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Power IBM Hardware

IBM Recycles Waste CPU Wafers Into Solar Panels 122

Posted by kdawson from the trash-to-power-revisited dept.
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."
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IBM Recycles Waste CPU Wafers Into Solar Panels More

IBM Recycles Waste CPU Wafers Into Solar Panels

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  • As the 8th Most Common Element (by Mass)... (Score:1, Insightful)

    by Anonymous Coward
    in the Universe. Do we really need to worry about recycling?

    http://en.wikipedia.org/wiki/Silicon [wikipedia.org]

    • Re:As the 8th Most Common Element (by Mass)... (Score:5, Insightful)

      by dwywit ( 1109409 ) on Tuesday October 30, 2007 @09:19PM (#21179199)
      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.

      • Re:As the 8th Most Common Element (by Mass)... (Score:5, Insightful)

        by Mark_MF-WN ( 678030 ) on Wednesday October 31, 2007 @01:35AM (#21180407)
        I remember reading about how the entire concept of "recycling" started with aluminum -- because the difference between refining new aluminum from bauxite and reprocessing existing aluminum is so incredibly great. Even iron is recycled to an extraordinary degree. And they say that 99% of all the gold that has ever been mined is still in use. There are even a few companies that believe that they can profitably recover platinum from the dust on America's highways left behind by catalytic converters!

        Is it any surprise that silicon, being so expensive to purify, would ultimately start to see at least some measure of waste recovery?

        • I imagine that when it gets doped it's very difficult to un-dope. I guess that's why the silicon is only being used in photovoltaic cells and isn't suitable to be made into new chips, but I'm a layman.
          • I don't think doping generally goes all that deep, you can probablly get rid of most of it by stripping back the surface with a suitable chemical.

        • Re: (Score:1)

          by ajs318 ( 655362 )
          Yes -- aluminium is made from bauxite by electrolysis of the molten ore. This consumes riduculous amounts of electricity. Extracting 50kg. of aluminium from ore -- that's enough for about 3000 * 330ml coke cans -- uses as much energy as melting down a whole tonne of used aluminium.

          One of the cool ways of recycling steel is in an electric arc furnace. You jump an arc from a carbon electrode to the pile of scrap steel, and of course it becomes a puddle. But there's more! Shine the light through a prism

    • Re: (Score:2, Insightful)

      by weirdcrashingnoises ( 1151951 )
      "The silicon quality usually necessary for solar production"

      apparently u couldn't even bother to RTFS
    • 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 be

      • 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)...

        ...

        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...

        There are more trolls moderating... than there are posting. Just

        • There are more trolls moderating... than there are posting. Just keep that in mind. No-nonsense honest bare-naked opinions are not rewarded here, but compliance to the homogenized baseline is.

          The thing about that, is that there is no homogenized baseline unless people choose to comply with it, so the antidote to that is clear.

          I also think a big part of that problem is that people no longer seem to understand that when you read a book, an article, or a Slashdot post, you are reading the perspective of i

  • I'll wait for AMD to do this (Score:5, Funny)

    by Anonymous Coward on Tuesday October 30, 2007 @09:10PM (#21179133)
    Their scrap wafers turned into solar power should generate more power at a fraction of the cost.

    • Re: (Score:1, Funny)

      by Anonymous Coward
      It'll take Sun to do it right.
    • 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.

  • Silicon wafers are not the answer for longterm PV (Score:5, Informative)

    by EmbeddedJanitor ( 597831 ) on Tuesday October 30, 2007 @09:11PM (#21179139)
    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.
    • How much energy does it take to make a PV wafer, per usable area? Not including what it takes to deliver and install (and later recycle) it?

      • Re:How Much? (Score:5, Informative)

        by EmbeddedJanitor ( 597831 ) on Tuesday October 30, 2007 @09:38PM (#21179325)
        To give you an idea... First you have to melt sand. Not cheese on a pizza, but sand.... then keep in melted while building up the silicon boule which takes a good long time. Then you cut it into wafers and a lot of the material gets lost in the kerf. Then there is doping where the wafers need to be kept at very high temperatures for many hours while the dopants get absorbed into the wafers...

        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.

        • 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? That makes discussions of the PV energy budget actually tractable, instead of just speculations about whether the breakeven is met.

