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LED's
Mar 15, 2008 22:46:12 GMT -5
Post by lenynero on Mar 15, 2008 22:46:12 GMT -5
Hi Lloyd,
You might be better served going with some more powerful LEDs .... The 14 watt kits I mess with that are all 5mm have 272 LEDs and barely covers 1 square foot and is not as good, from my experience as 5 .. 3 watt LEDs 2 blue,3 red.
38 LEDs 5mm would from my experience be good for a seedling .. but beyond that, not very useful. You would need at least 6 of these arrays to raise 1 tomato or pepper plant successfully.
I will post photos of my arrays if you want.
Leny
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Mar 16, 2008 0:14:13 GMT -5
Post by dvg on Mar 16, 2008 0:14:13 GMT -5
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LED's
Mar 16, 2008 3:16:44 GMT -5
Post by jonnybee7 on Mar 16, 2008 3:16:44 GMT -5
You might be better served going with some more powerful LEDs .... The 14 watt kits I mess with that are all 5mm have 272 LEDs and barely covers 1 square foot and is not as good, from my experience as 5 .. 3 watt LEDs 2 blue,3 red. So... the reason for this is that you can't just look at the wattage. Those 3 watt LEDs will have a much better lumens/watt output rating than the 5mm ones. correct? say a 3watt luxeon star for example would have more light output than 'x' amount of 5mm leds equaling 3 watts. and also those 272 5mm LEDs might cost you somewhere in the range of a $100. where as 5 luxeon stars would be in the neighborhood of $30-$40, not to mention less soldering. ;D I've found some cheap 660 nm. 0.5 mm. ones for around $38/1000. You sure about that price? The cheapest ones i found on mouser with 660 nm were 9 cents a piece. which is still $90/1000
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Mar 16, 2008 6:48:30 GMT -5
Post by lenynero on Mar 16, 2008 6:48:30 GMT -5
Hi Jonnybee7, I have found the best info on lumen's and watts has come from the dude over at greenpinelane.com. He has put together his measurements together here www.greenpinelane.com/lights_main_menu.aspxI can only give accounts of how my arrays have preformed and relate anecdotal observations.... I hope they are useful ;-) Leny
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Mar 16, 2008 16:25:21 GMT -5
Post by lloyd on Mar 16, 2008 16:25:21 GMT -5
I agree that the 3-5 watt ones are easier and cheaper per light output. However one source posted here said that you really need light at 660 nm and the high watt ones don't come in that wavelength. I'd rather go with fewer stronger lights. It seems the consensus here is to go with the high wattage led's. What wavelength and viewing angle are people using in the high power LED's?
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Mar 17, 2008 8:58:50 GMT -5
Post by lenynero on Mar 17, 2008 8:58:50 GMT -5
Hi Lloyd, I am waiting for Homegrownlights.com to come out with their high power kits... they also make a good 14 watt kit but you need like 4 of those kits to illuminate 2.5 square feet. They have sourced high power 660's I think they are cree Leds... www.homegrownlights.com/3wled.htmlBut in less then 2 weeks they will be releasing a high power LED kit for around 60 bucks... gonna see how many watts and what the coverage is like. Here is a link with the annoucment www.homegrownlights.com/future.htmlLeny
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Mar 17, 2008 12:23:27 GMT -5
Post by lloyd on Mar 17, 2008 12:23:27 GMT -5
Hi Leny, Thanks for the info. I'm going to wait a while and do some research. If you are going to buy the CREE ones let us know. Lloyd
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Mar 17, 2008 13:50:01 GMT -5
Post by briar on Mar 17, 2008 13:50:01 GMT -5
Lloyd, you prob looked at this already... but orbital technologies is the company that is working with NASA and JPL on LED systems for the space program, have a look at their current technology www.orbitec.com/projects/LGTLED/lgtled.htmHTH's Briar
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Mar 17, 2008 16:14:59 GMT -5
Post by lloyd on Mar 17, 2008 16:14:59 GMT -5
Thanks briar. The wavelengths they list are really weird. They don't use 660 nm. which is the main Chlorophyll A absorption line. Also they use green which is only for show. With their choices of colour you would expect a really poor result.
