This is a big issue and I've been unable to get good data on it. Opponents of vertical farms say that the high electrical consumption doesn't justify the reduction in energy related to travel. Proponents say that it's possible to optimize LEDs and have continuous fake "seasons" which justify the cost of transportation & refrigeration for certain species of food.
Does anyone have any good references that go into the details and provides numbers? Most of the pro-vertical farming information I've found is from companies who are investing in it so they consider the energy numbers to be a trade secret. But there must be some research group or open source team willing to publish all their data so that people can draw their own independent conclusions.
We will be publishing some data from our pilot installation next year (approx 250 m2 building, 100 m2 active growing area, 30 m3 water). It isn’t a vertical installation, but a Deep Water Culture (DWC) aquaponics installation. We are in the final stages of building it right now. Spent all day working on the decking around the fish tanks.
(Edited to correct the calculated values.)
Plus, I am no expert but I guess you can't make plants actually use much more than 100W/m2 for photosynthesis, the rest of sunlight consists of unsuitable wavelengths. It ends up as waste heat that you'd have to cool away. Perhaps if you could efficiently convert green and infrared parts of sunlight to red/blue, that could help.
Plants are pretty inefficient, it's true, but I don't think they're very efficient even with optimal wavelengths. But, yes, solar cells and LEDs can indeed convert green and infrared sunlight to red and blue, with about 3% efficiency under normal circumstances.
The big question for me is, if you're going to build a hothouse, why would you build it with an opaque roof? That just seems perverse, like writing an HTTP server in bash or assembly language or something: http://canonical.org/~kragen/sw/dev3/server.s
Also you haven't said anything about cooling, which the translucent roof inevitably requires in summer.
Cooling, though, is an issue whether your light comes from LEDs or the sun—either way it comes with a lot of extra heat. With the LEDs I'm familiar with, this is a worse problem than with sunlight, but in another thread https://news.ycombinator.com/item?id=20908476 I see a report that there are now illumination LEDs that reach an astounding 40–50% efficiency level. If that's true, it would make the LED cooling problem a little smaller than the sunlight cooling problem, instead of much bigger; and of course spectral matching helps.
Alternatively, every time when it’s not sunny... meaning all night every night. Of course, that would require experimenting if it’s actually more efficient, but AFAIK that’s what a MIT experiment found regarding growing basil (though they were optimising for flavour, not energy efficiency).
They have some data http://plantalux.pl/en/plantalux-ex300w-en/
He experiments with led and has detailed information on LED and plants.
He has a patent for growing smaller plants, by lighting with blue light on the stem.
Once basic caloric needs are met, a variety of vegetables become crucial in a healthy diet. American diets are terrible for this. It’s often cheaper or easier to buy highly processed foods based on corn, wheat, and soy than vegetables in the US .
What’s needed in the US and many modern countries is precisely what vertical farms are good at growing, fresh leafy greens, peppers, herbs, green beans, etc. Shipping fresh vegetables degrades the available nutrients in these items (up to 30% in three days [2). Even then that crunchy water like lettuce plays a crucial role in keeping gut biotica healthy and balanced.
Sure vertical farms won’t replace staple crops anytime soon or ever, but there’s an enormous need (in the US at least) for more fresh vegetables. Crunchy water also tastes pretty good if you know how to cook it.
What you are looking for is research from luuk graamans.
He has made some slight errors on the light intensity needed but still.
In any case vertical farming now is not there yet in Europe and the US but it will get there.
We also did some research on photovoltaic use with some good results :/
The “food miles” thing is insignificant nonsense; see notes/strawberry-miles.html in http://canonical.org/~kragen/dercuano-20190831.tar.gz.
I'm dubious about the economics of the thing.
