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Optical Concentrator To Make Solar Power Cheaper 141

Posted by Soulskill
from the bright-ideas dept.
Al writes "Researchers at a company called Morgan Solar have developed a simple solar concentrator that promises to cut the cost of solar energy. The Light-Guide Solar Optic (LSO) consists of a specially-molded acrylic optic that traps light and guides it toward its center using total internal reflection. At the middle of the concentrator another optic made of glass receives the incoming light, amplifies it and directs it toward a small solar cell at the very center of the device. Unlike other concentrators, the light doesn't leave the optic before striking a solar cell so there's no air gap, and there's no chance of fragile components being knocked out of alignment. This could significantly reduce the cost of manufacturing this type of solar cell."
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Optical Concentrator To Make Solar Power Cheaper

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  • Cool (Score:5, Interesting)

    by Hatta (162192) on Saturday February 21, 2009 @01:27PM (#26941815) Journal

    That's actually pretty cool. By concentrating the light, they need less photovoltaic material per square foot of land used for solar. I'm curious how the efficiency of photovoltaic cells varies with the concentration of light. Will 1 square foot of sunlight concentrated into a few square inches of photovoltaic cells produce as much power as 1 square foot of unconcentrated photovoltaic cells?

    • Re:Cool (Score:5, Interesting)

      by Skapare (16644) on Saturday February 21, 2009 @01:34PM (#26941879) Homepage

      The efficiency actually goes up relative to PV material in straight unmagnified sunlight. I'm sure there's a saturation point where that stops. This is one reason concentrating light on PV is a plus. Of course, the other is that it involves less PV material cost.

      • Acrylic rapidly becomes yellowed when exposed to ultraviolet, and especially under very high-intensity light, even if it has anti-yellowing chemicals added. This article, Applications and Limits of Polycarbonate and Acrylic Lenses [hubbell-canada.com], explains "... yellowing is a sign of degradation of the plastic molecule. Heat and ultraviolet act to break the molecules. This surrenders the intrinsic strength of the material as the molecular structure no longer consists of long intertwined chains but fractured segments. This may be reflected in reduced strength of parts with formed surfaces as these surfaces tend to localize stresses."

        The article, A Cheaper Solar Concentrator [technologyreview.com], referenced in the Slashdot story says, "With a flat bottom and convex, mirrored top, the [Morgan Solar [morgansolar.com]] optic receives the incoming barrage of light at a concentration of about 50 suns and amplifies it to nearly 1,000 suns before bending the light through a 90-degree angle."

        The article does not explain how there is a concentration of 50 times before the light reaches the optics. The article is wrong in using the word "amplifies". The correct word would be "concentrates".

        To have a 1,000 times concentration, the area of the optics must be 1,000 times larger than the area of the solar cell. That delivers 1,000 times the heat, also.

        Morgan Solar's investors page [morgansolar.com] says, "Morgan Solar was incorporated in June 2007 and is currently well funded by a start-up investment from our angel investor and Chairman, Eric Morgan." Apparently the company was funded by the inventor or someone in his family. It says, "Our plans call for securing our next round of investment funding by Q1 2009. If you are a venture capital company or a potential partner-investor interested in exploring investment opportunities with our company, please contact us."

        Was a Slashdot editor paid to allow this story? Did Slashdot profit? Was Technology Review paid to run the story? I think that articles about companies that are soliciting investments should have a statement about whether or not someone was paid.
      • Optical concentration for solar cells using lenses or mirrors is of course old news. They work dandy except for the problem that the more you concentrate the more you have to track the sun's position. Tracking solar cells are an economic non-started except in certain applications.

        Now classical optics says you cannot compress phase space with refractive or reflective optics. Ergo the claim being made is impossible unless they are
        1) relying on non-refractive optics (e.g. scattering)
        2) only gettin a boost n

        • Tracking solar cells are an economic non-started except in certain applications.

          Well, for that matter, solar cells in general are an economic non-starter except in certain applications.

          I think you're a little too down on tracking.

