Photovoltaic: Module cracks, hot spots, and PID effects are three important factors that affect the performance of crystalline silicon photovoltaic modules. Today, I will show you the reasons for cell cracks, how to identify and prevent them.
1. Formation and classification of cracks in photovoltaic modules
Cracks are a relatively common defect in crystalline silicon photovoltaic modules. In layman's terms, they are micro-cracks that are invisible to the naked eye. Due to the characteristics of its own crystal structure, crystalline silicon components are very prone to cracking. In the process flow of crystalline silicon module production, many links may cause cell cracks. The root cause of cracks
External force: The battery will be affected by external force during welding, lamination, framing or handling, testing, etc. When the parameters are improperly set, equipment failure or improper operation will cause cracks.
High temperature: The cell is not preheated at low temperature, and then suddenly encounters high temperature in a short period of time and then expands, which will cause cracks, such as excessive welding temperature, unreasonable setting of lamination temperature and other parameters.
Raw materials: Defects in raw materials are also one of the main factors leading to cracking.
According to the shape of the cell crack, it can be roughly divided into 5 types: tree crack, comprehensive crack, oblique crack, parallel to the busbar, perpendicular to the grid and cracks that penetrate the entire cell.
2. The impact of "cracking" on component performance
The current generated by crystalline silicon solar cells is mainly collected and exported by the busbar lines and thin gridlines whose surfaces are perpendicular to each other. Therefore, when cracks (mostly cracks parallel to the busbars) cause the thin gridlines to break, the current will not be effectively delivered to the busbars, resulting in partial or even failure of the cell, and may also cause debris, Hot spots, etc., at the same time cause the power attenuation of the components.
Third, the method of identifying "cracks"
EL (Electroluminescence, electroluminescence) is a kind of internal defect detection equipment of solar cells or components, which is a simple and effective method to detect cracks. Using the electroluminescence principle of crystalline silicon, the near-infrared image of the component is captured by a high-resolution infrared camera to obtain and determine the defects of the component. It has the advantages of high sensitivity, fast detection speed, and intuitive results. The picture below is the test result of EL, which clearly shows various defects and cracks.
Fourth, the reasons for the formation of "cracks"
There are many factors that cause module cracks, and there are many types of cracks, but not all cracks will affect the cells, not to mention "hidden" discoloration, as long as scientific prevention can properly prevent the modules from cracking. During the production process, improper external force intervention should be avoided for the cells, and attention should be paid to the temperature range of the storage environment. During the welding process, the battery should be kept warm in advance (hand welding). The temperature of the soldering iron should meet the requirements. In the process of module production, transportation, installation and maintenance, considering the cracking characteristics of crystalline silicon modules, it is necessary to pay attention to and improve the operation process in each process of installing the power station to minimize the occurrence of module cracks.
Five, the main points of preventing cracks in photovoltaic modules
In the production process and subsequent storage, transportation, and installation, avoid improper external force intervention on the battery cells, and also pay attention to the temperature change range of the storage environment.