I misstated at bit, it would be below 85%, but the logic remains. You would need to buy a hps every year for the first 3 years to keep up with or best the rate an led diminishes.
-
ICMag with help from Landrace Warden and The Vault is running a NEW contest in November! You can check it here. Prizes are seeds & forum premium access. Come join in!
LED vs. HPS: Truth about photosynthetic eff. & uniformity
- Thread starter Beta Test Team
- Start date
I misstated at bit, it would be below 85%, but the logic remains. You would need to buy a hps every year for the first 3 years to keep up with or best the rate an led diminishes.
Beta Test Team
Member
Yea, each lamp has its own rate of depreciation, for lamps like Ushio HPS and Hortlix HPS, it can be around 5,000, but also could be a bit less or more (the lowest I seen is around 3,000 hours for a high-end lamp). Certainly not great, that's for sure.
Even the claim by most CMH users is wrong, that CMH are good for 20,000 hours, they're not. At that point they're well below 85% of their original radiation (and that includes the Philips CMH).
Then there's also color shift of HIDs, which happens over time. That is, when the spectrum emitted by the lamp changes over time. This is also why using a lux meter is not a great choice for horticultural lamps when tracking radiation depreciation.
-------------
So just some quick math with lots of assumptions for e.g. Ushio or Hortilux HPS at 5,000 hours:
- Veg stage = 30 days at 18 hour per day
- Flowering stage = 60 days at 12 hour per day
- Total hour to harvest = 1,260 hours
- Time to harvest = 3 months
- Time it takes to reach useful life-span = about 12 months
--> So, a top-end HPS lamp should be changed out one time per year or so using the above grow schedule. That's not too bad, at about $95 to $110 per lamp when accounting for reduction in MSRP. For a grower with only a couple of lamps that's not much at all per year in re-lamping cost.
Last edited:
Beta Test Team
Member
And just for the CMH users (like us, we use Greenbeams). Here is an example re-lamping schedule.
Granted, the efficiency (as defined by turning joules into photosynthetic umol/s) of the Cycloptics luminaire as compared to the best-of-breed HPS and LED luminaires studied, is about 14.12% less:
- CMH 315W (Philips ballast and Elite Agro inside a Cycloptics reflector) = 1.46 umol/joule
- LED 400W (Light Science Grow Advantage Violet) = 1.7 umol/joule
- HPS 1000W (Gavita Pro DE) = 1.7 umol/joule
-------------
So just some quick math with lots of assumptions for the Philips Elite Agro CMH 315W at 10,000 hours:
- Veg stage = 30 days at 18 hour per day
- Flowering stage = 60 days at 12 hour per day
- Total hour to harvest = 1,260 hours
- Time to harvest = 3 months
- Time it takes to reach useful life-span = about 24 months
--> So, the Elite Agro lamp should be changed out every 2 years or so using the above grow schedule. That's not too bad, at about $80 to $100 per lamp when accounting for reduction in MSRP. For a grower with only a couple of lamps that's not much at all per year in re-lamping cost.
Granted, the efficiency (as defined by turning joules into photosynthetic umol/s) of the Cycloptics luminaire as compared to the best-of-breed HPS and LED luminaires studied, is about 14.12% less:
- CMH 315W (Philips ballast and Elite Agro inside a Cycloptics reflector) = 1.46 umol/joule
- LED 400W (Light Science Grow Advantage Violet) = 1.7 umol/joule
- HPS 1000W (Gavita Pro DE) = 1.7 umol/joule
-------------
So just some quick math with lots of assumptions for the Philips Elite Agro CMH 315W at 10,000 hours:
- Veg stage = 30 days at 18 hour per day
- Flowering stage = 60 days at 12 hour per day
- Total hour to harvest = 1,260 hours
- Time to harvest = 3 months
- Time it takes to reach useful life-span = about 24 months
--> So, the Elite Agro lamp should be changed out every 2 years or so using the above grow schedule. That's not too bad, at about $80 to $100 per lamp when accounting for reduction in MSRP. For a grower with only a couple of lamps that's not much at all per year in re-lamping cost.
