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Holographic Solar Collectors 189

Posted by ScuttleMonkey from the bright-idea dept.
An anonymous reader writes "The MIT Technology Review is reporting that Prism Solar Technologies has developed a technique to use holograms to concentrate light onto photovoltaic (PV) cells. While the implementation is only about a 10x increase over PV cells without collectors such as mirrors/lenses (mirror/lens approaches can do 100-1000x), it is a great deal simpler, more compact, and cheaper. Also because of the concentration, there is less need for physical PV cell real estate compared to crystalline PV silicon cells of similar output."
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Holographic Solar Collectors More

Holographic Solar Collectors

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  • Only 10x? That's huge! (Score:5, Interesting)

    by chriss ( 26574 ) * <chriss@memomo.net> on Tuesday April 25, 2006 @06:34PM (#15200902) Homepage

    10x increase for the holographic cell may sound bad compared to 100x-1000x for mirrors/lens. But in the installations I know that use mirrors or lenses they take up most of the area. If 10% of the whole surface was PV cells and 90% were e.g.. mirrors (a very conservative assumption, I think the PV cells will cover less then 1%) you would gain an effective increase of 100x instead of 10x. (This is not entirely true, since these new PV cells are only part energy creating silicon, most of their surface is just the holographic lense. But still a massive space saver compared to classical mirrors.)

    Plus you will usually have to place mirrors on the ground due to their weight and the weight of the motors attached to them to make them follow the sun. In contrast you can place PV cells on almost any surface, although you will loose a lot of efficiency if you can not orient them towards the sun.

    If you completely ignore that there are theoretically more efficient methods of concentrating the energy onto PC cells, you still get a 10x improvement over the typical installation (on a roof, with no fancy mirrors at all). And then 10x is huge.

    • 10x input != 10x output (Score:5, Insightful)

      by EmbeddedJanitor ( 597831 ) on Tuesday April 25, 2006 @07:10PM (#15201111)
      Silicon solar cells are still too damn expensive and power hungry to manufacture to be a useful mainstream generation tool. The only places they're really being used is where mainstream supply is not available/practical or where they are heavily subsidised for political/marketing ends. Increasing concentration to reduce the silicon are does reduce the amount of silicon and therefore potentially reduces the $ per W. However...

      PV efficiency reduces significantly with increase in temperature (which is why you see solar racer folk pouring water on the PV panels). Thus just cranking up the sunlight by concentration does not give a linear increase in output. PV cells for concentration thus need to be made thicker and differently (to code with the extra current, heat sinking etc.) but hopefully the payback is still there.

      Personally I think the PV quest is being approached incorrectly. There's too much emphasis on efficiency. Labs try to out % eachother and the big solar showcase is the solar race which is all about high efficiency cells.

      What they should target is $ per Watt because that is the real hurdle to making PV viable. Who cares if it's only 5% efficient, so long as it is cheap? Tile your house with the stuff to get the area.

      • Re:10x input != 10x output (Score:5, Informative)

        by trixillion ( 66374 ) on Tuesday April 25, 2006 @08:11PM (#15201479)
        From the article it is clear that this technology is specifically designed to address two of your concerns. Admittedly it helps to have a background in physics in order to understand some of the concepts (particularly the optics.) Firstly, the holographic lens and waveguide have been designed to direct certain ranges of wavelengths to the silicon and the other wavelengths away from it. This helps to prevent overheating of the silicon cells. Secondly, the lens system is there in order to collect more light per area of silicon used. This causes the $/Watt to increase, while the efficiency (Watts converted per Watt theoretically availlable) remains the same (well, in a perfect world, it sounds like this will work significantly better in their second generation.)
      • http://news.com.com/A+high-tech+way+to+defrost/21 0 0-11395_3-6061333.html [com.com]

        "We built a solar cell made of ice," he recalled. "While it is not as efficient as a silicon solar cell, it costs a penny a square mile."

