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Earth Science Technology

MIT Develops Ultra Thin, Light Weight, Efficient Solar Cells (blastingnews.com) 135

MarkWhittington writes: Researchers at MIT have developed a gossamer thin solar cell that is made of layers of flexible polymers. The cell is so light that it can rest on a soap bubble without breaking it. As a bonus, the thin, light cells puts out 400 times more power than the standard, glass covered photovoltaic cells, at about six watts per gram. According to the researchers, this new development could help power the next generation of portable electronic devices.
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MIT Develops Ultra Thin, Light Weight, Efficient Solar Cells

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  • by Sowelu ( 713889 ) on Tuesday March 01, 2016 @03:10PM (#51616915)

    Many other types of solar cells suffer badly from any damage anywhere, however small. Putting this stuff on clothes or on a notebook, or on a vehicle that might get whacked by a rock, seems like a pretty damage heavy environment...rooftop solar doesn't usually have that problem because it's stationary.

    • Flexible implies far more damage resistant, no?

      If it's more bendy it's less break-y.

    • Watts per square inch is more important. If I have a ultrathin solar panel and it gets that many grams/watt it probably takes a huge surface area to get that power.
      • by Ravaldy ( 2621787 ) on Tuesday March 01, 2016 @03:42PM (#51617189)

        Watts per square inch is more important. If I have a ultrathin solar panel and it gets that many grams/watt it probably takes a huge surface area to get that power.

        You need to read the article to understand why it's an advance. For 1 the process itself creates clearer cells hence an increase in efficiency. It you want to compare conventional cells to this one you need to have comparative data as you mentioned which we do not have. In their application watts per grams is ideal because their current intended use is on flying objects such as weather balloons. Here's the part of the article:

        While the solar cell in this demonstration device is not especially efficient, because of its low weight, its power-to-weight ratio is among the highest ever achieved. That’s important for applications where weight is important, such as on spacecraft or on high-altitude helium balloons used for research. Whereas a typical silicon-based solar module, whose weight is dominated by a glass cover, may produce about 15 watts of power per kilogram of weight, the new cells have already demonstrated an output of 6 watts per gram — about 400 times higher.

        • The comment on clearer cells made me wonder if you could use it in layers. Obviously, lower layers get less sun, but it might make up for the efficiency to a certain degree even if each layer drops by 50%, you could put 3 or 4 layers and have a decent output.

        • by Squirmy McPhee ( 856939 ) on Tuesday March 01, 2016 @07:16PM (#51618439)

          Watts per square inch is more important. If I have a ultrathin solar panel and it gets that many grams/watt it probably takes a huge surface area to get that power.

          You need to read the article to understand why it's an advance. For 1 the process itself creates clearer cells hence an increase in efficiency. It you want to compare conventional cells to this one you need to have comparative data as you mentioned which we do not have. In their application watts per grams is ideal because their current intended use is on flying objects such as weather balloons. Here's the part of the article:

          While the solar cell in this demonstration device is not especially efficient, because of its low weight, its power-to-weight ratio is among the highest ever achieved. That’s important for applications where weight is important, such as on spacecraft or on high-altitude helium balloons used for research. Whereas a typical silicon-based solar module, whose weight is dominated by a glass cover, may produce about 15 watts of power per kilogram of weight, the new cells have already demonstrated an output of 6 watts per gram — about 400 times higher.

          "Clearer cells" does not mean an increase in efficiency, in fact it means just the opposite. A clear solar cell is not absorbing a significant amount of light (or at least if it is, it is not producing a significant voltage, and hence not much power), whereas conventional opaque solar cells absorb extremely efficiently in the part of the spectrum where the sun produces the most photons.

