Investing in new lights LED or HID?

[SupraSPL]

Hi Avenger, thanks for the encouragement. So the only difference between PPF and PPFD is that inclusion of a distance. The "per second" part was throwing me off. They are both measured per second, which is why KNNA wrote "per second of course" when he mentioned it on CC.net. I think I am on board now

This is a bit of an old theory. I am sure KNNA knows that you can not grow anything of quality under monochromatic 660nm light.

For sure, he has said that red/blue works well for vegging but that red/white/blue works best for flowering.

To what extent or percentage the tuned spectrum can reduce the required PPFD is more than a guessing game, and all the claims by LED light manufacturers so far have been way too optimistic and not based in fact.

I agree. KNNA made an interesting point in this thread. We understand that individual photons are what drive photosynthesis. Blue photons are much more power hungry and the effect really adds up:

KNNA wrote:
"A photon's energy is inversely proportional to its wavelenght. So a PAR Watt of 450nm carries 450/650=69% photons than a PAR Watt of 650nm. Or said based on the red photons, a Watt of 650nm carries 650/450=44% more photons than a 450nm Watt. UIts a large difference that advices to use uE instead of Watts.

For example, you have a 30% efficient red LED (638nm peak) and a 38% efficient blue LED (450nm peak). This a valid example of max today's efficiencies (commercialy avalaible)of both colors. While the blue emits 380mW for each watt burned, and the red only 300mW, the blue emits 1.216 uE/s while the red emits 1.542 uE, due each blue photon carries more energy."

When considering energy efficiency, we can certainly benefit from this understanding when tuning the spectrum.

 

[SupraSPL]

I stumbled across some useful Cannabis-specific, published info that may help support KNNA's photosynthetic efficiency theory. The full text PDF is currently publicly available, link at bottom. On the first page they state:

"The photosynthesis and transpiration characteristics were studied under different light levels (0, 500, 1,000, 1,500, or 2,000 μmol m−2 s−1). An increase in photosynthesis was observed with increase in the light intensity up to 1,500 μmol m−2 s−1 and then decreased subsequently at higher light levels in both types of plants.
However, the increase was more pronounced at lower light intensities below 500 μmol m−2 s−1."

Lata H, Chandra S, Khan I, ElSohly M. "Thidiazuron-induced high-frequency direct shoot
organogenesis of Cannabis sativa L." In Vitro Cellular & Developmental Biology - Plant. 2009 Feb;45(1):12-19. <http://www.springerlink.com/content/3028210397611640/>

On a side note, KNNA has suggested that when using higher levels of PPFD, CO2 supplementation can help reduce the alleged loss of efficiency.

 

[secondtry]

Hey SSPL,

So the only difference between PPF and PPFD is that inclusion of a distance. The "per second" part was throwing me off. They are both measured per second, which is why KNNA wrote "per second of course" when he mentioned it on CC.net. I think I am on board now

No that's not accurate, PPFD doesn't include distance, but it does include density which is a factor of area (m^2). The difference is PPFD is measured at the canopy and is a factor of area. PAR irradiance is often (incorrectly IMO) used to express W/m^2 (i.e. J/s/m^2) and PPF is umol/s; neither of those are the same as PPFD (umol/m^2/s).

I agree. KNNA made an interesting point in this thread. We understand that individual photons are what drive photosynthesis. Blue photons are much more power hungry and the effect really adds up:

KNNA wrote:
"A photon's energy is inversely proportional to its wavelenght. So a PAR Watt of 450nm carries 450/650=69% photons than a PAR Watt of 650nm. Or said based on the red photons, a Watt of 650nm carries 650/450=44% more photons than a 450nm Watt. UIts a large difference that advices to use uE instead of Watts.

For example, you have a 30% efficient red LED (638nm peak) and a 38% efficient blue LED (450nm peak). This a valid example of max today's efficiencies (commercialy avalaible)of both colors. While the blue emits 380mW for each watt burned, and the red only 300mW, the blue emits 1.216 uE/s while the red emits 1.542 uE, due each blue photon carries more energy."