        We can make super cheap photovoltaics, but you have to factor in usability. There's a very limited part of the world where you can use a solar cell made of ice.

        Also, silicon solar cells aren't going to get any cheaper in the near future. The demand for polysilicon has been booming and (like oil) the r

      • cost per watt (Score:3, Informative)

        by maino82 ( 851720 )
        the article states that they are shooting for a price around $2.4/watt, which I can assume ytou is well below what we are currently paying. i was recently quoted a price of $8/watt from solarsave (http://www.solarsave.com/ [solarsave.com]) for a pv installation, so having to pay a third of that price is extremely reasonable from a cost per watt perspective, even if you don't get any added efficiency due to heat losses.

      • Re:10x input != 10x output (Score:5, Insightful)

        by syphax ( 189065 ) on Tuesday April 25, 2006 @09:36PM (#15201804) Journal
        Who cares if it's only 5% efficient, so long as it is cheap? Tile your house with the stuff to get the area.

        You are almost absolutely correct. Except for two things:

        1. Low efficiency leads to higher indirect costs- specifically, the infrastructure that holds the cells and connects them to the grid. As you get down to lower efficiencies, these costs become significant.

        2. Even at 10% efficiency, you need a huge area to produce a significant amount of juice. Sure, we could in theory generate all the energy we need in the U.S. by covering "only" around 1% of the U.S. land area with 10% efficiency PV (practical issues aside), but that still works out to be a huge area. Like, say, Maine. So even if we had a nice, cheap, low-efficiency solar technology, it's usefulness would ultimately be limited by land use constraints.

        • 2. Even at 10% efficiency, you need a huge area to produce a significant amount of juice. Sure, we could in theory generate all the energy we need in the U.S. by covering "only" around 1% of the U.S. land area with 10% efficiency PV (practical issues aside), but that still works out to be a huge area. Like, say, Maine. So even if we had a nice, cheap, low-efficiency solar technology, it's usefulness would ultimately be limited by land use constraints.

          I'm sure the black tar roofs (houses) or flat commercial

        • Sure, it would take an area the size of Maine, but how much land is already covered by one of the following?

          1. Rooftops
          2. Parking lots
          3. Paved roads

          I'd wager it's close to the area you need, and covering any of the above with solar panels would have little to no effect on anything, since the roads/roofs/lots are already nicely free of plant life that might want to use the sun.

          No reason not to stick a little 400w wind turbine on every other streetlight pole, either.

          The big limit is financial, and this solar

          • Rooftops

            Substantial. People have actually looked at this, but I don't have the numbers at my fingertips. It's a big number, but I think that when you filter out for the ones that could realistically have panels on 'em, it is only a pretty big number.

            Parking Lots

            This is my personal favorite. However, you'd need to build the infrastructure to hold the panels off the ground, which adds not insignificant costs. So in this case, efficiency is a strong driver of overall costs.

            Paved roads

            There are lots of prac
        • I always think about solar power while on the freeway... here in CA it's the 405 and the 5 freeways that do it for me... 12 car lanes of completely open space traveling hundreds of miles up and down the state, with a lot of already built infrastructure, ie: wiring, conduits, maintenance terminals, etc.

          Covering over the freeways with a half tube grid of cheap material... put up solar cells in grid cells where they make the most sense, let light, air and weather filter through the rest... feed it into the loc
      • Given that in most places we want power we also want hot water.
        I'm not sure why they don't combine PV Solar with absorption panels linked to a heat pump and the hot water system, or heat the pool.

        Finding uses for heat, in most building isn't all that hard.

        Deal with PV's problems by teaming with other technologies instead of trying to solve all the problems in isolation.

  • No space savings (Score:2, Informative)

    by Anonymous Coward
    they just replace sections of PV cells with this hologram stuff-- the panel is the same size, just less silicon
    • It won't save any space compared to regular PV cells, but assuming that area of holorgam is cheaper than area of silicon (The article implied that), then it will save money.

