成果報告書詳細
管理番号20120000000572
タイトル*平成23年度中間年報 太陽エネルギー技術研究開発 太陽光発電システム次世代高性能技術の開発 太陽電池用シリコンの革新的プロセス研究開発(シリカの直接還元プロセスの開発)
公開日2012/12/26
報告書年度2011-2011
委託先名国立大学法人弘前大学
プロジェクト番号P07015
部署名新エネルギー部
和文要約和文要約等以下本編抜粋:1. 研究開発概要
太陽電池の大規模な普及には、シリコン製造コストの低減が不可欠である。かつて川崎製鉄・日本板硝子がNEDO プロとして取り組んだシリカの直接還元プロセスは、収率の大幅向上や他の製造方法と同等の太陽電池効率を実現しながらも、操業不安定性や当時の市場規模などから時期尚早として中断されている。
英文要約Title:Direct Reduction Process of Silica(SiO2) to SOG-Si-- High Temperature Heating Reduction Process of Mixture Silica and Carbon Composite Pellet -- (FY2010-FY2012) FY2011 Anuual Report
The cost cut in silicon production is indispensable to the large-scale introduction of solar cells. The direct reduction process of silica tackled by Kawasaki Steel and Nippon Sheet Glass under the NEDO project was interrupted because of premature market and operation instability at that time in spite of its enough solar cell efficiency and yield improvement. Now, when the situation changed drastically, the direct reduction process of silica becomes the important strategy for solar cells on natural resource. One of the causes of the reduction instability is that the generated Sic walls blockade the reduction furnace. For the solution of this cause, we should elucidate complex reaction path (SiO2->SiO->SiC->Si), and develop control techniques on the reaction path.Our results in this fiscal year are as follows:(1) By the thermodynamic calculation, we found that the excess and deficiency of carbon contents causes to change reaction path drastically. Under the same condition for reaction temperatures and total ratio of raw powders, the separated 2 layers with SiC and SiO2+C powders generated silicon, while uniform mixed powders never generated silicon. This experimental result agrees the thermodynamic calculation. This result indicates that the reactive sites according to the reaction path should be separated. That needs to control the reaction path to control the mix ratio of raw powder. We proposed the possible method for operation stability of the shaft kiln by the control of mix ratio of powder. (2) The improvement was tried about the structure of the crucible. It divided into two steps of upper and lower sides and the maintenance in a furnace and the convection of the SiO gas generated at the first-step reduction reaction from the lower berth were promoted, and also an up-and-down temperature was controlled. Moreover, materials were divided into two layers (SiO2+C (below) and SiC (above)) inside the crucible, and then, the heating experiment was conducted. The result has shown that the amount of reduction Si(s) could increase more. The advanced two-step reduction furnace was designed and developed based on the above experimental results. (3) By discharge-plasma-sintering method, the pellet of SiO2 and C(1:1) made SiC at 1400 ℃. Compared with direct heating method, SiC was grown at low temperature considerably. This suggests the possibility that pulse current promotes the reaction of SiO to SiC.
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