          And how much is saved by using these IBM "scrubbed chips" instead of starting from scratch, for what %efficiency?
          • I don't think there are any easy answers due to different processes required to make different grade silicon and for other differences too (strenght, temperature etc). The crap they put into solar calculators etc could be made on a barbeque at home (well almost). Different doping levels require different amounts of baking and highly uniform doping requires doing it slowly.

            Waste wafers get you past the boule stage. You'd need to redope them though.

          • Re: (Score:2)

            by dbIII ( 701233 )

            instead of just speculations about whether the breakeven is met.

            The breakeven thing is a bit of a distraction since it is no longer 1960 - the time to break even would vary depending on the process and lattitude where you use the things. I don't have any numbers on this, it needs a bit more than what is in the textbooks but in short the wide use of semiconductors resulted in it being worth making even small improvements to save a lot of energy and money.

          • Prior Art (Score:4, Informative)

            by mdsolar ( 1045926 ) on Wednesday October 31, 2007 @12:20AM (#21180145) Homepage Journal
            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 [solarworld.de]. 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 ;-)
            --
            Rent solar and save: http://mdsolar.blogspot.com/2007/01/slashdot-users-selling-solar.html [blogspot.com]
            • Is "peak equivalent Sun hours per day" a way of combining the average insolation (across weather/night/seasons/azimuth) into the number of equivalent hours at solar noon? Where can I find those ratings for various places on the Earth, and country/state averages?
              • That is just right. Usually figures are given for tracking concentrators or latitude tilt panels. You can find US maps here: http://www.nrel.gov/gis/solar.html [nrel.gov]. The units are in kWh/m^2/day which I divide by a kW/m^2 to get hours per day. You'll notice that in New York, panels do better than tracking concentrators. This is owing to clouds being a bigger problem for concentrators. Tracking panels should do better than latitude tip panels though by something close to but not quite the fraction that trac

        • Re:How Much? (Score:5, Funny)

          by sholden ( 12227 ) on Tuesday October 30, 2007 @10:31PM (#21179641) Homepage
          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...

        • Re: (Score:1, Redundant)

          by Cecil ( 37810 )
          To get energy input (and thus $/watt too) to practical levels requires a change from wafer-based technology.

          No, it just requires a more efficient way to heat things to tremendous temperatures. Solar concentrators may come in handy for this purpose in the future, but at the very least they could build a solar panel farm next to the solar panel factory and use the energy directly in their current processes, which would be much more efficient.

        • Re: (Score:1)

          by cats-paw ( 34890 )

          Truly. Energy efficiency in solar cell production is a good thing. There are some companies which are attempting to be more efficient.

          Evergreen Solar [evergreensolar.com]

          Their production method is not wafer based. Much more efficient in both energy and material, in spite of the fact that they grow the ribbons in mid-air ! Be sure and watch the video on their site, it's fun.

        • Why not use the heat of the sun concentrated by mirrors to heat the sand and produce the silicon wafers? Wouldn't it be 100% renewable then?

        • Re: (Score:1)

          by johndr ( 109432 )
          It is actually much worse than that.

          After cooking silicon dioxide (sand) with carbon, the silicon has to be reacted with hydrogen chloride to form dichlorosilane. The dichlorosilane is distilled to purify it. This process is not too energy intensive as the boiling point of dichlorosilane is near room temperature. Then the dichlorosilane is decomposed at high temperature onto huge mandrels, another highly energy intensive step. The polysilicon this produces is melted again and the single crystal silicon

        • 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).

          That's only true with the old, basic, resistive heating elements. Using (electric-powered) heat pumps can easily give you far more heat from than directly burning the equivalent amount of fuel.

      • Re:How Much? (Score:5, Informative)

        by Ogemaniac ( 841129 ) on Tuesday October 30, 2007 @09:40PM (#21179341)
        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.

