Expert Proof: Polysilicon “Two Highs” Is a Misunderstanding

The photo shows the directional growth polysilicon ingot plant of LDK Solar.

Since the end of last year, the industry has rumors that the Ministry of Commerce intends to include polysilicon in the high-energy and high-emission "two-high" list. This argument has Yu Yan and Yu Lie. However, the reporter learned from the interview that the industry has other views.
A number of experts stated that starting from the reality of China's polysilicon industry and starting from the national energy strategy, in the entire industrial chain of photovoltaic products, the polysilicon production process can be green, and it can fully achieve discharge standards and even achieve through recycling. zero emission. Not long ago, the China Photovoltaic Industry Alliance had already submitted a report to the National Development and Reform Commission, the Ministry of Industry and Information Technology, the Ministry of Commerce, the Ministry of Environmental Protection, and the State Administration of Work Safety and other major polysilicon manufacturers in the United Nations, stating that there was no "high energy consumption and high emission" in polysilicon production. . So, is the polysilicon industry a "two-high" industry? The reporter conducted a thorough investigation in this regard.
Polysilicon is the basic raw material for the information industry and solar photovoltaic power generation industry. Many countries in the world list it as a strategic material, implement technology and market monopoly on China, and domestic demand depends on imports for a long time. China's polysilicon has been through many years of efforts by backbone enterprises such as Luoyang Silicon Silicon Technology, Jiangxi LDK Solar, Jiangsu Zhongneng Silicon Industry, and Sichuan Yongxiang Co., Ltd., and it has broken the technological ** and monopoly of the developed countries for many years to achieve large-scale production and supply. Solved the "one end" problem of the "two ends out" of the photovoltaic industry, and initially formed a strategic new industry.
However, the polysilicon industry has been plagued by the controversy over "high energy consumption and high emissions". Various preferential policies and scientific research have been hampered. This has dealt a fatal blow to a newly emerging industry. Luo Dazhong Silicon High Technology Co., Ltd. Deputy General Manager Yan Daya, and LDK Solar LDK Solar Technology Co., Ltd. President and Chief Operating Officer Yan Xingxue and other industry experts in detail to the reporter analyzed the polysilicon and the entire photovoltaic industry in the production process of energy consumption, energy contribution As well as its contribution to reducing the energy consumption of GDP, it analyzed the clean production process of polysilicon to facilitate the long-term healthy development of the industry.

Polysilicon in the entire product chain does not have high energy consumption. If only from a single polysilicon production, energy consumption is not low. However, in China, almost all large-scale enterprises do not only produce polysilicon, but extend the industrial chain to solar modules. In 2009, the world’s production of photovoltaic power generation modules was 10.5 GW, of which crystalline silicon solar cells produced 8.5 GW, thin film solar cells 1.6 GW, and crystalline silicon solar cells accounted for 84.16% of total production; in 2010, global photovoltaic cell production reached 21 GW. Compared to 10.5 GW in 2009, it has doubled. Crystalline silicon solar cells are still the mainstream of today's market.
The energy recovery period TP (year) of the photovoltaic power generation system = the total energy consumption of the manufacturing photovoltaic system/the annual power generation capacity of the photovoltaic power generation system, that is, the value-added effect of photovoltaic power generation. According to the above figure, the total energy consumption of photovoltaic power generation from silica to the system can be 2.597 kWh/Wp. Solar energy is abundant in western China. The annual average utilization hours of photovoltaic power generation systems is 3,000 hours (system efficiency has been considered). The eastern part is worse, about 1,000 hours, with an average of 1,500 hours, ie, one year for each peak-watt solar cell. 1.5kWh of electricity. From this, it can be calculated that the energy recovery period of photovoltaic power generation is 1.73 years. With the decrease in energy consumption of solar grade silicon materials (200kWh/kg-160kWh/kg), the efficiency of photovoltaic cells continues to increase (17%-22%), the substrate continues to thin, and the energy recovery period of crystalline silicon photovoltaic power generation systems may decrease To 1 year. If calculated according to its working life of 30 years, the energy-generating effect of the photovoltaic power generation system can reach more than 20 times. Thin film solar cells have an energy recovery period of only about 1 year. According to the calculation results, photovoltaic power generation can be completely used to produce photovoltaic cells and a benign and sustainable solar energy industry can be realized.
At present, the domestic production of solar modules has a service life of 25 years. Based on this calculation, after the solar energy components produced can realize energy recovery from production, they can generate electricity for about 22 years without any power consumption, and there is no emission of any pollutants. In fact, even after 25 years, the solar module's power generation efficiency is approximately equivalent to 80% 25 years ago, and it can still be used for a long time.
In 2009, during the visit to the International Solar Energy Research Center in Konstanz, Germany, the China Silicon Hi-Tech delegation saw a group of solar cell monocrystalline silicon cells produced in 1983. The conversion efficiency is still stable at 17%. Its life span has reached 27 years. According to domestic professionals, there are domestic monocrystalline silicon solar cell modules produced in 1977, used in meteorological observation stations, can still generate electricity, the calculated life expectancy has reached 33 years. With the improvement and stabilization of the quality of polysilicon in the country, polysilicon supply will gradually become affluent, and the high conversion rate, long-life, and low-cost benefits of solar photovoltaic power generation will be even more significant.

