@shibbyhockey04 Eddie, we actually have two Optical Engineers on staff from U of R. Lot’s of optical engineering with grow lights!
My guess, since you’re talking lumens, would be spectral shift of the lamp due to temperature. I didn’t think that HPS had much in the way of temperature dependence on spectrum, but a shift of a few nanometers at the edges of the eye’s luminosity curve can easily add up to 5-10% of lumen output. For umoles, the impact would be much less b/c all photons are weighting equally.
That’s what I was assuming was going on in the 5-10% loss. It’s been interesting to go from photometric units to radiometric units where I’m comfortable. Even looking at measures such as PPF where measurements are done based off photon count has been new and interesting.
I was reading through your technology and it’s really interesting stuff! The use of blue LED’s and phosphor coating to downshift into custom spectra is fantastic. Looks like you’re also getting a nice diffusion effect from particle scatter. When investigating the use of White LED’s,I read a few OSA papers on the degradation of the phosphor coating and what they were working on to improve it’s lifetime.
Could you possibly comment on what you’ve seen or experienced with the lifetime of the coatings and maybe talk about some challenges with phosphor coating in general? Really interesting application!
Unlike a sphere for small LED devices we use a 2m full sphere with the lamp centered in it. So the only losses are the holder of the lamp, which are compensated already when you calibrate the sphere.
A lamp typically gets a bit warmer in our HR96 reflector design, but specifically when compared to the more open reflectors. This doesn’t add any heat gain, but just a little shift of spectrum. Measuring in Lumens will give you a difference in output.
A rule of thumb about the inverse square law and point sources
An extended source, which any real world light source is, becomes a point source when the measurement distance is >5x the size of the source. For example, if the long dimension of a lamp is 12 inches, you can use the inverse square law if you are >60 inches away. This would work with a bare HPS bulb as an example.
The major exception to the inverse square law is when you use a reflector or optics as a means to collimate light. The intensity of light still diminishes with distance, just not as quickly. This is why a flashlight or spotlight still projects a bright spot at a distance.
Has your company developed or know of any new and interesting work being done with phosphor coatings for LED’s? I’ve seen papers talking about particle size and the efficacy related to this, some on degradation over lifetime and one interesting one from a few years ago on using glass-ceramic phosphors instead of polymer based phosphors. (Advances in glass-ceramic phosphors for white-light emitting diodes- A review, Chen et. al.,JECS 2015)
Just curious what challenges or advancements there have been recently in terms of efficacy, spectrum, or materials!
There’s constant innovation with phosphors as well as other materials like quantum dots. Transcend spends our time using these advancements to innovate downstream like remote phosphor systems or unique phosphor recipes (this is quite difficult actually, you can’t just layer different phosphors together like a sandwich and get good results, some of this has to do with particle size, which you mentioned).
You are right though, there are several material advancements in phosphors in recent years. These have improved color stability, reliability, efficiency etc… Some very important patents have also entered the public domain which gives access to previously unavailable materials.
Something interesting we’ve been looking at, and working with, for a little while now are systems with RoHs complaint quantum dots. QD’s have some really interesting properties, especially if you want narrow band light. You’re starting to see some versions of this technology pop up in high-end televisions.
Red shift is key for Bloom cycle. The Israel greenhouse cooperative at Ellat made a pink ploy plastic film that increased red shift beyond anything available at the time. and demonstrated that moving blooming plants from vegetative houses into finishing houses cut production time for azalea by 50%. The plastic was widely used in southern Europe, but never found much footing in the states a number of smaller growers made great use of the product. I will find some photos I have of Ellat greenhouse they where very large structures.
At peak times of the year they moved 4 to 6 747 a day from Israel to Amsterdam.
Excellent paper! Well written, good citations. I am following some of the citations out of pure curiosity. I want to have my nephew look at the paper when he returns to the states. He spent the last year in Taiwan, working on his Chinese at a university, while taking organic chemistry. He was interning in a lab group studying creating better LED’s
This definitely demonstrate the advantage of light absorption from high quality LED’s.
The paper leaves me with a few questions.
Can we find a paper that deminsrates inproved dry weight of plants grown under LED’s vs HID vs natural light? Dry weight, I think is the true measure of success. The cost benefit of lighting needs to look at this as the first measure success. The cost of ownership is important, but in my opinion it comes second to dry weight.
We know that a red shift during the flowering phase can improve the speed at which plants flower. But, there is a saturation limit to the light required to improve flowering in most horticulture crops. Do LED’s meet this saturation limit for cannabis?
Has anyone calculated the red shift saturation limits in cannabis?
Do growers see a difference in flowering times in verities with high levels of carotenoids vs plant with lower levels of carotenoids? Other horticulture crops with high level of carotenoids show delayed flowering verses verities with lower levels. High levels of carotenoids are reflecting more red light. I can give you citations in flowering crops if you would like.
we are drifting a bit Ethan, but for photosynthesis the spectrum doesn’t make any difference. Bruce Bugbee demonstrated that already many years ago and you can repeat this experiment easily. Probably shared this document a few times already. bugby light sources.pdf (609.0 KB)
For the development of the plant the spectrum does matter. See this research using a plasma lamp (and a few other sources) to simulate sunlight. The effects however are mostly morphogenetic, bringing the plant in a better position to more effectively use the available light:
Hi my build greenhouse and installed cover uv allowing the high light crops such cannabis and cut flowers
and other crops benefit with UV I Know you are into lights even natural light green houses need supplemental light.c(allows UV)
poly carbonate (inhibits UV)
would like to hear what anyone experiences are or Knowledge for my greenhouse growing Friends
Thank
Mark
Mountain Shore Inc