          Furthermore, the W/g comparison from the article is utterly meaningless. A solar cell made from a 180-micron-thick silicon wafer can't survive the elements without encapsulation, hence the heavy glass sheet for terrestrial solar modules. Even solar cells launched into space are protected by a polymer encapsulant and a glass sheet (though both are much thinner and lighter than for a terrestrial module). Implying that you can replace a fully encapsulated solar module with a completely unprotected polymer solar cell 1/10th the thickness of a sheet of cellophane to is like saying you can replace a boat's sail with a sheet of gauze and steer your way through a gale. Sure, maybe the cell does put out more W/g than a conventional cell, but quantifying the claim like this makes them look dishonest.

          Finally, to date, organic solar cell degrade rapidly when exposed to light -- so rapidly that organic cell researchers have been known to transport their cells to certification labs in light-tight boxes and supervise their efficiency measurements to ensure the cells are not needlessly exposed to light for even a few minutes. Add the high-radiation environment of space to the mix and you aren't likely to see these cells being shot into space anytime soon. Not to mention that even undegraded the cells are only 2.3%-efficient. The cells used in space applications are already significantly lighter than the structures they're mounted on, so cutting the efficiency by more than a factor of 10 is likely to result in increased weight no matter how light the cells are.

    • by zlives ( 2009072 )

      i think they said its as resiliant as a soap bubble... err weight

    • by hey! ( 33014 )

      Well, I should imagine that's a complicated question, because damage resistance is ultimately a property of the overall installation and design, not just individual components.

      The lightness and flexibility of the thing suggests that as a component it would be easy to damage; for example you could pick it up and crease it like a piece of paper. But those same properties would make it possible to install it in ways that would be quite damage resistant. For example on a notebook you could glue them to the su

    • Rooftop solar does have to deal with things like, wind, and snow, and occasionally, hail.
  • Watts per gram? (Score:5, Insightful)

    by LynnwoodRooster ( 966895 ) on Tuesday March 01, 2016 @03:12PM (#51616927) Journal
    Interesting, but portable products are also fairly limited by available surface area, which apparently has not changed in terms of amount needed per Watt.
    • by zlives ( 2009072 )

      maybe it could be used as a trickle charger in addition to battery...

      • by ganv ( 881057 )
        Yes it might be useful in very low power applications that benefit from light weight But the article says the current version is not very efficient, meaning it only extracts a small fraction of the energy in the light striking it. Standard solar cells might be 10% to 25% efficient. This may be only a few percent. In most applications I can think of, solar power is more limited by collecting area than by photocell weight, so this seems like niche product.
    • Oops, I think I accidently copied your comment. Was thinking the exact same thing, apparently. Sorry.
    • If it's paper thin, flexible, and really light ... you can cram a lot of surface area into a rolled up tube.

    • portable products are also fairly limited by available surface area

      A flexible panel can be rolled up and stuffed in a backpack, and then unrolled to charge a phone or tablet.

      • A flexible panel can be rolled up and stuffed in a backpack, and then unrolled to charge a phone or tablet.

        And that would be another cool product that very few people would actually buy and use, just like the folding panels available now. Makes much more sense to buy a backup battery or charger pack unless you are on some kind of long outdoor stint.

    • Yeah, it's about as useful as measuring the performance of an engine in terms of how many people named Barry worked on the team that developed it. Our new engine has over 5 times the HP/Barry as our previous model!

      While it's nice to know that potentially coating a product with these won't add to the overall weight in a meaningful way, it doesn't mean that they'll be able to generate enough power to keep the device running. There's also the matter of how expensive are these to manufacture. The article mak
    • In fact from the paper [sciencedirect.com] (subscription probably required) the efficiency of this cell is about 2.3%, about 1/10 that of conventional silicon solar cells - so per unit area you're much better off with silicon. The watts per gram metric is more about them showing that very little material is needed for this cell which is a component towards achieving low cost.

