Sustainable Si production for solar cells a responsibility for Norway? (or how can Norway contribute to the PV industry in collaboration with China?) Gabriella Tranell, Associate Professor The Norwegian University of Science and Technology 1
USA, May 2009 Solar Energy What is driving the development globally? Federal government: $467 million to expand and accelerate the development and use of solar and geothermal energy China, July 2009 China announces plans to achieve a solar power capacity of 2 GW by 2011, nearly 15 times up from 2009 India, August 2009 Indian government announces goal of generating 20 GW of solar energy by 2020 2 Billion people still without access to electricity from the grid. 2
Foreseen growth in the PV market will most likely again bring increased demand of solar grade silicon.. Corresponds to ~176000 tons of SoG- Si or 241100 tons MG-Si* Source EPIA 2009 *100% csi, 2007 mc-si scenario, Jungbluth, Tuchschmid and de Wild-Scholten 3
Silicon in the solar cell production chain Silicon cost, availability and production method is critical to achieving competitive and sustainable solar electricity for the international community! Currently responsible for ~30% of total energy consumption and associated GHG emission in SC production chain 4
Silicon Silicon (Si) occurs in nature (earth) only in the oxidized state as quartz or other silicate minerals ( Si 4+ ). Any process aiming at elementary silicon (Si 0 ) involves necessarily some reduction steps Silicon is not a metal but a metalloid: this implies that efficient purification methods applied to metallic compounds are not always efficient when applied to silicon High purity is however requested for silicon to act as a semiconductor in photovoltaic cells 5
Routes Towards High Purity, SoG-Si (6N+ Purity) Raw Materials (C + SiO 2 ) MG-Si (Si = 98-99% ) SoG-Si 6N+ Siemens/FBR-Si 8-11N 6
Production of Si as Si or FeSi World Wide* US 3 % Others 22 % Si and FeSi production in 2006 Total volume 4700.000 tons China dominates the market Norway has worlds largest and most energy efficient furnace Brasil 5 % Norway 6 % China 51 % Russia 13 % Source: USGS * ~80% by weight of total is Si in FeSi. China produced ~550 kton of MG-Si. Numbers do not include ~150 kton Si from the US 7
The Industrial Carbothermic Process for MG-Si production 11-13MWh/ t Si Overall reaction: SiO2 + 2C Si + 2CO What do we need? - Raw materials - Electrical Energy 8
MG-Si Process Outputs Emissions: Electric Energy CO2 Fossile CO2 =4.3 t/t Si Biological CO2 = 1.8t/t Si SO2 = 13 kg/t Si NOx =11 kg/t Si Energy: Bi-product: 0,2-0,4 tons of SiO2/ ton Si Heat content of gas ~ electric energy added with current technology 30% may be recovered Product: Chemical composition of commercial MG silicon Too high for SoG-Si 9
Si production and CO2 emissions Electricity source Total spec. CO2 (kg CO2/kg Si) Hydro/Nuclear 4.3 Gas Power 10.6 Coal power 17.7 10
Polysilicon (TCS route) The Siemens process TCS (electronic grade) MG-Si Chemical Vapor Deposition HCl Production of TCS T 1100ºC T 300ºC Polysilicon Si + 3HCl HSiCl3 + H2 One or more fractional distillations H2 Recovery and HSiCl3 + H2 Si + 3HCl regeneration Energy consumption >120 MWh/t Chemical waste 11
So how does this relate to Norway and the solar industry? 12
Silicon-based solar energy and offshore wind in Norway Why? Natural Resource Water Falls Oil- and gas resources Industrial Utilisation Metallurgical industry Oil- and gas industry New Innovation Solar industry Offshore wind technology 13
PV industry in Norway Wafer-based technology REC Wafer Elkem Solar System REC Silicon Panel Metallurgical Chemical Cell/ Module Wafer Si (98%) Raw Materials SoG-Si REC Solar Norsun CruSiN Metallkraft Saint Gobain Wash. Mills Vetro Solar Norsk Solkraft Umoe Solar FeSil Sunergy Prediktor Innotech 14
The Elkem Solar Route Elkem Silicon Metal Pyro-metallurgical refining Hydro-metallurgical refining Elkem Silicon SiMet is ideal Commercial quality Available on site Pyro-metallurgical refining step Well known principles Large scale capability Run in industrial scale today Hydro-metallurgical refining step Well known principles No scale constrains Run in industrial scale today Final solidification refining step Well known principles Directional Solidification Final polishing Solar Grade Silicon Feedstock Status: In production. Ramping up towards targeted 3000t/year Can be used as blend or 100% mix good results in cell production 15
The Solsilc Process the Pure Raw Materials Route 7steps 1. Agglomeration of quartz, carbon black and SiC-fines 2. Silicon Carbide. Formation of silicon carbide (SiC) is an intermediate process in the reduction furnace. 3. Reduction. The charge is agglomerates made of quartz, SiC and carbon 4. Holding. Metal is tapped and processed 5. Filtering. With one or more filters 6. Casting/Directional Solidification 7. Clean and cut ingot Small scale test plant close to completion 16
CO2- and energy account for PV-Si kg CO2 og kwh/kg Si 200 180 CO2 160 kwh 140 120 100 80 60 40 20 0 Conventional Siemens Best Practice Europe Elkem Route Energy payback time now ~18 months, with UMG Si metal 2-4 months 17
Renewable energy storage and multiplication Hydrogen Carbon Energy Recovery! WOOD CO2-free Electricity Silicon Bio-carbon CO2 CCS Quartz 18 Solar cell materials for energy export, 20-40 x more energy produced than used!!
Challenges ahead Collaboration between China and Norway? Challenges/Opportunities Create trust and acceptance for non-siemens metal in the market; openness on specification, qualification Increased recovery of high- and low temperature heat/ chemical energy New reductants for better GHG emission performance Utilisation of waste products and raw materials fines Recycling of PV silicon from process and end-of-life 19
Energy efficient and environmentally friendly production of silicon is one of the keys to a robust solar energy future Norway and China are key players in this game and should join forces in competence development for global impact! The future's so bright, I gotta wear shades 20