          The whole idea of inventing new designs is to change the economics; hand-waving preconceptions based on old designs are sheer obstructionism when aimed at an economical invention already demonstrated to work. The engineering and production of the tracking components is not so difficult as that of the solar cells themselves. The major components such as servo m

          • by goombah99 (560566)

            I think the assumptions and details of the application of the "classical optics" proof need to be spelled out a bit more. Does the argument cover non-imaging optics? What about optics where the light is concentrated at the edge of the sheet, as in the device in this article, thus having vectors that are in all directions within the plane of the device and a range of out-of-plane directions consistent with total internal reflection? I think the device to a large extent gives up specifying the directions from which the light arrives at the collector, thus being somewhat like the scattering exception to the phase-space argument. If so, this should relax the pointing accuracy needed.

            Louivile's theorem is a harsh mistress. You can't compress phase space.

            • What's your point? Phase space is not space alone but also direction.

              • by goombah99 (560566)

                Consider the plane directly in front of the collector. this plane has a large area. Next consider the area of the detector. this is small. The ratio of these in area is probably something like 1000 since they assume it's 1000 times amplification.

                This means that whatever the acceptance angle of the silicon detector, and lets be generous and assume this is 2pi sr, the acceptance angle of the plane in front of the panel must by louiville's theorem must be 1000th of this. Which is quite a small acceptance a

    • Here's the link ... (Score:5, Informative)

      by Skapare (16644) on Saturday February 21, 2009 @01:39PM (#26941917) Homepage

      ... about concentrating solar power [wikipedia.org].

    • Re:Cool (Score:5, Informative)

      by vsage3 (718267) on Saturday February 21, 2009 @02:01PM (#26942055)

      That's actually pretty cool. By concentrating the light, they need less photovoltaic material per square foot of land used for solar. I'm curious how the efficiency of photovoltaic cells varies with the concentration of light

      For a constant temperature, efficiency goes up logarithmically with light concentration. A solar cell with 1 sun on it is going to be less efficient than one with 500 suns on it assuming you have a way to cool the cells. Past a certain point the efficiency drops like a rock due to lack of cooling the cells and this reduces the voltage you can produce by about 2.3mV/C past room temp.

      • To cool it off maybe you could combine a solar electric system with a solar heating system and pass the cold water under the cells.

    • I think this could have a lot of potential for consumer level portable solar panels, all the portable panels avaible for back packing and bicycleing and whatnot are pretty crappy right now, but this would allow compact sollar devices to be a lot more feasible I think. Also you could remove the lense and use it as a fire starter.
      • Re:Cool (Score:4, Interesting)

        by M. Baranczak (726671) on Saturday February 21, 2009 @02:18PM (#26942173)

        Won't work. This thing has to face the sun directly. Which means that it has to be a fixed installation, and it won't work when it's cloudy.

        The article briefly mentions some other group at MIT that's developing a concentrator that works with diffuse light - so presumably that would take care of both those problems.

    • Increased light concentration means increased efficiency, though it levels off past a certain point. Whenever you see those "most efficient solar cell yet" stories, that was the cell's performance under about 1000x the light level of the sun.

      So you'll actually get a bit more power by concentrating, but there's a flip side - the heat. Solar cells are semiconductors, and semiconductors hate high temperatures.
    • by duffel (779835)

      More, actually... solar cells can actually increase in efficiency at higher concentration.

      This is part of the main attraction of 3rd generation solar cells, such as multijunction, quantum well or intermediate band cells, which are expensive to make but very very efficient, especially at high concentrations.

      Incidentally, there are some companies that already use non-imaging optics as part of their concentrator system, SolFocus [solfocus.com] being one of them.

  • by Almost-Retired (637760) on Saturday February 21, 2009 @01:35PM (#26941885)

    Neat idea, but how do they get rid of the heat of 1000 suns? Does the IR escape because it isn't reflected the same way?

    • Re: (Score:3, Interesting)

      by Colonel Korn (1258968)

      Neat idea, but how do they get rid of the heat of 1000 suns? Does the IR escape because it isn't reflected the same way?

      About 80% of the energy is absorbed across the entire solar spectrum. Yes, it will radiate some heat away as IR, but mostly the heat is convected away by the surrounded air. You're right, though--this is a design concern for these devices, as temperature effects efficiency and lifetime.

    • by mh1997 (1065630) on Saturday February 21, 2009 @02:08PM (#26942107)

      Neat idea, but how do they get rid of the heat of 1000 suns?

