Are LEDs Misunderstood?

[knna]

so do people deny that this is the chlorophyll absorbtions spectra?

No, that is one graph of chlorophill's light absorbance, on a given solution. Graph varies a little depending on the solvent used, but give or take, shape is very similar.

What we say, is that chlorophill's absorbance on light on lab conditions cant be used to know what spectrum of light works better or what wavebands have more efficacy promoting photosynthesis.

Why we say that?:

1)Pure empirical checking. So its proof, not an opinion. Photosynthesis is a process revealed by CO2 uptake or O2 release by plants, that are mensurable. Just by exposing a plant to different wavelenghts and measuring CO2/O2 evolution, you can see that photosynthesis vs wavelenght response has little to do with chlorophill's absorbance in a solution (lab).

These measurements has been taken very carefully thousand of times, for several plant's species, by botanists. All have a similar profile, averaged on Mc Cree or Inada photosynthesis-wavelenght graphs. (McCree expresing photosynthesis of absorbed light, Inada showing photosynthesis for incident light). Those curves have been measured again for other species and particular strains on agronomic studies, all confirming it along the years.

2)Theoretical analysis. Just to understand empirical results, it is worth to know why chlorophills absorbance in lab cant be used as a guide for photosynthetic efficiency:

-One thing is light absortion, and other, light use. Of course, you need light get absorbed to be used. But once absorbed, it may be dissipated as heat (unuseless for photosynthesis), or used for photosynthesis at different efficacy depending of wavelenght.

-Absortion of light by chorophills in vivo plants is different of absortion of the pigment alone in a solution, that is how those chlorophill's absortion graphs are calculated. Light absortion is a quantum process, strongly affected by spatial orientation. Plants transport energy obtained by a photon absorbed on a chain of electron jumps, resulting on a estratification of chlorophill pigments into the chlorophill's molecule, with different optimal wavelenght absortion for each. End result is chlorophils in vivo being able to absorb along a way wider range than on lab conditions, and at different efficacies.

In fact, on most plant's leaves there is a estratification on clorophills layers into a single leaf, with upper layers absorbing better the red, under it absorbing better the blue and in the center of the leaf, absorbing better the green. Plants change leaf's morphology to use better the light they receive, adapting to both intensity and spectrum by changing the thickness and concentration of chlorophills on those layers. For example, a plant grown under HPS light usually have a ratio chlorophill a/b 4 times lower that those grown under sunlight, because they have a double concentration of chl b but half of a.

Its a process that can be observed by eye, as plants receiving for example, strong green light, develop thicker but smaller leaves than those receiving red light, and more if its a weak red light.

-Chlorophills are not the only light absorbing pigments of plants. There are others, less important, but that works too absorbing a decent percentage of the total light absorbed. Main ones are carotenoids.

 

[squarepush3r]

wow things seem really complicated now.

 

[knna]

wow things seem really complicated now.

Yes, that is what allows LED seller sto post a graph of chlorophill's absorbance and develop their false marketing.

People prefer simple things. As far as it seems possible or reasonable, for a seller is irrelevant if its false or not. Some people will be tricked and give their money.

But we have forums where we can find actualized and more in deep info. You dont need to understand it, just you need to be aware that many things that LED sellers tell you are marketing BS. So dont trust words, trust actual results from a lamp you see in action.

Or ask for actual light output figures so you can compare a LED lamp with another.

 

[Dreamz_Of_Green]

700-1500$ a light is crazy

lets see i can get 7 x 600HPS for the price of the vertical lamp they offer 504w and probably 20x the yield
630,000 lumens of HPS lamps vs 504w LED puts out where u think my $1500.00 will go leds are overpriced and no one seems happy with em......yeilds is what counts in the end

it all comes out to price...... if u compare money for vertical LED 1500$ vs 1500$ HPS LAMPS (u pick ur own combo) HPS wins by a few million miles ...i dont see how LED gurl even compares LED to HID u cant with prices like this

its like comparing 5600w of HPS to 504w LED when led lamp yeilds more then 5600w of HID ill buy one at 1500$

 

[sx646522]

wow things seem really complicated now.