  • Holograms? (Score:5, Insightful)

    by exp(pi*sqrt(163)) ( 613870 ) on Tuesday April 25, 2006 @06:39PM (#15200924) Journal
    These sound like good old fashioned diffraction gratings to me. 'Hologram' sounds like nothing more than a marketing term. One disadvantage of using diffraction gratings is that the amount of bending is wavelength dependent. And it seems like the marketing department managed to put a spin on that too.

    • Re:Holograms? (Score:5, Interesting)

      by chriss ( 26574 ) * <chriss@memomo.net> on Tuesday April 25, 2006 @06:43PM (#15200954) Homepage

      Since you can create multiple refractions inside a hologram, you can create a much better lense than with diffraction gratings. So while both are basically flat lenses, the holographic version is much more efficient.

      • many diffraction gratings are holographic (Score:3, Interesting)

        by Anonymous Coward
        Um, hey guys. I think you'll find that many high quality differaction gratings [google.com] are in fact *holographic.*

        When it comes to making diffraction gratings, phase-delaying gratings beat out amplitude-reducing gratings (parallel opaque parts) for transmission. It's easy to make both phase and amplitude gratings with an interferometer (to make fringes) and some holographic film. For phase gratings, you just bleach the film/plates after you wash them in developer and before you use the stop bath.

        Three dimensional g

    • Comment removed (Score:4, Funny)

      by account_deleted ( 4530225 ) on Tuesday April 25, 2006 @06:45PM (#15200968)
      Comment removed based on user account deletion

    • Re:Holograms? (Score:3, Insightful)

      by thePig ( 964303 )
      And it seems like the marketing department managed to put a spin on that too
      Not sure whether that is a spin. Heating is a real problem for Solar concentrators.. A lens will concentrate light, but also IR. These are quite high temperatures we are talking about. If they can actually take out IR from the question, then this indeed is a good idea..
      Also, I can see pratical applications on window sills etc. In our place, temp can go up to 110. Think of a cheap window which will let in only light (similar to th
    • One disadvantage of using diffraction gratings is that the amount of bending is wavelength dependent.

      One man's disadvantage is another man's cooling system. Since the solar cells are also wavelength dependent, the goal is to collect all the usefull light and let the rest (mostly) pass harmlessly through the glass plate. Very clever.

  • Solar collecting is good. (Score:4, Insightful)

    by crazyjeremy ( 857410 ) * on Tuesday April 25, 2006 @06:40PM (#15200930) Homepage Journal
    When you can concentrate the suns energy the collector is more efficient. This is a VERY good thing, especially considering the amount of cloudy / rainy days most places have. Lots of people do not go solar because it simply does not draw enough power for the amount of money they have to use to build the system.

    • Re:Solar collecting is good. (Score:5, Insightful)

      by shmlco ( 594907 ) on Tuesday April 25, 2006 @06:48PM (#15200991) Homepage
      "Lots of people do not go solar because it simply does not draw enough power for the amount of money they have to use to build the system."

      I can see solar as a potential option for some businesses, but for home use you still have the small problem of no power output during the night. And that's usually just when you want some lights, television, heat, and so forth.

      If they want solar to REALLY catch on someone is going to need to develop not just a cost-effective solar cell, but also a cost-effective way to store and reuse the energy collected during the day.

      • Re:Solar collecting is good. (Score:4, Funny)

        by Glonoinha ( 587375 ) on Tuesday April 25, 2006 @06:54PM (#15201027) Journal
        If only there was a way to store all that electric power. Maybe massive plates of lead and zinc in a acid solution, in big heavy square things with little plugs on top to add distilled water from time to time (I have no idea why, but I envision that there would be a good reason to do so on my mythical device.) Give it a catchy name like 'Deep Cycle Truck Battery' and sell them at Wal*Mart for ~$50 apiece, letting us fill an entire room with them for under a thousand dollars.

