Other attempts are in vain, aluminum alloy frame is the only choice for photovoltaic modules

Summary

Aluminum is the most abundant metal on earth. Aluminum alloy is based on aluminum and adds a certain amount of other alloying elements. At the same time, it has many excellent properties and is widely used in industry and life. Aluminum alloy frame has always been one of the important auxiliary materials of photovoltaic modules, and it has developed with the photovoltaic industry. At this stage, under the two major development goals of "cost reduction" and "efficiency enhancement" in the photovoltaic industry, module manufacturers have adopted a variety of cost reduction and efficiency improvement solutions for modules such as reducing glass thickness, reducing silicon wafer thickness, and increasing module size. . This puts forward higher requirements on the strength of the aluminum alloy frame. At the same time, the rise in aluminum prices has also made component manufacturers consider various alternatives to the frame, and even consider canceling the frame. This paper discusses the characteristics of frameless double-glass modules, steel frame frames, rubber frames, and composite frames, and compares them with aluminum alloy frames. As a reference, the use of frame materials for building doors and windows is compared, and the advantages of aluminum alloy structural materials are discussed. Finally, the investment and recycling of aluminum alloy frame are discussed. The results show that aluminum alloy stands out as a structural material in the development of many materials due to its own characteristics, and has an absolute advantage, and the effect of asset value preservation and appreciation is obvious. The use of aluminum alloy frame for photovoltaic modules is the only correct choice for the development of the photovoltaic industry.

Introduction

As the second largest structural material, aluminum alloy has excellent new properties: high strength, strong firmness, good electrical conductivity, corrosion resistance and oxidation resistance, strong tensile strength, convenient transportation and installation, and easy recycling and other materials Incomparable advantages. Since the birth of photovoltaic modules, it has been used as a frame material, and has been accompanied by its side without any other materials. It is responsible for the wind load and snow load resistance of photovoltaic modules, comprehensive protection of photovoltaic modules, and convenient module installation. , which is enough to illustrate the irreplaceability of aluminum alloy frame in photovoltaic modules.

Aluminum alloy material features:

Aluminum alloy frame has always been one of the indispensable auxiliary materials for photovoltaic modules, mainly due to the advantages of aluminum alloy material itself, mainly including:

1) Low density, the density of aluminum is about 2.7g/cm3, which is only the second light metal higher than magnesium in metal structure materials, only 1/3 of iron or copper;

2) It is easy to strengthen, the strength of pure aluminum is not high, but it is easy to strengthen through alloying and heat treatment, making high-strength aluminum alloy, the strength is comparable to that of alloy steel, so the elastic modulus, rigidity and metal fatigue value are high, Not easy to deform, can protect the solar panel well;

3) Good electrical conductivity, the electrical conductivity and thermal conductivity of aluminum are second only to silver, gold and copper. If calculated according to the conductivity of the same quality metal, aluminum is almost twice that of copper. So it is helpful for component installation and grounding;

4) High plasticity, good ductility of aluminum and its alloys, can be made into various shapes, plates, foils, tubes and wires by pressure processing methods such as extrusion, rolling or drawing;

5) Easy surface treatment, aluminum can be treated by anodizing and coloring, with high hardness after treatment, good wear resistance, corrosion resistance and electrical insulation, and chemical pretreatment can also be used for electroplating, electrophoresis, spraying, etc. to further improve the decoration of aluminum Sexual and protective;

6) Corrosion resistance, strong oxidation resistance, aluminum and oxygen have a very high affinity, protective oxides will be formed on the surface of aluminum under natural conditions, and it has stronger corrosion resistance than steel. Because of this advantage, aluminum alloy profiles are widely used in various fields of construction and industry;

7) It is easy to transport and install, and the surface will not be oxidized even if it is scratched, which will not affect the performance;

8) Long service life, the life of aluminum alloy is generally more than 30-50 years. The life of the battery board is 25-30 years, so it can fully meet the requirements;

9) Beautiful appearance: the aluminum alloy surface can be silver-white, black, etc. after the anodic electrochemical treatment, which meets the aesthetic requirements;

10) Easy to recycle, the melting temperature of aluminum is low, about 660°С, the waste is easy to regenerate, the recycling rate is extremely high, and the energy consumption for recycling is only 3% of the primary aluminum.

