Hey guys! Just found these articles about the furture of LEDs. They are from Maximum Yeild Magazine. Just thought they were interesting and wanted to hear your thoughts! I do not use LEDs but this new technology sounds promising! Maybe some of you current LED users can share your experience. Enjoy!
This article is from the February 2010 issue and the title is: Next Generation of LEDs: The Diodes Strike Back
The last time we discussed LED (light emitting diode) technology for plant growth together, we looked at dual band (red/blue) light spectrum outputs in the 0.5 to one watt diode range. The overall output of the panels ranged from 45 to 90 watts. LED technology for plant growth is being developed at an accelerated rate, with much change in the technology occurring within a relatively short time frame.
In a previous article, I concluded that LEDs were a viable technology for providing artificial light energy to fuel the photosynthetic response (plant growth). However, there were some limitations. The dual band spectrum provided only red and blue light wavelengths. While these bands are where most of the photosynthetic response occurs, making LEDs very efficient, there is some other activity that occurs in other spectrums of the visible light bandwidth.
Imagine this: blue and red wavelengths of light are like the macronutrients, in terms of fertilizers, while other bandwidths are more like micronutrients. Micronutrients are just as important as macronutrients; the big difference is that they are used in much smaller quantities than macronutrients. So, its about supplying the correct and exact ratios of each. HPS and MH lighting produce huge quantities of their output in spectra that the plant uses very little of, making them much less efficient although effective because they are full spectrum.
Furthermore, the exact spectral output of the diodes, measured in nanometers (nm), has been fine tuned in next generation LED lighting so that the output occurs where the most light energy intensive reactions occur. In order to provide a complete, although not very intense, full spectrum light source with first generation LED grow lighting, the LEDs were supplemented with full spectrum CFL or T5 fluorescent lighting to meet the needs of the photosynthetic response on all the necessary wavelengths.
Quad Band LED Spectral Output (327 Watts)
When compared against the known photosynthetic response curve, quad band LEDs maximize the areas of highest photosynthetic activity in their output.
The result using the first generation LED lighting was a source of light for plant growth that used a minimal amount of electricity and delivered the required wavelengths of light to sustain healthy plant growth. It was also noted that different types of plants seemed to require different wavelengths of light at different times. The earlier LEDs were capable of producing healthy growth for rooting cuttings, young plants, seedlings and vegetative growth. The growth was exceptionally healthy and hard and supported relatively rapid development.
The first generation LED units provided an exceptionally cool running growing environment, which allowed for the use of supplemental CO2 enrichment to be applied very easily and cost effectively; further accelerating growth rates, plant health and yield potential. In our early test model, we were able to maintain CO2 levels of between 1200-2800 ppm in the growing environment by the use of fermentation in a sealed hydrohut (grow tent). Noticeably faster growth rates occurred, and the by-product of the fermentation, beer, was an added bonus. Not only was this set-up low in energy requirements, it was very economical and very quiet, an important consideration for those urban growers who live within close proximity to their gardens.
The earlier LED set-ups delivered good results relative to the amount of electricity they consumed, although HPS and MH High Intensity Discharge lamps seemed to win in terms of yield in the bloom phase. They also produced a lot more noise, heat and at least triple the electrical consumption when factoring all of the peripheral equipment required to manage the heat levels the HID lamps produced. To be fair though, if the earlier dual band lower wattage systems went watt to watt with the HIDS, they were capable of surpassing yields and crop quality in many types of plants. One drawback was that certain types of plants that had a definite finish in their life cycle sometimes took prolonged periods of time to ripen; this was attributed to limitations created by the dual band spectrum, although supplemental full spectrum fluorescent light alongside of the LED panels helped to improve upon this issue.
Due to their relatively lower intensity, and therefore limited ability to deliver high levels of light energy over distance travelled from the source of the light (diodes), it was recommended that those interested in gardening with such LEDs select auto-flowering plant varieties that mature under longer photoperiods and finish relatively shorter in stature, for example, less than 18 inches tall. This way, the plants were able to receive significant light levels from top to bottom, providing more consistent quality in all fruits and flowers harvested from the crop.
It appears that LEDs are ready to give your crop everything it needs for high yields and vigorous production in bloom.
