Thanks highzenburg, I try and sometimes get things
nearly right.
I'm using panels with 7 spectrums. So the light produced is magenta but its a mix of the following;
I.R 740nm Red 630nm, Deep Red 660nm, Orange 610nm, Blue 460nm, U.V 395, White 15 - 20,000k.
I'm using two different types of panel 6 produce the magenta type light and one has the same spectrum but in different ratio's and produces a much whiter light. The plants start off under the whiter light and progress through the flowering space.
Led's put out a lot less lumens than hps, but thats how they save energy, they only push light that the plant can use. PAR (Photosynthetically Active Radiation) is the part of the spectrum used for photosynthesis (400nm - 700nm) and is a far better measure of useable light available to the plants.
All the energy I put into the led units (except that used to drive the in built fans) is pretty much used to produce useable light, obviously a little is lost as heat.
Useful information;
www.sunmastergrowlamps.com/SunmasterPARWatts.htm[/COLOR]
PAR and Plant Response Curve
Just as humans need a balanced diet, plants need balanced, full-spectrum light for good health and optimum growth. The quality of light is as important as quantity. Plants are sensitive to a similar portion of the spectrum as is the human eye. This portion of the light spectrum is referred to as photosynthetically active radiation or PAR, namely about 400 to 700 nanometers in wavelength. Nevertheless, plant response within this region is very different from that of humans.
The human eye has a peak sensitivity in the yellow-green region, around 550 nanometers. This is the "optic yellow" color used for highly visible signs and objects. Plants, on the other hand, respond more effectively to red light and to blue light, the peak being in the red region at around 630 nanometers. The graphs below show the human eye response curve and the plant response curve. Note the vast difference in the contours.
In the same way fat provides the most efficient calories for humans, red light provides the most efficient food for plants. However, a plant illuminated only with red or orange light will fail to develop sufficient bulk. Leafy growth (vegetative growth) and bulk also require blue light. Many other complex processes are triggered by light required from different regions of the spectrum. The correct portion of the spectrum varies from species to species. However, the quantity of light needed for plant growth and health can be measured, assuming that all portions of the spectrum are adequately covered. Light for plants cannot, however, be measured with the same standards used to measure light for humans. Some basic definitions and distinctions follow that are useful in determining appropriate ways to measure the quantity of light for hydroponic plant growth.
Blue light by itself produces shorter plants (reduced internode lengths) which are dark in color. In contrast, red light produces plants with long internodes with softer growth (Nelson, 2003). A mix of both allows for good plant processes and growth.
As for cost, leds did seem to be falling in price earlier in the year but have seen a resurgence in costs as people seem to have rediscovered them to some degree and old companies are launching new more expensive led units. We have yet to see the high power 10, 20 and 50watt chips being utilised for commercial greenhouses, which should further reduce costs for all users, it really is just a matter of time.
I would like another 1000watts of led but the price is offensively high, i'm going to wait until after the outdoor season and hopefully we should see falling cost next year, tho the obvious solution is to build my own led as they are relatively cheap to produce as opposed to buy.
LEDs reduce costs for greenhouse tomato growers, study shows
Mitchell and doctoral student Celina GĂłmez experimented with light-emitting diodes, which are cooler and require far less energy than traditional high-pressure sodium lamps used in greenhouses. They got the same yield - size and number of fruit - with high-pressure sodium lamps and LED towers, but the LEDs used about 25 percent of the energy of traditional lamps.
http://www.purdue.edu/newsroom/rele...r-greenhouse-tomato-growers,-study-shows.html
