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IBM Recycles Waste CPU Wafers Into Solar Panels
Luyseyal writes "IBM has developed a process for scrubbing waste silicon wafers clean, allowing the otherwise highly secret waste to be sold. The silicon quality usually necessary for solar production is very high and the cost of solar panels reflects it. Recycling this waste should help bring down the cost in the long run and add a new profit vector for chip manufacturers. The article notes that IBM has such a high profile in the chip business that this recycling tech should spread rapidly."
While most PV is currently constructed from wafer silicon, this is not a viable long-term strategy because it takes so much energy to make a wafer. To make real progress, PV needs to move to alternative technologies.
Engineering is the art of compromise.
That's a lot of heating that needs to be done very cleanly so uses electrical power which is far more wasteful than trying to get the same heat from a primary source (gas/oil etc).
No wonder PV has such long energy payback times and costs so much.
To get energy input (and thus $/watt too) to practical levels requires a change from wafer-based technology.
Engineering is the art of compromise.
It actually takes an enormous amount of energy to make solar (or IC) grade silicon. The estimates I have seen calculate that about 20% of the total energy produced by a typical crystalline silicon solar panel is necessary to construct and install the cell. Roughly half that energy is embedded in the silicon itself.
I disagree with the parent's parent post. There is no reason that silicon cells are not viable renewable energy sources. They produce five units of energy over the long haul for every one put in (excluding sunlight, of course!) - and that one could be renewable itself.
Silicon for IC and solar is so expensive and energy intensive because it must be so pure. To produce it, SiO2 (quartz, sand, etc) first reduced with carbon (similar to how iron oxide is made into iron). This requires lots of energy. This product, however, is crude. To purify it, it must be gassified to various chlorosilane molecules and then distilled (lots of energy in both steps). The highly pure gas species are again reduced to silicon metal and then recrystallized carefully to eliminate even more impurities...again, energy intensive. In most cases, these steps are undertaken at different facilities or companies, requiring shipment at each step as well.
As for recyling - it would be a matter of grinding the top off by whatever method is easiest (eg. Silicon carbide grinding and finer particles of the same to polish) to give you a single silicon crystal to turn into whatever you want it to be. In a lab progressively finer grades of normal sandpaper and a retail brass cleaner gets enough of a polish to see a mirror finish under a microscope at 400x.
To add an answer to somebody else's question here there are other methods like "sol-gel", the name actually somes from solution and not solar. This method for multi-crystalline coatings including some solar cell materials is effectively mixing up some goo in a bucket, painting it on and then heating it up in an oven. The solar materials made this way are not as effective but really cheap due to not needing very high temperatures to fabricate - you don't have to melt silicon.
25Gj for a panel comes out to a little under 2000 Kj/mol of silicon. That is a totally plausible number given the number of steps and high temperatures required (above 1000C in some phases). The other 10% is not just installation, but also includes wires, back-panels, sealents, etc.
Putting things into space is enormously energy intensive. You would never come out ahead unless you built a space elevator first. Unfortunately, no material known to man is strong enough to build one, not even in theory (carbon nanotubes fall just short in theory and far short in practice).
I watched a video once showing how processors are made. Hard to believe the highly polished and uniform wafers start out as a giant glass turd. All kidding aside, the video also showed all the waste produced. And with silicon being worth a billion dollars an acre, a little bit of payback would be appreciated by chip manufacturers. I'm sure.
The game.
Right. I heard the same thing from an Applied Materials VP.
Besides, the serious players in the solar business are now making solar cells five square meters at a time, using gear based on LCD panel fab technology. Solar panel production has gone way beyond using recycled IC wafers.
There's been commercial wafer recycling for years.
Hope IBM is not planning on patenting their method. This kind of thing has been studied already to understand the energy savings from recycling solar cells. Recycling solar cells requires about one third the energy of making new cells: http://www.solarworld.de/solarmaterial/english/press/8AV.3.14.pdf. And, basically, you scrape off what was on the waffer before and then start again. Note that in the link, they assume about 2.7 peak equivilent sun hours per day. A typical value for the US is 5 so that the energy payback time would be about 2 years for a new panel and 8 months for a recycled panel. For 40 years of use you get EROEIs of 20 and 60 for new and recycled respectively. But, you have to wait 40 years to start getting the cheaper deal ;-)
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Rent solar and save: http://mdsolar.blogspot.com/2007/01/slashdot-users-selling-solar.html
Look at the Stirling engine projects.
I don't read your sig. Why are you reading mine?
Yes, for example, see this press release about one particular company which builds "solar thermal" power plants:
http://www.ausra.com/news/releases/070927.html
Solar thermal systems have certain advantages over solar photovoltaic systems:
However, they have these disadvantages:
For more information:
http://en.wikipedia.org/wiki/Solar_thermal
http://www.ausra.com/technology/
What sort of efficiency can we get out of focusing sunlight on water (using cheap Fresnel lenses), making steam, and using it to turn a turbine?
You're talking power plants, now. Photovoltaics are good for rooftops, and when somebody has an acre of land they're not using somewhere. These are usually a lot closer to where the electricity is going to be used, so you save in transmission losses.
If you're just using the sunlight for heat, most of the newer projects use something other than water to collect heat, because they can get hotter, and may be able to store enough heat to keep producing electricity a while after the sun goes down.