Double-sided, large-size, differentiated .One article to understand the development direction of photovoltaic glass technology

With the advent of the reduction of photovoltaic subsidies and the era of affordable Internet access, under the tremendous pressure of continuous cost reduction, in recent years, the technological development of photovoltaic cells and modules has been changing rapidly in various forms. However, the development direction of module technology related to photovoltaic glass is mainly: double-sided double-glass photovoltaic modules, large-size photovoltaic modules and differentiated photovoltaic modules.

Technical direction of components related to photovoltaic glass

1.1 Double-sided photovoltaic modules

The double-sided module refers to a photovoltaic module using double-sided batteries, which can significantly increase the power generation capacity of the system and reduce the power generation cost of the system. In recent years, with the maturity of the manufacturing process and the corresponding cost reduction, since 2018, many domestic large-scale module companies have entered the stage of mass production of double-sided modules. In 2019, the actual output of double-sided modules exceeds 15GW, and the capacity of double-sided modules Reached over 25GW. Double-sided power generation technology has become an important starting point for photovoltaic companies, and is rapidly developing in the direction of Liaoyuan.

Double-sided components appeared in 2016. As of the end of 2018, the main packaging methods are 2.5mm+2.5mm double glass frameless and framed. At the end of 2018, due to the increase in the mass production capacity of 2.0mm semi-tempered photovoltaic glass and the significant reduction in cost, Longji and Artus took the lead in mass production of 2.0mm+2.0mm double-sided double glass framed components. In the case of meeting the strength and cost requirements, the weight of double-sided double-glass modules has been greatly reduced (taking 72 battery modules as an example, the weight of double-sided double-glass modules can be reduced by 5KG), which has gradually won high recognition in the market. Therefore, in 2019, photovoltaic module companies mainly adopt a 2.0mm+2.0mm double glass framed packaging method for double-sided modules.

In 2019, there are also some new packaging methods for double-sided components on the market, such as 1.6mm + 1.6mm double glass framed and 3.2mm + transparent backplane framed packaging methods. With the competition arising from the addition of transparent backplanes, the author believes that it is necessary to further reduce the glass thickness and increase the glass strength of double-sided double glass modules to enhance the competitive advantages of double-sided double glass modules.

1.2 Large-scale photovoltaic modules

The photovoltaic industry has gradually formed a consensus that by increasing the size of the battery or increasing the number of batteries to greatly increase the power generation of a single photovoltaic module, it can significantly reduce the system power generation cost (BOS cost) of the power station, which is easier and more effective than improving battery efficiency. Also more obvious.

Since 2018, Longji has been the first to launch M6 cells (length 166.75mm), which is about 13% larger than the mainstream M2 cells (length 156.75mm), which means that the power generation of modules with the same number of cells has increased. About 13%. However, Central held a new product launch in August 2019 and revolutionaryly launched the M12 cell (length 210mm), which is about 80% larger than the single-chip area of the mainstream M2 cell (length 156.75mm).

With the introduction of M12 solar cells and corresponding 500W and 600W components in the Central, the market has attracted great attention because it can significantly reduce the BOS cost of the power station. Facing the high power challenge of M12 battery modules, large domestic and foreign module manufacturers have planned to respond by increasing the number of individual module batteries. The competitive landscape of high-power large-size components has gradually emerged!

1.3 Differentiated photovoltaic modules

Due to the different installation environment and use requirements of photovoltaic modules, end customers will make some special requirements for photovoltaic modules, which will lead to different types of photovoltaic modules, such as: anti-glare photovoltaic modules for airports or near airports, for roofs Black colorless photovoltaic modules, moisture-proof photovoltaic modules for seaside or water surface, wind-sand-resistant photovoltaic modules for desert areas, and BIPV or RIPV photovoltaic modules of special sizes, etc.

At present, the market share of differentiated photovoltaic modules is still very small, but the author believes that as the cost of photovoltaic modules is further reduced and the application scenarios are more and more extensive, the demand for differentiated photovoltaic modules in the market will definitely increase. Differentiated or customized photovoltaic materials supporting it are needed, especially photovoltaic glass as the key auxiliary material of photovoltaic modules (the differentiated modules mentioned here are mainly related to the difference of photovoltaic glass, not including all the market Types of differentiated components).

