An interesting perspective on PV modules reduces cost.

?Aluminum is the most abundant metal on the earth, aluminum alloy is based on aluminum to add a certain amount of other alloying elements, while having many excellent properties, widely used in industry and life. Aluminum alloy frame has always been one of the important auxiliary materials of photovoltaic modules, with the development of the photovoltaic industry.

At this stage, under the two development goals of "cost reduction" and "efficiency improvement" in the photovoltaic industry, component manufacturers have adopted a variety of component cost reduction and efficiency solutions such as reducing glass thickness, reducing silicon wafer thickness, and increasing component size. This puts forward higher requirements for the strength of the aluminum alloy frame. At the same time, the rise in aluminum prices has also allowed component manufacturers to consider a variety of border alternatives, and even consider canceling the border.

This article discusses the characteristics of frameless double glass assembly, steel frame, rubber frame, and composite frame, and compares them with aluminum frame. As a reference, the use of frame materials for building doors and Windows are compared, and the advantages of aluminum alloy structural materials are discussed. Finally, the input and recovery of aluminum alloy frames are discussed. The results show that aluminum alloy, due to its characteristics, stands out as a structural material in the development of many materials, has an absolute advantage, and the effect of asset preservation and appreciation is obvious. The use of aluminum alloy frames for photovoltaic modules is the only correct choice for the development of the photovoltaic industry.

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01. Introduction

As the second largest structural material, aluminum alloy has excellent new properties: high strength, strong fastness, good electrical conductivity, corrosion resistance and oxidation resistance, strong tensile resistance, convenient transportation and installation, easy recycling, and other materials that can not be matched. Since the birth of the photovoltaic module, it has been used as a border material and has been accompanied by its side, without any other material replacement, bearing the wind load and snow load of the photovoltaic module, providing a full range of protection for the photovoltaic module, and facilitating the installation of the module, which is enough to show that the aluminum alloy frame is irreplaceable in the photovoltaic module.

02. Aluminum alloy material characteristics

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

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

2) Easy to strengthen, pure aluminum strength is not high, but through alloying and heat treatment is easy to strengthen, the manufacture of high-strength aluminum alloy, strength can be comparable to alloy steel, so, elastic rate, rigidity, metal fatigue value is high, not easy to deformation, can be a good protection of solar panels;

3) Good conduction, aluminum's electrical and thermal conductivity is second only to silver, gold, and copper. If calculated according to the conductive capacity of equal-mass metals, aluminum is almost twice that of copper. Therefore, it is conducive to component installation grounding;

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

5) Easy surface treatment, aluminum can be anodized coloring treatment, high hardness after treatment, wear resistance and corrosion resistance, and electrical insulation good, chemical pretreatment can also be electroplating, electrophoresis, spraying, and other further improve the decorative and protective aluminum;

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

7) Convenient transportation and installation, even if the surface is scratched, it will not produce oxidation and does not affect the performance;

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

9) Beautiful appearance: aluminum alloy surface after anodic electrochemical treatment, can appear silver, black, etc., in line with aesthetic requirements;

10) Easy to recycle, the melting temperature of aluminum is low, about 660° C, the waste is easy to recycle, the recovery rate is very high, and the recovery energy consumption is only 3% of the original aluminum.

03. Border alternative solution

Under the two development goals of "cost reduction" and "efficiency improvement" in the photovoltaic industry, most of the module manufacturers use a variety of component cost reduction and efficiency solutions such as reducing glass thickness, reducing silicon wafer thickness, and increasing component size, which ultimately put forward higher requirements for the strength of the frame structure. At the same time, photovoltaic module manufacturers have been looking for alternative solutions, including frameless double-glass components such as the elimination of the border solution, but also considered the use of other materials photovoltaic borders, including steel structure, rubber, and composite materials. Next, various solutions are discussed and analyzed below, so that readers can have a clearer understanding of the photovoltaic module border.

?Frameless double glass assembly

Because the frameless double glass component adopts double glass, the mechanical properties of the component are improved, and the frameless double glass pressing block is used, the aluminum alloy frame can be eliminated theoretically. However, there is always a difference 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 component, a large number of customer complaints were received, mainly because the frameless double glass component appeared to be deformation, causing hidden cracks in the battery and glass burst. The main sources of stress causing component deformation are (1) uneven lamination stress of the junction zone; (2) uneven mechanical stress; and (3) Uneven thermal stress. The problems of frameless double glass components lead to heavy losses for component manufacturers. The aluminum alloy frame can make the edge of the photovoltaic module evenly stressed, and will not cause stress hazards due to installation fixtures, internal stresses, and other reasons. After experiencing frameless double glass modules, photovoltaic manufacturers are more aware of the importance of aluminum alloy frames for photovoltaic modules.