Let’s assume that the power source is solar. The 84% energy loss of solar panels, followed by the 80% energy loss of LED lighting, works out to about 3% of the sunlight harvested getting to the plants. That's a high price to pay for wavelength-shifting and time-shifting; it's hard to see when this would be a better solution than skylights, lightpipes, and colored filters, maybe supplemented by LEDs or low-pressure sodium at night. (Except, I suppose, to avoid violent reprisals for cultivation somebody doesn't like.)
If the power source is fossil fuels or nuclear energy, it makes even less economic sense, except at extreme latitudes like those of northern Scotland or Norway, because those energy sources are even more expensive.
In moderate latitudes with adequate civil rights, it would seem that the only reason for indoor cultivation with only or primarily artificial light would be an aesthetic taste for the artificial, like tailfins on 1950s cars or the bright blue LEDs on current shitty consumer electronics.
You're also not tied to variations in weather, meaning more consistent yields and substantially smaller likelihood of crop failure. And you're saving labor of tilling/planting, as well as the significant equipment/fuel costs and associated outages that go with outdoor farming.
There might also be automation benefits, easier to design an assembly line around your indoor grow setup with consistent lighting conditions for visual processing, but I'm not sure about this one.
Regarding solar, even if your percentages were correct (and I'm pretty sure they are not); the point of sun light is that it has a very attractive cost of exactly 0$. It costs absolutely nothing. So it doesn't matter that solar panels are not very efficient. They actually are getting better and certainly 16% efficiency is nowhere near the best there is. However, the only thing that matters is the cost of these panels and the amount of space they take up. Which is why places like Scotland and Norway still find uses for solar panels even though conditions are obviously less than ideal for operating them. As mentioned, both have alternate sources of clean energy that are cheap and plentiful (i.e. wind and hydro). And if you look at Iceland, it uses geothermal to power it's greenhouses.
The whole point of LEDs is that they are supposedly very efficient; around 40-50%. Also heat is not actually energy loss in a vertical farm. Temperatures in Scotland are below ideal temperatures for growing things. Meaning most of the energy use in a vertical farm is probably used for temperature control (mostly heating and occasionally cooling).
Luckily, you can produce both heat and light using energy. Meaning that the reason vertical farming is getting a lot of attention is that the cost of energy has been dropping by rather a lot and is projected to continue to drop. Effectively this dominates variable cost in a vertical farm. The economics of growing vegetables in a vertical farm is a simple function of kilos of produce / kwh.
You seem to be arguing this cost is too high. That seems to be countered by the many people actually growing stuff in greenhouses for decades this and making plenty of money. E.g. the Netherlands is the largest exporter of tomatoes world wide. This is a billion dollar industry. These tomatoes are grown in green houses. Those used to be powered using cheap natural gas and in recent years are being powered by cheap wind energy. Square meters are expensive in the Netherlands and most of those tomatoes are grown in an area that has very high population density. I'd say vertical farms consume similar amounts of energy (or less) but have a much higher space efficiency.
For most purposes I agree with you! However, in this case, the alternatives I am considering are:
1. Build a 10000 m² greenhouse full of, say, lettuce, perhaps on multiple shelves ("vertical farming").
2. Build a 10000 m² solar park full of solar cells, then use the energy produced by the solar cells to illuminate lettuce being grown inside an opaque concrete box, of some arbitrarily variable size.
In this comparison, the efficiency of solar cells and of LEDs matters very much indeed! Because of their inefficiency, you get 30 times as much lettuce in case #1. That's the reason I think this scheme is uneconomic except in unusual cases. In another part of the comment thread, I agreed that abundant wind energy is a case where it might make sense.
It's true that there are solar cells in commercial production that are 30+% efficient instead of 16%. However, those are specialty solar cells designed for use in things like spacecraft (we used them on our satellites at Satellogic, for example.) Consequently, they are eye-wateringly expensive and not getting cheaper, and so nobody is building solar parks with them, particularly since non-arable land is abundant and will remain so for a couple of decades, while the prices of low-cost 16%-efficient solar cells are dropping like a hafnium pellet.
