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I Any sunlight band pass filter for 400-700nm of EM Spectrum?

  1. Jun 27, 2016 #1
    This 400-700nm slice is the Photosynthetically Active Radiation (PAR) required of plants and, for many applications, there is much unwanted UV and IR heat outside of it.

    Is there any known translucent material or film that will pass a high % of that 400-700nm wavelength from sunlight while also largely excluding the rest, either by reflection and/or absorbance?

    If there is anything worth looking into, but it's also crazy expensive for much more than a couple square inches of it, how best to remove any excess heat beyond its rated capacity if a Fresnel lens or other device concentrates sunlight to and through it?

    Thanks for any suggestions or links for more info.
  2. jcsd
  3. Jun 27, 2016 #2


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    What exactly are you trying to do? We may have a another suggestion that can help you.
  4. Jun 27, 2016 #3
    New hot desert small greenhouse design, inquiring if any better films, perhaps not well known for this application, that could be used to minimize IR gain.

    Or, if crazy expensive for more than a couple square inches, if could have sunlight concentrated onto and through it to then be diffused inside, minus IR component.
  5. Jun 27, 2016 #4


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    Staff: Mentor

    Well, I certainly can't help you with that. Hopefully others here can. Best of luck!
  6. Jun 27, 2016 #5

    Andy Resnick

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    The most simple filter I can think of would be a few cm of water held within a polycarbonate tray. Water will absorb most of the IR and the polycarbonate will absorb most of the UV:

  7. Jun 27, 2016 #6
  8. Jun 27, 2016 #7


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    Does a standard greenhouse setup not perform well enough?
  9. Jun 27, 2016 #8
    Greenhouses in cooler weather function very well as designed warming up interior, though have challenges at night keeping it.

    Greenhouses in deserts in summer heat expend huge resources in water and electricity in pumps/fans for evaporation cooling fighting excess IR heat build up. They also often employ moveable shading, which unfortunately also reduces the good PAR portion of sunlight desired, too.

    Bottom Line: I'm interested in exploring anything that could be employed, beyond current commercial greenhouse specialty glazing, to let more of that 400-700nm slice of Photosynthetically Active Radiation (PAR) required of plants in, while reflecting or absorbing, thus keeping out, more of that unwanted UV and IR heat outside of 400-700nm.
  10. Jun 27, 2016 #9


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    Oh, I thought you wanted a desert environment inside of a greenhouse, but you want a non-desert environment inside while the greenhouse is in the desert.
  11. Jun 27, 2016 #10


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  12. Jun 28, 2016 #11
    Thanks, Tom.G!

    Update; Off exploring Borofloat hot mirrors now, to where inexpensive solar reflectors or cheap re-purposed Cassegrain parabolic dish could concentrate light through hot mirror smaller footprint, where IR reflected off it there, then PAR visible light transmitted coolly through it to inside before being diffused. Looking at direct hollow light tube, rather than adding complexity/cost of fiber optics to direct that cooler light inside. Some outfits already offering both versions, but seeing what DIY cheaper options possible.

    Bottom Line: trying to determine if it could be done cheaper than dealing with usual excessive solar IR gain of desert summer greenhouses requiring expense of cooling space via evaporation coolers, pumps and fans, especially where water and electricity is scarce.

    Any suggestions or thoughts appreciated.
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