The prospect of photovoltaic power generation is beyond doubt

China has promised the international community that by 2020, the carbon dioxide emissions per unit of GDP will fall by 40%-45% compared with 2005, and the share of non-fossil energy in primary energy consumption will reach about 15%. Among them, following the development of wind power and nuclear power, solar photovoltaic power generation is the most promising.
Photovoltaic photovoltaic power generation has significant advantages over traditional coal-fired power generation. According to statistics: In 2009, the average national coal consumption was 342 grams of standard coal/kWh. The total energy consumption of photovoltaic power generation from silica to the system is 2.597kWh/Wp, and the standard coal is 888.2g standard coal/Wp. In 2010, the average is 335 grams of standard coal/kWh.
“Silicone solar cells have a 30-year life span and are basically maintenance-free. The average power generation during the life span is 1.5×30=45kWh. The standard coal is 19.73g standard coal/kWh, which is only 1/17th of coal-fired electricity. It is more energy!” Yan Dazhou, deputy general manager of Luoyang Silicon High-tech Co., Ltd., said to reporters.
Yan Dayu said that in recent years, China's polysilicon production has expanded and its quality has improved, which has created favorable conditions for crystalline silicon solar photovoltaic power generation to increase conversion, reduce costs, and prolong life. Domestic photovoltaic companies have adjusted the life expectancy of crystalline silicon solar cells to 40 years, and at the same time, the power generation efficiency has increased. The efficiency of polysilicon photovoltaic power generation is 18% to 20%, and the efficiency of monocrystalline silicon photovoltaic power generation is 20% to 22%. Between 1.3 and 1.5 yuan/kWh, and is expected to further reduce.
On April 28, 2008, the upstream and downstream industries of the domestic photovoltaic industry, in Luoyang, will reduce the cost of China's photovoltaic power generation to RMB 1 per kWh in 2012. According to this requirement, the price of polysilicon 2008 will be reduced to RMB 700/kg in 2009. The price has been reduced to 600 yuan/kg, and the price in 2010 has been reduced to 500 yuan/kg. Polysilicon manufacturers have tried every means to reduce costs and improve quality, and have already achieved all the requirements in advance. The price of photovoltaic building was also reduced from 3.5 to 5 US$/Wp to the current 1.5 to 2 US$/Wp, which has a significant effect. In addition: According to the learning curve of the photovoltaic industry, the installed capacity of photovoltaic power generation doubles and the cost of photovoltaic power generation decreases by 20%. In 2009, the installed capacity and ratio of the world are shown in the table below.

