Transcend (YC S15) Launches an Extra-Efficient LED Light for Indoor Farmers
techcrunch.com
techcrunch.com
Indoor farms, especially in Japan, have been using LED lights for a while. Red/blue combos, in the pink/purple range, seem to work best.[1] The big advantage of LED lighting is not the reduced power consumption, but the reduced heat. The lamps can be closer to the plants without cooking them, which means the trays can be stacked closer and the density of the operation goes up. For most non-druggie applications, the plants aren't that tall. So small, distributed lighting units are used, instead of huge ceiling lamps.
Some plants can be overclocked. They do need a light/dark cycle, but it can be shorter than 24 hours. The life cycle of the plant is then sped up.
[1] http://www.economist.com/news/science-and-technology/2160219...
Each light is 19 pounds and is about 10"x8".
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.
Typical LEDs used for illumination are blue LEDs with a phosphor coating to produce white. Transcend is doing essentially the same thing, but the goal is to produce wavelengths optimal for plant growth instead of a broad spectrum for illumination. The biggest difference in implementation looks to be that Transcend is separating the phosphor from the emitter while most LEDs used for illumination bond the phosphor directly to the emitter.
In theory these lights change everything, why grow peas in Kenya, put them on a plane and send them 1/4 the way around the world when a greenhouse in the Home Counties will do nicely?
The cannabis angle is pretty good too. As things stand growing those plants takes a stupendous amount of energy with all the problems of ventilation, mould growth, noise from the ventilation and the need to 'not get caught'. With this technology those that can hold down a job can get growing their own without having to have the huge 'leccy bill or having to be friends with dealers.
I like the lateral thinking of tuning the light to suit photosynthesis by using phosphors, I am surprised that has not been possible before. One day this will seem so obvious yet it wasn't until this product came along.
You are worried about air miles, but are willing to accept artificial light?
Do you just want to feel like you are being environmentally friendly, or do you actually want to be environmentally friendly?
I've been surprised at how many people only want to feel that way, but don't actually care about being environmentally friendly. (A good example of this is locavores.)
> of tuning the light to suit photosynthesis by using phosphors, I am surprised that has not been possible before.
It has been thought of before, people have been doing it for decades. This is just an incremental improvement.
LED lighting use more, even without doing the calculations I feel quite confidant in saying that it uses much more.
With a single trip 100m trip, the LEDs lose. With 10^7 100km trips, the LEDs win. The question is where the line is, and the answer is that it's going down all the time.
Hu? You are planning on shipping a single tomato 621 million miles? That's enough to ship it to Mars and then back.
Why in the world would you do that? Wouldn't it spoil?
You know you have to pay to power the LED, right? It's not just equipment cost? It takes less energy to grow a tomato in the sun, then fly it somewhere then it does it grow it indoors with artificial light.
And no, LED efficiency is not going up all that much anymore - there are physical limits to that.
If you only ever grew one tomato then you probably could buy a cheap plane ticket to deliver it, for less than the lights. So you'd be right, the LEDs would use more energy (cost to make, ship, and use) vs the delivery charges for the sun-grown (free energy) tomato from farther away - even if shipped expensively.
But if you grew millions of tomatoes from the same LEDs then you'd be wrong - now buying the grow lights is much more efficient than shipping in sun-grown tomatoes from even a few kilometers away.
How many tomatoes are you going to grow?
You keep focusing on buying the lights, but I'm not talking about that. I'm talking about running the lights.
Each of our remote phosphor fixtures are rated to last for 96,000 hours to 90% output. That's over 10 years of 24/7 use.
How has this been tested? And if it is true, why is there a 5 year warranty rather than a 10 year? And what level of decline in output is covered by the 5 year warranty?
Efficiency: >2.0 μmoles per watt
Presuming you mean "per joule" rather than "per watt", this is very close to the claimed efficiency of the underlying Royal Blue LED, and (I think) much higher than any white LED. While I can believe there is some benefit from the lower temperature of the remote phosphor, this would be a remarkably high number for a full spectrum light. How has this been measured?
I don't think growing lights are full spec
In theory, you can get a significant gain in efficiency by choosing specific wavelengths. In practice, it's difficult figure out exactly what these wavelengths should be, and to match them to existing high efficiency emitters.
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.
For others who are interested, here's another interesting link on the remote phosphor approach:
http://www.ledsmagazine.com/articles/print/volume-9/issue-7/...
And a nice overview of the efficiencies of white LED's, and where the losses usually are: http://www.sandia.gov/~jytsao/SSL_Trajectories_Proc_IEEE.pdf
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.
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.
Argh.
Plants require light at 450 nm (blue) and light at 650 nm (red) to experience normal growth, and 730 nm (far-red) is also required to flower normally. (That last one may be important to growers of certain plants valued for their flowers and/or fruits.)
Phytochromes and photropins are the plant pigment-hormones that govern the plant life cycle. They respond to those 3 critical wavelengths of light to allow the plant to guess the time of day and the season of the year. Some plants also need a dark phase to "sleep", but it doesn't have to be as long as an actual night.
