
In field tests, device harvests water from desert air - evo_9
http://news.mit.edu/2018/field-tests-device-harvests-water-desert-air-0322
======
bdevine
Ok, I have a dumb question about this sort of technology. Aren't these devices
essentially just borrowing from tomorrow by capturing moisture that would have
eventually collected as clouds? Are there any long-term ramifications to using
these?

~~~
cornholio
Clouds are quite cheap. Most of them drop most of their water over areas that
would not significantly suffer from a marginal reduction of rainfall (the
oceans, the arctics, mountain ranges).

And a dryer average atmosphere should be partially compensated by increased
evaporation from the oceans. Overall, this technology should be applicable on
a continental scale before it shows any measurable effect on other areas.

~~~
thaumasiotes
> areas that would not significantly suffer from a marginal reduction of
> rainfall (the oceans, the arctics, mountain ranges)

Agreed as to the ocean and the arctic, but precipitation over mountain ranges
is generally recovered by lower-altitude communities when the water eventually
flows down to them.

Snowmelt has been a major source of water historically.

~~~
eloff
Also the artics are essentially cold deserts, they don't get much
precipitation and there is likely very little that could trace its origin to
the hot deserts of the world.

~~~
Cogito
That's not really true.

 _Parts_ of the arctics are definitely deserts, but that is not true for _all_
of the arctic regions.

Looking at the relevant parts of wikipedia [0] and [1], "annual precipitation
averaged over the whole planet is about 1000 mm" while "parts of southeast
Greenland [recieve] over 1200 mm". Antarctica has a lot less precipitation in
general, but there are still large parts of it that are not classified as
desert.

[0]
[https://en.wikipedia.org/wiki/Climate_of_the_Arctic#Precipit...](https://en.wikipedia.org/wiki/Climate_of_the_Arctic#Precipitation)

[1]
[https://en.wikipedia.org/wiki/Climate_of_Antarctica#Precipit...](https://en.wikipedia.org/wiki/Climate_of_Antarctica#Precipitation)

------
peterburkimsher
Could this be used on Mars?

The humidity at the surface is 30 to 75 ppm [1]. Clouds have been known to
form.

If Elon Musk gets interested, I think the MIT researchers could get the
investment they need to scale this up.

I'm just grateful to read some good news about scientific progress for a
change. Useful inventions like this give me more hope for humanity.

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4508910/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4508910/)

~~~
cwkoss
Very cool idea.

Few potential issues come to mind:

\- I bet dust would muck up the MOF

\- Dust would need to be swept off to allow sunlight energy to reach the solar
chamber.

\- Ambient temperature on mars in below the freezing point of water. May not
get enough sun to warm the MOF enough to drive off the moisture. EDIT: Found a
source saying that water vaporizes during the day because of the reduced
pressure - interesting.

------
ChuckMcM
This is pretty neat. From previous papers it is using temperature swing
adsorption[1] pull the water out of the air. Basically their MOF material
collects on its surface (adsorbtion) water at one temperature and releases it
(desorption) at the other. In this way, just by putting their material out in
the Sun light the day/night cycle will collect and then dispense the collected
water all passively.

The 'catch' is how expensive is it to produce the MOF and how long does it
work before it needs to be replaced. In an ideal world, with a cheap catalyst
and infinite lifetime, you could build a large tower full of this stuff and it
would pour water out during the desorption process.

[1] [https://www.ethz.ch/content/dam/ethz/special-
interest/mavt/p...](https://www.ethz.ch/content/dam/ethz/special-
interest/mavt/process-engineering/separation-processes-laboratory-
dam/documents/education/rcs%20notes/ArvindRajendran_AdsorptionBasics.pdf)

------
dieg0
Yes, you can extract water from air. You have just re-invented distillation,
in a painfully mind blowing way.

In Chile we have the driest desert on earth, the Atacama desert, this projects
have “tried” to address the challenge of getting fresh water in remote
communities located in such places. State funds have been directed toward
similar "science" projects. TV has dedicated time and resources to explore
this "idea".

This has to stop, the amount of water that you can extract from air is related
to the amount of humidity in that place's air. You don't need much to
understand that the amount of water in the air isn't much in places such as
deserts. And if you have lots of humidity in the air, you can probably get
water from other sources, such as rain.

~~~
tomc1985
You said it yourself, the Atacama is the driest desert on earth. I imagine
that environment would be the _most_ difficult to extract water from.

Develop the tech in easier locales then, once the major details are worked
out, target the outliers.

~~~
dieg0
Air already has X amount of water, you cannot get more than X. It doesn't
matter if X is very tiny like in deserts or very large like in the middle of
the pacific ocean.

~~~
tomc1985
Per cubic meter, sure, but there is a lot more of it than that to work with

We build our space equipment the same way... arrange for/synthesize/simulate a
close analogue of an environment for initial development and then move on to
the real thing once the initial quirks are solved. I certainly don't know the
science behind water extraction but I imagine an extremely dry locale would
not be the best place to be performing all your validation tests. Maybe start
with a kind-of-dry desert, or some other biome. Like Joshua Tree instead of
Death Valley...

------
patrickxie
could this idea work? tie these devices to balloons, so they can reach the
high humidities of the clouds, then when waters collect the balloons will drop
to the ground, dumping the water into a collector. as the water is dumped the
device rises again to continue humidity collection.

~~~
rungcc
Leave it to Silicon Valley to reinvent rain.

~~~
beamatronic
s/reinvent/disrupt

------
ghawkescs
What's the difference between MIT's prototype and Zero Mass Water?

