My friend, have you ever heard of photovoltaic?

"isn't it just using solar energy to generate electricity? "I'm sure a lot of people can blurt it out.

Compared with today's endless stream of cutting-edge technology, solar energy has been in people's field of vision for at least a few decades, and it is really not new, and photovoltaic companies have not caused any waves in recent years.

But in 2020, everything was suddenly different.

With the inclusion of "carbon peak" and "carbon neutralization" in the Government work report in 2021, and the carbon peak in 2030, the carbon neutral emission reduction schedule in 2060 has become the hottest concept in the capital markets. not even one of them.

The so-called carbon neutralization, generally speaking, is to offset the carbon dioxide emitted in the production process by various means, and finally achieve zero carbon dioxide emissions. One of the main ways to achieve this is to replace traditional fossil energy with "clean energy" and reduce carbon emissions from energy production.

Photoelectric is such a kind of "clean energy".

In the early years, due to technical limitations, the cost of photovoltaic power generation was too high, and its application was not economical enough. However, with the rapid iteration of technology and industrial upgrading, the cost of photovoltaic power generation has dropped by more than 90% in the past decade, even lower than conventional energy in some countries.

Driven by the policy, the demand for photovoltaic equipment has soared, and a huge blank market has emerged.

According to the forecast of China Photovoltaic Industry Association, the average annual installed capacity of photovoltaic in China during the 14th five-year Plan period will be about 1.5 times that of 2020.[1]. Globally, Bloomberg predicts that photovoltaic and wind power will account for 56% of the global power structure by 2050 (see chart below).[2]。

How can an industry with great potential get less profit-seeking capital?

The IEA of the International Energy Agency predicts that renewable energy will become the world's largest source of electricity around 2030, and nearly 60% of global power investment between 2015 and 2040 will go to renewable energy.[2]。

With the top-level design, market demand, technology accumulation, even the money is in place, multiple benefits are ready, and the opportunity for photovoltaic take-off seems to be at hand.

So, do you know anything about the photovoltaic industry chain?

What does the photovoltaic industry chain look like?

Generally speaking, the upstream of the industry is the preparation of raw materials from silicon to silicon wafers; the middle reaches is from photovoltaic cells to the manufacturing of photovoltaic modules, which is responsible for the production of effective power generation equipment; downstream is the application end, that is, photovoltaic power generation system.

Compared with the same semiconductor chips, the photovoltaic industry chain can be said to be very simple-of course, relatively speaking, there are still a lot of technical details.

In this paper, the magnifying lamp (ID:guokr233) divides the industry chain into seven parts from top to bottom, disassembles the whole photovoltaic industry chain for readers, and introduces the core raw materials, key technologies and future trends of the industry:

• Photovoltaic silicon: control the upstream of the industry

• Photovoltaic silicon wafer: monocrystalline silicon completely replaces polysilicon

• Photovoltaic cells: continuous upgrading and rapid progress

• Photovoltaic module: the foundation of solar power generation

• Photovoltaic auxiliary materials: no silicon, also important

• Photovoltaic Inverter: the Last piece of Photovoltaic Internet Jigsaw

• Photovoltaic power station: the terminal of industry

Photovoltaic silicon: control the upstream of the industry

Polysilicon material is an electronic material with industrial silicon as raw material and purified by a series of physical and chemical reactions to reach a certain purity. it is the main raw material for manufacturing silicon polishing wafers, solar cells and high-purity silicon products. it is the most basic raw material for the information industry and new energy industry.

Polysilicon is a form of elemental silicon. When molten elemental silicon is solidified under supercooled conditions, silicon atoms are arranged in lattice form to form nuclei. If these nuclei grow into grains with different plane orientations, these grains combine and crystallize into polysilicon.

First of all, it needs to be clarified that polysilicon (material) is not equal to polysilicon (wafer). Polysilicon wafer is a product made of silicon material through a series of processes, which is located in the middle of the industrial chain. Because the distinction between the two names is not high, they often cause misunderstandings. The polysilicon material here is also the raw material for the preparation of monocrystalline silicon.

The purity of polysilicon determines its application field. The purity of solar-grade polysilicon used in photovoltaic is generally between 6N~9N (that is, 99.9999% to 99.999999%, a few 9 is a few N). The purity of electronic-grade polysilicon used in the production of semiconductors and other electronic components should reach 11N, which is much more difficult than the solar energy level.

From a global point of view, the polysilicon industry is continuing to transfer to China, and the epidemic has accelerated this process. In 2020, global polysilicon production capacity was 608000 tons, down 9.9% from the same period last year; production was 521000 tons, up 2.6% from the same period last year.

