Enhancing Solar Quality: Key Insights and Recommendations from Kiwa

Energy transition is being prioritised by economies around the world as a crucial step toward achieving net-zero targets. Among renewable energy sources, solar power is leading the charge and defining this new era of sustainable development. Both private and public entities are formulating policies to integrate solar energy into their growth strategies, and ongoing research aims to enhance the key factors that affect the quality of solar technology. These factors are essential for the successful integration of solar into the broader energy mix, helping it compete effectively with conventional energy sources.

Recent technological advancements have significantly improved solar technologies, making them more attractive alternatives. More firms are now focusing on improving key quality parameters to ensure solar energy’s reliability, durability, and affordability. One of the most authoritative reports on solar PV quality is provided by Kiwa PVEL and Kiwa PI Berlin, which offer guidance on acceptable quality parameters across multiple dimensions of solar module performance.

In this blog, we explore the main quality parameters, assurance mechanisms, and recommendations by Kiwa to ensure higher reliability in solar PV modules.

Key Quality Parameters for Solar PV Modules

Quality assurance (QA) plays a vital role in the solar PV industry as it ensures that modules deliver expected performance and remain reliable throughout their lifespan. Thus, robust QA processes are essential for minimising risks, enhancing durability, and guaranteeing that solar PV systems generate the anticipated energy output. Since solar modules are exposed to harsh weather, UV radiation, and other environmental challenges, continuous and thorough QA is crucial to ensuring long-term reliability and safety.

The introduction of advanced cell technologies like TOPCon and HJT has added complexity to the manufacturing process, requiring stricter QA measures. Although these technologies offer higher efficiency, they are more vulnerable to variations in material quality and production consistency. Even minor deviations can lead to performance issues or premature failures.

To address these concerns, Kiwa PVEL developed the Product Qualification Program (PQP). This program guides manufacturers and buyers to maintain high-quality standards for solar modules.

Quality Assurance: A Multi-Tiered Approach

Kiwa’s quality assurance process for solar modules focuses on four key areas – the Product Qualification Program (PQP), Pre-Shipment Inspection (PSI), Batch Testing, and Ongoing Reliability Monitoring (ORM). These measures ensure that solar modules meet stringent quality standards, delivering reliable performance in a variety of conditions.

Product Qualification Program (PQP)

The PQP is not a simple pass/fail test. Rather, it is a comprehensive set of qualification tests that assess module performance under real-world conditions. This allows both manufacturers and buyers to gauge how the modules will perform over time. For example, a module may show weaker results in tests like Potential Induced Degradation (PID) but could still be acceptable for installation in regions where PID risks are low.

The PQP establishes clear thresholds for power degradation and overall performance. For instance, modules subjected to thermal cycling or damp heat tests should exhibit less than 3% degradation to pass. Results showing degradation between 3% and 5% are classified as conditional and require a Root Cause Corrective Action (RCCA) analysis to identify and address the problem.

Pre-Shipment Inspection (PSI)

Pre-Shipment Inspections play a critical role in verifying that solar modules meet specified requirements before they are shipped to buyers. PSI includes visual inspections for physical defects, electrical performance tests, bifaciality assessments, and electroluminescence (EL) imaging to detect micro-cracks or hidden faults.

A review of 774 batches in 2022-2023 by Kiwa PI Berlin revealed varied defect rates across different manufacturers, underscoring the complexities of solar module production and the importance of stringent inspections.

Batch Testing

To ensure consistent quality, random samples from each production batch are subjected to IEC/UL stress tests. These short-duration tests measure power output, check for potential-induced degradation, and assess the module’s mechanical load resistance. This process enables manufacturers to catch any quality issues early in production, reducing the risk of defective modules reaching the market.

Ongoing Reliability Monitoring (ORM)

ORM ensures long-term reliability by monitoring module performance over time. Modules from various production batches are tested under real-world conditions, including exposure to UV light, hail, and mechanical stress. For advanced technologies like TOPCon, which are particularly sensitive to UV degradation, ongoing testing is crucial to guarantee durability and sustained performance. ORM helps ensure that these advanced modules can withstand harsh environmental conditions over their lifespan.

Recommendations to Raise the Bar for Quality

Kiwa has made several recommendations for module buyers to enhance the quality of solar PV systems, setting higher standards for reliability.

First, Kiwa advises buyers to establish specific Acceptable Quality Limits (AQLs) for each defect category. These limits should be based on factors such as product technology, batch size, and the specific site conditions. For critical defects, an AQL of 0 is recommended, while a 1.5 AQL for major defects is considered a reasonable threshold.

Buyers should ensure that modules undergo Pre-Shipment Inspections (PSI) according to ISO standards, including thorough visual inspections and electroluminescence testing. Early identification of issues like microcracks, weak soldering, or contamination can significantly reduce the risk of failures during installation or operation.

In addition, buyers are encouraged to request Batch Testing to assess the performance of solar modules from each production batch. Key metrics, such as power output and mechanical durability, should be closely monitored to identify any quality concerns before the modules are deployed.

Finally, continuous quality monitoring through Ongoing Reliability Monitoring (ORM) is essential for maintaining consistent module performance. Regular testing for hail and UV resistance is particularly important in regions exposed to extreme weather conditions, ensuring long-term reliability.

Key Results & Analysis from Recent Testing

Kiwa’s report offers valuable insights into the current state of the solar PV industry, showcasing both progress and remaining challenges in advancing solar technologies.

The PQP tests indicate that most modules tested in 2023-2024 experienced less than 3% power degradation, marking a significant improvement compared to previous years. This suggests that more manufacturers are producing higher-quality modules capable of maintaining long-term performance.

However, Pre-Shipment Inspections (PSI) conducted on 774 batches of solar modules revealed that only 76 batches were completely defect-free. Many modules showed issues such as microcracks and frame defects, underscoring the importance of stringent quality controls throughout the manufacturing process.

Recent testing has also highlighted the importance of ongoing validation for hail resistance, particularly for glass-on-glass modules. Modules with advanced technologies like TOPCon and HJT cells, which are more susceptible to UV damage, demonstrated better-than-expected performance when subjected to regular monitoring.

As solar energy becomes a cornerstone of the global clean energy transition, ensuring the quality and reliability of solar modules is essential. Kiwa’s comprehensive testing protocols—including PQP, PSI, batch testing, and ORM—provide manufacturers and buyers with the tools to uphold the highest standards. By implementing these recommendations and maintaining robust quality assurance practices, solar developers can reduce risks, enhance system performance, and secure a stronger return on investment.