Where do cracks appear in the back sheet?

Crystalline solar modules consist of silicon solar cells embedded in two polymer films. This composite is usually laminated between a front glass and a backing sheet. This polymer-based backing sheet protects the solar cells from environmental influences. During an inspection of the solar generator, chalking, cracks, breaks, or scratches may become visible.

How can you detect cracks in the back sheet of the module?

For ground-mounted systems, cracks, breaks, and scratches are usually visible with the naked eye. Only very shallow scratches are difficult to detect. For rooftop systems, it is somewhat more difficult. If the angle of the modules is large enough, the cracks are visible during an inspection without further measures. In the case of modules mounted flat or laid parallel to the roof, such cracks are usually only  noticeable when the modules are uninstalled or when the cracks are so large that they cause further faults. They can then be detected by means of insulation measurement or via error messages in the monitoring system.

What causes damage to the backing sheets?

A common cause of cracks, breaks, and scratches in the backsheet is thermal or mechanical stress on the solar modules. These can also be caused by UV radiation on the back of the modules. However, it is also possible that internal thermal or mechanical stresses, such as hot spots, cause cracks in the backsheet. Careless handling of the modules during transport or installation can also lead to cracks in the backsheet.

What is the risk of damaged backing sheets?

Very shallow scratches do not necessarily pose a risk. However, they can be a sign of mechanical or thermal stress. If this stress continues, the shallow scratches can develop into deep cracks. These can then cause moisture to penetrate the module. This can lead to corrosion within the module. As a result, a loss of performance can no longer be ruled out. Insulation faults can also occur.

How can damage from the backing sheets be prevented, and is the defect repairable?

Since the backing sheet is an integral part of the solar module and is permanently attached to it, it is usually not possible to replace it. It is possible to repair the backing sheet. However, this often only solves the problem if the cracks were caused by incorrect handling of the modules during transport and installation. To do this, however, the cracks must be detected early enough before moisture has already entered the module. If external or internal mechanical and thermal stresses are the cause of the cracks, repairing the backing sheets will hardly solve the problem. The safety risk may still exist. In such cases, it may be worthwhile to replace the module. When replacing the module in question, it is particularly important to ensure that the replacement module matches the other panels in the string and in the system. You can find suitable replacement modules on the SecondSol online marketplace.