Steel frame

Because steel has the advantages of high strength and cheap price compared with aluminum alloy profiles, photovoltaic manufacturers have tried to introduce steel frames instead of aluminum alloy frames to achieve cost reduction. 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) Poor appearance of steel structure border: at present, there are some alloy steel structure border products on the market, but due to process limitations, resulting in a large difference in appearance with the existing aluminum alloy border, it is difficult for customers to accept the switch from an excellent aesthetic aluminum alloy border to a poor appearance of steel structure border, the product appearance is compared as follows:

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2) High density and heavyweight: due to the high density of the steel structure border, the conventional 72-version border with the same section thickness will more than double the weight of the steel structure border. In the context of the development of large-scale photovoltaic modules, the weight of the components has a great impact on the installation and use of the components, which has become one of the bottlenecks limiting the further development of large-scale components, so the steel structure components do not meet the future development trend of photovoltaic modules.

3) Poor corrosion resistance: the aluminum alloy frame has excellent corrosion resistance after years of experiments and power station end verification. However, the steel frame is easy to be oxidized and rusted due to the material characteristics, which affects the beauty and product life;

4) Low recycling value: After 20-30 years of outdoor operation of steel structure frame, it is easy to rust, difficult to recycle, low recycling ratio, and does not have economic and environmental protection;

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

Rubber frame

In many products ready to replace the aluminum alloy frame, an aluminum alloy with rubber rubber buckle frame scheme came into being, although the product has not been officially unveiled, through the manufacturer's introduction can be understood that the frame scheme uses a similar frameless double glass block structure design, and its main application in frameless double glass components, the product compared with the aluminum alloy frame, the disadvantages are as follows:

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

2) The rubber-plastic frame is easily weathered and generally cannot reach the service life of solar panels (25 years);

3) Poor environmental friendliness, the whole life cycle of rubber products has great pollution to the environment, which is not in line with China's green sustainable development path.

?Composite frame

?Composite border in many border materials have a long history, as early as 2012, manufacturers were developing related products, but due to the characteristics of its polymer materials, they have not been accepted by the mainstream component manufacturers, their application scenario is 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.

04. Frame materials of doors and Windows

"A stone from another mountain can attack jade." We can learn from the development of frame materials in the building door and window industry with a longer history, and refer to the development of photovoltaic module borders. The window frame has experienced the era of wood Windows, steel structure Windows, and plastic steel Windows, and the final technological development determines the modern doors and Windows series based on aluminum alloy doors and Windows.

The analysis of the development process of doors and Windows shows that the material characteristics of different materials of doors and Windows frames determine that aluminum alloy doors and Windows are the inevitable choices for the doors and Windows market.

1) Wood window: Wood window is the earliest form material used by human beings, with natural, harmonious, warm, solid characteristics, need to use high-quality wood, as well as excellent technology manufacturing, so the price is higher, more used in villas and other high-end space treatment; In addition, poor quality wood Windows are easy to deformation, affecting the use of.

2) Steel structure window: the product of the industrial revolution, China's old public housing before the 1980s used this kind of window, easy to rust, cheap, not sealed, has been eliminated.

3) Plastic steel window: As the name suggests, the window is composed of plastic and steel, and 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; However, the plastic steel material is easy to age and discoloration, cracks may appear after exposure to the sun, the strength of the profile is low, and the large-size profile is easy to deform, which is suitable for the structure of small doors and Windows.

4) Aluminum Windows: Aluminum Windows are the most widely used window and door materials, and their advantages are very obvious: lightweight, strong, not easy to deform, metal texture, easy to process, can use spraying or electrophoresis surface treatment, can match any color with the architectural appearance and the interior space of the room, is the most choice of building doors and Windows materials.

05. Economic analysis of aluminum alloy frame

At present, the fundamental reason for the emergence of various photovoltaic border solutions in the market is the cost-reduction demand for photovoltaic modules, due to the substantial growth of the current aluminum price, increasing the cost of component borders. On the other hand, from the perspective of material recycling and recycling, compared with other materials, aluminum alloy frame has a high reuse value, and the recycling process is simple, in line with the concept of green recycling development. Here's a simple calculation:

* At present, the size of the 182 and 210 versions is the same, and this calculation is estimated according to the unified size

After 25 years of use, the PV module frame can be fully recycled. Although the price of a single set of frames reaches 100 yuan per set, the recycling value of a single set of aluminum frames is estimated at the current aluminum price to be as high as 70 yuan. At the same time, due to the requirements of the national electrolytic aluminum production capacity "ceiling" restriction and dual control of energy consumption, as well as changes in the domestic and foreign economic environment, it is expected that after 25 years, aluminum prices will rise. Temporarily calculated by doubling the price of aluminum, the recovery value of the aluminum frame will reach 140 yuan per set, which is much higher than the investment of buying a frame now. The aluminum frame of the 210 component is similar. The value of aluminum alloy frame preservation and appreciation highlights, which is not possessed by other materials such as steel structure frame and rubber frame.

06. Conclusion

In recent years, with the development and application of China's photovoltaic industry and building doors and Windows industry, aluminum alloy stands out in many structural materials, showing the absolute advantage of aluminum alloy, which is the choice of photovoltaic industry development needs, but also experienced a lot of practice of the best structural material program, aluminum alloy frame is still the best partner of photovoltaic modules.

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