      They keep them in the dark so they don't get hot.

      or from wikipedia:

      The solar cells require high-capacity heat sinks to prevent thermal destruction and to manage temperature related performance losses...In May 2008, IBM demonstrated a prototype CPV using computer chip cooling techniques to achieve an energy density of 2300 suns.

    • My first thought was, why are they using a PV cell in the first place, instead of using the heat to drive a turbine?

      • waste heat (Score:4, Interesting)

        by zogger (617870) on Saturday February 21, 2009 @03:21PM (#26942661) Homepage Journal

        Or use the waste heat to drive a stirling engine as a booster perhaps. I know just regular solar panels get wicked hot on the backs of them when sitting in full direct sun, I mean it is black stuff sitting behind a clear surface and stuck on a metal backing, it gets *hot*. Just doubling that heat would turn it into some sort of decent viable optional energy source.

        And why PV? Instant electricity from it, solid state, no moving parts, pretty spiffy stuff. Big solar concentrators with turbines are cool too, we have those for giant megawatt scale production now, but we don't have them for joe homeowner yet or joe back packer, PV fits the bill for those purposes.

        • by evanbd (210358)

          Nope, you don't want to use that waste heat. If you insert a thermal engine in the waste heat path, then for equivalent cooling capacity the solar cell gets hotter. At higher temperatures the efficiency of the solar cell drops rapidly. Since the temperature is low (by heat engine standards) the efficiency of your heat engine will suck anyway; you're better off spending your heat-moving ability keeping the solar panel cool than putting the waste heat to use.

          Short version: heat engines efficient enough to

    • by UttBuggly (871776)

      Neat idea, but how do they get rid of the heat of 1000 suns? Does the IR escape because it isn't reflected the same way?

      I would throw out the idea of a "Tri-brid" power solution.

      1) Solar arrays using a design like the article.

      2) Steam plant, using the heat byproduct of the arrays.

      3) Wind turbines, married to the distribution system with the first two.

      My thoughts on this were concerning the land use efficiency. The Southwest U.S. is ideal for all three in many areas. By co-locating and combining the technologies, you get a near 100% output cycle, assuming you don't get the magic trifecta of no sun, no wind, and insufficient I

      • by ductonius (705942)

        2) Steam plant, using the heat byproduct of the arrays.

        The efficiency of heat engines is governed by the temperature difference between the hot and cold side. Coal and nuclear plants typically have a hot side at around 600 degrees Celsius and newer designs are pushing that higher for greater efficiency. Common glass stats to soften at around 550 degrees Celsius and solar cells start to lose efficiency even at 50C.

        The solar array and concentrator would have to maintain a temperature well below 600C just to avoid melting, so any heat engine run from their waste h

    • I saw a system recently which massively concentrates sunlight onto high efficiency PV cells, which are actively cooled, I think by a mixture of gas and liquid coolant. In other words they are cooled like any other type of engine.
    • Yes, we need a way to get rid of all that heat. After all, heat is the last thing we need when generating electricity; just look at any typical conventional electric generator plant .
    • Well, if you attach your solar cell to a heat sink the same size as the concentrating surface (lens), then you have as much area to dissipate heat over as you have for a normal, non-concentrating panel.

      In other words, the ratio of light collecting area to heat emitting area is the same in both cases.
    • by goombah99 (560566)

      Neat idea, but how do they get rid of the heat of 1000 suns? Does the IR escape because it isn't reflected the same way?

      No problemo. Once it hits 6000 Kelvin, it will be in equlibrium with the sub blackbody and not get any hotter.

  • by Matt Perry (793115) <perry...matt54@@@yahoo...com> on Saturday February 21, 2009 @01:36PM (#26941893)

    From the picture, it looks a lot like a fresnel lens [wikipedia.org].

    • Re: (Score:3, Interesting)

      by Rowanyote (980640)

      There are some key differences. In a fresnel lense the ridges just bend the light passing through a small amount. It is basically the surface of a regular lense stepped into a flat surface. Thus it acts almost exactly like a standard lense and has a focal point somewhere behind that all the light is reflected to.

