Snail Trail on your PV module: A disease or symptom?
Solar PV system looks quite simple. Upto certain extent, it is true too. There is no moving part and technically almost nil O&M requirement. However, as the industry is seeing evolution it is encountering new problems, which were previously not present at least not identified. A snail trail phenomenon is one of those kinds. Small dark lines or partially discoloration on PV modules is known as Snail Trail. In the earlier stage of identification of Snail Trail, it was believed that it is reducing the performance of the solar panel, even leading to the permanent degradation of the modules. Industry was treating this as PV panel disease . However, at that time no one/company was certain about the cause of Snail Trail.
When this phenomenon drew considerable attention of the industry, scientist/researchers considered this as potential topic of research. They executed a series of complex experiments like Electroluminescence (EL) analysis and infrared (IR) measurements were taken by an EL camera, Optical and field-emission scanning electron microscopy and many more. They compared the performance of defected PV module with ‘normal’ working PV modules. The results presented a complete new picture to the market. As per the results, Snail Trail was more of a symptom rather than Disease.
The origin of Snail Trail on PV modules is due to Ag2Co3 nanoparticles. They can absorb and scatter the light resulting in dark discoloration on the module surface. In most of the cases Micropores/ cracks also led to Snail Track. Moisture, oxygen, carbon dioxide and other compounds could gain access through cracks and cell edges or pass through the de-bonded areas between the encapsulation layer and the Si substrates to interact with and oxidize the silver grid. Cracks develop due to a variety of causes and can occur during production, transportation and installation. It is believed that larger numbers of cracks develop in the cells due to poor handling.
However, as solar energy enthusiast, we should not be much worried about the Snail Trail. Relying on the researcher’s studies, yearly power degradation due to snail trail is approximately 0.56%, which is considered to be normal degradation range. However, losses due to cracks can severely impact the energy yield on permanent basis. So, we should improve our PV module handling procedure.
Image reference: http://uwaterloo.ca/centre-advanced-materials-joining/sites/ca.centre-advanced-materials-joining/files/uploads/files/p_peng_rsc_adv_2012_0.pdf
Written By: Gaurav K. Sharma