Alternative border solutions:

Under the two major development goals of "cost reduction" and "efficiency enhancement" in the photovoltaic industry, most module manufacturers use various modules such as reducing glass thickness, reducing silicon wafer thickness, and increasing module size to reduce costs and improve efficiency. The above cost reduction scheme finally puts forward higher requirements on the structural strength of the frame. At the same time, photovoltaic module manufacturers have been looking for alternative solutions, including frameless double-glass modules, which eliminate the frame, and have also considered using other materials for photovoltaic frames, including steel structures, rubber, composite materials, etc. Next, various solutions are discussed and analyzed, so that readers can have a clearer understanding of the frame of photovoltaic modules.

Frameless Double Glass Module:

Because the frameless double-glass module adopts double-layer glass, the mechanical properties of the module are improved, and at the same time, the frameless double-glass pressing block can be used to theoretically save the aluminum alloy frame. However, there are always differences between the laboratory test results and the actual operation of the power station. Within a few years of the installation of the frameless double-glass modules, a large number of customer complaints have been received. The main sources of stress that cause the deformation of the components are: (1) uneven lamination stress of the busbar; (2) uneven mechanical stress; (3) uneven thermal stress. The problems of frameless double-glass modules have resulted in heavy losses for module manufacturers. The aluminum alloy frame can make the edge of the photovoltaic module evenly stressed, and will not cause hidden stress due to installation fixtures, internal stress and other reasons. After experiencing frameless double-glass modules, photovoltaic manufacturers are more aware of the importance of aluminum alloy frames to photovoltaic modules.

Steel Frame:

Because steel has the advantages of high strength and low price compared with aluminum alloy profiles, photovoltaic manufacturers have tried to introduce steel structure frames instead of aluminum alloy frames to reduce costs. However, due to the material characteristics of the steel structure frame, its application in photovoltaic modules is limited. The main reasons are as follows:

1) The aesthetics of the steel structure frame is poor: At present, there are some alloy steel structure frame products on the market, but due to process limitations, their appearance is quite different from the existing aluminum alloy frame, and it is difficult for customers to accept the excellent aesthetics. The aluminum alloy frame is switched to the lesser looking steel frame.

2) High density and heavy weight: Due to the high density of the steel structure frame, the weight of the conventional 72-type frame with the same section thickness should be more than doubled. In the context of the development of large-scale photovoltaic modules, the weight of modules has had a great impact on the installation and use of modules, and has become one of the bottlenecks restricting the further development of large-scale modules. Therefore, steel structure modules do not meet the future development trend of photovoltaic modules.

3) Poor corrosion resistance: The aluminum alloy frame has been proven to have excellent corrosion resistance after years of experiments and power station terminals. However, the steel frame frame is easily oxidized and rusted due to material properties, which affects the appearance and product life;

4) Low recycling value: After 20-30 years of outdoor operation, the steel frame frame is very easy to rust, difficult to recycle, low recycling ratio, not economical and environmentally friendly;

5) Poor processability of steel frame: The processing technology of steel frame is mainly bending process, which easily leads to low precision of steel frame products, limited frame shape, and difficult processing.

Rubber border:

Among the many products that are ready to replace the aluminum alloy frame, an aluminum alloy with rubber rubber snap frame solution came into being. Similar to the frameless double-glass pressure block structure design, and it is mainly used in frameless double-glass modules, compared with the aluminum alloy frame, this product has the following disadvantages:

1) According to reports, the rubber snap frame instead of the conventional aluminum alloy frame has the advantage of self-cleaning by rain, that is, its products are mainly used in frameless double-glass modules, but as mentioned above, the current frameless double-glass product solution has gradually Abandoned by component manufacturers, it is unknown how to solve the above problems with the rubber frame;

2) The frame made of rubber and plastic is easily weathered and generally does not reach the service life of the solar panel (25 years);

3) The environmental friendliness is poor, and the whole life cycle of rubber products causes great pollution to the environment, which is not in line with my country's green and sustainable development path.

