It is possible. We are coming out with a new LED T5 lamp where we can easily customize the output spectrum. It would be fun to work together to find out the ideal spectrum.
We build our own remote phosphor components and in some cases source components from companies like Intematix. We have a solid "side business" where we formulate and produce custom remote phosphor components for non general lighting applications.
For the recycling cavity we do indeed use WhiteOptics. We used Furakawa in our last design and have had success with both.
We don't have spectral tuning functionality at the moment but it's something we are working on. A number of customers growing fruiting/flowering plants have asked for this sort of spectral control. For non-fruiting plants there seems to be less of a demand. We plan on having a next gen remote phosphor design with spectral control within the next 12 months.
i would imagine spectral controls to be less useful for leafy greens. will the spectral controls be remote controllable? ie; an api over some type of wifi connection?
Yes, it has been tested. The industry standar LM-80 lifetime testing of the LED shows an L70 lifetime of ~300,000 hours. We are operating the LEDs at a lower temperature meaning they should theoretically last even longer. This is how we specify the 96,000 hour operating time to 90%
The Royal Blue LEDs we use have a ~55% EQE (external quantum efficiency). This gives a μmoles per joule a fair amount above 2.0. We lose a few photons during the conversion process and that drops us down to about 2.0.
We have a ~30% efficiency improvement over standard white LEDs because the phosphor is remote. The gain is 100% due to to the recycling cavity and omnidirectional nature of phosphors.
I'm still surprised at the level of efficiency, but glad to hear that you can back it up. I wasn't doubting that an underdriven LED would last that long, rather I was surprised that the remote phosphors would last that long without decrease in output. But reading more elsewhere, I now see that the lifespan of the remote phosphors can be excellent: http://www.digikey.com/en/articles/techzone/2014/apr/develop...
For others who are interested, here's another interesting link on the remote phosphor approach:
The exact figure in the last are already somewhat out of date, but if you plug in the specs for the newer LED's, presumably the underlying physics hasn't changed.
Phosphors are interesting in that they emit in 360 degrees. We have a "recycling cavity" behind the phosphor plates that reflects "backward" emitting photons. The design of this cavity is key to an efficient remote phosphor system.
As far as forward throw, the plate is a lambertian emitter. This means ~80% of the light is in a 60 degree beam angle and nearly >95% within 70 degrees.
If you already have a light-recycling setup for the phosphor - maybe you could additionally use brightness-enhancement films to use for light recycling in angular space. Just like in liquid crystal screens, BEFs could refract light rays with high exit angles back towards the phosphor, giving you a collimation of about 45° for rectangular, linear prism films.
But of course, conservation of optical étendue ('optical entropy' so to say) can't be cheated and absorption and scattering losses will be the trade-off for better collimation.
Etendue shouldn't be too much of a concern because we are emitting onto a relatively large space. We hadn't considered using a BEF but will certainly look into it.
Someone else mentioned using a holographic printed film for the same purpose of a BEF. Have you every used something like this?
Not personally - I've read about holographic films but they were rather for screen backlighting - you won't need that precision, I think. There are some advanced materials that are basically very advanced diffusers with a defined scattering distribution.
But BEFs are dirt cheap and do a very good job for this, your run-of the mill backlighting setup for screens is a very simple, effective system. Also: Using two linear BEFs (rotated relative to each other at a right angle) is more efficient than one pyramidal film.
The losses I mentioned are because of the light-recycling: You get lots more back reflections into the system - every ray that doesn't have the right exit angle gets reflected/refracted back into the system, the phosphor will absorb/re-emit/scatter, randomizing the ray's direction again and the ray 'retries' to get out of the system with a different angle.
These processes naturally induce losses (non-radiative decay in the phosphor, Fresnel losses at one of the BEFs, no perfect reflection on the back mirror). Even if you only lose a fraction of a percent, you lose that fraction lots of times before a ray may make it out of the system. It adds up - still, the collimation is very good for such a simple system (i.e. slap two films for a few dollars per sqm over your emitting area) it should be very easy to test.
Edit: You'll get the best collimation for 90°-angle prism films - there are other BEF types that'll smooth the angular distribution of the light recycling for wide viewing-angle displays.
Yes, we lose there is energy losses from Stokes shift. For example, when we shift from a high energy blue photon to a lower energy red photon we lose the difference in photon energy as heat. Blue LEDs are approx 55% efficient and red LEDs 35% efficient. Even with Stokes shift losses our fixtures end up being more efficient.
If, however, blue LEDs and red LED emitted at similar efficiencies our technology wouldn't work. We'd lose too much energy in the conversion. Luckily (for us) blue LED efficiency is projected to increase more quickly over the next few years than other colors (more R&D dollars behind them).