Polysilicon production can achieve zero emissions

Regarding the argument that polysilicon pollution is high, Yan Daya said that this is closely related to its production technology and processes, and that improved technology can completely achieve discharge standards and even achieve zero emissions. Polysilicon can be fully recycled. Its production uses silicon metal as raw material and reacts with hydrogen chloride to synthesize trichlorosilane. After the trichlorosilane is purified by distillation, it is reduced with high-purity hydrogen to obtain polysilicon products. During the reduction process, a large amount of tail gas is produced, and the components in the tail gas are separated by a dry recovery system, in which: SiCl4, SiHCl3 mixed liquid is sent for distillation purification, high-purity SiHCl3 is reduced to produce polysilicon, SiCl4 is sent to a hydrogenation system and converted into trichlorosilane. , Purification and then return to the use of the reduction system; HCl gas sent to the trichlorosilane synthesis process; hydrogen return to the reduction process to produce polysilicon. The entire polysilicon production system is an ideal closed-loop system for material recycling and energy recycling.
In the polysilicon production process, silicon tetrachloride is a by-product of polysilicon production. Each ton of polysilicon produced produces 10 to 20 tons of silicon tetrachloride. If it is not properly handled, it will directly affect production and cause environmental pollution. The mainstream process is to convert hydrogenation to trichlorosilane, become polysilicon feedstock, and return to the system. The auxiliary process includes the production of other products in the industrial chain such as gas phase white carbon black, ethyl silicate, high-purity quartz, optical fiber preforms, and organic silicon.
Polysilicon production "three wastes" treatment. Polysilicon production "three wastes": Exhaust gas: main component N2, containing a small amount of H2, HCl, Si2HCl2, SiHCl3, SiCl4, etc.; Wastewater: exhaust gas washing water, pure water preparation drainage, etc., acidic; waste residue: silicon powder, silicon dioxide , Limestone slag, etc., harmless, insoluble, is a general solid waste. Treatment method: The waste gas generated by the system is collected through the pipeline to the exhaust gas treatment tower in the three-waste treatment station, using the principle that the chlorosilane is easily hydrolyzed and the acid and alkali is neutralized, and the exhaust gas is sprayed with alkaline water in the exhaust gas treatment tower. , Neutral gas discharged from the top of the exhaust gas treatment tower, the main component is nitrogen and a small amount of hydrogen; ** and silica generated by the hydrolysis of chlorosilanes, ** reacted with the alkali to form neutral water, and meet emission standards after further treatment; The silicon is solidified by pressure filtration and shipped to the government designated dump site.
Taking LDK Corporation of Jiangxi as an example, the first-phase project of 15,000 tons of high-purity silicon material put into production by the company in September 2009 has been optimized and innovated through continuous refinement of the latest generation Siemens process, from distillation, hydrogenation, and Recovery and exhaust gas recovery form a fully closed-loop, full-recovery system. The power consumption per kilogram of polycrystalline silicon produced does not exceed 60 kWh, and the material consumption level is also controlled below 50% of the industry standard. The purity of the product is much higher than that of the current domestic refining and purification. Industrial standards, to reach the international advanced technology level. “At present, when this project is in operation, all wastes are recycled, and there is no harm to the environment without any pollution,” said Peng Xiaofeng, chairman and chief executive officer of Seville.
It can be said that at present, China's polysilicon production basically has no technical problems in the processing of “three wastes”. The domestic 1,000-ton-scale factories all have a “dry tail gas recovery” system, and the environmental assessment and inspection system is perfect. The factory is clean and the environment is beautiful. There is no "high emission".

Polysilicon energy consumption should not be simply compared Yan told reporters that some domestic experts and government officials compared polysilicon production with steel and electrolytic aluminum, that polysilicon consumption 200kWh/kg (standard coal 68.4kgce/kg); electrolytic aluminum power consumption 14kWh/kg (contract coal 4.788kgce/kg); of course, high energy consumption! "However, the use of the two is different, the value of the two is different, the added value of technology and the scale of the total energy consumption are different. The contribution to the country and its strategic significance are different. It is not appropriate to simply handle it." Yan Dazhou said.
For electrolytic aluminum, the current price of 14,600 yuan / ton, its million GDP output value index: 4.788/1.46 = 3.279 tce / million. In 2009, the country consumed 14.39 million tons of electrolytic aluminum, and consumed 14,000 kWh/t × 14.39 million tons = 2014.6 million kWh. In 2009, the country’s total electricity consumption was 369.73 million kWh, accounting for 5.45% of the total electricity consumption.
For polysilicon, according to industry estimates, even if the price of polysilicon drops from the peak of 400 US dollars per hour to the current level of about 65 US dollars, per ton of polysilicon electricity consumption converted 68.4 tons of standard coal, GDP output value of 65 × 6.83 × 1000 = 44.395 Ten thousand yuan/ton, its million GDP output value consumption index: 68.4/44.395=1.54tce/million, less than half of the energy consumption per million yuan of aluminum electrolytic production, lower than the national 2008 yuan output value of industrial output value 2.189 yuan At the same time, it can reduce carbon dioxide emissions by 30%.

