Kiwa PVEL’s 10th module testing scorecard highlights the challenges facing module manufacturers in 2024

PV cell and module manufacturing moves fast. As we’ve observed previously on this blog, both new cell and module technologies are making the transition from pilot to commercial production at breakneck pace.

The payoff of the rapid technological progress of solar manufacturers is more efficient, powerful, and economic modules for our customers’ roofs and projects – but it also brings with it risks. We’ve seen it in the past: new technologies come onto the market, and it is only once they are being installed at scale that new forms of degradation or weaknesses emerge.

The situation is further complicated in 2024 as module makers in fierce competition on price. With low prices comes pressures on cost, which can lead manufacturers to look for cheaper materials or novel ways to make savings in production. And it can result in corners being cut when it comes to quality and durability.

Given these market dynamics, quality assurance and testing remain important ways to gain insights as to whether certain manufacturers and module series will continue to perform as intended after 20 to 30 years on the roof and under the harsh Australian sun.

10th Reliability Scorecard

Last month, quality assurance laboratory Kiwa PVEL released the 10th edition of its PV Module Reliability Scorecard. The publication is a summary of the findings from its Product Qualification Program (PQP). The PQP includes a range of reliability and performance tests that go far beyond industry standards.

Modules that pass one or more of the particularly rigorous PVEL tests are awarded the status of “Top Performer”.

In 2024, 53 module manufacturers, including 388 module types, achieved “Top Performer” status in at least one test category – an encouraging trend. However, less than 6% of the modules tested achieved the status in all six reliability categories, and only nine module makers did so along with achieving the status in the PAN (reported and modelled energy) category. 

After a series of severe hail events in the U.S. in recent years, PVEL added a new category this year – for modules that did not see glass breakage after being exposed to hail balls that were 35 mm to 55 mm in size.

A decade as “Top Performer”

Digging into the results, it is pleasing to see that Trina Solar is in the rarefied air of having cleared the high bar of achieving Top Performer status in all seven tests in this latest round. Looking back across the past decade, Trina is one of only three companies that has achieved that status every year.

Alongside Trina, the other three companies that have been consistent Top Performers in this way are fellow Chinese giants Jinko and JA Solar.

BayWa r.e. proudly stocks the Trina Solar Vertex S range for its customers right around Australia.

In a statement, Trina noted that its Vertex N 720W module was one of only four that achieved Top Performer status in all seven tests this year. “The recognition is a testament to our commitment to supplying customers with the highest quality and best-performing PV modules,” said Trina’s head of branding and marketing Cao Yunduan. 

TOPCon durability

With the rapid switch from p-type cell technology to n-type, some concerns have been raised as to the durability of these high-efficiency products when exposed to challenging environmental conditions – in particular hot and humid climates. In light of this, the PVEL thermal cycling testing yielded some interesting results.

The thermal cycling testing conducted by PVEL for the scorecard goes beyond industry standards. This means that modules are tested for 600 thermal cycle durations, rather than the standard 200 (IEC 61215). Thermal cycling exposes the module to extreme temperature swings, replicating what they will experience when it is very hot during the day and then cold at night.

While after 200 cycles PVEL observed that the modules it tested performed “exceedingly well”, some showed concerning levels of degradation after the full 600 hours. In the EL (electroluminescence) example below, power loss of more than 5% is evident.

PVEL attributes this degradation to TOPCon cell makers having made the switch to metallization pastes that contain aluminium along with silver. Aluminium can be prone to corrosion.

Encouragingly, it appears that cell makers are addressing this problem, through the application of laser processes in production that allow the aluminium content of the pastes to be reduced. It is likely that this process was not applied to all the TOPCon products tested for the 2024 scorecard.

In its damp heat testing, relevant to modules installed in hot and humid climates, PVEL pushed modules far beyond what is specified by IEC/UL standards. PVEL tested modules for 2000 hours, twice that of the standard.

Here too, while the headline results were encouraging – median degradation after 2000 hours was less 1.6% – PVEL reports that the “the number of outliers and failures increased.”

In one such outlier result, delamination of the module was evident, “with bubbles encroaching from the glass//glass laminate edge (under the frame) to the bussing ribbon and onto the cell surface.” PVEL notes this is concerning on the grounds of safety and is non-IEC 61730 compliant.

The cause of delamination, postulates PVEL, is likely cost-reduction measures whereby dual polyolefin (POE and POE) encapsulant is replaced by a combination of POE and EVA. Other possible causes include reduced encapsulant thickness and/or a shorter lamination time.

Dual-glass modules performed better overall under the extended damp heat testing – confirming why manufacturers are adopting the approach, particularly to encapsulate TOPCon cells. 85% of the glass-glass modules tested had degradation by less than 2% after the damp heat test, with that number falling to 46% for glass-backsheet modules.

It is understood that TOPCon cells can be prone to degradation if there is water ingress, hence the widespread adoption of dual glass. However, backsheet manufacturers have been designing products with increased resistance to water ingress, which is likely to be revealed by damp heat testing, and they may well be employed in production if they can achieve cost competitiveness with glass.

Glass in focus

While the adoption of dual-glass encapsulation can assist in keeping moisture out, large-format modules necessitate the use of thinner, untempered glass. There have been increasing reports of glass breakage at utility-scale PV projects – particularly for large-format, glass-glass modules.

Furthermore, severe hailstorms have recently wreaked havoc at some utility-scale projects in the U.S., causing widespread module damage.

To cast light into the risks posed by hail, PVEL included a hail stress sequence test for its 2024 scorecard. Again, the lab pushed beyond the standards firing hail stones from 35 mm to 55 mm in size at the modules.

In the face of these hail strikes, PVEL found that glass-backsheet modules have an advantage. “3.2 mm fully tempered glass//backsheet modules are significantly less susceptible to glass breakage than 2.0 mm heat strengthened glass//glass modules”, PVEL reports.

When exposed to 50 mm hailstones, there was a breakage rate of 89% in dual-glass modules, which typically use 2 mm glass. This fell to 40% in glass-backsheet modules.

Interestingly, breakage only on the rear-side glass was evident in 40% of the dual-glass failures. This is counter intuitive as the front-side glass is where the hail strikes.

PVEL attributes the phenonium of rear-side breakage to the back glass being “typically weaker” due to its holes required for the junction box and the use of “ceramic fritting” applied to the space between cells, which it not universally applied but does boost efficiency.

The 2024 PV Module Reliability Scorecard includes a wealth of information about module quality and durability. It shines a light on the challenges facing module makers in this time of rapid technology change and extreme price pressure.

It also shows that despite these challenges that there is a cohort of manufacturers for which quality remains an upmost priority – a message that can be conveyed to customers wanting a rooftop PV system that will stand the test of time.

“While we applaud the advances in manufacturing and the number of Top Performers listed, we remind buyers to remain vigilant," said Kiwa PVEL’s Tristan Erion-Lorico, in a statement announcing the scorecard’s publication. "We encourage them to explore each page of the scorecard to better understand the range of test results that we're seeing every day at Kiwa PVEL's labs."

To be eligible for inclusion in the 2024 scorecard, manufacturers had to have allowed PVEL to witness the production of the tested modules at one of their factories and in accordance with the testing laboratory’s bill of materials (BOM) test requirements.