      The idea of this work is that organic cells in principle might be able to become cheaper per unit area than silicon solar cells (they will need to be muc

    • Cost to launch a payload into low earth orbit is currently around $3000/kg for the smaller rockets, $10,000/kg for the larger ones. About $20,000 - $30,000/kg for geosynchronous orbit. So yeah this is a really big deal.
    • Re:Watts per gram? (Score:5, Interesting)

      by Daniel Matthews ( 4112743 ) on Tuesday March 01, 2016 @06:17PM (#51618141)
      How about this for an application, the cells are so light that they can form the skin of a hydrogen lofted blimp with enough surface area to run all of it's payload and convert it's water ballast to hydrogen to allow for buoyancy control. The reverse process of ballast recovery uses a hydrogen/oxygen fuel cell so that no water is lost in total, and additional power is generated. What we are talking about here is mid to upper stratosphere cruising blimps with an endurance measured in years. e.g. Project Loon type communications networks. These are particularly important as they can be deployed very quickly if our communications satellites are destroyed by a solar flare and we can't put more of them up quickly because the dead ones also triggered a space junk collision cascade.
    • the thin, light cells puts out 400 times more power than the standard, glass covered photovoltaic cells

      Wrong; they put out 400 times more specific power [wikipedia.org] than standard cells. The summary omits the word "specific," which makes for a huge error.

  • Thats a new way of defining solar cell efficiency, usually they go by area. It certainly won't power the next generation of electronic devices, maybe in 10 or 20 years something like this might see production
    • Sometimes weight is more important, especially when you can make big sheets of this that can be unrolled by some mechanical means. For example, when you need to use solar power as part of a package going on the pointy end of a rocket meant to exit the atmosphere.

      For that kind of thing, weight is everything.

    • Thats a new way of defining solar cell efficiency, usually they go by area. It certainly won't power the next generation of electronic devices, maybe in 10 or 20 years something like this might see production

      I think they got the idea from the less common metric g/W. A little over a decade ago there was a shortage of purfied silicon that lasted quite a few years, and during that time the solar industry became very interested in the number of grams of silicon that were required to produce a watt of power. Naturally, the power conversion efficiency of the cell has an impact on this number, but so do things like the thickness of the wafer, how much silicon is lost during production, and so forth. My guess is that t

  • by laing ( 303349 )
    How do such lightweight cells dissipate the heat created while they are operating? It seems to me that they would self-destruct in a very short time.
  • That means that instead of using a single layer of conventional cells, you can have hundreds of layers of these, generating hundreds of times more power per surface area!

    Oh, wait. That doesn't actually work, and that's one reason we always hear about power per area, but rarely per volume or per mass.

    Now, if these can be produced as cheap, disposable decals, where you just stick on another one when your current one gets too torn up -- that could be seriously useful. Even better if we can unfurl them by the s

    • by gstoddart ( 321705 ) on Tuesday March 01, 2016 @04:08PM (#51617389) Homepage

      You know, I bet if you could unfurl 10 or 20 feet of it, it would also be useful in a lot of places.

      Hell, for camping make an entire tarp out of it. It's both your shelter over the picnic table and your power source. If it's portable, light, and flexible it's not like there aren't situations in which you can simply let it cover area once you get it there.

      If the mass is low enough, getting a sufficient area to a location to be useful becomes a whole lot easier.

      I can imagine tons of places where people would say "yeah, so, I've got 50' of space I can put this". How many watts can you get out of a 50' strip? I'm betting more than enough to be useful.

      • by afidel ( 530433 )

        Exactly, make your rain fly out of it, now when you setup your tent your also generating electricity. Or put it as the outer layer on your jacket, now you're generating electricity wherever you go.

    • Anything that flies cares about the weight. A lot.

      This process boils down to making a thin film (2 micrometers) of flexible solar cells by throwing out the bottom (or top - depending on the cell) part of the solar cell and using the same thin film as both the top and the bottom layer.
      I.e. Both the solar cell carrier and the coating are made out of ultra-thin coating.

