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Thread: Light Battery

  1. #1
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    Light Battery

    If you refract light, would a solar panel obsorb more photons?

  2. #2
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    I can't see why. What makes you think it might?

    Grant Hutchison

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    I picture light photons over lapsing, and so close together that a solar cell has no choice but to only see one photon, instead of 2. I thought maybe the refraction of light, compared to that of the same amount of light not refracted, would render more photon absorption.

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    I'm not really sure what you are talking about, but people do use anti-reflective coatings for photovoltaic cells, as well as concentrators.

    First link
    Bare silicon has a high surface reflection of over 30%. The reflection is reduced by texturing and and by applying anti-reflection coatings (ARC) to the surface1. Anti-reflection coatings on solar cells are similar to those used on other optical equipment such as camera lenses. They consist of a thin layer of dielectric material, with a specially chosen thickness so that interference effects in the coating cause the wave reflected from the anti-reflection coating top surface to be out of phase with the wave reflected from the semiconductor surfaces.
    Second link
    Concentrator photovoltaics (CPV) (also known as concentration photovoltaics) is a photovoltaic technology that generates electricity from sunlight. Unlike conventional photovoltaic systems, it uses lenses or curved mirrors to focus sunlight onto small, highly efficient, multi-junction (MJ) solar cells.
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    Quote Originally Posted by Chunky View Post
    I picture light photons over lapsing, and so close together that a solar cell has no choice but to only see one photon, instead of 2. I thought maybe the refraction of light, compared to that of the same amount of light not refracted, would render more photon absorption.
    The photons will arrive at the same rate, though, whether they're coming through air or coming through glass.

    Grant Hutchison

  6. #6
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    Chunky, I am guessing that you mean using a lens or curved mirror to concentrate more light on the panel than it would get otherwise. Is that correct?

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    Quote Originally Posted by Hornblower View Post
    Chunky, I am guessing that you mean using a lens or curved mirror to concentrate more light on the panel than it would get otherwise. Is that correct?
    Maybe.

    If so, then it's futile.

    A 10'x10' lens refracting light into a 1'x1' square solar cell will collect no more energy than a 10'x10' solar cell. Either way, your collection is 100 square feet of solar influx.

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    My question stems from the idea of using the same technique they use in a TV backlight. Using a lens to refract the light. Sandwich this film between two solar cells, and repeat this process stacking them one on top of another. We could save so much space. And potentially double the output(i guess)

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    Quote Originally Posted by Chunky View Post
    My question stems from the idea of using the same technique they use in a TV backlight. Using a lens to refract the light. Sandwich this film between two solar cells, and repeat this process stacking them one on top of another. We could save so much space. And potentially double the output(i guess)
    1.
    How exactly does a thin-film lens increase the influx of light?

    If the solar cell is one square metre, it intersects one square metre of sunlight, which maxes out at about 1368 watts.

    If the solar cell is one square metre - and has one or a dozen one square metre lenses stacked on top of it - it intersects ... one square metre of sunlight, which maxes out at about 1368 watts.

    Where are all these additional photons going to come from?

    2.
    If you have more than one solar cell stacked together - and any light is getting through to the bottom one - then the top one isn't doing its job.

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    Basically you can do a couple of things: You can stack PV cells that are optimized for different parts of the solar spectrum, and that can improve areal efficiency at the cost of complexity. This is already done and has been taken about as far as it can go. The other thing you can do is use a concentrator, which can reduce the size or number of PV cells and so reduce costs if the concentrator is inexpensive. This has been done for decades in some applications. However, the concentrator increases complexity, tends to require more careful focusing, tends not to work as well in diffuse sunlight (like cloudy days) and increases PV cell temperature, which reduces efficiency and can shorten operational lifespan. As PV cell costs have come down, concentrators arenít used as often. Usually, a concentrator doesnít improve areal efficiency, but properly designed concentrators can be used to focus light on active cell surface (instead of, for instance, conductors printed on cells that can block some of the light reaching the cells) and in that case can offer limited areal efficiency improvement since less sunlight is wasted on non-converting surface. Itís not magic, though. You might get a couple percentage points improvement in panel efficiency at the cost of added complexity.