        • Re: (Score:2)

          by Average ( 648 )
          One factor that may make a difference is that power at point A is not equivalent to power at point B. The places where power is ultra-cheap tend to export it in the form of manufactured products (i.e., the Columbia River historically being a cheap place to refine Aluminium lead Boeing in Seattle). If energy were somewhat more expensive, something that is net Energy-Return-on-Energy-Invested positive (making solar cells) will be even more net-positive in a cheap energy climate.
          • not if the anti globalisation cults have their way. ironic considering they are one and the same with movements like greenpeace and other global warming sub cults.
            • You presume to much. The transportation cost for moving coal to a power plant is 200 times higher for the amount of energy produced than the transportation cost of taking a solar panel from a factory to your roof. Solar beat nuclear in this measure as well if you consider that uranium is mined in Austraia and enriched in France. Of course it makes sense to make panels where there is hydro power. But, there is hydro power in a lot of places so why the globalization jab? Shipping solar panels a long way

        • Re: (Score:3, Insightful)

          by Doc Ruby ( 173196 )
          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 may

          • Re: (Score:3, Informative)

            by Ogemaniac ( 841129 )
            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 (c

            • Re:How Much? (Score:5, Interesting)

              by Doc Ruby ( 173196 ) on Tuesday October 30, 2007 @11:00PM (#21179773) Homepage Journal
              Another way to calculate it is about 777.6Kj:Kg [slashdot.org], 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.

            • Re: (Score:1)

              by IdeaMan ( 216340 )
              A NASA funded study during the 70's came back with the conclusion that it would certainly be profitable to build an SPS. Given our rising energy costs, it would seem even easier now, except for the prohibitively expensive launch costs. The current space competitions may change the launch situation.
              One interesting thing about a space elevator is that you Don't have to go all the way from geo to ground. You could build a chain of them in different orbits. This should enable us to use non-theoretical mate

        • Re: (Score:2)

          by dbIII ( 701233 )
          First I'll say that it is very true that it is a lot of energy but the part below I have to dispute and ask where it came from:

          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

          What year was this written? What estimate did they have for the lifetime of the cell? Is it possible that it was written longer ago than their estimate for the lifetime of a cell and that improvements in the dec

          • I heard it from someone in my own company and have heard similar numbers before. Since we (actually our subsidiary) make the silicon, I doubt we are skewing the data in favor of the nuclear industry. Instead, the point was that we have to get our energy costs down and figure out a better way to make this stuff. Indeed we have, but we are still the biggest consumer of electricity in the state now due to our efforts to make silicon for the solar industry. How ironic.

            • Re: (Score:2)

              by dbIII ( 701233 )

              I heard it from someone in my own company and have heard similar numbers before

              Another sign of the post literate society that unfortunately I'm part of too :( Is anybody out there literate enough to have some reference to cite and not just rumours?

      • Re:How Much? (Score:5, Informative)

        by dbIII ( 701233 ) on Tuesday October 30, 2007 @09:59PM (#21179485)
        It really depends on how big the ingot is that the wafers are cut from and how well the factory is set up. It used to be a very slow energy intensive operation - you are growing very big single crystals of pure silicon after all in a process known as "zone refining". There were a lot of improvements in the 1970s to change the size of the zone melted, some changes to reduce the amount of this that has to be done and doing things in large volumes (big ingots with big wafers) brings the energy use per square millimetre of silicon components right down. There are still people that look at the numbers from the first solar cells produced for the early space program by experimental methods and assume (or pretend as an arguement ploy) the costs are the same today despite the very wide use of semiconductors and the improvements and economies of scale.

        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.

      • Re: (Score:2)

        by mikael ( 484 )
        This web page [processpecialties.com] provides an explanation of the process. You are going to be melting sand into liquid, which is going to require industrial furnaceswhich precision controlled temperatures. High temperature furnaces can use up to 14 kilowatts of energy for a good few hours per ingot of silicon.

        Then the other machines are required to grind and slice the ingot into wavers. These will use a standard industrial supply since they are just doing mechanical motion and maybe some water/gas cooling.

        But that wouldn't tak
    • Yes, you're right- on a comparable scale of cost per megawatt produced our current PV technology costs more than 10x that of all other common energy sources. And although PV panels don't have any emmissions, the manufacturing process isn't exactly environmentally friendly either. However it is great for specific circumstances, mostly isolated (off-grid) applications, or for peak-demand in sunny areas (solar-powered air conditioners!). So developments like this one are welcome but it would be wrong to thi
    • You do realize that the point here is in taking SCRAP silicon wafers and putting them to productive use? They're not claiming that semiconductor quality silicon is "THE ANSWER" for low cost/low energy manufacture of photovoltaic cells. They've just developed a process that allows them to use material that would otherwise go to a landfill for production of solar energy.

