Study finds HPS spectrum results in higher photosynthesis rate (per light quanta) than LED spectra

[Kushash]

Nice thread Kassiopeija. These threads rarely stay on track. I find in grow comps LED and hps growers always get along and the trolls can't penetrate the conversation. In threads like this however the conversations always fall apart because the trolls, the parrots and the clueless always derail the conversation that the growers try to have.

 

[Kassiopeija]

just so you could see the effects of ir leaf heating, it would rule out what rocketsoul was suggesting that the difference in the test results could be from a higher metabolic rate. then do the test again with no ir filter for the sodium but equalised leaf temps for the led plants to see if it equalizes.

it seems they did try to work around that somewhat

from the study:

Measurements were made with the leaf cuvette temperature controlled to within ± 1˚C of the target temperature.

my personal experience is LED leaves are a few 1-3°C lower than ambient but HPS leaves are +3-4°C.

 

[Milky Weed]

One caveat is that higher photosynthetic yields does not necessarily translate to higher bud yield. I think this is all IR and due to higher temps in the plant leading to higher metabolic rates. But a hot plant also produces buds which are less dense (as in weight per volume at dry, not as in big and hard nugs), the heat seems to make the plant take on more water in its tissue which means the actual dry weight bud yields can be bigger in weight with leds, but often look smaller in volume.

Thats what i was thinking, i was wondering what the temperatures were and how the extra heat from the hps is increasing metabolism.

 

[OneHitDone]

Grew with HPS bulbs for many years. PAIN IN THE ASS! I remember constant heat problems. I mean I was using 1000watters with air cooled hoods and had to run a mini spit AC just to keep the flower rooms cool. Then regular bulb changes and loss of efficiency if not changed regularly.

No thank you.

I now run 650watt China made LEDS and WOW what a difference. No more heat issues resulting in no mini split and way less need for fans and air movement.

What a headache HPS was compared to the new Tech. AND, well the flowers are bigger, denser, terpier, and more potent.

I don't know anything about all the charts and stuff. Only 35 years of hands on experience with the plant and now both lights. LEDs are way better.

Those that refuse to upgrade are close minded or just cheap. (My electric bill went from $1500 a month to $800 a month with a greater yield.} Easy math man.

Some of you guys are so stuck in your ways you cant see the forest because of the trees...lol Reminds of the old guy who still has a land line cuz cell phones might cause cancer...lol

I call BS on this.
A 650W China led contributes more heat to the room than an air cooled 1000W HID if ducted correctly.
I saw this first hand swapping an air cooled thouie in place of a 460W indagro induction. Temp went way down with the higher wattage air cooled setup.
Plus, unless you are in denial you know that in general you could fry an egg on an led driver

 

[NanoGadget]

I call BS on this.
A 650W China led contributes more heat to the room than an air cooled 1000W HID if ducted correctly.
I saw this first hand swapping an air cooled thouie in place of a 460W indagro induction. Temp went way down with the higher wattage air cooled setup.
Plus, unless you are in denial you know that in general you could fry an egg on an led driver

I dunno what kind of drivers you are referring to, but the meanwells I run never get anything close to that hot.

 

[jcdws602]

I call BS on this.
A 650W China led contributes more heat to the room than an air cooled 1000W HID if ducted correctly.
I saw this first hand swapping an air cooled thouie in place of a 460W indagro induction. Temp went way down with the higher wattage air cooled setup.
Plus, unless you are in denial you know that in general you could fry an egg on an led driver

You must be running your light(s) at 100% if your driver(s) is/are that hot. I run multiple boards that I never go past 40% resulting in much cooler operating temperatures and will also increase their life span. Watt for watt both light sources will create similar heat output but the difference being led grows requires less watts.

 

[Kassiopeija]

You must be running your light(s) at 100% if your driver(s) is/are that hot. I run multiple boards that I never go past 40% resulting in much cooler operating temperatures and will also increase their life span. Watt for watt both light sources will create similar heat output but the difference being led grows requires less watts.

hmm so you buy 2.5 times the amount of LED fixtures needed to have 2-3% better efficiency of light generation? with drivers also becoming less efficient the more they arent driven at their normal operation setting...

 

[Fardsnarp]

Lights are tools. Put them to work. When used up, something better will probably have come by, especially in the LED market.

 

[I amTHE...GanjaFarmer]

I call BS on this.
A 650W China led contributes more heat to the room than an air cooled 1000W HID if ducted correctly.
I saw this first hand swapping an air cooled thouie in place of a 460W indagro induction. Temp went way down with the higher wattage air cooled setup.
Plus, unless you are in denial you know that in general you could fry an egg on an led driver

I call BS on you calling BS. lol

I use Meanwell and Inventronics drivers and they contribute VERY little heat to the tents. Lights out 69-72f lights on 79-81f. I use the big Infinity fans and never have to turn them up past 6 or 7. I also have clip fans blowing directly on every driver, keeps them super cool and makes the lights last longer.

So what exactly am I BSing about? Sounds more like YOU are the one full of shit my friend. Fry an egg? lol

 

[a mongo frog]

So what exactly am I BSing about? Sounds more like YOU are the one full of shit my friend. Fry an egg? lol

Thats low dude. Not cool

 

[xtsho]

 

[Offmymeds]

From:

https://www.scirp.org/journal/paperinformation.aspx?paperid=108091

View attachment 5103496
You see that at any given similar PPFD the HPS spectrum results in a (slightly) higher CO2 assimilation rate.

Before the HPS vs LED comparison, the study compared 3 LED lights to find out the best - which was chosen subsequently.