Escuchate 'El Maestro':

Light absortion is a quantum process, strongly affected by spatial orientation. Plants transport energy obtained by a photon absorbed on a chain of electron jumps, resulting on a estratification of chlorophill pigments into the chlorophill's molecule, with different optimal wavelenght absortion for each...

In fact, on most plant's leaves there is a estratification on clorophills layers into a single leaf, with upper layers absorbing better the red, under it absorbing better the blue and in the center of the leaf, absorbing better the green...

-Chlorophills are not the only light absorbing pigments of plants. There are others, less important, but that works too absorbing a decent percentage of the total light absorbed. Main ones are carotenoids.

That's also why I referenced these HERE:

While we're at it, here's a bit more information on why a little Green is actually useful for plants, too:

Green Light Drives CO2 Fixation Deep within Leaves

Green Light Drives Leaf Photosynthesis More Efficiently than Red Light in Strong White Light: Revisiting the Enigmatic Question of Why Leaves are Green

(2nd link has been posted before I believe, the first one is 'new' here - and explains things much more clearly)

Without a little green (and yellow) in the mix, it's kinda like running a car on 6 cylinders instead of 8. You'll still get there, just not quite as fast, or in as much style. Worth a read to help illuminate (no pun intended) a common misconception.

(accessory pigments will absorb light in the green/yellow wavelengths, do biochemical 'work', and then emit (fluoresce) light in a lower wavelength - some of which is then absorbed and used by the next molecule in the chain. Kinda like regenerative braking in an electric car. Waste not, want not. Plants are pretty cool, no?...

Go through the whole abstract, it's worth a read. Should be able to download it as PDF.

BTW sp, the site I sent you to IS the sales site. You have to register and send Gud a PM, no shopping cart there yet. Don't worry, he's good peeps.

-SX

P.S. Greetz to knna

 

[FreezerBoy]

no one seems happy with em

Happy? There are growers here who are beyond ecstatic with LEDs. I'm considering them strongly. I certainly would never consider a 600 HPS. That would be a disastrous choice for me and a great many other growers as well.

 

[knna]

Great articles, sx646522!

Its nice that photosynthetic studies, that almost dissapeared during 80's and 90's, are again atractive to botanists. Those articles are not only excelent, they open the door to other botanist revisit earlier studies that dindt take into account the light absortion and use gradients described.

It is to expect that botanist now start to measure photosynthesis respect PPFD level and spectrum with all this in mind, taking into account the leave's morphology being studied so take detailed records of leaves of different thickness, structure and light adaptation, so we may infer cannabis properties from them.

BTW, reading the article I notice I was wrong, the upper epirdermis layer absorb better the blue, not the red.

 

[headband 707]

Happy? There are growers here who are beyond ecstatic with LEDs. I'm considering them strongly. I certainly would never consider a 600 HPS. That would be a disastrous choice for me and a great many other growers as well.

You know Freezerboy I have yet to have any smoke grown with LED's so I can't say one way or the other . I would have to do a double blind on taste/potency/yeild etc. but I really do see this as the wave of the future or they will use these along side the regular lights as an added spectrum. peace out Headband707

 

[SupraSPL]

Happy? There are growers here who are beyond ecstatic with LEDs. I'm considering them strongly. I certainly would never consider a 600 HPS. That would be a disastrous choice for me and a great many other growers as well.

Well said, it really fits the bill for some of us. I got to see 1.5 gr/watt last time around and I expect even more if I can get new ferts dialed in and new lamps built.

Now I can also say that the dankest buds I have ever come across in my life came from an LED grow. Granted we don't get medical grade here very often but even the stuff that comes in from cali is not as impressive.

