LEDs For Vertical Farming: Buying Guide For Lights
LEDs For Vertical Farming: Buying Guide For Lights
Posted on June 13, 2017
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Big Changes in Vertical Farming!
It’s easier than you think to pick the right lights for your vertical farm.
Trying to figure out the right LED lights to buy can be an overwhelming experience. There are more specs, stats, and engineering minutiae packed into product pages for LED lights than anyone running a business should have to parse through.
This article is for people who want to start their own indoor vertical farm and it’s going to drill down on the important characteristics of the lights for a business. In other words, this isn’t an exposition on the science or engineering of LEDs – despite what LED manufacturers would have you believe, you don’t need to geek out to get this right and you don’t need “cutting-edge technology.” In fact, what I want to do is try and cut through all the science and marketing-speak and put this in terms of the factors that will influence a practical business decision.
For perspective, the conclusions drawn from this piece are from a very small farm and are probably only applicable to farms costing less than $1 million (and maybe not even all of those). Once you go beyond that, some of the business decisions change. I recognize this.
I’d also note, that for our business, we’ve always had more success with going out and getting things done than staying home and planning/optimizing. These conclusions also reflect that. But hey, we’ve been making money selling our produce while people that started at the same time as us are still at home fiddling with their systems.
Before we get started, this article gives a good overview about what makes LEDs great, but my understanding of commercial lighting has increased exponentially since it was first written.
If you would like to get into the science behind this, I’d recommend the book LED Lighting For Urban Agriculture by Toyoki Kozai.
Our Test
GE, Philips, and Total Grow lights are all used in commercial farms and all come highly recommended. By using these lights, we knew they were vetted for quality and the reputation of the brands meant that we wouldn’t have to worry if their spec sheets were accurate.
For background – when selecting these lights, our plan was to originally grow a range of plants including microgreens, lettuces, and herbs and we got the same lights (***this is not what you would do if you knew what you were buying for – we were at a different stage in our business model when we made that choice***) for all of them. With these plants in mind, we knew that for everything but the neediest herbs, we wouldn’t need to go over 400 μmol/sec/m2 (this is a measure of photosynthetic photon flux per unit area, often abbreviated as PPF and is the most important metric for determining the quality of lights) and that staying lower would be better for the micros and more efficient for the lettuce.
We did 2 test runs of different loose leaf lettuce blends, started from seed under the Philips lights before finishing them off under the different brands. We controlled for light height, light amount (daily light integral)*, humidity, temperature, duration, and feeding times.
To start, here are the lighting profiles for our layout provided by the vendors.
Philips
GE
Total Grow
*While the DLI’s were slightly different, we took this difference into account when evaluating the overall values of the lights across different factors.
Yield
For us, this was the most important factor. We wanted to know if any of these lights lead to more (or better looking) food.
After harvest, we weighed our lettuce from each of the three systems and found… that the Total Grows had a small edge. The microgreens under the Total Grows looked a lot better too but we didn’t measure that accurately. As part of this, we’d also included some cheapo LEDs that were only 6000k in the experiment, though not with as many controls in place. While all three name brand lights looked better than the yields from these lights, it wasn’t by much.
Cost
This was our second most important consideration for obvious reasons. Here are the list prices for the lights we looked at (and as with anything, when you go commercial, there’s some wiggle room):
Philips: $121+/light, $726/shelf. These are the Gen 2 lights and they can be had for slightly less than this number, but you also have to buy female connectors and wiring. The price noted here reflects that.
GE: $349/light, $698/shelf. This includes clips for hanging them, jumper cables, and the pre-wired plug. And remember, these are 8 feet long.
Total Grow: $32/light, $1050/shelf. In addition to the lights, you are also paying for the socketed cord the lights plug into and you can get hanging infrastructure that I did not include the cost of here because I didn’t end up needing it.
And of course, expect to add at least another $50-$100 for shipping each product depending on how many of these you get.
Warranty And Expected Lifetime Hours
The warranty is the more important thing here in my opinion because it is what the company is actually willing to put money behind, but each are important.
Philips: 3 year warranty. 25,000 hours at 100% efficiency that gradually drops after this point (this might be true of the other lights tested, but only Philips mentioned it).
GE: 5 year warranty. 36,000 hours.
Total Grow: 5 year warranty. 50,000 hour service life.
Energy Efficiency
This turned out to be an incredibly important factor in my decision. My farm is built inside of a refurbished garage and is limited to the breaker that was already installed: 15 amps. That means I had to be able to run the whole farm on around 11 amps (both because wattage fluctuates and because I run a space heater when the exhaust fan kicks on below certain temperatures). So, the lower the amperage draw, calculated by dividing watts by volts, the greater the area I could light at a given level
The below measurements are in joules/second which is a good approximation for watts. It also applies to 1 light for each of these brands, not what is needed to light our whole shelf.
