Vertical Farming Has Found Its Fatal Flaw

Re:Vertical Farming Has Found Its Fatal Flaw by ThePhysicist on Friday December 30, 2022 @03:02AM (#34182977)

I think the sun provides around 5.000-10.000 lux (lm/m²) illuminance in temperate climates on an average day. Modern LEDs produce around 200 lm/W, so I think you need around 10-15 W/m² to grow stuff inside that would normally grow outside, e.g. corn (of course you can optimize the spectrum to save some energy, I'll disregard that here for the sake of simplicity). That's around 0.25 kWh/m²/day of vertical farm, or 7.5 kWh/m²/month. So, for one hectare of food you'd need 75.000 kWh/month of electricity, only for the lighting. Given these numbers I don't know how vertical farming could replace outdoor farming for most staple crops. Maybe if a miracle in energy production occurs, but even then many other challenges remain.

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Re:Vertical Farming Has Found Its Fatal Flaw by chongli on Friday December 30, 2022 @03:39AM (#34183164)

Solar energy is only one factor in the equation. Another one is water. Indoor farming lets you get your energy and water from different places. This is potentially a breakthrough because of the relative difficulty of moving large quantities of water around (not to mention food destined for market) compared to electricity.

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Re:Vertical Farming Has Found Its Fatal Flaw by imtringued on Friday December 30, 2022 @04:43AM (#34183526)

But in this scenario you just want a greenhouse that recirculates water but you still don't want to stack your plants to take advantage of natural light.

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Re:Vertical Farming Has Found Its Fatal Flaw by chongli on Friday December 30, 2022 @07:55AM (#34184565)

Whenever you harvest the fruits and veggies you take water out of the system. You also lose water due to evaporation and people coming/going from the greenhouse. So while you may be a lot more water efficient in a greenhouse you're still a consumer of water.

Furthermore, I am thinking of places like Canada (where I live) that get very little sunlight in the winter, despite having incredible abundance of fresh water. We could grow a lot of vegetables in the winter and power the artificial lighting using wind, hydroelectricity, or nuclear. This would allow us to avoid importing so many vegetables from California or Mexico.

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Re:Vertical Farming Has Found Its Fatal Flaw by farmaway on Friday December 30, 2022 @04:08AM (#34183321)

How much of the Sun's emissions spectrum is actually used by plants for photosynthesis? Are there efficiency gains to be realized by converting non-"bioavailable" solar radiation first into electric power, and then into LED output that plants can use for photosynthesis? Some quick Googling suggests "yes", , but it's been years since I took an EM physics course.

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Re:Vertical Farming Has Found Its Fatal Flaw by imtringued on Friday December 30, 2022 @04:46AM (#34183537)

If that were possible then all these vertical farms deserve to fail because they didn't take such a basic strategy into account.

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Re:Vertical Farming Has Found Its Fatal Flaw by farmaway on Friday December 30, 2022 @05:20AM (#34183708)

I'm not sure I understand what you mean. What I'm driving at is the ratio of m² used to grow plants the old fashioned way / m² used for solar panels + vertical hydroponics to grow an equivalent yield. It's unclear to me what this ratio is with current photovoltaic (PV) and LED efficiencies. Vertical farm owners may not know or care unless they're also involved in power generation.

Photosynthesis only uses a subset of the visible spectrum. PV panels make power using a different (larger? certainly non-identical) subset of the visible spectrum, albeit at a maximum of maybe 30% efficiency in practice. At first glance, if solar panels convert enough unused parts of the spectrum into LED output that can drive photosynthesis, there might be a net gain on crop yield per m² versus traditional farming. I'm sure someone's run this experiment by now. If so, I'd be curious to see the results.

Incidentally, PV panels discard IR light which makes up 55% of all received solar energy. Concentrated solar power systems seem theoretically more efficient per m² since they capture all light as heat, but I imagine maintenance, energy storage, and heat engine/dynamo inefficiencies combine to bring their total efficiency down.

In short, back of the napkin calculations for this stuff are harder than they may seem! I'd love to see the results of some real-world experiments.

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Re:Vertical Farming Has Found Its Fatal Flaw by zeristor on Friday December 30, 2022 @06:15AM (#34184018)

Red and blue mostly I think, hence purple lights, and why plants look green and not black.

As I understand the variation in green light and it’s intensity mucks up photosynthesis, now if photosynthesis could be tuned to use green light too that would be handy, it’s just that evolution has a head start of billions of years.

Of course though eukaryotic cells run on mitochondria, if energy could be sourced to the cell to replace the chloroplasts directly that could be one way around. But denaturing food like that could have unforeseen consequences.

There was a Tommorow’s World item about making food from petrochemicals, I’m still aghast.

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Re:Vertical Farming Has Found Its Fatal Flaw by LargoLasskhyfv on Friday December 30, 2022 @08:42PM (#34192501)

> There was a Tommorow’s World item about making food from petrochemicals, I’m still aghast.

You make that sound so bad.

https://en.wikipedia.org/wiki/Single-cell_protein

Imagine the potential... ;->

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Re:Vertical Farming Has Found Its Fatal Flaw by PeterisP on Friday December 30, 2022 @06:21AM (#34184043)

You can save some energy by choosing specific spectrum LEDs but you can't go overboard as that is tricky, since in addition to photosynthesis a bunch of other processes in plants are activated by light, and if you just put in one frequency then you may get weird results as some processes in the plant "think" that it's nighttime and screw up its growth.

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Re:Vertical Farming Has Found Its Fatal Flaw by voakbasda on Friday December 30, 2022 @11:29AM (#34186555)

I can think of one plant that will never flower under fluorescent bulbs, because they lack enough red wavelengths to trigger the hormones that shift its biochemistry from vegetative to reproductive growth.

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Re:Vertical Farming Has Found Its Fatal Flaw by jnsaff2 on Friday December 30, 2022 @09:51AM (#34185531)

So you are saying that of the ~1kW of energy that ends up on a m2 from sun only 10-15W is light that is useful for plants? And that is after the power conversion losses?

So my solar panel that gets ~200W/m2 could feed 10x the area of plants than the sun directly?

Something does not add up here.

Edit: 10k/200 is 50 so I don’t see how you ended up with 10-15

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Re:Vertical Farming Has Found Its Fatal Flaw by LargoLasskhyfv on Friday December 30, 2022 @07:48PM (#34191987)

There is another thing that comes to mind. Wind. Many plants grow thin and weak without it. One can maybe compensate that with blowers, but that's just more energy needed. Or shaking them somehow. I don't know exactly how relevant that would be for small stuff growing fast to be consumed ASAP, but maybe the lack of it could also influence taste/texture?

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