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					    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
1
    Solar cell market
    [MWP]
    2500

    2000

    1500

    1000

     500

      0
      1985       1990     1995     2000     2005    2010    2015   [Year]


            Average growth rate in        Quartz demand:
            the solar electric energy     2001: ~ 65 000 tons
            demand from 1990-2001         2010: ~ 350 000 tons
            was 22% per year

2
    Solar cell market

    100 %
                          Other          Thin film
    80 %
                                         Multicrystalline
    60 %

    40 %
                                         Monocrystalline
    20 %

     0%
       1980        1984           1988   1992        1996      2000

     - Crystalline cells: made from Si
     - Thin film cells: made from amorphous Si/CdTe/CuInGa diselenide
     - Other cells: electrochemical cells, organic cells, etc..


3
    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 wafers




    - Mainly quartzites and hydrothermal quartz
    - Little processing other than size reduction
    - Purity of quartz: typical 97-98% SiO2
4
    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 wafers




         Quartz +            Carbothermic
                                                       Refining    MG-Si
         Carbon               reduction




    - Lump size material only (10-150 mm)
    - MG-Si purity: typical 98.5% Si




5
    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 wafers



        MG-Si +              Trichlorosilane                 Purification of
         HCl                     (HSiCl3)                        HSiCl3




                                                            Deposition on Si
                                         EG-Si
                                                                 rods



    - Stream of by-products/waste
    - Highly energy consuming
    - EG-Si purity: ppb-ppt
6
    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 wafers



                                               Growth
                                            (monocryst. Si)

           EG-Si rejects +
          processing losses                                       Si blocks
              (SoG-Si)

                                              Casting
                                           (multicryst. Si)


    - Highly energy consuming
    - Si purity: ppm-ppb

7
    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



         Si blocks              Wafer cutting                Cell processing



          Cut off              Sawing losses
                                                              To block prod.




8
     Purity and price of materials

    1 ppt
                                                    ~ 50 - 60 $/kg
                                                      EG-Si


    1 ppb
                                                                    ~ 200 - 230 $/kg
                                                                      Wafer

    1 ppm                                        SoG-Si
                                             ~ 25 - 30 $/kg



     0.1 %                 ~ 1 - 1.5 $/kg
             ~ 0.05 $/kg
      1%                     MG-Si
             Qtz

               0.1            1.0           10                100               1000   [$/kg]
9
     Crystalline Si cell production costs



                                                                     Qtz + C
                                                      67 %
                                                                     MG-Si
         55 %           45 %
                                             25 %
                                                                     SoG-Si

                                                 7%                  Wafer prod.

                                                    1%


       CELL MODULE        WAFER


     - Processing of primary raw materials: approximately 0.5% of total costs


10
          Material impurities (ppm)
                              Quartz                          Silicon metal
               A          B            C        D        MG        UMG      SoG
     B                        <1                <0.04     15-50       <30      <1
     P              <5        0.2         <5     0.05     10-50       <15      <5
     Fe            600         15        0.1    <0.03      2000      <150     <10
     Al            400         30          7        7   100-200       <50      <2
     Ca            150         15        0.1      0.5   100-600      <500      <2
     Ti             30        1.2          4      1.2       200        <5       1
     Cr             15        2-5      <0.01   <0.003        50       <15       1

     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
11
       Purity and price of quartz


     1 ppm                                            SoG-Si ~25 - 30 $/kg

                                     D ~ 1.5 - 2.5 $/kg
     0.001 %


                           C ~ 0.4 - 0.6 $/kg
      0.01 %



      0.1 %
                    B ~ 0.1 - 0.2 $/kg
                                                A - Lump qtz (mainly quartzites)
        1%                                      B - Processed qtz (normal pegmatite)
                                                C - Processed qtz (pegmatite core)
               A ~ 0.05 $/kg
                                                D - Hydrochemically treated qtz


12
      Current technology


      Prod. of cells    Cell
     & cell modules    Module



         Wafer



                                  Prod. of
     Wafer sawing      Block      blocks
                                               SoG-Si