In the same period, China's polysilicon production capacity was 457000 tons, down 1.9 percent from the same period last year, and the output was about 396000 tons, up 15.8 percent from the same period last year. The growth of domestic polysilicon production capacity and output leads the world by a large margin, accounting for 75% and 76% respectively.[4]。

In addition to capacity transfer, polysilicon is also an industry with obvious Matthew effect.

By the end of 2020, China's polysilicon CR5 (the market share of the top five largest enterprises, that is, industry concentration) has reached 87.5%. There are 4 enterprises with a production capacity of more than 50,000 tons (adding up to more than 40% of the total global production capacity).[4]. Large domestic polysilicon manufacturers also occupy a key position in the global supply chain, which means that capacity transfer also strengthens the pricing power of domestic enterprises.

With the advantages of capital and technology, leading enterprises always maintain more orders, higher operating rate and high profit margins brought by economies of scale, which further ensures the first-mover advantages of leading enterprises in R & D and production technology upgrading in the future. On the other hand, less competitive enterprises have gradually shut down, which affected the decline in global production capacity in 2020.

As the upstream of photovoltaic industry, polysilicon is the core material of mainstream solar cell production process, and its price is also one of the core factors affecting the terminal price of photovoltaic products.

In the early stage of the development of the industry, affected by the low level of production technology, the consumption of silicon is relatively large, and the price of raw materials is also on the high side, resulting in a very high proportion of silicon in the total cost of photovoltaic equipment at that time. In 2010, the cost of cells (including silicon components) in a photovoltaic module was as high as 91%. By 2019, it has dropped to 48%, almost halving.[5]。

It can be seen that as the upstream silicon material has less and less influence on the terminal, it is an important trend. This is mainly due to the continuous decline in production costs brought about by the continuous progress in processing technology.

In terms of silicon production, benefiting from the continuous progress of the mainstream technology "improved Siemens method", the industry average production cost of polysilicon has continued to decline, which has greatly reduced the silicon purchasing prices of downstream enterprises. To some extent, this has opened up profit margins for the downstream, but also stimulated the willingness of enterprises to produce photovoltaic modules.

The basic principle of the improved Siemens method is that high purity trichlorosilicon (Cl3HSi) is reduced by high purity hydrogen on the high purity silicon core at about 1100 ℃ to form polysilicon deposited on the silicon core. Compared with the traditional process, it has the matching process of energy saving, consumption reduction, recovery and utilization of by-products and a large amount of by-product heat energy at the same time.

At present, the modified Siemens method is the most mature, widely used and fastest expanding process for the preparation of polysilicon. The product of this route is in the form of rod silicon, and the rod silicon produced by this method accounts for about 97.2% of the country's total output in 2020.[3]。

In addition to the "improved Siemens method", at present, there is a "silane fluidized bed method" for the preparation of polysilicon materials (which is decomposed by silane method in a fluidized bed reactor and polycrystalline silicon particles are formed on the surface of pre-loaded fine silicon particles. The product is in the form of granular silicon), which has a cost advantage over the current mainstream process and can supplement the industry to a certain extent. However, the technology is not mature and the process is flawed, which limits the proportion of production capacity in the industry.

Although the price of silicon has fallen significantly in the long run, there has been a crazy rise since 2021. In just half a year, the price of polysilicon has risen several times, from 85 yuan / kg to more than 200 yuan / kg, and some bulk orders have even reached 225 yuan / kg.[6]。

The soaring upstream raw materials have led to serious pressure on downstream photovoltaic enterprises, and the China Photovoltaic Industry Association even called on "all members and photovoltaic enterprises to abide by the law, operate rationally, and respect the spirit of contract." consciously resist excessive hoarding of polysilicon and silicon wafer products, driving up prices, as well as speculative behavior that is not their own production and operation demand. "[7]

The reasons for the current situation are complicated.

First of all, we can not rule out the existence of some enterprises to cherish sales, price increases and other bad behavior. Some people in the industry say that the current silicon production capacity can meet the downstream demand, which is because downstream enterprises deliberately create signs of polysilicon shortage and coordinate to bid up prices.[7]Of course, the details are difficult to verify.

Secondly, the shortage of upstream production capacity also exists objectively. Affected by the policy, downstream companies in order to occupy market share as soon as possible, head companies in the rapid capacity expansion, there is indeed the phenomenon of grabbing orders and occupying upstream capacity-which is very similar to the recent chip shortage. Correspondingly, the capacity expansion on the supply side of the upstream is bound to lag behind, and the expansion cycle of silicon material is already longer than that of the downstream, which further aggravates the mismatch between supply and demand and contributes to the shortage.

But overall, short-term abnormal shocks are unlikely to be a long-term trend. After the upstream and downstream production expansion is completed and the demand stabilizes, silicon prices will return to normal, and the long-term trend of price reduction will not change.