      From the sound of it, this lens bends all the incoming light 90 degress or more, sending it towards the center through the lens itself to a secondary optic area which concentrates the light and r

    • Re: (Score:2, Informative)

      The one thing I learned about about optics from the elective class I took in college: all lenses look similar, but function very very differently. To evaluate a lens based on how it looks is something like evaluating a microprocessor based on how the die looks.
    • by EndoplasmicRidiculus (1181061) on Saturday February 21, 2009 @06:11PM (#26944125)
      It's not a fresnel lens. The light is reflected internally and concentrated towards the center rather than being refracted towards a focal point some distance away. As always, pictures speak louder than words: http://www.morgansolar.com/images/technology/lgophoto1_full.jpg [morgansolar.com]
  • solex agitator (Score:2, Informative)

    by ByTor-2112 (313205)

    Watch out for the man with the golden gun...

  • Does this thing have to be aimed at the sun? In 1D or 2D? If it needs 2 pointing axes, it's too complex. 1D, maybe; there are trough-like concentrators at Mojave which are driven to move with the sun.

    • It would appear that it must track the sun precisely.

    • Why does that make it "too complex"? Finding the sun is not a particularly hard engineering problem.

      • Doing it cheaply and without having a large ugly array mounted to the roof would be the hard part, especially if they want to use this on homes.

  • My house has an nearly unbeatable infestation of small ants, and I can't help but think just what a magnificent burning lens one of these would make minus the solar chip.

    But aside from that, there are some other pretty nifty uses for concentrated sunlight. I am definitely curious whether the lens can be scaled up to a square meter or more, enough to possibly melt glass or aluminum.

    • by polar red (215081)

      I am definitely curious whether the lens can be scaled up to a square

      You're thinking of solar furnaces, like the one in Odeillo http://en.wikipedia.org/wiki/Solar_furnace [wikipedia.org] (already in production for over 20 years ...)

    • by drinkypoo (153816)

      you can already buy big huge fresnel lenses cheap and then use an array of them to do all kinds of solar concentration.

    • My house has an nearly unbeatable infestation of small ants

      I got rid of a nasty colony of Pharoah ants [terro.com] with the Terro sugar/boric acid liquid bait, drizzled on the outside walls, they came and ate in droves and just vanished within a week.

      Or, you could just demolish the structure and burn it, but I bet the ants would actually survive that and just move away.

  • transmission lines (Score:5, Interesting)

    by bcrowell (177657) on Saturday February 21, 2009 @01:56PM (#26942021) Homepage

    I live in LA. To the east of us is the Mojave Desert, and there's already quite a bit of solar power out there right now [wikipedia.org]. The big issue is transmission lines to get the energy from the Mojave to LA. Building transmission lines requires political action, and that's slow and uncertain because of NIMBY. I have photovoltaics on my roof, but objectively, if you look at the price of land where I live versus the price of land in the Mojave Desert, it's pretty clear where you should be building these things.

    • That's the thing about alternatives. Storage. Also unlike wind solar panels block the ground underneath big time. One has to wonder about the effect if solar becomes a bigger source.

      • I'm thinking effects similar to forest.

        Shade, cooler, a little less evaporation, only shade tolerant bushes underneath.

        Of course you don't want plants overgrowing your solar power plant anyway.

        • Re:Shadow lines (Score:4, Interesting)

          by WalksOnDirt (704461) on Saturday February 21, 2009 @03:37PM (#26942799)

          Of course you don't want plants overgrowing your solar power plant anyway.

          Which is why in actual practice the land under the solar collectors is made as sterile as they can afford to make it. We need to accept that getting most of our energy from desert solar will probably require destroying the ecology of several percent of the deserts of the southwest. I think that's an acceptable trade off, but for those who insist on a "greener" solution I suggest they push for nuclear power.

          • by duffel (779835)
            OK, several things:

            There is not enough fissile material in the world to supply the world with nuclear power.
            Nuclear power is far from green. Consider the waste for one. The effort of mining it.
            Normal power plants tend to make the area under the power plants *completely* unusable... I mean, check out all those buildings in the way.

