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Why vertical farms are a crock.

monbiot.com

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Re: Why vertical farms are a crock.

#71

Post by tocomment »

dalke wrote: post #48
kyteland wrote: post #44

Earlier quoted context omitted.

I don't buy his argument that the cost of artificial lighting alone would be ~100x the current market value of the produce, especially when you use the solar collector analogy for farmland. Some quick googleing puts wheat in the 1% efficient range or less when converting light into carbohyrates. I have no idea where to find the exact number but it's not efficient at all. In a controlled environment the remaining 99%…

"In a controlled environment the remaining 99% of the energy could be recycled." Thus violating the second law of thermodynamics. Do tell how we can recycle that energy, turning waste heat back into light, since that would also make solar cells more efficient, increase farming capabilities in cloudy/cold regions, and reduce our dependency on petroleum by making biofuels easier to grow. For a starting point of the cal…

Put mirrors on the walls and ceiling and put reflective particles over the soil. That should let more light eventually end up on the plants.

Re: Why vertical farms are a crock.

#72

Post by 1053r »

ars wrote: post #30
1053r wrote: post #9

Earlier quoted context omitted.

Production prices for solar energy are now below $0.80 / watt ( http://www.123jump.com/market-update/First-Solar,-Inc-Q4-Ear... ), although skyrocketing demand has caused wholesale prices to remain much higher. It seems likely that we may in the next 10 years be in a place where we can turn sunlight into electricity, and then electricity into the exact wavelengths of light used in photosynthesis more efficiently than…

How in the world did you get +8 mod on this? That's utter nonsense! You can only get as much light as you have surface area - so now instead of fields of crops, you have fields of solar collectors! Did you think there was some magical light multiplier device that could give you more output light than you started with? Plants already use the best parts of the visible spectrum to collect light. The small amounts of inf…

A solar cell collects energy over a range of frequencies, while a plant (if I recall) uses only two. You can think of it this way. Wheat is say 1% efficient at solar collection, while even crappy solar cells are like 8%.

Of course you need to transmit electricity and re-emit the light efficiently. You will still end up with acres of solar panels, as I said. Before you jump on someone for getting their science wrong, make sure YOURS IS RIGHT!

Re: Why vertical farms are a crock.

#73

Post by Vivtek »

rsheridan6 wrote: post #67
ars wrote: post #30

Earlier quoted context omitted.

How in the world did you get +8 mod on this? That's utter nonsense! You can only get as much light as you have surface area - so now instead of fields of crops, you have fields of solar collectors! Did you think there was some magical light multiplier device that could give you more output light than you started with? Plants already use the best parts of the visible spectrum to collect light. The small amounts of inf…

You might be able to beat crops in that way if you dispensed with photosynthesis and crops altogether and came up with a completely different way to convert solar energy to carbohydrates. Somebody else in this thread said that a wheat field converts 1% of its solar energy to food calories. They didn't cite that and I don't have time to look it up, but if it's true it should be beatable.

Assuming three billion years of evolution is beatable is generally a fool's game. I do like the idea of chlorophyll-tuned lasers, though.

Re: Why vertical farms are a crock.

#74

Post by Vivtek »

chadmalik wrote: post #57
sshumaker wrote: post #55

Earlier quoted context omitted.

Because your comments about local food are clearly written without a basic understanding of the breakdown of energy use. Freight shipping uses about 1 gallon of gas/ton/500 miles. Over 80% of the costs are in the final few miles - trucking from the shipping depot to the markets. Getting food locally delivered is far less energy efficient than having it shipped in bulk by freight to supermarkets.

No, it is because the moderation policies on this site are absurd and comments saying "it sucks" get modded up while a reasonable comment gets modded down. Bottom line the world is running out of hydrocarbons. Things that look "energy efficient" to you today won't look so efficient in 50 or so years. Peak oil already happened in the United States, Hubert's peak is reasonably well accepted, and the idea that shipping…

Huh. You don't normally see a classic flounce like this around here.

Re: Why vertical farms are a crock.

#75

Post by dalke »

tocomment wrote: post #71
dalke wrote: post #48

Earlier quoted context omitted.

"In a controlled environment the remaining 99% of the energy could be recycled." Thus violating the second law of thermodynamics. Do tell how we can recycle that energy, turning waste heat back into light, since that would also make solar cells more efficient, increase farming capabilities in cloudy/cold regions, and reduce our dependency on petroleum by making biofuels easier to grow. For a starting point of the cal…

Put mirrors on the walls and ceiling and put reflective particles over the soil. That should let more light eventually end up on the plants.

You'll need mirrors which don't block the light. One-way mirrors are only half-silvered, which means they'll block more light than they'll recover. What you'll have to do is figure on something on the other side of the plants than the light source.

Take a look at the link to "Photosynthetic efficiency". Only about 13% of the light ("incomplete absorption") could be reused this way. Most of the rest of the energy is turned into heat.