So, here we are today, with the next generation of LED units for plant growth in hand. It truly is amazing to see how much the technology has improved and evolved in such a short time span. I was amazed at how bright the first generation units were relative to the amount of power they consumed. I was nearly blinded by the intensity that the next generation LED panels produced; and this is coming from someone who has spent far too much time around bright HID lighting!
1A-HPS VS Quad Band for Photosynthesis
Looking at this chart, we can see that quad band LEDs appear to be better tailored to the known photosynthetic response curve VS HPS lighting.
In fact, the model tested for this article draws approximately 586 watts of power, yet produces 30 per cent more initial light intensity than the sun, and has double the output of a 1000 watt HPS lamp at equal distances from the light source. These intensities have been carefully measured in the 610-680 nm range using a highly specialized light meter; this is where most of the photosynthetic response for reproductive (bloom phase) in a variety of crops occurs. Consult Chart 1-A in this article to compare the relative spectral output of this new quad-band LED growth technology to a horticultural HPS lamp, while also comparing to the known photosynthetic response curve.
Not only is this lighting technology incredibly bright, it has been engineered as a quad-band spectral output to ensure that all of the necessary wavelengths for all types of plants are being delivered, allowing plants to complete their natural life cycle similar to HPS and MH illuminated gardens. This is an especially important consideration for the ripening phase for crops in the bloom cycle. The unit featured here produces light in the following ranges: 455-475 nm (blue), 620-630 nm (red), 660 nm (far red) and bright white (full spectrum, 2700K).
There was never any question as to whether LEDs were effective for vegetative growth. It now appears that LEDs are ready to give the crop everything it needs for high yields and vigorous production in bloom: intense light levels in balanced spectral ratios while eliminating what the crop does not need - excessive heat. All of this with about half the power consumption in lighting alone, and significantly reduced costs in cooling equipment required and the relatively high level of electricity required operating energy intensive appliances such as ACs, chillers and industrial fans.
Not only are there more diodes in this unit versus the first generation of LEDs discussed, they are of higher wattages. The diodes themselves are approximately two watts each, although the power they are driven to is dependent on the individual spectral outputs engineered into each of the different LED chips on the lighting board.
These cutting edge LED chips are driven at much higher frequencies than previously with earlier diode technologies used for plant growth. The difference is significant. Now the chips can be driven at hundreds of milliamps instead of tens of milliamps; this fuels the process at which electrical current is passed through the chip and energy, called electro luminescence, is released. In laymens terms: bigger LED chip + more milliamps = very bright light versus first generation LED crop lighting. While more milliamps are being passed through the individual LED chips, the overall amount of power consumed is still relatively very low to the intensity of the light produced, making the next generation of LED crop lighting technologies very efficient.
HPS Lamp Spectral Output (1000 watts)
HPS lamps produce a lot of yellow and orange in their spectrum, falling short in the red and far red wavelengths relative to the overall output.
Now with all of this output, surely there must be a lot more heat? The answer is no, not really. Even at more than 10X the light energy output versus the earlier 45 watt dual band, smaller wattage diode panels, these higher wattage LED systems run incredibly cool relative to their light output, retaining all of the benefits from the first generation of LEDs while delivering a broader and more intense source of light for bigger yields and faster finishes.
As with the smaller wattage first generation LED units, the very small amount of heat that is produced by LED lighting originates mostly from the electronic driver that regulates the amperage (milliamps) being directed to the individual diodes in the arrangement on the light board. One difference, however, is that the high output second generation light system is heavier. The internal circuitry is cooled with several small computer-type fans. They run so quiet that they are barely audible, making second generation LED lighting systems much quieter than conventional core and coil ballasted HID lighting systems, as well as quieter than some models of electronically ballasted HID lighting systems. High power LED systems run cool for the amount of light they produce, so it is possible to construct a garden in a wider range of locations, because noisy fans and extensive duct work for cooling purposes are minimized or eliminated.
The space for growing crops does not require as much vertical clearance, or conversely, taller plants can be grown in rooms with height limitations. The high powered LED fixtures can be placed very close to the ceiling and the LEDs run cool enough that, if necessary, plants can grow very close the LED light source. Conventional HID lamps require significant clearances from the top of the plants to prevent overheating, and require significant clearance distances from ceilings for safety reasons. The additional clearance requirements for HID lamps can limit the vertical space for crop growth in tighter spaces as a result.