Active expansion of polysilicon in foreign countries Although domestic polysilicon "two highs" have been continuously questioned, data show that large foreign companies are still actively constructing and expanding polysilicon projects.
The United States is the country with the largest polysilicon production. In 2009, the total output of polysilicon in the United States, Japan, Germany and South Korea reached 84,500 tons, an increase of 47.2% from 57,400 tons in 2008. Among them, 4 polysilicon factories in the United States have a total output of 48,000 tons, accounting for 45.8% of the world's total output. Among them, Hemlock's 2009 polysilicon output was 2,750 tons per year, ranking first in the world; Advanced Silicon (REC) Materials' output was 11,000 tons per year, ranking third in the world; MEMC's polysilicon production was 9,000 tons per year. fifth. Among the polysilicon companies in the United States, foreign shares account for the majority, Hemlock's shares are distributed: 63.25% for Dow Corning, 24.5% for Shin-Etsu in Japan and 12.25% for Mitsubishi in Japan; Advanced Silicon (REC) Materials Co., Ltd. was a full-time Japanese company in 2005. When the polysilicon market emerged, it sold all of its shares to Norway and changed its name to REC; Mitsubishi (US) was also a full-time Japanese company. The world's polysilicon projects gather in the United States. Thanks to the United States' preferential electricity prices for polysilicon plants, the price of electricity has long been 2 to 3 cents/kWh, with obvious advantages and tax concessions.
Since 2010, foreign polysilicon enterprises have expanded their production rapidly. Germany's Wacker's production capacity will reach more than 22,000 tons by the end of this year; the United States's Heimrock Company also announced that it will double its production capacity; Japan's Deshan Cao Da is also busy expanding its production.
It is understood that, to date, none of the traditional seven polysilicon companies has ever built a plant in China and no one has transferred technology abroad. It has been keeping polysilicon production in the country and exporting its products at high prices. The expansion is still in the United States, Germany, Malaysia and other places.
Polysilicon, like oil, coal and other products, is a core industry that is related to the future competitiveness of a big country. It is worth noting that at present, foreign polysilicon products are imported into China at a low price during the infant industry's development of China's polysilicon, and compete with customers for Chinese local polysilicon enterprises. The competition is extremely fierce.

Crystal silicon solar cell industry chain schematic

Crystalline silicon solar cell industry chain schematic energy consumption calculation boundary conditions Starting from the raw silica sand, to make crystalline silicon photovoltaic power generation system, the entire energy consumption EP expression:
EP = EP1 + EP2 + EP3 + EP4 + EP5 + EP6
Among them: EP1 is "silica sand - metallurgical silicon" energy consumption: 13kwh/kg;
EP2 energy consumption of “metallurgical silicon-polysilicon” 200kwh/kg (modified Siemens average in France);
EP3 is a "polysilicon-polysilicon chip" energy consumption 9 kwh / kg (currently the domestic mainstream, the use of multi-wire cutting machine slice energy consumption level);
EP4 is the power consumption of polysilicon film-polycrystalline silicon photovoltaic cell 0.2kwh/Wp;
EP5 is the energy consumption of “photovoltaic cell—photovoltaic module” with the energy consumption of 0.15kwh/Wp and the encapsulation material;
EP6 is a "photovoltaic module - photovoltaic system" energy consumption of 0.31kwh/Wp, including the energy consumption of grid-connected inverters, cables and other production.
The result of the calculation is:
Polysilicon production consumes industrial silicon raw materials: 1.5kg, that is, 1.5kg of metallurgical silicon is required for producing 1kg of high-purity polysilicon;
Drawing silicon rod or casting silicon ingot consumes high-purity polysilicon: 1.2kg, ie 1kg silicon ingot/silicon rod requires 1.2kg of high-purity polysilicon;
1kg silicon rods or ingots can be cut 60 pieces of 125 × 125mm silicon wafers (sheets can be cut 70 to 90), the average production of 2.4Wp solar cells per sheet, total: 144Wp/kg;
High-purity polysilicon needed to produce solar cells per watt: 1200g/144Wp = 8.3g/Wp (National advanced level: 6g/Wp);
Industrial silicon required for the production of solar cells per watt: 1.2 x 1.5 x 1000 g/144 Wp = 12.5 g/Wp;
According to the calculation of the above parameters, the power consumption of each link is as follows:
EP1 = 13 kWh/kg x 12.5 g/Wp/1000 = 0.1625 kWh/Wp
EP2 = 200kWh/kg x 8.3g/Wp/1000 = 1.66 kWh/Wp
EP3 =9kWh/kg÷144Wp/kg = 0.0625 kWh/Wp
Total energy consumption: EP = EP1 + EP2 + EP3 + EP4 + EP5 + EP6 = 2.545kWh/Wp
Solar module yield = 98% (ie, package yield)
Total energy consumption: 2.545/0.98 = 2.597kWh/Wp