Led Temps - Air vs Leaf Surface

meangreengrowinmachine

Well-Known Member
I can't comment on UV supplementations much myself. Only done it myself a few times and nothing controlled. Reptile bulbs when I died.
My reference to UV LEDs for fixture manufactures was towards their life expectancy. They are significantly lower than more traditional colors likes, whites, blues, reds.
Now days with BPAR(biological PAR...380nm-780nm) starting to be acknowledged equal or more so to standard PAR(400-700nm), manufactures will use the extended range it offers, but very unlikely to step outside of it till something beyond major comes forward to show it worthy.

Based on all available both evidence and technology wise, I think there is that there is more to be gained from the extended BPAR range as a grower from 700-780nm then there is to be gained from 380-400nmn.
Ah I see, that is very good to know! Thank you
 

HydroKid239

Well-Known Member
Cool find. But I'll stick to my statement. You're not going to see true IR heat in LED fixtures. That is the biggest waste in lighting history yet. Literally throwing money out the window.
Increasing ambient is free, and puts the environment into a more photosynthetically active range. Rather than waste money on light to counter your cooling.
Not to mention the reliability at temperature of those LED...similar to UV leds in that regards. the LM80 isn't even close to market ready.

730 near IR...ALL DAY LONG BABY. Great additions to any basic led fixtures spectrum.
Over 800nm... burble is a more effective use of led, money, and energy.

And the last bit is the actual marketing by companies...how are they supposed to market wasted energy. Even with a good old wordsmithing.... wasted energy, shorter lifespans, no scientific data to support its need...



The most photosynthetically active ambient temp is 86F/30C. with a leaf temp delta in the 2-5* range. That is the goal every one is after. Favorring the cooler side of it as the drop off is less steep on the cooler side of that.
Well your original statement was

“Need to get into the 800+nm to start getting direct surface heating. And there will not be a day ever that those nm are incorporated into a "LED spectrum" as you called it. 730nm...ya, but its not heat just a deeper red.” bongsmilie

I’m not forcing it on you saying you should use it, but research stops things like the above from being said.
 

JOO©E

Member
Increasing air temp increases VPD when RH & CTD (canopy temperature depression) are maintained, but RH actually decreases as ambient rises, which further exacerbates the increase in VPD. When people are increasing ambient to offset low LST, they are most likely increasing the VPD.

Is the desired effect from an increase in VPD, or LST, or both?

HID give off IR that warms plants more than LED. This means that HID grown plants have higher VPD than LED plants (for a given RH and air temp). This means that HID supposedly need even greater RH %'s than LEDs do in order to maintain a proper VPD (for a given air temp). Is this what is observed in practice?

Is the suggestion to increase ambient a round about way of increasing VPD to more similar values noticed under HID grows? I'm assuming RH isn't much greater in HID grows than LED grows, and if it truly is that most HID grows and most LED grows have similar RHs then it would mean that on average HID have greater VPD than LED. This brings me to the question of, what is truly being achieved when air temp is increased in LED grows? Is the noticed difference in growth due to increased VPD? When people are trying to increase their RH when growing with LED, are they actually countering the ultimate effect that the increase in air temp achieves (increasing VPD)? Can decreasing RH be just as effective as increasing air temp? Or, is it LST that is the driving catalyst? Is it that VPD needs less monitoring and that its more about overall LST?

I'm not sure what to conclude.




I will say that LEDs between 800-900nm won't be very effective at changing LST. They do have some decently efficient emitters within that range (~50%), but much of the emission is reflected by the leaves and it's not till about 1400nm you get decent absorption by water and really 1900nm is what you'd want to target ideally imo.

QTH (Quartz Tungsten Halide) lamps are estimated to be about 85% efficient at about 1900K CCT (can get up to 95% efficient at higher CCT), which is close to what you'd most likely want to source if you were after a targeted increase in LST. I haven't found any though to purchase realistically (Thor Labs has some interesting spectrums but seems mostly made for instrumentation and very $$). There may be use for a device to increase LST, but LST might not be the ultimate goal and there may be other more efficient ways of achieving desired growth than this. I honestly don't know, just throwing some thoughts around out there in the ether..

:bigjoint:
 
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ComfortCreator

Well-Known Member
Increasing air temp increases VPD when RH & CTD (canopy temperature depression) are maintained, but RH actually decreases as ambient rises, which further exacerbates the increase in VPD. When people are increasing ambient to offset low LST, they are most likely increasing the VPD.

Is the desired effect from an increase in VPD, or LST, or both?

HID give off IR that warms plants more than LED. This means that HID grown plants have higher VPD than LED plants (for a given RH and air temp). This means that HID supposedly need even greater RH %'s than LEDs do in order to maintain a proper VPD (for a given air temp). Is this what is observed in practice?

