
New ways to make vertical farming stack up - jkuria
https://www.economist.com/science-and-technology/2019/08/29/new-ways-to-make-vertical-farming-stack-up
======
sxp
>The biggest drawback of vertical farming is the high cost of the electricity
required to run the large number of LEDS...One way of saving electricity is to
use LED s that generate only the colours that plants require, instead of the
full spectrum of plain white light.

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.

~~~
bjelkeman-again
There isn’t much to be secret about really. When you ask any of the big LED
suppliers, like Philips or Hortilux, for a quotation, they ask what you are
planning to grow and they give you a lighting plan. The energy usage is
relatively predictable, if you know how the building you are in is insulated
and you know your ventilation requirements. It isn’t trivial, but it is
possible to do the numbers.

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.

~~~
cagenut
anything you share will be much appreciated.

~~~
bjelkeman-again
It will be shared over here (not much content yet and ugly, but release early
etc.) Translations to come.
[http://cirkularodling.se/](http://cirkularodling.se/)

------
decasteve
I’m a skeptic but vertical farming in the ocean might have more promise like
the 3-D ocean farm project. [0]

[0]
[https://www.bfi.org/ideaindex/projects/2015/greenwave](https://www.bfi.org/ideaindex/projects/2015/greenwave)

------
noetic_techy
Energy isn't vertical farmings only issue. The fact that you cannot grow
staple crops like wheat, soy, or rice indoors is the major issue. Most of what
these farms are best suited to grow can be considered "crunchy water" and not
nutritious enough to feed a planet.

~~~
ColanR
What about potatoes? Seems like those are a fairly good staple crop.

~~~
onlyrealcuzzo
Not sure, but I don't think root vegetables are good for growing indoors. They
need a lot of soil depth. I can't imagine it'd be efficient, but not sure...

~~~
kss238
you can grow root vegetables (at least some) hydroponically

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natmaka
Is it possible to use fiber optics, conducting the light (and UVs, maybe even
screening out unwanted ones) obtained from some dome-shaped collectors
installed outside (probably on the roof) to the culture?

[https://en.wikipedia.org/wiki/Light_tube](https://en.wikipedia.org/wiki/Light_tube)

------
neonate
[http://archive.is/YwnHT](http://archive.is/YwnHT)

------
vf3orfeas
Yeah that's a tricky one. First of all it has been settled that white light is
the way to go in order to enhance taste and other characteristics. The game is
in making led more efficient and plant factories or vertical farms more
automated. It also has to do with location, check Japan and China.

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 :/

------
kragen
dx7tnt responded with a most informative link:
[https://news.ycombinator.com/item?id=20905033](https://news.ycombinator.com/item?id=20905033)

The “food miles” thing is insignificant nonsense; see notes/strawberry-
miles.html in
[http://canonical.org/~kragen/dercuano-20190831.tar.gz](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.

~~~
jillesvangurp
Scotland exports more energy than that it uses. Most of that energy is wind
based; not solar. You are right that using nuclear of fossil fuels for this
would not be economically viable. Luckily, clean energy is cheaper and Norway
and Scotland export a lot of it. Especially Norway is rather dark and the only
way to grow stuff there most of the year is indoors.

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.

~~~
kragen
> _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._

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](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](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?

~~~
jillesvangurp
Well there are a lot of confused arguments being made. One of the reasons for
my downvote was that you are being rather assertive and dismissive. You speak
with an authority that is simply not there and citing numbers to make a point
that doesn't survive a lot of scrutiny.

Anyway, you seem to like numbers: \- [https://ecotality.com/most-efficient-
solar-panels/](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...](https://www.dial.de/en/blog/article/efficiency-of-ledsthe-highest-
luminous-efficacy-of-a-white-led/) 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.

~~~
kragen
> _Well there are a lot of confused arguments being made._

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...](https://www.solarserver.de/service-
tools/photovoltaik-preisindex.html) 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...](https://www.dial.de/en/blog/article/efficiency-of-ledsthe-highest-
luminous-efficacy-of-a-white-led/) 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...](https://www.amazon.com/Cast-FS-Plexi-
Glass-
size/dp/B01LYK5RDW/ref=sr_1_5?keywords=plexiglass+48+96&qid=1567924820&s=gateway&sr=8-5)
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.

~~~
rini17
I don't see anywhere any mention of spectral efficiency. Can't find any
reference number, but it seems plants grow the same under sunlight (say,
1000W/m2) as under LED lights that use only 250W/m2 or even less.

When typical solar panel gets 160 W/m2 output then the comparison isn't so
lopsided as you describe.

~~~
kragen
I'd be very interested! I agree, this would change the situation enormously.

------
Havoc
Did the sun start charging by kwh now?

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.

~~~
kragen
I don't think it'll get there eventually, unless I misinterpreted you? See my
top-level comment for the reasoning.

~~~
Havoc
>I don't think it'll get there eventually, unless I misinterpreted you?

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.

~~~
kragen
Sure, but as pointed out both in the article and my comment, you can get those
same advantages with a greenhouse, except maybe for "location".

~~~
Havoc
Honestly the whole...this discussion but also something I said somewhere else
is a very irritating style.

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.

~~~
kragen
Oh, sorry about that! I meant
[https://news.ycombinator.com/item?id=20905366](https://news.ycombinator.com/item?id=20905366)
\--- I was writing on my hand computer where copying and pasting links is a
pain.

------
akeck
Can you do vertical farming with light pipes?

------
dx7tnt
Link for those without the Economist:

[https://www.intelligentgrowthsolutions.com/the-economist-
gro...](https://www.intelligentgrowthsolutions.com/the-economist-growing-
higher-new-ways-to-make-vertical-farming-stack-up/)