It would seem things are looking very promising for this latest generation of high-powered, quad-band LED crop lighting systems. In the next couple of installments, we will put the technology through its paces, and take some comparative measurements versus traditional indoor crop lighting systems such as HPS, MH and high output fluorescent lighting.
LED lighting for crop growth may very well revolutionize the way we grow plants indoors, and allow for just about anybody, in any type of space to be able to set-up a highly efficient and productive indoor garden so that anybody with an affinity for all things leafy and green may enjoy fresh healthy harvests of their favorite plants any time of year. Stay tuned for part two in the series to learn more about this rapidly evolving technology.
Here Is the follow up in the March 2010 Issue and it's titled: Grow Room Invasions: Next Generation LEDs II
For those of you just joining in, this is a continuation from part one in this series on high intensity and high output LED (light emitting diode) technologies as a light source for high yielding indoor gardens. In our last installment we discussed the benefits and the limitations of dual band diode lighting versus conventional indoor crop lighting systems like high output fluorescents, MH (metal halide) and HPS (high pressure sodium).
The earlier generation LED lights produced lots of light relative to the amount of power they used, ran very cool and eliminated wasted light wavelengths. However, they were unable to deliver very high intensity levels for larger, high yielding gardens and omitted the trace amounts of light wavelengths that certain types of plants seemed to require to fulfill their life cycles in a timely fashion.
Enter the higher wattage, very high output quad band LED crop lighting systems. By using higher wattages and more individual diodes/chips in the lighting board and driving them with hundreds of milliamps rather than tens of milliamps, the overall intensity is incredible. Coupled by the fact that there are 288 diodes/chips per fixture being tested, we had a 600 watt LED lighting system. We also discovered that these are not driven to their full capacity, so a 600 watt LED fixture is really only drawing about 327 watts of power. Amazingly, this provides light intensities that compete with 1000 watt HPS lamp in the 630 to 680 nm (nanometer) range, the light for flowering and fruiting responses.
Not only is this next generation of LED crop lighting much more intense than its predecessor, it also offers a broader spectrum while still delivering very efficient light wavelengths versus conventional light sources. The quad band lighting arrangement being examined has output in the following wavelengths: 455 to 475 nm, 620 to 630 nm, 660 nm and bright white (2700K; full spectrum). Note that there are higher ratios of red and blue diodes versus others, as this is where the majority of the photosynthetic response curve falls into. However, it still supplies the trace levels of all the bandwidths required. Also note that the quality of the red light is improved with this generation due to innovations in the manufacturing of the individual chips/diodes.
Chart one: LED VS HPS for Photosynthesis: Notice how much of the HPS lamps intensity is in the green and yellow bandwidths. These bandwidths are used in very small amounts for plant growth.
Someone who really knows their lighting may also notice that very little light would be produced in the 555 nm range based on the diode types listed above. At this nanometer rating, the light is mostly green; a bandwidth plants tend to reflect back more than absorb (thats partly why plants look green to us). Oddly, this is also the peak wavelengths we use to measure lumens (lm) and lux (lx) for growth. Growers have been using lm and lx to measure the intensity of their HPS and MH lamps; not really measuring the usable light for growth. Lux and lumens measure mostly green light, because these units of measurement were intended to be relative to how the human eye sees light rather, than the shades of the rainbow (spectrum) that plants use for photosynthesis (growth).
Upon consulting chart one in this article, you will see that when compared to an HPS lamp, the majority of the HPS lamps intensity is in the green to yellow (550 to 600 nm) range of light, while a considerably smaller percentage is in the blue, orange and red spectrums where most of the real action occurs. So, when we hold a light meter up to them and measure the lumens or lux, they appear to be giving lots of light for growth. More accurately, they are giving lots of light although as intensity; not very much where it is needed the most: in the blue and red portions.
Look at figure one. What you see is a high lumen (7130 lumens from over 12 inches away) rating from the veg model being tested. Now think about this: what you are seeing is the LEDs output in the lowest area of the spectral emission because the average light meter isnt measuring in the right wavelengths for LEDs/photosynthesis. This LED crop light was intentionally designed to have a low output in this range for efficiency.
This means that the reading should be considered much more intense for growth in terms of what it might compare to with MH and HPS lighting, because the majority of intensity is being measured in the 555 nm or green light range. With MH and HPS lighting, very little of the total output occurs in the blue and red areas where photosynthesis happens (HIDs are mostly in the yellow/green bandwidths). With LED lighting, the vast majority of the output occurs in the red and blue ranges with very little in the green (555 nm) area, making LEDs very efficient (and standard light meter readings deceiving).
Advanced growers know that vegetative plants will grow more vigorously with high levels of blue light and then produce larger flowers and fruits during the bloom phase with higher levels of red and orange wavelengths. If any lighting engineers are reading this, they are likely horrified to see a discussion of LED lights for plant growth in terms of lumens; the author recognizes that the majority of the light meters that most growers own measure in lumens or lux rather than PFD (photon flux density), Micro-Einsteins, PAR, etc.
In the end, seeing is believing, and if you plug in one of the newer high output quad band LEDs, you will be amazed at the intensity of light created; and perhaps even more amazed by the lack of heat produced along with the light. Make sure to have some protective glasses on.
Well how does it yield? Reportedly some test pilots in the State of California found the 600 watt quad band crop light to yield within +/- five to 10 per cent of a standard 1000 watt HPS lamp that used a high quality horizontal lamp reflector for the bloom phase. Obviously a lot more data is required before anything can be considered utterly conclusive; however, these early reports and findings are looking extremely promising.
Figure one: Intense LED lighting: Given how little of the LEDs output is in bandwidths that are measured in lumens, this reading suggests that this LED lighting system is incredibly intense (+7000 lumens).
As well, 600 watt high output LEDs are available in custom outputs and chip/diode ratios for improved vegetative growth characteristics and are even more efficient, as vegetative plants typically require lower light intensities. In short, this means you can cover more square feet of growing area in veg with a single 600 watt high output LED than you can in flowering; especially with specialized vegetative growth diode arrangements (see figure one for a comparison).
In the real world, which many of us are forced to live in, we must also consider the economic factors in terms of how viable high output quad band LED crop lighting systems are for indoor growers.
It is true that in North America, you can expect to pay near three times more for a high-output quad band LED system over a standard or a cost effective digital 1000 watt HPS/MH ballast, bulb, high quality reflector and cords. While that might stop some people in their tracks, take the time to consider the following.
The 1000 Watt HPS will draw about three times more power to produce the same light intensities in the bloom 610 to 680 nm range. In fact, the LED will produce a higher quality of red light in the bloom phase because the diodes/chips allow for light wavelengths to be tailored very exactingly. Little can be done to enhance the spectrum of HPS lamps, although the horticultural HPS lamps are superior to standard lamps. Now if you live somewhere where electricity is expensive, or want to run multiple lamps, the savings actually pay for the difference within a short time frame.
The above chart does not factor the replacement costs of HID lamps such as MH and HPS. Consider that every six months to maintain optimal light levels, the bulbs will require replacement. With the LEDs they will require no replacement at all for over 50,000 to 100,000 hours. To save you from doing the math, they will run for at least 10 years before needing replacement using a 12 hour lighting cycle. In the opinion of the author, it will take some time before growers in real world situations will be able to confirm these findings. However, it is clear that tremendous cost savings are offered in terms of lamp replacements, and more importantly, the cost of electricity.
Seeing is believing, and if you plug in one of the newer high output quad band LEDs, you will be amazed at the intensity of light created.
Also note that further energy saving can be achieved by choosing high-output LED crop lighting systems because little cooling will be required. With HID lighting systems, a lot of heat is produced by the lamps and ballasts. This has to be vented away, commonly with air cooled reflectors, vent fans and air-conditioners. Obviously, this all uses quite a bit of electricity. For the home gardener this means a bigger power bill and more noise with fans and ACs humming to keep the lamps cool.
For the commercial grower it means having fewer lighting systems on the same 200 AMP service versus using lower wattage and lower heat-output quad band high intensity LED systems. Thats right, because they use less electricity growers can run more lights safely per circuit. In an apartment, that might mean having three lights in a room where you could have only had one HID lamp. That is a quick way to triple your productivity levels, especially in smaller spaces.
So now we have more information on some of the potential benefits of using high-output quad band LED crop lighting systems: less heat and less electrical use means more efficient gardens and the capability to run more lights per circuit. In terms of economics, we have also examined the cost benefits when considering the cost of electricity and lamp replacement. In our next installment we will have a look at the emerging technology from the growing perspective. That is, how to tweak your garden for maximum yields when using next generation LED lights for plant growth. We will discuss modifications in temperature, humidity and CO2 levels that will not only make your LED garden more efficient, they will almost certainly make it more productive as well. Until then...