> The whole point of LEDs is that they are supposedly very efficient; around 40-50%.
No, LEDs are nowhere close to 50% efficient. LEDs have many wonderful attributes, including tunable color spectra, directionality, the possibility of being scaled down to submillimeter scales (hard to do with an incandescent bulb!) and, indeed, very good efficiency --- compared to other light sources, that is. The problem is, all light sources are shitty when it comes to efficiency; LEDs are just less shitty. That's why we charge our cellphones wirelessly with induction coils, not LEDs and expensive multijunction photovoltaic cells.
It's hard to get your hands on good efficiency numbers, because LED vendors don't quote any kind of absolute energy efficiency number in the datasheets, because they only publish luminous efficacy (because that's what people normally care about). In theory, we can derive the absolute energy efficiency using a luminous-efficiency curve: https://en.wikipedia.org/wiki/Luminosity_function. I'll see if I can do that in a separate comment.
> heat is not actually energy loss in a vertical farm.
This argument turns out to be wrong; I've explained why in detail in https://news.ycombinator.com/item?id=20906210, but in brief, 87% of the energy we're talking about gets lost in the solar park, not the hothouse, and artificial illumination to crop-growing levels produces so much heat that you need to air-condition the hothouse rather than heating it. Moreover, produced heat is always energy loss, because you can always reduce it further even by adequate insulation.
> Meaning that the reason vertical farming is getting a lot of attention is that the cost of energy has been dropping by rather a lot and is projected to continue to drop. Effectively this dominates variable cost in a vertical farm.
It's true that the cost of energy dropping, and to levels that would make people in the Space Age gasp. I still don't see how that justifies building a 30-hectare solar park to grow the same lettuce you could grow in a one-hectare greenhouse. I mean, how big is your armored vault hothouse going to be?
> You seem to be arguing this cost is too high. That seems to be countered by the many people actually growing stuff in greenhouses for decades this and making plenty of money.
No, man, that's not what I'm saying, man. I'm saying that if you're going to build a hothouse, make it a greenhouse. Daylight it, with skylights and/or lightpipes. Maybe supplement with artificial lighting some of the time. Lighting it with a solar farm that's thirty times as big is going to be more expensive, unless solar cells are thirty times cheaper than glass per square meter, and lighting it with fossil fuels is more expensive still. Fuck, thirty times cheaper than plexiglass. Thirty times cheaper than the shitty transparent plastic wrap we used to make greenhouses in Ecovillage Velatropa. If you're right and, against all odds, LEDs are now 50% efficient, exceeding the theoretical ideal luminous efficacy maximum Wikipedia gives, the threshold becomes fifteen times cheaper instead of thirty --- still improbable!
While I'm calculating the efficiency of LEDs for you, would you mind undoing your downvote, please, now that you know you entirely misread the main thrust of the comment you were downvoting?
Anyway, you seem to like numbers:
- https://ecotality.com/most-efficient-solar-panels/, So, 20-22% for commercial solar panels; not 16%. That seems consistent with numbers that I've heard elsewhere.
- https://www.dial.de/en/blog/article/efficiency-of-ledsthe-hi... So, 40-50%; with the rest being produced as heat because physics. You need both light and heat in a vertical farm or a greenhouse (which use lots of LEDs because the sun does not always shine). That seems consistent with the notion that I can touch an LED lamp and not burn myself. They are not producing a lot of heat and plenty of light.
Vertical farms are possible, economical, and possibly very lucrative because energy is cheap. Your argument is basically that because of inefficiencies in solar plants (real or imagined) vertical farms cannot possibly be economical.
Well that's a simple thing to calculate: kilo watt hours go in, kilos of produce come out. Either that adds up or it doesn't. For reference, the Netherlands is feeding most of Europe from a hundred square kilometers of wind powered green houses. Billion dollar business. Including in the middle of the winter when the sun is largely missing in action and it is cloudy, dark, and cold. It's been economical and highly profitable to do that for decades. To the point where Italy imports Dutch tomatoes.