Now, it is possible to be more efficient through layers. Take a jungle, where most of the energy is absorbed by the top level while lower-level plants make use of what energy comes through, eg, more efficient in dim light or better use of other parts of the spectrum.

You will be able to get some more efficiency by doing this, but it's going to be expensive, and nothing like "99%".

Re: Why vertical farms are a crock.

#76

Post by dalke »

1053r wrote: post #72
ars wrote: post #30

Earlier quoted context omitted.

How in the world did you get +8 mod on this? That's utter nonsense! You can only get as much light as you have surface area - so now instead of fields of crops, you have fields of solar collectors! Did you think there was some magical light multiplier device that could give you more output light than you started with? Plants already use the best parts of the visible spectrum to collect light. The small amounts of inf…

A solar cell collects energy over a range of frequencies, while a plant (if I recall) uses only two. You can think of it this way. Wheat is say 1% efficient at solar collection, while even crappy solar cells are like 8%. Of course you need to transmit electricity and re-emit the light efficiently. You will still end up with acres of solar panels, as I said. Before you jump on someone for getting their science wrong,…

"a plant (if I recall) uses only two [frequencies]"

You mis-recall. It has two peaks in the absorption spectra but they are not narrow. In other words, a plant is green. There's no way to absorb only two frequencies and still be green.

"Wheat is say 1% efficient at solar collection"

Using http://en.wikipedia.org/wiki/Photosynthetic_efficiency as a guide, about 28% of sunlight energy is collected by chlorophyl. Of that, much is used to keep the plant alive (sugar production, respiration, growing roots). About 1% is left for human use.

It's the 28% that's relevant here, not the 1%.

In other words, 28% for plants beats "crappy solar cells" at 8%. Now, 47% of the energy is outside the 400-700nm range that chlorophyll can process so you might be able to double the energy use if you can find a good way to upconvert/downconvert light into that range. That would at best double what you can grow.

Which is still nowhere close to getting viable farming in an urban center.

Re: Why vertical farms are a crock.

#77

Post by brudgers »

jdietrich wrote: post #26

Farmland isn't just a place to put some plants while they grow. A farm is a giant solar power facility, one that converts solar energy, carbon dioxide and water into carbohydrate. Monbiot doesn't stress the point enough - it's all about light. When we say that we have a shortage of farmland, what we mean in practical terms is that we have a shortage of flat areas with good drainage to function as solar collectors. Go…

Hogs and chickens don't run on sunshine.

They stack pretty well.

And in urban areas the pipes are already in place.

Agriculture is messier than we all like to pretend.

Re: Why vertical farms are a crock.

#78

Post by Jsw32 »

It seems that many people here are making conjecture based upon little research. Vertical farms are very much possible and actually relatively efficient . The EPA has been funding small scale pilot farms to test the concept. The engineering hurdles which people are describing have mostly been dealt with. Food from these farms may cost more but it is fresh, local and organic instead of ethelyne ripened and full of pesticides. Take a walk to whole foods and you'll see that people are willing to pay for that.

Re: Why vertical farms are a crock.

#79

Post by phunel »

hugh3 wrote: post #22
alabut wrote: post #8

Earlier quoted context omitted.

" You would need > 100 of these buildings (ignoring all the other issues for now) to be able to replace one major farm. " So what if it didn't replace one major farm and just a small local one? And what if the vertical farm and office building idea were combined, so that you had alternating floors of greenhouses for plants and office workers that ate them? I'm surprised I haven't seen the ideas brought together befor…

And what if the vertical farm and office building idea were combined, so that you had alternating floors of greenhouses for plants and office workers that ate them? It takes 1-2 acres of farmland to support one person's eating requirements, which is two floors of the Empire State Building. Alternatively, there's 21000 people working in the ESB so that's about 200 people per floor. If you devoted every second floor to…

Pretty sure the 1-2 acre number is quite relative to diet. Perhaps for heavy cattle grazing, bush meat, etc. but not for a vegetable based diet. For an alternative reference see: http://books.google.com/books?id=hwAHmktpk5IC&pg=PA819&#...

Re: Why vertical farms are a crock.

#80

Post by rsheridan6 »

Vivtek wrote: post #73
rsheridan6 wrote: post #67

Earlier quoted context omitted.

You might be able to beat crops in that way if you dispensed with photosynthesis and crops altogether and came up with a completely different way to convert solar energy to carbohydrates. Somebody else in this thread said that a wheat field converts 1% of its solar energy to food calories. They didn't cite that and I don't have time to look it up, but if it's true it should be beatable.

Assuming three billion years of evolution is beatable is generally a fool's game. I do like the idea of chlorophyll-tuned lasers, though.

Evolution can be stuck in local maxima determined by some path it went down a long time ago. If life happened to evolve an inherently inefficient metabolism, it would be stuck with it forever because you can't really go back on something that fundamental (we share glycolysis mechanism with bacteria).

And, even if evolution automatically did win, plants did not evolve to feed us. They evolved to reproduce themselves, and we have incidentally hijacked them to use as food sources.

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