On the topic of the CMH, they're certainly an impressive evolution of HID tech.
However LED's are finally at a point where they can be economically viable. For an entity who's committed to using their luminaire for a long period of time LED's are certainly worthwhile to look into. A softly driven, properly cooled COB led such as the vereo 29 or the CXA 3070 suffer from very little light depreciation. The vero 29 for example has an lm-70 rating of 50,000 hours with a Tj of 85*c and a drive current of 2.1 amps(80 watts). Which would be about 9 years worth of use according to the lighting schedule(1,260 hours) you listed.
A 200 watt panel could be built for a comparable price as the CMH luminaire you posted. Except the relamping cycle would be every 96-120 months rather than 24. The material cost would be roughly the same, but the savings can be found in a reduction of labor and electrical use.
Course COB lighting for horticulture application is still in it's infancy. Everything I just posted is mostly conjecture, as all of the numbers are calculated from data sheets. A paper tiger if you will, with only a handful of examples of enthusiasts using them on a small scale and no concrete scientific testing to speak of. However preliminary tests show promising results. Time will tell if they gain in popularity.
However LED's are finally at a point where they can be economically viable. For an entity who's committed to using their luminaire for a long period of time LED's are certainly worthwhile to look into. A softly driven, properly cooled COB led such as the vereo 29 or the CXA 3070 suffer from very little light depreciation. The vero 29 for example has an lm-70 rating of 50,000 hours with a Tj of 85*c and a drive current of 2.1 amps(80 watts). Which would be about 9 years worth of use according to the lighting schedule(1,260 hours) you listed.
A 200 watt panel could be built for a comparable price as the CMH luminaire you posted. Except the relamping cycle would be every 96-120 months rather than 24. The material cost would be roughly the same, but the savings can be found in a reduction of labor and electrical use.
Course COB lighting for horticulture application is still in it's infancy. Everything I just posted is mostly conjecture, as all of the numbers are calculated from data sheets. A paper tiger if you will, with only a handful of examples of enthusiasts using them on a small scale and no concrete scientific testing to speak of. However preliminary tests show promising results. Time will tell if they gain in popularity.
Beta Test Team
Member
Nice post.
Yea, COB sure is interesting! And maybe the future of LEDs are now LESs, not LEDs.
The problem with LED or LES is still the price for commercial units, not DIY. For people who care most about ROI (businesses) LED are still too expensive in many cases considering they're not any more efficient then a best-of-breed HPS, and they are 2x to 3x more expensive than that HPS umol to umol. (Granted, this won't stay true for long, I'm sure with COB or even LED, HPS efficiency will be exceeded, but it hasn't been yet, commercially.)
Most companies can't, or shouldn't, use DIY lighting of any sort in my opinion. Even though those COB are UL listed, the luminaire (for lack of a more specific term) into which they're installed wouldn't be if it's DIY. Granted, I know next to nothing about building a luminaire using COB or LED, so if I'm wrong please let me know. Insurance alone would be really tricky and expensive with DIY lights, I think.
I think the biggest barriers to LEDs or LESs being widely adopted for large scale indoor or greenhouse cultivation by commercial growers (of any high irradiance crops) are their price (professional units) and their rather poor canopy area coverage and uniformity (as compared to best-of-breed like Cycloptics or even well thought out installation of Gavita).
The former problem (price) can be overcome by companies being less greedy, and making money by selling more units at lower cost, rather than fewer units at higher cost. The latter issue is big problem for LEDs I think, for example, in a large open space warehouse or greenhouse they're not an ideal light choice for high irradiance crops.
I think there are two divergent use-cases by most growers: personal and small (for random example less than 100 sq. ft. canopy), or commercial and large (for random example 100 sq ft. canopy and greater). I think LED currently are great for small growers, but not for large growers - though they could be great for large growers in the future.
Yea, COB sure is interesting! And maybe the future of LEDs are now LESs, not LEDs.
