LED lighting for Greenhouses!

[kaichu dento]

Just thought it would be interesting to post some pics of the greenhouse with the experimental LED fixtures we're checking out now!

Anyone else got interest in greenhouses, and this experiment in particular?

 

[jeffosborne]

Wow! Very intreresting! I do not have any greenhouse myself, but I will be interested to know what your results are like.

The 80% red, 20% blue is shown on the label, wonder how that balance was figured?

Thanks so much for sharing your photos. What is your part in this project?

Cheers,

Jeff O.

 

[kaichu dento]

I don't know how the mix was figured, but the explanation to me has been that red was for floral growth and blue for foliage when it came to incans. When I brought this up and wondered if we shouldn't move them to the tomato side, I was told that there was another deep red when it came to led's which would be for floral growth, but that this particular combination was definitely for foliage only. :duh2:

It's been a couple months now and I can't see any difference in growth compared to the other areas of the lettuce tables so I'm having doubts about the viability of using just LED's, but maybe later when we have sections with nothing but the new fixtures it'll be easier to evaluate, I hope...

 

[blasterman]

but the explanation to me has been that red was for floral growth and blue for foliage when it came to incans.

Chlorophyll has two rather specific spectra bands that it likes, these being blue and red. You can look up the specific lines on wiki if you wish, but it's established science. What isn't quite established science is how ratios of those two spectra cause the plant to grow differently, but the common claim is that an abundance of red or blue light tells the plant there's either competing foliage above it or next to it because of the way sunlight hits it. Overhead sun being much bluer than low horizon sun. At least that's one theory.....

The question here is what exactly the LEDs in this case are supposed to accomplish. Icans and *most* HID (I believe I see HIDs mounted in this greenhouse) are going to produce sufficient blue and red spectra to meet the plants needs. So, adding additional LEDs wouldn't produce a difference in growth because the plants already have enough light.

I remember reading an article in some science journal about ten years ago where farmers were experiementing with putting colored, reflective foil on the ground directly beneath low growing outdoor vegetable crops. The idea being to see what the effects were of different wavelengths of light reflected onto the underside of the leaves where Chloroplasts had different characteristics. The results, as I recall, were varied, but certain species of vegetables responded with significant additional growth while others didn't care. I would hazard a guess that putting illumination in such a fashion in a greenhouse is an emulation of the ground foil technique.

From a pragmatic standpoint, LEDs, if used in sufficient volume, would be able to provide the same degree of required light for optimum plant growth at significant electrical savings. The reason is simple, that being that it's much easier and efficient to generate the specific spectra that Chlorophyll needs with LEDs rather than wasting a lot of energy creating spectra that the plant doesn't need (HID, Ican, etc). You are going to need a *LOT* more LED bars though.

 

[kaichu dento]

The question here is what exactly the LEDs in this case are supposed to accomplish. Icans and *most* HID (I believe I see HIDs mounted in this greenhouse) are going to produce sufficient blue and red spectra to meet the plants needs. So, adding additional LEDs wouldn't produce a difference in growth because the plants already have enough light.

From a pragmatic standpoint, LEDs, if used in sufficient volume, would be able to provide the same degree of required light for optimum plant growth at significant electrical savings. The reason is simple, that being that it's much easier and efficient to generate the specific spectra that Chlorophyll needs with LEDs rather than wasting a lot of energy creating spectra that the plant doesn't need (HID, Ican, etc). You are going to need a *LOT* more LED bars though.

As you already guessed, the ideal is that we could use less power, which is all generated here on property, and reduce heat output as well. I like the idea of using them on the lettuce side much more than for the tomatoes as well, particularly in the winter.

Typically we're needing more heat on the tomato side, which is supplemented very heavily by the lights during the day, while the lettuce side is often too hot, requiring the fans to run constantly.

The two bars already in the pictures were brought in so that we could assess the viability of going all LED and I'd really like to see a section lighted without any incan lighting before making a decision. As you noted there are still incans above the LED's, and they were run all at the same time, making the LED fixtures not much more than conversation pieces.

