Where can you find snail trails?

Snail trails are a phenomenon of wafer-based silicon solar modules and represent a discoloration of the silver-containing front side metallization (metal mesh, cell grid). The cause of this local cell discoloration are cell cracks, depending on the embedding film used, which usually consists of ethylene vinyl acetate (EVA). These EVA films protect the cells from the effects of the weather and UV radiation and provide electrical insulation for the cells. Since the solar cells are only about 0.2 millimeters thick, they are prone to hairline cracks. These are called microcracks.

How to recognize snail trails in the module?

This module error can be seen with the naked eye. It often looks as if snails have left their typical slime trails, except that these meandering discolorations are under the front glass of the modules. They can be easily distinguished from peeling encapsulation films, blistering and delaminations based on their typical shape. With the latter, a flat discoloration can be seen, while the snail trails appear as individual, precisely definable lines.

What is the cause of slug trails?

These rather linear discolorations indicate microcracks (microcracks) in the crystalline silicon solar cells. The snail trails are caused by substances in the EVA foil diffusing through these cracks and reacting with the silver of the grid on the front of the cell, leading to the typical discoloration observed.

What is the danger of slug trails?

Since snail trails are a sign of microcracks, i.e. cell breakage, they can also lead to a loss of performance. Whether this is the case and how high the loss is depends on the type and spread of the microcracks and the resulting inactive cell areas in the solar cell. The loss of performance can also develop over a longer period of time. Therefore, such modules and the yield values ​​of the system should be kept in mind during regular system inspections.

How can you prevent slug trails and is the error repairable?

Since snail trails can be traced back to microcracks that occur during production, transport, installation and operation (hail, high snow loads, strong winds) of the modules, the operator of the solar system cannot explicitly prevent or prevent this error. A specialist can be consulted with regard to a possible replacement of the affected modules. This can make the cracks and fractures in the cells visible using electroluminescence, assess the extent of the loss of performance and assess precisely whether it is worth replacing the affected modules. Above all, it is important to ensure that a replacement module fits the other panels in the string and in the system. You can find suitable replacement modules on the SecondSol online marketplace.