"LED Lighting Technologies to Substitute Natural Light

To substitute natural light is quite difficult also if you consider how hard it is to obtain light near the visible part of the spectrum with traditional luminaries. Light emitting diodes are here to change that difficulty.

SSL (solid state lighting) is the youngest lighting technology and by now is believed to be more efficient than incandescence and fluorescence due to the fact that SSLs produce light at or near the visible part of the spectrum and as a result the emitted light can be used straight or with minor conversion. One of the most important advantages is that SSL technology has eliminated damaging components from the light sources (remember: light emitting diodes contain no ultraviolet unless they are produced as UV LEDs).

NASA is already using SSL in its space farming systems. The reasons are quite simple: incandescent or fluorescent lamps are not efficient enough for such purposes, because they consume a lot of electrical power, generate heat and contain electrodes that burn out (maintenance costs are high). This is why NASA's plant physiologists started to work with light emitting diodes (blue and red) to grow salad plants such as lettuce and radishes. The researchers found our that blue and red light is essential for plant growth and, in general, a percentage of 8% blue LEDs and 92% red LEDs, both with the same frequency and relative intensity per LED, are enough for a harmonious evolution. Blue has a smaller influence than red; however a percentage between 1% and 20% of blue light can be selected, depending on the plants and their growth requirements....."
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