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#1
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LED's as substitute for HPS
Hi,
I read about some NASA experiments with blue and red LED's for growing vegetables in space. Anyone here who has experience with this? In times when everybody is complaining about the price of electricity it seems natural to think about replacing all kinds of lamps with LED's. But then there is the question of effeciency and wave lenghts. I read that in principle plants only need blue and red light to grow and prosper. If I remember correctly it was 450 nm and 675 nm light that was most suitable. But what about IR and UV? No other wave lenght? Plants don't need that at all? And if this information is correct, what is the right balance between those 2 components. I have seen conflicting information. In one case they said the red-blue ratio should be 3:1, while others say almost the opposite. I want to run some small tests with some very fast growing plants, preferably edible. Any suggestions what vegetable/herb would be most suitable? Ron Norway |
#2
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LED's as substitute for HPS
On Sun, 3 Feb 2008 13:45:47 +0100, "Ron"
wrote in part: I want to run some small tests with some very fast growing plants, preferably edible. Any suggestions what vegetable/herb would be most suitable? Ron Norway For fastest growing edible plant I nominate lettuce and for the fastest herb basil. Both are available in many varieties, including dwarf forms, and both are easy to grow. |
#3
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LED's as substitute for HPS
In article ,
Ron wrote: I read about some NASA experiments with blue and red LED's for growing vegetables in space. Anyone here who has experience with this? In times when everybody is complaining about the price of electricity it seems natural to think about replacing all kinds of lamps with LED's. But then there is the question of effeciency and wave lenghts. I read that in principle plants only need blue and red light to grow and prosper. If I remember correctly it was 450 nm and 675 nm light that was most suitable. But what about IR and UV? No other wave lenght? Plants don't need that at all? Many plants use the shifting balance between 'red' and 'far-red', i.e. near IR to 'measure' day length and 'decide' when to initiate flowering. For vegetative growth, most plants have auxiliary pigments that let them get substantial benefit from wavelengths outside those that chlorophyll is most responsive to. This is especially apparent in aquatic plants that usually grow in water tinted brown or yellow, and in understory plants that get heavily filtered light. So to some extent, it's the total amount of light, more than the frequencies, that counts. And if this information is correct, what is the right balance between those 2 components. I have seen conflicting information. In one case they said the red-blue ratio should be 3:1, while others say almost the opposite. Depends on the plant, and whether you're after vegetative growth or flowering. People grow plants under all kinds of artificial light with considerable success. I grow all the transplants for my garden under cool white fluorescents, which have a terrible spectrum -- mostly green wavelengths, although they look white to the eye, and they do very well -- as well or better than with the 'plant lights', expensive fluorescents that mainly emit blue and red wavelengths. Commercial growers use sodium and metal halide lamps, which also have skewed spectra. I want to run some small tests with some very fast growing plants, preferably edible. Any suggestions what vegetable/herb would be most suitable? I'd suggest lettuce -- it's fast growing, you don't want it to flower, and you can eat it. Buttercrunch is a small Bibb type that grows well under artificial light, at least for me. One winter I grew a lot under cool whites, just for something to try. Lettuce does best under cool conditions and doesn't require as much light as many other edible plants. I've seen panels of white LEDs, too. They are being used here experimentally as auxiliary street lights, and they are remarkably bright. Note that most LED lights these days actually emit UV, and phosphors are used to create the 'color temperature' or wavelength pattern, as with fluorescents. My guess is that LED lighting will replace compact and standard fluorescents in the fairly near future, once they get marketed to consumers and economies of scale kick in. I don't know whether they will replace MH and HPS before or after for commercial growers. Note that if you want to compare different combinations of blue and red, you'll have to compensate for different amounts of energy that actually reaches the plants' surface, since most wavelengths can be used to some extent, and some phosphors are more efficient than others in converting UV to the desired wavelength. If the color is produced by filtering through a colored coating, the difference will be even more extreme. So a light meter, at least, will be important for your experiments. You don't want to conclude that one color combination is better than another when what's actually happening is that the better combinations are just providing significantly more total energy than the others. Good luck, and let us know what you find out! |
#4
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LED's as substitute for HPS
skrev i melding ... On Sun, 3 Feb 2008 13:45:47 +0100, "Ron" wrote in part: I want to run some small tests with some very fast growing plants, preferably edible. Any suggestions what vegetable/herb would be most suitable? Ron Norway For fastest growing edible plant I nominate lettuce and for the fastest herb basil. Both are available in many varieties, including dwarf forms, and both are easy to grow. Thanks for the good suggestion. Lettuce is also recommend by the other one that responed, so that might be worth a try. I like basil very much, so 50-50? Ron |
#5
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LED's as substitute for HPS
Note that if you want to compare different combinations of blue and
red, you'll have to compensate for different amounts of energy that actually reaches the plants' surface, since most wavelengths can be used to some extent, and some phosphors are more efficient than others in converting UV to the desired wavelength. If the color is produced by filtering through a colored coating, the difference will be even more extreme. So a light meter, at least, will be important for your experiments. You don't want to conclude that one color combination is better than another when what's actually happening is that the better combinations are just providing significantly more total energy than the others. Good luck, and let us know what you find out! Many thanks for this in-depth answer. My plan is to make my own PCB's with series of blue and red LED's and eventually powering it up with a solar panel. Just for the fun of it. I'll start with a normel power supply, though. Chinese LED's are really cheap nowadays. Production of the PCB's costs me far more than the LED's. Though I still have concerns about the wavelength. Some suppliers are not able to give specific figures and they exaggerate the amount of light they produce! If they say 14.000 mcd, you better divide that by two. But still, at a price of about $0,07 a piece postage included it's not bad. Suggestions for even cheaper suppliers are welcome! What I would need, is a meter to measure the spectrum of the LED's. I saw one for $199,- but will need to do some further research to be sure that this is the right one for me. http://www.specmeters.com/Light_Mete...ght_Meter.html But I think that as long as I use blue/red LED's, I don't need to be concerned about the effects of filtering of the light, because there is no phosphor used in the pure colors. I suppose I would need at least 1000-2000 LED's to start with, quite acceptable if the experiments goes well, and I can use the panels for 50.000-100.000 hours. Thanks again, and I think I should make a website for this experiment. If so, I post a message on this list! Ron |
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