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Mar 17, 2008 21:38:35 GMT -5
Post by briar on Mar 17, 2008 21:38:35 GMT -5
just a touch of green has been shown to be beneficial, current thinking is that it increases intra-canopy performance, prob due to the fact that it is reflected more... but much more then just a touch reduces efficiency... I am currently trying out the LGM5, it uses a similar blend with similar ratios, I have just started using it, but so far I'm impressed. They have included a few orange, a single green and one near IR with every cluster if you haven't watched geocities.com/butchtincher/research1/ledmov.rar I highly recommend you do, prob the best single independent and unbiased ref on LED plant lighting that I know of, the newest research by NASA and JPL is showing the need for more then just single wavelengths of red and blue for long term health and optimal plant growth Briar edit: add pic here is the LGM-5 that I am playing with, this pic was taken from approx 5 feet from light, very intense light and notice the color blending, recommended distance to plants is 18-24" (prob for "cone" overlap requirements)
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Mar 17, 2008 22:04:23 GMT -5
Post by lloyd on Mar 17, 2008 22:04:23 GMT -5
Briar, could you email me the file? I downloaded it and the rar file is corrupted and will not decompress.
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Mar 18, 2008 7:41:35 GMT -5
Post by briar on Mar 18, 2008 7:41:35 GMT -5
LED RESEARCH Light-emitting diodes, LEDs, are a comparatively new light source for plant growth and are being actively investigated for numerous applications. Every week new articles appear in the popular press about advances in LED technology and the potential of this solid-state light source for automotive and home lighting, computing, public works light sources, etc. Red LEDs originally had 15-18% efficiency, but now are up to almost 22%, whereas blue LEDs were only 3-4% efficient and are now at 11%. This increase in efficiency makes LEDs competitive with other sources for plant-growth lighting (Tennessen and Ciolkosz, 1998; M. Bourget, 2005 Pers. Comm.). Another important advance in LED research is the commercial availability of “chip-on-board” LED light engines. Unlike discrete LEDs with plastic lenses, these light engines are small printed-circuit wafers that pack large numbers of small LEDs of selectable emission colors into close proximity. For example, the ORBITEC light engine can array 132 LEDs of five colors in a 6.25 cm2 square (Massa et al., 2005a). This allows for unprecedented color blending and very bright light levels. LED emissions are current-controlled, and the light output is directly proportional to input current within their operating range, so unlike other types of dimming systems for lighting, dimming of LEDs directly reduces power usage. LEDs have solid-state construction, are extremely durable, and resistant to shock. Transparent coatings on the chips protect them against high humidity and allow for cleaning without reducing light levels. LED chips, like discrete LEDs, have low mass and volume. LEDs generally emit light in a narrow region of the color spectrum. The number of available colors is extremely large, with one of the most efficient being red LEDs emitting at 640 nm, where light has a relative quantum efficiency for photosynthesis of ~96% (Sager and McFarlane, 1997). Experimentation has demonstrated that different species can be grown successfully under LEDs, including spinach (Goins and Yorio, 2000), lettuce (Goins et al., 2001; Kim et al., 2004), radish (Goins et al., 2001), wheat (Goins et al., 1997), and micropropagated potato plantlets (Miyashuta et al., 1995). Generally, about 15% blue light is required for normal growth, and yields have been achieved that are comparable to growth under white light (Yorio et al., 1998). Research has demonstrated that green light also can have beneficial effects for growth and plant assessment, especially within dense foliar canopies (Kim et al., 2004; 2005). INTRACANOPY LIGHTING FOR CROP GROWTH Intracanopy (IC) lighting aims to improve lighting efficiency by providing light distribution throughout the canopy of a crop. In planophile crops, where leaves present themselves perpendicular to overhead light and eventually close off their inner canopy to light, mutual shading of lower leaves by those above leads to net carbon loss via respiration, premature leaf drop, and often flower bud and fruit abortion inside the canopy (Ohler et al., 1996). Thus, unshaded top and side leaves end up doing all photosynthetic work for the entire crop stand. If the light sources could instead irradiate from within the canopy, a much greater percentage of available leaf surface could be utilized for photosynthetic work. This should increase biomass output per energy input efficiency. Additionally, light intensity drops off exponentially from a point irradiation source according to the inverse square law, where I = E / d 2 with I being the irradiation on a surface at a distance d from the light source emitting radiant energy E (Bickford and Dunn, 1972). Thus, light levels drop off rapidly with increasing increments of distance between lamp and plant, so that with the necessary separation of hot light sources above a crop stand the amount of light incident upon the leaves is highly attenuated, further requiring that the hot source be high-emitting and high power. If a much cooler light source can be maintained in close proximity to or even touching leaves, more light will be available at leaf level for lower power cost. This will lead to a greater energy-use efficiency of the biomass-production system. IC lighting has been previously examined, either as a supplement to traditional overhead lighting, or as a sole lighting source. Stasiak and colleagues tested soybean grown under microwave lamps and supplemented with side-mounted lighting that was piped into the canopy via glass tubes lined with optical lighting film to levels of at least 150 μmol m-2 s-1 PAR at 100 mm from the tube surface. When overhead light of 400-1200 μmol m-2 s-1 PAR was supplemented with inner canopy lighting, productivity increased 23-87% (Stasiak et el., 1998). Also, Tibbitts and Wheeler found that using fluorescent side lights or MH light pipes with overhead-lighted potato crops gave increases in tuber dry weights of 12-16% (Tibbitts et al., 1994b). Sideward lighting systems for production of plants from cuttings was developed to reduce the vertical PAR gradient found in overheadlighted propagation chambers (Hayashi et al., 1992; Kozai et al.,1992). One system used fluorescent lamps and it was demonstrated that sideward lighting reduced the electricity cost per potato plantlet produced from cuttings (Hayashi et al., 1992). Fluorescent lamps, however, take up a large volume of space, and they release heat that then has to be removed. To counteract these issues, Kozai and others (1992) used diffusive optical fibers as a light source for side lighting. This allows plant containers to be stacked, and also allows placement of containers near the light source, thereby increasing the efficiency of light capture and the vigor of biomass accumulation by plantlets (Kozai et al, 1992). If low-intensity IC lighting is used as a sole source of PAR starting from the seedling stage, Frantz and others demonstrated that expanding cowpea leaves adapted physiologically to become shade leaves, with lower lightsaturation levels and light-compensation points than plants lit with more intense light from above (Frantz et al., 1998). They used short, 15-watt fluorescent tubes G.D. Massa— Plant-growth Lighting for Space Life Support 24 Gravitational and Space Biology 19(2) August 2006 suspended within the crop canopy by monofilament and surrounded by transparent Mylar sleeves to prevent leaf scorch (Frantz et al. 1998; 2000; 2001). With IC lighting as a sole source, they found twice as much edible biomass production per unit energy input as in overhead-lit canopies (Frantz et al., 2000). The two lighting architectures combined, however, did not increase overall yield relative to input wattage, probably because the fixed-position overhead lights were underutilized until the plants grew to sufficient height (Frantz et al., 2000). Frantz and colleagues demonstrated that increasing lamp number within the canopy by 38% raised stand productivity by 45%, and that the highest energy-use efficiencies could be obtained by switching lights on higher up in a canopy as the plants increased in height (Frantz et al., 2001). When the data were normalized, plants grown under low-intensity IC lighting produced 50% of the edible biomass of those grown under highintensity overhead lighting but with only 10% of the total electrical energy input (Frantz et al., 1998). Further increases could not be accomplished, however, due to the volume occupied by the heat-shielded lamps – if more lamps were added to the canopy, the available planting space decreased. Those proof-of-concept studies with fluorescent lamps illustrated the need for a cool, smallvolume light source that will allow switching on of lights to keep pace with plant growth. Vertical, linear-arrayed LEDs were found to fit those requirements. LED RECONFIGURABLE LIGHTING ARRAYS The NASA Specialized Center of Research and Training in Advanced Life Support (ALS NSCORT) was created to develop technologies to lower the equivalent system mass (ESM) of an advanced life-support system (Drysdale, 1997). The crops focus area of the ALS NSCORT has entered into a collaboration with Orbital Technologies Corporation (ORBITEC, Madison, WI) to develop a reconfigurable LED lighting array that will significantly reduce the power and energy required to grow plants using electric lights. The development and preliminary testing of this lighting-array system has been described in previous publications (Massa et al., 2005a; 2005b). Briefly, the prototype system uses ORBITEC’s proprietary light engine, consisting of 100 chip-on-board LEDs set into a 6.25 cm2 square chip. There are sixtyfour 640-nm-emitting (red) LEDs, sixteen 440-nmemitting (blue) LEDs, and twenty 540-nm-emitting (green) LEDs on each chip. Additionally, there are