Lighting efficiencies

PPF is measured with an integrating sphere. If you have a SPD you can apply the formulas as shown on page 8 of the link I posted earlier http://www.inda-gro.com/pdf/MeasuringPlantLight.pdf and mathematically determine PPF. Remember that PPF is just a unit of energy that relies on the efficiency of the lamp in converting power into light. But I suggest you really look at the PPF (uMole/s) values as shown on section two of the charts and you'll see that the most efficient light listed, in terms of converting energy into PPF, is an LED panel that was sampled @ 1.8 uMole/S/Watt. Keeping that in mind there are two points that I take from this;

The first being that as a grower I know that the plant response when having compared some of these technologies is not going to be driven by the highest number we see posted on a comparison like this. The range between 400-700nm is too great and a narrow LED emission that contributes to a higher efficiency is doing so by virtue of narrow wavelengths that are deemed by LED lighting engineers to be optimal to photomorphogenesis. This means that wavelengths that are not deemed as necessary or considered unimportant are reduced or eliminated in the board design. So naturally they can create a high PPF in terms of energy efficiency since the diodes are limited to much narrower spectrums.

The second being that you can compare the PPF values as they have been listed as a single number and no matter the technology, that single number is not going to tell you where in the vegetative, carotenoid and flowering regions that particular lamp emits energy. Again with the 400-700nm region being so wide any of these technologies should be listed in a 3 part format so a determination can be made as to what one can expect of the lamp given the chlorophyll absorption sensitivity curve of the particular plant being grown.

Engineers have a fond way of couching their data with the old saying; 'There are lies, damn lies and statistics'
Gardeners have a fond way couching their data with the old saying: 'Numbers can sway an argument but plant response trumps everything'

chazbolin said:

PPF is measured with an integrating sphere. If you have a SPD you can apply the formulas as shown on page 8 of the link I posted earlier http://www.inda-gro.com/pdf/MeasuringPlantLight.pdf and mathematically determine PPF.

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Sorry what is an SPD?

SPD = Spectral distribution. For example if I built a 450nm deep blue LED growing lamp the PPF and PPFD would blow the numbers right off the charts but your plant would be hating life. A warm white LED on the other hand has a decent SPD for photosynthesis but the PPFD would read much lower than a blue or a red LED. No one really knows what the best SPD is for flowering cannabis. If you asked cannabis itd probably say "the sun". But nature does not support commercial medical marijuana without our tending (ditchweed). Outdoor buds are extra leafy. I could never buy seeds from this respected company just because of the leafy outdoor pics. Anyway, once your SPD is in the ballpark, I say efficiency trumps SPD. Now that top bin LEDs have reached and overcome the radiometric efficiency of HPS, LED SPD is the new frontier.

For example I would rather use a 55% efficient 450nm LED instead of a 35% efficient 470nm blue. Even more importantly I would use a low CRI warm white LED over a high CRI led even though high CRI is less peaky. That is controversial but Mr Flux's calculus shows that High CRI leds are much less efficient in terms of PAR watts.

I summarize it like this. The only difference between PPF and PPFD is where the measurement is taken. HPS manufacturers can provide PPF but they should not provide PPFD because they would have to know about your reflector, cooling method, and canopy distance. LED lamp manufacturers can provide PPFD but it is not apples and oranges with other spectra. (Regarding the eye hortilux 1000w HPS, I argue it creates no more than 400 PAR watts, otherwise Id really have to step up my LED game

The reason PPFD from one spectrum to another is not apples and oranges in practice is because one SPD might have higher energy photons (bluer), more saturation (overly peaky), or just a poor balance than another SPD (can't compare led vs HPS PPFD for example).

All of the above are the reasons I focus on SPD and radiometric efficiency instead of PPFD. Soon I will forget what PPFD means again. Knowing only radiometric efficiency and SPD, you can perform meaningful experiments on the plants and zero in on an ideal SPD and an ideal lighting technology.

My favorite Mark Twain quote, "lies, damned lies and stats"!

Abiqua said:

My favorite Mark Twain quote, "lies, damned lies and stats"!

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Ha! Thanks for the laugh. Each of us takes ourselves too seriously in one way or another. I like LEDs because they're efficient. But I cant be bothered with minutiae.

can you augment an led panel with cfl or does it just camcel out the leds?

MourningGlory said:

can you augment an led panel with cfl or does it just camcel out the leds?