Here are the links to the articles
http://www.maximumyield.com/article_sh_db.php?articleID=530&yearVar=2010&issueVar=February
http://www.maximumyield.com/article_sh_db.php?articleID=539&yearVar=2010&issueVar=March
This article is from the February 2010 issue and the title is: Next Generation of LEDs: The Diodes Strike Back
The last time we discussed LED (light emitting diode) technology for plant growth together, we looked at dual band (red/blue) light spectrum outputs in the 0.5 to one watt diode range. The overall output of the panels ranged from 45 to 90 watts. LED technology for plant growth is being developed at an accelerated rate, with much change in the technology occurring within a relatively short time frame.
In a previous article, I concluded that LEDs were a viable technology for providing artificial light energy to fuel the photosynthetic response (plant growth). However, there were some limitations. The dual band spectrum provided only red and blue light wavelengths. While these bands are where most of the photosynthetic response occurs, making LEDs very efficient, there is some other activity that occurs in other spectrums of the visible light bandwidth.
Imagine this: blue and red wavelengths of light are like the macronutrients, in terms of fertilizers, while other bandwidths are more like micronutrients. Micronutrients are just as important as macronutrients; the big difference is that they are used in much smaller quantities than macronutrients. So, its about supplying the correct and exact ratios of each. HPS and MH lighting produce huge quantities of their output in spectra that the plant uses very little of, making them much less efficient although effective because they are full spectrum.
Furthermore, the exact spectral output of the diodes, measured in nanometers (nm), has been fine tuned in next generation LED lighting so that the output occurs where the most light energy intensive reactions occur. In order to provide a complete, although not very intense, full spectrum light source with first generation LED grow lighting, the LEDs were supplemented with full spectrum CFL or T5 fluorescent lighting to meet the needs of the photosynthetic response on all the necessary wavelengths.
When compared against the known photosynthetic response curve, quad band LEDs maximize the areas of highest photosynthetic activity in their output.
The result using the first generation LED lighting was a source of light for plant growth that used a minimal amount of electricity and delivered the required wavelengths of light to sustain healthy plant growth. It was also noted that different types of plants seemed to require different wavelengths of light at different times. The earlier LEDs were capable of producing healthy growth for rooting cuttings, young plants, seedlings and vegetative growth. The growth was exceptionally healthy and hard and supported relatively rapid development.
The first generation LED units provided an exceptionally cool running growing environment, which allowed for the use of supplemental CO2 enrichment to be applied very easily and cost effectively; further accelerating growth rates, plant health and yield potential. In our early test model, we were able to maintain CO2 levels of between 1200-2800 ppm in the growing environment by the use of fermentation in a sealed hydrohut (grow tent). Noticeably faster growth rates occurred, and the by-product of the fermentation, beer, was an added bonus. Not only was this set-up low in energy requirements, it was very economical and very quiet, an important consideration for those urban growers who live within close proximity to their gardens.
The earlier LED set-ups delivered good results relative to the amount of electricity they consumed, although HPS and MH High Intensity Discharge lamps seemed to win in terms of yield in the bloom phase. They also produced a lot more noise, heat and at least triple the electrical consumption when factoring all of the peripheral equipment required to manage the heat levels the HID lamps produced. To be fair though, if the earlier dual band lower wattage systems went watt to watt with the HIDS, they were capable of surpassing yields and crop quality in many types of plants. One drawback was that certain types of plants that had a definite finish in their life cycle sometimes took prolonged periods of time to ripen; this was attributed to limitations created by the dual band spectrum, although supplemental full spectrum fluorescent light alongside of the LED panels helped to improve upon this issue.
Due to their relatively lower intensity, and therefore limited ability to deliver high levels of light energy over distance travelled from the source of the light (diodes), it was recommended that those interested in gardening with such LEDs select auto-flowering plant varieties that mature under longer photoperiods and finish relatively shorter in stature, for example, less than 18 inches tall. This way, the plants were able to receive significant light levels from top to bottom, providing more consistent quality in all fruits and flowers harvested from the crop.
It appears that LEDs are ready to give your crop everything it needs for high yields and vigorous production in bloom.
