Fraunhofer Center for Silicon Photovoltaics CSPCell cracks and microcracks in crystalline silicon photovoltaics modules are caused by various environmental stresses and can reduce the performance and service life of solar systems. However, there is a lack of assessment standards that reliably classify their impact on energy yield. Employees of the Fraunhofer Center for Silicon Photovoltaics CSP in Halle (Saale) have developed a standardized nomenclature of cell cracks and other anomalies in the "PV-Riss" project in order to increase legal certainty for manufacturers, investors, operators and insurers.
Damage to photovoltaic (PV) modules, in particular cell cracks and microcracks in crystalline silicon cells, is caused by a combination of manufacturing-related residual stresses (preloads) and external mechanical, environmental stresses during operation. These can significantly impair the performance, safety and service life of solar systems. Although electroluminescence (EL) measurements are now standard and can be used to visualize cell cracks and other abnormalities, there is still a lack of generally accepted assessment standards and binding criteria for risk assessment or for predicting the effects on performance and safety. Uncertainty about the significance of such findings often leads to legal disputes, which primarily affect small and medium-sized operators. This is currently one of the biggest challenges in the quality assurance and damage assessment of long-term care insurance systems.
With the completion of the "PV-Riss" research project led by the Fraunhofer CSP, a significant step has been taken towards the standardized assessment of cell cracks in crystalline silicon PV modules. The aim was to create reliable criteria for the nomenclature, classification and evaluation of cell cracks. The focus of the research work at Fraunhofer CSP was on the systematic investigation, categorization and evaluation of cell cracks and their effects under laboratory and field conditions. A standardized defect catalog for the classification of cracks was developed, primarily based on EL images, supported by magnetic field images (MFI), as well as infrared photography (IR) and performance data. In laboratory tests with over 200 modules, cell cracks were specifically generated and examined with regard to their behavior with different numbers of busbars and crack patterns. Combined thermo-mechanical load tests and cyclic load profiles were used to investigate the development of cell cracks and their influence on performance degradation and potential safety risks. A specially developed test rig was used for this purpose.
The data obtained will be used for future inquiries as recommendations for assessing and dealing with cell cracks. In addition to cell cracks, which are particularly relevant for older modules, additional categories were also assigned to the other anomalies visible in the EL. These include contacting problems, defects in screen printing, cell defects and degradation patterns due to light degradation (LID, LETID), potential-induced degradation (PID) and UV-induced degradation (UVID) as well as other observations in a comprehensive overview.
Fraunhofer CSP played a leading role in the development of VDE SPEC 90031, which creates a uniform nomenclature for electroluminescence images and supports international standardization processes. "Cell cracks are not a new phenomenon, but their assessment has so far been characterized by uncertainty. With VDE SPEC 90031, we are providing a scientifically sound, reproducible methodology for classification and evaluation for the first time - a decisive step for the quality assurance of modern PV systems. This reduces uncertainties in warranty issues, improves communication between manufacturers, experts and operators and supports more efficient operational management of long-term care insurance systems," says Dr. Bengt Jäckel, project manager at Fraunhofer CSP.
The "PV-Riss" research project was funded by the German Federal Ministry for Economic Affairs and Energy (BMWE) as part of the "WIPANO" program (knowledge and technology transfer through patents and standards). The project partners were Forschungszentrum Jülich GmbH, Anhalt University, Hanwha Q Cells GmbH, Ing.-Büro Kirch, Arp & Kleiss GmbH, Sunset Energietechnik GmbH and the German Commission for Electrical, Electronic & Information Technologies in DIN and VDE (DKE).
(June 11, 2025)