 

[knna]

1.5gram per watt from LED have to be seen....anyways my rant isnt the lights its the price vs what u could buy HPS wise for same price id rather have 1500$

i get 600's for 200$
----------------------------
3x HPS 600w 600$
A/C/ & ducting 400$
pack of C99 f2s 140$
Nuets for hydro 100$



a Homemade Hydro system (NFT or DWC) and i will murder ur one lamps yeild at 1500$ and have money to spend on meters or anything else a noob might need

No doubt a HID setup is cheaper than a LED one, at least when we talk of large grow areas.

It is clear for anybody doing some maths that lighting a large space with LEDs is currently not cost effective.

But this is now, it is just a matter of time LED lighting goes being more and more profitable and beats HIDs too on cost. LED industry expectations is to reduce price per lm by 10 fold in 2015 respect to 2009 prices.

On the other hand, you are not including running cost on your maths. When you include the lower electric bills required to get a given yield, it results that in many cases, LEDs are now profitable: small spaces, where inneficient low wattage HIDs must be used, or light and $ costing cooltubes or aircooled hoods are required, or AA is used for cooling the space, whre each watt saved on lighting means 3 more of cooling...

In this thread we are trying to put LED on the right perspective, based on objetive arguments. LEDs arnt the magic lighting that does miracles, as many sellers says, but on the other hand, they can be used to grow excelent quiality herb and offer some advantages that other lightings. So they are currently another valid lighting alternative.

For some people, other technologies are more adecuate for their setups. But for others, LEDs may be the better option avalaible, or at least one of the options to think of.

Pioneers are researching on this field. For many, its not about how much it cost, but learn how to get the best from them. Their work will help to all the people that in the future are going to use them, by finding the spectrums, light densities, optics, growing styles, etc, in order to obtain the highests yields with the highest quiality possible.

Think that if LED industry expectations continues being achieved, in less than 5 years nobody will use any other type of lighting for growing, because they are going to allow to use a lot less watts (about 40% than with HIDs for same yield) and by cheaper.

For next year, LEDs with energy efficiencies 40% higher than best HIDs are going to be avalaible in red and blue. Until now, (good) LEDs have been getting better yields per watt while having lower gross efficiencies than HIDs. Just imagine how it is going to be when we can use LEDs way more efficient than them.

Dont blame LEDs. If any, blame the inmature industry that is full of not proffesionals and ignorants enriching themselves with the wave. In this thread you have links to many sucessfull LED grows with many happy growers. There is a lot to improve yet, and especially, in the industry, that must be able to offer well designed products at decent costs.

All is not perfect, but it is not all shit neither.

 

[asde²]

...where inneficient low wattage HIDs must be used...

i wont say low wattage HIDs are inefficient, those low watt CMH we have on market almost touching 40% efficiency which is higher than any 600w HPS can offer - and the spd doesnt seem to bad either for growing MJ as people with ~30% efficient versions claim to get 1.5g/w

For next year, LEDs with energy efficiencies 40% higher than best HIDs are going to be avalaible in red and blue.

do you mean there will be >80% (as most efficient HID go over 40%) efficient leds in red and blue? my informations are limited but the top efficiencies in laboratorys dont even hit the 70% mark from what i heard so how would they release it on market next year? - maybe i got you wrong but no matter how i try to understand you but even 50% efficient red leds to be available next year sound very unrealistic to me - sorry if i totally got you wrong but i only found those 2 options..

 

[knna]

i wont say low wattage HIDs are inefficient, those low watt CMH we have on market almost touching 40% efficiency which is higher than any 600w HPS can offer - and the spd doesnt seem to bad either for growing MJ as people with ~30% efficient versions claim to get 1.5g/w

You are right about the low wattage CMHs, I didnt thought on them when wrote that paragraph. But keep in mind too that those CMHs requires their own especific ballast than arnt cheap either. I just say LEDs may be profitable currently on small spaces, not that they are the only valid option.

do you mean there will be >80% (as most efficient HID go over 40%) efficient leds in red and blue? my informations are limited but the top efficiencies in laboratorys dont even hit the 70% mark from what i heard so how would they release it on market next year? - maybe i got you wrong but no matter how i try to understand you but even 50% efficient red leds to be available next year sound very unrealistic to me - sorry if i totally got you wrong but i only found those 2 options..

