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Pliable Solar Cells on a Roll

Posted by michael on Sun Dec 19, 2004 02:01 AM
from the you'll-be-covered-in-the-stuff dept.
Technology Science
klevin writes "New Scientist is running a story on someone else who's developed thin, flexible, photovoltaic cells: 'The thin and bendy solar panels can be stuck to fabrics, sheets or backpacks and promise a go-anywhere electricity supply.' Whatever happened to those sheets of solar cells that some university here in the US developed several years back? As I remember, the concept was that they could be draped across roof-tops and whatnot. Never heard anything after that." We had post about solar building clothing last year.
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  • Hmmm. (Score:2, Insightful)

    by krymsin01 (700838)
    Would be good to use as a solar sail, I bet.

    • Not really (Score:3, Interesting)

      by Nomihn0 (739701)
      If I understand solar sails correctly, this is not how they work. Instead, they utilize the combined force of billions of subatomic particles radiated by stars hitting a parachute shaped foil to tow a capsule. This is why they are made to be exceptionally lightweight and large in their surface area.
      • Yes, you are correct in that, but if you made the sail out of a large, lightweight, flexible solar panel, you'd be generating electricity and momentum.
        • Usually people imagine solar sails as being made of a very VERY thin film,on the order of a few micrometers thick... the point being that there's very little additional mass created by the sails themselves since you need so much surface area to create any appreciable force. Also, the less mass that's used for the sails, the more mass that's available for payload (or just plain not there, which means greater acceleration).

          Here's a few links (thanks Google and the obligatory Wikipedia):
          A geocities-looking [solarsails.info]

      • Re:Not really (Score:2, Informative)

        by Anonymous Coward
        Oddly enough, not so much the force but the momentum. And not subatomic particals so much as light. Stars appearently make a lot of light. And that's why solar sails, as opposed to cells, are reflective. The radiation pressure equation would probably provide more insight into this should you wish to investigate further.
      • Holy Crap! Am I the only one that read this as a joke? Geez, some people take things way too seriously...and whoever modded this "Insightful" as opposed to "Funny" needs to grow a sense of humour.
        • But unless they can make it much thinner, this WOULDN'T make a good solar sail.

          At "a little thicker than photographic film", it is probably too heavy to be a good solar sail material.

          (Yeah, I know you never said it would, but you do seem to be defending that position.)
    • um, no it wouldn't. i can't believe you got modded up insightful.

      solar sails need to be incredibly light and (as a consequence) thin.

      solar sales work on light pressure not by converting light to electricity to drive an engine.

    • Re:Hmmm. (Score:4, Interesting)

      by The_Dougster (308194) on Sunday December 19 2004, @05:32AM (#11129072)
      Solar sail? Try relativity rocket.

      Just use the solar cells to power up a linear accelerator and shoot nuclei out the back at near the speed of light. If you can get 0.999c from a nucleus you get a tremendous thrust for one little atom. Remember, F mA when you approach the speed of light. Relativity rockets (super ion engines) are probably the best means of propulsion where electric power is plentiful but mass is dear. I'm sorry, but that tiny momentum of a photon is so small it is pathetic. Granted you get 2x boost for reflection vs 1x boost for adsorbtion, but 2 x 0 still equals 0. The only way to practically get around in space is to shoot nuclei out the back of a rocket engine at the speed of light.

      • Piezoelecticity is a force to voltage type thing and while pretty nifty, is unrelated to photovoltaic cells.

        For the laymen out there, I'll explain this in technical terms. If you have a roughly cylindrical quartz crystal, and if you squeeze it, the crystal lattices "snap" into an alternative arrangement which free's up some electrons and essentially produces a static charge. When you remove the stress, the crystal lattice snaps back into its rest state and wants its electrons back.

        Conversely, by applying

  • I wonder if there are other applications that make more sense than clothing that can charge a cell phone.

    I think this type of material could be very useful to provide electricity in places that do not have access to a reliable electrical grid.

    How many watts are needed to run a a phone, a refrigerator, a radio or a computer?

    • Quite a bit more than I would think can be powered by embedded solar cells. It is hard enough for a regular solar cell to power anything with somewhat demanding electricity usage. Besides the fact that solar energy is not exactly the 100% uptime 24h solution.

    • I think this type of material could be very useful to provide electricity in places that do not have access to a reliable electrical grid.

      Solar cells are already used in lots of applications that don't have access to an electrical grid, reliable or not. Pliable solar cells might be useful in more applications, but the ones we have now are used quite a bit.

