LOS COST, HIGH PURITY SILICON BY ALKALINE GLYCOLIC DIGESTION OF SILICA

THE SOLAR CELL APPLICATION OF CRYSTALLINE SILICON THIN-FILM, PHOTOCOLTAIC (PV) TECHNOLOGIES IS CURRENTLY LIMITED BY THE HIGH COST OF THE SILICON RAW MATERIAL. THIS IS A RESULT OF THE CARBOTHERMAL REDUCTION METALLURGICAL PROCESS USED TO CREATE THE SEMICONDUCTOR-GRADE SILICON FROM SILICA. THERE IS A NOVEL ALTERNATIVE ORGANOSILICON CHEMISTRY, BASED ON ALKALINE GLYCOLIC DIGESTION OF SILICA, THAT DOES NOT INVOLVE THE ENERGY-INTENSIVE, COSTLY CARBOTHERMAL REDUCTION. THE PHASE I PROJECT INVESTIGAGTES THE FEASBILITY OF THIS CHEMISTRY TO CREATE A HIGH PURITY SILICON RAW MATERIAL BY IDENTIFIYING APPROPRIATE NUCLEOPHILES TO EFFECT A ONE- OR TWO-STEP REDUCTION OF THE GLYCOLIC DIGESTION PRODUCT, AND BY IDENTIFYING PURIFICATION OPERATIONS ON PRECURSOR INTERMEDIATES. THIS PHASE CONCLUDES WITH A FEASIBILITY AND ECONOMICS STUDY FOR A PILOT-PLANT FACILITY. THE COST OF SILICON SOLAR PHOTOVOLTAIC CELLS IS LARGELY AFFECTED BY THE COST OF THE SILICON RAW MATERIAL. IF THE SILICON RAW MATERIAL CAN BE REDUCED FROM ITS CURRENT LEVEL OF $10 TO $15 PER KILOGRAM (BASED ON SCRAP SILICON FALL-OUT FROM THE ELECTRONICS INDUSTRY) TO $1 TO $2 PER KILOGRAM, A $3 PER PEAK WATT SOLAR CELL WOULD ACCORDINGLY DROP IN COST TO LESS THAN $1 PER PEAK WATT. AS THE CRYSTALLINE SILICON SOLAR CELL INDUSTRY GROWS INTO THE 10'S OF MEGAWATTS, THE DEMAND WILL EXCEED THE SUPPLY AVAILABLE FROM THE ELECTRONIC INDUSTRY, AND THE PRICE FOR THE SILICON RAW MATERIAL WILL INCREASE SUBSTANTIALLY. FURTHERMORE, AS THE PV INDUSTRY REACHES 1 GIGAWATT BY THE YEAR 2000, IT WILL NOT BE ABLE TO OBTAIN PURE SILICON FALL-OUT FROM THE ELECTRONICS INDUSTRY, WHOSE TOTAL USE OF SILICON RAW MATERIAL WAS EQUIVALENT TO ONLY 120 MEGAWATTS IN 1992. THIS NEW AND INNOVATIVE SUPPLY OF LOW-COST, HIGH-QUALITY SILICON CAN MEET THE GROWTH AND DEMAND OF THE CRYSTALLINE SILICON SOLAR CELL INDUSTRY.