Photovoltaic silicon wafer: monocrystalline silicon completely replaces polysilicon

Silicon wafer is the end of the upper reaches of the industrial chain and the starting point of photovoltaic products. Its shape, size and thickness depend on the production process and downstream product design requirements. The further processing of the silicon wafer is the crystalline silicon cell chip, and the battery chip is the solar panel after arrangement, packaging and combination with other auxiliary materials, which is the smallest effective power generation unit of the photovoltaic system.

Briefly summarize the production process of silicon wafers: after a series of processes, the polycrystalline silicon material mentioned in the previous section is made into monocrystalline silicon rods, or ingots are made into polycrystalline silicon ingots, and then sliced into silicon wafers.

At present, photovoltaic silicon wafers have two kinds of product forms: single crystal and polycrystal, but there is a generation gap between them.

The crystal quality, electrical and mechanical properties of monocrystalline silicon are excellent, and the photoelectric conversion efficiency is better, but the production cost is high in the early stage of the development of the industry, so it has not been widely used. At this stage, polycrystalline products rely on price advantages and dominate the market for a long time.

With the continuous progress of silicon production process, rod pulling process and the final cutting process, the production cost of monocrystalline silicon has dropped rapidly. At the same time, the new generation of cell technology, represented by PERC cell (the back battery of passivation emitter, Passivated emitter rear contact solar cells,), has a higher utilization rate of monocrystalline silicon wafer, which further widens the existing gap in photoelectric conversion efficiency.

Under the rise and fall of cost and conversion efficiency, monocrystalline silicon is rising rapidly. By the end of 2020, the market share of single crystal silicon wafers has increased from 20% in 2016 to more than 90%, and polysilicon wafers have been fully replaced.[8]。

In addition to the dispute over the route between monocrystalline silicon and polysilicon, wafer manufacturing is also focused on reducing production costs.

One of the measures is to "get bigger", that is, to increase the size of a single chip, which is one of the main trends of silicon wafers at present. At present, there are five mainstream sizes of photovoltaic wafers, which are 156.75mm, 158.75mm, 166mm, 182mm and 210mm.

Large dimensions are accelerating. 156.75mm and 158.75mm specifications are being rapidly phased out, 166mm has become the mainstream, and 182mm and 210mm production capacity has continued to increase, rapidly entering the market.[3]。

The reason behind this is that the power generation efficiency of large-size silicon wafers is higher, and the non-silicon cost of end products (energy, manpower, accessories, etc.) is lower.

In a nutshell, the production rate of the battery / solar module downstream of the silicon wafer is relatively fixed, which has little to do with the size of the silicon wafer.

If the larger wafer area means that the total power of the battery / module produced per unit time is higher, the corresponding production cost per watt will be diluted. Secondly, the amount of some auxiliary materials, such as junction box, filling glue, bus box, DC cable, etc., has nothing to do with the area of the battery, but only related to the number of battery blocks. Under the same conversion efficiency, the consumption of these auxiliary materials of large size battery is also lower than that of small size, which further reduces the non-silicon cost.

The accumulation of this series of advantages is the increase in terminal profits, which is estimated to increase by nearly 0.1 yuan per watt of gross profit.[9]. However, large size also requires the synchronous improvement of downstream production process and the coordinated development of a certain industrial chain.

In addition, the loss of silicon in the production and slicing process will also lead to the increase of production cost, how to reduce the silicon consumption in the production process is also important.

From the macro trend, the comprehensive silicon consumption per watt (g / W) continues to decline, and the unit silicon consumption in 2019 is 4.3g/ watts, which is only 31% of that in 2009.[10]. The substantial improvement in the utilization rate of raw materials will naturally lead to simultaneous growth of profit margins. At present, the main way to reduce silicon consumption is to reduce wafer thickness and chip loss.

Wafer thinning: from the perspective of industrial development trend, the decline in wafer thickness is another long-term trend-this not only effectively reduces silicon consumption and increases the number of wafers, thus achieving cost reduction, but also brings more product design routes for downstream battery pack design. At present, the mass production thickness of single crystal silicon wafer is 170 ~ 180 μ m, which is more obvious than that in the early stage of the industry. some enterprises using cutting-edge technology have been able to realize the production of 140 μ m single crystal silicon wafer, and there is considerable room for cost reduction in the future. In the long run, the technical route pointing to the thickness of 120 μ m is also relatively clear, but it is limited by the production technology and is far away from commercialization.

Chip loss: blade loss is the main source of loss in the process of silicon cutting. Compared with the traditional cutting method, the new generation of WEDM technology has a series of advantages, such as fast cutting speed, high rate of good products, low loss of single chip and so on. High-level cutting technology also contributes to the further thinning and enlargement of silicon wafers, which can help improve the design of silicon wafers and reduce production costs.

