Erich Dornberger: Photovoltaics Will Become a Pillar of the Future Energy Supply
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Event Date: 
Fri, 03/30/2012 - 10:30am
Location: 
Towne Building, room 337

Special CBE Seminar
Photovoltaics Will Become a Pillar of the Future Energy Supply

Dr. Erich Dornberger,
Director, Application Engineering, Wacker Chemie AG
Burghausen, Germany

Abstract
Photovoltaic technology is still at the beginning of its development and is poised for enormous growth in the future.  Due to a fast decline of PV system prices and the levelized cost of electricity (LCOE) in the range of ~6-12  Ct/kWh, PV will be competitive with other Renewables (e.g. wind) and conventional power plants (e.g. gas) in the near future.  The PV market continues to be strongly dominated by crystalline silicon due to a better system cost structure compared to thin film technologies.  Made from high purity polycrystalline silicon, or polysilicon, crystalline silicon-based modules are now reaching efficiencies of up to 20%.  The energy needed to manufacture polysilicon-based modules has significantly decreased to around 1 year pay back time and the CO2 content of 1 kWh of PV electricity is only around 15 g (i.e. a factor of 40-60 below fossil-fuel power plants).

In this talk, I present an introduction to the manufacture of the polysilicon feedstock that is vital to this PV technology.  The large-scale manufacture of ultrapure polysilicon (99.9999999% purity) via the refining of 99% pure metallurgical grade silicon requires the application of chemical engineering principles from the first to the last production step.  Firstly, trichlorosilane is produced from finely ground metallurgical grade silicon and hydrogen-chloride in a fluidized bed reactor. After distillation, the trichlorosilane is decomposed in a reactor at about 1000°C and so-called “poly rods” are grown up to 200 mm in diameter.  Finally, the rods are crushed into “poly chips” with sizes varying from about 10 to 200 mm. 

I conclude by discussing the role of Wacker in the worldwide manufacture of polysilicon.  Today, the US is the home for the world’s largest polysilicon production capacities.  Wacker, as the worldwide No. 2 poly producer, is currently constructing an 18.000 mt polysilicon plant in Charleston, TN with production starting in 2013.