Most efficient 600W HPS on the market are about 39% bulb efficiency (I refer to PAR Watts/burned Watts). And to get all that light, you must use it on a vertical setup. If not, you must derate that emission by the optical losses at reflector and, if its the case, glass barrier.

But still getting the max of 39%, a 40% improvement means an efficiency of 39+(0.4*39=15.6)=54.6% efficiency. When i say 40% more efficients is respect the comparision base, Im not refering to absolute efficiencies, as which interest me is how much light more I can get for watt burned when comparing both options.

Right now, there is deep blue LEDs close to those efficiencies, although still very difficult to get. But it is to expect that they wont be rare next year.

On the red range, lab prototypes has reached it and are expected to be produced at the beggining of next year. Maybe not 54-55% will be released first, but I hope they will be close to 50%. Look for Epistar red chips achievements along this year. Red chips development has been stoped for some years because manufacturers used all funds on white LEDs, in order to reach the 150lm/W figure. Once reached, now they need efficient red LEDs for color compensation and to do cost effective high efficiency warm white lamps, so there are funds now dedicated again to AlInGap chips. It is reasonable to expect that now they improve the same way INGaN chips has improved on the last years.

 

[knna]

Anyway, asde, if expectation arent achieved and instead of LEDs with 40% improvement on gross efficiency over large HIDs, there are LEDs with an improvement of 20%, that is sure, because now there are some on those figures yet, still the argument of LEDs clearly surpassing HIDs in the near future is valid.

We are getting more than 1g/W constantly using LEDs emiting at efficiencies of about 25%, and always below 30%. With absolute effciencies of 50%, we may expect near double g/W figures.

 

[PetFlora]

It's been awhile since I chimed in. My last grow I supplemented my UFO 90 ($349 2 years ago, now $280) with quite a few CFL watts- cheap, but far from ideal. Feeling I left a lot of grams on the table, I am getting closer to buying another LED to compliment my UFO 90 (455-470 nm / 610 - 660 nm , 680, 740nm). As an experienced UFO 90 personal use grower, I think I need ~200 LED watts to grow 4 nice plants with reasonably phat buddz & thick nuggz.

Adding to my confusion: Several companies are now offering a variety of LEDs using 3 watt chip sets. Some have 6 r/b spectrums, others 11-1. I am not aware of any including green. GLH offers a 120; for $389; AdvancedLED a UFO 120 (11 bands) for $349. In combination with my UFO either of these might just do the trick.

Would I get as much LED as I could afford? Not until the chip replacement issue has been resolved, or the prices drop to where tossing 2-300 watt LEDs doesn't hurt.


Questions:

1. Are 3 watt LEDs better?

2. Is any mfg placing the various r/b LEDs so the various wavelengths combine in the most light balanced manner?

3. What about bulb/chip replacement? I read where the life expectancy of red leds (or is it the blues) are about half of the blue (or is it red) life expectancy?

4. Since LEDs are not easily replaced, and no mfg talks about repair or exchange, are we supposed to throw away the lights every 3-5 years?

 

[SupraSPL]

It is true that the blue/white LEDs are built on different chips than the yellow/orange/red. I remember noticing that in the Cree spec sheets. Even though the blue chips are superior it is not by much, so life expectancy should not be significantly different as long as they are not driven too hard and as long as they are properly cooled.

LED technology is evolving very fast. If a lamps retains 90% of its photon output for 5 years (an easy mark in most cases) then we can consider that the lamp will likely be replaced by much more efficient models by that time.

