EN
What is EL Imaging?
EL Imaging is a new technique used in the detection of defects that arise during the lamination and interconnection of solar panels. During the lamination and interconnection of solar panels, EL Imaging is one of the few techniques that can enable defect detection without the destruction of solar panels. EL Imaging relies on the controlled flow of current through a solar panel to produce an infrared image of the panel. In that image, minor cracks, poor quality solder joints, and broken solar cells appear as dark spots. The newer generation of EL mobile laboratories can identify defects that are as small as 50 microns (less than a human hair). This technology allows manufacturers to receive immediate feedback while panel production is still ongoing. We also have a scanner located after each heat treatment to identify and manage stress and heat damage while the panel is still in the heat treatment stages. The machine will also reject a panel before it is encapsulated, which protects the panel from “hidden defects” that will degrade the efficiency of the solar panel during its operational life (typically the decline is 15 percent to 25 percent).
Correlating EL Defects with STC Performance Deviation (±3%)
Due to defect morphology's ability to predict the loss of STC performance, our statistical modeling of 50,000 panels shows that micro-cracking that spans more than 10% of a cell's surface area is guaranteed to exceed a deviation of PMAX by +/- 3%. This type of modeling allows for predictive flash testing, where EL defect metrics are entered into a machine learning algorithm to determine IV curve anomalies with 92% accuracy, which is significantly better than a visual inspection.
Defect Type Average Power Loss Rejection Rate
Finger interruptions 4.2% 98%
Corner micro-cracks 2.8% 65%
Full-cell fractures 18.7% 100%
Due to the emergence of defect clusters, our production systems automatically modify the laser scribing adjustment, resulting in a 30% decrease in scrap and a Pmax consistency within a +/- 2% batch tolerance.
End-of-Line Validation: Ensuring Electrical Safety and Performance
HI-Pot Testing at 1.5× System Voltage per IEC 61215-2
Panels undergo HI-Pot Testing for electrical insulation and dielectric strength verification. Voltage is applied to panels at 1.5 times the rated voltage per IEC 61215-2 for 60 seconds. Technicians are looking for electrical potential insulation weaknesses and arcing during the test. During the test, the dielectric strength tester measures the amount of current that leaks through the tester. Panels that are greater than 50 microamps per square meter are scrapped. This is the last step to ensure that the panels do not present electrical hazards when installed at various locations around the world.
IV Curve Tracing and Pmax Consistency Checks (±2% Threshold)
IV Curve Tracing is performed post HI-Pot to the panels. This test is performed at Standard Test Conditions (STC). Systems measure Pmax and The systems measure Pmax and enforce a strict ±2% tolerance across production batches. For any deviation, statistical process control (SPC) initiates root-cause analysis and only units that meet performance benchmarks are packaged.
More Testing and Better Testing for Environmental Impact and Durability for Solar Panels
More Solar Panel Certifications
Leading manufacturers are advancing their certifications. Instead of including dual certification as a process control step post manufacturing, it is being treated as a core process control step. InfraMentum explains that when manufacturers merge the standards IEC 61215 for design and IEC 61730 for safety, the solar panels are subjected to as many as 18 different stress tests, including rapid temperature changes from -40 degrees Celsius to +85 degrees Celsius, as well as mechanical, UV, simulated hail (i.e. hail) impacts, and various other fire and electrical safety tests. Assessing the real-world longevity of products that survive this rigorous testing is well over 25 years and includes climates that are hot and desert-like, salty-coastal, and high-altitude mountainous locations.
Extended Stress Testing: 1000h Damp Heat + PID Resistance at −1000V
Advanced labs conduct damp heat testing far beyond the industry standard. Tests usually last 1000 hours at 85 degrees Celsius and 85% relative humidity. This is three times longer than the requirement for the IEC 61215 standard. This type of testing exposes moisture infiltration into the materials BEFORE visible mechanical separation occurs. This is coupled with another critical test where -1000 volts of electrical bias is applied for 96 hours of the test. This type of testing is referred to as accelerated testing. All electrical stress that would normally be applied over the course of years are applied over just a few days. If a PV module continues to perform at > 98% of its initial power output following this type of testing, a manufacturer can be confident that the PV module will yield a field performance data for degradation < 0.5%/year. This is the type of real world PV module test that is almost impossible for a manufacturer to ‘fake’ and is the type of real world test that validates the manufacturer’s claims for durability.
Incorporating Traceability and Process Governance in Supplier Vetting and ISO 9001:2015
Effective governance and excellent traceability systems are imperative in safeguarding the quality of products. All suppliers we have in our network undergo prior verification, which considers the purity of the materials, the dimensional stability over a period of time, and the resistance of the product to aging. Each and every part undergoes either laser engraving or barcoding for the purpose of raw silicon traceability to the final assembled panel. With our level of detail in tracking the production, it is easy to locate the origin of production errors. Likewise, without any operational disruptions, we are able to locate the different production and operational batches in the case of a product recall. Our quality management is put in place according to ISO 9001:2015 and includes everything concerning the internal reviews, the resolution of nonconformities, and continual improvement initiatives. Specifically, in Clause 8.5.2, it is stated that we should have records that are traceable to the origin of the materials. Annually, we plan our evaluation of our suppliers to determine whether we are compliant to the requirements.
Continuous quality control is integrated with every component of the supply chain, instead of being treated as merely a box to check.
FAQ
What is EL imaging?
Controlled current is run through a solar panel to find defects like micro-cracks, faulty solder joints, and broken cells. Each defect appears as a dark spot in an infrared image. These images are used to conduct EL imaging.
What is HI-Pot testing, and what is its significance?
HI-Pot testing is a type of dielectric strength testing, where insulation weakness or arcing is tested by exposing the panels to 1.5 times their rated voltage. It confirms the electrical safety of panels in relation to their intended countries of deployment.
What is involved in dual certification?
Dual certification is a combination of compliance with IEC 61215 and IEC 61730, which means about 18 stress tests are performed in the course of production. Sustainability of panels in different climatic conditions is ensured after passing dual certification.