Most energy efficient grow light

The frequency of a far red photon (750nm) is about half the frequency of a blue (400nm) photon and thus has about half the energy of a blue photon. Per watt electrical energy twice as much far red photons can be created assuming the far red LED and the blue LED are equally efficient.
Let's plug in some numbers:
E = h x f E=Energy in Joule, h = Planck's constant in kg m^2/s, f = Frequency in Hz
f = c / l f = Frequency in Hz, c = Speed of light in m/s, l = wavelength in m
Then E = h x c / l = 6.626 x 10^-34 x 0.3 x 10^9 /( 750 x 10^-9) = 2.66 x 10^-19 Joule.

That is the energy of a far red photon. The inverse (reciprocal) equals the number of far red photons we get using 1 Joule of electrical energy.
So: 0.376 x 10^19 photons
That is still an unfamiliar number... How many micro mols is that? One mol equals 6.0 x 10^23 units (Avogadro's number; molecules, ions, photons, whatever).
0.376 x 10^19 / (6.0 x 10^23) = 0.0627 x 10^-4 mol = 6.27 umol/Joule

Note that the PPFD of a far red grow lamp is zero because far red is not within the PAR range! The most efficient grow light commercially available seems to yield 2.9 umol/Joule.

Now the real world and my questions:
- Far red seems to benefit plant growth as much as photons in the PAR range but only in conjunction with PAR. Would a combination of red and far red work? If so, what is the minimum percentage of red photons needed?
- Green light penetrates the canopy more. How important is that?
- An overall whitish spectrum helps identifying problems with the plants. Can I just turn on some normal white light to check for problems but let the plants grow in red light?
- Blue light seems to help making the plants more dense and sturdy in the vegetative phase. What percentage of blue to other photons is needed? Is there a need for blue in the bloom phase?
- Is some ultra violet important?
- How efficient are LEDs anyway?
- What percentage of energy is lost by the drivers?
- What do you think of the idea to push the spectrum as much as possible towards the far red in order to be energy efficient?

PAR = 400-700
ePAR=380-780nm ... and has been accepted as the "new PAR range". And gives validation to the 730nm LED by including its output in PAR now. And because of the wavelength weighting...can be really efficient µmols/w despite a low wall plate efficiency.

To your original question....
3.20µmols/w in full spectrum white+660nm has been done by HLG. https://cdn.shopify.com/s/files/1/1538/8585/files/HLG_Scorpion_Diablo.pdf?v=1628013597
And plenty of ready heavy lights hit over 3.0 some even 4µmols, but are relying on heavy red weighted SPDs to accomplish that.

-Driver losses(efficiencies) are posted by every driver company in the market.

JohnnyStillwater said:

The frequency of a far red photon (750nm) is about half the frequency of a blue (400nm) photon and thus has about half the energy of a blue photon. Per watt electrical energy twice as much far red photons can be created assuming the far red LED and the blue LED are equally efficient.
Let's plug in some numbers:
E = h x f E=Energy in Joule, h = Planck's constant in kg m^2/s, f = Frequency in Hz
f = c / l f = Frequency in Hz, c = Speed of light in m/s, l = wavelength in m
Then E = h x c / l = 6.626 x 10^-34 x 0.3 x 10^9 /( 750 x 10^-9) = 2.66 x 10^-19 Joule.

That is the energy of a far red photon. The inverse (reciprocal) equals the number of far red photons we get using 1 Joule of electrical energy.
So: 0.376 x 10^19 photons
That is still an unfamiliar number... How many micro mols is that? One mol equals 6.0 x 10^23 units (Avogadro's number; molecules, ions, photons, whatever).
0.376 x 10^19 / (6.0 x 10^23) = 0.0627 x 10^-4 mol = 6.27 umol/Joule

Note that the PPFD of a far red grow lamp is zero because far red is not within the PAR range! The most efficient grow light commercially available seems to yield 2.9 umol/Joule.

Now the real world and my questions:
- Far red seems to benefit plant growth as much as photons in the PAR range but only in conjunction with PAR. Would a combination of red and far red work? If so, what is the minimum percentage of red photons needed?
- Green light penetrates the canopy more. How important is that?
- An overall whitish spectrum helps identifying problems with the plants. Can I just turn on some normal white light to check for problems but let the plants grow in red light?
- Blue light seems to help making the plants more dense and sturdy in the vegetative phase. What percentage of blue to other photons is needed? Is there a need for blue in the bloom phase?
- Is some ultra violet important?
- How efficient are LEDs anyway?
- What percentage of energy is lost by the drivers?
- What do you think of the idea to push the spectrum as much as possible towards the far red in order to be energy efficient?

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You got some legwork to do. Let us know your findings.

Welcome to RIU!

I just plug my HID into a timer and grow.

xtsho said:

I just plug my HID into a timer and grow.

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That is funny..
I have only grown with a small hid for a short time, no issues.
Next 3 lights were led, again no issues
I have never worried bout power usage, so i couldnt tell you the difference.
I still really find myself eyeballing this .. Would work awesome in my 3x3

HippieDudeRon said:

PAR = 400-700
ePAR=380-780nm ... and has been accepted as the "new PAR range". And gives validation to the 730nm LED by including its output in PAR now. And because of the wavelength weighting...can be really efficient µmols/w despite a low wall plate efficiency.

