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Monday, January 28, 2008

RSI Silicon: Solar Grade Silicon from Pennsylvania (then Alabama)

Novel process begins with a Sodium Silicate (Na2SiO3) precursor in solution.
The complete production process patent has been published by WIPO.
RSI Silicon claims Solar Grade Silicon production will start in Q2 2008 with 1000 metric ton annual capacity.

RSI (Reaction Sciences, Inc.) Silicon is commercializing a process for six nines (6N) or 99.9999+% pure solar grade silicon that does not require metallurgical silicon (mg-Si) as in an input. Proven polysilicon and solar grade silicon production processes all share metallurgical silicon as a feedstock including the Siemens, Fluidized Bed Reactor, and upgraded metallurgical processes.

After noticing a recent increase in traffic and interest regarding Easton, Pennsylvania USA, based RSI Silicon, I redoubled my efforts to research and establish a dialog with the company.

Since a small blurb I wrote in Solar Light Flashes: November 15, 2007, RSI Silicon has corrected (or scaled back?) their initial pilot line production plans in 2008 from 5000 to 1000 metric tons.

Dr. Steve Amendola, along with his experienced team, has commenced building the first plant. It is envisaged that production at the 1,000 metric tonne (bold added) per annum plant based in Northampton County, Pennsylvania, will commence Q2 2008.

In an apparent new development, the RSI Silicon website details ambitious expansion plans:

RSI anticipates completing a new plant in Alabama in 2009 that will have a production capacity of 24,000 metric tonnes per annum, adding a new 5,000 tonne furnace in 2010 and 2011.

First, for the impatient, here is the key Reaction Sciences, Inc., international patent published by the World Intellectual Property Organization (WIPO):


A method for preparation of high purity silicon suitable for photovoltaic cells using reduction of silica, which is pre-purified in an aqueous solution, in presence of a reducing agent, preferably carbonaceous agent, where the pre-purified silica has a low amount of boron suitable for photovoltaic cells is described.

RSI Silicon’s production process for solar grade silicon can be outlined in simplified form as follows. I’ve left out the addition of sulfuric acid to adjust pH, details about the steps, and optional steps for clarity.

  • Sodium silicate (Na2SiO3) is dissolved in deionized water to create an aqueous solution for chemical processing into high purity silica (SiO2).
  • The solution is filtered to remove insoluble materials including most of the phosphorus by first adding calcium or magnesium to the solution.
  • Boron is removed using a chelating agent such as AMBERLITE IRA734, an ion exchange resin. RSI Silicon’s tests and projections indicate Boron levels of 0.1ppm or lower after this step.
  • After being allowed to stand, a pure silica gel precipitates and is filtered and dried at up to 1400 °C (degrees Celsius). The silica is crystallized into briquette form.
  • In the final step, the same Carbothermic Reduction process, used to produce metallurgical silicon in a submerged arc furnace and described in Solar Grade Silicon roads lead to Ruše - Part 2, separates the oxygen from the pure silica (SiO2) to yield the Solar Grade Silicon.

There are two similarities to the Solarvalue AG process. Both methods begin with high purity inputs. RSI Silicon uses a chemical process to produce higher purity silica than any natural quartz. Like Solarvalue, RSI Silicon requires high purity carbon for the Carbothermic Reduction process to avoid contaminating the purified silica. However, RSI Silicon is even concerned about tapping the arc furnace in air and specifies the silicon be cooled in an inert gas atmosphere such as argon or helium.

RSI Silicon has not acknowledged my requests for an interview. Because of inconsistencies on the RSI Silicon website, I would like to reconfirm this company’s schedules and plans.

At the H&R Block digits community site, the Macworld post has a slideshow (slide 10 et al.) capturing the Photovoltaic Blogger enjoying a Blog and Brew and includes a link to my Going SOLIO at Macworld 2008 post.



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