The problem with LED or LES is still the price for commercial units, not DIY. For people who care most about ROI (businesses) LED are still too expensive in many cases considering they're not any more efficient then a best-of-breed HPS, and they are 2x to 3x more expensive than that HPS umol to umol. (Granted, this won't stay true for long, I'm sure with COB or even LED, HPS efficiency will be exceeded, but it hasn't been yet, commercially.)
Most companies can't, or shouldn't, use DIY lighting of any sort in my opinion. Even though those COB are UL listed, the luminaire (for lack of a more specific term) into which they're installed wouldn't be if it's DIY. Granted, I know next to nothing about building a luminaire using COB or LED, so if I'm wrong please let me know. Insurance alone would be really tricky and expensive with DIY lights, I think.
I think the biggest barriers to LEDs or LESs being widely adopted for large scale indoor or greenhouse cultivation by commercial growers (of any high irradiance crops) are their price (professional units) and their rather poor canopy area coverage and uniformity (as compared to best-of-breed like Cycloptics or even well thought out installation of Gavita).
The former problem (price) can be overcome by companies being less greedy, and making money by selling more units at lower cost, rather than fewer units at higher cost. The latter issue is big problem for LEDs I think, for example, in a large open space warehouse or greenhouse they're not an ideal light choice for high irradiance crops.
I think there are two divergent use-cases by most growers: personal and small (for random example less than 100 sq. ft. canopy), or commercial and large (for random example 100 sq ft. canopy and greater). I think LED currently are great for small growers, but not for large growers - though they could be great for large growers in the future.
Last edited:
genedigger
Member
im not smart with the science behind how lights work.i would love to try led to get the bill lower.ive been using a digilux bulb going on one year 12/12 everyday i harvest once a week sometimes every 2 weeks.i have not noticed any decrease in yield.i weigh every harvest all the same strains.what going to happen? is my yield going to just drop off one day? im confused.can someone out there school my ass on this subject.ive been reusing my soil and ammeding it like crazy over the past year and ive only gotten higher yields on my white diesel and oldtime moonshine an a few others.what gives .im going to get another bulb very soon just to change and see maybe my yields wiil go up?
Well this is not exactly the case. The vero 29, 3000k, 80cri, at nominal drive current (2.1 amp/80w) is roughly 39% efficient. Which is right inline with a brand new HPS bulb which are roughly 35% efficient.
They're efficiency increases significantly as the rive current is reduced as well. At 1.05 amp (40w) the vero 29 is 43% efficient. For low light intensity crops or vegetative growth, the 5000k 70 cri emitter is a perfect match. At 300ma(10.5 watts) it is theoretically 67% efficient and can adequately replace a 55w T5HO bulb and outlive many drivers. Since theoretical projections estimate 2 million hours of operation for the emitters driven this softly, compared to the typical driver life of 50,000 hours.
LED's also offer a lot of unique features that can be advantageous or highly desirable to commercial users. Since they're directional by nature don't need reflectors that need to be serviced(labor) and reduces light pollution(advertising perk). They're 'greener' in the since that there is less overall material being used and the overall safety of the materials themselves(no glass or hazardous gasses). They're inherently a bit safer in their mode of operation than HID tech, no glass bulbs to burst. Then for the high performance crowd the heat from the LED is also directional and easy to remove compared to an HID bulb. Water cooling and refrigeration tech offer unique potentials for heat removal for certain applications.
No I'll disagree with you. The problem with commercial adaption is no the price of the lamps themselves. Rather it's the lack of hard evidence and the fact that they don't exist. To my knowledge there are no commercial COB lamps available for horticulture applications. Most of the luminaries available are built for high bay industrial lighting, flood lamps, and headlights.
Price isn't the issue. Gavita markets themselves as a luxury brand light for connoisseur users. I bet they can't keep up with orders. Just need to wait for commercial lamp producers to see the potential in cob tech.
Beta Test Team
Member
That's the main issue with LEDs though, see inverse-square law. Also see the irradiance uniformity graph on page one as an example. Irradiance uniformity under LEDs has always been pretty poor over a large area (for example, square meter), which is why they're best not for large open areas for high irradiance crops.
