This is a great discussion! Excellent points on many issues I have had questions on.
I am currently leaning towards LEDs in my application due to the heat reduction - less need for more heat management strategies, I have been impressed with the developments in the last 2 years especially. I first tested an LED light in 2009 and it was pretty pathetic. Now they are giving a good savings on not just the light energy, but also the supporting infrastructure needed and energy required. Maybe not as high in yield, but getting increasingly close.
However I am seeing increasingly the ceramic metal halides on the market using 315w-630w range. How do these new developments fit into the equation?
A 1000W HPS has as much heat gain in a room as 1000W LED or 1000W incandescent. In a closed room it doesn’t make any difference if you do not have a much more efficient light source.
The sun has 53% infrared radiation. HPS has a few percent more. The cooling capacity would be about the same - ask your climate control specialist.
The CDM 315 is a great lamp. I personally prefer the 4200K version for its spectrum, but it is not as efficient as the Agro.
Many of the reported yields per Watt are very true - but look at the yield per square meter and the costs of the fixtures and yearly lamp replacements. You need about 3.5 CDM 315s to replace a single 1000W HPS.
As I already remarked earlier: lower PPFD gives you a higher yield per Watt.
So the big question then. Does a 1000w HPS give the same result as a 1000wLED or a 1000W Incandescent.
With the new LEDs i have - I can flick a switch and it is running a bloom light mode, or a grow light mode, or both. To me that in itself is a savings in time and effort.
read the research… Of course it will not. But choosing a light source that has a lower efficiency (as in PPF/W) will give you less photosynthesis. The experiment was not about efficiency, but photosynthetic rates given the same PPFD.
So if I put a 1000w HPS with no fan in a room, and an out of the box 1000w LED in another identical room, then the ambient temps of both rooms will be the same after 12 hours run time?
And if those two have different outputs, what should we be comparing with? Does a 1000w HPS match a 1000w LED. Or as much of the LED marketing seems to say that a 1000w LED is more equivalent to say 1500w HPS.
nathan look up heat gain in HVAC systems. The efficiency of a light source doesn’t matter. Light doesn’t disappear, it converts into heat eventually. The light that is absorbed by a plant does not all get converted to chemical energy either. If I add 1000W of energy into a system, I must take out 1000W. So at same efficiency same power into the room for the same ppfd and same heat load.
btw did you know that it takes more energy to create a blue photon than a red photon, and that extra energy is not all used by the plant and dissipates into heat? Ergo: blue light will heat up our plant more than red?
Plants are photon counters. The energy of the photon is of no influence to the photosynthetic process. it takes about 12 photons to bind 1 CO2 molecule.
If you guys prefer I can split the discussion with @nathan around the LED lighting into a separate topic, if that makes things easier to keep track of.
I don’t mind. To me HPS vs LED is one of those issues I really struggle with. Both have their own unique benefits I think but it is great to get such detailed information from professionals such as @Theo and @clones
@Theo - that’s great feedback. I’m coming indoor from an outdoor and greenhouse background - testing to see what works but without the professional lighting background. Having more informed analysis to the claims is great which is why I think this thread is so important.
I would but we are getting much off-topic at the moment and I am already spending a whole free evening on a forum… time for a bit of quality time if you don’t mind.
You can share your thoughts whenever you are free, we are collecting valuable opinions on lighting science and would like to hear your thoughts on green light and Far red!
It’s a 513 W fixture supposedly replacing 600W HPS (which HPS? Lots of 600W HPS systems ranging from 1000 - 1190 umol s-1) and for a 4 x 4. This gives it away a little: that is probably at a much lower ppfd. We recommend about 500W per square meter for high intensity, but in a small tent you have much losses. LED has an advantage there as less light goes to the walls, so less losses. To light it uniformly though you probably need to hang it high over your crop given the 90-120 degrees “view angle” (how professional) - so probably a much tighter beam angle as LEDs typical have a lambertian distribution.
I don’t know, I haven’t seen any real PPF specs.
Again, remember: a lower PPFD will give you a higher yield per Watt, but you need more space. The nugs may not be as compact as with high intensity lighting though. Scrog recommended.