Thinning direction of photovoltaic glass

2.1 Selection of glass thickness of double glass components

As of 2018, 2.5mm+2.5mm double glass framed packaging is mainly used for double-sided double-glass components on the market, and from 2019, 2.0mm+2.0mm double-sided double-glass components are mainly used Glass framed packaging methods, currently some 2.5mm glass is used as a double-sided double-glass module front and back panel manufacturers are also actively certifying 2.0mm glass double-sided double-glass components, plans to switch 2.5mm glass to 2.0mm glass as soon as possible .

The main reason for the reduction of the double-sided double-glass module glass from 2.5mm to 2.0mm is: the weight of 2.0mm glass is reduced by 20%, the cost of 2.0mm glass is reduced by about 4%, and the mechanical strength of 2.0mm glass can also meet the module The mechanical load requirements and supply capacity are also guaranteed.

At present, some companies have begun to produce 1.6mm photovoltaic glass, and some component companies have also begun to produce 1.6mm + 1.6mm double-sided double glass modules. With the improvement of 1.6mm photovoltaic glass toughening performance, cost reduction and supply capacity improvement, the author believes that 1.6mm+1.6mm double-sided double glass modules will be more applied to the roof and gradually replace the existing 3.2mm Single glass conventional components. Because in the case of basically the same weight and cost, roof customers will prefer to choose double glass double-sided components with longer warranty.

From the perspective of the selection of the back glass type of double-sided modules, in order to pursue a higher double-sided rate of photovoltaic modules, the current back glass of double-sided modules basically chooses ultra-white embossed photovoltaic glass instead of float method. Glass is because the transmittance of about 92% of 2.0mm ultra-white embossed photovoltaic glass is significantly higher than the transmittance of about 90% of 2.0mm float glass without coating on the back glass. However, in the future, there may be tight supply of embossed glass and the cost advantage of float glass, and the type of back glass of double-sided double-glass modules may be partially shifted to the use of float glass.

2.2 Selection of glass thickness of single glass components

Before 2014, more than 72 photovoltaic cells used in Europe and America used 4.0mm thick photovoltaic glass. After eliminating concerns about the strength of the glass, for the consideration of cost and weight, the photovoltaic modules basically use 3.2mm photovoltaic glass, and the 4.0mm photovoltaic glass gradually withdrew from the stage of history after 2014.

Around 2014, LG of South Korea learned that 2.8mm thick glass is the lower limit of the thickness that the glass industry can be fully tempered for a long time. After testing and certification, South Korea LG fully adopted 2.8mm photovoltaic glass as the cover of its photovoltaic modules Plate glass, until now, there are still a small number of component manufacturers in the world that use less than 3.2mm photovoltaic glass as a single glass photovoltaic module cover glass.

At the beginning of 2017, as AVIC Sanxin launched 2.5mm all-tempered glass for the first time in the world, its mechanical performance in all aspects was close to 3.2mm tempered glass, let us see that 2.5mm all-tempered glass replaced 3.2mm or 2.8mm photovoltaic glass Possibility as a single glass module cover. Subsequently, it attracted the attention of many well-known overseas component companies.

At the 2019 SPI exhibition in the United States, we have seen that well-known module companies Sunpower and Taiwan URE have exhibited single-glass modules of AVIC Sanxin 2.5mm fully tempered photovoltaic glass, of which Sunpower has obtained its certification at the end of 2017. After this exhibition, South Korean well-known module companies have shown great interest in replacing 2.5mm all-tempered photovoltaic glass with 3.2mm photovoltaic glass on single-glass modules, and plan to conduct testing and certification of 2.5mm all-tempered photovoltaic glass.

2.3 Impact of thinning of photovoltaic glass on production capacity

As can be seen from the table above, when the nominal thickness of glass is reduced from 3.2mm to 2.5mm, 2.0mm and 1.6mm, the current glass production capacity of the same furnace can be increased by 17%, 41% and 60%, respectively. However, as the yield of thin glass is improved and the thickness is controlled more accurately, the production capacity of thin glass is expected to be further improved.

2.4 The impact of photovoltaic glass thinning on cost

With the reduction of thickness and large-scale production, the manufacturing cost and selling price of thinned photovoltaic glass will decrease correspondingly. At present, the market price of 2.5mm semi-tempered glass is 10-12% lower than that of 3.2mm tempered glass, and the price of 2.0mm semi-tempered glass is 12-15% lower than that of 3.2mm tempered glass.

2.5 Impact of photovoltaic glass thinning on energy and environment

The production of photovoltaic glass is a process of high energy consumption and pollutant emission. At present, more than 90% of the global photovoltaic glass furnaces are built in China. If we can increase the capacity of a single kiln through the thinning of photovoltaic glass to meet more market demand, on the other hand, it is to reduce the number of kilns, thereby reducing energy consumption and environmental pollution.

