Crystalline silicon photovoltaic modules are an important part of the photovoltaic power generation system. The quality of the modules directly affects the power generation performance of the power station. The main components are tempered glass, EVA, cells, ribbons, backplanes, frames, junction boxes, sealants, etc. Material properties and common appearance defects are as follows:
Learn to understand the composition and structure of photovoltaic modules
1. Cells
Crystalline silicon cells are mainly made of semiconductor silicon. After the light is irradiated on the semiconductor, the P-N junction of the cell receives light (the P-type junction is silicon doped with trivalent boron, the N-type junction is silicon doped with pentavalent phosphorus, the junction of the two is the P-N junction, and silicon is tetravalent Semiconductors) create a potential difference and thus a current flow. At present, the thickness of the cell is 200±20μm, and it is easy to be damaged by force during the production process. The common problems are shown in the figure below:
2. Ribbon
The soldering strips used in multibusbar solar photovoltaic modules are tin-coated copper strips, which are divided into interconnection strips and bus strips. The interconnection strips are used to connect battery sheets, and the bus strips are used to connect battery strings, which play the role of conducting electricity and collecting electricity; common defects at the welding strips include welding There are material problems and welding problems, as shown in the figure below:
3. Glass
The photovoltaic module adopts low-iron toughened suede glass (or coating), which has the protection of battery cells, waterproof, high light transmittance, reliable wind pressure resistance, and hail impact resistance. Common problems can be divided into glass material reasons and external force reasons, as shown in the following figure:
4. EVA
EVA is used to encapsulate spliced battery strings, which is a copolymer of ethylene and vinyl acetate. EVA is non-viscosity at room temperature and easy to operate. After certain process conditions, hot pressing will undergo fusion bonding and cross-linking curing, and become completely transparent. The cured EVA can withstand atmospheric changes and is elastic. In addition, after it is bonded to glass, it can increase the light transmittance of the glass, play the role of anti-reflection, and have a gain effect on the output of solar cell components. Common problems can be divided into material reasons and process reasons, as shown in the following figure:
5. Backplane
At present, the commonly used backplane structures include TPT, TPE, TPF, KPK, KPF, etc., which are used as packaging materials on the back of the module. It reflects sunlight, so the efficiency of the module is slightly improved, and because of its high infrared emissivity, it can also reduce the operating temperature of the module, which is also conducive to improving the efficiency of the module. It also needs to have properties such as aging resistance, corrosion resistance, water vapor penetration resistance, and insulation. Common problems can be divided into backplane material, process, and external force reasons, as shown in the following figure:
6. Border
The frame used by the PERC photovoltaic module is aluminum profile, and the surface of the aluminum profile is anodized, which has the properties of insulation and corrosion resistance, protects the component, increases the load-bearing capacity, and is convenient for transportation and installation. Common problems can be divided into material reasons and external force reasons, as shown in the figure below:
7. Junction box
The junction box used by photovoltaic modules is composed of a box cover, a box body, a pole tube, a connecting wire, and a connector; the sealing method usually includes potting glue sealing and sealing ring sealing, and its main functions are as follows:
(1) Connect the lead wire of the component to derive the current generated by the component.
(2) Protection: heat dissipation, prevent hot spot effect, seal anti-aging.
The common problems of junction boxes are mainly due to material and process reasons, as shown in the following figure:
8. Sealant
Photovoltaic modules are currently mainly sealed with silica gel or adhesive tape, which must have the characteristics of waterproof, UV resistance, and weather resistance, as shown in the figure below:
(1) Connect the lead wire of the component to derive the current generated by the component.
(2) Protection: heat dissipation, prevent hot spot effect, seal anti-aging.