        Someone should invent that.

      • Re:Solar collecting is good. (Score:5, Interesting)

        by networkBoy ( 774728 ) on Tuesday April 25, 2006 @06:58PM (#15201043) Journal
        Since plain ol solar will never meet our energy needs, just use the grid as a storage device. Durring the day the grid is fed by solar energy with the shortfall made up of anything else available, at night the total demand for energy is lower so those same reserve sources can feed the grid. If there ever is a time that our entire grid can be solar (I doubt highly that this will ever happen) then you can charge a kinetic sourcew against a gravity well* or charge a massive flywheel with the excess power.
        -nB

        * for example pump water up a mountain to a storage lake and let it run down durring the night for power
        -nB
        • "for example pump water up a mountain to a storage lake and let it run down durring the night for power"

          Okay... just for what it's worth, have you ever been to the Hover Dam? Ever seen the amount of water that goes through the turbines each day? Assuming, or course, you're not in Kansas or Indiana or some place lacking in available mountains.

          Or considered just how many flywheels you'd need, and how large they'd have to be, to power an entire city for a night.

          Not saying your ideas aren't practical, but...
        • a pump storage facility which pumps water up a hill is operational in wales and connected to the national grid in the UK

          it is used to balance out extreme loads reacting quickly to smooth out demand so that more power stations are not kept idling

        • "* for example pump water up a mountain to a storage lake and let it run down durring [sic] the night for power"

          FYI: For those that think that this is just a random idea that networkBoy made up, http://www.nypa.gov/facilities/blengil.htm [nypa.gov] and http://www.nypa.gov/facilities/niagara.htm [nypa.gov] are examples of where this has been done for years.
      • Most enviromentalist don't advocate pure solar, they advocate using it the take strain off other systems, I look at AC in the desert as big strain to be removed.

        Put a solar farm on several people's roofs, put a wind farm here and there, coastal cities get wave generators, and everything else can be nuclear. That is the future, not pure solar.

        If this new system could be inmproved to focus the light to a small line I wonder if panels could be hid inbetween roof shingles? Removing the ugly factor entirly

        • I agree, except you missed one major change in the energy usage: population decline. The rate of change from efficiency based on fossil to other sources may be too high. So, the populate is affected through a massive price shift for most goods and transportation. I believe most folks will eventually conclude that energy resources can only come up so far, the rest is bringing down need to match.

          There's only so much "getting off the [old] grid" one can do, and when? Most folks agree that "not no
      • That's what grid-connected solar arrays are for. You use the grid as your battery. In California at least, with a grid-connected array, PG&E buys any surplus electricity you generate during the day (while you're at work and the sun is shining) for the more expensive daytime retail price and when youg et home and actually consume, you buy back from the grid for the cheaper, night time price.

        • "You use the grid as your battery."

          But it's not a battery. Yes, you may be able to sell some excess power to the "grid", but the "grid" doesn't store energy, it just distributes it. As such, a power station connected to the grid still needs to be able to supply ALL of the energy everyone needs at night.

          So at night solar has issues. In fact, it's not too great on cloudy, snowy, short winter days either.
          • There is a 'power station' not far from me [wikipedia.org] which monitors demand on the grid. When there is a low demand, the price of electricity goes down[1] and the buy it. They use this electricity to pump water up a hill from one reservoir to another. When the demand goes up, so does the price of electricity. They open a valve and let the water through some turbines, generating electricity which they sell back to the grid.

            It takes a few hours (at least) for most power stations to significantly alter their outpu

            • "While the grid might not be a battery, it certainly contains some fairly large ones."

              The operative word in that sentence being "some". Given all of the electrical grids on the planet, it looks like about three-four dozen or so are pumped storage systems. I also liked the following quote: "In 2000 the United States had 19500 MWe capacity of pumped storage. This produced a net -5500 MWe of power because they consume more power filling their reservoirs than they generate by emptying them."
              • This produced a net -5500 MWe of power because they consume more power filling their reservoirs than they generate by emptying them.