      What applications, you might ask? `35 mph school zone' lights (it's easier to add solar cells than to run wires.) Remote creek monitoring stati

      • Well, my laptop power supply is rated at 65W.
        It takes about as long to charge the battery (while still using the computer) as to exhaust the battery so i'd imagine the power consumption of the laptop itself is about half this.

        Regarding the mobile phone. My charger has a rating of less than 7W, and i usually need to charge it for about 2.5 hours every 3 days. This is very manageable with solar cells (you have 72 hours to accumulate 21 watt-hours of energy).
  • The new Apple fashion: instead of black shadow people in their iPod advertisements, everyone is now covered with solar panels. (This might actually help the batter life, though, so it's not a total loss.)

  • WARNING (Score:3, Interesting)

    by Dash'n'SlashDot (841636) <(moc.liamg) (ta) (drazzahmilc)> on Sunday December 19 2004, @02:15AM (#11128688) Homepage
    God, solar panelling on the clothes. try to imagine the warning labels they would put on thee things: WARNING! DO NOT USE WHILE BATHING OR WHILE HAVING SEX. ... Don't laugh. You heard it here first. Expect it on your self-heating winter coats next year.
    • Normally winter occurs because there's less sunlight than usual. I don't think they're going to be producing your imagined self heated clothing through solar panels any time soon.

  • Iowa Thin Film Technologies (Score:2, Informative)

    by Anonymous Coward
    The poster might have been thinking about Iowa Thin Film Techologies [iowathinfilm.com]...

  • Flat vs. Flexible Info (Score:5, Informative)

    by sahrss (565657) <sahrsNO@SPAMyahoo.com> on Sunday December 19 2004, @02:20AM (#11128703)
    To address some of Klevin's confusion, since I've been following solar panel advancements:

    Thin, flexible cells have been around for a while. One reason they haven't caught on heavily is because they're nowhere near as 'powerful' (efficient at conversion) as hard panels. Did a quick search (don't take this data *too* seriously, but it represents what's normal); compare panels from these two pages:
    Flexible [solar-electric.com]
    Solid [solar-electric.com]

    Specifically, compare "Unisolar 32 watt flexible solar panel" from the first link to "Shell ST40 thin film CIS 40 watt solar panel" on the second. The flexible panel is 940 sq. inches and 32 watts, while the solid panel 663 sq. inches and 40 watts. Big difference in watt per area.

    I ended up choosing a big solid one to fit in the rear dash of my car; flexible would have been easier to deal with, but it won't fold, and produces less power. (I use the panel in my car to power my laptop/cell phone combo while camping and stuff, it's very cool and gets a lot of questions from random interested people!)

    Here's another chart to compare the two: Product Page [selectsolar.co.uk]
    Tried to find an efficiency rating chart comparing the two types, but no luck. The numbers are out there somewhere...
  • i live in oregon and i really cant wait to get a solor powered raincoat. oh wait
  • Screw clothing to charge cellphones, etc. I can't think of a more petty use.

    The major impact of this tech has nothing to do with its portability/flexibility. The article estimates that the price for a final process fab will be about 1 euro per watt, compared to a highly competitive market which has so far only produced 5.6 euro per watt glass panels.

    Simply put, this would make photovoltaics as an energy source an order of magnitude more competitive, if the process is scalable.
    • Okay, was reading the wrong data, that was peak price, the lowest prices one can find are around E2.66 per watt for crystalline + E3.15 for thin film.

      Still, 1 euro per watt would make a HUGE difference in the viability of solar.
  • I don't care what anyone says.

    Now matter how pliable or environmentally friendly, solar cells are not good on a roll. They taste absolutely nothing like butter, and quite frankly, I find them barely palatable.

    Don't the editors try this these things themselves? This is as bad as that "http://slashdot.org/article.pl?sid=02/10/28/18522 41&tid=126" story. Trust me, those things taste absolutely nothing like fruit-rollups.

  • Is $US52 per square metre about right? (Score:4, Informative)

    by thorpie (656838) on Sunday December 19 2004, @02:49AM (#11128769)

    They quote 7% efficiency, 1 euro per watt.
    Full sun is 1000 watts/sq metre, so with 7% efficiency we get 70 watts/square metre, so it has a cost of 70 euros/sq metre or, at 1.33 euros to the dollar, about $US52.60/sq metre.
    Cover a 10 * 4 metre area of roof for $2,100 and get enough energy, in the middle of summer, to boil your 2 kw electic kettle all day.
    At 12c per kwH for electricity, @ 2.8 kw * 6 hours/day * 365 days/year gives a cost saving of $735 pa, or a repayment of the $2,100 capital in 3 years

    Are these numbers OK?