When considering energy efficiency, we can certainly benefit from this understanding when tuning the spectrum.

If I understand what KNNA was trying to relate I don't think KNNA understands how blue photons are used by plants very well because we need less blue photons (ratio wise) than red. Reason being there are more blue photons per second due to the smaller wavelengths the blue photons have to travel. Blue photons hold the most energy but offer the lowest QE (Quantum Efficiency), thus if the energy within each blue photons does not drive photosynthesis it simply heats up that leaf (energy no used for Pn is converted to simple heat). And when we heat up the leaf we increase VPD (Vapor Pressure Deficit) which decreases stomatal conductance and lowers Pn which further prevents blue photons from being absorbed and driving Pn so they further heat up the leaf...it's a catch 22. That is why I would never buy one of the new plasma lamps, way too much blue.

Efficiency of converted watts to photonic [sic] energy is not the efficiency we should care most about, we should care most about QE. I think one of KNNA's main hangups is he seems to care very much, and concentrate very heavily upon efficiency of converting watts to lux or watts to PPF, etc.

HTH

 

[secondtry]

Hey SSPL,

I stumbled across some useful Cannabis-specific, published info that may help support KNNA's photosynthetic efficiency theory. The full text PDF is currently publicly available, link at bottom. On the first page they state:

"The photosynthesis and transpiration characteristics were studied under different light levels (0, 500, 1,000, 1,500, or 2,000 μmol m−2 s−1). An increase in photosynthesis was observed with increase in the light intensity up to 1,500 μmol m−2 s−1 and then decreased subsequently at higher light levels in both types of plants.
However, the increase was more pronounced at lower light intensities below 500 μmol m−2 s−1."

Thats the same study I posted, well one of them, which shows 1,500 PPFD as ideal. What the bold text is saying is when going from low PPFD (ex. 300-400) and increasing the PPFD (ex. to 500) the relative increase in Pn is greater than if you go from higher PPFD (ex. 700) to highest PPFD (ex. 1,500). Thus 1,500 PPFD is still the best choice and offers the highest Pn, but the relative increase of Pn is smaller from from high PPFD to highest PPFD than it is from low PPFD to medium PPFD.

That figure you posted should show you why you don't want to use KNNA suggested 300-400 PPFD, look how little Pn it's generate vs. higher PPPF...

On a side note, KNNA has suggested that when using higher levels of PPFD, CO2 supplementation can help reduce the alleged loss of efficiency.

Co2 is always good, regardless of the level of irradiance (not under a fluoro but you get my drift), and adding Co2 to high irradiance increase Pn, not due to an effect on what KNNA calls a "loss of efficiency" tho. If I were KNNA I would write and worry MUCH more about VPD at low irradiances than Co2 because VPD controls the stomatal conductance which limits the amount of Co2 taken in by leaf.


All the best

 

[renz]

So no one knows lighting from the bottom works?

Probably no one knows because if you tried it with HID there would eventually be exploded glass everywhere...

 

[renz]

Hey SSPL,

No that's not accurate, PPFD doesn't include distance, but it does include density which is a factor of area (m^2). The difference is PPFD is measured at the canopy and is a factor of area.

You absolutely need to state a distance for measuring power (PPFD in this case) in a given area to characterize a source.

Even though distance isn't included in the units, the value doesn't mean anything unless the distance is stated along with it, either along side the stated PPFD value or somewhere in the documentation.

1 uE/m^2/s doesn't mean anything for objective comparison.

1 uE/m^2/s @ 1m would.

 

[Dope Boy Magik]

wuzup with the htg supply leds??

 

[secondtry]

@ All,

Lots of people have asked me about Horti blue 1000w MH by PM so I thought I should upload a PDF about the lamp. I am not sold 100% on these lamps, I need to make sure they can emit > 1,200 PPFD at reasonable distance from canopy...but I bet these lamps when used correctly will be better than any other lamp...

