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The loss of hundreds of millions of yuan to photovoltaic investors by 3A backplanes is like a shocking thunder, which "exploded" the huge risks behind the diversification of photovoltaic backplane technology routes.
Faced with the pressure to reduce the cost of photovoltaic power plants, packaging materials including backsheets are also continuing to explore new technical directions and space for cost reduction. However, behind the continuous innovation of new technologies, as a "copper wall and iron wall" that protects the reliability of photovoltaic modules, The risks brought by the diversification of backplane structures are also testing photovoltaic power plants under outdoor operating conditions. In the development process of continuous cost reduction and localization in the field of backplanes, several technical routes have been differentiated, and coated backplanes are one of them. Fluorine membrane backsheet materials have been certified by the industry as the most excellent and reliable backsheet selection, but under the pressure of cost and process, coated backsheets have begun to appear in the market.
As the name suggests, the coated back sheet is made of paint, and its fluorine content is significantly reduced. After experiencing the lessons learned from the fluorine-free 3A backsheet, the performance of the coated backsheet with reduced fluorine content on the application side has not been verified.
It is understood that the outer coating of the coated backplane generally uses polyurethane formed by chemical cross-linking of isocyanate and FEVE resin, and this material has a low fluorine content. In terms of material characteristics, it is used as a protective layer for components. , Compared with fluorine film, there is still a gap in weather resistance and chemical resistance.
In a laboratory test conducted by a third-party organization, the commercially available coated transparent backsheet was severely whitened and the outer coating peeled off after the UV damp heat aging test, resulting in a decrease in light transmittance. In fact, in some power station applications, the performance of the coated backplane is not satisfactory. Because the coating is far less dense than the fluorine film and is prone to pinholes, the coated backplane often exhibits mildew and burn through. , Scratches, delamination and cracking.
Related professionals analyzed that the reasons for the failure of the coated backplane include the following points. The paint is directly coated on the PET substrate, and there are pinholes on the surface after the solvent evaporates, and a dense film cannot be formed. Therefore, the interface between the coating and the PET substrate is easily corroded by water vapor, and it is prone to aging, peeling and mold in the outdoor environment; secondly, the coating has poor toughness, and the outer layer is easily scratched by flying sand. In addition, the transparent FEVE coating has poor compatibility with additives, and it is easy to precipitate after aging, causing the coating to whiten and peel off.
A senior professor in the new energy major of a university in Qinghai told the author that the power generation of photovoltaic power plants is determined by the comprehensive outdoor performance of the various materials of the modules. Although the cells are the main body of power generation, the performance of other materials outdoors is It directly or indirectly affects the safety and power generation performance of photovoltaic power plants.
"Take the backplane as an example. Although it looks like a white plastic protective film, in fact, the components of the component backplane are very different. In Qinghai, many cases of failure of the coated backplane have been found, mainly in the backplane. The board is not abrasion-resistant and easy to scratch."
The professor explained that after the surface coating of the coated backplane is worn, the PET middle layer will be directly exposed to the environment, causing obvious cracking of the PET, which will lead to the power degradation of the module battery and the risk of insulation leakage. . Especially in the northwest region, a reliable backplane can be used to better protect the long-term operation of the components. It is understood that up to now, head component companies are still cautious about coated backsheets. A related person from a head module company told the author that the performance of coated backsheets in terms of aging resistance is general, and it should be used with caution in photovoltaic power plants in humid and hot, strong ultraviolet, high and low temperature areas.
Facing the great task of global climate transformation, the demand for new energy projects at home and abroad is showing an explosive trend, and the photovoltaic industry has ushered in a new development cycle. But at the same time, limited by land and other conditions, the installation environment of photovoltaic power plants is gradually diversifying, and photovoltaic power plants "up to the mountain and down to the sea" are facing an increasingly complex operating environment.
But at the same time, the photovoltaic industry is still facing continuous pressure to reduce costs. In this context, new technologies are blooming and emerging in endlessly. But as far as the backplane is concerned, high reliability can escort the 25-year life cycle of photovoltaic modules. It will inevitably pay a heavy price for this to be done. These cases of backplane failures in the outdoor are a lesson for the past.