 

[VegasF6]

It seems like there are only 10 blue LEDs and 42 or so red. That is more like 10%. But then, it isn't the amount of LEDs but of lumens. From the few examples of power leds I am looking at, it seems the red LEDs are usually much brighter than blue, maybe 2 or 3 times so. So that would seem to make it more like 5% or even less blue light.

Am I looking at this wrong?

 

[uk_caver]

I guess that for plant lighting, lumens isn't a fantastic measurement, since it's related to human eye sensitivities, not plant sensitivities.

 

[donn_]

Fascinating stuff. I'll be adding a 40' x 10' greenhouse to the back of my house soon, and have been studying lighting sources.

Typically we're needing more heat on the tomato side, which is supplemented very heavily by the lights during the day, while the lettuce side is often too hot, requiring the fans to run constantly.

This will always be a problem with hothouse production of both Tomatoes and Lettuce in the same facility. There are Lettuce varieties which deal much more successfully with heat, and may be worth consideration. 'Jericho' is one of the best I've found so far.

Red spectrum light has been shown to increase Tomato productivity by as much as 20%, through nothing more than the use of red plastic mulch. My experiments have shown only 10%, but I'm using it outdoors, with much less control over the other elements of environment.

When I get my greenhouse together, it will be approximately 25% winter vegetables and the balance in production of ornamental grasses and selected tropicals.

 

[IMSabbel]

It seems like there are only 10 blue LEDs and 42 or so red. That is more like 10%. But then, it isn't the amount of LEDs but of lumens. From the few examples of power leds I am looking at, it seems the red LEDs are usually much brighter than blue, maybe 2 or 3 times so. So that would seem to make it more like 5% or even less blue light.

Am I looking at this wrong?

Yes.
Plants are not human eyes. They couldnt care less for the amount of lumens the lights have.

Blue leds have higher efficiency than red ones, so i would guess it might even be more than 20% blue light...

 

[blasterman]

After pounding through a lot more white papers on the subject I think I've arrived at a happy 'sweet spot'. My own tests with houseplants seem to confirm it.

Rather than blue LEDs, it would seem that using white LEDs instead solves a lot more problems. A 4 or 5:1 ratio red/white might solve a lot of these issues.

 

[VegasF6]

Very well, then how is there 80% red light measured with radiant flux?

How are blue LEDs more efficient? You are saying that 2 otherwise identical LEDs given the same amount of power, the blue will output more light, higher radiant flux?

LED manufacturers seem to only give radiant flux for royal blue, and luminuous flux for all others. Apparently that is just how it is done. Makes it hard to compare apples to apples. I did find this:
Luminous flux and luminous intensity are measurements like radiant power and radiant intensity, only adjusted for the sensitivity of the human eye. Radiant power of a wavelength of 555 nm is multiplied by a factor of 1, but light of higher and lower wavelengths are multiplied by lower factors, until infrared and ultraviolet wavelengths are reached, when the radiant power is multiplied by zero.
If I am reading it right, which I may not be, it says if I have a light source with 30 lumens at say, 620-640 nanometers (red) I would multiply 30 by a # less than 1, say for instance, .8. 30x.8=24. So, the radiant flux in that case would be 24?

 

[Apollo Cree]

Since LED's are rather monochromatic, there's potential for an LED to hit either a "sweet spot" or a null in the sensitivity of chlorophyll. I wonder if the spectral sensitivity of plants varies much from plant to plant due to other pigments and dyes, different forms of chlorophyll, different chemistry, plant structure, etc.

Blue light hazard might also be a concern in some cases.

 

[TorchBoy]

It seems like there are only 10 blue LEDs and 42 or so red. That is more like 10%. ...
Am I looking at this wrong?

10/52 is 19.2%.

 

[kaichu dento]

Fascinating stuff. I'll be adding a 40' x 10' greenhouse to the back of my house soon, and have been studying lighting sources.

This will always be a problem with hothouse production of both Tomatoes and Lettuce in the same facility. There are Lettuce varieties which deal much more successfully with heat, and may be worth consideration. 'Jericho' is one of the best I've found so far.

Red spectrum light has been shown to increase Tomato productivity by as much as 20%, through nothing more than the use of red plastic mulch. My experiments have shown only 10%, but I'm using it outdoors, with much less control over the other elements of environment.