HTH

 

[secondtry]

@ repoocbd
(that's the OP)

So what did you buy? LED or HID? I don't think you told us.

 

[Avenger]

I bet you will be disappointed in the Hortilux blue as far as PPFD goes, especially compared to the Hortilux super HPS. Not to mention it's short life and it loses output rather drasticly by 50% of its rated life.

 

[secondtry]

Yea that is my worry about the Hortilux blue. If the PPFD is high enough it would be great but I have doubts too. I won't use it until I test it. For now I am sticking with my 600w. What I really want is a 1000w CMH (as its pulse start) if the PPFD is high enough.

I change lamps each grow so the life span isn't a big deal to me.

All the best!

 

[VerdantGreen]

ok here's some 'meaningless' yield data from my actual plant grown under my 'toy' LED lights. 59.2 grams from a 63watt light from hydro grow LED - basically 1 gpw and the strain is a haze dom that yields fairly low so i am very happy.
i would also say (subjectively) that it smells stronger and is possibly more potent than when grown under straight hps. more like the extra terpenes and resin production you get under CMH. pics etc in my grow diary if anyone is interested.

V.

 

[renz]

YAY, REAL SCIENCE!

 

[SupraSPL]

@ Secondtry. KNNA is aware of the waste heat from blue photons in the leaf and has mentioned it before. One thing I have focused on, from what he and others have posted, individual photons are what matter for photosynthesis rather than energy of the photon, hence the need for QY or PPFD rather than PAR watts (although PAR watts can lead to these numbers). (<- Of course I realize you know all this.) It is interesting to consider the point you make about how blue photons, despite their higher energy, there are more of them per second due to higher frequency.

Re: the graph. I noticed that you posted this source as well, but I assumed you must not have read it in its entirety. I am shocked that you would summarize that data by saying that 1500 is ideal indoors. We must have very goals my friend

@ Verdant. Congrats on your successful yield and thanks for the data! Even when comparing pure HPS vs Fluoro grown bud using identical strains, I found there was a huge difference in aroma but I haven't had the chance to conduct a side by side for potency.

@ OP. I am also interested to hear what you decided on. I apologize for the hijacking but I hope you gained some insight from our lengthy discussions. Good luck!

 

[Frodobagins]

I have no idea why people look at LEDs besides that they like the wow factor. I don't think most people use LED to reduce their electric bill. Regardless, most people I know grow to reach the highest growth, yield and quality,not the lowest electric bill... (those two are mutually exclusive IMO) All the best

Well,

I can tell you my major reason for purchasing LED's, I live in a row home with my family, children, and pets. The last thing I wont to be responsible for is a massive fire that burns down my home and one half of the block with it!!!

Is that a good enough reason to look at LEDS!!!!


Frodo

 

[Frodobagins]

I stumbled across some useful Cannabis-specific, published info that may help support KNNA's photosynthetic efficiency theory. The full text PDF is currently publicly available, link at bottom. On the first page they state:

"The photosynthesis and transpiration characteristics were studied under different light levels (0, 500, 1,000, 1,500, or 2,000 μmol m−2 s−1). An increase in photosynthesis was observed with increase in the light intensity up to 1,500 μmol m−2 s−1 and then decreased subsequently at higher light levels in both types of plants.
However, the increase was more pronounced at lower light intensities below 500 μmol m−2 s−1."

Lata H, Chandra S, Khan I, ElSohly M. "Thidiazuron-induced high-frequency direct shoot
organogenesis of Cannabis sativa L." In Vitro Cellular & Developmental Biology - Plant. 2009 Feb;45(1):12-19. <http://www.springerlink.com/content/3028210397611640/>

On a side note, KNNA has suggested that when using higher levels of PPFD, CO2 supplementation can help reduce the alleged loss of efficiency.

Actually,

Pertainging to LEDS the above chart clearly shows me that because of the inherent cost of LED lamps (I paid $1300 for mine), you get your biggest bang per buck by putting your LED grow in the 500 PPFD range which gives you an E > 4. A PPFD of 1500 in a LED grow would cost you 3X and you would still have an E< 6. Thats a 300% increase in cost for less then a 50% improvement in E, Ue or however you want to measure it.