So, here we are today, with the next generation of LED units for plant growth in hand. It truly is amazing to see how much the technology has improved and evolved in such a short time span. I was amazed at how bright the first generation units were relative to the amount of power they consumed. I was nearly blinded by the intensity that the next generation LED panels produced; and this is coming from someone who has spent far too much time around bright HID lighting!
Looking at this chart, we can see that quad band LEDs appear to be better tailored to the known photosynthetic response curve VS HPS lighting.
In fact, the model tested for this article draws approximately 586 watts of power, yet produces 30 per cent more initial light intensity than the sun, and has double the output of a 1000 watt HPS lamp at equal distances from the light source. These intensities have been carefully measured in the 610-680 nm range using a highly specialized light meter; this is where most of the photosynthetic response for reproductive (bloom phase) in a variety of crops occurs. Consult Chart 1-A in this article to compare the relative spectral output of this new quad-band LED growth technology to a horticultural HPS lamp, while also comparing to the known photosynthetic response curve.
Not only is this lighting technology incredibly bright, it has been engineered as a quad-band spectral output to ensure that all of the necessary wavelengths for all types of plants are being delivered, allowing plants to complete their natural life cycle similar to HPS and MH illuminated gardens. This is an especially important consideration for the ripening phase for crops in the bloom cycle. The unit featured here produces light in the following ranges: 455-475 nm (blue), 620-630 nm (red), 660 nm (far red) and bright white (full spectrum, 2700K).
There was never any question as to whether LEDs were effective for vegetative growth. It now appears that LEDs are ready to give the crop everything it needs for high yields and vigorous production in bloom: intense light levels in balanced spectral ratios while eliminating what the crop does not need - excessive heat. All of this with about half the power consumption in lighting alone, and significantly reduced costs in cooling equipment required and the relatively high level of electricity required operating energy intensive appliances such as ACs, chillers and industrial fans.
Not only are there more diodes in this unit versus the first generation of LEDs discussed, they are of higher wattages. The diodes themselves are approximately two watts each, although the power they are driven to is dependent on the individual spectral outputs engineered into each of the different LED chips on the lighting board.
These cutting edge LED chips are driven at much higher frequencies than previously with earlier diode technologies used for plant growth. The difference is significant. Now the chips can be driven at hundreds of milliamps instead of tens of milliamps; this fuels the process at which electrical current is passed through the chip and energy, called electro luminescence, is released. In laymens terms: bigger LED chip + more milliamps = very bright light versus first generation LED crop lighting. While more milliamps are being passed through the individual LED chips, the overall amount of power consumed is still relatively very low to the intensity of the light produced, making the next generation of LED crop lighting technologies very efficient.
HPS lamps produce a lot of yellow and orange in their spectrum, falling short in the red and far red wavelengths relative to the overall output.
Now with all of this output, surely there must be a lot more heat? The answer is no, not really. Even at more than 10X the light energy output versus the earlier 45 watt dual band, smaller wattage diode panels, these higher wattage LED systems run incredibly cool relative to their light output, retaining all of the benefits from the first generation of LEDs while delivering a broader and more intense source of light for bigger yields and faster finishes.
As with the smaller wattage first generation LED units, the very small amount of heat that is produced by LED lighting originates mostly from the electronic driver that regulates the amperage (milliamps) being directed to the individual diodes in the arrangement on the light board. One difference, however, is that the high output second generation light system is heavier. The internal circuitry is cooled with several small computer-type fans. They run so quiet that they are barely audible, making second generation LED lighting systems much quieter than conventional core and coil ballasted HID lighting systems, as well as quieter than some models of electronically ballasted HID lighting systems. High power LED systems run cool for the amount of light they produce, so it is possible to construct a garden in a wider range of locations, because noisy fans and extensive duct work for cooling purposes are minimized or eliminated.
The space for growing crops does not require as much vertical clearance, or conversely, taller plants can be grown in rooms with height limitations. The high powered LED fixtures can be placed very close to the ceiling and the LEDs run cool enough that, if necessary, plants can grow very close the LED light source. Conventional HID lamps require significant clearances from the top of the plants to prevent overheating, and require significant clearance distances from ceilings for safety reasons. The additional clearance requirements for HID lamps can limit the vertical space for crop growth in tighter spaces as a result.
It would seem things are looking very promising for this latest generation of high-powered, quad-band LED crop lighting systems. In the next couple of installments, we will put the technology through its paces, and take some comparative measurements versus traditional indoor crop lighting systems such as HPS, MH and high output fluorescent lighting.