It can be seen that at present, the development route of the upstream of the photovoltaic industry is very clear, and everything revolves around cost reduction.

Although there is a battery route that does not use silicon wafers, it is far away from commercialization and can not shake the dominance of silicon cells. In the next few years, how to produce silicon more efficiently, although increasing the wafer output rate and reducing the subsequent installation cost at the same cost, will still be the same development direction in the upstream of photovoltaic.

Photovoltaic cells: continuous upgrading and rapid progress

After introducing the silicon wafer, now let's understand the starting point of the middle reaches of the photovoltaic industry, the core component of photovoltaic power generation-photovoltaic cells.

The so-called photovoltaic cell is a kind of semiconductor sheet that uses solar energy to generate electricity. As long as certain lighting conditions are met, the battery chip can output voltage and generate current in the case of a loop.

At present, the mainstream photovoltaic cells are processed from silicon wafers through a series of processes, because this process is more complex and is not the core of this paper, so only the schematic diagram is listed, and I will not repeat it.

Battery sheet is the core factor that determines the overall performance of the module, and its importance to photovoltaic power generation is self-evident: the most important index of photovoltaic module is power generation, and the power generation system of photovoltaic module is made of photovoltaic cells in series and parallel. From the principle level, the photoelectric conversion rate of the battery chip directly determines the overall generating power of the module.

The existing technical routes of photovoltaic cells are many and complex. In addition to the mainstream monocrystalline silicon PERC cells, there is also a certain amount of BSF cells using the previous generation of battery technology, while the new generation of N-type cells are also rising rapidly and are expected to replace PERC cells to become the next generation of mainstream products.

Adding other elements into semiconductor silicon and adding a large number of free electrons, semiconductors mainly rely on electrons to conduct electronics. such products are called electronic semiconductors, or N-type semiconductors. Photovoltaic cells that use such semiconductors are N-type cells.

At present, single crystal PERC products, as mainstream photovoltaic cells, have mature production process, high production capacity, and photoelectric conversion efficiency up to 23%, which has obvious advantages over the previous generation of BSF cells, and is the most cost-effective battery technology route. But the problem with PERC battery is that its efficiency is approaching the theoretical limit of 24.5%, and the optimization space in the future is very limited. This is one of the main reasons why the industry is looking for the next generation of batteries.

N-type battery is a relatively mature and clear technical route in the industry. There are many subdivision routes of N-type battery, and the general conversion efficiency has exceeded the average level of 24%. It has great potential and considerable room for commercialization in the future. At present, the main N-type batteries can be divided into three categories: TOPCon, HJT and IBC.

The biggest feature of the technical route of TOPCon: is that the theoretical photoelectric conversion efficiency is extremely high, reaching 28.7%, which is close to the limit of crystalline silicon (29.43%), which is obviously better than PERC (24.5%) and HJT (27.5%).[12]. Regardless of the theoretical value, the current mass production average efficiency of TOPCon batteries is also 24%, which is higher than that of mainstream battery products. Another advantage of this route is that it has low requirements on the production line, can be upgraded based on the existing PERC production line, is more friendly to upfront investment, and can improve the application cycle of the existing production line.

However, the shortcomings of the TOPCon route are also obvious, and its production process is not yet finalized and very complex, with as many as 12-13 processing procedures, which is much higher than 9 channels of PERC batteries. As a result, the rate of good products is relatively low, and the complex production process also pushes up the production cost. Under the influence of these factors, the further mass production of TOPCon battery is limited.

HJT battery: also known as heterojunction battery or HIT, HDT, SHJ battery, is considered to be the most promising technology route to become the next generation mainstream. The average photoelectric conversion efficiency of HJT battery is about 24%, which is significantly higher than that of PERC battery, which can effectively increase the power generation and dilute the cost of power generation. Another core advantage of HJT batteries is that there are fewer processes-there are only four steps in the product process, and fewer process steps are useful to improve the yield.

Cold knowledge: the earliest developer of heterojunction battery was Sanyo of Japan, but the company later registered HIT as a trademark, making it impossible for other companies to use this acronym to refer to heterojunction battery. This is why heterojunction batteries are called more.

But fewer production processes and low production costs are two different things. The biggest problem with HJT batteries is that the production cost is too high: according to Solarzoom statistics, the current cost of HJT batteries is about 30% higher than that of PERC batteries, which is obviously unacceptable to the photovoltaic industry, which puts cost reduction first.[13]. The cost of HJT, first, because of the high requirements for raw materials, consumption is also relatively large; second, because the production equipment and existing equipment are not compatible, the need to rebuild the production line has greatly pushed up the pre-cost; third, the product processing technology is also more complex.

Generally speaking, although it is generally favored by the industry, HJT still needs a more mature production process and a better cost reduction route in order to achieve large-scale commercialization as soon as possible.