    At this price will it be practical to disconnect from the grid sometime soon?

    • I think you 1.33 US dollars to 1 euro.

    • Re:Is $US52 per square metre about right? (Score:5, Informative)

      by drphil (320469) on Sunday December 19 2004, @06:28AM (#11129200)
      Although there is nothing wrong with your calculation per se, there are a lot of costs it doesn't include, so it is low by quite a bit. The 1 euro per W (peak Watt or average W - article doesn't say) is only the cost for just the solar cell at high volume manufacturing. At that point you are still quite a long ways from installing this on your roof cost-wise. You still have to put the solar cell in a module, then install it in a panel, then install the panel on your roof along with a rectifier (since your house expects AC) plus other equipment and power storage if you want to be competely off-grid - there are costs, of course, each step of the way.

      The rule of thumb I came across when I was studying the econ of solar cells ~18 months ago was that for thin film cell solar to be viable (without govt subsidy) it had to be manufactured for $1/pW (or one euro, depending on exchange rate) and had to have at least 10% efficiency. If the 10% efficiency is not met then the downstream costs eat you alive because you have to install so much more area of solar cells to get the required power.

      The current advances in flexible solar have been excellent and the solar market is growing at ~30% (although still >90% c-Si cells), but unless you are willing pay a price to be "green" or your govt gives you a fat subsidy for installing the solar power it will take you many years to repay your capital - on the order of 10 or more if you currently have ready access to the power grid. If you are remote from the grid, solar is actually a great deal cheaper today - but by using Si-based solar which is manufactured on relatively large scale today and has 15% efficiencies versus thin film.

      Govt subsidies are still going strong in Japan - Germany is wavering. With G(lobal) W(arming) Bush in office the increase in solar in the US is going to be from the Eco-minded willing to take a bath $$-wise or off grid applications - well, there are also cats who are pretty good at utilizing passive solar power.
    • Let's say it's 1 Euro/watt. That's about $1.33 USD/watt, or about $1,330/kW.

      The next factor to consider is the solar insolation [solarseller.com] for your area. This tells you how many hours of direct sunlight you get, for your area, each day. In my case, the annual average is about 4.5 hours / day.

      At that rate, 1 kW of photovoltaics will give me about 4.5 kWh of electricity, per day, on average.

      Also in my area, electricity is about 7 cent/kWh. Consequently, that 1 kW PV array will save me about 31.5 cents/day, on ave
  • Without even glancing at the article (this IS /.) I'm curious how this is different than the rollable flexible solar cells that have been on the market forever.

    I can buy them at canadian tire, thats how common they are. Product # 11-1575-0 for example. (might neet to enter a postal code, v1p1c7 works.)

    Maybe they are more efficient or something? These seem about the same as a rigid solar panel for the size. More expensive though obviously.

    FINE, I just looked at the article..seems the only advantage is th
    • FINE, I just looked at the article..seems the only advantage is they are expected to be dirt cheap. I've heard that before. I'm still waiting to wallpaper my house in transparent OLED film :)

      I've got my north wall wallpapered with an OLED screen broadcasting a white image and my south wall wallpapered with solar panels to catch it all.

      I hereby claim prior art for all the future perpetual motion/infinite energy machine creators who attempt to patent my brilliant idea.
  • As I remember, the concept was that they could be draped across roof-tops and whatnot. Never heard anything after that.
    http://www.atsautomation.com/solar_technologies/d e fault.asp [atsautomation.com]

    SSP as mentioned on Slashdots pior story for having solar "denim" has small flexible solar panels avaliable now in Canadian Tire. Not that this helps those of you not in Canada... But you can buy them now.
  • Any reasonably useful photovoltaic system is going to need about 1kW output under typical conditions. So with this material, for around $1000 you can generate maybe 50 cents worth of electicity each day. Obviously you aren't going to get rich by selling power back to the grid with a scheme like this but 1kW of totally free power would be kind of nice to have.

    I always thought that a cool thing to do would be to use the excess electricity from PV cells to crack water and make Hydrogen gas rather than goofing

    • Yes, you will get rich. If a $1000 investment yields $0.50 per day worth of electricity on average, then that results in $182.50 per year in revenue. Assuming no maintenance, land, installation, or other overhead costs, you are earning 18.25% yearly on your investment. It would be like printing money!

