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Technology and raw materials forsolar cell quality quartz

Erik Larsen & Knut L. SandvikDept. of geology and mineral resources engineering,

Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway

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Solar cell market

Average growth rate in the solar electric energy demand from 1990-2001 was 22% per year

[Year]

[MWP]

Quartz demand:2001: ~ 65 000 tons2010: ~ 350 000 tons

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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

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Crystalline silicon solar cell production

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

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

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Crystalline silicon solar cell production

- Lump size material only (10-150 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

Refining MG-Si

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Crystalline silicon solar cell production

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

MG-Si + HCl

Trichlorosilane (HSiCl3)

Purification of HSiCl3

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

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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

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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 off Sawing losses

Cell processing

To block prod.

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Purity and price of materials

QtzMG-Si

EG-Si

SoG-Si

Wafer

1 %

0.1 %

1 ppm

1 ppb

1 ppt

~ 0.05 $/kg~ 1 - 1.5 $/kg

~ 25 - 30 $/kg

0.1 10 100 1000 [$/kg]

~ 50 - 60 $/kg

~ 200 - 230 $/kg

1.0

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Crystalline Si cell production costs

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

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Material impurities (ppm)

A - Good quality lump quartzB - Processed hydrothermal quartzC - Processed pegmatite core quartzD - Hydrochemically treated quartz

MG - Metallurgical gradeUMG - Upgraded metallurgical gradeSoG - Solar grade

A B C D MG UMG SoGB <1 <0.04 15-50 <30 <1P <5 0.2 <5 0.05 10-50 <15 <5Fe 600 15 0.1 <0.03 2000 <150 <10Al 400 30 7 7 100-200 <50 <2Ca 150 15 0.1 0.5 100-600 <500 <2Ti 30 1.2 4 1.2 200 <5 1Cr 15 2-5 <0.01 <0.003 50 <15 1

Quartz Silicon metal

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Purity and price of quartz

A

B

D

C

SoG-Si1 ppm

~ 0.05 $/kg

~ 0.1 - 0.2 $/kg

~ 0.4 - 0.6 $/kg

~ 1.5 - 2.5 $/kg

~25 - 30 $/kg

1 %

0.1 %

0.01 %

0.001 %

A - Lump qtz (mainly quartzites)B - Processed qtz (normal pegmatite)C - Processed qtz (pegmatite core)D - Hydrochemically treated qtz

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Current technology

Mining & Processing

Lump quartz

MG-Si

EG-Si

SoG-Si

Wafer

Cell Module

Carbothermic reduction

Prod. of EG-Si

Prod. ofblocks

Wafer sawing

Prod. of cells& cell modulesProd. of cells

& cell modules

Block

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Mining & Processing

Lump quartz

MG-Si

EG-Si

SoG-Si

Wafer

Cell Module

Carbothermic reduction

Prod. of EG-Si

Prod. ofblocks

Wafer sawing

Prod. of cells& cell modulesProd. of cells

& cell modules- Over 50% of total costs- Very expencive materials

Current technology

Block

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Mining & Processing

Lump quartz

MG-Si

EG-Si

SoG-Si

Wafer

Cell Module

Carbothermic reduction

Prod. of EG-Si

Prod. ofblocks

Wafer sawing

Prod. of cells& cell modulesProd. of cells

& cell modules- Almost 50% loss- Recycling required

Current technology

Block

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Mining & Processing

Lump quartz

MG-Si

EG-Si

SoG-Si

Wafer

Cell Module

Carbothermic reduction

Prod. of EG-Si

Prod. ofblocks

Wafer sawing

Prod. of cells& cell modulesProd. of cells

& cell modules- Approximately 30% of total costs - Highly energy consuming

Current technology

Block

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Mining & Processing

Lump quartz

MG-Si

EG-Si

SoG-Si

Wafer

Cell Module

Carbothermic reduction

Prod. of EG-Si

Prod. ofblocks

Wafer sawing

Prod. of cells& cell modulesProd. of cells

& cell modules- Approximately 10% of total costs - Highly energy consuming- Limited availability- Unnecessary pure

Current technology

Block

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Mining & Processing

Lump quartz

MG-Si

EG-Si

SoG-Si

Wafer

Cell Module

Carbothermic reduction

Prod. of EG-Si

Prod. ofblocks

Wafer sawing

Prod. of cells& cell modulesProd. of cells

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

Current technology

Block

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Mining & Processing

Lump quartz

MG-Si

EG-Si

SoG-Si

Wafer

Cell Module

Carbothermic reduction

Prod. of EG-Si

Prod. ofblocks

Wafer sawing

Prod. of cells& cell modulesProd. of cells

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

Current technology

Block

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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. ofblocks

Wafer sawing

Prod. of cells& cell modulesProd. of cells

& cell modules

Block

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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 modulesProd. of cells

& cell modules

Electrolysis /plasma techn.

Prod. ofblocks

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Conclusion

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ConclusionTODAY

FUTURE