IBC battery: this is the technical route with the highest conversion efficiency in photovoltaic cells at present. In the early stage of research and development, the photoelectric conversion efficiency of IBC battery has exceeded 25%, which is better than other batteries on the market. But IBC is also the most immature technical route: its production process is very complex, the processing cost is extremely high, and the production equipment is expensive. This makes IBC batteries face more difficulties in commercialization than other technical routes.

On the market side, with the gradual landing of new production capacity of PERC battery chips in 2020, the market share of this route continues to increase, rising to 86.4%. Due to the relatively old technology and weak power generation capacity, the market share of BSF batteries has dropped to 8.8%, down 22.7% from 2019, and has been basically eliminated by the market.[14]. Due to the cost problem, the production scale and consumption of N-type batteries (mainly HJT [heterojunction] batteries and TOPCon batteries) are still limited, and the current market share is about 3.5%, a small increase compared with 2019.

In addition to the traditional crystalline silicon cells, there is a completely different photovoltaic cell technology route-thin film solar cells.

The power generation principle of thin film solar cells is the same as that of crystalline silicon cells, but it uses a kind of photovoltaic materials with micron thickness prepared from non-silicon materials such as cadmium sulfide and gallium arsenide. Because the basic product form of this material is a layer of thin film, it is named thin film battery.

Thin film solar cells have the characteristics of low attenuation, light weight, low material consumption, low preparation energy consumption, suitable for combining with buildings and so on. However, because it is still in the early stage of research and development, the current conversion efficiency of thin film cells is not high. The laboratory efficiency of cadmium telluride thin film cells and copper indium gallium selenium thin film cells which can be commercialized is only 19.5% and 16% 17% respectively.[3]It is not even as good as the BSF battery, which is already on the verge of being phased out, and its power generation capacity is obviously On the other hand, the technical route with high conversion efficiency has a series of problems, such as the cost is too expensive, the production difficulty is too great and so on. The superposition of these factors leads to great difficulties in the commercialization of thin film cells.

Photovoltaic module: the foundation of solar power generation

Although a photovoltaic cell already has the power generation capacity, its power is too low for practical application. This is about the last link in the middle reaches of the photovoltaic industry, the smallest effective power generation unit of the battery and photovoltaic industry, which undertakes the photovoltaic conversion equipment in the photovoltaic power station-photovoltaic modules.

Photovoltaic modules, or solar panels, both refer to the same product, the equipment pictured above. The photovoltaic module is made of battery chips in series / parallel, encapsulated, and then installed with other auxiliary materials. From the position of the industry chain, the photovoltaic module is located between the photovoltaic cell and the photovoltaic system, which is the final product of the photovoltaic manufacturing industry.

The preparation of photovoltaic module mainly includes two steps: battery interconnection and lamination.

Battery interconnection determines the electrical performance of the module. at present, the standard number of photovoltaic modules is 60 or 72, which is connected by 10 or 12 copper wires as bus bars, and six groups of photovoltaic modules are interconnected into one photovoltaic module.

After the battery sheet is interconnected, it is generally necessary to package the battery sheet and the back plate together in the order from bottom to top according to the toughened glass, the plastic film, the battery sheet and the back plate, and the back plate and the toughened glass encapsulate the battery sheet and the film inside. It is protected by aluminum frame and silica gel seal edge. After lamination treatment, the service life of photovoltaic modules can be greatly improved, and the environmental tolerance and mechanical properties can be significantly optimized.

At present, the two main development trends of photovoltaic cells are double-sided modules and half-chip packaging.

The so-called double-sided module, as the name implies, refers to the use of double-sided battery photovoltaic modules, characterized by the positive and negative sides have the capacity to generate electricity. When the sun shines, part of the light will be reflected to the back of the module by the surrounding environment, and the double-sided component has the ability to collect this part of the light energy, thus increasing the power generation.

It is obvious that compared with the traditional single-sided design, the power generation power of double-sided battery is better, which can effectively reduce the average power generation cost of the power station. Accordingly, the production process of double-sided battery is also more complex, its back can not use opaque conventional backplane, superimposed with other production processes lead to slightly higher cost.

However, after the efficiency and income-increasing ability of the double-sided design has been verified, the downstream power stations have gradually accepted this technology. The market share of double-sided components in 2020 has increased by 15.7 percentage points from 2019 to 29.7%, and is expected to continue to expand in the future.[3]。

Half-chip packaging is the current mainstream packaging mode, which refers to cutting the battery sheet into two half-pieces of the same size along the direction perpendicular to the main grid line of the battery. The current generated by the photovoltaic battery in the process of power generation is related to the area of the photovoltaic battery, so the current passing through the main grid line in half of the cell is only about 1 / 2 relative to the whole chip. When half of the battery is connected in series, the resistance of a single positive and negative circuit remains unchanged, and the power loss of the single circuit is reduced to the original 1amp 4, thus reducing the overall power loss of the module and reducing the negative impact of component heating on power generation capacity.