  • Electricity is only a small part of the game (Score:3, Interesting)

    by dr.Flake (601029) on Sunday December 19 2004, @05:03AM (#11129007)
    What amazes me is that all this investment time and "energy" is spent on cells that produce electricity.

    Whereas the collection of Heat is as simple as it can get, but rarely used.
    Though most mediteranian countries use solar heat for heating their domestic water, but that is about it.

    What i have in mind is the use of solar heat, collected during summer, to warm domestic homes during winter. (Thats where real amounts of energy (read CO2) are needed !)
    Water is an exellent storage container for heat and is dirt cheap.

    The only problem is where to store all the warm water. Probably the easiest solution would be to pump up ground water, heat it, and pump it back. (The ground is actually an exellent therman insulator!)
    Use the 1kW of solar energy from a couple of M2 of these cells to make water run through 100 m2 of cheap solar heat collectors.

    Now we are SAVING evergy.

    • Re:Electricity is only a small part of the game (Score:5, Interesting)

      by TheLoneCabbage (323135) on Sunday December 19 2004, @06:35AM (#11129224) Homepage
      Most solar researchers in this veign are using Sodium Cloride (table salt). It has a much higher specific heat than water. Tends to be less explosive when heated to 600c (you really want to build your house on top of an aging steam boiler with the equivalent energy of dynamite?), and is even cheaper than water and dirt (water aint cheap where I come from)! When molten it's conduction of heat is so efficient you don't even need pumps, it's own confection currents do the work for you.

      Now you just need a near perfect insulator and your all set. (say an underground tank insulated with airogel)

      The real trick isn't in just heating homes though. It's also running things like ovens and stoves. For that your going to need a liquid that stays a liquid between -10c and 250c, without dangerous pressure build up, freezing, corroding or screwing up your pumps. (and it can't pollute the environment when it leaks)

      Once you can safely transport high temperatures 2-3 times boiling point, you can do some pretty amazing things. Like running your A/C from the heat well. (two sterling engines hooked up to eachoter in reverse) Water pumps, air tools, and electrical generators (40-50% efficient in sealed systems like sterlings, but much higher for open ended boilers. The trick as you put it is to avoid converting the energy from one form to another untill it's absolutly necesary.

    • QTFA:

      "Kroesen's team has made its solar cells bendy simply by making them thin. But this has involved a trade-off. While the best solar cells are now working at efficiencies above 20%, the H-AS cells are only about 7% efficient. The researchers think efficiency is worth sacrificing for a cell that is going to be more generally useful, though they still hope eventually to reach 10% efficiency."

    • Allready the quite low efficiency of traditional solar cells makes their use in many applications too cumbersome, so the fact that these are flexible is not likely to help with the lower efficiency as the surface area will start to get very big.

    • I wonder how the efficiency of these panels compares to the more conventional ones. I can't help but think that there's probably a difference; but if it isn't too bad, they could prove to be pretty useful.

      At the moment it's around 7% which is a little bit lower than conventional solar cells which have an efficiency of around 20%.
      But they are working to get it to 10%.
      Second, they can produce it for 1 a watt.
      Which means that it's 8 to 10 times cheaper than conventional solar cells.
    • How durable is it? If it got ripped, would it work anymore?

      Could you grab a roll and keep it round the house, then just cut strips off and make things with it?

      And 1 euro per watt... WTF? How many cubic meters of fabric in a watt exactly?

    • Actually, the biggest obstacle is making them efficient in the first place. A solid panel made of crystalline cells can only get between 11% and 14% efficiency (thin film PVs gets even less), when optimally tilted towards the sun. This is because only certain wavelengths are allowed to be converted into energy at the moment. Scientists are still working on a molecule or bunches of molecules (I'm not entirely sure how it all works) that will be able to utilize more of the spectrum. Until then, we are stu
      • Your post made me remember something that I was wondering about a while back but never found an answer.

        Since Infra-Red radiation is part of the electromagnetic spectrum and very near the wavelengths of visible light, can it be focused using an optical lens just as one can focus light rays?

        I had an idea about placing a fresnel lens in front of a large low-availability IR radiating source and focusing it to make a hotspot. A small area with an extremely high temperature is much more thermodynamically useful

    • TFA talks about the product entering mainstream production in a couple of years. You can purchase the Iowa Thin Film solar cells now. They're about 7% efficient, as they claim. They're not expensive, and you can get them at a number of distributors. [iowathinfilm.com] I've personally used Jameco and Sundance Solar.

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