PV Module Testing: Recommended Pass/Fail Metrics by PVEL and PI Berlin
The importance of rigorous testing in the solar industry cannot be overstated. With the growing demand for reliable and efficient photovoltaic (PV) modules, it is crucial for manufacturers and buyers to have clear guidelines on what constitutes acceptable performance. In a recent report by PVEL and PI Berlin, recommendations for pass/fail metrics for PV module testing have been outlined, shedding light on the industry’s standards and expectations.
Historically, the Kiwa Group and its subsidiaries have been key players in the testing of solar modules. However, the company has been cautious in imposing strict pass/fail criteria for its testing process, citing the multitude of factors that can impact the suitability of a PV product in real-world conditions. Variables such as regional climate, deployment environment, and material composition are not always taken into account during testing, making it challenging to establish universal pass/fail metrics.
Despite this, manufacturers and buyers have consistently sought guidance from Kiwa PVEL on what results are deemed acceptable. Responding to this demand, the testing group has now provided recommendations for the results of its tests. For instance, modules subjected to thermal cycling, damp heat, mechanical stress sequence, and potential induced degradation testing are advised to be given a passing grade if they exhibit degradation rates of 3%, a failing grade if they exhibit degradation rates of 5% or higher, and a “conditional pass” if they fall within the range of 3-5%.
These metrics are based on the average results of tests conducted by the Kiwa Group, reflecting the industry’s performance standards. For example, in thermal cycling tests, 95% of modules displayed degradation rates of 3% or lower, warranting a passing grade, while only 1% exhibited degradation rates exceeding 5%, resulting in a failing grade. The damp heat and mechanical stress sequence tests also yielded similar historical pass/fail percentages, demonstrating consistency in performance evaluation.
However, the potential induced degradation (PID) testing data showed some variability, with 11% of tests receiving conditional passing grades. This variance can be attributed to the diverse materials and components used in PV module construction, leading to differing degradation rates. As a result, drawing definitive pass/fail conclusions from PID testing has proven more challenging, underscoring the complex nature of module performance assessment.
Terry Jester, managing director for North America at Kiwa PI Berlin, emphasized the significance of these recommendations in elevating industry standards and safeguarding renewable energy investments. He stated, “This white paper highlights key aspects for module procurement and displays our commitment in pushing the industry to higher levels of quality. We believe our updated guidance will be instrumental in advancing the solar industry and safeguarding renewable energy investments worldwide.”
Despite the progress made in establishing pass/fail metrics for various testing methods, the report acknowledges the need for further data collection in certain areas. For instance, insufficient conclusive data on UV-induced degradation has hindered the formulation of formal performance metrics by the Kiwa Group. The uncertainty surrounding UV-induced degradation is evident in the testing data, with a wide range of results observed. While 25% of modules exhibited degradation rates below 3%, 35% fell into the conditional passing category, and 22% received failing grades.
Moreover, the occurrence of “other failures” in UV-induced degradation tests was notably higher at 17%, underscoring the need for additional testing to gain deeper insights into module performance under UV exposure. The lack of comprehensive data in this field highlights the ongoing challenges in setting definitive pass/fail criteria for all testing parameters.
In addition to UV-induced degradation, the report refrains from providing guidance on testing related to PVsyst, a program used for estimating the energy output of solar power plants. Instead, developers are advised to rely on third-party testing from reputable labs for accurate assessments of module quality and performance. This cautious approach underscores the importance of thorough and independent testing to ensure the reliability and efficiency of PV modules.
The integration of PVEL and PI Berlin labs into a single brand earlier this year marked a significant step in enhancing testing capabilities and industry collaboration. Tristan Erion-Lorico, VP of sales and marketing at Kiwa PVEL, highlighted the necessity of this consolidation, stating that manufacturers are striving to produce higher-quality products, necessitating informed decisions on module quality and performance by operators.
In a related development, US renewable power firm Clean Energy Associates (CEA) reported a concerning increase in micro-cracks in PV modules between 2022 and mid-2023, raising questions about the overall quality of modules in the industry. This trend underscores the importance of stringent testing protocols and quality control measures to address potential issues and ensure the long-term reliability of solar installations.
Moving forward, continuous innovation and collaboration within the solar industry will be essential to drive advancements in module testing and performance evaluation. By adhering to recommended pass/fail metrics and staying abreast of evolving industry standards, manufacturers, buyers, and operators can uphold the integrity and efficiency of PV systems, contributing to the growth of renewable energy worldwide.