    • 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.

      Great point...except this article is talking about using wafers that were already made for CPUs. So all this energy it takes to make the wafer has already been expended, it is done, over with, can't be returned, end of story...except now they can get some of it back if they use the wafer for so

      • Re: (Score:2)

        by Luyseyal ( 3154 )
        Yes, the news is not "IBM Invents Solar Recycling", but that they found a better way of erasing their Intellectual Property from the wafers so they can be recycled more readily.

        -l

    • 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.

      Care to explain this statement to mere humans? It sounds like you are saying that there's no such thing as entropy, or that the sun is going to suddenly go out tomorrow.

      There are enough existing solar panels to produce more solar panels with existing technologies forever, or at least until the sun burns out. There is no need to use any energy input other than the sun, and if there were, manufacturers could just use their first production runs to power subsequent runs. It's called up-front investment and

  • Dear IBM, (Score:5, Funny)

    by tjstork ( 137384 ) <todd.bandrowskyNO@SPAMgmail.com> on Tuesday October 30, 2007 @09:34PM (#21179293) Homepage Journal
    If you just give me a few hundred thousand dollars, I'll buy a little boat and just dump all your trash in the ocean.

    signed,

    Nigeria
  • scrubbing waste silicon wafers clean

    Looks like Intel and AMD just found themselves a new dry cleaner

  • ha ha bad pun (Score:3, Funny)

    by rleamon ( 895852 ) on Tuesday October 30, 2007 @09:44PM (#21179371) Homepage
    "the cost of solar panels reflects it" Slow day at the news desk.

  • This is great (Score:4, Interesting)

    by Fengpost ( 907072 ) on Tuesday October 30, 2007 @09:48PM (#21179395)
    However, it would more impressive if someone can recycle the waste of LCD substrate. The LCD generates huge amount of waste as well.
  • So what do they do with SOI wafers? Remove the whole buried oxide layer by CMP?
    • So what do they do with SOI wafers? Remove the whole buried oxide layer by CMP?

      Sure, why not? The buried oxide layer in an SOI wafer is much thinner than the oxides in the metal stack. If they are using an aggressive CMP to polish the whole metal stack away (which is what I am assuming they are doing, probably without the C, though - I bet it's purely a mechanical polish), removing the relatively thin buried oxide shouldn't add a whole lot to the process.
      • But pure mechanical polishing will produce a lot of dislocations, which will kill the efficiency of the photovoltaics. Also I am thinking if they keep the insulating layer (SmartCut or nanoCleave or ELTRAN wafer), they can use the wafer to make the type of photovoltaics with both N+ and P+ on the backside (I just can't remember the name) and the oxide as passive/antireflection layer. But are the handle wafers high quality wafers? For SIMOX wafer, I think the defects density maybe too high to be used in t

  • Oh man! (Score:5, Funny)

    by Derek Loev ( 1050412 ) on Tuesday October 30, 2007 @09:55PM (#21179457)
    "Are those solar panels real??!! They're huge!"
    "No way man, that's got to be silicon. There's no way it's natural."
  • Big Blue is going to change their name to Big Green.

  • hmmm (Score:4, Informative)

    by thatskinnyguy ( 1129515 ) on Tuesday October 30, 2007 @10:49PM (#21179715)
    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 [siliconvalleyvisitor.com]. All kidding aside, the video also showed all the waste produced. And with silicon being worth a billion dollars an acre [news.com], a little bit of payback would be appreciated by chip manufacturers. I'm sure.

    • Re: (Score:3, Interesting)

      by rah1420 ( 234198 )
      I've done better than visit a museum; I used to work at what was once Lucent Microelectronics in Allentown PA where, before they tore it down to make way for a ball stadium, they had wafer fabs and even a crystal growing installation onsite.

      The best part of that job was signing up for being a chaperone for "Take your Daughter to Work Day" (it was still daughters only then) and herding the kids around to the different areas. We watched the ingots growing and being cut into wafers, polished, kerfed, and then

  • Question about solar power (Score:5, Interesting)

    by Entropius ( 188861 ) on Tuesday October 30, 2007 @11:15PM (#21179847)
    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.

