Can you actually explain what makes LEDs so special?

Why is this so critical to vertical farming?

Before diving into the basics of LED lighting, let’s touch on why vertical farms require such a massive amount of light.  Though a simple problem to understand, there is no universal lighting solution to efficiently illuminate multi-level farms because higher levels shade lower ones.  Essentially, any move to intensify the number of seedlings per square foot, a primary function of vertical farming, is going to increase the shade over seedlings already in place as in the image from VertiCrop below.


As a result, prominent critics cite lighting as the main limiting factor any successful vertical farm would have to overcome.  One such critic is Dr. Ted Caplow.

I first ran into Caplow’s work after learning about the Science Barge experiment he was running in New York.  Caplow and his team were trying to figure out exactly what it would take to reach efficient, sustainable production in the middle of a city.  The barge was a success, but it hinted at failure for vertical farming.


Based on his experience, Caplow came up with a rough estimate for calculating lighting requirements for hydroponic growing facilities fueled by solar panels (like vertical farms).  Basically, he estimates that to light a single layer of plants using energy exclusively from solar panels requires an area 20x larger than the square footage of that layer.

With improvements in LEDs and solar panels, Caplow’s estimates may soon be wrong if they aren’t  already.

But first thing’s first: what are LEDs and what exactly is efficiency?

11 thoughts on “Can you actually explain what makes LEDs so special?

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  8. There is no doubt that LEDs are the future, but are they the present?

    No. Not at all.

    You will save yourself around 20 watts for the same square foot coverage. Sounds great, doesn’t it? Unfortunately it will take 50 hours to reach a single kWh (that is at 12 hours a day, which is quite common for leafy greens).

    Here comes the tricky part: How much are you paying for your kWh? The higher the cost of your electricity, the more sense it will make to get LEDs, but let’s say the standard price in the US is 10 cents (In Spain I get them for 0.06€).

    Every 4 days you will save yourself 10 cents in electricity. Every 40 days you’ll save yourself an entire dollar.

    How much does a 4-foot fluorescent tube cost? Around 1 dollar getting them in bulk from the manufacturer (which all vertical farms should obviously do). The cheapest 4-foot LEDs you can find will be 100 bucks.

    How long will it take to get that initial cost back due to your energy savings? Those extra 99 dollars, saving 1 dollar every 40 days means … 99 times 40 days … 3,960, over 10 years.

    Yes, you’ll also have to get reflectors for your fluorescents – 99.85% reflective anodized aluminum cost less than 4 euros each, and will last decades providing proper maintenance. Those 4 euros won’t be a problem either.

    As for HVAC costs: LEDs and fluorescent tubes aren’t any different in heat (BTU) production. The reason LEDs are usually said to “emit less heat” is simply because less watts run through them. Of course 35 watts will emit less heat than 54w, but again, looking at how much it will cost to cool your growing area (each watt will mean 3.41 BTU of heat) it would take many, many years to get back the money you invested in your LEDs. The exact numbers are difficult to get, since it depends on your climate and the temperature you want your grow room to be at, but summing up, saving yourself 68 BTU per 4-foot luminaire isn’t going to offset those extra 99 bucks you paid for your LED (and that’s going with the cheapest available)

    Sorry for the rant but the numbers still don’t work out. Let’s talk again in 2020, when I’m sure LEDs will be cheap enough to finally kick fluorescents out of vertical farms forever.

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