- The connection method of the single battery of the module
There are mainly two ways to connect the single cells in series and parallel, and these two ways can also be used at the same time to form a mixed connection mode of series and parallel. If the performance of each single cell is consistent, the series connection of multiple single cells can increase the output voltage proportionally without changing the output current; the parallel connection method can not change the output voltage. The output current can be increased proportionally under the condition of lower voltage; while the series-parallel hybrid connection can not only increase the output voltage of the component, but also increase the output current of the component.
- Structure of crystalline silicon solar cell module
A typical package structure of a crystalline silicon solar cell module is shown in Figure 1.
Conventional solar cell modules have the following structural forms: glass shell structure, bottom box module, flat plate module, and fully glue-sealed module without cover plate. There are also newer double-sided tempered glass package components.
- Structure of thin film solar cell module
The packaging of thin film photovoltaic cells is somewhat different from that of crystalline silicon cells. The types of substrates and packaging methods are different. The relative position of the semiconductor material and the substrate will affect the structure of the module. For front wall type CdTe cells and most amorphous silicon cells using non-tempered glass substrate, the glass substrate can be used as the upper cover to protect the cell, any type of glass can be used on the back, and tempered safety glass can be used if required. For rear wall type CIS cells and some amorphous silicon cells using non-tempered substrates, a cover plate needs to be added to protect the cells.
In addition to the above two structures, if other types of substrates are used, another packaging method is used. This packaging method has three layers and is suitable for both front-wall and rear-wall thin-film photovoltaic cells, as shown in Figure 2. .
- Packaging materials for solar cell modules.
The length of the working life of the component has a great relationship with the packaging material and packaging process. The packaging material is easy to be ignored in the component, but it is a component that must not be underestimated in practice. click here to open to learn more about this aspect of solar cells.
(1) Upper cover plate The upper cover plate covers the front of the solar cell module and constitutes the outermost layer of the module. It must have high light transmittance and firmness to protect the battery for a long time. The materials used for the upper cover are: tempered glass, polyacrylic resin, chlorinated ethylene propylene, transparent polyester, polycarbonate, etc. At present, low iron tempered glass is the most common top cover material.
(2) Adhesives mainly include room temperature curing silicone rubber, chlorinated ethylene propylene, polyvinyl butyral, transparent hydrogen peroxide, polyvinyl acetate, etc. The general requirements are: ① high light transmittance in the visible light range; ② flexible; ③ good electrical insulation performance; ④ suitable for automated component packaging.
(3) The bottom plate is generally tempered glass, aluminum alloy, plexiglass, TPT, etc. At present, TPT composite film is widely used, and its requirements are: ① good weather resistance; ② no change in lamination temperature; ③ strong bond with the bonding material.
(4) Frame The flat panel component must have a frame to protect the component and the connection between the component and the square matrix. The frame is made of adhesive to seal the edge of the component, and the main materials are stainless steel, aluminum alloy, rubber, reinforced plastic, etc.
- Basic characteristics of solar cell modules
5.1 The volt-ampere characteristic curve of the module
The volt-ampere characteristic curve of the component is shown in Figure 3. The output power of a solar cell module is equal to the output voltage multiplied by the operating current, and most of the I-V curves are measured under Standard Test Conditions (STC). This I-V curve includes three important points: the maximum power point (Vmp, Imp), the open circuit voltage point (VOC) and the short circuit current point (ISC).
5.2 Influence of irradiance and temperature on module performance
Figure 4 shows the effect of irradiance on module performance. As can be seen from Figure 4, the output current of the module is proportional to the irradiance of sunlight. The stronger the sunlight, the higher the output power of the module. As the irradiance decreases, the shape of the volt-ampere characteristic curve is basically unchanged, but the short-circuit current gradually decreases. The open circuit voltage does not change much with irradiance.
Figure 5 shows the effect of temperature on component performance. When the temperature of the component is 25°C higher than the standard operating temperature, the efficiency of the component decreases, mainly manifested in the drop of the open circuit voltage. As the temperature increases, the shape of the volt-ampere characteristic curve is basically unchanged, but the whole is shifted to the left, indicating that the open circuit voltage decreases with the increase of temperature.
5.3 Effects of shading on component performance
The impact on the performance of the entire module when one cell in the module is shaded. If one cell in the module is completely shaded, the power loss of the entire module may be as high as 75%. Of course there are some components that are less affected by shading than this example.
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