1 Technology and raw materials for solar cell quality quartz Erik Larsen & Knut L. Sandvik Dept. of geology and mineral resources engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway

2 Solar cell market Average growth rate in the solar electric energy demand from was 22% per year [Year] [MW P ] Quartz demand: 2001: ~ tons 2010: ~ tons

3 Solar cell market - Crystalline cells: made from Si - Thin film cells: made from amorphous Si/CdTe/CuInGa diselenide - Other cells: electrochemical cells, organic cells, etc.. Thin film Monocrystalline Multicrystalline Other

4 Crystalline silicon solar cell production - Mainly quartzites and hydrothermal quartz - Little processing other than size reduction - Purity of quartz: typical 97-98% SiO 2 1) Mining and processing of raw materials (quartz + coke) 2) Carbothermic reduction to metallurgical-grade Si (MG-Si) 3) Purification of MG-Si to electronic-grade Si (EG-Si) 4) Production of silicon blocks from solar-grade Si (SoG-Si) 5) Wafer cutting and processing into wafers

5 Crystalline silicon solar cell production - Lump size material only ( mm) - MG-Si purity: typical 98.5% Si 1) Mining and processing of raw materials (quartz + coke) 2) Carbothermic reduction to metallurgical-grade Si (MG-Si) 3) Purification of MG-Si to electronic-grade Si (EG-Si) 4) Production of silicon blocks from solar-grade Si (SoG-Si) 5) Wafer cutting and processing into wafers Quartz + Carbon Carbothermic reduction RefiningMG-Si

6 Crystalline silicon solar cell production - Stream of by-products/waste - Highly energy consuming - EG-Si purity: ppb-ppt MG-Si + HCl Trichlorosilane (HSiCl 3 ) Purification of HSiCl 3 Deposition on Si rods EG-Si 1) Mining and processing of raw materials (quartz + coke) 2) Carbothermic reduction to metallurgical-grade Si (MG-Si) 3) Purification of MG-Si to electronic-grade Si (EG-Si) 4) Production of silicon blocks from solar-grade Si (SoG-Si) 5) Wafer cutting and processing into wafers

7 Crystalline silicon solar cell production EG-Si rejects + processing losses (SoG-Si) Growth (monocryst. Si) Casting (multicryst. Si) Si blocks - Highly energy consuming - Si purity: ppm-ppb 1) Mining and processing of raw materials (quartz + coke) 2) Carbothermic reduction to metallurgical-grade Si (MG-Si) 3) Purification of MG-Si to electronic-grade Si (EG-Si) 4) Production of silicon blocks from solar-grade Si (SoG-Si) 5) Wafer cutting and processing into wafers

8 Crystalline silicon solar cell production 1) Mining and processing of raw materials (quartz + coke) 2) Carbothermic reduction to metallurgical-grade Si (MG-Si) 3) Purification of MG-Si to electronic-grade Si (EG-Si) 4) Production of silicon blocks from solar-grade Si (SoG-Si) 5) Wafer cutting and processing into cells Wafer cuttingSi blocks Cut offSawing losses Cell processing To block prod.

9 Purity and price of materials Qtz MG-Si EG-Si SoG-Si Wafer 1 % 0.1 % 1 ppm 1 ppb 1 ppt ~ 0.05 $/kg ~ $/kg ~ $/kg [$/kg] ~ $/kg ~ $/kg 1.0

10 Crystalline Si cell production costs - Processing of primary raw materials: approximately 0.5% of total costs

11 Material impurities (ppm) A - Good quality lump quartz B - Processed hydrothermal quartz C - Processed pegmatite core quartz D - Hydrochemically treated quartz MG- Metallurgical grade UMG- Upgraded metallurgical grade SoG- Solar grade

12 Purity and price of quartz A B D C SoG-Si 1 ppm ~ 0.05 $/kg ~ $/kg ~ $/kg ~ $/kg ~ $/kg 1 % 0.1 % 0.01 % % A - Lump qtz (mainly quartzites) B - Processed qtz (normal pegmatite) C - Processed qtz (pegmatite core) D - Hydrochemically treated qtz

13 Current technology Mining & Processing Lump quartz MG-Si EG-Si SoG-Si Wafer Cell Module Carbothermic reduction Prod. of EG-Si Prod. of blocks Wafer sawing Prod. of cells & cell modules Block

14 Mining & Processing Lump quartz MG-Si EG-Si SoG-Si Wafer Cell Module Carbothermic reduction Prod. of EG-Si Prod. of blocks Wafer sawing Prod. of cells & cell modules - Over 50% of total costs - Very expencive materials Current technology Block

15 Mining & Processing Lump quartz MG-Si EG-Si SoG-Si Wafer Cell Module Carbothermic reduction Prod. of EG-Si Prod. of blocks Wafer sawing Prod. of cells & cell modules - Almost 50% loss - Recycling required Current technology Block

16 Mining & Processing Lump quartz MG-Si EG-Si SoG-Si Wafer Cell Module Carbothermic reduction Prod. of EG-Si Prod. of blocks Wafer sawing Prod. of cells & cell modules - Approximately 30% of total costs - Highly energy consuming Current technology Block

17 Mining & Processing Lump quartz MG-Si EG-Si SoG-Si Wafer Cell Module Carbothermic reduction Prod. of EG-Si Prod. of blocks Wafer sawing Prod. of cells & cell modules - Approximately 10% of total costs - Highly energy consuming - Limited availability - Unnecessary pure Current technology Block

18 Mining & Processing Lump quartz MG-Si EG-Si SoG-Si Wafer Cell Module Carbothermic reduction Prod. of EG-Si Prod. of blocks Wafer sawing Prod. of cells & cell modules - Approximately 3% of total costs - Impure raw materials - Can not be refined to SoG-Si quality Current technology Block

19 Mining & Processing Lump quartz MG-Si EG-Si SoG-Si Wafer Cell Module Carbothermic reduction Prod. of EG-Si Prod. of blocks Wafer sawing Prod. of cells & cell modules - Less than 0.5% of total costs - Few high-grade deposits - No processing due to requirements Current technology Block

20 Electrolysis / plasma techn. Quartz powder Mining & Processing - Mineral processing - Electrolysis / plasma metallurgy - Purification combined with crystallisation Future SoG-Si route Mining & Processing Lump quartz MG-Si EG-Si SoG-Si Wafer Cell Module Carbothermic reduction Prod. of EG-Si Prod. of blocks Wafer sawing Prod. of cells & cell modules Block

21 Processed quartz Mining & Processing - Mineral processing - Electrolysis / plasma metallurgy - Purification combined with crystallisation Future SoG-Si route SoG-Si Block Wafer Cell Module Wafer sawing Prod. of cells & cell modules Electrolysis / plasma techn. Prod. of blocks

22 Conclusion

23 Conclusion TODAY FUTURE