When I get my greenhouse together, it will be approximately 25% winter vegetables and the balance in production of ornamental grasses and selected tropicals.

I'm going to see if we can get some Jericho seeds, but we have done pretty good with Green Forest and Coastal Star for Romaine. Still, it'll be interesting to see if this is a good one for us or not.
Other varieties we're using are Charles/Butterhead, Cireo/Lollo, Revolution/, Multy/Multi-Leaf, Mirata/, Ferrari/, Nevada/Summer Crisp, Cherokee/, and we've been using all of these for at least a couple years now with the Nevada, Revolution and Ferrari being in use right from the start.
This gives us a good balance between standard salad lettuce, Romaine for the Caesar salads and the Charles and Nevada cover sandwiches.

One thing that I've been wanting to do is to swap sides and put the tomatoes on the side that is getting hammered by the sun in the summer and is naturally hotter by a long shot as a result. For some reason the logic of working with nature just isn't sinking in here and I keep getting stories of how it's so much work to switch sides, even though I'm the one who would be having to do it, and how we're going to run cold water from the ice museum cooling system to make up for the fact that the sun is pounding the lettuce side of the greenhouse!

Your talk of the red mulch sounds interesting, but all I can imagine is painting the white floor in the greenhouse red! I'm scared to mention it to the boss cause he may make us work in a red floored greenhouse then! :sick2:

 

[VegasF6]

10/52 is 19.2%.

Thanks for pointing that one out Ian. It's only ~10% of the red, but it is 19.2% of the overall, which is the correct way to look at it.

A friend recently asked me to try and design one of these, but I can't imagine it would be cost effective to make one when these already exist.
Kaichu, do you have an approx cost on these?

 

[TorchBoy]

It's only ~10% of the red,

:thinking: For quantity it's 10/42, or 23.8% of the red. I have no idea about output power.

 

[VegasF6]

Ok I just suck at math :0

 

[blasterman]

A friend recently asked me to try and design one of these, but I can't imagine it would be cost effective to make one when these already exist.

Using 8' alu bars strung from the ceiling and simple 60 degree optics you could probably do it for half the price.

 

[VegasF6]

I dunno, maybe. But I would have to make something for my time. Here is the model he was initially interested in.
http://shop.ledgrowlight.com/product.sc?categoryId=11&productId=13
Not a lot of specs to go on there, but looks like 288 1W leds. And obviously active cooling, 8 fans infact, wow.

kaichu dento are the wex-c150 just passively cooled?

Then, how am I going to drive anywhere from 52 to 288 leds? That would be a lot of xitanium drivers. I looked into some meanwell solutions, but I just don't know about them.

Then, have you priced large heatsink extrusions? Not cheap. And he wants 4 units. Not saying it can't be done, but not sure if I am up to all that. Also not so sure it is cost effective vs HPS as being discussed here:
http://www.candlepowerforums.com/vb/showthread.php?t=248753
Or this post. (though I am not sure about those #'s)
http://www.candlepowerforums.com/vb/showpost.php?p=2094203&postcount=7
Or the cannabis forum linked. I didn't feel like posting that one.
Although, I have to say, it is interesting. I have never seen such a large array of 5MM leds. Cool stuff, seems the same points are made over and over again though.

Well, I have spent enough time hijacking this thread. kaichu dento thanks for posting the pics it was very interesting.

 

[kaichu dento]

A friend recently asked me to try and design one of these, but I can't imagine it would be cost effective to make one when these already exist.
Kaichu, do you have an approx cost on these?

I know that some of the fixtures we've got were incredibly expensive, and given that they did not perform as hoped, it strikes me that any price would be too much for stock fixtures that I don't believe were designed with the proper emitters.

kaichu dento are the wex-c150 just passively cooled?
Well, I have spent enough time hijacking this thread. kaichu dento thanks for posting the pics it was very interesting.

All the fixtures I've seen have been fan cooled. The newer ones we have now are simply led's mounted onto aluminum plates with a bank of fans blowing down from the top. The original lights shown in this thread have fans in the ends if I recall correctly, but I haven't seen one of them in half a year, so it's impossible for me to go look now.
I didn't see any hijack of the thread, as anything having to do with the subject seems good to me. Go ahead and carry on! :thumbsup: