Cheap T5HO "Plant" bulbs and longevity

[TyroneGenade]

My dataset has PAR/W but I prefer to think in microE as there is some debate as just what PAR is (I agree with your definition that distinguishes between PAR and PPFD).

I suspect the issue is with the efficiency of the conversion of UV to photon X, Y & Z via the phosphors, with the electrons being energized to the lower orbitals (and releasing lower energy photons) when they fall back to their proper orbital instead of being fully energized to the orbital needed to release high energy photons. (So I concede my original understanding is wrong and you are helping me think a bit better about this.)

Cool whites have PAR/W of 0.94. The average in my dataset is 0.87 so 0.72 isn't particularly bad. Gro-lux (3rd row in the plant pic above) is 0.55 and it is better than CWs are growing plants. I don't think PAR/W is a good indicator of the efficacy of a lamp for growing plants.

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[Ray]

Naoki - here's my take on it:

In all cases, light is emitted when electrons - excited to escape their electron shells by whatever energy input is around - fall back to their "normal" state.

Blue light is always the result of more energy being released on that fall-back than is red, so must have had a greater energy input to start with. I have no doubt that is equally true with phosphors and filaments.

Yes, the UV energy emitted by the mercury vapor as its electrons collapse is uniformly applied to all the phosphors, but the tungsten atoms in a filament are all getting the same amperage, aren't they? if it's low, you get predominately red; if high, blue gets added. I have no doubt that blue-emitting phosphors require more energy input than do red-emitting ones, and the UV energy is plenty for both - it's all about blending percentages.

Incidentally, for those of you with a full PC keyboard with number pad to the right, left-ALT + 230 on the number pad = µ