Cracking in Solar Backsheets Not Correlated with Climatic Conditions_ Report

DuPont has released its ‘Global Photovoltaic Reliability Report’ with findings from studies conducted on solar modules across the globe to track material degradation and how it affects module performance.

The 2020 field report tested around 3 GW worth of solar installations comprising over nine million solar panels from 551 installations and found that defects were exhibited by around 30% of the solar modules and 16% of the backsheets. The previous years’ report found total module defects of 34%, total backsheet defects of 14%.

The DuPont Global Photovoltaic Reliability Program identified different types of defects in modules which included:

  1. Backsheet defects: outer-layer (the side exposed to the air) and inner-layer (the side facing the cell) cracking, delamination, yellowing
  2. Cell and interconnect defects: corrosion, hot spot, snail trails, broken interconnect, cracks, burn marks
  3. Encapsulant defects: discoloration, browning, delamination
  4. Other defects: glass defects, loss of anti-reflective (AR) coating, junction box

The company said that it identified a rapid increase in cracking in polyvinylidene fluoride (PDVF) backsheet, noting that the overall outer layer cracking rate of PDVF backsheets increased by over three times compared to the previous year. These defects directly affect the module’s power generation capacity and can cause other issues like delayed inverter starts, ground faults, and even fires.


Backsheets defects by degradation mode

It said the PVDF outer-layer cracking defect rates rose from 5% to 23% between the fourth and ninth year of installation of the solar modules in countries like China, Europe, India, and North America. Deeper backsheet cracks have led to backsheet delamination, exposing the core layer, and in some cases, leading to inverter tripping and ground faults.

“Delamination and cracking were observed in multiple double glass module installations,” according to Kaushik Roy Choudhury, senior scientist and global technology leader at DuPont Photovoltaic Solutions, the solar wing of DuPont.

“Delamination appears to originate near edges of a module or at individual cells, while cracks likely originate at scratches or chips on glass surfaces and edges or at stress risers introduced by the racking system,” he added.

Mercom has previously reported on how the inferior backsheets can cut the overall life of solar projects. Due to the pressure of low tariffs, the quality of components used in solar projects is usually the first casualty. Most of the cost of building a project still goes towards procuring solar modules, and this is where the price is prioritized over quality.

The study, which covered different regions across North America, Europe, Asia, and the Middle East, also identified that climate and cracking were not correlated as cracking was observed in all kinds of weather conditions.

In a recent webinar conducted by Mercom, experts discussed PV module quality deficiencies identified from field installations, penetration of new PV technologies in the Indian space, and their advantages. You can view the webinar here.

Last year, Mercom interviewed Rajaram Pai, Business Leader, E&C South Asia, at DuPont India, who explained the importance of backsheets in solar projects. Read the full interview here.