Reflections on the development of solar photovoltaic industry (3)

Third, polysilicon will remain the main raw material of solar photovoltaic in a long time. Polysilicon is the main material for the preparation of crystalline silicon solar cells, accounting for about 30% of the final price of the entire battery. With the advancement and improvement of polysilicon production technology, its high prices will be gradually reduced, thereby reducing the cost of crystalline silicon cells.

(a) The polysilicon production process is relatively mature. The existing polysilicon production process technologies mainly include modified Siemens process, silane process, fluidized bed process, and metallurgical process. The modified Siemens process utilizes chlorine and hydrogen to synthesize hydrogen chloride, hydrogen chloride, and industrial silica fume to synthesize trichlorosilane at a temperature of 250-350°C. The trichlorosilane is then separated and purified, and the purified trichlorosilane is The chemical vapor deposition reaction in the hydrogen reduction furnace produces high-purity polysilicon. The polysilicon prepared by the modified Siemens method has high purity and good safety. Compared with the silane method and the fluidized bed method, the deposition rate is highest, and it is conducive to continuous operation. It is the mainstream technology for producing polysilicon, and the most mature technology, the lowest investment risk, the easiest With the expansion, the polysilicon produced accounts for 80% of the total production in the world today. Most of the existing polysilicon in China is prepared using the modified Siemens method.

(b) Polysilicon is not a "high energy consumption" or "highly polluting" industry. Now people often use “refining 1 ton of polysilicon to consume 160,000 kWh of electricity” to determine that the polysilicon industry is a high-energy-consuming industry. This view is one-sided. According to authoritative data, from the perspective of energy consumption per unit of production, under the current technological conditions, China's energy consumption per 10,000 PV modules (including polysilicon refining process) is about 900 kWh (if polysilicon is used alone, when polysilicon is sold at 300 In the case of 10,000 yuan/ton, the energy consumption per 10,000 yuan is 533 kWh. When the polysilicon price is 450,000 yuan/ton, the energy consumption per 10,000 yuan is 3,550 kWh. The energy consumption per 10,000 yuan in the steel industry is approximately At 3,900 kWh, the energy consumption per 10,000 yuan in electrolytic aluminum production is approximately 6,000 kWh. The energy consumption per unit of output in the photovoltaic industry is much lower than that in the iron and steel and electrolytic aluminum industries. At present, the energy consumption per unit of polycrystalline silicon is lower than that of steel and electrolytic aluminum. (Currently, high-energy-consuming industries and products are identified as local energy consumption according to the GDP of RMB 10,000 and industrial added value. There is no absolute number, it is a relative concept, it is a recognition issue.) More importantly, photovoltaic products are a kind of production. Energy products that consume energy during the process and produce energy during use are far more energy-efficient than energy. According to calculations, a 1 MW solar photovoltaic power generation system is installed in an area with medium light conditions in China, and the annual power generation is about 1.3 million kWh; a total of 2.37 kWh of electricity is used for the production and installation of a 1 watt solar photovoltaic power generation system, 1 MW. The production and installation of the solar photovoltaic power generation system requires 2.67 million kilowatt hours of power consumption. It takes only about 2.04 years to recover and balance its own power consumption. The average lifetime of solar modules is 25 years, and solar modules are used to realize production energy consumption. After recycling, it can generate electricity for about 23 years. In other words, the polysilicon solar cell system installed with 2.67 million kWh of electricity will eventually generate 32.5 million kWh of electricity. That is to say, the ratio of polysilicon photovoltaic production to electricity generation is 1:12.2, and the economic and social benefits are very impressive. . Therefore, simply using the energy consumption of polysilicon to identify the polysilicon industry as a high-energy-consuming industry is unscientific and even more objective. It is necessary to remove polysilicon photovoltaics as the hat of high-energy-consuming industries as soon as possible.

In addition, people often say that the polysilicon industry's pollution problem mainly refers to the production of a large number of byproducts of silicon tetrachloride in the production of polysilicon, and silicon tetrachloride has strong corrosion. At present, the improved Siemens method commonly used in polysilicon production plants has achieved complete recycling of silicon tetrachloride. Some polysilicon production companies cause pollution, and have a great relationship with inadequate environmental supervision and insufficient corporate investment. Technically speaking, Silicon chloride can not only be processed, but also can be recycled, and it can be used as a raw material to produce white carbon organic monomers and other products, through the recycling can solve the pollution problem, with the continuous improvement and improvement of the production of polysilicon technology, a large number of four Silicon chloride can be completely recycled.

(3) There is still a large space for the cost reduction of photovoltaic power generation. At present, the high cost of photovoltaic power generation is a key factor in the difficulty of large-scale promotion of photovoltaic power plants, and the high production cost of polysilicon is one of the important reasons for the high cost of photovoltaic power generation. The cost of domestic production of 1 kilogram of polysilicon is mostly in the range of 40-50 U.S. dollars, while the cost of foreign seven polysilicon producers is in the range of 20-30 U.S. dollars. The domestic polysilicon production costs still have a large space for decline. Realizing closed-loop production is the key to significantly reducing energy consumption in polysilicon production. It can reduce production costs through comprehensive utilization of exhaust gas, by-products, and waste heat recovery, while achieving the goal of energy conservation and emission reduction. Most polysilicon companies in foreign countries set up factories, which are mostly combined with chemical companies. They operate in the “chemical group” and can easily realize the “circular economy” within the group and can achieve “zero emissions” of wastes. Leshan “National Silicon Material and By-product Utilization Industrialization Base” uses silicon tetrachloride instead of hydrogenation of silicon tetrachloride for hydrogenation to produce trihalosilane, fumed silica, ethyl silicate, and organic silicon. Products, synthetic quartz and other materials have reduced polysilicon production costs by extending the industrial chain. With the improvement of solar cell module production and construction of large-scale solar power station technology, especially the upgrading of inverters and smart grids, there is still much room for reducing the cost of the entire solar photovoltaic power generation system. At present, some authoritative organizations in the world are optimistic about the future cost of photovoltaic power generation. The most optimistic forecast is that the cost of photovoltaic power generation will be reduced to 1.0-0.7 yuan/kWh by 2015, which will reach the level of traditional power prices. In 2009, the bidding price of Dunhuang Solar Power Station on the Internet was 1.09 yuan. On August 16 of this year, the National Energy Administration’s 280 MW photovoltaic power plant concession project was formally opened in 2010. A total of 50 companies in 13 projects submitted tenders for 135 minutes, ending in August. On the 17th, the minimum price for participating companies had bottomed out at 0.7288 yuan/kWh, indicating that solar power is closer to traditional energy prices, and the time for commercial promotion is not far away.