PV modules are: hot spots, cracks and power attenuation. Because these quality problems are hidden inside the panels or occur after a period of operation of the photovoltaic power plant, it is difficult to identify the panels when they enter the site for acceptance, so it is necessary to use professional equipment to detect the photovoltaic modules.
1. Causes of hot spots and detection methods
of photovoltaic modules Hot spots of photovoltaic modules refer to the dark spots that are burned out when the module is exposed to sunlight because some cells are blocked and can not work, so that the temperature of the covered part is much higher than that of the uncovered part. The formation of hot spots in
PV modules is mainly composed of two internal factors, namely, the internal resistance and the dark current of the cell itself.
Hot spot durability test is a photovoltaic module test to determine the ability of solar modules to withstand hot spot heating effect. Photovoltaic cell modules are tested for a reasonable time and process to show that the photovoltaic cell can be used for a long time under the specified conditions.
Hot spot detection can be carried out by infrared thermal imager, which can use thermal imaging technology to display the temperature and its distribution of the measured object with a visible thermal map.
2. Causes of hidden cracks and detection methods
of photovoltaic modules Hidden cracks refer to small cracks in the cells, which will accelerate the power attenuation of the cells and affect the normal service life of the modules. At the same time, the cracks of the cells will expand under mechanical load, which may lead to open-circuit damage. Cracks may also cause a hot spot effect. Hidden cracks are caused by many reasons, such as uneven stress of components, or violent shaking in the process of transportation and reshipment, which may cause hidden cracks of cells.
Photovoltaic modules will be subject to EL imaging test before leaving the factory, and the instrument used is EL detector. Based on the principle of electroluminescence of crystalline silicon, the instrument uses a high-resolution CCD camera to capture near-infrared images of components, and obtains and determines the defects of components. The EL detector can detect whether the photovoltaic cell module has hidden cracks, fragments, false welding, broken grids and abnormal phenomena of single cells with different conversion efficiencies.
3. Classification of power attenuation and detection method
of photovoltaic modules Power attenuation of photovoltaic modules refers to the phenomenon that the output power of modules gradually decreases with the increase of illumination time. The power attenuation of PV modules can be roughly divided into three categories:
the first category is the power attenuation of modules caused by destructive factors;
the second category is the initial light-induced attenuation of modules;
the third category is the aging attenuation of modules.
Among them, the first category is the controllable attenuation in the installation process of photovoltaic modules, such as strengthening the quality control of unloading, reshipment and installation of photovoltaic modules, which can reduce the probability of cracking and fragmentation of module cells.
The second and third categories are the process problems to be solved in the production process of photovoltaic modules. PV module power attenuation test can be completed by PV module I-V characteristic curve tester.
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