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  11. #11
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    Quote Originally Posted by DaveC426913 View Post
    1.
    How exactly does a thin-film lens increase the influx of light?

    If the solar cell is one square metre, it intersects one square metre of sunlight, which maxes out at about 1368 watts.

    If the solar cell is one square metre - and has one or a dozen one square metre lenses stacked on top of it - it intersects ... one square metre of sunlight, which maxes out at about 1368 watts.

    Where are all these additional photons going to come from?
    thats why I asked ? Idk.

    And to your 2. Not stacked vertically. Stacking them horizontally, side by side -Like the cells in a battery


    Have you ever taken apart a tv or a monitor? Have you seen what produces its backlight? Please do, and maybe you'll understand what im talking about?
    Last edited by Chunky; 2020-May-14 at 04:15 AM. Reason: Emoji didn't work.

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    FTR, Decades ago, I would spend a great deal of money, buying very expensive 1/2 W solar panels from RadioShack. I think they were $20 or $50 each. Outrageous prices nowadays. IIRC, each one had a plastic cover with arrays of small convex lenses. I recall wondering what was the point. It might be that the efficiency of light to electricity conversion increases at higher intensity, or it was just a useless gizmo.
    I'll see if I can find a picture on the net.
    This is it: https://images.app.goo.gl/PLmvoMHRwGLmmbny6

    Makes you feel old when stuff you can remember vividly are referenced as vintage.
    Last edited by a1call; 2020-May-14 at 05:09 AM.

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    If i did it right. I uploaded a pdf of this "film" im talking about. (I think) I skimmed through the pdf..
    Attached Files Attached Files
    Last edited by Chunky; 2020-May-14 at 05:30 AM. Reason: ehhh

  15. #15
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    Quote Originally Posted by Chunky View Post
    thats why I asked ? Idk.

    And to your 2. Not stacked vertically. Stacking them horizontally, side by side -Like the cells in a battery


    Have you ever taken apart a tv or a monitor? Have you seen what produces its backlight? Please do, and maybe you'll understand what im talking about?
    Are you talking about putting the panels edge-on, and using that light-spreader film to expose a larger area of solar panel to a given cross-section of sunlight?

    This could help catch sunlight that gets reflected from the panels, giving it more chances to be absorbed and converted, but you could do that by just angling panels toward each other...like a series of "V" cross section panels, with the opening of the V towards the sun. However, the panels will then shade each other when not pointed at the sun, and you're better off flattening them so they're gathering a larger area of full sunlight instead of scavenging reflected sunlight.

  16. #16
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    Quote Originally Posted by a1call View Post
    FTR, Decades ago, I would spend a great deal of money, buying very expensive 1/2 W solar panels from RadioShack. I think they were $20 or $50 each. Outrageous prices nowadays. IIRC, each one had a plastic cover with arrays of small convex lenses. I recall wondering what was the point. It might be that the efficiency of light to electricity conversion increases at higher intensity, or it was just a useless gizmo.
    I'll see if I can find a picture on the net.
    This is it: https://images.app.goo.gl/PLmvoMHRwGLmmbny6

    Makes you feel old when stuff you can remember vividly are referenced as vintage.
    Some solar panels were arrays of circular silicon chips, with those, in principle a larger objective lens would increase output, Slightly,avoiding the spaces.
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  17. #17
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    Quote Originally Posted by profloater View Post
    Some solar panels were arrays of circular silicon chips, with those, in principle a larger objective lens would increase output, Slightly,avoiding the spaces.
    I remember those solar panels, they were single cells of polycrystalline silicon that covered maybe a third of the area of the plastic housing:
    http://amal.net/?p=343

    The plastic array diffused the light more than anything. Cheap over-priced Rat Shack junk...I think I only managed to get my parents to buy me one.

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