Delamination

  • delaminazione_modulo

Delamination

Delamination of the PV module is the detachment, even if only partially, of the encapsulant from the glass or the backsheet…let’s have a look at the reasons causing it

A PV module has a multi-layer structure, which is sealed by an encapsulant, often based on Ethylene Vinyl Acetate (EVA). The different layers of EVA are melted together in one piece by a machine called laminator.

The laminator has a working cycle lasting less than 20 minutes at a controlled temperature of approximately 140 C. The process happens in a vacuum. This is extremely important in order to eliminate any air content inside the module, and to guarantee a high quality product.

During the lamination process, the EVA changes from a solid state to a liquid one, to finally settle in the form of a gel at the end of the cycle.

The fact that the different layers of the module will be sealed together for the 25 years of power output guaranteed by the manufacturer is determined by the percentage of the EVA gel.

There are different factors that can be held responsible for a low percentage of gel: the raw materials used, how these are transformed, and the manufacturing process.

The quality of the laminated material is determined by the content of gel, which is measured through a chemical test. A well- organized production facility can carry out the test in-house.
In general, the detachment is visible because of the presence of air bubbles inside the module, particularly along the frame and at the level of the ribbons.

It is therefore easy to recognise a delaminated module, even without technical instruments.

If it is impossible to access the installation, one can still identify the presence of delaminated modules by the poor isolation resistance of the plant. When the resistance is too low the inverters do not start, especially in the morning when the level of humidity on the ground is higher. This involves a high loss of the output of the installation.

By law, isolation resistance should be above 40 MΩ/sqm, therefore for a standard module of 60 cells with a surface of 1.65 sqm, resistance should be above 24.5 MΩ.

Unfortunately delamination cannot be solved on the ground, and restoring the isolating capacity of the module would be expensive. In this case, when the problem arises, it is necessary to change the modules, to avoid both further output losses and electrical hazards.

The modules which have been removed, if not excessively delaminated, and only after a detailed evaluation, could possibly be used, one at the time, in micro-installations with low tension.

FuturaSun carefully evaluates its encapsulants and processes, carrying out “gel content test” in order to confirm the quality of the EVA and minimize the risk of delamination.

2016_gel_content_test

Gel Content Test

written by Nicola Baggio

 

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November 11th, 2016 |

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