Is the suggestion to increase ambient a round about way of increasing VPD to more similar values noticed under HID grows? I'm assuming RH isn't much greater in HID grows than LED grows, and if it truly is that most HID grows and most LED grows have similar RHs then it would mean that on average HID have greater VPD than LED. This brings me to the question of, what is truly being achieved when air temp is increased in LED grows? Is the noticed difference in growth due to increased VPD? When people are trying to increase their RH when growing with LED, are they actually countering the ultimate effect that the increase in air temp achieves (increasing VPD)? Can decreasing RH be just as effective as increasing air temp? Or, is it LST that is the driving catalyst? Is it that VPD needs less monitoring and that its more about overall LST?

I'm not sure what to conclude.




I will say that LEDs between 800-900nm won't be very effective at changing LST. They do have some decently efficient emitters within that range (~50%), but much of the emission is reflected by the leaves and it's not till about 1400nm you get decent absorption by water and really 1900nm is what you'd want to target ideally imo.

QTH (Quartz Tungsten Halide) lamps are estimated to be about 85% efficient at about 1900K CCT (can get up to 95% efficient at higher CCT), which is close to what you'd most likely want to source if you were after a targeted increase in LST. I haven't found any though to purchase realistically (Thor Labs has some interesting spectrums but seems mostly made for instrumentation and very $$). There may be use for a device to increase LST, but LST might not be the ultimate goal and there may be other more efficient ways of achieving desired growth than this. I honestly don't know, just throwing some thoughts around out there in the ether..

:bigjoint:
What we can observe is the plants grow faster when we run LEDs into the low 80s without CO2. Versus running say 76f which with HID would be great.

The resulting change in RH / VPD is an incidental result of increasing temps solely to try and maximize growth speed.

When we understand how LEDs leaf temps are lower than ambient, we get a VPD benefit of seeing that when running at ambient say 82f...the vpd at that temp should be computed from leaf temps, not ambient. So that 82f is maybe 77f at leaf temps, and maintaining or getting close to ideal VPD is much easier at 77f than 82f.
 

JOO©E

Member
What we can observe is the plants grow faster when we run LEDs into the low 80s without CO2. Versus running say 76f which with HID would be great.

The resulting change in RH / VPD is an incidental result of increasing temps solely to try and maximize growth speed.

When we understand how LEDs leaf temps are lower than ambient, we get a VPD benefit of seeing that when running at ambient say 82f...the vpd at that temp should be computed from leaf temps, not ambient. So that 82f is maybe 77f at leaf temps, and maintaining or getting close to ideal VPD is much easier at 77f than 82f.
Interesting for sure.

Yes, VPD is lower with a -CTD(LED) compared to a +CTD(HID). Though, you are still increasing VPD when you increase LST and air temp?

Perhaps VPD is not such a big deal, looking at the HPS thermal posted from the link above, you'd need over 100% RH to begin to enter proper VPD estimates?

Photosythesis is endothermic but is driven by external photons, so I was curious how the -CTD given the energy input is being supplied from outside the system that's seeing the reduction in temp, are there other endothermic reactions?
 

JOO©E

Member
Actually, it's probably not so much that the plants are reducing in temp as it is the air is increasing in temp, and perhaps evaporation is playing a role? It certainly has me curious
:bigjoint:
 

ilovereggae

Well-Known Member
I suggest reducing air exchange to retain heat and humidity in the tent. I control humidity within a percent or two using an Inkbird humidity controller on my ventilation fan. Another inkbird controls the heater.
got my ac infinity controller dialed in. should have done this a long time ago. swear the seedlings have doubled in size since yesterday. need to get that new controller for my S6 for flower tent next.

20210223_105642.jpg20210223_092828.jpg
 
Not sure how deep anyone wants to dive on the subject,
Some marketing for Apogee in there, but some good at just past 20min mark
Well your original statement was

“Need to get into the 800+nm to start getting direct surface heating. And there will not be a day ever that those nm are incorporated into a "LED spectrum" as you called it. 730nm...ya, but its not heat just a deeper red.” bongsmilie

I’m not forcing it on you saying you should use it, but research stops things like the above from being said.
Cool perspective and out of context take. Most would call that reductio ad absurdum. So again...I stand by it.

Thanks for playing.
 
