Why LEDs make bad plant lights (facts + pics!)

[Ross]

Let's not get carried away or sucked in to inflamatory threads (not that you are). I think this whole topic is very much like the elections and presenting lots of "edge" posts, and there are those who really want this technology to be the end-all and there are those (like me) that say ho-hum, heard that before. So, at the trisk of inflating this discussion even more, let me suggest we move on. Ocelaris has made his point (and a good one) that the LED technology doesn't suck, it just needs some time to mature and become what some would hope it will. In the mean time we use what we use and enjoy our orchids. Can we agree to this?

[Tele fan]

You bet.
David

[Arvax]

Just made up a LED Luxeon array to test
( mix of blue and red 3W LEDs).
As far as the spectrum I am using this chart...
Botany online: Photosynthesis - Absorption Spectra - Chlorophyll a and b

Since I am concerned about power cost I matched the number of LEDs and type ( Red and blue have different voltage drops ) to equal 12V so no dropping resistor is needed.

[Ocelaris]

Are you running these constant current off of a power module? I'm curious! Love to see how it works out!

As far as power cost is concerned, If LEDs are more efficient per watt, they might be more efficient over fluorescent or HID, but as far as a white LED is concerned, they're still lumen/watt behind fluorescent and HID... so far. But again, if Red and Blue are are what the plants need, they might over power straight white light. Take some pics!

[Gold3nku5h]

Do you think any new technology worked all the kinks out within 10 years, within 20? Im not saying it should take anywhere near that long, but as long as people keep working on them to make them better, it will only be a matter of time before LED's run the hydroponic industry. The color spectrum to grow with is easily changed with them as its just a matter of rendering, instead of figuring out which gasses do what when and how. Already there are grow light LED's that are fully usable by plants, you may have seen ones that wern't specific to plant growth.

[greenpassion]

Originally Posted by Gold3nku5h

Do you think any new technology worked all the kinks out within 10 years, within 20? Im not saying it should take anywhere near that long, but as long as people keep working on them to make them better, it will only be a matter of time before LED's run the hydroponic industry. The color spectrum to grow with is easily changed with them as its just a matter of rendering, instead of figuring out which gasses do what when and how. Already there are grow light LED's that are fully usable by plants, you may have seen ones that wern't specific to plant growth.

Can you tell me what the LED's are that you're referring to? Are you familiar with the LED's from Orchid Limited? I was referred there by an earlier post from here, where the person replying to me says she uses them and they do just fine.

[Ocelaris]

I'll start by saying I don't know the product by Orchid Limited, but this thread is very old and technology may have changed somewhat, but I'm not aware of efficiency improving that much, and the same chemistry/physics apply now as they did before. Look at a lighting source's efficiency, color rendering index and color temperature. Pick the best light for the money, plants don't care how much you spent.

Maybe LED grow lights have improved, but I'd need to see some proof of the spectral outputs compared against a Photosynthetic Active Radiation (Par Rating) chart. My guess is that pound for pound you're still better off with HIDs or fluorescents. You're certainly not going to get any better performance for less money with LEDs, they're not cool or cold despite common misconceptions. But it's not out of the possibility to get better with LEDs, but I don't believe they offer any significant advantage.

Originally Posted by Gold3nku5h

The color spectrum to grow with is easily changed with them as its just a matter of rendering, instead of figuring out which gasses do what when and how. Already there are grow light LED's that are fully usable by plants, you may have seen ones that wern't specific to plant growth.

This is incorrect in so many ways. Please feel free to disregard anything this person says about lighting. I just cringe at the inaccuracy. I'm not sure this person even knows what "rendering" means. In context of lighting, it refers to "Color Rendering Index". "just a matter of rendering" makes no sense whatsoever. You can't just change the colors that a combination of chemicals make... They're part of the inherent nature of the element... And you can't "filter out" colors that aren't already in the light... you can't put a blue filter over red LED and get white light... not sure where this person was going with rendering.



LEDs are a combination of chemicals just like any other lighting technology. They are actually the most difficult to change of all! They are set in stone by the process of creating the LED, because the different fabrication processes to grow these crystals (which LEDs are basically crystals) with electrodes attached, you would need a whole different set of machinery to grow the LED crystals of a different set of chemicals... That's glazing over the technology, but the point is with fluorescents or HIDs, it's like adding a little more spices here or there to the same capsule... I'm not sure why this is pertinent to what the best lighting is for orchids, but it seemed in need of correction.



If you want to see the various LED outputs, you can see them at the LED Museum :

The Led Museum

If you go into the site, you can see under "Discrete LEDs" which "combinations create each color, i.e.

Silicon Carbide = 485nm (a light blue color)
Gallium Nitride and Indium Gallium Nitride =445-485nm (dark blue)

DISCRETE (3mm-10mm) LEDS
700-4900nm NIR & Infrared
640-700nm Red
625-640nm Orange-Red
615-625nm Orange
600-615nm Amber
585-600nm Yellow
555-575nmYellow-Green
515-540nm True Green
490-510nm Blue-Green
485nm Sky Blue SiC
445-480nm True Blue (1)
445-480nm True Blue (2)
430-440nm Deep Blue
395-420nm Violet
341-395nm Ultraviolet (UVA)
240-340nm Deep Ultraviolet (UVB & UVC)

These combinations create 1 narrow spectral band. (see pic below)
White LEDs are nothing more than a blue LED with a phosphor coating EXACTLY LIKE FLUORESCENTS... so really you should be calling your white LEDs, fluorescent lights, not LEDs... (playing devil's advocate).

The only difference is how they illuminate the phosphors, whether a gas inside a fluorescent tube or a chip combination.

[terryros]

I would second Ray's comment. For the home indoor grower, we need the plants and flowers to look as natural as possible to be happy. We also need control of heat generation/power consumption and the height over the plants that we can have the lights. If a natural white LED can accomplish this and give acceptable growth/flowering, I will be satisfied.

[Ray]

Back to the "lumens per watt" subject for a moment, if we bring our thoughts to PAR (photosynthetically active radiation) one could argue that if you choose your LEDs to match the chlorophyll absorption spectrum, including matching the relative intensity to the absorption curves, the LED lighting would be THE most efficient, as they would be 100% PAR, with none of the light energy is "wasted" on the other parts of the spectrum - something that cannot be said of any other light source.

Then there's the energy efficiency - of the input power, how much is converted to light and how much to heat - sure they generate heat, but I still think an LED has the advantage.

[ginnibug]

My husband says he really doesn't know of any that are working to improve flourescents. He uses only LEDs to make lights for racecars and says the LEDs have improved drastically. He says the company that is always on the cutting edge for LEDs in Cree. They are always improving. CREE | LEDs for the LED Lighting Revolution If you go to their press releases on their site it gives you up to date info.

Now, Why my husband hasn't made me a grow light out of new LEDs , I DON'T KNOW? I think he's too busy with the cars!!! ginnibug