Philips: 2.17 µmole/J (x6 lights needed for our grow space)
GE: 2.33 µmole/J (x2 lights needed for our grow space)
TotalGrow: 1.3 µmole/J (and remember, we need at least 30 of these for the grow space). Another thing to note with these lights is that the housing heated up noticeably more than the other brands.
However, all of these lights were so efficient that it didn’t actually end up mattering for my space. That calculus changes the more lights you have.
Ease of Use
This ended up mattering probably a little more than it should for us compared to a mature venture. The reason for this is because we knew we were going to be moving stuff around, just kind of playing and making frequent adjustments. No one wanted to waste time fiddling with everything and more flexibility means more testing and iterating is easier down the road.
Philips: You have to wire these things yourself, which takes less than 10 minutes/light but has a learning curve that’s steeper than I would have liked requires some basic tools and a soldering iron. You could do it without the solderer, but I feel much more confident in the wiring with it. One thing to take into account when buying plugs, try and get ones that will all fit on your power strip. We didn’t think that far ahead and have some wasted outlets as a result.
We hung these with s hooks from the frame. I only feel ok about how secure they are. When we re-do the space, these will get directly mounted onto the shelves and will eliminate this problem.
GE: Super easy. Just unpack and plug in. We used s hooks into the mounting clips for these as well. That’s definitely not how they were intended to be used but we wanted to be able to move everything around and that would have been too hard if we screwed or nailed these things into our shelves (which even being able to do is another benefit of building your own shelving).
Total Grow: So you have to unbox a lot more lights which added a negligible amount of time but was still a bit of a pain. And if we were covering 10k square feet instead of 130, it might be an actual factor in terms of costing a few hours of pay to do. And once that was done, we had a rather unwieldy socketed cord to maneuver into place. This would have been much easier if we would have used their custom built mounting option (that they suggested and was well worth the price, we just switched our grow site dimensions too far along in the process) so that’s no fault of their design. Overall, not as easy as the GE lights, but definitely easier than the Philips ones.
Feeling/Durability
Philips: These have nice metal frames and thick plastic protecting the diodes and overall feel very good although one of mine buzzes loudly. I don’t know if that’s because of mishandling from previous projects, bad wiring (it was purchased and used before the others), or a fault in manufacturing.
GE: These are made of a thick plastic and overall feel a lot less durable than the Philips or Total Grow lights. I wouldn’t quite say they were fragile though. Also, being 8 ft long, they have a slight bow when not properly supported.
Total Grow: Wow. These blew me away with how solidly they were put together. In terms of durability from dropping or water, I have the most confidence in these lights by a significant amount.
Company
Philips/GE: I ended up ordering both of these through Hort Americas. Hort Americas has great customer service and worked with me to get detailed product information and talk me through the right products for my farm. They had helpful alternative suggestions and cost saving ideas.
TotalGrow: TotalGrow (Venntis Technologies) gave me some of the best customer support that I’ve ever received in my life. They will work with any farm to customize their spectrum and setup for the space and help you with your design process.
Conclusion: I would definitely encourage either ordering from Hort Americas or TotalGrow as opposed to some other web site.
Overall
To keep this from wandering too much more, I ended up choosing the GE lights for cost and energy use reasons. The fact that they were easy to install was icing on the cake.
The results of the yield test lead me to another conclusion. Pretty much any home grower or someone looking to just get a system going and tinker with it will be set with shop lights of the right spectrum. Small commercial growers should probably get a dedicated horticultural bulb, but probably don’t need to worry too much about getting the latest and greatest, because really, despite the hype, it didn’t end up making a huge difference.
I also know that the company that manufactures the TotalGrow lights has improved both the cost, energy use (by 10%), and output (10-25%) of their product so I expect them to be a much better option once their new generation of lights is out.
However… if you were to drastically increase the scale of your facility beyond what we did at Rosemont, the calculus changes. The minor yield differences suddenly start equalling thousands of dollars/year. Same for the increased electrical cost.
Still, even at that scale, I think you would be fine with any of the lights mentioned. Probably the most important factor would be the best bulk buy price you could negotiate with your distributor.
Helpful links:
https://fluence.science/science/how-to-compare-grow-lights/
http://hortamericas.com/catalog/horticultural-lighting/arize-lynk-ge-led-grow-lights/
Buy Philips GreenPower LED Grow Lights
http://totalgrowlight.com/products/broad_grow_bulb.html