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Supplement: yes
More light = good. To a point. The discussion here is about measures, not lighting types.
See here:
https://www.rollitup.org/tags/cfl.html

Some more interesting discoveries:

http://chameleongrowsystems.com/Chameleon_Grow_Systems/Photosynthetic_Photon_Flux_(PPF).html

http://www.hoshi-lab.info/env/light.html

If these were posted prior to this, my apologies.

Question: anyone know where to find raw table data that is used in representing peak photosynthetic rates? There are hundreds of graphs and charts, but I cannot find the raw data, say that you could use to create a new chart with...
thanks in advance, cheers

Mr Flux might be able to help with that one.

canadian1969 said:

Question: anyone know where to find raw table data that is used in representing peak photosynthetic rates? There are hundreds of graphs and charts, but I cannot find the raw data, say that you could use to create a new chart with...
thanks in advance, cheers

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Most often used for this is the McCree 1972 action spectrum; the raw data is in the text file.



Note that this shows the relative efficiency. The absolute efficiency of plants is very low, in the order of 1%.

There are hundreds of chlorophyll absorption net action sensitivity curves which are meant to represent the known spectra and intensities that a particular plant species will optimize photochemical response. Due to the wide variety of plant species in the world and the fact that differing plant species will absorb different spectrums and intensities to serve their unique photobiological needs there is not a one size fits all sensitivity curve we can all point to and say 'this is it'. Scientists and researchers have not been able to agree on a separate sensitivity curve that would even standardize flowering and vegetative species. And as you can see by the DIN 5031-10 curve I post in my earlier link there is enormous differences of opinion in the amount of light that must be created in the 500-600nm regions.

The McCree curve you point to does not only not represent all plant species net action spectra it is also not representative of the amount of light that many plants, including cannabis, require, in the carotenoid or visual regions that an artificial grow lamp must emit to achieve the Emerson Effect. McCree weights the 500-600 plant requirements significantly higher in these regions, making it wasted energy to many plant species.

I am curious where you were going with relative and optimum efficiencies. If you were correlating the SPD relative intensities as shown on the 'Y' axis this is a relative radiant intensity in watts and is no way representative of plant absorption efficiencies. Since you just dropped off after your 1% statement I can only surmise that is where you were going with that which of course the SPD is not meant to integrate absorption efficiencies to a particular lamps relative intensities. I may have misunderstood your point so perhaps you would clarify that for us?

To add a few more data points, I can verify that flowering cannabis does just fine without 660nm deep reds and without far red or infrared. Emerson effect not critical. Adding 660nm leds at half and half with 630nm reds works fine too. Adding HPS to all those leds also works fine, but no huge increase in photosynthesis with the addition of far red. And of course HPS works great on its own too. So ultimately cannabis is not terribly picky. Based on that theory I just aim for the highest radiometric efficiency possible and spread out (the reds) as much as possible. Allocate 15-20% to blue and add a touch of white and you are good to go.

It sounds like you don't need a net action sensitivity curve for cannabis as the plant is as you put it 'not terribly picky' but in denying the plant a 660nm, Pr region you have missed giving it the proven benefits of chlorophyll b absorption that this spectral region provides. The Far Red is used as a Pfr switch so in providing this wavelength exclusively at lights out you can induce a flowering state without losing two hours to the plants relaxing into this state after having been cast into instant darkness.

It sounds like your theory of aiming for highest radiometric efficiencies is working for you from the SSL engineers decidedly anthropocentric viewpoint of what diodes you decide to put into your panels. Now let's see how plants respond to that theory in reality. Pictures and journals please. Based on plant response only than would I say you may, or not, be 'good to go'.

I am curious where you were going with relative and optimum efficiencies.

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Chaz, I was talking not about the optimum but about the absolute efficiency of a plant. This is very low, like one photon in a hundred is utilized in photosynthesis and the rest is wasted. Of all plants sugar cane does photosynthesis the best, turning 8% of light energy into sugar.

You seem critical of the McCree data but I don't know of anything better. The DIN data seems geared towards green leafy vegetables.

Point taken on absolute efficiencies relative to the sun. The order of magnitude may be more in the neighborhood of 1 in 1 billion photons but as sunlight is currently at infinite supply, and hopefully remains so, that is not an absorption efficiency I think we need to worry about. On the other hand I am very interested in commercial greenhouse gardening where sunlight is the primary engine of photosynthesis and supplemental lighting of optimum spectra and intensities for that species is utilized to contribute to high crop value DLI levels. This my friend is going to play a large part in the future of commercial agriculture and meeting the worlds expanding population food source requirements.