In general, during the packaging process of the battery module, there will be a phenomenon called CTM (Cell-to-Module Loss) loss, that is, the total power generated by the module is less than the sum of the total power of the battery chip. Therefore, in addition to improving the photoelectric conversion efficiency, reducing CTM loss is also one of the ideas of component development. Half-chip packaging performs well on this point, and has the characteristics of relatively simple production process and low upgrade cost of the production line, so it has been widely used.

By 2020, the market share of half-chip packaging has reached 71%, an increase of 50% over the same period last year, surpassing full-chip packaging to become the absolute mainstream of the market.[15]。

In addition to the above two trends, there are many other routes of photovoltaic modules, such as splicing, tile, no main gate and multi-main gate, and there are many market segments. However, these routes either change only some design details, or are not widely used, or can be superimposed with the current assembly process as a supplement, so they will not be discussed in further detail.

Photovoltaic auxiliary materials: no silicon, also important

To produce a photovoltaic module, the battery is obviously far from enough, and a series of non-silicon auxiliary materials are needed. The performance of auxiliary materials also has an important impact on the final performance of components.

At present, the common component auxiliary materials include interconnection bar, bus bar, toughened glass, glue film, back plate, aluminum alloy, silica gel and junction box.

From the cost point of view, the top five in the cost of auxiliary materials are frame, glass, plastic film, back plate and welding strip. Among them, the frame accounts for the highest proportion of non-silicon cost, while glass, glue film and backplane are the core auxiliary materials of photovoltaic modules, which have an important impact on the final performance of the equipment. We will explain these auxiliary materials and development trends in the following sections.

Frame

As the name implies, the frame is the outer frame of the photovoltaic module, which is sealed with silicone after packaging, which plays the role of fixation and edge protection. At present, the general photovoltaic module frame is made of aluminum, which is second only to the battery in the cost share of all kinds of components, and is the most expensive non-silicon auxiliary material.

However, the technical content of the aluminum frame is very low, and the cost share is high simply because of its commodity pricing model, the bargaining power of downstream producers is very low, and the pricing of aluminum frame products is basically synchronized with that of aluminum ingots. Cost reduction space can only be found in processing fees. And because the production threshold is low, there are many suppliers of aluminum frames, the competition is very fierce, the market has been fully negotiated, the space to further reduce costs is very small.

Glass

Photovoltaic glass is generally used as the packaging panel of photovoltaic modules, which is in direct contact with the external environment, and its weather resistance, intensity and light transmittance play a core role in the life and long-term power generation efficiency of photovoltaic modules. At present, there are three main product forms of photovoltaic glass: ultra-white embossed glass, ultra-white processed float glass, and transparent conductive oxide coated (TCO) glass.

Generally speaking, silicon photovoltaic modules mainly use ultra-white embossed glass or ultra-white float glass, on the one hand, it can protect solar cells and increase the service life of photovoltaic modules. On the other hand, ultra-white embossed glass and ultra-white processed float glass have relatively low iron content and higher light transmittance, which can improve the power generation efficiency of the module.

The development of photovoltaic glass is mainly driven by upstream and downstream, and the main trends are increasing and thinning, respectively.

The increase in size is mainly affected by the upstream. Due to the gradual growth of the size of the silicon wafer, the glass plate as the packaging panel must also increase synchronously in order to meet the upstream demand. However, at present, there are not many enterprises in the industry that can produce large-size glass, which leads to a certain degree of mismatch between supply and demand, helping to push up the price of glass. How to adjust the production capacity as soon as possible in the future is a challenge to the production enterprises.

To reduce the thinning, one is to reduce the cost, and the other is also related to the design of photovoltaic modules. At present, some double-sided components adopt the double-glass route in which both sides are encapsulated with glass, and both sides use 2.5/2.0mm thick glass instead of traditional 3.2mm. This is not only for the overall weight loss of the equipment, but also for cost considerations. Considering the continuous growth of the permeability of double-sided modules, the thinning of photovoltaic glass will continue in the future.

Glue film

The packaging film is generally made of organic polymer resin, which is in direct contact with the battery sheet inside the module, covering the upper and lower sides of the battery sheet, and plays a protective role in anti-water vapor, anti-ultraviolet and so on. At present, there are three kinds of mainstream film on the market, which are transparent EVA (polyethylene-polyvinyl acetate copolymer for short) film, white EVA film and POE (polyolefin) film.

The development of packaging film is also affected by the design of downstream photovoltaic modules. Although the two EVA films are still mainstream and have a combined market share of nearly 80%, their performance gradually lags behind the downstream demand and cannot solve the PID problem well, so they are not suitable for double-sided components and are selling market share.