I'll shoot for for a PPFD of 500 in my LED grows, thank you!!!


Frodo

 

[secondtry]

Hey SSPL,

Well, you did it, you coaxed me back here to post to you , but only to make a couple of points, I am still not going to post here on the regular.

@ Secondtry. KNNA is aware of the waste heat from blue photons in the leaf and has mentioned it before. One thing I have focused on, from what he and others have posted, individual photons are what matter for photosynthesis rather than energy of the photon, hence the need for QY or PPFD rather than PAR watts (although PAR watts can lead to these numbers).

So called "PAR watts" (watt/m^2) from a pyranometer can not be converted to PPFD (i.e. umol/m^2/s) with any degree of accuracy; it's a big ball park conversion which I refuse do to because of the inaccuracy. SunMaster is so fuc*ing stupid for using a pyranometer it isn't even funny!!!!! Once again I will post this link: LINK

Re: the graph. I noticed that you posted this source as well, but I assumed you must not have read it in its entirety. I am shocked that you would summarize that data by saying that 1500 is ideal indoors. We must have very goals my friend

I did read the whole paper, I always do before I comment on a paper, and my point is very valid, I think you might misunderstand the paper a bit. At no point in the paper is there a claim made that Pn is higher at 500 PPFD than at 1,500 PPFD. I think you might be getting mixed up with the paper's use of PPFD like quantitations (re: umol/m^2/s) such as intercelluar CO2 (see below), maximum rate of photosynthesis (A max), etc.

At 1,500 PPFD WUE (Water Use Efficiency) is increased and intercellular CO2 (C i) is decreased which is why it's very wise to add CO2 in high irradiance gardens, this prevents "photorespiration" where leafs RuBP (i.e. rubisco) use O2 and less CO2 which greatly lowers Pn. By adding CO2 to ideal levels of 700-1,000 ppm (not over 1,200 ppm!) the ratio of intercellular CO2 concentration to ambient CO2 (C i/C a) will not cause photorespiration. Please see this link for good info on photorespiration: LINK

Here is an example of where I think your confusion lies, in these two sentences the data for "μmol m−2 s−1" (i.e. umol/m^2/s) is not PPFD, it's intercelluar CO2:

Contrary to g s, C i was highest, i.e., 365.00 ± 32.82 and 360.00 ± 21.70 μmol m−2 s−1 at zero light for in vitro and ex vitro propagated plants, respectively (Fig. 3 b). The values gradually decreased with increase in PPFD in both cases.

Can you please explain why you are shocked? Much of that paper deals with in vitro tissue culture, only a very small portion of the that paper deals with PPFD of growing plants, and in that small section ideal PPFD for highest Pn is ~1,500.

Also, this is only one paper, I cited three other papers which also find ideal PPFD for Pn, WUE, etc, is ~1,500. So I really don't see what your point is, but maybe I misunderstood what you were trying to convey?


Here is the most important section of that paper in regard to PPFD, it clearly shows 1,500 is better then 500, that is, if one adds CO2 like I (and everyone else suggests). And controlling VPD (Vapor Pressure Deficit; see my previous post about VPD) is important to lower transpiration in ANY irradiance, but more so with high PPFD:

Gas and water vapor exchange.