That is, when they're kept as far from the canopy as they need to be for efficient work around the plants (> 2'), the irradiance uniformity at canopy is pretty poor. And if they're kept close to the canopy, their irradiance uniformity is better, but you also need more units and working with the plants is inefficient (as the LEDs are close to the canopy).
Raising and lowering LED or COB luminaires is also wasted work hours and kWh (e.g. winch), the same goes with raising and lowering HID luminaires. That's why most professorial commercial operations (non-Cannabis) don't raise and lower lamps, nor do scientific plant growth chambers. This is another area where there is room for this technology to mature and improve from where it is today.
(The luminaires we use, Greenbeams, are designed to be fixed in place, not raised and lowered. If you're interested, see here: https://www.icmag.com/ic/showpost.php?p=6631449&postcount=6611)
Radiance data (lumen or umol/s) isn't really all that helpful when planning radiation system (luminaire) without irradiance (lux or PPF) data and its uniformity data, as well. This is hard to calculate correctly for indoor or growth chamber setups, cookie-cutter style, because there are many things to take into account, so just trying to use the inverse-square law won't work.
Producing radiant energy is one thing, but making it turn into optimized uniform irradiant energy over the canopy is another. For smaller canopies LEDs are great, but for larger canopies that is often not the case (which is way they haven't taken over the HID market in professional operations of high irradiance crops - not Cannabis.)
True, that's a main problem with HID. We've long wanted to experiment with IR blocking film below an open reflector.
But this topic is a bit off-topic, getting into such things as kWh draw from in-line fans and such. While I agree they must be considered, for this thread it's more about the luminaire efficiency itself. (Same for the issue of 'greenness' of the luminaire, while important, it's off topic to this comparison.)
Even if commercial COB or LED luminaires turn out to be more efficient in turning joules into photosynthetic umol than best-of-breed HPS (which isn't true right now), if the price doesn’t come down relative to umol output they will not be adopted by businesses with bottom-lines (ROI) as effected by how much it costs to produce each gram. Which includes things like yield efficiency, i.e. gram per kWh, which accounts for all manner of electrical appliances.
My point and your point seem to agree: the technology isn't commercially available yet, as a luminaire one can buy (rather than build).
Yes, but they're (Gavita) are about 2.5x less to buy umol for umol. That is, to get the same photosynthetic umol/s from a LED that you do from Gavita Pro DE 1000W you'd pay about 2.5x as much. So you're not getting any more photons for plants, you're just paying a whole lot more for them...
And that's only about radiant energy, it doesn't even consider irradiance uniformity, where HID is normally better than LED. So one would need even more LEDs to match HID in terms of uniformity of PPF (umol/m2/s) over canopy in most cases.
So when we account for things like yield efficiency it's hard for commercial growers using LEDs to make back their initial investment and have lower costs to produce each gram than HPS - reaching that equilibrium may take many years, or never happen. That was the main point of the three plant scientists cited in the first post.
Anyway, thanks for the interesting conversation, I learned a few things that's for sure. COB look really interesting.
Beta Test Team
Member
The best bet is to find the lumen depreciation curve for your lamp, then calculate how many hours you have operated your lamp and see where it falls on the curve. Once lamps are less than 85% (ideally 90%) of their initial energy output (for example, as lumens) it's a good idea to re-lamp.
genedigger
Member
so i read on a few different sites my bulb is 1 yr. to 1-1/2yr. i guess that makes sense.unless this is someone hyping up el product. im gonna get a new one this week,maybe ill get 2 just in case.
While this is true of LED panels composed of a mix of 3-10w low power leds. This is would not be the case with a properly designed lighting system composed of COB's. A 80w vero 29 will cover roughly 1 square foot and require a minimum mounting distance of 1.5 ft at full power. With cobs is possible to attain a superior uniformity by distributing the power more evenly. While this is also true of 'conventional' led tech, it get's prohibitively expensive on a large scale. Even with the best HID reflectors you usually wind up with a 'hot spot' directly under the bulb. Especially with horizontally mounted bulbs.