      Think mounting solar cells on transparent sticky tape, then adding another layer of same tape on top as protective coating.
      Only a lot thinner t

    • by laing ( 303349 )
      It actually DOES work in some cases. Many spacecraft presently use triple junction GaAs photovoltaics [spectrolab.com] with ~30% efficiency. Typical single junction Si cells top out at around 12% efficiency. Quad junction cells [spectrolab.com] exist (~43% efficiency), but I'm not aware of any that have flown yet (which doesn't mean they haven't).
  • a really lightweight solar model plane or drone would be cool
  • Definitely more energy dense than uranium ore.... Done with that canard at least.
  • Just one more time: We don't care about W/g. We care about $/W.

    • by Anonymous Coward

      Wrong. Since we're buying drugs here, the important metric is $/g

    • by afidel ( 530433 )

      That totally depends on the application. For backpacking I care about W/g, for delivering to the middle of nowhere I care about W/g and W/L (each gallon of fuel delivered to a forward base in Afghanistan cost $400). For my roof I care about $/W and W/m^2. It all depends on use case as to what parameter you need to optimize for.

      • Exactly. I've been watching for a choice that makes good sense for back-country power needs and solar just isn't there yet for my usage.

        Warning, shoddy math ahead. TLDR; This new cell could save 9-10oz off of the current weight of a popular backpacking solar product bringing it in line with the power provided by a 10K mAh power pack over a 5 backpacking day trip. Yay, solar might finally be efficient enough to consider!

        I pack a 10K mAh Anker lithium power pack that weighs about 8 ozs. A GoalZero Guide 1

    • Or W/soapbubble?
      Can a soap bubble carry 6W worth of solar cells? Can the sun provide enough energy for such an area. Or, how big a soapbubble are we talking about? Don't soapbubbles burst spontaneously, i.e. they don't carry any weitght?

      I used to think of MIT as a world-class technical university. But with these sort of releases, I can no longer be sure.

  • "How long does it last?"

    "I would like another question."
  • I've always liked the idea of retiring in the sky - nothing keeps the relatives away better. Now maybe my solar-powered blimp can happen..
  • by swell ( 195815 ) <jabberwock&poetic,com> on Tuesday March 01, 2016 @07:03PM (#51618367)

    watts per gram ?
    Since when is that a measurement standard?

    By that standard, my car provides152HP per muffler bearing. Its MTBF is 32 dog years and fuel efficiency is 1.4 teaspoons per nautical mile . . . Oh, I get it- this is more slash spam where big numbers are inserted somewhere to wow the ignorant.

    • by mandolin ( 7248 )

      watts per gram ? Since when is that a measurement standard?

      It isn't, yet. But, I first heard of "performance per watt" when Transmeta debuted their first CPU, and similarly thought "who (expletive) cares about that"? Today, performance per watt actually matters in some applications (parallel systems, possibly data centers ...).

      Point is, somebody may find a compelling use for these devices if they can be made practical, be they solar-powered robo-flies or whatever.

  • 400 times might make a big difference when talking weight ratios and something like a PV powered aircraft. But for my roof. 400 times is misleading. Surface area is al that matters in that equation.
  • by gweihir ( 88907 ) on Tuesday March 01, 2016 @08:17PM (#51618751)

    You do not measure solar cell efficiency in "watt per gram", you measure them in percent of the light-energy converted to current. But I guess with conventional cells now up to 20% or so, they could not have claimed a completely inane "400x improvement".

    • The article is not talking about solar cell efficiency, it's talking about power per unit of weight. I guess your reading comprehension is not that good, so let me try "As a bonus, [the new cells] puts out 400 times more power [than the old cells] per gram"
      • by gweihir ( 88907 )

        Power per unit of weight is completely meaningless for solar cells. But I guess your understanding of the subject matter is not that good.

  • This seems like just the thing for an electric airship.
  • Vapor Deposition can be very expensive. High heat and energy are required for even small amounts. Look at how small that sample is! Sure, light weight cells could be useful in certain applications, but that's really not the problem right now for massive installations.
  • Flexible and light yet as efficient - perfect recipe for replacing fossil fuel generators in combat zones where fuel costs up to $30 per gallon.

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