LED lighting for crop growth may very well revolutionize the way we grow plants indoors, and allow for just about anybody, in any type of space to be able to set-up a highly efficient and productive indoor garden so that anybody with an affinity for all things leafy and green may enjoy fresh healthy harvests of their favorite plants any time of year. Stay tuned for part two in the series to learn more about this rapidly evolving technology.
Here Is the follow up in the March 2010 Issue and it's titled: Grow Room Invasions: Next Generation LEDs II
For those of you just joining in, this is a continuation from part one in this series on high intensity and high output LED (light emitting diode) technologies as a light source for high yielding indoor gardens. In our last installment we discussed the benefits and the limitations of dual band diode lighting versus conventional indoor crop lighting systems like high output fluorescents, MH (metal halide) and HPS (high pressure sodium).
The earlier generation LED lights produced lots of light relative to the amount of power they used, ran very cool and eliminated wasted light wavelengths. However, they were unable to deliver very high intensity levels for larger, high yielding gardens and omitted the trace amounts of light wavelengths that certain types of plants seemed to require to fulfill their life cycles in a timely fashion.
Enter the higher wattage, very high output quad band LED crop lighting systems. By using higher wattages and more individual diodes/chips in the lighting board and driving them with hundreds of milliamps rather than tens of milliamps, the overall intensity is incredible. Coupled by the fact that there are 288 diodes/chips per fixture being tested, we had a 600 watt LED lighting system. We also discovered that these are not driven to their full capacity, so a 600 watt LED fixture is really only drawing about 327 watts of power. Amazingly, this provides light intensities that compete with 1000 watt HPS lamp in the 630 to 680 nm (nanometer) range, the light for flowering and fruiting responses.
Not only is this next generation of LED crop lighting much more intense than its predecessor, it also offers a broader spectrum while still delivering very efficient light wavelengths versus conventional light sources. The quad band lighting arrangement being examined has output in the following wavelengths: 455 to 475 nm, 620 to 630 nm, 660 nm and bright white (2700K; full spectrum). Note that there are higher ratios of red and blue diodes versus others, as this is where the majority of the photosynthetic response curve falls into. However, it still supplies the trace levels of all the bandwidths required. Also note that the quality of the red light is improved with this generation due to innovations in the manufacturing of the individual chips/diodes.
Someone who really knows their lighting may also notice that very little light would be produced in the 555 nm range based on the diode types listed above. At this nanometer rating, the light is mostly green; a bandwidth plants tend to reflect back more than absorb (thats partly why plants look green to us). Oddly, this is also the peak wavelengths we use to measure lumens (lm) and lux (lx) for growth. Growers have been using lm and lx to measure the intensity of their HPS and MH lamps; not really measuring the usable light for growth. Lux and lumens measure mostly green light, because these units of measurement were intended to be relative to how the human eye sees light rather, than the shades of the rainbow (spectrum) that plants use for photosynthesis (growth).
Upon consulting chart one in this article, you will see that when compared to an HPS lamp, the majority of the HPS lamps intensity is in the green to yellow (550 to 600 nm) range of light, while a considerably smaller percentage is in the blue, orange and red spectrums where most of the real action occurs. So, when we hold a light meter up to them and measure the lumens or lux, they appear to be giving lots of light for growth. More accurately, they are giving lots of light although as intensity; not very much where it is needed the most: in the blue and red portions.
Look at figure one. What you see is a high lumen (7130 lumens from over 12 inches away) rating from the veg model being tested. Now think about this: what you are seeing is the LEDs output in the lowest area of the spectral emission because the average light meter isnt measuring in the right wavelengths for LEDs/photosynthesis. This LED crop light was intentionally designed to have a low output in this range for efficiency.
This means that the reading should be considered much more intense for growth in terms of what it might compare to with MH and HPS lighting, because the majority of intensity is being measured in the 555 nm or green light range. With MH and HPS lighting, very little of the total output occurs in the blue and red areas where photosynthesis happens (HIDs are mostly in the yellow/green bandwidths). With LED lighting, the vast majority of the output occurs in the red and blue ranges with very little in the green (555 nm) area, making LEDs very efficient (and standard light meter readings deceiving).