                Right, which is why they work as load-balancers and promote financial efficiency rather than actually promoting power efficiency. Thankfully the main generating systems have already tied financial efficiency to their, somewhat more fluctuating power efficiency, so it all works out.
      • Solar power HAS really cought on in some parts of the world though...like Germany. Germans can sell solar power back to the grid and actually make a profit. A lot of people are renting out the roofs of some farms just to put solar cells on it and feed it back to the grid. In a way Germany is subsidizing the solar industry for the rest of the world (at least until the refined silicon shortage is solved) because they are driving the industry right now.
      • If they want solar to REALLY catch on someone is going to need to develop not just a cost-effective solar cell, but also a cost-effective way to store and reuse the energy collected during the day.


        In developed areas, at least, there is already an easy way to do that: use the power grid as your energy store, by selling power to the grid during the day and buying it back again at night.

      • I can see solar as a potential option for some businesses, but for home use you still have the small problem of no power output during the night. And that's usually just when you want some lights, television, heat, and so forth.

        If they want solar to REALLY catch on someone is going to need to develop not just a cost-effective solar cell, but also a cost-effective way to store and reuse the energy collected during the day.

        This is a non-issue. The technology and legislation addressing this has existed for nea
        • "You sell power to the power company when generating, and you buy it back when you're not generating. Simple."

          Simplistic, you mean. Repeat after me: The grid is not a battery. Yes, you may be able to sell some excess power to the "grid", but the "grid" doesn't store energy, it just distributes it. You can't buy "your" power back again.

          So to repeat, a power station connected to the grid still needs to be able to supply ALL of the energy everyone needs at home on a cold night.

          "Come on people, do you honestly
          • Simplistic, you mean. Repeat after me: The grid is not a battery. Yes, you may be able to sell some excess power to the "grid", but the "grid" doesn't store energy, it just distributes it. You can't buy "your" power back again.

            So to repeat, a power station connected to the grid still needs to be able to supply ALL of the energy everyone needs at home on a cold night.

            Fortunately, the amount of power needed at night is far lower than that needed during the day. Other power generation mechanisms are sufficient
            • "If you want to go all-renewable, wind could provide the left over power needed at night."

              Another source that works well only under limited conditions (when the wind is blowing) and only practical in specific locations (where there tends to be a lot of wind). Like solar, both can help, but neither can be depended upon to provide and maintain constant baseline loads.

      • > If they want solar to REALLY catch on someone is going to need to develop not just a cost-effective solar cell, but also a
        > cost-effective way to store and reuse the energy collected during the day.

        Agreed. Flywheels seem like a nice solution to that problem. Of course, next thing we'll know they'll be writing about "torque pollution" ;-)
      • nah you just join the roof-exchange program, where you put your solar cells on somebody's roof the other side of the planet (where it's light when it's dark for you), and they put theirs on yours. The most convenient option is to drag a cable from them to you (through the earth is the shortest route), but if that's too expensive for you (with the electicity savings, it won't be for long) they simply send you the electicity by shipping batteries they've charged to you. Simplicity.

      • Re:Solar collecting is good. (Score:3, Insightful)

        by Anonymous Coward
        You need to physically go and see some houses that have "whole house" solar installations, talk to the people there. Sigh... I can yammer about it all day long, say I lived with it for years, that the battery banks (cheap normal flooded lead acid storage batteries) could go for four days with heavy clouds, that on sunny days the batteries would be fully chrged by 1 PM in the afternoon despite heavy usage, that the payback period is less than ten years, etc...it won't do any good. Not a damn bit of good, Thi
      • Here is the deal...

        When solar cells are used, they are feed directly into your houses power supply and any excess electricy produced goes back into the power grid. Not stored in batteries.

        This seems rather odd, but when electricity goes back into the power grid, it spins your meter backwards. Anytime your meter goes backwards, you get cash back from your power company.

