging GmbH based in Dietenheim, Germany.
In the medium term, this will enable a continuous production process to replace the current batch production in certain areas, which could boost a module manufacturer’s output many times over with a comparatively low investment. The potential for improvement in cost-effectiveness should make solar power even more competitive in the future.

“It’s amazing how quickly solar power is expanding around the globe,” comments Faisal Shafiq, a Bayer MaterialScience expert on thermoplastic polyurethanes. According to the European Photovoltaic Industry Association (EPIA), the global market for solar power installations is currently growing at a rate of around 40 percent. Solar-Report 1/2008 from web service Solarserver.de reveals that the contribution of large solar power installations (at least 200 kW/a) to power grids has doubled every year since 2004. “And this trend is expected to continue,” says Shafiq.

As a result, the solar modules that generate solar power photoelectrically are very much in demand. “Yet they are still produced using a comparatively complex process”, explains Shafiq. Solar cells made from silicon wafers are put between a sheet of glass and a substrate together with an embedding film (primarily EVA films) and thermally crosslinked in a vacuum laminator for 12 to 20 minutes at temperatures of around 145 °C. This high temperature ensures that the EVA elastomer hardens to create a transparent layer. According to Shafiq, “This method has a number of disadvantages. For example, the time required for crosslinking prevents a higher throughput being achieved and solar module manufacturers have to factor in comparatively high downtimes and maintenance costs because the crosslinking agents added to the EVA can make it necessary to replace the filter membranes.”


Find more information at www.bayermaterialscience.com
 

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