PID effect (Potential Induced Degradation), also known as potential induced attenuation, is the packaging material of the battery module and its upper and lower surface materials. Ion migration occurs under the action of high voltage between the battery sheet and its grounding metal frame, resulting in the attenuation of module performance, which has a great negative impact on the service life and conversion efficiency of photovoltaic cells.

On the contrary, POE film has better barrier performance, so it is especially suitable for water vapor sensitive technical route, and water vapor is one of the main culprits leading to PID effect. Therefore, with the change of downstream demand, POE film is regarded as an upgraded substitute for EVA material, and its permeability increases rapidly, and its market share has reached 25.5% in 2020, and is expected to further increase in the future.[3]。

Back plate

The backplane is located in the outermost layer on the back of the solar cell module, which protects the solar cell module from the erosion of the external environment and plays the role of weather-resistant insulation. it is necessary to have a high level of resistance to high and low temperature, ultraviolet radiation, environmental aging, water vapor barrier, electrical insulation and so on.

At present, the photovoltaic backplane products on the market are extremely numerous and complex, and lack of a unified naming standard. The industry is usually divided into fluorine / non-fluorine two categories according to whether it contains fluorine or not, and further subdivided according to the processing technology. In order to reduce the reading burden of readers, different processes will no longer be explained here.

Generally speaking, the backplanes used in the market are mainly K structure, T structure, C structure, glass backplane, transparent organic material backplane, and other backplanes.

K (KPK/KPF/KPE) structure backplane is still the absolute mainstream of the market, accounting for 59.5% in 2019, while T (TPT/TPF/TPE) structure template, which is also a traditional product, has a market share of 14% in the same period.[17]. However, these two kinds of backplanes are opaque, which is not in line with the current development trend of double-sided battery modules (see below for details of double-sided components), and the market share begins to shrink. By the end of 2020, the market share of K-shaped structural backplane and T-shaped structural backplane fell by 13.7% and 3.2% respectively.

Accordingly, with the rapid growth of the market scale of double-sided components, the market share of glass backplane and transparent organic material backplane, which are included in the production because of light transmission, has increased rapidly, increasing by 14.2% and 1.5% respectively compared with 2019. Under the condition that the development trend of downstream components remains unchanged, their market share will continue to grow.[3]。

Welding strip

Solder strip, also known as tinned copper strip, refers to a kind of solder coated with a uniform thickness of tin base on the surface of copper strip, which is used in the connection between photovoltaic module cells to play the role of conductive electricity accumulation.

Although the proportion of welding strip in non-silicon cost is similar to that of backplane, its price is close to that of aluminum frame. 90% of the cost of photovoltaic welding strip comes from copper and tin as raw materials, which means that the production cost is basically determined by the bulk price of the current period. And the technical content of welding strip is also very low, after full competition in the market, the bargaining space is very small.

In addition to occupying the top five auxiliary materials, non-silicon components also include junction boxes, packaging silicone and so on. The prices of these production materials are relatively stable, the technical content is also general, and the pricing model is similar to frame and welding strip. Generally speaking, at present, there is little room for non-silicon cost reduction of photovoltaic modules, and it is dominated by commodity prices, and the bargaining power of downstream manufacturers is not very strong. It is already difficult for photovoltaic equipment manufacturers to further compress profit margins in the non-silicon sector.

But this does not mean the stagnation of technical iterations. At present, the three core raw materials, including glue film, backplane and photovoltaic glass, still have an important impact on the downstream product design and final performance. How to adjust products in line with the progress of battery technology is still an important development direction of core auxiliary materials manufacturers.

Photovoltaic Inverter: the Last piece of Photovoltaic Internet Jigsaw

Photovoltaic inverter is an electronic equipment that converts the direct current generated by photovoltaic modules into alternating current with adjustable frequency. As the grid-connected power supply needs to meet the quality requirements of the grid, the inverter can adjust the voltage waveform for the power grid or load, which can directly affect the power generation efficiency of the solar photovoltaic system.

According to the application scene and power, photovoltaic inverter can be divided into three types: centralized inverter, group series inverter and household inverter.

Limited by the application scenario, the photovoltaic inverter market is very stable, which is completely determined by the downstream power station, and it is almost impossible to change significantly. By the end of 2020, the photovoltaic inverter market is still dominated by centralized inverters and series inverters. Among them, the serial inverter occupies the main position, accounting for 66.5%, the centralized inverter accounts for 28.5%, and the latest distributed inverter has a market share of about 5.0%.[3]. According to the agency's forecast, this pattern will not change much in the long run.

