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MIT Solar Towers Beat Solar Panels By Up To 20x 159

An anonymous reader writes "A team of MIT researchers has come up with a very different approach to solar collectors: building cubes and towers that extend solar cells upward in three-dimensional configurations. The results from the structures they've tested show power output ranging from double to more than 20 times that of fixed flat panels with the same base area (abstract, full pre-print). The biggest boosts in power were seen in the situations where improvements are most needed: in locations far from the equator, in winter months and on cloudier days."
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MIT Solar Towers Beat Solar Panels By Up To 20x

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  • Picture... (Score:5, Informative)

    by Anonymous Coward on Tuesday March 27, 2012 @12:34PM (#39485805)

    Picture available here [extremetech.com]. It's a solar pancake!

    • Re:Picture... (Score:4, Informative)

      by Firethorn ( 177587 ) on Tuesday March 27, 2012 @01:31PM (#39486823) Homepage Journal

      That's an interesting article, but I found the link about using an ion cannon [extremetech.com] to make cells 1/10th as thick at 1/2 the cost of cheap chinese cells to be potentially more revolutionary.

      At this point we're not especially limited on space for solar installs. Our problem is that our collection systems aren't cheap enough.

      • Re:Picture... (Score:5, Informative)

        by uigrad_2000 ( 398500 ) on Tuesday March 27, 2012 @01:51PM (#39487199) Homepage Journal

        The Ion cannon article was featured on Slashdot two weeks ago. [slashdot.org]

        I think a better way to state it, would be to say that efficiency per square foot of ground used is not important, unless the cost of the cells come down.

        Now that there is word of a new manufacturing process to reduce cost, two weeks later, we find an article about how to arrange low-cost cells.

      • Re:Picture... (Score:4, Informative)

        by pla ( 258480 ) on Tuesday March 27, 2012 @02:39PM (#39487897) Journal
        At this point we're not especially limited on space for solar installs. Our problem is that our collection systems aren't cheap enough.

        This. These 3d shapes give a better yield for a given footprint, but actually cost more.

        Hey, If you can make individual flat panels cheaply enough, I'll pave half an acre with them for all I care about the "footprint". That said, I really don't understand why no major company has come up with mass produced smaller panels in a roofing-shingle form factor, but, entirely different topic.

        Now, the part of this that does appeal to me involves the improved yield at high latitudes - But does that mean improved only against the footprint, or against the surface area? If the former, hey, cool, I live just far enough North that solar won't realistically pay back the investment given the present dominant efficiencies and prices; If the latter, then to repeat myself, just make 'em cheaper, I'll provide the space.
        • I really don't understand why no major company has come up with mass produced smaller panels in a roofing-shingle form factor, but, entirely different topic.

          Solar shingles have been around for quite some time.

          http://www.google.com/search?&q=solar+shingles [google.com]

          If our conversation is going to follow the pattern of a typical slashdot discussion thread, you will now need to retroactively define the terms "major", "mass produced", and "smaller" in such a way that you can insist that I am not only wrong, but also

        • Yield at high latitudes is not a big deal even for conventional solar arrays. Solar PV is huge in Germany (basically due to federally mandated feed-in tariffs for over a decade.)
          Now consider that Berlin is at the latitude of South Hudson Bay.

        • Exactly. All these "researchers" seem to care about is power collection per area of the footprint. Who cares about that? Heck, you could easily beat these towers just by making a giant vertical panel of solar cells 10 times as tall. The efficiency per unit area of the photovoltaic cells will be crap, but who cares, as long as we have the highest power numbers per footprint area!!!

          What's important is how much power you're collecting, in relation to the area of the PV panels themselves. How much area the

      • Re:Picture... (Score:5, Informative)

        by fast turtle ( 1118037 ) on Tuesday March 27, 2012 @02:46PM (#39488001) Journal

        Did you RTFA? I happened to do so having caught it a couple of days ago. The interesting element to this design is the early/late (dawn/dusk) power generation as the current method doesn't get enough solar incidence to generate anything until 3 hours after sunrise/3 hours before sunset. That's 6 hours of production that's being missed, which is why this design reaches 15-20x the generated power of conventional flat panels.

