Use a 12 position Nob check out "3in1 dimming" thread from stardust.
Here I gave you a scientific study showing you that LED need at least 80F ambiant Temp to achieve a good efficiency, maybe even 84F is using monos. I wanted to discuss if really more efficient light means more efficient overall system, and if efficiency is still the limiting factor in our set up...
I will make an example to illustrate better the point I want to discuss:
I have a 1x1x2m box. I maximise my light because I have a high Co2 level in my place and I want to make as much weed as possible in my box. So I need about 350W PAR (about 1500PPFD with 3500K cob). I also need extraction for my plant to breeze, say the minimum is to extract the volume of the box every minutes it make about 150m3/h
In terms of parameters I want 85F for ambiant temp, not less, otherwise, as the paper show, Leaf Surface Temperature become too low and it photosynthesis drop.
I want to achieve all these ideal parameters and spend the less possible money - investment and elec bill needs to be taken into account.
So
- I get a 40% eff LED lamp, I will need 875W of light in my room, and I will get 525W of heat.
- I get a 50% eff LED I will need 700W and get 350W electricity bill goes down by 20% here, initial investment goes up.
At this point we make the assumption that this to light enable me to reach this 84F temp, hence I better go with the 50% eff LED. We all agree !!!
But now let's continue the race as it is happening,
>>>>>3. I go for 65% eff LED lamp, then I use only 540W that give me 188W of heat. I put a lot of initial investment because it is way more expensive than 50% eff, but electricity bill is reduce by 22% compare to 50% eff and 38% from my initial 40% eff Light so I will recover my money. Great !
Problem, there is not enough heat with only 188W, my temp in the room goes down to 80F, the plant grow less and they don't use the 350W of PAR light as efficiently as before.
Ouch !!! It means I invested a lot of money to get 5% more efficiency but because of f... Temperature my plants grow 5% more slow... Operation is null and I losed money. Even worst, if race continu to the point temperature is too low, I might pay a lot of $ for 5% percent but the plant will have a metabolism reduced by say 10 or 15% percent.
Why is that ? because the limiting factor here is temperature ! not light, not Co2 not any thing else anymore.
Solutions ?
I decrease the extraction =>> no, we assume it was already at the minimum.
I add heater => it add cost, electricity bill, and my 65% efficiency LED costed me a lot more money than the 50%...
reduce LED efficiency => less investment, more electricity bill but ideal on all the other parameters. It is called a hit, the sweet spot. It will be different for different application, but again I think 65% efficiency might not be better than 55% depending of your case.
Now let's find this sweet spot