        Soo... You are still depedant on your local power grid for nightime power, but perhaps that might change for people who want to not have anyt

  • So many stories but where are they? (Score:4, Insightful)

    by Zaai ( 817587 ) on Tuesday April 25, 2006 @06:40PM (#15200934)
    Pardon me for being sceptical about the actual commercial feasability of this.

    Over the last decade quite a few of these wonderful improvements have been announced yet the commercially available solar-cell still has an efficiency of less than 15% and the price hasn't changed that much either.

    I wonder if these announcements are more motivated by an upcoming investment round...

    God knows we could use them, but when do we get to see them?

    • Re:So many stories but where are they? (Score:4, Informative)

      by crazyjeremy ( 857410 ) * on Tuesday April 25, 2006 @06:46PM (#15200979) Homepage Journal
      Products like this decrease the amount solar panels needed. Many of the wonderful improvements are available, but at a very high cost. This development specifically reduces the cost needed to attain the same amount of power.
      • I believe you probably meant this, but your wording is a bit misleading.

        You still need the same number of *panels* with this new technology. They are not more efficient per area than normal panels built with the same type of silicon, and probably slightly less due to loss in the diffraction.

        But you need less silicon per panel, since most of the panel is just a cheap holographic diffraction grating that directs light towards the small strips of silicon.

        You'll still need your whole roof, or whatever-- but it
  • In their ability to concentrate light, holograms are not as powerful as conventional concentrators. They can multiply the amount of light falling on the cells only by as much as a factor of 10, whereas lens-based systems can increase light by a factor of 100, and some even up to 1,000.

    What's stopping me using a holographic collector in conjunction with a mirror/lens affair? Use mirrors/lens' to angle 100 - 1000 times more light energy on to the hologram .. That, presumably, would get the cost down yet furth
    • What's stopping me using a holographic collector in conjunction with a mirror/lens affair?

      That would be innovative... and they have this thing designed to stop that kind of stuff.

      It is called a 'patent'.
    • What's stopping me using a holographic collector in conjunction with a mirror/lens affair?

      Why use a mirror lens when you can replace it with ANOTHER holographic collector?
    • The problem with concentrating the light too much is it generates more heat. Like a computer heat causes problems it reduces the efficency of the solar cell. Also the heat increases the rate the cell degrades and will have to be replaced more oftain. 10x is a reasonable amount of concentration because it does not significantly reduce efficency and does not stress the chip.
    • The issue here is the holograms are a replacing the mirrors/lenses. The actual photo cells are still the same.

      The idea here is the holograms could be made flat while mirrors you'll have to link up with motors to track the sun.

      If you have mirrors already tracking the sun, then you don't need holograms to redirect the light to the photo cells.

    • Re:Alternative to each other? (Score:2, Informative)

      by Anonymous Coward
      Concentration is highly overrated from a cost standpoint. A typical solar cell runs about $3/peak watt produced at 1 sun illumination. A 10 to 1 concentration ratio would reduce solar cell area to $0.30 if you could continue to use the same cell and it can handle the concentration. You have achieved 90% of the possible cost reduction for the solar cell. A 1000 to 1 concentration ratio only buys about you another 29.9 cents or so cost reduction of the cells and you have to pay for a much more complicated

  • Hologram, eh? (Score:5, Funny)

    by LochNess ( 239443 ) on Tuesday April 25, 2006 @06:46PM (#15200984) Homepage
    Finally, a use for Arnold J. Rimmer.

  • Promising... (Score:3, Interesting)

    by dakirw ( 831754 ) on Tuesday April 25, 2006 @06:47PM (#15200988)
    Anything that can provide decent solar generation more cheaply would be good. Sounds like their process improvements in the 2nd gen panels might meet the $1.50/watt figure mentioned in the article. In any case, costs of any solar tech will need to go down quite a bit to support more widespread use, especially in developing countries.