I find this noteworthy because the study itself doesn't seem to mention this, and sadly, they weren't able to use the LED to reproduce PPFD states higher than 1000umol. Which, *I suspect*, the LED would fare even worse due to the blue/red vs green-light mismatch. (green-light has been proven to work better photosynthetically at higher PPFD)

The study itself concludes that LED is far superior to HPS but the argument here relies solely on higher total raw light output, better uniform canopy spread. They state that HPS at its recommended hanging height isn't able to create the same amount of light than LED at all - which IS very believable.

But in a way a skewed argument because in a commercial operation, like a hall or big greenhouse, it is general practice to simply hang as many fixtures up in a cross-lighting setup until saturating light-levels are achieved.
Which will also take care if uniformity of light-spread.

I do not wish to shill for any type of lighting system, but I f*** hate it when studies are done in such a horrible way to basically cash in on a lighting-system weakness.... I don't need a study to realize a HID bulb has less uniform spread than a LED bar light when these systems are used as a single light-source in a tent.
Any PPFD chart shows that already. And the PPF umol/J in the datasheet also gives a clear info on the power of a light-source.

But the HPS spectrum results in a quicker photosynthate-accumulation than the LED spectrum. HPS seems to drive photosynthesis-rates higher, thus, less light-quanta will be actually needed to arrive at the very same amount of carbohydrates.

Keep in mind though it's just a single study and the results may be not without faults. Though the result is in line with my general knowledge about the various light-colours' effects on photosynthesis.
Sadly some of the LED vs LED preliminairy data isn't shown either, which could have been used to create even a bigger gap of HPS vs averaged LED data

I think everyone was thinking that.

 

[Milky Weed]

Needs some pepper

maybe calmag sauce too

 

[I amTHE...GanjaFarmer]

Thats low dude. Not cool

So dude calls me out and says my post is BS. I defend myself, and I am the bad guy? lol Did you take ur meds today mongo?

lol

 

[a mongo frog]

Did you take ur meds today mongo?

No. Sorry about that.

 

[I amTHE...GanjaFarmer]

No. Sorry about that.

 

[Prawn Connery]

I call BS on this.
A 650W China led contributes more heat to the room than an air cooled 1000W HID if ducted correctly.
I saw this first hand swapping an air cooled thouie in place of a 460W indagro induction. Temp went way down with the higher wattage air cooled setup.
Plus, unless you are in denial you know that in general you could fry an egg on an led driver

Unfortunately, physics says otherwise.

The best HPS lights are about 30% efficient = 70% thermal energy, 30% visible photon energy

Average LEDs are around 50% efficient (good ones are over 60%) = 50% heat, 50% light

70% of 1000W HPS = 700W of heat
50% of 650W LED = 325W of heat

If you put a HPS in a cool tube then yes you can duct away a fair amount of heat. But if you did the same to an LED, you could do the same.

Most LED heat is conductive (which becomes convective once air starts wicking heat away from the heatsink), while most HPS heat is radiative, which means infrared passes through the glass cool tube (the air inside the tube – which will have some humidity – does abosorb some infrared, which is ducted away, but the rest goes straight through the tube).

And we all know you can't fry an egg on a Mean Well driver. Yes, they get hot, but not that hot. Plus, why not just relocate the driver outside the grow room? Just sayin.

LED produces more light and HPS produces more heat – you can't argue with that. What you observed was simple air exchange: if you increase air exchange, you can carry more heat out of the grow area regardless of what sort of fixture it is.

 

[Prawn Connery]

But the HPS spectrum results in a quicker photosynthate-accumulation than the LED spectrum. HPS seems to drive photosynthesis-rates higher, thus, less light-quanta will be actually needed to arrive at the very same amount of carbohydrates.

Keep in mind though it's just a single study and the results may be not without faults. Though the result is in line with my general knowledge about the various light-colours' effects on photosynthesis.
Sadly some of the LED vs LED preliminairy data isn't shown either, which could have been used to create even a bigger gap of HPS vs averaged LED data

Hey mate, someone else pointed this out above, but that graph indicates to me that LED is closing the gap at higher PPFD. @Grow Lights Australia has already shared my views on this, and that is I also believed green was more efficient at lower PPFD than blue and red. It makes sense if you think about it:

* HPS has a very green spectrum which is more photosynthetically active, but mostly at lower levels which is why the LED is able to catch up at higher PPFD levels (it's a shame we don't know which Fluence spectrum was used).

* In a forest or jungle canopy environment, green light penetrates (along with far red) as it is reflected off leaves in the upper canopy into the lower canopy. However, that green light is also being photosynthesised as it is reflected off each leaf. By the time it reaches the lower canopy, there is a lot less green light than at the top (but even less blue and red), so it makes sense that plants have evolved to use green ight at lower PPFD levels than other colours.

I'm sure I have read this somewhere so I'll go off and see if I can find the study, instead of relying on memory.

The bit about cannabis being selectively bred under HPS for 40 years, that's true too. Plants that yielded better under HPS tended to be used for breeding.

I also wonder how much the extra radiated heat from the HPS also speeds up the photosynthetic process? Was there a measure of leaf temperature in that study?

 

[I amTHE...GanjaFarmer]

 

[Alfadog#1]

Alot of led company's try focusing too much on replicating hps but in a led such as color or spectrum maybe to seem more appealing to old timers or persuade into thinking they are like hps but actually led. Leds can do a much better job at fine tuning spectrum with different diodes not just bright white and far red look into leds with photogenesis spectrum made tailored to grow plants not light up football stadium's