            Do you really think that solar power use in a desert will have a more pronounced impact on the environment than using, oh, i don't know, coal power in the rest of the countr
            • by jackbird (721605)
              1. Depends how you do it. Thorium and pebble beds being two of the ways to have enough fuel for millennia. 2. Depends how you do it. If you're reprocessing almost all your waste and only have to dispose of a small amount of hot (industrially useful) stuff for a couple of hundred years, it's not so bad. 3. Yes, but since the OP was talking about single-digit percentages of the entire southwestern desert, the footprint of a nuclear plant or fifty is going to be a lot smaller.
            • by Muad'Dave (255648)
              That's funny. Scientific American just had an article [sciam.com] about this. Their data suggests current breeder technology could supply the Earth's current needs for 70,000 years given the NEA's conservative estimates of currently available fuel.

              According to the NEA, identified uranium resources total 5.5 million metric tons, and an additional 10.5 million metric tons remain undiscovered-a roughly 230-year supply at today's consumption rate in total.

              Two technologies could greatly extend the uranium supply itself. Nei

          • by dbIII (701233)

            desert solar will probably require destroying the ecology

            By putting in a road, power lines and some things that shade the ground a bit in a couple of square miles for a huge installation? I don't think you quite understand what you are talking about.

            but for those who insist on a "greener" solution I suggest they push for nuclear power.

            The nuclear debate is effectively dead in the USA until you can find people that will put up vast amounts of money to build things that will not produce anything for a decade

      • by Belial6 (794905)
        I'm thinking it will turn that 30 year roof into a 40 year roof, or that 20 year road into a 30 year road. Maybe extend the life of a parking lot or two....
        • I'm thinking it will turn that 30 year roof into a 40 year roof.

          I'm thinking that any gains in roof covering lifetime are more than cancelled by the penetrations of the waterproof membrane by support legs.

      • Re: (Score:3, Interesting)

        by bcrowell (177657)

        That's the thing about alternatives. Storage.

        Huh? My post, which you were replying to, didn't say anything about storage.

        LA's problem with lack of capacity shows up on hot days in the summer, when everyone is running their air conditioner. That's exactly when the Mojave plants will be running at their maximum production. Because of this excellent match between peak production and peak demand, there isn't really an issue with storage. It's a perfect fit.

        • True for now, but if electric cars ever catch on than you will start seeing another large peak at night when they are charging.

      • by duffel (779835)
        Storage isn't that big a deal until we collect so much solar power that we can't use it up during the day.

        During the day there are massive drains of power because of things like air conditioning or just industrial use that you don't have to worry about storing solar power until you make more than is needed by all those processes.
      • by duffel (779835)
        Well, given that the solar constant is 1 kW per square meter, multiply by efficiency, you can work out just what sort of area you need to cover to supply any given site with solar power - and you'll find that barely any of the united states will have to be covered with solar cells. One or two deserts will do.
        • Your overall point is right, but the gross insolation is about 6kWh/m^2 per day even in the Mojave because the sun isn't usually directly overhead.

    • by FooAtWFU (699187)
      You're probably not going to be building lens-concentrated photovoltaics in the Mojave. Some sort of solar concentrator design (with the big tower in the middle that they aim the sun at with mirrors) or the more-experimental solar chimney designs are better bets and generally much more cost-effective.
    • by rsborg (111459)

      The big issue is transmission lines to get the energy from the Mojave to LA. Building transmission lines requires political action, and that's slow and uncertain because of NIMBY.

      Do you think the $11B in funding for a smart grid [wikipedia.org] will help this effort?

  • by Anonymous Coward
    This should arrive just in time to recharge my flying car. I can hardly wait!
  • by Jane Q. Public (1010737) on Saturday February 21, 2009 @02:05PM (#26942079)
    It's TFA's fault, but even so.

    There is no "amplification" taking place at all, merely concentration. Those are two VERY different things.
  • An unstated benefit (Score:3, Interesting)

    by vandelais (164490) on Saturday February 21, 2009 @02:09PM (#26942113)

    of this particular solar advance means not only greater efficiency and lower cost, but also MUCH MUCH greater feasability for wider adoption by areas of higher latitudes. In addition, this particular advance would appear to reduce the detriment of partial occlusion by some factor.

    This concentrator technology also reduces the manufacturing use of rare metals for these systems and that is another huge benefit also.

  • > optic made of glass receives the incoming light, amplifies it

    I'm sorry, but an "optic made of glass" can not amplify light. All it can do is concentrate it.

