The design lifetime of photovoltaic modules is 25 years. Therefore, the working life requirements are also set for the supporting materials that make up the modules. As a key material in photovoltaic modules, backplanes not only protect and support photovoltaic modules, but also must have reliable insulation, water vapor barrier properties, and weather resistance, and their service life is generally required to be guaranteed for 25 years. Because many understanding concepts of photovoltaic backplanes still remain in the industry four or five years ago, this paper summarizes the five common misunderstandings of photovoltaic backplanes, hoping to eliminate misunderstandings for the industry and provide reference for backplane selection.
One of the misunderstandings of backplanes: Can all fluorine films provide 25 years of protection?
Truth: The quality of fluorine materials (fluorofilm and fluororesin) is affected by various factors such as fluorine raw materials, formulation, process, and quality level. The use of factory brands and outdoor use for more than 25 years is relatively reliable; Providing 25 years of protection is obviously a false proposition.
The second part of the backplane misunderstanding: Can the inner fluorine film 1um be protected?
Truth: The inner layer of the back sheet not only plays the role of adhesive, but also has UV protection. The protection of the fluorine material to PET depends on the fluorine material in certain CPVS concentration pigment conditions, and the ultraviolet rays reflect and absorb in the interior through a certain thickness. Block UV rays from entering the PET interface. Therefore, the coating is too thin to completely block the aging of the ultraviolet rays, resulting in the yellowing and cracking of the PET in the intermediate layer. Generally, the thickness of the inner layer of the fluorine material must reach about 10 μm to achieve protection.
The third part of the backplane misunderstanding: Is the water permeability of the coated backplane necessarily large?
Truth: The water permeability of the backsheet is directly related to the PET material of the intermediate substrate and the thickness of the backsheet. There is no correlation with the coating or the composite. The PET substrate is the actual barrier layer. Nylon backsheet has a certain degree of water absorption and its water permeability is higher than the industry standard. The root cause of snails in the industry is the EVA.
Backplane misunderstanding No. 4: Will the coated backsheet be resistant to falling sand?
Truth: The abrasion resistance is directly related to the thickness of the outer material, and it is not much related to coating or compounding. In addition, the material hardness and flexibility also have an effect on the wear resistance. The ordinary fluorine film is a non-cross-linked two-dimensional structure, lacking strong chemical bonds in the longitudinal direction (Z direction), but weaker van der Waals forces and hydrogen bonds, while the coated fluorine layer is a cross-linked three-dimensional structure. The network structure has strong chemical bonds in the three directions of X, Y, and Z. This dense network structure has no obvious defects and is difficult to be destroyed. In contrast, the coated backplane has a comparative advantage. High abrasion resistance.
Wrong understanding of the backplane 5: coating type backplane is easy to peel it?
Truth: The adhesion fastness of the fluorine film or coating and the substrate depends on the formulation and processing technology. The laboratory generally uses the boiling water test, the HAST (PCT) test, and the thermal shock test for rapid inspection. The coating is chemically covalently bonded to the substrate, resulting in a high degree of integration and reduced attenuation. It is stronger than the composite backsheet made of adhesive.
Misunderstanding of the backplane 6: Non-fluorine and single-sided fluorine backplane costs lower than double-sided fluorine backplane?
Truth: Considering material cost alone, double-sided fluorine-containing backsheets may be high. However, from the perspective of the long-term benefits of photovoltaic systems and the cost of electricity, the situation is completely different. Aging during the use of non-fluorine and single-sided fluorine-containing backsheets, resulting in too much power failure of the module, reducing system revenue, technical progress and production efficiency can reduce the cost of manufacturing double-sided fluorine-containing backplanes, making the price and non-fluorine The backplane and single-sided fluoroplastic backplane are flat.
Finally, the article analyzes the common failure modes and aging mechanisms of photovoltaic backsheets, and proposes the concept of “non-fluorine backplatesâ€, pointing out that any low-cost non-fluorine material at the expense of quality is unacceptable to the entire industry. It calls on the entire industry to attach importance to the quality of materials and jointly promote the healthy development of the photovoltaic industry.
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