The numbers are heavily influenced by cost of electricity and time of use. Payback ranges from 1-5 years with an average user seeing payback in about 3.
Average 600W HPS lamps are 1.0-1.3 µmoles/watt. A complete fixture consumes 660 watts with ballast losses. They generally lose about 20% of their light due to reflectors (omni-directional lamp in a directional application).
This means that our 2.0 µmoles/watt fixture at 230 watt consumption can replace a 660 watt HPS fixture, provide the same amount of light, and have a nice payback.
Here's what I didn't get from your website: there are typically two wavelengths you're interested in for growing plants, depending on the phenological stage: a red and a blue (I can't remember the exact numbers, but the band is quite narrow). How can it be that your lamps have higher efficiency despite providing a complete spectrum? I don't know anything about light physics, hence my question; intuitively, I'd say you could have higher 'yield' by focusing all energy you put in to one wavelength (or at least, a narrow band).
It turns out that plants use more than just red/blue for photosynthesis. They do indeed absorb narrow bands of red/blue more strongly than other colors like green (this is why plants are green) but only absorb about 10% more efficiently.
The green light not absorbed is reflected. This gives the opportunity for green photons to reflect their way down to the bottom leaves for a more distributed growth.
We have built a number of lights with "focused" spectrum but haven't seen a benefit. In many plants, like "red" lettuces the leaves only turn red with a full spectrum (I have no idea why, a botanist might know the answer...)
We do see a benefit to skew the spectrum for many flowering/fruiting plants in later growth cycles and have a plan to come out with a "fruiting spectrum" in the future. This will part of our August Indiegogo campaign.
Interesting. I do admit that much of what I know comes from books written for growing marijuana, since until a few years ago those were almost the only (large scale) applications of indoor growing, and that most of that knowledge isn't very scientific (for example until a few years ago the mainstream technique to force bloom on mj plants was to vary the light cycle only). Research is frantic in the field, a fascinating development.
One last question if you don't mind: do you see a market for this in small scale operations, or do market pressures force your customers to grow always bigger like in the rest of agriculture? It seems that the only (sustainable) way to make a profit on growing food (plants and animals) is by scaling up.
(OK I lied, I have another question actually: with the pressure on lighting system vendors in Europe to screen their customers for illegal operations, and increasing pressure to hold vendors accountable for such use, are you experiencing that American vendors actually have a market advantage on this? Do you export to Europe? (meta: who would have thought just 10 years ago that in 2015 the US would become the world's leader on high tech marijuana production!) also sorry for focusing on mj, your industry suffers from its association with it, I know - it's just that that market was the only non-academic source of knowledge on it for so long)
It will be interesting to see how the market scales. There are certainly advantages to large commercial greenhouses etc... but there is a quickly growing trend for small local producers that grow a few hundred or couple thousands plants at a time. They might service a grocery or a few restaurants. There is also a trend for people to grow at home, grove labs was already mentioned in this thread as an example. My guess, ultra-efficient, nearly fully automated indoor production facilities will be a major player. Labor and energy are the two biggest costs to production and there are emerging technologies to address both of these.
Regarding Europe, it hasn't been a primary focus for us but we have exported a few orders to the UK, Germany and Netherlands. I hadn't heard of pressure on vendors to screen their customers. I'll have to look into this.
Our orders so far have split about 50:50 between veggies and marijuana. The marijuana side of the business does certainly seem to overshadow the veggie side as far as general public interest goes!
The major difference is upfront cost vs. cost of ownership. If you purchase the "cheap" multi-color products you will end up consuming MUCH more energy. The difference is much more than the upfront cost of the lights.
There are some well designed multi-color "pink" lights out there and there cost is similar to ours. A 325watt multi-color design has similar light output to our 230 watt remote phosphor design.
There are two reasons the light is the size that it is. First temperature. We have a passive heat sink with fins and a plastic remote phosphor sheet. Both have to stay relatively cool and more surface area makes this possible.
Its funny, the first fixture we built and sampled to growers was about 25x smaller. We used an active heat sink and a glass phosphor sheet. A common complaint was "why is this so small?" I want my lights to be "big and strong". We took this feedback and decided to move to passive design.
Our original logic was that smaller is better, especially in a greenhouse. The most efficient light is one that is off and the less shading of sunlight the better.
I think small lights could be a really good market for you, for all the urbanites like me, living in condos. Make a tiny kit that can grow herbs or lettuce at an accelerated rate using little power because of LEDs, and I'd buy it in a second.
As it stands, I think a 1m strand of TL-RL20 will be a purchase for me soon, and I'll build the kit myself.
It is possible. We are coming out with a new LED T5 lamp where we can easily customize the output spectrum. It would be fun to work together to find out the ideal spectrum.