Large size direction of photovoltaic glass

3.1 The size of photovoltaic glass

For a long time, photovoltaic modules have been mainly packaged using 60 or 72 M2 cells. The corresponding photovoltaic glass size is mainly 1.6 to 2.0 meters in length and 0.9 to 1.0 meters in width.

In order to improve the yield rate and reduce costs as much as possible, the production lines of photovoltaic glass manufacturing companies are basically set according to the standard that the glass length does not exceed 2.2 meters and the width does not exceed 1.1 meters. If this size is exceeded,  most of the photovoltaic glass  manufacturing company can produce.

3.2 The size of photovoltaic glass in the future

With the rise of half-sheets, shingles, and large-size cells, the design of photovoltaic modules has become larger and more complex, and the size of photovoltaic glass has become larger and more.

Recently, the glass size of the 600W photovoltaic module of the M12 battery is designed to be close to 2300mm in length and about 1300mm in width. At the same time, the glass size of the latest M6 battery 500W photovoltaic module (6*14=84 cells) is designed to be about 2400mm in length and 1050mm in width . The author believes that in the next 1 to 3 years, the maximum length of large-size photovoltaic glass is about 2400mm, and the maximum width is about 1300mm.

Under the pressure of the continuous decline in BOS costs and the goal of fully achieving "parity online", the author believes that there will be more and more photovoltaic module companies participating in the competition of high-power modules, and large sizes will appear in the third quarter of 2020. Mass production and launch of components.

Differentiation direction of photovoltaic glass

4.1 Double-coated high-transparency glass

Compared with the conventional single-layer coated photovoltaic glass, the double-layer coated high-transparency glass has two major characteristics of improving the solar light transmittance and enhancing the moisture resistance of the photovoltaic glass.

The principle of double-layer coating to improve the solar transmittance is: first coat the bottom film and the surface film on the surface of the photovoltaic glass. The main component of the bottom film is silicon dioxide, the refractive index is 1.44, the thickness is about 80nm, the surface film and the conventional single same layer coating, refractive index is about 1.29, thickness is about 110nm. By adjusting the thickness of the base film and the surface film, the reflectance of sunlight can be further reduced and the light transmittance in the infrared band can be increased, thereby obtaining a higher solar transmittance than single-layer coated glass.

The principle of double-layer coating to enhance the moisture resistance of photovoltaic glass is: because the underlying film is a dense silica layer, it can better block the moisture in the air from reaching the glass surface, and better avoid the hydrolysis reaction of Na₂SiO₃ in the glass. The formation of metal hydroxides further erodes the SiO₂ film structure and eventually leads to a decrease in the transmittance of photovoltaic glass. Therefore, the double-coated glass has better performance to adapt to the hot and humid environment. Judging from the humid heat test report of the authoritative testing agency, double-layer coating does have better performance of resistance to humid heat than single-layer coated glass.

4.2 Double-coated colorless glass

Double-layer coated glass can reduce the light reflectance of the ultraviolet and infrared bands by adjusting the thickness of the bottom film and the surface film, so that the appearance color of the double-layer coating looks very light, and can even be adjusted to "transparent color", so it is called "double-layer coated colorless glass".

The single-layer coated glass has a high light reflectivity to the ultraviolet and infrared bands, so the surface of the single-layer coated glass is prone to appear red and purple, and the overall appearance appears to be a non-uniform blue.

For European and American rooftop customers, they have higher requirements for the appearance and color consistency of photovoltaic modules. Therefore, some well-known domestic and foreign module companies have begun to choose double-coated colorless glass as their special photovoltaic glass for roof modules, especially black. The choice of roof components is more inclined to choose double-coated colorless glass.

The cost increase of double-coated colorless glass is basically the same as double-coated high-transparency glass. The author believes that as the cost of photovoltaic modules decreases, the demand for rooftop photovoltaic modules will further expand, and the demand for double-coated colorless glass will definitely grow rapidly.

4.3 Photovoltaic glass for special applications

It is understood that some component companies abroad have developed towards BIPV (Integrated Building Photovoltaic Power Generation) or RIPV (Integrated Roof Photovoltaic Power Generation). This type of component may require special sizes and shapes of photovoltaic glass, or may need to be used in different types of colors or patterns are printed on the surface of photovoltaic glass. Although the application of BIPV and RIPV is still very few at present, in the long run, BIPV or RIPV is an inevitable application development direction, that is to say, the photovoltaic glass industry should also consider the needs of society in this regard trend.