Growing plants with leds is only a question of time. As leds perfomance raise and prices drops, it becomes more interesting.
Leds saves lots of power compared with traditional ways of growing. Leds are directionals, saving all the reflector loses. Leds permits desing a grow light wich only emit in the wavelenghts the plants uses better. Leds dont emit IR, reducing ventilation needings.
But when led grow lights will be a good choice depend on led's efficiency and price.
High Pressure Sodium bulbs are near 40% efficient converting electric input in active photosyntetic light (high watage ones). Now, best red leds are about 30% efficient. HPSs reflectors loses are about 25%, so the effective irradiance that leds and HPS give is very similar at same watts.
¿How much better is the red light promoting photosyntesis than white light?
Leds grow lights discributor's claims of 3x or 4x againts white light are false. Plants use all the PAR (photosyntetic active spectrum, 400-700nm) in a very flat mode, and the minimun (in green) are more than 50% of maximun (in red). Between white and red light, the max difference is about 25% more for red light. Its 1/4 more effective, not 3 o 4 times more.
But plants need blue light too, and blue leds are less efficient and more expensive. I dont see any wich reach 25%. And photosyntetic action of blue ligh is generally minor than white light average.
So, at actual perfomance, no less leds watts are required (compared with HPS). In best case, using very little blue leds, only a little less watts is the leds advantage. Insufficient to compensate the higher initial cost.
But things probably change in near future. I think leds efficiency of 45% will be reached in the next years, while leds price continue dropping. Then, leds grow light will be profitable (like general lighting leds).
Now, im interested in build a led array to do experiments with 2 plants, while waiting the moment leds will be cost effective.
But i dont find the appropiate leds. Best growing plants wavelenghts are 667nm (chorofill A absortion peak), 640nm (chl B peak) and 440nm(chl A and phototropism effects).
660nm leds are AlGaAsp, wich arent good for high intensity tecnology. I didnt see any AlInGap with that wavelenght (if anybody knows one, please tell me, i will be very grateful). And it is the most photosyntesis active wavelenght. CHl A is usually at less 2 times the content of Chl B. Now i have 1500 660nm leds, but soldering 1500leds is consuming me!
Most high intensity blue leds are 465-470nm peaked. There are some 450nm peaked (Royal Blue ones), wich can work, but i would like to find some with lower peak wavelenght (because more photosyntetic effect and because its supposed GaIn leds are more efficients as lower the peak wavelengh). Can anybody confirm this or report some blue led with 430-440nm peak? By the way, as FirstDsent note, those leds will be very useful for acuaria lighting (no IR, high directional beam perpendicular to water surface and the choice of putting leds near acuarium corners, below surface level).
