Evaluation of Cell Cracks in Crystalline Silicon Photovoltaic Modules Using Imaging Techniques

The number of photovoltaic systems installed worldwide has risen sharply over the past 10 to 15 years. However, as operating times increase under harsh environmental conditions, various anomalies and faults are increasingly becoming apparent in the components, which can affect both the performance of the systems and their electrical safety and service life. Cell cracks and microcracks in crystalline silicon PV modules are among such anomalies and can impair module performance. The number of modules with known cell cracks has exploded since the introduction of electroluminescence measurements in solar parks and due to large-scale measurement campaigns, but the significance of the findings has not been systematically analyzed.

Despite various fault catalogs and classifications, there are still no generally accepted, binding evaluation standards or forecasts that describe the impact on a system's energy yield. The finding of “cell cracking” therefore regularly leads to uncertainty and lengthy legal disputes. This currently harms mainly small and medium-sized companies, which have invested well over €50 billion in photovoltaic systems in Germany alone. At the same time, the PV system market will grow both in Germany and worldwide. Defining a standardized procedure and uniform standards for evaluating cell cracks in order to establish the necessary legal certainty and prevent costly disputes is therefore in the interests of module manufacturers, project developers, investors, operators, and insurance companies. The PV-Riss funding project is dedicated to this task in order to close the normative gap.

The project work focuses on creating an internationally accepted classification and evaluation system for cell cracks (IEC Technical Specification (TS), published under the identifier Electroluminescence (EL) of Photovoltaic Modules – Terms and Classification” VDE SPEC 90031). To this end, a standardized evaluation basis, including a statistical analysis of module selection procedures, is being developed, which will be prepared specifically for German experts and also initiated as an international standard document (IEC TS). Finally, the results will be transferred to a standard proposal (IEC New Work Item Proposal). This will enable warranty claims and potential safety risks to be better assessed and legal certainty for all parties to be guaranteed.

The investigations carried out as part of the PV-Riss project aim to develop a scientific basis for damage prediction for current cell and module technologies.