Solar Breakthrough: Dow Corning's PV1101
By Bill Moore
Dow Corning calls it PV1101. It's not polysilicon. It's not metallurgical grade silicon. It's something in between and its just what the crystalline silicon solar industry has been needing for a long, long time.
What's this mean to you and me? To find out, EV World talked with the director of Dow Corning's solar products division, Gaetan Borgers. What we learned won't immediately change our lives, but it is likely to have important consequences in coming decades as the demand for photovoltaic cells continues to grow.
We began by talking about Dow Corning's long history in producing products for the solar industry including the silicone sealers used to assembly solar panels. The company also has a significant investment in Hemlock Semiconductor, the world's largest producer of polysilicon. The announcement of PV1101on which Dow Corning Solar has been working on for the last five years, marks the company's direct entrance into the solar cell feedstock business.
To understand the significance of PV1101, you need to know how we get from "sand" to solar cells. The process begins by refining quartzite, a type of sand, into 98.5% pure silicon called metallurgical-grade silicon. This requires a lot of energy and is produced in large quantities around the world, mainly for the steel-making industry. Known as mg silicon, it is the primary feedstock for making silicon wafers used in both the computer chip and solar wafer industries.
The next step in making photovoltaic cells is to further refine mg silicon into ultra-pure, nine nines silicon called polysilicon that is 99.9999999 percent pure. And here is where PV1101 becomes important for a couple reasons. Because most of the world's polysilicon has been used for the computer chip industry, it has to be extraordinarily pure, which makes it very expensive.
Historically, solar wafer manufacturers have relied on the cast-off waste of the silicon ingot industry to save costs, but with the growth of the photovoltaic solar industry -- now using as much polysilicon as the computer chip industry -- all of the waste silicon is now spoken for. This means the solar industry is paying as much for crystalline silicon as computer chip makers, which can generate significantly more profit from a single wafer than their PV counterparts. And because of the global demand for solar panels, driven largely by an aggressive renewable energy policy in Germany, there is now a severe shortage of polysilicon, which has stalled the steady decline in the price per watt cost of solar PV.
What is needed is additional polysilicon that is tailored not for computer chip makers, but for the solar industry, which doesn't need the same level of purity. This is where PV1101 comes in. Manufactured at a Dow Corning pilot plant in Brazil, PV1101 is designed specifically for the solar PV industry who can use it as a lower-cost polysilicon extender that can be mixed to whatever level of purity the wafer manufacture desires, depending on the needs of their customers.
Borgers would not reveal the exact ratio at which PV1101 would be blended with the computer-grade polysilicon because, in part, it will vary from customer to customer and also because of non-disclosure agreements with the customers, though he did say it would be somewhere below 50 percent.
Borger pointed out that while PV1101 won't solve the shortage of polysilicon, especially since the plant in Brazil will only be able to make about 1,000 metric tons annually in its start-up phase. In 2005, the industry consumed some 32,000 metric tons of polysilicon. The plant can ultimately produce between 3-4,000 metric tons.
Also because this is a new process in start-up production stage, he couldn't talk about what kind of cost savings would be realized by the manufacturer by supplementing with PV1101. DoE studies in the late 70s and early 80s, however, indicated that the price needed to be around $10/kg to be competitive. At the moment polysilicon is going for upwards of $50-60/kg, if you can even get it. On the spot market, it's selling for upwards to $200/kg. Right now, the industry is happy to get whatever it can to make up the shortage. Some wafer production facilities in China, for example, are only running at half their capacity.
While efforts are underway to build more polysilicon capacity to meet the current shortage, Borgers is of the belief that supplies will continue to be constrained into the immediate future. He pointed to an industry study that shows demand for PV cells in 2006 is 5 gigawatts. Yet the industry is only able to manufacture between 2.5-2.8 gigawatts this year. Although some believe new capacity coming on line in 2008-2010 will satisfy demand for polysilicon, that is by no means a universal consensus within the industry.
Borgers told EV World that even by 2010, Dow Corning Solar believes it will still be difficult for the industry to meet the demand for polysilicon, even with the ramp up of PV1101, which he noted already is completely sold out well into the future.
What about other solar technologies like thin film and organic solar? They will continue to grow, absorbing more market share, but crystalline silicon (C-si) will continue to be the dominate player for decades to come. Projections see C-si still holding on to 80-85% of market share by 2020, down from its present 95% share.
As to the potential size of the industry, I asked Borgers about a new report out of Europe that foresees as many as 2 billion people enjoying the benefits of solar electricity by the 2020's. He thinks that's a very ambitious goal that will require continued price-per-watt cost reductions to make it competitive with central grid power. The cost problem is directly related to the availability of low-cost feedstock, which PV1101 hopes to help address.
Finally, Gaetan agreed that proactive government policy such as that in Germany and Spain is equally important in helping pull the industry along, though everyone recognizes ultimately the industry has to stand on its own in the competitive energy marketplace.
He stressed in conclusion that Dow Corning is firmly committed to the solar PV industry and is planning to increase its capacity to produce PV1101 as soon as possible.
For more details on solar cell manufacturing and PV1101, be sure to listen to all of the 28:30 minute-long interview using either of the two MP3 players incorporated into the right-hand column of this page. Or, if you prefer, you can download the file for later playback on your favorite MP3 device. The download URL is: http://www.evworld.com/evworld_audio/gaetan_borgers.mp3.