two photodiodes. The green LEDs and the photodiodes are in place to accommodate future system-upgrade capabilities. The small size and close proximity of the LEDs allows for uniform spectral blending of photon emissions. Since the LEDs are current controlled, with the colors controlled separately, both the red-blue ratio and the light intensity output can be adjusted continuously. Twenty each of these light engines are mounted along a hollow linear support (approximately 3 cm wide x 1.5 cm thick x 65 cm long) that is attached to an electronics enclosure (approximately 5 cm x 12 cm x 10 cm) also containing two fans. Figure 1 shows such a “lightsicle”. The hollow design of the lightsicles allows air to be drawn through them from the bottom of the canopy past the circuitry controlling the LEDs and out the top of the enclosure, thus removing electrically generated heat from the vicinity of the plants. Each lighting array presently consists of 16 such lightsicles sized to light a growth area ~0.25 m2 and a growth volume ~0.15 m3. These arrays are currently configured to energize light engines from the bottom up, so that the lights can be switched on incrementally to keep pace with changing plant height. Fig. 1 A lightsicle for the reconfigurable lighting array with the major external components labeled. Each lightsicle consists of 20 LED light engines mounted to a tubular support, with associated electronics. Cooling air is pulled through the support past the internal electronics by fans mounted on the electronics enclosure. G.D. Massa— Plant-growth Lighting for Space Life Support Gravitational and Space Biology 19(2) August 2006 25 The electronics systems within the lightsicles communicate with a control enclosure via a Controller Area Network (CAN) communication system. The control enclosure allows the user to select LED power levels as well as the number of light engines energized to allow manual control that keep pace with plant growth. Red and blue LEDs have independent controls. Photoperiod is controlled by a programmable timer. The control enclosure also houses the system power supply and plugs directly into grounded 110 V power sources. Each lightsicle can be hung independently in a variety of configurations, allowing for flexibility in the intracanopy plant-growth arrangement. In addition, the lightsicle array can be reconfigured into a rectangular planar array consisting of 20 x 16 light engines for close-canopy, overhead lighting. Figure 2A and B shows lightsicles in intracanopy and overhead configurations, respectively. This close-canopy configuration is ideal for lighting rosette (e.g., lettuce) or erectophile (e.g. dwarf wheat) crops. The light array can be brought in close proximity to crop surfaces without scorching them, and after the development and integration of automated switching protocols, the energized engines will be able to track and mirror plant growth. Light engines positioned directly above each seedling will switch on automatically, and then adjacent engines will illuminate as the leaves of the seedlings are produced and expand until all engines are on. As with the IC lighting, greater efficiency will be achieved by not lighting empty space, but rather targeting lighting only where photosynthesis can occur. Fig. 2 A. Intracanopy LED lightsicle array with LEDs off. B. Overhead LED array with LEDs energized. C. Intracanopy array with closed canopy of cowpea plants. LEDs are not energized. D. Overhead array with closed canopy of cowpea while LEDs are energized. Note senescence of lower leaves. Plants in C. and D. are both 32 days old. G.D. Massa— Plant-growth Lighting for Space Life Support 26 Gravitational and Space Biology 19(2) August 2006 Five hardware tests were performed with the first prototype lighting array using cowpea crop stands. Modifications to the experimental design were made between trials 1 through 4 with incremental improvements in crop productivity achieved at each successive trial (Massa et al., 2005a). Figure 2C shows an example of an intracanopy-lighted plant canopy prior to harvest. Following intracanopy trial 4, the lighting system was reconfigured into a planar array, and a fifth trial was run using conditions identical to trial 4 but mounting the lights overhead (Fig. 2B.). In the overhead trial, all light engines were energized throughout the trial, while in the intracanopy trials, lights were switched on incrementally to keep pace with plant growth. To normalize the total power usage, the overhead lights were run at a current that was identical to the average daily current of intracanopy trial 4 so that the same total amount of electrical energy (99kW-h) was used during the month-long trial. In the overhead trial, we observed mutual shading and drop of the lowermost leaves, so that 11% of the total biomass senesced prior to the end of the trial. Figure 2D shows the overhead-lighted canopy prior to harvest. Overall, plants grown under overhead lights produced less biomass and had a reduced energy conversion rate than plants grown with intracanopy lights, with overhead-lighted plants averaging 75% of the productivity of