    In fact the whole this just sounds like packaging a solar cell and an elaborate magnifying glass to me.

    No net decrease in surface area. No proven increase in efficiency.

    • Re: (Score:3, Informative)

      by pete-classic (75983)

      No net decrease in surface area. No proven increase in efficiency.

      There's a third axis; cost per watt. Acrylic is cheaper than PV silicon.

      (Actually the relationship of surface area and efficiency is fixed, so it's really a second axis.)

      -Peter

  • If this material concentrates all of the sunlight onto the PV chip in the center does that mean that NO OTHER light will pass through it? From the description of something that will take (sun)light from any angle and direct it towards the center does that mean someone behind it will only see black?

    If not, it might be a good surface to use on the millions and millions of square feet of windows that covers office buildings. You could conceivably generate ALL of a buildings energy needs that way. (The power

    • Re: (Score:3, Funny)

      by thrillseeker (518224)
      does that mean someone behind it will only see black?

      Caution ... do not look into solar concentrator with remaining eye.
  • Interesting to compare this to a holographic concentrator [prismsolar.com]. This optical concentrator has a much higher concentration ratio and thus allows the use of much less silicon, but on the other hand it requires a mechanical tracker and a heat sink, which the holographic concentrator does not.

    I hope to see both these technologies in production soon. $/W is the big barrier for photovoltaics.

  • by Mishotaki (957104) on Saturday February 21, 2009 @02:22PM (#26942199)
    There has been so many news about breakthrough in power cells technology... making them cheaper and more efficient... but why the hell are they still so damned expensive?
    • by John Hasler (414242) on Saturday February 21, 2009 @02:45PM (#26942397) Homepage

      Because they used to be insanely, ridiculously, incredibly damned expensive. Now they are merely damned expensive. In a decade or so they will be down to expensive. Someday they will be cheap, but the sun may go out first.

      • Someday they will be cheap, but the sun may go out first.

        Hmmm I can see the ads.
        "Purchase Duke Nukem Forever now, and get a free pack of solar cells!"

      • Because they used to be insanely, ridiculously, incredibly damned expensive. Now they are merely damned expensive.

        For a few months in 2008, I believe solar was cheaper than oil... still damned expensive, though.

  • In other words, a Fresnel lens. Nice!
    • by PPH (736903) on Saturday February 21, 2009 @02:48PM (#26942421)

      Not really a lens of any type. Its an example of non imaging optics [wikipedia.org]. A lens, Fresnel or otherwise, or a mirror, produces an image of an object at its focus. So, as the sun moves across the sky, its image would move across the plane of focus. So you'd either have to make that image plane big enough to contain the imaged sun track over a day or move the apparatus. Non imaging optics reflect or refract incoming light rays from any direction on to a single point as well as focus the light from a large aperture onto a smaller area.

      While the idea of non imaging optics in general isn't novel, the design of this device might be.

  • Didn't Joe DuBois invent this on Medium last season?
  • This is dependent on unobstructed sunlight and a properly aligned receptor. Which means tracking systems, which add cost. Perhaps at some point thin film PV will simply become cheaper than the lens system, because although a bigger total area will be needed, tracking will be a lot simpler or unnecessary.
  • by drinkypoo (153816) <martin.espinoza@gmail.com> on Saturday February 21, 2009 @05:19PM (#26943725) Homepage Journal

    The plastic is the problem. Can't we do it with all glass? If you use a solar furnace you can make it with solar energy. Alternately, if you get enough PV, you can run an electric furnace. Either way, plastic is nasty and sand is everywhere. (Some of the additives in glass are nasty, to be fair. But not all glass is nasty. All plastic is either nasty or has a short life when exposed to UV. Much is nasty AND has a short life.

  • For a simple lens...

  • Well, if this outfit truly manages to achieve that one dollar per watt figure, it will cause something of a revolution in solar applications. Furthermore, if they can do a buck a watt, odds are that with increased production they can do much, much better.

    If an investment of ten grand can buy me ten kW's worth of solar panels (not counting ancillary physical plant and energy storage) I'd consider putting up a small solar farm. Hell, forget the storage system: just buy a synchronized inverter and feed it b

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