LayTec and CSE Partner to Successfully Commercialize a New PV Metrology Method

LayTec's X Link inline metrology tool uses a technique developed and patented by Fraunhofer CSE to quickly and accurately assess module reliability. (Image courtesy of LayTec)

LayTec’s X Link inline metrology tool uses a technique developed and patented by Fraunhofer CSE to quickly and accurately assess module reliability. (Image courtesy of LayTec)

[Today's guest post comes to us from Ben McBride, a PV Fellow who's currently working with our Photovoltaic Technologies team to help solar companies develop pioneering products. Over the past few weeks, Ben has been working on an exciting new quality assurance tool for the solar industry, and was kind enough to share a few details about his work.]

The amount of photovoltaic (PV) solar power installed around the world has grown by a factor of almost sixty over the past decade, and it increased nearly 70% in the last year. As hundreds of thousands of solar panels are added to homes, commercial rooftops, and utility power plants every year, it becomes increasingly important for manufacturers—and consumers—that these products will survive the test of time in what are often harsh conditions.  Solar panels sold on the market today typically come with a 25-year warranty, and there are panels currently installed in the field that have exceeded the manufacturer’s performance guarantee—even after more than 20 years of outdoor exposure.  But for each module that beats the odds, there are many others that start losing performance after just a few years of outdoor exposure—a problem with real financial consequences for homeowners and companies.

To understand why PV solar modules lose power, it’s important to also understand how they are assembled. One of the biggest challenges of building a module is protecting the physical and electrical properties of a crystalline silicon solar cell that is about one-sixth as thick as a CD and more brittle than a piece of antique china. It’s a challenge that’s made all the greater by the conditions modules are exposed to: high winds, rain, sleet, snow, or extreme sunshine. The most common and reliable method of protecting solar cells involves sandwiching them between sheets of  a material known as ethylene vinyl acetate (EVA), covering the front with a pane of glass, and laying a protective back sheet on the rear side.  This stack is then heated to allow the EVA to cure, which seals the stack as a module.  During the curing process, polymer chains within the EVA become cross-linked together.

How much cross-linking takes place within the EVA is an important determining factor in how well the module will stand up to the punishments of Mother Nature.  The higher the degree of cross-linking, the more durable the module.  A common method for checking cross-linking is to rip through the protective back sheet, extract a piece of EVA from the interior of the module, and perform a series of steps involving harsh chemicals over the course of several days. However, this method effectively destroys the module, and requires specific skills and facilities to carry out.

In the Photovoltaic Modules Group at Fraunhofer CSE, we have developed a method that enables us to assess cross-linking in a matter of seconds without damaging the module in any way, greatly improving quality control options for PV solar module production. This method takes advantage of the effects cross-linking has on the elasticity of the EVA binding the module together. By mechanically distorting the back of the module, it is possible to quickly measure the elasticity of the EVA, and in turn, how much cross-linking has taken place.

Our novel technique has proven to be quick and nondestructive, and we’ve worked to scale our initial prototypes up to the industrial level. Last year, we licensed the patent for this method to LayTec, a manufacturer of optical in-situ and in-line metrology systems for the PV and thin-film industry. The end result is LayTec’s new X Link metrology system, which was officially announced on May 2nd and given its first public showing in Shanghai, China earlier this year.  Visitors to this year’s Intersolar North America show will get an opportunity to see the X Link first-hand at Booth 8501 in the Moscone Center’s West Hall, and learn more about this exciting collaboration from both partners’ technical teams. We look forward to seeing you there!

About author
I'm a founding member of Fraunhofer CSE, having joined the Center back in 2008. In addition to serving as Fraunhofer CSE's Marketing Specialist, I work as a marketing and communications consultant and freelance creative professional.
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