Photovoltaic power station: the terminal of industry

Photovoltaic power station is the end of photovoltaic industry chain. In this link, photovoltaic equipment is finally connected to the power grid and transmits power, which is the scene of practical application of photovoltaic power generation.

Just as photovoltaic modules come from series-parallel photovoltaic modules, in order to build a photovoltaic power station, it is necessary to assemble photovoltaic modules in a certain way, and install the supporting structure to form a larger DC power generation unit-photovoltaic array. after that, a large number of photovoltaic arrays can be connected with photovoltaic inverters, distribution cabinets and other equipment, as well as the central control system, the photovoltaic power station can be built.

Similar to traditional power stations, photovoltaic power stations are divided into centralized and distributed types. In terms of market share, by the end of 2020, large surface power stations in China accounted for 67.8%, occupying the absolute mainstream, while distributed power stations accounted for 32.2%.[3]。

Centralized large-scale grid-connected photovoltaic power stations are large-scale photovoltaic power stations built centrally by installing a large number of photovoltaic arrays in uninhabited areas where solar energy is enriched, such as deserts or hills. The generation of the centralized photovoltaic power station is directly integrated into the public grid and connected to the high-voltage transmission system to supply long-distance load.

The main characteristic of the centralized photovoltaic power station is that the operation and maintenance is more economical, benefit from the scale effect, the power generation cost is relatively low, and the power generation is large, which can better meet the access requirements of the power grid. At present, centralized power stations are in the mainstream in China, and they are mostly distributed in the areas rich in light energy in the west.

However, the shortcomings of centralized photovoltaic power stations are also greater. The solar energy enrichment area in China is not a high-load area, which leads to a certain mismatch between supply and demand, so that the electric energy can not be absorbed locally, and there is a certain phenomenon of abandoning light and electricity. At the same time, due to the natural fluctuation of photovoltaic power generation, the centralized photovoltaic power station has a large load on the power grid, and photovoltaic access to the Internet has been more troublesome.

Distributed photovoltaic power station mainly refers to the use of small open space, or the surface of buildings, such as factory buildings, public building roofs and other surface construction of small power stations, in the sparsely populated developed countries occupy the mainstream.

The advantages of distributed photovoltaic power stations are mainly concentrated in small investment, fast construction, small area and so on, and directly on the user side, which can reduce the dependence on the power grid and reduce the line loss. At the same time, the distributed photovoltaic power station can also realize the local digestion of power generation, and then connect the surplus to the power grid. Compared with centralized power generation, the problem of abandoning light and electricity is not obvious.

The defect of distributed power station is that due to the highly decentralized characteristics, the requirements for the control system are relatively high, and the regulation and management are more complex.

Summary

Throughout the full text, we can find that the core development path of the photovoltaic industry is to use solar cells with higher photoelectric conversion efficiency to generate cheaper electricity. The whole industry follows this basic principle from the design of the upstream silicon wafer to the establishment of the downstream power station, and even the selection of some non-critical auxiliary materials in the intermediate link.

Summed up into four words, that is, "reduce costs and increase efficiency". If you want to rank two keywords, you have to reduce the cost before increasing the efficiency.

Contrary to many people's intuition, photovoltaic equipment can actually achieve a very high level of photovoltaic efficiency, more than 40%, nearly twice that of current mainstream batteries. However, this technology is extremely expensive and can only be used in facilities such as satellites and space stations at no cost. It is very far away from large-scale civilian and commercial use.

This is actually an economic account: simple stacking performance does not mean lower power generation costs, and finding the best cost-effective combination in the continuous progress of technology is the root cause of photovoltaic power generation being able to access the grid at an affordable price.

Of course, the cost of power generation down does not mean that the whole industry can rest easy. At present, there are still some problems in the photovoltaic industry.

Although solar energy has the advantages of inexhaustible and pollution-free, it also has unstable defects, which are obviously affected by day and night, weather and season. This is directly manifested in photovoltaic power generation, including a series of problems, such as large fluctuations in power generation, adverse to the stability of the power grid, difficult to connect to the grid and so on. At the same time, there is a phenomenon that the light energy enrichment area (northwest) is far away from the power load area (southeast coast) in our country, and there is an obvious mismatch between supply and demand, which leads to "abandoning light and electricity", resulting in waste.

To solve these problems, we need to seek breakthroughs in photovoltaic energy storage and grid-connected technology. at present, the common solutions are photovoltaic hydrogen production, chemical energy storage, local absorption, and so on-of course, this belongs to the downstream of photovoltaic. It is far away from the photovoltaic industry chain itself, so it is no longer carried out.

In short, it is hoped that the domestic photovoltaic industry can take advantage of the wave of "carbon neutralization" to further develop, so that industrial production and ordinary people can use clean energy from the sun as soon as possible.

After all, there is an adequate power supply, but also can protect the earth's environment, in any case will not be a bad thing.