PVEL Scorecard 2022 Confirms Improving Quality, Performance From Top Manufacturers

PV Module Reliability Scorecard 2022 is out. 25 manufacturers have made it to the list. 3 India based manufacturers, Adani Solar, Vikram Solar and Waaree Solar make it to the list, although only Adani Solar seems to have performed creditably across all parameters.

The Germany based PVEL’s scorecards summarise results from the independent testing and names specific PV module model types as top performers. Seen as one of the most credibility benchmark for testing of modules, certification here is one of the more widely accepted standards. A strong performance means wider acceptance and stringer exports for many. One reason why Chinese brands dominate the list.

Although PVEL’s scorecard lists top performers by model type, yet they represent unique bills of materials (BOMs) that have undergone testing in product qualification programme (PQP) for PV modules. So, there is a scramble among the manufacturers to make to the coveted scorecard.

Scorecard Eligibility: To be eligible for the scorecard, manufacturers must have:

• Completed the factory witness within 18 months of 2022.
• Submitted modules to all reliability test sequences in the PQP.
• Submitted at least two factory-witnessed PV module samples per test sequence.

Scorecard Scoring: The 2022 PV Module Reliability Scorecard shows top performers for six PQP test categories. Not all products or model types are represented in every test.

Four principles govern Product Qualification Programme for PV modules.

1. Empirical data: The PQP provides empirical metrics for revenue and energy yield modelling.
2. No hand-picked samples: Auditors witness production of all test samples and record BOM details.
3. Standard processes: The PQP tests all BOMs in the same way with calibrated equipment and in consistent test environments.
4. Regular program updates: Test sequence updates provide data on new technologies and manufacturing techniques.

The key takeaways from relevant parameters werre:

Thermal Cycling
PVEL’s thermal cycling (TC) test assesses the capacity of PV module to withstand changes in temperature. While ambient temperatures vary daily and seasonally in most solar markets, top-performing TC results are most critical in locations where temperatures are much lower at night than during the day, such as deserts and high-altitude regions.

Key Takeaways

• This year’s TC results are the best in PVEL’s history: 90% of BOMs tested degraded by less than 2%, with a median of 0.72% and average of 0.97%.
• Over 70% of BOMs tested were multi-busbar (MBB). BOMs with MBB cell interconnections achieved better test results than older busbar designs on average, indicating that MBB soldering issues can be addressed.
• Two BOMs that passed IEC 61215’s TC 200 requirements ultimately degraded by more than 5% after PVEL’s TC 600 test, which demonstrates that accelerated testing remains necessary for risk mitigation.

Mechanical Stress Sequence
PVEL’s mechanical stress sequence (MSS) has two primary objectives: to determine whether cells in PV modules are vulnerable to cracking under pressure and if cell damage is likely to cause power loss or lead to hot spots (a potential safety risk) in the field. Strong MSS results are most important in project locations with extreme weather events and conditions, including heavy snow and high winds.

Key Takeaways

• While 72% of BOMs are Top Performers in MSS, PVEL observed a significant number of failures during this sequence in 2022 Scorecard testing. The most common failure mode was broken glass, not power loss.
• More than 80% of modules greater than 2100 mm tall are Top Performers, compared to just 68% of modules less than 2100 mm. This indicates that larger modules can be optimized for mechanical strength.
• Glass//glass BOMs only failed because of glass breakage, not cell-level damage. Glass// backsheet BOMs were more susceptible to cell cracking, but less susceptible to glass breakage.

PID
Potential-induced degradation (PID) is triggered by high PV system voltages on ungrounded systems. PID is more likely to occur in projects that use transformerless inverters, especially in high temperature and high humidity environments. While PID is sometimes reversible, severe and permanent PID can decrease energy yield by as much as 30%.

Key Takeaways

• PID results improved markedly as compared to 2021, when PVEL claimed to have reported the highest mean and median PID rates in its history. Yet PID remains unsolved: 5% of BOMs tested for this Scorecard degraded by >8% after PID testing.
• While BOMs with EVA encapsulants were Top Performers, BOMs with POE encapsulants were generally less susceptible to PID. 93% of POE BOMs are 2022 Top Performers vs. 72% of EVA BOMs.
• Average power loss for monofacial modules was slightly lower than the average front-side PID rate for bifacial modules. In contrast to 2021, front- and rear-side PID rates for bifacial modules were tightly aligned this year.

LID + LETID
Light-induced degradation (LID) and light-and elevated temperature-induced degradation (LETID) are cell-based phenomena triggered by light exposure that should be considered in energy yield models. LID rates vary by cell technology and typically stabilize within a few days or weeks of field operation. LETID mainly affects PERC cells. Research suggests it is most severe in hot climates.

Key Takeaways

• Almost all BOMs tested in this category were top performers this year, and only one BOM had a degradation rate over 3%.
• Improved LID+LETID test results were largely driven by advancements in cell doping, a key step of the manufacturing process for crystalline cells.
• Commercially available products sold under the same model type as LID+LETID Top Performers may behave differently in the field. Manufacturers often offer several BOMs to clients with varying performance and cost.