    • Re:Promising... (Score:3, Insightful)

      by Jeremi ( 14640 )
      In any case, costs of any solar tech will need to go down quite a bit to support more widespread use, especially in developing countries.


      The other possibility is that the price of the alternatives might go up. If that happens, then solar will look more attractive even at its current pricing.

  • Or was all of that just a bunch of BS?
  • They should just make a giant hologram of the sun. Then we'd have perpetual energy.
  • Perhaps someday they will become efficient enough that it will be cost effective to build arrays several dozen miles square on the light side of the moon and then beam the energy back to earth as microwaves. In the absence of some sort of major breakthrough in fusion energy production, that seems like the way to go for clean energy.
    • Light side of the Moon? Hunh? The lunar "day" is somewhere around 28 Earth days...fixed installations will be in shadow approximately 2 weeks at a time, and at unfavorable angles for some of the other 2 weeks.

      Or do you mean build rails all the way around the Moon and motorize the panels so they can stay on the "light side". Or maybe position at the poles (too lazy to google it...does anybody know the axial tilt of the Moon? shallow enough to stay out of shadow at the poles?)

      Better yet, unless you're p
    • Thats a great idea.

      And then when Bush Jr. Jr. Jr. decides that he doesn't like [bad country here], he'll just tell the opperators to point the giant microwave systems at [bad country] country for a while.

  • We used a similar product in 2001 (Score:5, Interesting)

    by goldarg ( 227346 ) <john.meatkite@com> on Tuesday April 25, 2006 @07:17PM (#15201156) Homepage
    Back in 2001 the Tucson Citizen did a project where they powered a Sun Colbalt Qube 3 off of solar power using a set of panels based on a very similar if not the same technology.

    The panels they came from a company called TerraSun and the one I have on my desk left from the project looks remarkably like the one in the article.

    Archive.org still has some pages from the site which is long defunct http://web.archive.org/web/20010807151516/www.sola rexplorer.net/gallery/index.php?TopicID=panels [archive.org]

    Google finds reference to the technology that TerraSun was developing http://www.wapa.gov/es/greennews/2001/may14'01.htm [wapa.gov]

  • How about Fresnel lenses? (Score:5, Interesting)

    by dinther ( 738910 ) on Tuesday April 25, 2006 @08:02PM (#15201417) Homepage
    Concentrating light onto PV cells has been done before. The main problem is that the PV cells get too hot and degenerate quickly. Bulky panels using mirrors or lenses can be solved using flat fresnel fenses. Now the question remains, how to cool these things. It dawned to me that the panel created so far is in fact very similar to the solar water heaters. Why not combine the two? A fresnel lens concentrates the light onto a PV panel that is protected against heat by water flowing up between two layers of glass (Hot water rises) circulating as it does in traditional solar hot water systems. The water takes out the heat producing IR radiation leaving all the good electricity generation radiation for the PV panel. This way you can put up one panel producing both hot water and electricity.
    • I've always wondered why they didn't do something like that. You would want the water on the back of the cells though so it doesn't absorb any of the incident energy.
    • I actually asked a similar question to a PV install vendor here, since our desert temperatures are around 45 Celsius during the day. This reduces the output of panels (which are rated at 25 Celcius) significantly, and it would seem ideal to cool the panels with water and pre-heat your hot water system, spa, etc.

      The problem is, if you are grid-tied or have a certified installer work on your system, they are extremely reluctant to even talk about mixing liquids with electricity. Often they tie the panels
    • IANAOE, but an obvious solution would be to use selective mirror, prism or diffraction grate to permit only the wavelengths tho which the PV cells are sensitive through. In particular they could eliminate the IR portion - IIRC no PV cells are really sensitive to this section of the spectrum.