Composite border

Composite material frame is a kind of frame material with a relatively long history. Some manufacturers have developed related products as early as 2012. However, due to the limitations of its polymer material characteristics, it has not been accepted by mainstream component manufacturers. Its application scenarios Limited, there is still a long way to go.

Although the aluminum alloy frame has never been replaced by other materials, the process of seeking alternative materials has never stopped, and various attempts have not been accepted by the market.

Frame materials for doors and windows

“The stone of other mountains can attack jade. ” We can learn from the development of frame materials in the building door and window industry with a longer history to be a reference for the development of photovoltaic module frames. The door and window frame has experienced the era of wooden windows, steel structure windows, and plastic-steel windows, and the final technological development has determined the modern door and window series mainly based on aluminum alloy doors and windows.

Analyzing the development process of doors and windows, we can see that the material characteristics of door and window frames of different materials determine that aluminum alloy doors and windows are the inevitable choice in the door and window market.

1) Wooden window: Wooden window is the earliest window material used by human beings. It has the characteristics of natural, harmonious, warm and solid. It needs to be made of high-quality wood and excellent craftsmanship, so the price is higher, and it is mostly used in high-end villas. Space processing; in addition, inferior wooden windows are easy to deform and affect the use.

2) Steel structure window: a product after the Industrial Revolution, this type of window was often used in the husband's house before the 1980s, which is easy to rust, cheap and unsealed, and has now been basically eliminated.

3) Plastic-steel window: As the name suggests, the window is composed of plastic and steel as the window profile. The plastic (PVC) profile is lined with steel, which not only achieves the thermal insulation effect, but also increases the strength and the cost is low; but the plastic-steel material is easy to age and change color. , cracks may appear after exposure to the sun, the strength of the profile is low, and the large-size profile is easily deformed, which is suitable for the structure of doors and windows with a small volume.

4) Aluminum alloy windows: Among the types of doors and windows, aluminum alloy windows are the most widely used door and window materials at present, and their advantages are very obvious: light weight, strong, not easy to deform, metal texture, easy to process, and can be sprayed or electrophoresis. It can be used in any color to match the shape of the building and the interior space of the living room. It is the most selected material for building doors and windows.

Economic analysis of aluminum alloy frame

The fundamental reason for various photovoltaic frame solutions in the current market is the demand for cost reduction of photovoltaic modules. Due to the substantial increase in the current aluminum price, the cost of the module frame has increased. But on the other hand, from the perspective of material recycling, compared with other materials, the aluminum alloy frame has a very high reuse value, and the recycling process is simple, which is in line with the concept of green recycling development. Here is a simple calculation:

*The size of the 182 and 210 versions is currently the same, and this estimate is based on the unified size

After 25 years of PV module frame, the frame can be fully recycled. Although the price of a single frame of the 182 72 version reaches 100 yuan per set, the recycling value of a single set of aluminum frames is as high as 70 yuan based on the current aluminum price. At the same time, due to the requirements of the national electrolytic aluminum production capacity "ceiling" limit and energy consumption dual control, as well as changes in the domestic and foreign economic environment, it is expected that after 25 years, the rise of aluminum prices is a high probability event. If the aluminum price is doubled for the time being, the recycling value of the aluminum frame will reach 140 yuan per set, which is much higher than the investment in buying the frame now. The situation with the aluminum alloy frame of the 210 component is similar. The preservation and appreciation value of aluminum alloy frame is outstanding, which is not available in other materials such as steel frame and rubber frame.

Conclusion

Combining the development and application of my country's photovoltaic industry and building door and window industry in recent years, aluminum alloy stands out among many structural materials, showing the absolute advantage of aluminum alloy. This is the choice for the development needs of the photovoltaic industry, and it is also the most experienced Excellent structural material solution, aluminum alloy frame is still the best partner for photovoltaic modules.