        • Re:Picture... (Score:4, Informative)

          by icebike ( 68054 ) * on Tuesday March 27, 2012 @03:01PM (#39488189)

          Yeah, I read dud RTFA. It said:

          While the cost of a given amount of energy generated by such 3-D modules exceeds that of ordinary flat panels, the expense is partially balanced by a much higher energy output for a given footprint, as well as much more uniform power output over the course of a day, over the seasons of the year, and in the face of blockage from clouds or shadows.

          This suggests to me that there is no ROI on this method, or at least none that could not be more cheaply matched by simply tilting existing solar arrays [pureenergysolar.com].

          I don't discount the possibility that we are seeing another poorly written TFA, and that there is an eventual ROI. But the implication is that the generation of power early and power late in the day may never actually pay for the structures and maintenance needed to collect it, leaving you with zero net gain over a tilted array in northern latitudes.

          • I think the wording of the article could stand improvement; meanwhile, without facts and figures upon which to do the necessary calculations, I think any definite statement about ROI (I prefer payback period) is premature. In the interim it seems like some interesting engineering research in its own right and I'll be interested in any follow up.

        • If you have one solar cell and want to install it at a particular latitude, there is a specific orientation that will produce the most energy over a day. All cells should be in that orientation to maximize their individual energy production. This is what leads to fixed installations being large flat arrays with every cell in the same orientation. If you have 100 cells it is true that you can put 50 of them facing more to the easy and 50 more to the west, and you may be able to do this with less land area th
    • Picture available here [extremetech.com]. It's a solar pancake!

      so if a solar pancake works, with the down facing solar panels and everything, what about stacking several cubes at their corners, like several of these [wikipedia.org] on top of each other? That way you don't have sections that are not facing sunlight like you do with the MIT solar pancake design since there's no solar panels on the side of the structure, [extremetech.com] with a cube balanced on a tip you'd have a sun facing panel at all times. Set-up would be a breeze too since you don't have to face it towards the sun like the MIT des

      • by es330td ( 964170 )

        with a cube balanced on a tip you'd have a sun facing panel at all times.

        So by extension you then have some portion of the remaining panels NOT facing the sun at all times. If we're talking about ROI, doesn't this present a huge hurdle?

  • Prior art... (Score:4, Interesting)

    by msauve ( 701917 ) on Tuesday March 27, 2012 @12:37PM (#39485867)
    So, MIT has basically recreated what a 7th grader has previously done [wattsupwiththat.com].
  • by O('_')O_Bush ( 1162487 ) on Tuesday March 27, 2012 @12:38PM (#39485877)
    Big surprise that structures in volumetric configurations ended up being more efficient at gathering energy... considering plants have known this since they left the seas hundreds of millions of years ago.
    • Big surprise that structures in volumetric configurations ended up being more efficient at gathering energy... considering plants have known this since they left the seas hundreds of millions of years ago.

      Are you suggesting that lichen is not the evolutionary pinnacle of plant evolution? Oh sure, maybe your fancy trees produce more nutrients per unit land area, but AT WHAT COST?

    • Growing up does not net you any more energy as a whole. The purpose for plants and trees to grow up is to beat their neighbor out for access to that sunlight. Natural selection is inherently selfish. Were we intelligently designed, the world would be flat and covered in a thin layer of green algae. You erect your massive solar tower in your own backyard, and now your neighbor can't get a sun tan.
  • paper link (Score:5, Informative)

    by Trepidity ( 597 ) <delirium-slashdot@nosPAM.hackish.org> on Tuesday March 27, 2012 @12:38PM (#39485881)

    As seems depressingly common in science journalism, they vaguely mentioned the existence of a paper, but don't actually give the title or (dare we hope) a hyperlink to the paper. At least they did mention the name of the journal it was published in.

    In any case, the paper is "Solar energy generation in three dimensions." If you're at a university with a subscription the official version (not open-access) is here [rsc.org]. There is also an open-access preprint version at the arXiv [arxiv.org].

  • by Hentes ( 2461350 ) on Tuesday March 27, 2012 @12:39PM (#39485911)

    Most people use solar panels because they can be comfortably put on rooftops. If someone has enough room for these 3D structures they could just install a Sun tracking system that's even more efficient.

    • And, what do your neighbors think about you shading their solar panels?

    • by DerekLyons ( 302214 ) <fairwaterNO@SPAMgmail.com> on Tuesday March 27, 2012 @01:11PM (#39486401) Homepage

      If someone has enough room for these 3D structures they could just install a Sun tracking system that's even more efficient.

