The math shouldn’t be all that hard. I recommend anyone making a decision on lighting to double check manufacturer claims with some back of envelope calculations. You are about to spend a ton of money - interrogate you lighting supplier to the degree I’m about to pick this post apart. Lets dive into this a bit:
claimed that a 1000w HPS only makes 700ppfd
As for the 700 μmol claim, was this an average PPFD or peak PPFD? If you look at the PAR maps Nate put together for a variety of 1000W HPS bulbs, the measurements on the Philips Greenpower bulb suggest an average number around 650-700 μmol/m2/s despite a center of fixture reading of 1136 μmol/m2/s. I did a quick calculation on Nate’s PAR map and got something around 650 μmol/m2/s average across the canopy. I have attached this calculation to this post. 180905 Philips Greenpower HPS PAR Map calculation.xlsx (151.0 KB)
vs their light as 1200ppfd
If in theory you have a fixture with a total PPF output of 1700 μmol/s on a 4’x4’ canopy and you have no light losses (i.e. reflective walls all around the canopy) as well as a minimal hotspot under the fixture, you should be able to see approximately 1140 μmol/m2/s at canopy (4x4’ = 1.49m2; 1700 μmol / 1.49m2 = 1140 μmol/m2/s). This translation depends a lot on the optics and uniformity – the more prominent the hotspot(s) the faster this calculation falls apart. I can tell you that this is possible with the Samsung LM301B mid power LED, which might be the part Fluence is using.
Now of course in practice there will be some light leakage out of the sides of your racks, so your average PPFD will be a little bit lower than the total PPF divided by your canopy area. If you are considering a low profile fixture for multi tier cultivation, I recommend you look closely at the PAR maps at 6” / 12” / 18” and pick a fixture with the least amount of hotspot at these distances, otherwise you are missing out on many of the benefits of a large area fixture (less prominent hotspot).
We are preparing to announce a new product for large scale multi tier cultivation along these lines in the coming weeks.
We tested their deep 4x4 reflectors at the same wattage, and hit 4250 PAR at the same distance.
As for that 4250 number, this is a center of fixture measurement at 30”, correct? No matter how well that reflector is designed, the center hotspot will still be there to some extent at some distance. I recommend contacting Nanolux to understand the minimum distance at which the deep reflector is designed to function. It is possible that you are seeing a measurement at a focal point where many rays cross, and that the reflector was designed to be used at a different height to the canopy (ie greater than 30").
For the matter, we designed our FluxScale Reflectors to provide high uniformity at a minimum of 30”. I don’t know what other manufacturers are using for materials, but we import weather resistant and highly reflective sheet metal from Germany (Alanod Miro 9033AG) and make our reflectors in the US in accordance with our software optimized geometry.
I’m glad you mentioned UVB – we are working on some pilots with an innovative UVB technology, however we need to do a lot more work to understand the ROI of the UVB capability in relation to UVA Light Formulas, which are a lit easier to pull off due to the wide availability of high power UVA LEDs. I know @Growernick is interested in this – anyone else feel free to contact me!