To your original question....
3.20µmols/w in full spectrum white+660nm has been done by HLG. https://cdn.shopify.com/s/files/1/1538/8585/files/HLG_Scorpion_Diablo.pdf?v=1628013597
And plenty of ready heavy lights hit over 3.0 some even 4µmols, but are relying on heavy red weighted SPDs to accomplish that.

-Driver losses(efficiencies) are posted by every driver company in the market.

Click to expand...

Thanks for your answer! So there are already lights that have implemented energy efficiency by shifting the spectrum towards the (far) red. Do you know a company name or can you provide a link to such lights?

J2M3S said:

You got some legwork to do. Let us know your findings.

Welcome to RIU!

Click to expand...

Thank you!
Asking questions on this forum and watching Bugbee videos is the legwork I can do. I do not have the means nor the time to do any 'real' research...

Interesting questions…

JohnnyStillwater said:

Now the real world and my questions:
- Far red seems to benefit plant growth as much as photons in the PAR range but only in conjunction with PAR. Would a combination of red and far red work? If so, what is the minimum percentage of red photons needed?

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I don't pay that much attention to far red because my flower light doesn't have it and I'm not in the market for another light. What I have picked up is that the combination of far red + red can change when the plant starts to flower. I don't recall having seen any research that indicates a change in yield or photosynthesis.

JohnnyStillwater said:

- Green light penetrates the canopy more. How important is that?

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"penetrates the canopy" - a leaf absorbs about 95% of the photons that strike the surface. To get light to the lower part of the canopy, growers can remove what's blocking the light or add lights at the side or from below.

Shane Torpey at Migro did a video on this and I came up with the same number - 1/20 of the light gets through a leaf, leading to the condition known as "DAWA"* canopy.

JohnnyStillwater said:

- An overall whitish spectrum helps identifying problems with the plants. Can I just turn on some normal white light to check for problems but let the plants grow in red light?

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For starters, I would not design a light that was all red light. While blue light does diminish yield, "flower" lights include blue photons. Refer to the spectra for HLG's R series and Chilled's flower lights. I use a Growcraft X2 for veg and an X3 for flower.

I can see the plants well under the flower light but the veg light is a bit too "revealing" (hard to explain). What I've found with the veg light is that small differences in coloration in leaves are exaggerated such that leaves that appear normal under white light may show up as having streaks of light green when viewed under the veg light. It was off-putting at first. I now use a white light when I check the plants.

To your question - with the the Growcraft "full cycle" (red heavy) spectrum, I can check the plants' health. With the veg light (blue heavy) differences are exaggerated so I use a white light.

JohnnyStillwater said:

- Blue light seems to help making the plants more dense and sturdy in the vegetative phase. What percentage of blue to other photons is needed? Is there a need for blue in the bloom phase?

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Blue photons tend to produce plants that are short and compact, with small internodal space. The plants in my current grow have only been under the X2 and they're noticeably more dense than my previous grow (a Mars SP 3000 + a blue LED puck).

Check the spectra on chilled's website. Also, Bugbee has published results of yield vs % blue light in flower and blue hammers yield pretty hard for every 1% above 4%, IIRC. If I were planning on building a light, I'd check out the spectra on the chilled site.

I didn't have the X2 for veg for my last grow so I used the Mars SP 3000 + a blue LED combination and then used the X3 in flower (plus a Viper Spectra XS-1500 for two branches that fell out of the tent) and ended up at 947gm/m2. I suspect that the X3 played a major part in that.

JohnnyStillwater said:

- Is some ultra violet important?

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It depends on who you read. Bugbee has a video on this and…he's not a fan. He comments, I think it was one of the videos where he's being interviewed by the folks at Cornell's ag school, that people have latched on to the research that Lydon published some decades ago. In that paper, Lydon found an increase in terpenes (IIRC) under in one part of the study but not in the other. On that basis, Lydon concluded that the value of UV was "equivocal". Bugbee refers viewers to the dictionary.

I don't know what's in the Lydon paper because the source where I found it wanted $40 for the PDF so my interest level went to zero.

Light manufacturer's, perhaps, have read the PDF and decided that there's sound science behind it. Or, perhaps, it's of no actual value (ie. research does not indicate a benefit) but light manufacturer's are making UV lights because people will buy them. Dunno.

JohnnyStillwater said:

- How efficient are LEDs anyway?

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Check any site that tests lights - there's scads of data on this. Chilled has that info because they publish third party test results on their site. They also sell the Ultra, if you're in the market for an extremely high output, very efficient light.

JohnnyStillwater said:

- What percentage of energy is lost by the drivers?

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Don't know but I'd suspect that it's at least 20% - that's just a generic value that pops up in the arena of energy losses.

JohnnyStillwater said:

- What do you think of the idea to push the spectrum as much as possible towards the far red in order to be energy efficient?

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If you don't have blue in your spectrum, you're going to tend to have tall plants and will tend to have lots of internodal space which will tend to preclude you from having dense colas.
Manufacturers offer a variety of lights, with different spectra. Most growers grow lights are "white", "sunlight", "balanced" whiile some higher end lights offer spectrum control. A few manufacturers offer veg and flower lights that are, respectively, blue and red heavy - the only two that I can think of are HLG and chilled.

Having run through these questions, my limited experience points very much to what Bugbee a couple of key points in his 44 minutes "lighting myths" video (I'm sure he's relieved that I agree with him ).

*DAWA - "dark as a whale's ass"