      Under conditions where you can see the sun - that's true. But the point of TFA is that these 3D structures are more efficient *in situations where sun trackers aren't more efficient*.

      Conditions exactly like those currently outside my window - where the sky is nearly uniformly bright but you cannot see the sun at all due to the clouds. Conditions that are fairly common here in the Pacific Northwest.

      • by jschen ( 1249578 )
        You don't need to see the sun to track it. Its location is predictable, so you only need to know your current location (easily determined by GPS at installation) and the current date and time.
      • I'm going to go out on a limb here (pun not intended) and predict that if you do hours of mind-numbingly boring math, it will turn out that if there is no tracking, the arrangement of leaves on trees are optimal for capturing sunlight from varying angles over the course of Spring/Summer/Fall.
    • Re: (Score:2, Interesting)

      by Anonymous Coward

      A tracker means moving parts, though; this arrangement might be cheaper and more reliable.

  • Costs more (Score:3, Insightful)

    by AdrianKemp ( 1988748 ) on Tuesday March 27, 2012 @12:42PM (#39485949)

    The cost/watt is higher, this is DOA I dare say.

    They're simultaneously saying that it's most beneficial for northern/southern areas where daylight is diminished and that it's a more compact arrangement of cells.

    Those two don't go together well... Most northern and southern areas have very large open areas due to having low overall population density.

    Cost/Watt is all that matters in most areas for solar panels, Watt/weight in the rest. I can't see this being of use except in powering small devices

    • by Lehk228 ( 705449 )
      not much use right now, but possible future development of cheap / low embodied carbon / low usage of rare and toxic solar collectors with a lower collection rate could benefit from this greatly
    • Re:Costs more (Score:4, Informative)

      by chudnall ( 514856 ) on Tuesday March 27, 2012 @12:56PM (#39486155) Homepage Journal

      The time is ripe for such an innovation, Grossman adds, because solar cells have become less expensive than accompanying support structures, wiring and installation. As the cost of the cells themselves continues to decline more quickly than these other costs, they say, the advantages of 3-D systems will grow accordingly.

      “Even 10 years ago, this idea wouldn’t have been economically justified because the modules cost so much,” Grossman says. But now, he adds, “the cost for silicon cells is a fraction of the total cost, a trend that will continue downward in the near future.” Currently, up to 65 percent of the cost of photovoltaic (PV) energy is associated with installation, permission for use of land and other components besides the cells themselves.

    • With the zigzag tower configuration, it's just more nooks and crannies for snow to collect in and block even more sunlight.

      I'll wait for Zero Point Energy.
    • Umm, no southern isn't southern US southern is south of the equator. While I'll give it to you that there are less people in the southern hemisphere there still is ~800M people and the land mass is much smaller (less than half), and about 20% of that is Antarctica (which presumably wouldn't be solar accessible anyways because it is in the polar region), so more dense than you'd expect I think. But still less than the northern hemisphere of course and they probably would just tear down some more rainforest r

  • misleading (Score:5, Insightful)

    by demonbug ( 309515 ) on Tuesday March 27, 2012 @12:47PM (#39486021) Journal

    20x output (compared to a flat panel with the same footprint).

    Not really news. This is like excitedly proclaiming that a 20 story building has nearly 20 times the floorspace of a single story building with the same footprint. Uh, no shit? (Or that a 20 story building receives more insolation than a 1-story building; hmm, you think maybe it has a lot more surface area?) I also like that they hand-wave away the fact that it costs significantly more per unit output by saying that cells are getting cheaper. Great.

    Not that there aren't uses - it absolutely makes sense to go this route where you have limited footprint space - but it just doesn't seem at all revolutionary. I guess if you tack the letters M-I-T onto a press release it instantly becomes newsworthy.

    • Just goes to show you while Boston has Harvard, MIT and other good schools there are still dumb ideas in the city and in those schools :-) I guess stupidity obeys diffusion too :-)

    • by Guspaz ( 556486 )

      By the same example, if I take a photovoltaic panel that measures 100x100x1 centimetres, and I turn it on its side, causing it to capture only, say, 50% as much energy, by their measurement (power produced versus base size) I've just increased my efficiency by 5000x... Even though I just took the panel and turned it on its side.