After looking at the link I can see we're on the same line of thinking for the most part. Distributing the power using more lower power lamps over a larger area. As opposed to fewer high power lamps.
Agreed.
I think COB tech is going to be the key to bridging that gap. The main problem with them at the moment is that they haven't been built yet. It's fairly new tech, the vero series was just released in 2013. They show great promise, but every thing is basically in alpha testing at this point. Bridgelux wasn't really targeting the horticulture industry with these, it's really just a welcome happenstance that they work well. Certainly the tech could be refined if it could be proven that there is a market for it.
When considering costs, everything counts. I don't believe in leaving stones unturned.
We'll have to agree to disagree on this point. Since I can't offer much in the way of evidence. At this point, all I could show is calculated figures from the manufactures data sheet. There isn't any concrete independent testing, yet. In my opinion, the tech is there, but the evidence isn't.
The prices are dropping. It's just beginning.
Yup, the number one hinderance to industry adaptation is non existence.
Likewise, It's always good to consider other perspectives on a matter.
Sorry, I should have clarified a bit. Bridgelux differentiates their chips by their CRI(color rendering index) and their spectral output, much like florescent bulbs. Since they're mainly marketed towards human lighting applications. Without over complicating the subject this is important because the 'warmer' color temps and higher CRI emitters are less efficient at turning electricity into photons than the cooler, lower CRI emitters. IE A 5000 kelvin, 70 CRI emitter is 15% more efficient than a 2700 kelvin, 90 CRI emitter.
The whole thing is terribly inconvenient.
Beta Test Team
Member
Oh yea, that question about kelvin I posted was to devilgoob before I realized that devilgoob was responding to your post about kelvin - I thought the response was to me about the 3,000 hour useful life-span I wrote about. I'm well are of kelvin, photopic curve, CRI, etc. Sorry for the confusion and making you type that last paragraph.
CRI and kelvins, as you pointed out, have nothing to due with how plants use photons. It would be great if LED/LES markers (like CREE) would offer horticulturists data by umol, dropping all the lumens, CRI, and whatnot. Same with efficiency, we need to use umol per joule, not LER (Luminous Efficacy of Radiation), and umol/s and PPF (not lumens and lux).
Our spreadsheet we're about to make public this week analyses the spectral characteristics of any light source for which the SPD is available, using rated lamp wattage and lumens to calculate umol/s (we make use for CIE's 2006 luminous efficiency functions to get umol/s from lumen, using wattage for accuracy). Our work is based mainly off of Dr. Busko's (ca. 1999) and knna's (ca. 2006), from whom we branched their work to build upon it greatly (knna got his method from Dr. Busko originally). The spreadsheet will be well suited for analyzing LEDs and COB, as well as HID lamps. Once we release it we'd be happy to consider your input on how to optimize it for use with LEDs/LESs, assuming there are improvements hat can be made for LED users.
CRI and kelvins, as you pointed out, have nothing to due with how plants use photons. It would be great if LED/LES markers (like CREE) would offer horticulturists data by umol, dropping all the lumens, CRI, and whatnot. Same with efficiency, we need to use umol per joule, not LER (Luminous Efficacy of Radiation), and umol/s and PPF (not lumens and lux).
Our spreadsheet we're about to make public this week analyses the spectral characteristics of any light source for which the SPD is available, using rated lamp wattage and lumens to calculate umol/s (we make use for CIE's 2006 luminous efficiency functions to get umol/s from lumen, using wattage for accuracy). Our work is based mainly off of Dr. Busko's (ca. 1999) and knna's (ca. 2006), from whom we branched their work to build upon it greatly (knna got his method from Dr. Busko originally). The spreadsheet will be well suited for analyzing LEDs and COB, as well as HID lamps. Once we release it we'd be happy to consider your input on how to optimize it for use with LEDs/LESs, assuming there are improvements hat can be made for LED users.
Last edited:
Agreed, it would make life much simpler. Maybe someday we can convince CREE and Bridgelux to use more convenient units. That's why i'm looking forward to some independent tests.
