Metallurgical polysilicon seeks a way out

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In the production process of polysilicon, the metallurgical method is trying to challenge the dominant position of the improved Siemens method by offering lower energy consumption and costs. 　　“With the continuous advancement and maturity of technology, it is only a matter of time before the metallurgical process gradually replaces the improved Siemens process as the main raw material for photovoltaic power generation. ”At the \"2010 International Symposium on Solar Polysilicon Production Using Metallurgical Methods,\" industry professionals from home and abroad attending the event claimed that in five years, polysilicon produced by metallurgical methods (hereinafter referred to as \"metallurgical method\") would account for half of the silicon used in photovoltaic applications. 　　However, industry insiders are well aware that the metallurgical method still needs to be tested by the market. Technological breakthroughs: “The entire photovoltaic industry is faced with the challenges of low costs and high efficiency. **Among the photovoltaic power plants to be built under the 12th Five-Year Plan, those that will be most popular are undoubtedly those that feature low costs and high efficiency.” ”In the view of Shi Jun, president of the Strategic Alliance for Technological Innovation in the metallurgical process for solar-grade polysilicon industry, the metallurgical process is a polysilicon production method that is efficient, energy-saving, and suitable for large-scale clean production, and it already boasts the advantage of low costs. 　　In terms of polysilicon production technologies, the improved Siemens method, the metallurgical method, and the silane method are the most widely used. The improved Siemens method is currently the dominant technology, accounting for around 85% of global production; the core technologies behind this method are in the hands of seven major silicon material manufacturers from countries such as the United States, Germany, and Japan. 　　“Given that the current metallurgical method is not yet fully developed and cannot be applied on a large scale in industrial production, the purity of polycrystalline silicon produced by this method is low, ranging only from 5N to 6N (where 1N corresponds to one 9, and 6N means 99.9999%). This is a significant difference compared to the purity of polycrystalline silicon produced by the improved Siemens method, which reaches levels of 9N to 11N. ”Li Shengmao, a senior researcher at CIC Consulting, told reporters that the metallurgical method has obvious shortcomings. 　　But the gap is narrowing step by step. “Currently, the efficiency of photovoltaic cells manufactured using the metallurgical method has increased from 13% to 17%, while the efficiency of single-crystal silicon cells has risen from 14% to nearly 18.5%. The degradation problem has also **improved**, and the photovoltaic performance of metallurgical-polished polysilicon is now on par with that of polysilicon produced using the improved Siemens method. ”Shi Jun said. 　　However, the metallurgical method also has clear advantages, namely that the investment required to produce polysilicon using this method is relatively low. If polycrystalline silicon is produced using the metallurgical method, the investment cost for a polycrystalline silicon production line with a capacity of around 1,000 tons is only about one-third of that for the improved Siemens method. Moreover, compared with the improved Siemens method, the most significant advantage of the metallurgical method is its low energy consumption. This technology uses inexpensive industrial silicon as raw material and employs metallurgical techniques to purify it; the process flow is short, and the overall energy consumption is only about 20% of that of the improved Siemens method. 　　In the view of Liu Yingkuan, chairman of Ningxia Power Generation Group (hereinafter referred to as “Ningxia Power Generation”), efficiency and purity are no longer issues. “In the first half of 2010, we achieved industrial-scale production of polycrystalline silicon using domestic electron beam furnaces, thereby enabling effective and stable phosphorus removal as well as the reduction of metal impurities. With this, the research and development as well as industrialization efforts related to the metallurgical method were completed, and we now have the capability to produce large quantities of 6N–6.5N solar-grade polycrystalline silicon in an effective and stable manner. ” 　　Liu Yingkuan said that having overcome the technical challenges related to impurity removal and purification, they are now pushing forward toward large-scale production. It is reported that in Ningxia, the projects for producing 10,000 tons of 4N high-purity silicon per year, 2,000 tons of solar-grade polysilicon per year, 1,000 tons of monocrystalline silicon per year, as well as a slicing production line capable of producing 25 million wafers per year, all began construction in April 2009 and are set to be completed and put into operation within this year. Additionally, the projects for producing 50 megawatts worth of battery modules per year and 100 megawatts worth of tracking systems per year have already been brought online. 　　It is understood that more than a dozen companies in China, such as Ningxia Power Generation and Shanghai ProNew Energy Co., Ltd., are engaged in the production of polysilicon using metallurgical methods, and their total output is expected to reach 3,000 tons by 2010. In addition to using the products for their own needs, some photovoltaic module manufacturers have also begun to show interest in polysilicon produced by the metallurgical method. For example, JA Solar Photovoltaic (Suzhou) Co., Ltd. (hereinafter referred to as “JA Solar”) reached a cooperation agreement with Ningxia Power Generation at the beginning of the year, signing a purchase contract for 80 tons of polysilicon produced by the metallurgical method. Cost competition: It is understood that the current cost of producing polysilicon using the improved Siemens method is between $20 and $50 per kilogram. In the view of Chen Genmao, one of the leading scientists at JA Solar, the cost of the metallurgical method needs to be reduced to between $10 and $25 per kilogram in order to be competitive. “If the price can be lowered and the quality further improved, then the metallurgical method has great market potential.” ” 　　Liu Yingkuan told reporters that now that the quality of polycrystalline silicon produced by the metallurgical method has become relatively stable, their focus is on further reducing production costs at a larger scale, with the goal of bringing the cost of 6N–6.5N solar-grade polycrystalline silicon down to below 150 yuan per kilogram. 　　Due to the limitations of the processing techniques, the purification limit of silicon using metallurgical methods is 6N to 7N, making it suitable only for the solar industry. Therefore, most industry professionals are cautious about metallurgical polysilicon. 　　“There has indeed been some progress in purifying polysilicon using metallurgical methods; the current standards seem to meet the requirements for solar cell production. However, the efficiency of the cells produced is not high, and if the production cost is 150 yuan per kilogram, it is still higher than the 20 dollars per kilogram required for producing silicon materials using the improved Siemens method abroad. ”An expert in solar cell research told reporters that as solar cells place increasingly higher demands on the quality of silicon materials, the technologies for improving the Siemens process and the silane process have become more sophisticated, resulting in fiercer competition for the metallurgical process. Although some manufacturers currently use raw materials with low levels of harmful elements that meet the requirements, it is very difficult to further increase the purity. 　　 However, many companies remain optimistic about the development prospects of the metallurgical method. “On the one hand, the characteristics of polysilicon produced by the metallurgical method meet the current industry demands for energy savings and emission reduction in the polysilicon sector. On the other hand, companies that use this method can significantly reduce production costs and enhance their competitiveness. At present, the conversion efficiency of the metallurgical method is close to that of the improved Siemens process, and there is still much room for improvement. The competition between these two technologies will be a long-term affair. ”Li Shengmao said.