5 ms·

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 yo

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.

chongli 4y ago
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.
- imtringued 4y ago
  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.
  - chongli 4y ago
    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.
farmaway 4y ago
On spectrum optimization: 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 plants can use for photosynthesis? Quick Googling suggests "maybe, probably not", but it's been years since I took an EM physics course. I realize PV panels are less than 100% efficient at solar to electric energy conversion. Wikipedia suggests 30% is a realistic figure for large-scale solar installations. Batteries also add losses, so let's assume LEDs only run while the sun shines. LEDs themselves add losses too, so our inefficiencies seem to be piling up... All the same, I'd love to see someone run the experiment of (yield per care of traditional farming) / (yield per acre of solar panels + vertical hydroponics).
- imtringued 4y ago
  If that were possible then all these vertical farms deserve to fail because they didn't take such a basic strategy into account.
  - deleted 4y ago
    [deleted]
- zeristor 4y ago
  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.
  - LargoLasskhyfv 4y ago
    > 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 https://en.wikipedia.org/wiki/Single-cell_protein Imagine the potential... ;->
aaron695 4y ago
[dead]
jnsaff2 4y ago
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
LargoLasskhyfv 4y ago
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?

chongli 4y ago

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.

imtringued 4y ago
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.
- chongli 4y ago
  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.

farmaway 4y ago

On spectrum optimization: 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 plants can use for photosynthesis? Quick Googling suggests "maybe, probably not", but it's been years since I took an EM physics course. I realize PV panels are less than 100% efficient at solar to electric energy conversion. Wikipedia suggests 30% is a realistic figure for large-scale solar installations. Batteries also add losses, so let's assume LEDs only run while the sun shines. LEDs themselves add losses too, so our inefficiencies seem to be piling up... All the same, I'd love to see someone run the experiment of (yield per care of traditional farming) / (yield per acre of solar panels + vertical hydroponics).

imtringued 4y ago
If that were possible then all these vertical farms deserve to fail because they didn't take such a basic strategy into account.
- deleted 4y ago
  [deleted]
zeristor 4y ago
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.
- LargoLasskhyfv 4y ago
  > 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 https://en.wikipedia.org/wiki/Single-cell_protein Imagine the potential... ;->

aaron695 4y ago

[dead]

jnsaff2 4y ago

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

LargoLasskhyfv 4y ago

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?