The effect of different PPFD on photosynthesis (P n), dark respiration (R d), transpiration (E), stomatal conductance (g s), intercellular CO2 concentration (C i), ratio of intercellular to external CO2 concentration (C i/C a), and WUE of in vitro raised and ex vitro vegetatively grown plants is shown in Fig. 3. Rate of photosynthesis tended to increase with increasing light intensity up to 1,500 μmol m−2 s−1 in both cases. However, the increase was more pronounced at PPFD below 500 μmol m−2 s−1. Maximum rate of photosynthesis (A max) was recorded as 26.40 ± 4.30 μmol m−2 s−1 for in vitro propagated and hardened plants. However, it was slightly lower (25.6 ± 3.90 μmol m−2 s−1) for ex vitro vegetatively propagated plants at 1,500 μmol m−2 s−1, but there was no significant difference. This difference in P n was, however, found statistically insignificant. A comparable photosynthetic activity between seed raised plants and their tissue culture raised counterparts of same age has also been reported by Bag et al. (2000) and Purohit et al. (2002) in the case of temperate bamboo (Thamnocalamus spathiflorus) and Himalayan oaks (Quercus leucotrichophora and Q. glauca), respectively. Furthermore, in the present study, exchange of CO2 was found to be adversely affected by light intensities beyond 1,500 μmol m−1 PPFD. Dark respiration (at 0 μmol m−2 s−1 PPFD) was ~15% higher in ex vitro plants as compared to in vitro propagated plants. The rate of transpiration (Fig. 3 a) tended to increase considerably with an increase in PPFD (up to 2,000 μmol m−2 s−1) in both sets of plants. Similar to E, g s−2 s−1) and was comparable in ex vitro and in vitro also increased with PPFD in all cases up to highest level tested (2,000 μmol m raised plants. Contrary to g s, C i was highest, i.e., 365.00 ± 32.82 and 360.00 ± 21.70 μmol m−2 s−1 at zero light for in vitro and ex vitro propagated plants, respectively (Fig. 3 b). The values gradually decreased with increase in PPFD in both cases. Variations in the C i/C a and WUE of both plants are shown in Fig. 3 c. Similar to C i, the C i/C a ratio at 0 μmol m−2 s−1 PPFD was maximum for both group of plants. The C i/C a ratio gradually decreased with PPFD up to 1,000 μmol m−2 s−1 and then became nearly constant (~0.54) for both sets of plants at higher PPFD (1,500–2,000 μmol m−2 s−1). In both sets of plants, a gradual increase in WUE was recorded with increase in PPFD up to 1,500 μmol m−2 s−1, and maximum values (30.00 ± 5.80 and 28.00 ± 9.23 for ex vitro and in vitro plants, respectively) were recorded at this light level. However, the increase was more pronounced at PPFD below 500 μmol m−2 s−1. These results reveal that in vitro propagated plants of C. sativaex vitro appeared to be normal and was comparable to vegetatively grown plants of same age with respect to the physiological functions examined in this study.

All the best


P.S. Why are so so adamant about your agreement with KNNA? Is it because you invested so much time/energy into LEDs? The fact is what I and Avenger have been writing is correct, I know it's an "inconvenient truth"...but it's the truth none the less...

 

[secondtry]

Hello,

Well,

I can tell you my major reason for purchasing LED's, I live in a row home with my family, children, and pets. The last thing I wont to be responsible for is a massive fire that burns down my home and one half of the block with it!!!

Is that a good enough reason to look at LEDS!!!!


Frodo

No, not to me. I have never burned down my houses because I use proper rated extension cords, wiring, fuses, etc. What you suggest is not a valid reason, if it was we would hear about people burning down there houses all the time...

 

[secondtry]

Hey again,

Actually,

Pertainging to LEDS the above chart clearly shows me that because of the inherent cost of LED lamps (I paid $1300 for mine), you get your biggest bang per buck by putting your LED grow in the 500 PPFD range which gives you an E > 4. A PPFD of 1500 in a LED grow would cost you 3X and you would still have an E< 6. Thats a 300% increase in cost for less then a 50% improvement in E, Ue or however you want to measure it.

I'll shoot for for a PPFD of 500 in my LED grows, thank you!!!


Frodo

Yes considering the cost of LEDs using lower PPFD is better for your wallet but NOT YOUR PLANTS! That is the crux of the issue, do you want to grow the best plants, or merely grow plants with the least electric bill? Drop the god damn LEDs and get an HID, then you can have high PPFD and you won't spend even a 1/16 of what you would on LEDs to cover the same sized canopy with less PPFD (less PPFD from LEDs that is)...

 

[secondtry]

err post, sorry.