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meangreengrowinmachine

Well-Known Member
Its not even close to "clear"
Can you explain (in dummy terms i guess) whats wrong with a diode at over 800nm ? is it not possible ?
Maybe I'm not getting it either but I think what he is saying is that infrared is more about heat so when you get into infrared leds its not going to do much. However that NEAR infrared spectrum is not heat but in fact the actual spectrum that is giving you that ... more full spectrum light as opposed to doing what I am doing and using just 3500k.... ? Maybe thats what he is saying? Lol
 

getogrow

Well-Known Member
Maybe I'm not getting it either but I think what he is saying is that infrared is more about heat so when you get into infrared leds its not going to do much. However that NEAR infrared spectrum is not heat but in fact the actual spectrum that is giving you that ... more full spectrum light as opposed to doing what I am doing and using just 3500k.... ? Maybe thats what he is saying? Lol
That makes much more sense. Thanks bud....i think you may be onto something.
Im just wondering why not use the over 800nm diodes ? Does the plant do nothing at all, except heat up, when its that high ? Is that a fact ?
 

meangreengrowinmachine

Well-Known Member
That makes much more sense. Thanks bud....i think you may be onto something.
Im just wondering why not use the over 800nm diodes ? Does the plant do nothing at all, except heat up, when its that high ? Is that a fact ?
I think its because the entire point of leds is to produce LESS heat. So making an infrared led I think is against the entire purpose? ... I could be totally off base im no expert on LEDs
 

getogrow

Well-Known Member
I think its because the entire point of leds is to produce LESS heat.
Well , that used to be the main selling point but no , thats not the main reason they are "better". My mind thinks the basic white leds are lacking the "some" of the IR that hps has. Im no expert at all and im not very word smart , im just going by my tiny bit of learning and using them. Im an ol hps guy.
Hell , some guys go way overkill with leds and use the same amount of watts as they would with hps , meaning the same amount of heat. Too much in my opinion.
 
Maybe I'm not getting it either but I think what he is saying is that infrared is more about heat so when you get into infrared leds its not going to do much. However that NEAR infrared spectrum is not heat but in fact the actual spectrum that is giving you that ... more full spectrum light as opposed to doing what I am doing and using just 3500k.... ? Maybe that's what he is saying? Lol
That is what I said. over 800nm is purely wasted on heat. It does absolutely nothing but heat surfaces. It is the same heat that comes FREE by simply raising your room temperature and not wasting heat by "cooling" Why cool your room but add heat to the light?

780nm and below is NOT IR. It is Far Red. And far red is good. It is very photosytecally active(makes shit grow) as well as has morphological traits(effect plant shape/structure).

If you ever hear someone talking about "IR" in grow lights spectrum with LEDs, it is 99.9% of the time actually referring to a form of far red, usually 730nm since that is the most available in the LED world. And that confusing over the correct terminology is what I believe has lead to the little bit of bickering in this thread.

EDIT:
With all that said, heat is good up to ~86f/30C for ambient. Check out the Q10 coefficient of photosynthesis for more. Long story short, 10*C raise in temp doubles your plants metabolism rate and ability to grow. That is why hot room grow more...to a point(86f/30c). Maximizing the plants metabolism. But heat is basically free and should not be wasting money and energy on in in the form of an LED.
 
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meangreengrowinmachine

Well-Known Member
That is what I said. over 800nm is purely wasted on heat. It does absolutely nothing but heat surfaces. It is the same heat that comes FREE by simply raising your room temperature and not wasting heat by "cooling" Why cool your room but add heat to the light?

780nm and below is NOT IR. It is Far Red. And far red is good. It is very photosytecally active(makes shit grow) as well as has morphological traits(effect plant shape/structure).

If you ever hear someone talking about "IR" in grow lights spectrum with LEDs, it is 99.9% of the time actually referring to a form of far red, usually 730nm since that is the most available in the LED world. And that confusing over the correct terminology is what I believe has lead to the little bit of bickering in this thread.
Hey I got it mostly right! Lol
 

ComfortCreator

Well-Known Member
Why insist that under 800nm is not infrared?

Most definitions of the visible spectrum end at about 700nm. If you want to say over 800nm is wasted, fine, but insisting part of the spectrum sometimes called far red cant be considered infrared is inaccurate. Call it near infrared if you choose...but it is part of the infrared spectrum and using your terms maybe we could settle on 700-800nm being the USABLE and beneficial portion of the infrared range?
 

JOO©E

Member
Wavelengths greater than 780nm haven't demonstrated photosynthetic activity, though wavelengths greater than 780nm can increase rates of photosynthesis by increasing temp.

TBH I really can't think of a reason to irradiate the canopy. Maybe if you have to add heat, ie you can't just reduce exhaust rates due to high RH or low CO2 (essentially you happen to be growing in a colder climate), then perhaps directly irradiating the canopy is just as efficient as increasing ambient? Though maybe just add more lights? In all other instances though, providing IR only to increase LST doesn't seem very efficient, I'd have to agree.

And, if you were still determined to irradiate "heat" then you'd want wavelengths much greater than 780nm. The shortest non-visible wavelengths that are effectively absorbed by the plant have peaks around 1400nm, or 1900nm.
veg-reflect.png
 
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