On the other hand once the efficiency improvements slow down we can focus on improving the lumen maintenance of the lamps for long term use. It should be possible to achieve >90% lumen maintenance for 10 years or longer of nonstop use 12/12. These charts only go down to 55c for the heatsink temp but my heatsinks are at or below 40c. Even at 55c they are expecting 90% lumen maintenance at 40,000 hours when driven at 350mA.

http://www.philipslumileds.com/technology/lumenmaintenance

 

[OPT]

So after browsing the LED topic for a little bit, I still have 2 questions...maybe ya'll can help me out with em.

I keep seeing people saying LED's are only good for Veg, but then I see some nice buds, LEDs are used throughout the whole life cycle, correct?

How is the light distribution on a LED? HIDs with reflectors reflect the light down, kinda like a upside down V, this allows plants on the outside of the direct light to still get decent lumens.

When I look at LEDs and I read that they shoot the light straight down, would this mean that only the plants directly under the LED would get the max spectrum, or can plants on the outside of the directness still get sufficient lumens?

I ask this becauses I'm interested in maybe trying an LED out. I'm looking to add more weight, but less wattage used, and if LEDs can get me there, I may try them.

OPT

 

[knna]

It's been awhile since I chimed in. My last grow I supplemented my UFO 90 ($349 2 years ago, now $280) with quite a few CFL watts- cheap, but far from ideal. Feeling I left a lot of grams on the table, I am getting closer to buying another LED to compliment my UFO 90 (455-470 nm / 610 - 660 nm , 680, 740nm). As an experienced UFO 90 personal use grower, I think I need ~200 LED watts to grow 4 nice plants with reasonably phat buddz & thick nuggz.

Adding to my confusion: Several companies are now offering a variety of LEDs using 3 watt chip sets. Some have 6 r/b spectrums, others 11-1. I am not aware of any including green. GLH offers a 120; for $389; AdvancedLED a UFO 120 (11 bands) for $349. In combination with my UFO either of these might just do the trick.

Would I get as much LED as I could afford? Not until the chip replacement issue has been resolved, or the prices drop to where tossing 2-300 watt LEDs doesn't hurt.


Questions:

1. Are 3 watt LEDs better?

Not necessarily. But not necessarily worse neither.

In general, for LED of same bin, running at "1W" (350mA) is more efficient than running at "3W"(700mA). But using them at 700mA allows to use less LEDs (lower cost) or, more often, invest on fewer better bin LEDs, thus end result is similar.

On some sense, the ones using 3W LEDs usually uses better LEDs, just because cheap asian manufacturers cant build "3W" LEDs. If any reason to choose one or the another optin, its this

2. Is any mfg placing the various r/b LEDs so the various wavelengths combine in the most light balanced manner?

Nobody knows for the moment what is the most balanced spectrum.

. What about bulb/chip replacement? I read where the life expectancy of red leds (or is it the blues) are about half of the blue (or is it red) life expectancy?

In general, on LED lighting replacement for comercial lamps makes little sense. LED lighting is different than other types of lighting. There is no replaceable parts, they are integral lamps. If they are well build and reliable, for the time light output has depreciated, you will have avalaible way better lamps by cheaper that replacing LEDs on the old one.

That would be only an option for DIY lamps or lamps with modular designs.

It would be like buying a portatil computer thinking on how to replace the motherboard after some years. Likely, for the time the motherboard is obsolete, you will buy a new one for less than the cost of replacing the motherboard. What would be important on the buy is ensuring the computer (lamp) is reliable and guaranteed for the expected operating period (useful life), or at least , for a period enough to worth the investment.


There is no a general trend of useful life for LEDs of different colors. The useful life strongly depends on the operating conditions and the quality of components used.

For example, blue/white LEDs needs special optics that not yellow with high temperature and short wavelenght light. Epoxies in general cant do that, but they are way cheaper, and many small manufacturers only have equipment for that. Thus their Blue/white LEDs wont have a good useful life.

On the other hand, red chips usually are used at larger current densities, which makes them more sensitive to external temperature. If the thermal path is not well designed, they will degrade fast. But good designed red LEDs running on the specified conditions may have a very long useful life. Some quality ones projects 80% initial emission past 80000h on conditions able to be acomplished on the practice.

