What are the reliability concerns with conventional module technology?
While most of the Indian investors are concerned over the reliability and degradation of solar PV modules, it is important to understand different aspects of solar PV module manufacturing technology which affect the reliability of a PV module. Typically a PV module is made from C-Si wafers, the biggest concern is the purity of C-Si wafers used in the cell manufacturing. Most of the C-Si PV module manufacturer are facing negative profit margins and in this scenario it may be possible that some of the manufacturer can cut corners while selecting inferior quality silicon wafers which contributes to significant part of overall PV module cost.
In recent years some of the PV modules have started failing in first two years only, while expected life is 25 Yrs. Some of the typical defects apart from the purity of C-Si include the degradation of coatings the protect panels, the encapsulant, backside cell architecture etc. While selecting solar panel no one knows the industry wise defective solar panel and even if the defect are discovered they are not publicise due to confidentiality agreement. Investors are having quality concerns especially to the Chinese manufacturer and it is important to access the supply chain of the manufacturer before finalizing any purchase decision. It is very difficult to access the quality of PV module because the material use in manufacturing keeps changing with reference to their supplier’s arrangement and many times module manufacturer are reluctant to share information about their supply chain.
While most of the solar companies are facing tuff time and filing bankruptcy it is harder to believe that some of the reputed manufacturer may be substituting cheaper material and untested materials due to cost concerns. Some of the large manufacturer generally offload their manufacturing requirement to the small manufacturer which have typical module lamination facilities often these small facilities produce PV module in the name of large manufacturer as per the subcontracted terms & conditions, however these large manufacturer’s have no control over the subcontracted small manufacturer’s. There are lot of shortcuts taken in order to save cost by the small manufacturer and its results in poor quality in PV modules. The most crucial part is lamination of the solar cells by a thin film which protects the cells from moisture, and the encapsulant that seals the cell between the layers of glass. There they huge quality concern in this lamination process and it affects the long term reliability and degradation rate of PV modules.
Recently a third party testing organisation STS (Senergy Testing Solutions) found that the defect rate of Chinese module was about 8%. The major failure were found during the testing of PV modules for thermal cycling, damp heat test, hot spot test, humidity freeze test, and mechanical load test.
Most of the PV module manufacturer provide 25 years warranty, however these warranty have a lot of fine print. These warranty generally do not covered. the cost of transportation, removal, and re-installation, nor do they cover the loss of revenue due to panel not working during our recent visit to various solar PV sites we have also noted the cracks in PV modules which is not visible through normal eye and can only we seen through a infra-red camera. Due to increasing troubles in PV modules the third party testing organisation have started testing of these modules for IEC qualification. Fraun-hoffer has tested 1776 PV modules for IEC qualification and found about 20% PV module fail during testing. Fraun hoffer also noted the number of defects in PV material. In front and/ or back cover glass, there were instances of corrosion, abrasion, frosting, and breakage.
Some of the large companies have tried to address the reliability issues and have established module testing laboratory in the plant itself to assist the quality of there modules.
Article By: Dr. Sanjay Vashishtha & Kapil Dev Sharma