Regarding the reliability of photovoltaic systems, so much depends upon the lamination process during fabrication. Many manufacturers guarantee their solar modules will still deliver 80 percent of their output power after 25 years. But if encapsulation – the technique that protects the solar cells from environmental wear and tear – is less than perfect, this is unlikely to be the case.
The Fraunhofer Centre for Silicon Photovoltaics (CSP) considers the problem critical enough to kickstart a multi-partner project to design a more reliable method for encapsulation.
During manufacturing, the solar cell composites are fixed into place by two films of EVA plastic that are heated in stages: the first film melts, flows into the voids between the cells and fills them. In the second stage, the material is "crosslinked", meaning the molecules combine to form a 3D structure that stabilises the cell. "In places where encapsulation films are insufficiently crosslinked, delamination can occur over time, which affects the life of the module," explains Anton Mordvinkin, heading up the project at Fraunhofer CSP in an .
If the so-called “degree of crosslinking” could be measured in factory, without destroying the module (which it what usually happens), then lamination could be properly monitored and weak points rectified before the system reaches the market. The partners aim to develop a quality control protocol for reducing potential lamination failures by up to 20 percent.
As a starting point for designing the non-destructive measurement technology, Fraunhofer CSP will use data from field returns, as well as from climate chambers and weathering tests. The team expects the optimised lamination technique will increase the solar cell production yield by 2 percent, as well as extending the system’s performance overall.