Vertical farms are simply more efficient ways of doing the same things using largely the same kinds of technologies. The revolutionary thing is the level of automation and the ability to farm in, on top, or close to where the produce is used/sold. That seems to start making a lot of sense economically in a lot of places already doing this. The cheaper the energy, the more sense it makes.
There certainly are! If you think more carefully and pay more attention to what I'm saying, you can stop making them.
Again, I'm well aware greenhouses can be economical; that's my whole point --- greenhouses are more economical than indoor cultivation! It's unfortunate that your annoyance with my tone is leading you to put so much effort into rebutting things I'm not saying in the first place.
The part where the economics aren't going to work out is where we switch from gathering sunlight with glass or plastic windows to gathering sunlight with solar panels and reproducing it through LEDs, losing 97% of it in the process. (That's assuming 20%-efficient LEDs.) Even at the 48.7% LED efficiency in the article you cite, you're still losing 92% of the sunlight in this process. The only way that can work out is if 13 square meters of solar panel come out to be cheaper than one square meter of glass or plastic skylight in the greenhouse, or if the artificial lighting is used as a supplementary source of light (as you say has been done for decades), or if the power for the LEDs comes from something even cheaper than low-cost solar panels. That last is definitely a possibility in places like Scotland, Norway, or Iceland, where sunlight is scarce and other power sources are available.
This is analogous to discussions about desalinated water. With modern reverse-osmosis plants, desalinated water is astoundingly cheap: US$0.58/kℓ as of 2016 at Israel's new Sorek plant, for example, so you can fulfill the drinking, cooking, and bathing needs of a household for about US$7 a year. But it's no longer cheap when you consider water use on an agricultural scale, where (in medieval units) that's US$715 per acre foot, two or three times the price farmers in the US commonly pay.
So, yes, energy is very cheap, and will get cheaper. But energy on an agricultural scale is still not cheap, and solar panels will never make energy on an agricultural scale cheap. You need a cheaper source of power.
As for the high-efficiency solar panels, yes, there have been 21%-efficient solar panels for a long time, since the 1970s in fact. The multijunction solar cells we used on our satellites were 30% efficient, if memory serves, and multijunction cells in the lab have exceeded 40%. As the article you linked explains, the 22%-efficient panels are monocrystalline solar panels marketed as "high efficiency"; you can see in https://www.solarserver.de/service-tools/photovoltaik-preisi... that they consistently cost about 60% more per watt, and therefore 120% more per square meter, than the 16%-efficient "low-cost" polycrystalline solar panels that are universally used in new solar power stations. So high-efficiency solar panels don't turn out to be a cheaper source of power than low-cost solar panels, any more than diesel fuel is, except, say, in Antarctica. High-efficiency solar panels are what you use when paying twice as much per square meter is okay as long as you get 60% more energy out of your very limited roof.
I understand how, since you lack that deeper knowledge about the context, it sounds to you like I'm being unreasonably assertive and dismissive. But in fact my assertivity and dismissal are based on understanding aspects of the situation you just weren't aware of.
The article on super-efficient white LEDs https://www.dial.de/en/blog/article/efficiency-of-ledsthe-hi... is very promising! I very much appreciate you bringing it to my attention. The calculation method they outline is solid. Unfortunately, their results are not reproducible or falsifiable, because they don't say which LEDs have these remarkably high efficiencies. (They do say that most illumination LEDs are less efficient, but of course that's no bar to LED-illuminated subterranean hothouses --- you could just not use the inefficient LEDs.) Lacking information on the particular brand and part numbers as well as testing conditions (temperature and current, mostly), it's impossible to say whether their astonishing results indicate that these near-50% efficiencies are reliably achievable, whether they are achievable but only under conditions that are otherwise unfavorable in some way (water-cooling the LEDs, for example), or whether they simply amount to some kind of measurement or calculation error. The results I've seen on manufacturer datasheets and other reproducible, falsifiable sources unfortunately do not reach this level of performance.