  • Pointless. (Score:3, Interesting)

    by zippthorne ( 748122 ) on Tuesday April 25, 2006 @09:39PM (#15201813) Journal
    This scheme removes one of the principle benefits of photovoltaic power: namely that it's omnidirectional: it'll still have a decent energy production even if the light source is diffuse. like.. say.. light, but full cloud cover (seems half the weather in the NE is light full cloud cover...) or fog. if you're going to bother lensing the light, you might as well use a solar collector to drive a heat engine, which is far more efficient than PVs are right now.
  • The fact that these panels are much cheaper to develop and output the same power as a conventional PV panel is where its at. If they can get the price down to $1.50/W, it starts to look really appealing. For an installation of 10 200W panels (2kW), you're looking at saving $2000.

    One of the other factors with this panel is that it brings down the net carbon impact of the devices. It takes less energy to produce these panels, so the breakeven time is much shorter than on a conventional PV panel.

    However, the b

  • One interesting aspect is that these things seem to be pleasant to look at.

    Aesthetics are an important issue for solar collectors, because if we want to generate any significant amount of power from solar, we are going to be looking at a lot of them. On average, with 10% efficiency, you can generate about 150 kWh per year per square meters. US electric power generation in 2004 was about 4 trillion kWh [doe.gov], so if solar were to provide even 10% of that, we'd need to cover the better part of Rhode Island with ce
    • We already have fore more than 1-2 Maines already being used in the US, they're called buildings. By requiring all new buildings to have a minimal amount of PV cells or solar hot water heating installed, a great deal of power can generated simply through new construction.

      Start off with an insignificant amount per new home, say a 1000 watt inerty system and/or enough solar hot water for 4 people, and up the amount every decade or so until the thing becomes self sustaining.

      After visiting Hawaii I am conv

    • if solar were to provide even 10% of that, we'd need to cover the better part of Rhode Island with cells. If you were to provide 100% of total US energy consumption with solar (no, I'm not suggesting we do that), I think you'd need 1-2 Maines.

      Finally, a use for Nevada/NewMexico/Arizona/Or any of those old Nuclear test sites.

      .... It's Pronounced Nuk-U-Lar ... Homer Simpson or G.W. Bush, I can't recall. Ok, that one is definately G.H. Bush

  • Pyron Solar http://www.pyronsolar.com/US/index.htm [pyronsolar.com] has got a great little system put together that uses fresnel lenses to focus sunlight on high efficiency solar cells.

    They float the entire assembly in water to cool it and to assist in rotation so that the apparatus can follow the sun.

    Our energy problems are licked, I hope.

  • Skeptics: this is NOT just a glorified Fresnel lnz (Score:5, Informative)

    by Starker_Kull ( 896770 ) on Wednesday April 26, 2006 @08:42AM (#15203805)
    My first thought reading the headline was that this was just called a "hologram" to get some buzz, over what is a very generic, straightforward way of increasing the power delivered to the expensive part, the solar cell. But (for those too lazy to RTFA) this is different for three reasons:

    1) It is almost omnidirectional - a Fresnel lens is a flat subsititue for a regular lens, with limited off-axis focusing ability. This seems to use the glass as a lightguide instead, with a broader angular reach (in exchange for limited scalibility - bigger the glass width to thickness ratio, the more light lost because of increased internal reflections & distance from entrance to cell)

    2) It uses a hologram to selectively reject useless frequencies like infrared, which is 80% (IIRC) of the energy of sunlight, but generates no electricity from the cell. In fact, infrared is harmful to the cell, because it increases its temperature, which reduces its effeciency!

    3) Because of the above features, it does not need a turning mechanism to follow the sun, the solar cell (which is the most expensive part) lasts much longer because it is not heated as much even though it is capturing much more useful light and converting that into electricity, it is flat and relatively easy to handle, unlike traditional solar cells with large, bulky, moving "capture" mechanisms placed in front of them....

    In summary, it is cheaper per kilowatt-hr, AND more effecient, AND more practical for installation (no moving parts or seperated pieces). This is pretty neat.

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