But if you have an integral lamp, you must trust the projection of useful of the manufacturer. Imagine that if thay lies systematically about initial perfomance (that is easily mensurable with the right equipment), you cant trust them on projections of useful life, and way less on the horticultural market. For the dominant lamps right know (UFOs and similar), the fact is we dont know if they are going to keep 80% of initial output past 6 months. I wouldnt expect more than 15000h, and likely 8-12Kh may be close to reality for the good ones (3-4 years of continous use). Time will tell.

. Since LEDs are not easily replaced, and no mfg talks about repair or exchange, are we supposed to throw away the lights every 3-5 years?

Yes, thats it. The same you throw your CFLs, together with his equipment. The target of manufacturers is to sell integral lighting systems and achieve a continous price dropping, so people can buy for cheaper a new lamp when the older has done its job.

I think there is a place for modular designs that allow some partial replacement and upgrading without throwing all off. But its not easy to do. Electronic equipment has a life. If you want to use, for example, a power supply that outlast the LEDs themselves, you need to use very high quality components, which in turn would make it very expensive. Possible, but probably unsucessfull on the market, people buys the cheaper product when you offer a life of 10years vs 5 years. People is used to doubt of marketing claims, and for the time users could confirm others that the lamps actually lasted 10 years and that it was upgraded three times, the company is bankrupt.

So after browsing the LED topic for a little bit, I still have 2 questions...maybe ya'll can help me out with em.

I keep seeing people saying LED's are only good for Veg, but then I see some nice buds, LEDs are used throughout the whole life cycle, correct?

LEDs are valid for all the cycle. But as on veg you need lower light densities and the efficecy improvement of LED spectrums is higher, usually most LEDs lamps works fine on veg, and their limitations (low efficiency, poor spectrum) only appears on bloom, when if there is no enough light, there is nothing to do, whatever the spectrum.

How is the light distribution on a LED? HIDs with reflectors reflect the light down, kinda like a upside down V, this allows plants on the outside of the direct light to still get decent lumens.

When I look at LEDs and I read that they shoot the light straight down, would this mean that only the plants directly under the LED would get the max spectrum, or can plants on the outside of the directness still get sufficient lumens?

It depends of each lamp. But in general, you are right, you cant use them on grow spaces way larger than the lamp itself. But only secondarily due the light distribution, mainly due if the grow space is too large, current lamps are unable to provide enough light.

With most HID reflectors happen similar, however. Light distribution is very uneven most often. But as they emits lots of light, by raising the lamp the footprint is enlarged still keeping good average irradiances. You could do the same with any LED panel which dont use very narrow optics, but the problem on this situation is often they can give enough liught for a large footprint budding sucessfuly. This will change on the near future, hopefully.

 

[SupraSPL]

Another way to adjust the lamp coverage is by choosing different heatsink profiles. Lower profile heatsinks (shorter fins) work great for veg and the taller profile heatsinks work best for flowering because they increase the light density. I try to keep the heatsink as close to the canopy as possible but not so close that hot spots are created or reduced color mixing.

I have been trying to beat color mixing problems by using less colors and spreading them more evenly. So far a simple red/deep red/white spectrum is working well.

Another way to get more benefit from the even spread of LED is using defoliation. Rather than cleaning up the lower shoots to improve upper colas you can gradually remove upper fan leaves that are shading lower bud sites. So far it is working well (thanks for that tip KNNA!) As a bonus you can feed them to your cat or yourself is you dont mind a numb tongue.

 

[Weezard]

Wait! What?

Wait! What?

Aloha, Supra,

Did you not mean "reflectors" when you typed "heatsinks".
If not, please explain your reasoning so I can get some sleep tonight.

Cornfused weeze

 

[unthing]

Weezard, it will haunt your dreams..

Well, I didn't understand either. But hopefully Supra will soon explain it