Nevertheless, even if those surprising claims about LEDs do pan out, it doesn't undermine my core claim, which is that a square meter of skylight is going to grow more vegetables than a square meter of solar panels, and that the solar panels are not, in the foreseeable future, going to be sufficiently cheaper than glass or clear plastic to make this an economic win. Low-cost solar panels currently cost about €30/m² wholesale, plastic wrap on Amazon costs about €0.001/m², and the solar panels provide one-sixth the energy, one-thirteenth after going through a 50%-efficient LED, or one-thirtieth after going through a 20%-efficient LED. If the LEDs were 100% efficient and there were no transmission and storage losses, the cost of energy would still need to fall by a factor of a hundred and eighty thousand for the costs to become equal. That's 17 to 18 doublings; expect it around 2050 to 2060.
Beating durable plexiglass should come sooner: https://www.amazon.com/Cast-FS-Plexi-Glass-size/dp/B01LYK5RD... is US$300 (€270) for 14.9 m² of 3.2-mm-thick acrylic, which is US$20/m² (€18/m²). That's only a factor of 10.4 cheaper than (wholesale) low-cost solar panels, or a factor of 50 cheaper than low-cost solar panels powering 20%-efficient LEDs; solar panels are on track to beat that in a decade or two. It'll be interesting to see what they find to protect the solar panels from hail, though. Maybe it'll work for greenhouses too.
When typical solar panel gets 160 W/m2 output then the comparison isn't so lopsided as you describe.
First, yes, you do need heating in some places, but not as many as people usually think; the German Passivhaus program has demonstrated that you have to get to near-Arctic latitudes before adequate insulation isn't sufficient and you need active heating for a conventionally comfortable existence. https://en.wikipedia.org/wiki/Passivhaus
Second, the 84% of the energy that you lose at the solar panel doesn't provide heating in any useful way, unless the solar panel is inside your house under a glass roof or something. Only the 13% of the energy the LED wastes as heat is providing heating in a potentially useful way, and even then, it's only heating the vertical farm, not a dwelling space.
Third, as you know if you've ever been in a place with a glass roof, direct sunlight provides far too much heating. Most of the sunlight that comes through the greenhouse roof gets turned into heat, immediately or soon, except for the tiny percentage that gets captured in sugar. And these LEDs are providing about two or three times as much heat as the sun, per unit illumination. So the problem is going to become cooling rather than heating --- and cooling is an easier problem to solve, much of the time, if you have giant windows you can open.
Fourth, in the cases when you do need heating rather than cooling --- to ordinary temperatures like 25°, not some kind of process heat for a chemical plant or something --- you can get it several times more efficiently with a heat pump. Waste heat has a coefficient of performance of 1: every watt you lose provides one watt of heating. (Maybe 0.95 or something, but very close to 1.) Common heat pumps like the "aire acondicionado frio/calor" here in the house with me provide a coefficient of performance of about 2: every watt used by the compressor provides about 2 watts of heating, because it's sucking an additional watt out of the outdoors in the condenser coils and pumping it into the house. Good heat pumps like those used in ground-source heat-pump systems provide a coefficient of performance of about 6: you get 6 watts of heating for every watt of electrical energy that goes into moving that heat around.
So, even if you do need heating, wasting energy on electrical power is not a good way to get it.
So this is not a good argument for purely or mostly artificially lit farming.
If not then I doubt this is a commercially competitive strategy.
Much like coal vs solar it'll get there eventually but I'm highly skeptical of this working out right now.
Controlled farming has advantages on pesticide use, water use, location, automation etc.
So to my totally untrained eye...that seems like yes eventually that'll eat into the whole LED isn't free like sun advantage.
If you want to tell me something...do so.
I have better things to do that dig through your post history to figure out what you reckon you might have referenced that is important in your eyes.