                                               Prod. of
                                                EG-Si
                                                          EG-Si



       Mining &        Lump     Carbothermic
      Processing                  reduction
                                               MG-Si
                       quartz
13
      Current technology


      Prod. of cells    Cell       - Over 50% of total costs
     & cell modules    Module      - Very expencive materials



         Wafer



                                  Prod. of
     Wafer sawing      Block      blocks
                                                  SoG-Si



                                                 Prod. of
                                                  EG-Si
                                                                EG-Si



       Mining &        Lump     Carbothermic
      Processing                  reduction
                                                  MG-Si
                       quartz
14
      Current technology


      Prod. of cells    Cell       - Almost 50% loss
     & cell modules    Module      - Recycling required



         Wafer



                                  Prod. of
     Wafer sawing      Block      blocks
                                                  SoG-Si



                                                 Prod. of
                                                  EG-Si
                                                            EG-Si



       Mining &        Lump     Carbothermic
      Processing                  reduction
                                                  MG-Si
                       quartz
15
      Current technology


      Prod. of cells    Cell       - Approximately 30% of total costs
     & cell modules    Module      - Highly energy consuming



         Wafer



                                  Prod. of
     Wafer sawing      Block      blocks
                                                  SoG-Si



                                                 Prod. of
                                                  EG-Si
                                                                   EG-Si



       Mining &        Lump     Carbothermic
      Processing                  reduction
                                                  MG-Si
                       quartz
16
      Current technology


      Prod. of cells    Cell       - Approximately 10% of total costs
     & cell modules    Module      - Highly energy consuming
                                   - Limited availability
                                   - Unnecessary pure
         Wafer



                                  Prod. of
     Wafer sawing      Block      blocks
                                                  SoG-Si



                                                 Prod. of
                                                  EG-Si
                                                                   EG-Si



       Mining &        Lump     Carbothermic
      Processing                  reduction
                                                  MG-Si
                       quartz
17
      Current technology


      Prod. of cells    Cell       - Approximately 3% of total costs
     & cell modules    Module      - Impure raw materials
                                   - Can not be refined to SoG-Si quality


         Wafer



                                  Prod. of
     Wafer sawing      Block      blocks
                                                  SoG-Si



                                                  Prod. of
                                                   EG-Si
                                                                    EG-Si



       Mining &        Lump     Carbothermic
      Processing                  reduction
                                                   MG-Si
                       quartz
18
      Current technology


      Prod. of cells    Cell       - Less than 0.5% of total costs
     & cell modules    Module      - Few high-grade deposits
                                   - No processing due to requirements


         Wafer



                                  Prod. of
     Wafer sawing      Block      blocks
                                                 SoG-Si



                                                 Prod. of
                                                  EG-Si
                                                                  EG-Si



       Mining &        Lump     Carbothermic
      Processing                  reduction
                                                  MG-Si
                       quartz
19
      Future SoG-Si route


      Prod. of cells    Cell    - Mineral processing
     & cell modules    Module   - Electrolysis / plasma metallurgy
                                - Purification combined with crystallisation


         Wafer



                                   Prod. of
     Wafer sawing      Block       blocks
                                                    SoG-Si



                                                    Prod. of
                                                     EG-Si
                                                                      EG-Si



       Mining &         Lump
                       Quartz   Electrolysis /
                                Carbothermic
      Processing                plasma techn.
                                   reduction
                                                    MG-Si
                       quartz
                       powder
20
      Future SoG-Si route


      Prod. of cells     Cell      - Mineral processing
     & cell modules     Module     - Electrolysis / plasma metallurgy
                                   - Purification combined with crystallisation


         Wafer



                                      Prod. of
     Wafer sawing       Block         blocks




                                      SoG-Si



       Mining &        Processed   Electrolysis /
      Processing         quartz    plasma techn.
21
     Conclusion


                                              Qtz
                                       74 %

       55 %         45 %                      SoG-Si
                             16 %

                                10 %          Wafer prod.




      CELL MODULE    WAFER




22
     Conclusion
                  TODAY




                  FUTURE




23

				
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