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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."
Their scrap wafers turned into solar power should generate more power at a fraction of the cost.
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.
I think it's got more to do with the "energy debt" that silicon wafers acquire during their manufacture. Anything is better than starting from scratch.
They sentenced me to twenty years of boredom
"The silicon quality usually necessary for solar production"
apparently u couldn't even bother to RTFS
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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.
But what am I going to use for pellet gun targets now?
Seriously, a 1x2, slotted to hold wafers, A-framed, and backstopped by a heavy tarp fed to a 55 gal drum is the most awesome way to dispose of scrap wafers ever. We generate about 100 a year at my site and they pile up in 5 gallon buckets waiting to be sent to scrap, I just like helping along the process...
-nB
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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.
"the cost of solar panels reflects it" Slow day at the news desk.
However, it would more impressive if someone can recycle the waste of LCD substrate. The LCD generates huge amount of waste as well.
The purpose of writing is to inflate weak ideas, obscure poor reasoning, and inhibit clarity....Calvin
"Are those solar panels real??!! They're huge!"
"No way man, that's got to be silicon. There's no way it's natural."
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.
With Silicon you have the added problem that you want really big crystals since you do not want a grain boundary halfway across your electronic component. The wafers are cut from a single large crystal and it takes a lot of effort to grow this crystal. Silicon is very hard so cutting it into wafers is not that easy either.
I understand the process. But what is the actual quantity of energy required to make a square meter of PV? How many joules to produce a 15%, or for a 20%, or a 23%, or even the new (not just silicon) 42% PVs?
And how much is saved by using these IBM "scrubbed chips" instead of starting from scratch, for what %efficiency?
You say about 20% of the energy the PV will produce is consumed in construction and installation - 10% in manufacturing the silicon. A square meter of PV will last maybe 30 years, getting maybe an average (across weather/night/season/daytime) of 300W, for 248Gj. Does making the silicon really consume 25Gj? The rest of the deployment takes the equivalent of 193 gallons of 34Mj:L gasoline to deploy? Somehow that seems off by 10x or more. Do PV actually take more like only 1-2% of their lifetime output to deploy? And with this new IBM process, does recycling them at the end of their life mean grinding them back to sand, or some other energy input to return them to useful PV?
FWIW, even if the 20% number is correct, it sounds to me like we should be making and deploying these things in space, where there's vast energy to exploit, and probably the costs (including the deferred costs of "pollution" byproducts) are lower, once the process is in place. Considering the benefits (like 3-5x the reliable insolation, nearly unlimited capture area, and putting us firmly in profitable space industries poised for further exploitation), the investment in launching the "factories" seems like an excellent risk.
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make install -not war
The AC said "As the 8th most common element (by mass) in the Universe. Do we really need to worry about recycling?"
And for this he/she was modded Troll. That the AC missed the point that recycling the CPU wafers is about not wasting the effort and energy that went into creating them and is not about the abundance of unrefined silicon is most likely a simple careless mistake and there is no evidence to the contrary. Assuming that it's a deliberate troll attempt and wasting mod points that could have been used to promote the responses that corrected it, in my mind, says more about the moderator who did this than about the AC who was factually wrong (for whatever reason).
Why am I bothering to write this, knowing I will probably be modded down? Because I have noticed a decline in the quality of judgment calls made by some moderators (certainly not all and not most of them) and it tends to express itself in this way. Meta-moderating is great and I gladly do it every time it comes up, but if I meta-mod something as "Unfair" it does nothing to explain why I thought so. Moderating isn't supposed to be about kicking ass, it's more of a small way that we can contribute to a site that we enjoy reading, posting, and yes even trolling in order to make it a better place, but that's true only so long as we have that intention behind it.
It is a miracle that curiosity survives formal education. - Einstein
First you have to melt sand. Not cheese on a pizza, but sand
God damn it! No wonder my attempts have never worked. You have no idea how many different types of cheese I have tried...
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.
Another way to calculate it is about 777.6Kj:Kg, which is 18.624Gj for the 8" wafer, in the range of what we ran down.
I left out the only 20% efficiency solar -> DC conversion factor, so the cells I described produce only about 50Gj in their lifetime, or 37% total energy inefficiency from manufacturing. Seems like a lot.
I'm not sure we'd have to put the silicon into space. I saw reports of a NASA demo a few years ago of a lunar robot making solar cells from lunar dust. There's about 20 trillion square meters of Moon facing the Sun at any time, getting about 1.3KW:m^2, or 26 petawatts. Even at 1% conversion/transmission/conversion efficiency, that's 260TW, or 17x total human energy consumption. Which means well under 6%, perhaps even 0.6%, of the Moon's surface would replace all Earth power generation. Of course, orbiting solar platforms could offer even larger energy return. And consider the amount of energy wasted on war and fuel distribution that could be saved. If the space "factories" are productive enough, the energy budget balances well in favor of doing it.
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make install -not war
Aren't there ways to get solar power without futzing with photovoltaics?
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? Is this cheaper per watt of generating capacity to build?
Seems like if you did this on seawater (on a big barge or similar), you could extract the water once the steam recondensed and getting desalination for free. If desalination becomes necessary to supply freshwater this might be worth it.
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
I read on a book about a Germany based solar plate vendor produces their solar plates using the power generated from the solar plates they produced and installed outside their building. This is not a perfect solution. But better then totally rely on power generated from other not-green sources.
Sort of like bootstrapping solar power!
Is it any surprise that silicon, being so expensive to purify, would ultimately start to see at least some measure of waste recovery?