intracanopy-lighted plants (data not shown). These trials were conducted prior to the correction of certain electronic anomalies reported by Massa et al. (2005a). In the first hardware tests, PAR output from the light engines was very low when only lower engines were energized, with a maximum of 100 μmol m-2 s-1 emitted from a lower engine with 5 engines energized. As more engines on each lightsicle were energized, the light output from each engine increased until more than 700 μmol m-2 s-1 of PAR were detected from the same lower engine when all 20 engines were energized at the same power level. Thus, when plants were young and only a few light engines were energized, the light emission from that engine was still very low, causing elongate growth and spindly stems of seedlings. This light-output issue has been rectified through a modification of the software controlling the light-engine drivers, and now we are able to obtain uniform irradiation from a given engine regardless of the number of light engines energized along the array. A second set of lightsicles has been constructed by ORBITEC, and tests are underway to examine IC vs. OH irradiation in a side-by-side experiment. An additional feature added to the second prototype array is an extension so that the control box is raised on 8 of the 16 lightsicles. This allows the shorter lightsicle electronics enclosures to nestle under the longer lightsicles, giving a much wider range of possible lighting configurations. Light-engine positions in the longer lightsicles are the same as in the shorter ones. FUTURE DIRECTIONS A canopy gas-exchange-measurement system is being developed specifically for IC LED lighting. A custommade, whole-canopy cuvette will allow real-time photosynthesis and transpiration rate measurements of an entire crop stand growing among the IC lights. Gas exchange will be measured as a function of environmental parameters such as light level, red-blue ratio, CO2, and temperature. This powerful tool will permit rapid optimization of IC lighting and growth conditions for a variety of ALS candidate crop species. A second research focus is being developed at ORBITEC under a Phase II SBIR from NASA for “High Efficient Lighting with Integrated Adaptive Control (HELIAC)”. This project focuses on the development of automated plant detection and light-engine switching using green LEDs and photodiodes embedded on individual light engines. Automation of the switching system to energize LEDs only when leaves are in front of light engines will conserve considerable energy by not lighting empty space, will maximize biomass production by keeping pace with plant growth, and will significantly reduce the personnel time involved with light operation. Additionally, these added capabilities will allow development of a close-canopy lighting system for targeted overhead lighting of erectophile and rosette crops. CONCLUSIONS When considering a light source for ALS, several important characteristics must be kept in mind: A variety of light sources have been evaluated from this perspective. LEDs, especially the relatively new chip-onboard LED light engines, appear to be optimal lighting systems for ALS crop growth for a variety of reasons. As a rapidly developing technology, electrical efficiency of these light sources continues to increase. In addition, the ability to precisely select a spectrum that is efficient for photosynthesis, growth, and flowering, the durable solidstate nature of LEDs, the relatively cool emitter surface, their long lifetime, tunability of the spectrum and irradiation levels, and ability to easily remove heat all combine to make this lighting type the best contender for ALS crop production. When the benefits of LEDs are coupled with techniques that apply light only where there is photosynthetic capability, the increased lighting efficiency will result in a significant reduction in the power required to maintain desired levels of biomass production, reducing the cost of growing plants in an ALSS, and bringing crop growth on Luna and Mars that much closer to reality. ACKNOWLEDGEMENTS The authors wish to acknowledge Mercedes Mick for help with lighting installation, plant growth, and data collection and analysis. We also wish to thank Bruce Bugbee and Ray Wheeler for helpful discussions, and Thomas Crabb and Charles Barnes for support and G.D. Massa— Plant-growth Lighting for Space Life Support Gravitational and Space Biology 19(2) August 2006 27 encouragement. This work was supported in part by NASA grant NAG5-12686.
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Mar 28, 2008 6:24:42 GMT -5
Post by Rick Hillier on Mar 28, 2008 6:24:42 GMT -5
I just set up a new set of shelves for both CP aquariums, starting my plants for outside (I know... I'm a bit late there) and a few dart frog terrariums.
I'm tempted to look into these LED lights, but I am wondering if anyone has actually tried them yet and what do things actually look like under them. While I want healthy plants/critters, I don't want it to look like it came from outer space.
>>> Rick <<<
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