Candy-Colored Solar Panels Don't Need Direct Sun

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flighthouse
flighthouse Registered Users Posts: 18 ✭✭
Interesting article about a different way to make a solar panel.

http://news.nationalgeographic.com/news/2009/09/090914-solar-video-ap.html

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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
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    Re: Candy-Colored Solar Panels Don't Need Direct Sun

    My solar panels also produce electricity without direct sun and on cloudy days. Just not as much. Notice any similarity there? Of course mine aren't pretty colours. :roll:
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Candy-Colored Solar Panels Don't Need Direct Sun

    Well...it's a lens.

    There are PVs now that use lenses to concentrate more light onto a smaller PV receptor. This is similar - it just concentrates in a different direction.

    The basic problem is efficiency - even if you concentrate oodles of light onto a PV receptor, that receptor itself is still a low-efficiency silicon PV cell. So what you end up with using lensing tech is a PV module which has more glass and less PV cells than a "normal" solar panel.

    The theory of course is that you can stick these things all over in places where you can't put normal solar panels. Personally, I agree with the naysayer in that video - these things are still too expensive and inefficient to be economically feasible for widespread adoption.
  • Kamala
    Kamala Solar Expert Posts: 452 ✭✭
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    Re: Candy-Colored Solar Panels Don't Need Direct Sun
    dwh wrote: »
    ... use lenses to concentrate more light ...

    Wouldn't the lenses also concentrate heat? If so, that may also lower the panel's efficiency.
  • dwh
    dwh Solar Expert Posts: 1,341 ✭✭✭
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    Re: Candy-Colored Solar Panels Don't Need Direct Sun
    Kamala wrote: »
    Wouldn't the lenses also concentrate heat? If so, that may also lower the panel's efficiency.

    The old lady scientist who talks about the product in the video says that the heat is "just dissipated".

    Infrared is a different wavelength. I suppose it's possible to design a lens that directs one wavelength this way and another wavelength that way.

    I'm guessing that is what they are doing with the lens in the OP - redirecting a percentage of visible light to the edges, while allowing (some of the) infrared to pass through.

    Still...the infrared is hitting a piece of glass, so surely there must be *some* heating of that glass.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
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    Re: Candy-Colored Solar Panels Don't Need Direct Sun

    This is bordering on a scam (separating investors/governments from their money) in my humble opinion.

    First--if this thing was going to be efficient at collecting energy--the thing should look "black" -- at least in the visible light spectrum. Any colors that are being reflected/transmitted are not being gathered for power collection by the silicon arrays. And--from the interview:
    "To see photovoltaic panels on every building. It's also nice, its efficient, its effective, its all the advantages. But still it makes the buildings more expensive. People will not be willing to pay. The efficiency now is too low. It's good but its still too low to go commercial.
    Second, if heat is a huge problem--they could always selectively coat the panel glass to reflect heat--this is done on building glass already (low E windows, etc.) to reduce heat loads. The other source of heat "conversion" would probably come from the low efficiency of a silicon PV cell--all of the "useful" spectrum that is not converted into power ("white light" on black cells) has to be converted into heat anyway.

    My last point in this post--Normal window glass is a very poor conductor of light... Solar panels use Low Iron Glass which still is ~91% efficient for 3.2mm (1/8") thick glass.

    Notice the how small the solar collector squares are. The are only a few inches across... A 2" light path in low iron glass:

    0.91^(2"/0.125") = 0.22 transmission efficiency for 2" of glass.

    Imagine what a 4'x8' piece of window glass would lose in transmission. It is possible to have light transmit for 10's of miles in glass--fiber optic cables do this all the time (although, the signals are sent in the infra red band--not the visible light band because--IIRC--that is where the glass has less losses). The fiber optic cable glass is very high purity, not cheap, and may not even make good window glass.

    And, there is the whole issue of hermetically sealing and wiring those little panels of window glass.

    I don't know for sure--but I don't see anything practical using this technology.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • tallgirl
    tallgirl Solar Expert Posts: 413 ✭✭
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    Re: Candy-Colored Solar Panels Don't Need Direct Sun

    It depends on if the color is "in" the glass, or if the coloration is part of how light is concentrated to the edges of the glass. If the glass reflects light into the inside of the glass, and keeps it there until it reaches the edge, it can be a form of solar concentration, where the entire glass surface is the collector and the edges are where all the conversion take place.

    In "Mythbuster" terms, this invention is "Plausible".