    • Re: (Score:2)

      by dbIII ( 701233 )
      Yes - but you have to build something big, which means a big capital cost. There have even been pilot projects that store enough steam to drive the turbines at night and another that splits ammonia during the day and reforms it at night to give base load. Since oil and coal are cheap there is little incentive to build very large solar thermal plants and it doesn't work well at the low end so we see small photovoltaic generating projects instead. If you double the size of the photovoltaics you get twice t

      • Re: (Score:1)

        by defnoz ( 1128875 )
        Something like this [bbc.co.uk] perhaps?

        Of course, solar panels still have advantages in microgeneration and for portable devices etc.

    • Re: (Score:3, Informative)

      by mspohr ( 589790 )
      This has been done. Look at this link for some projects in California. http://www.energy.ca.gov/siting/solar/index.html [ca.gov]

      Look at the Stirling engine projects.

    • Re: (Score:1, Informative)

      by Anonymous Coward

      Aren't there ways to get solar power without futzing with photovoltaics?

      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 [ausra.com]

      Solar thermal systems have certain advantages over solar photovoltaic systems:

      • They're more economical because the technology is relatively simple
      • They can store the heat overnight, thus providing "base load" capacity
      • The superheated steam they produce can be integrated with existing

    • 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?

      You're now subject to the challenging laws of thermodynamics. Engine efficiency is directly related to temperature difference, and the temperature of the water is based on the square of the area you're using to gather sunlight. In other words, while solar-thermal is practical in very large installations, yo

      • the temperature of the water is based on the square of the area you're using to gather sunlight

        No it's not.

        The collector temperature is related to the sterradial average of the temperatures it "sees" in all directions around it.

        If it's in space and "sees" sunlight for the sun's normal subtended angle and 4-degrees absolute empty space around it (mod a sprinkling of distant stars) its equilibrium temperature is about that of a high-orbit satellite at the earth's orbital distance from the sun - i.e. a bit bel

    • Re: (Score:3, Informative)

      by Doctor Faustus ( 127273 )
      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 hea

  • nano solar is the way to go (Score:1, Insightful)

    by Anonymous Coward
    print solar panels on any kind of thin film. http://www.kqed.org/quest/television/view/399 [kqed.org]
  • http://www.ez2c.de/ml/solar_land_area/ [ez2c.de]

    (it NEVER hurts)

    (now, people complaining about storing energy for night-time, can start ranting NOW!)

    • Re: (Score:2)

      by hey! ( 33014 )
      With respect to storing energy for the nighttime, that is a tricky long term engineering problem that has a marvelously simple and effective short term solution: you store the nighttime energy as unburned fossil fuels in your existing coal, natural gas and oil fired plants.

      The storage problem only becomes critical when your nighttime energy demand can no longer be economically met by fossil fuels. In projecting when that point happens, you have to factor in the net reduction in demand for fossil fuels by
  • I was at the gym, and while I was running on the treadmill the Discovery Channel's "How it's made" program was on. The first segment was on the manufacture of disposable plastic shopping bags. It was of those production processes that has literally dozens of amazingly clever little machines so that people have little to do but move bulk materials like plastic pellets or sheeting from one production line to another, eventually taking boxes of finished product off the last machine.

    The next segment was on t

    • The next segment was on the production of solar panels, and the contrast was not only striking, it was shocking. The entire process is done by hand.

      No it's not. That's the way they did it on that show, but that was done at an exceedingly small shop. I think they said that shop did something like six panels a day, which would work out to a manufacturing capacity of something like 100 kW/year. By contrast, even a relatively small PV production line is fairly automated, handles as many wafers in a day as a h

  • IBM probably processes less than 100,000 wafers, mixed 200mm and 300mm, a month. If they are yielding 80% to devices that is 20,000 wafers a month available for solar applications. And this is a very aggressive estimate. It isn't a lot compared to the needs of the photovoltaic people, who now by more silicon that the semiconductor companies.

    But recycling is good, I guess, given the cost of making silicon in the first place.
  • Why not store the wafers for a few years before selling them as scrap? Does anyone really care about yesterday's outdated chip designs?

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