Blue light is likely most efficient at forcing the increase in green plant mass. That is, it makes bigger leaves and longer stems. That isn't always what you want for indoor farming.
The ideal indoor grow light would have a programmable, timed output of those three critical wavelengths of light, with a different ideal program for each type of plant. You may wish to start with red light, to germinate the seeds, go to blue light for rapid growth, then manipulate the plant into flowering out of season by switching between the two reds.
Transcend also needs a smaller, programmable 650/730nm light to offer a complete indoor farming solution, particularly for plants that do not get natural sunlight. It wouldn't need to use nearly as much energy, as it is being used primarily for hormonal signaling rather than photosynthesis.
Context: "The company has developed a wavelength conversion system that uses phosphorous to convert blue photons, which are the most efficient type of photon, into any other color photon."
But the highest efficiency color for LEDs to produce largely depends on what Cree and Nichia are doing this year. Unfortunately, most of the readily available numbers tout luminous efficiency rather than raw light power. That's fine if you're looking for a reading light, but chlorophyll does not have the same absorption spectrum as the opsins in the human eye. You have to look for "wall-plug efficiency", which is less commonly reported.
So with respect to photons emitted per watt, I'm not sure which LED chemistry takes the prize. It depends on the temperature and input power, too. You can achieve 200% wall-plug efficiency, but only if you're converting picowatts of electricity into picowatts of photons in a hot LED. This is not possible (economically) for grow lights.
The benchmark for grow lights is the low-pressure sodium lamp, at about 38% efficiency. LEDs maybe get 30-65%, considering transformers, internal resistance, quantum efficiency, reflective losses at the die-capsule interface, etc. Higher efficiency comes from more expensive components.
As for chemistry, InGaN efficiency drops at longer wavelengths, and AlInGaP efficiency drops at shorter wavelengths, leaving a big efficiency trough in the green range. (Fortunately for this, plants don't need green.) I suspect that AlInGaP LEDs in the orange range are more efficient than visible blue InGaN LEDs, but this is hard to show with a lazy web search.
So when you say "most efficient" you really have to be very explicit about the application. That was my implied complaint about that sentence in the article.
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, 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).
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?
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.
High pressure sodium lamps (apparently the norm for indoor commercial food growing) look to be about 1.8µmoles/watt, compared against the ">2 µmoles/watt" of these lights, well, its going to take a long time to save $1000 in energy on a 250 watt lamp.
Lamp lifetime may tip the scales in favor of these LED lamps. Lamp size may also help, I used a 600 watt high pressure sodium lamp in my calculation against the 250 watt LED.
(µmoles are new units to me. I think I got through the lumens-lux-µmoles calculation correctly, but maybe not.)
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.
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.
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)
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!
I actually have a grow shop around the corner from where I live who have chili peppers in their display grow boxes (because they can't grow marijuana there for legal reasons), and they use MH lamps still; if there would be a cheaper way to grow, they'd switch in a heartbeat, because indoor growing is about squeezing every last drop of efficiency from your setup (although it's been a while since I've been there to be honest, and I did see them advertise a LED grow light a few weeks ago, but still not at prices much lower than GP).
But on a more broad note: Indoor farming has real potential, in particular for certain types of crops. Not only do indoor farms use less water (which takes energy to produce and transport), but requires less or no pesticides, can be grown out of season, and you're less subject of good/bad weather patterns.
I don't think we'll see this type of thing for inexpensive crops that use up a lot of land (e.g. corn) but we might be more expensive crops that are fairly land efficient (e.g. nuts, fruits, etc).
http://www.adn.com/article/20150315/vertical-farm-poised-ris...
I'd be curious to see comparison with PAR spectrum and plant grow results against similar wattage multi-color LED.
Or a 1200w for $369: http://www.amazon.com/KingTM-Spectrum-360-860nm-10bands-Flow...
I actually have free electricity at my office, otherwise I'd run the numbers to see the cost savings. 5x longer lifespan ... I'd want an independent review.
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.
with the legalization of marijuana already happening in some states and pending in many others, the lighting industry is full of fluff right now and too many players... will be interesting to see who stands, who falls and who M&A. I think many growers will stick to HIDs until someone can prove LEDs, Plasma or induction not only delivery the same quality product, but can actually do it cycle after cycle, these 50k hour guarantees are suspicious at best.
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?
Also curious if they're using a film (like WhiteOptics White97) or having the cavities coated (I forget the product name). None of the coatings were cheap when I was researching them, but a % or two better than the films.
I'd love see the LED driver board on these...
But anyhow:
It's incredibly cool stuff, especially when you show someone the raw blue leds (blindingly bright), then drop a remote phosphor over it.
Kudos for going for it, and good luck. I wish I had your fortitude!
For the recycling cavity we do indeed use WhiteOptics. We used Furakawa in our last design and have had success with both.