      Yeah, I can see it being useful in some places, but there's nothing revolutionary here. It's just a novel way of mounting the existing panels.

    • by AK Marc ( 707885 )
      And they compare structure footprint to output, not output per shadowed area. So you put them up and shade your neighbor. He's screwed, you get a benefit. He'd be better off if both of you had flat panels. So footprint isn't the only consideration.
  • by TraumaFox ( 1667643 ) on Tuesday March 27, 2012 @12:56PM (#39486163)
    Quick, someone alert all of the major energy companies so they can buy up the patents and sit on them for eternity!
  • You're still limited by physics, and ultimately even with an advanced 3D layout only so much sunlight hit's every square meter. Even if we could magically capture 100% efficiency it will never touch other forms of power generation for the same density, and will require large tracts of land for the same effect.

    This is pretty neat, but a far cry from ever solving our energy crisis.
    • by TheSync ( 5291 )

      You are correct that the earth receives only so much sunlight per square meter. These towers are only absorbing light that would otherwise not hit the roof - it might otherwise go into the street (where solar panels are not practical) or could be shading your neighbor's roof (where solar panels could be practical).

      • it might otherwise go into the street (where solar panels are not practical)

        Run a network of narrow tubes just below the surface of the road, pump water through them to draw off the heat absorbed from the sun to a heat pump of some sort to power a generator.

        While I agree you might not want to do that on a major road, nothing to stop you laying it into a car park.

    • Actually, we get 1,000 watts from sunlight per square metre, so it would take a very minor portion of the earth's landmass to power our civilisation.
    • by AK Marc ( 707885 )
      Someone else pointed out it's about 1kW per m^2. Given the power consumption of the planet, that's more than enough power to supply all our needs. Panels on every house pumping back into the grid would be sufficient. We wouldn't need to develop a single bit more than we already have, just develop more efficiently (using roofs and such).
      • by Tynin ( 634655 )
        Yes, the output of the sun is enough, but factor in transmission loss of ~6.5% and that the conversion efficiency is only ~33% and it isn't so good, at only ~311 - 333Watts per m^2 of potential PV. Which really isn't that bad once I thought about it a bit more...
        • by AK Marc ( 707885 )
          I don't like sodium, but I like the concentrated heat solutions. Sodium adds needless complexity to answer the "doesn't make power at night" whiners. Total power and reliability is more important than placating whining naysayers.
  • I affixed high-efficiency monocrystalline silicon PV cells to the aluminum cans and used pizza boxes strewn about in my yard and now my trash is generating electricity! Electricity from trash, wow!
  • In the place where this would presumably be most useful, where horizontal space is at more of a premium than vertical space, it could well be illegal due to solar access [sunschools.org] laws. Here in Denver, it has led to some odd-looking asymetric second-stories when they are added to existing bungalows -- where, say, the left half of the A-shaped roof has a shallow or near-flat slope and the right half has a steep pitch.

  • Is there some interesting physics going on, or is this just taping a bunch of cells vertically to intercept more light at a low incidence angle? Surely,that can't be all there is to it, right?

    • Am I the only one thinking of the next posting "Dysfunction In Modern Science?" on /. today right after this one?

      Or the one a while back about a child who made a TREE with solar leaves that performed better but it turned out he had it all wrong and the media hyped the BS?

      For me, in winter I have a 78 degree perpendicular with the sun-- that is nearly vertical in which case a bunch of staggered 45/-45 degree panels would work and the lower ones would get a lot of sun considering they are supposed to work fin

  • Oriented or tracking panels produce only around 20-30% more energy than flat horizontal panels, when averaged over a year over most of the USA. This because much of the insolation is diffuse. NREL has maps that show the measurements at http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook/atlas/ [nrel.gov]

  • Put some white space to the left of the text on your page. It's a real pain to read words that are jammed right against the edge of a monitor.
  • MIT solar towers (Score:2, Insightful)

    by Anonymous Coward

    It's a stupid concept. If I had been asked to review their paper I would have recommended not publishing it. Here's a link to their abstract:


    "We demonstrate that absorbers and reflectors can be combined in the absence of sun tracking to build three-dimensional photovoltaic (3DPV) structures that can generate measured energy densities (energy per base area, kWh/m2) higher by a factor of 2–20 than stationary flat PV panels for the structure

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