Takeaways from the PVEL 2021 reliability scorecard

High quality modern solar modules should be made to last on rooftops for over 50 years or more, but are all the manufacturers doing their best to make sure their solar products meet the criteria? It is crucial for the PV module to go through rigorous testing before installation. These tests are critical to determining the quality and performance of modules under environmental conditions, as well as confirming they meet mandated safety requirements.


In BISOL Group, we care deeply for quality therefore we use only top-notch components that ensure higher energy yields and lower degradation throughout the life of a solar module. For example, junction box that we use in BISOL is non-potting, and more expensive. The main advantage is a possible diode exchange inside the junction box - instead of changing the whole module. We strive for our modules to work perfectly while resisting all climatic conditions, therefore using our own climate chamber in BISOL Production is a great test to grant product’s reliability. In the last 12 months, we have replaced almost all machines with state-of-the-art automated lines. By implementing the most progressive M6 dimension half-cut cells (166 x 166 mm) and multi-busbar technology with the advanced 9 thin wire busbars, we increased power and conversion efficiency compared to other modules on the market. Our success primarily relies on the focus on R&D, performance testing and incomparable quality control.


PV magazine published a valuable review of solar modules stress tests that simultaneously expose modules to multiple stresses as if they were in the natural environment. We find the main points of PV magazine’s article we are publishing below in a shortened version extremely important, which is why we decided to share them with you – our esteemed readers and customers.


The annual publication from PV Evolution Labs shares results from solar panel stress tests focused on specified and verified bills of materials.


PV Evolution Labs (PVEL) has released its 2021 Reliability Scorecard. The annual publication is a collection of results from solar panel stress tests focused on specified and verified subcomponent bills of materials.


A few highlights from this year’s results:

  • The highest failure rate for a part, submitted by one-third of manufacturers, was junction box failure. These failures were observed visually prior to testing, offering a simple checkpoint for installers as solar panels are unpacked onsite.

  • New solar cell technologies and general practices – multi-cut cells, monocrystalline, multi-busbar – are showing strong performance characteristics versus their predecessors of single large cells, multicrystalline, and 3-4-5 busbars.

  • Thin-film, IBC, and glass-glass solar panels show lower levels of degradation. This aligns with 25 years of First Solar observations, SunPower’s 40 years of useful life argument, as well new warranties from glass-glass module manufacturers.

The group’s newest product test, the Mechanical Street Sequence (MSS), seeks to discover how larger solar panels now deployed in more complex environments will potentially develop microcracks and degrade over the next several decades.


PVEL said that its MSS aligns with the forthcoming IEC 63209 technical specification for extended reliability testing. It said the IEC 61215 certification standard only requires static mechanical loading, and PV modules will pass if they exhibit no visible damage when evaluated by eye and have less than 5% power loss.


To start all testing processes, including this MSS, PVEL observes the production of each solar panel they test, from the opening of the raw materials through every step of production, until they are palletized and shipped with tamper-proof tape. The below electroluminescence imaging shows a panel’s progression through the three main steps of MSS – static mechanical load (SML) – #2, dynamic mechanical load (DML) – #3, and environmental stress – #4.


In the SML testing phase, modules are mounted on two rails and secured at typical ground-mount clamping locations. They then undergo three rounds of one-hour downforce and one-hour up-force at 2,400 pascals.


For the DML testing, there are 1,000 cycles of alternating positive and negative loading at 1,000 pascals. As part of the simulated environmental stress, modules undergo 50 thermal cycles from 85 C to -40 C, then 10 cycles of humidity freeze, high heat, and humidity followed by a rapid drop to freezing temperatures.


The report said that, in general, solar panels from the last five years show higher levels of field degradation. This should not be too surprising as more than half of the world’s solar deployment has occurred over the same time period.


If we were to focus on one technology among the many which make up a modern solar panel, the report suggested that module encapsulation should get our attention. Variations in the encapsulant formulations were the primary factor affecting the degradation rate.


An aerial-infrared analysis submitted with the report by Heliolytics showed that a manufacturer’s size does not correlate with field reliability.


While the solar panel failure rates noted here are trivial for residential and small commercial customers with even 100 panels, the higher failure rates will add significant labor hours when it comes to gigawatt-scale facilities.