You seem critical of the McCree data

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Not so much critical as I think it overreached insofar as trying to distinguish a broad enough net action sensitivity curve that would direct those who mfg artificial light sources to target their efforts solely on these regions/intensities satisfactory. That is not entirely what McCree said in his 1972 paper it played a part in mfg's providing high levels of light in the carotenoid region. For years there has been academic debate as to how these action curves can be standardized to allow mfg's to tailor lamp output for a particular species there has to date not been a consensus and no absolute standards have been adopted. And I think that is fine. I hate absolutes in anything unless they really are absolute. While there are a fair amount of absolutes in engineering I can rely on I continue to be amazed by plant response when adjusting certain environmental conditions, such as light and anionic linear polyachrylamides to name a couple, can upset those stating 'absolutes' in plant photobiological response.

I had looked at McCree, as its referred to oft. actually the data i was looking for was the raw table data for chlorophyll a b b-carotene for peak rates.

awesome stuff though, thanks!!

MrFlux said:

Most often used for this is the McCree 1972 action spectrum; the raw data is in the text file.

View attachment 2929551

Note that this shows the relative efficiency. The absolute efficiency of plants is very low, in the order of 1%.

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thank you!!

RE far red - I have heard that idea tossed around, use a halogen at lights out but I haven't tried it. I am always growing dozens of different varieties and every batch is mixed so I stick to 12/12 flip flop to keep heat under control without AC for the most part. If I could run 14/10, get more yield but the same finish time that would be great. One thing I am convinced of though, it would be a mistake to include far red LEDs in your lamp unless they are on a switch or timer of some sort.

chazbolin said:

It sounds like your theory of aiming for highest radiometric efficiencies is working for you from the SSL engineers decidedly anthropocentric viewpoint of what diodes you decide to put into your panels.

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My goal is the get the best quality buds for smoking. Have been recycling the same soil for years, living organics only simply because my intuition tells me it is the right way to grow. I make electrical efficiency the next most important goal, minimum AC, high efficiency fans, bare bulbs etc. Yield comes last in my selections. Vegging and cloning with only 100 watts for a 2400w HPS grow. Growing cannabis indoors is caused by anthropocentric law, but I am trying to learn how to reduce that impact in every way possible and teach others how to.

chazbolin said:

Now let's see how plants respond to that theory in reality. Pictures and journals please. Based on plant response only than would I say you may, or not, be 'good to go'.

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You make a fair point chaz and I do not expect you or anyone else to take my word for it, but I would not make claims that I do not believe can be peer reviewed and achieve objective repeatable results. I have been experimenting with LED for 5 years nonstop, building off the shoulders of KNNA a great thinker. Using the same cuttings, my lamps beat bare 600HPS watt for watt by 2X easily and maybe even 3X once I get things tweaked (based on dissipation wattage and dry weight). On top of that is the subjective improvement in bud quality. I keep the journals short and sweet, with an emphasis on pics of finished plants, but I am willing to answer any questions and document anything of interest.

That said, I navigate by logic and intuition. If I didn't make my own rules I'd be nowhere. I rarely do side by sides with control groups because of limited resources. In other words I am not willing to make sacrifices in my grows to bear the burden of proof but I greatly appreciate the sacrifice of those that do. I do spend hours trying to learn and teach on this forum though, and always willing to take pics to back up my claims.

I have grown with and without deep red and the results were similar. But I am not advocating for that. We now have access to deep reds that are 42% efficient at 700mA 50c and soon we will have 48%. I have been working to convert manufacturer data into a useful form for comparison (thanks Mr Flux) and stated recommendations for building the most efficient growing lamp (~43% @ 700ma 50c), exact bins and where to get them. What improvements to this formula would you suggest?

All run at 700mA - Tj ~50c
(1) Luxeon ES 450nm blue M4R (55%)
(2) Luxeon ES 660nm deep red EX6/EX7 (38%)
(2) Oslon SSL 660nm 3T (42%)
(2) Cree XPE 630nm red P4 (42%)
(2) Cree XML2 3000K T5 bin (40.6%) replaced the XTE WW that were 32%

Here are those exact lamps at work on a bunch of low-medium yielding OGs