Any sunlight band pass filter for 400-700nm of EM Spectrum? 1

[shane21]

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.

 

[IRstuff]

If you're focussing light, why do you need more than a couple of square inches?

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[hendersdc]

Here is a filter that does what you want, there are many options, I just picked one size for example.

[URL unfurl="true"]http://www.edmundoptics.com/optics/optical-filters/imaging-filters/imaging-filters/89793/[/url]

 

[shane21]

IRstuff,

Application is for a small greenhouse in summer desert heat, inquiring if any better films out there, perhaps not already well known for this particular application, that could be utilized to better minimize internal IR gain via its glazing.

Or, if crazy expensive for more than a couple square inches, exploring then if it could have sunlight concentrated onto and through it to then be diffused inside greenhouse, minus its IR component. Basically, cooler sunlight.

Of course, that material would have to be able to also handle that concentrated IR heat that's absorbed and not reflected. Or, method employed to draw off heat sufficiently quick enough to avoid degrading performance or melting it outright.

I don't know if anything is available or practical, just inquiring here what avenues might could be explored.

Bottom Line: Interested in anything that could be employed, beyond current commercial greenhouse specialty glazing, to let most 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.

 

[shane21]

hendersdc, Thank you, going now to check it out!

 

[IRstuff]

If it could have been done cheaply, it would have been done. Farming is a low-margin industry, so if it's not comparable to plastic sheeting, it's probably ill-affordable.

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[shane21]

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.

 

[EdStainless]

Some of the solutions that I have seen used (plastic film with a coating on it) did reflect nearly all IR, but only passed some visible light. They could do this because there is so much light that you really don't need it all.

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[shane21]

Yes, the few innovators in greenhouse glazing that still maintain fair % of PAR visible light are not much above 20% IR filtering.

 

[IRstuff]

Any material that's got a trade name isn't going to be cheap. To "concentrate" the sunlight, you need the same equivalent area of reflector, and anything that reflects sunlight well is also not going to be cheap.

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