Advanced growers know that vegetative plants will grow more vigorously with high levels of blue light and then produce larger flowers and fruits during the bloom phase with higher levels of red and orange wavelengths. If any lighting engineers are reading this, they are likely horrified to see a discussion of LED lights for plant growth in terms of lumens; the author recognizes that the majority of the light meters that most growers own measure in lumens or lux rather than PFD (photon flux density), Micro-Einsteins, PAR, etc.
In the end, seeing is believing, and if you plug in one of the newer high output quad band LEDs, you will be amazed at the intensity of light created; and perhaps even more amazed by the lack of heat produced along with the light. Make sure to have some protective glasses on.
Well how does it yield? Reportedly some test pilots in the State of California found the 600 watt quad band crop light to yield within +/- five to 10 per cent of a standard 1000 watt HPS lamp that used a high quality horizontal lamp reflector for the bloom phase. Obviously a lot more data is required before anything can be considered utterly conclusive; however, these early reports and findings are looking extremely promising.
As well, 600 watt high output LEDs are available in custom outputs and chip/diode ratios for improved vegetative growth characteristics and are even more efficient, as vegetative plants typically require lower light intensities. In short, this means you can cover more square feet of growing area in veg with a single 600 watt high output LED than you can in flowering; especially with specialized vegetative growth diode arrangements (see figure one for a comparison).
In the real world, which many of us are forced to live in, we must also consider the economic factors in terms of how viable high output quad band LED crop lighting systems are for indoor growers.
It is true that in North America, you can expect to pay near three times more for a high-output quad band LED system over a standard or a cost effective digital 1000 watt HPS/MH ballast, bulb, high quality reflector and cords. While that might stop some people in their tracks, take the time to consider the following.
The 1000 Watt HPS will draw about three times more power to produce the same light intensities in the bloom 610 to 680 nm range. In fact, the LED will produce a higher quality of red light in the bloom phase because the diodes/chips allow for light wavelengths to be tailored very exactingly. Little can be done to enhance the spectrum of HPS lamps, although the horticultural HPS lamps are superior to standard lamps. Now if you live somewhere where electricity is expensive, or want to run multiple lamps, the savings actually pay for the difference within a short time frame.
The above chart does not factor the replacement costs of HID lamps such as MH and HPS. Consider that every six months to maintain optimal light levels, the bulbs will require replacement. With the LEDs they will require no replacement at all for over 50,000 to 100,000 hours. To save you from doing the math, they will run for at least 10 years before needing replacement using a 12 hour lighting cycle. In the opinion of the author, it will take some time before growers in real world situations will be able to confirm these findings. However, it is clear that tremendous cost savings are offered in terms of lamp replacements, and more importantly, the cost of electricity.
Seeing is believing, and if you plug in one of the newer high output quad band LEDs, you will be amazed at the intensity of light created.
Also note that further energy saving can be achieved by choosing high-output LED crop lighting systems because little cooling will be required. With HID lighting systems, a lot of heat is produced by the lamps and ballasts. This has to be vented away, commonly with air cooled reflectors, vent fans and air-conditioners. Obviously, this all uses quite a bit of electricity. For the home gardener this means a bigger power bill and more noise with fans and ACs humming to keep the lamps cool.
For the commercial grower it means having fewer lighting systems on the same 200 AMP service versus using lower wattage and lower heat-output quad band high intensity LED systems. Thats right, because they use less electricity growers can run more lights safely per circuit. In an apartment, that might mean having three lights in a room where you could have only had one HID lamp. That is a quick way to triple your productivity levels, especially in smaller spaces.
So now we have more information on some of the potential benefits of using high-output quad band LED crop lighting systems: less heat and less electrical use means more efficient gardens and the capability to run more lights per circuit. In terms of economics, we have also examined the cost benefits when considering the cost of electricity and lamp replacement. In our next installment we will have a look at the emerging technology from the growing perspective. That is, how to tweak your garden for maximum yields when using next generation LED lights for plant growth. We will discuss modifications in temperature, humidity and CO2 levels that will not only make your LED garden more efficient, they will almost certainly make it more productive as well. Until then...
Here are the links to the articles
http://www.maximumyield.com/article_sh_db.php?articleID=530&yearVar=2010&issueVar=February
http://www.maximumyield.com/article_sh_db.php?articleID=539&yearVar=2010&issueVar=March
Get it? I hate the idea of using lighting like HID that wastes so much E on the heat, plus its ventilation. Led power!! (Not yet, but in the future 
)
