Photovoltaic modules are the core components of photovoltaic power generation. In order to ensure the normal operation of photovoltaic power generation, it is necessary to inspect and maintain the components and components of photovoltaic power plants. Common problems with photovoltaic modules include hot spots, cracks, and power attenuation. Due to these quality issues hidden within the battery panel or occurring after a period of operation of the photovoltaic power plant, it is difficult to identify them during the on-site acceptance of the battery panel, and professional equipment needs to be used for photovoltaic module testing.
Causes of hot spot formation and detection methods for photovoltaic modules
Photovoltaic module hot spot refers to a dark spot where a module is exposed to sunlight and some battery cells are blocked from working, causing the covered part to heat up much more than the uncovered part, resulting in excessive temperature and burning out.
The formation of hot spots in photovoltaic modules is mainly composed of two internal factors, namely internal resistance and the dark current of the cell itself.
The hot spot durability test is a photovoltaic module testing test to determine the ability of solar cell modules to withstand the heating effect of hot spots. By conducting testing of photovoltaic cell components at a reasonable time and process, it is demonstrated that photovoltaic cells can be used for a long time under specified conditions.
Hot spot detection can be carried out using an infrared thermal imager, which can use thermal imaging technology to display the temperature and distribution of the measured target using a visible thermal map.
Reasons for the formation of hidden cracks and detection methods for photovoltaic modules
Hidden cracks refer to the appearance of small cracks in the battery cell, which can accelerate the power attenuation of the battery cell and affect the normal service life of the component. At the same time, hidden cracks in the battery cell can expand under mechanical load, potentially leading to open circuit damage and hot spot effect. The occurrence of hidden cracks is caused by the combined action of multiple factors, such as uneven force on components or severe shaking during transportation and reshipment, which may cause hidden cracks in battery cells.
Photovoltaic modules undergo EL imaging testing before leaving the factory, using an EL detector. The instrument uses the electroluminescence principle of crystalline silicon, and uses a high-resolution CCD camera to capture the near-infrared image of the module, to obtain and determine the defects of the module. The EL detector can detect whether photovoltaic cell components have hidden cracks, fragments, solder joints, grid breaks, and abnormal phenomena of single cell batteries with different conversion efficiency.
Classification of power attenuation and detection methods for photovoltaic modules
Photovoltaic module power attenuation refers to the phenomenon where the output power of the module gradually decreases with the increase of lighting time. The power attenuation phenomenon of photovoltaic modules can be roughly divided into three categories:
The first type is component power attenuation caused by destructive factors;
The second type is the initial photoinduced attenuation of the component;
The third type is the aging attenuation of components.
Among them, the first type is the controllable attenuation during the installation process of photovoltaic modules, such as strengthening the unloading, transportation, and installation quality control of photovoltaic modules, which can reduce the probability of hidden cracks and fragmentation of module battery cells.
The second and third categories are urgent process issues that need to be addressed in the production process of photovoltaic modules. The power attenuation test of photovoltaic modules can be completed through the I-V characteristic curve tester of photovoltaic modules.
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