I'd be interested in helping where I can, but I have much to learn. I'd be interesting in looking at it.
I'm not omnipotent, I don't entertain chinese panels for the most part. However I wouldn't purchase that panel if you were considering it. It looks very poorly designed and looks like it uses rather mundane if not outright crappy emitters.
I'm sure it will grow plants. Even an incandescent will do that though, so it's not saying much. For the sake of efficiency HID would be a better choice.
From my experience (and from PAR footprint tests) the problem with LEDs has nothing to do w/ spectrum or penetration (this is often stated as the problem, erroneously I believe, unless you call more distributed light bouncing off of reflected surfaces penetration), but rather coverage. They tend to focus the light on one spot rather than distributing it around.
Autoflower.net has some photoperiod grows w/ 1 month veg using soil achieving nearly 1 gram per watt w/ LEDs, which is pretty damn impressive if you ask me given that it's soil. However, this is only for one plant, where coverage isn't really an issue. What tends to happen when people try to go larger scale is that they buy the biggest panel possible, and the problem of focusing light on one region is exacerbated.
I think w/ LEDs if you had 4, say, 250 watt actual draw panels distributed such that the PAR reads about 1000 PPFD over a 4 x 4 area, you'd do much better than HPS. There have been some great results already on rollitup using the AT600, which suffers from the problem of focusing too much PAR on one spot. For example:
AT 600:
Compare this to a Gavita footprint (which I believe at 24" hits around 300 PPFD at the borders).
Autoflower.net has some photoperiod grows w/ 1 month veg using soil achieving nearly 1 gram per watt w/ LEDs, which is pretty damn impressive if you ask me given that it's soil. However, this is only for one plant, where coverage isn't really an issue. What tends to happen when people try to go larger scale is that they buy the biggest panel possible, and the problem of focusing light on one region is exacerbated.
I think w/ LEDs if you had 4, say, 250 watt actual draw panels distributed such that the PAR reads about 1000 PPFD over a 4 x 4 area, you'd do much better than HPS. There have been some great results already on rollitup using the AT600, which suffers from the problem of focusing too much PAR on one spot. For example:
AT 600:
Compare this to a Gavita footprint (which I believe at 24" hits around 300 PPFD at the borders).
Beta Test Team
Member
Good points. Uniformity of irradiance is a big factor in terms of costs (initial and ROI), and generally is worse for LEDs than HID in a good reflector, which is why they're currently not so well suited for large area canopies.
It's important to account for reflected photons, as well as those from other light sources (overlapping 'footprints'), to fully characterize irradiance uniformity (ideally over every couple square inches, at most).
Here is an example of irradiance uniformity over the canopy (a square meter footprint one meter from the aperture or LEDs). Our choice of luminaire is listed there as well, as "Cycloptics 315W":
https://www.icmag.com/ic/showpost.php?p=6663878&postcount=4
Neither LED nor HID reflectors nor bare lamp, except for Cycloptics, offer a very high degree of irradiance uniformity over the whole canopy, especially over larger areas (too large means, as in walls are far from the center of the canopy, mores units are needed, relatively). That feature, and the CMH spectrum from Philips 315W lamp, stationary luminaire, as well as full PPF characterization for the growth chabmer accounting for reflected photons, is why we chose Greenbeams rather than Gavita Pro DE 1000W (even though as a single luminaire Gavita has about 12% greater efficiency than Greenbeams).
Here's our canopy irradiance uniformity. For a 6' x 8' canopy using 3,780 watts (12 Greenbemans) at 61" (about 5 feet) from reflector aperture (left hand side) and 22" from reflector aperture (right hand side). The room is about 9.5" x 11.5" with 94% reflectivity walls, ceiling, and floor.
At 5' from aperture (left hand side) there is practically no reduction PPF at the edges of the canopy as compared to the center. At 22" from aperture, the reduction is less than about 200 PPF at the edges as compared to the center:
It's important to account for reflected photons, as well as those from other light sources (overlapping 'footprints'), to fully characterize irradiance uniformity (ideally over every couple square inches, at most).
Here is an example of irradiance uniformity over the canopy (a square meter footprint one meter from the aperture or LEDs). Our choice of luminaire is listed there as well, as "Cycloptics 315W":
https://www.icmag.com/ic/showpost.php?p=6663878&postcount=4
Neither LED nor HID reflectors nor bare lamp, except for Cycloptics, offer a very high degree of irradiance uniformity over the whole canopy, especially over larger areas (too large means, as in walls are far from the center of the canopy, mores units are needed, relatively). That feature, and the CMH spectrum from Philips 315W lamp, stationary luminaire, as well as full PPF characterization for the growth chabmer accounting for reflected photons, is why we chose Greenbeams rather than Gavita Pro DE 1000W (even though as a single luminaire Gavita has about 12% greater efficiency than Greenbeams).
Here's our canopy irradiance uniformity. For a 6' x 8' canopy using 3,780 watts (12 Greenbemans) at 61" (about 5 feet) from reflector aperture (left hand side) and 22" from reflector aperture (right hand side). The room is about 9.5" x 11.5" with 94% reflectivity walls, ceiling, and floor.
At 5' from aperture (left hand side) there is practically no reduction PPF at the edges of the canopy as compared to the center. At 22" from aperture, the reduction is less than about 200 PPF at the edges as compared to the center:
One has to remember that plants use light for more than just photosynthesis. Photomorphogenic responses need to be considered as well. Plant needs are not universal, as the suns output and intensity do vary depending on the position on the globe, the position of the rotation, and orbit around the sun. Plant needs can also shift as they age.
Spectral output is very important. Plants use shifts in spectral output as feedback in a changing environment. However these shifts in spectral output are relative to one another. One can't just focus on a specific (group of) wavelength without considering it's effect on the balance of the overall light source. This is where I believe LED panels composed of monochromes and low power whites fall short. They put too much emphasis on the 'absorption peaks' and litter their panel with a mix of LED's that just don't 'mix' properly. Sure it'll drive photosynthesis and growth, but it may not be the desired growth.
Not to overstate the importance of spectrum. HPS lamps, for all intents and purposes, on paper has a 'terrible' spectral output for plants. The real world results are undeniable. There is a reason HID's have been the industry standard for decades.
This is why I'm excited about COB tech. It's relatively easy to 'tweak' the spectral output by varying the type of phosphor used in the LES. The actual diodes underneath the LES are identical for a given brand/series. Usually high efficiency blue or UV diodes. These features gives manufactures an opportunity to optimize a lamp for a specific purpose by varying the shape and type of LES.
I don't think we're too far off topic. I think discussing the potential advancements is still relevant. I'd encourage you to experiment with COBS a bit, if only on a small scale.
Apologies in advance for the lack of citations. I don't have any that could be considered 'credible' IMO and I have many gaps in my own knowledge.
Beta Test Team
Member
OIBI said:
Good points. For citations of your notes about various action spectra, and the action specrta themselves and their RQEs, see the second link in my signature. More current scientific info than you'll find in any one place, anywhere, I suspect. We've been working with the exact points you raise for some time.
You may also like this thread if you haven't seen it:
"It is shown that blue light-induced stomatal opening is mediated by the blue light"
https://www.icmag.com/ic/showthread.php?t=295194
In terms of plant growth (as it relates to photosynthesis), spectrum isn't the most important factor to high photosynthetic rates, assuming it's mostly PAR range irradiance that's being emitted. And that's the main claim to fame for many LED brands, that is, their spectrum is better for photosynthesis, which isn't true except in a figurative vacuum.
Like all HID luminaire companies and individuals with whom we've had contact, I suspect most LED companies have very little (to no) understanding about spectrum as it effects photomorphogenesis, photonasty, phototropism, and photoperiodism. Heck, most have little understating of spectrum as it effect photosynthesis...
Though if you don't mind, this thread is starting to get off topic. I'd rather end this discussion about spectrum in this thread, and I'd be happy to comment in another thread about the topic.
Thanks for understanding.