[https://www.zeromasswater.com/](https://www.zeromasswater.com/)

Is it the minimum humidity rating?

------
s0rce
Gah, their own university press office doesn't even link to the latest paper.

Here is it after a quick search, open access too:

[https://www.nature.com/articles/s41467-018-03162-7](https://www.nature.com/articles/s41467-018-03162-7)

Seems interesting, for small, possibly off the grid, desert communities. Not
sure how the overall lifecycle energy demands would compare to say
desalination for most of the coastal population centers.

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wiz21c
Reminds me of Dune...

~~~
rglovejoy
More like Tatooine.

~~~
davidw
Was looking for the comments about getting a droid that understands the binary
language of their moisture vaporator.

------
black_puppydog
I don't see a link to the actual paper, or the title... Is the press office
concerned about scaring the general public with links to actual science?!

~~~
nkurz
No link, but at least they give enough information to search for it. I think
it must be this one:
[https://www.nature.com/articles/s41467-018-03162-7](https://www.nature.com/articles/s41467-018-03162-7)

~~~
beautifulfreak
"Here, we demonstrate an air-cooled sorbent-based atmospheric water harvesting
device using the metal−organic framework (MOF)-801 [Zr6O4(OH)4(fumarate)6]
operating in an exceptionally arid climate (10–40% RH) and sub-zero dew points
(Tempe, Arizona, USA) with a thermal efficiency (solar input to water
conversion) of ~14%. We predict that this device delivered over 0.25 L of
water per kg of MOF for a single daily cycle."

So what does a kilogram of the MOF cost, compared to the ordinary costs of
acquiring water in dry places?

------
noetic_techy
Couple this with algae growing and you could have a sustainable source of both
food and water almost anywhere.

Yes, algae cakes are nasty but beggars cant be choosers.

~~~
diyseguy
A quarter liter per day could easily water a tree. Reforestation seems
possible with this device.

~~~
hexane360
>One large tree can lift up to 100 gallons of water out of the ground and
discharge it into the air in a day.

This won't forest the desert. It may supplement a couple areas which could
_almost_ sustain trees, but trees are some of the most water-thirsty plants
around.

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sungx105
MOFs are generally notoriously unstable in water. Would a scaled-up system be
able to perform while maintaining functionality over many cycles?

~~~
fernly
right right right -- you have an extremely high surface area of metal and you
expose it to air and moisture. Why would it not oxidize in like minutes?

------
danbruc
Condensing water requires 2.265 MJ/kg, go figure how viable this is.

~~~
danbruc
Let me elaborate because this received a couple of downvotes. They only use
the metal-organic framework to adsorb water vapor from the atmosphere during
the night and then use sunlight to desorb it during the day which leaves them
with water vapor again. Now they still have to condense that into water and
their 2017 paper [1] shows that they use a Peltier element paired with a big
heat sink to do this. But this is the process that actually requires the most
energy, disiapating 2.265 MJ/kg of water which is enough energy to heat the
same amount of water by 541 K. Maybe I am missing something but to me it seems
like that metal-organic framework at best provides a marginal benefit over
simply condensing water on a Peltier element directly, which will, with an
efficiency of 15 % [2], still require about 4.2 kWh/kg.

[1]
[https://globalscience.berkeley.edu/sites/default/files/water...](https://globalscience.berkeley.edu/sites/default/files/waterharvesting.pdf)

[2]
[https://en.wikipedia.org/wiki/Thermoelectric_cooling#Perform...](https://en.wikipedia.org/wiki/Thermoelectric_cooling#Performance)

~~~
nkurz
I downvoted the original comment because I thought it was factually accurate
but misleading. The implication was that the amount of energy required made it
obviously nonviable, but you didn't actually show the work to make that case.
Without strong evidence, "go figure how viable this is" is an unhelpful thing
to say when someone claims to have a working prototype.

Your explanation here is much better (and I upvoted it), but I think it still
misses the major point that the authors claim that the new device _does not
use a Peltier cooler_. Instead, it's heated by the sun, and uses a passive
heatsink. I think it's the same mentioned in the earlier paper as "We also
report a device based on this MOF that can harvest and deliver water (2.8 L
kg–1 day–1 at 20% RH) under a non-concentrated solar flux below 1 sun (1 kW
m–2), requiring no additional power input for producing water at ambient
temperature outdoors.".

So I think the answer to your question is "Yes, it can be viable if you have a
convenient source of heat that can produce the necessary energy". 1 MJ is
about 270 Watt Hours, sunlight at noon is about 1000 W/m^2, and solar thermal
collection can be more than 50% efficient. This doesn't mean it's viable, but
as the new paper shows, if you have a square meter of sunlight available the
energy necessary for condensation is probably less of a limiting factor than
the collection of the moisture into the (currently exotic) sorbent.

------
cwkoss
I wonder if these could be used for irrigation without having to run water
lines.

How much does the MOF cost to produce?

What is flow rate?

How would wide-scale use of these in an area effect the regional climate?

~~~
portofcall
MOF’s are not mass produced, and while a method has been proposed to scale up
production, as far as I know it’s never been tested. It’s also a solvent-heavy
process, and often uses a lot of benzene.

MIT the university is an amazing thing, but MIT the press release machine is
pathetic.

~~~
gene-h
MOFs aren't mass produced, but it is possible to produce large quantities of
them. BASF has been able to make double-digit tonnage quantities of MOFs per a
single production run[0]. It much simpler to make MOFs than other
nanomaterials like carbon nanotubes and graphene. The MOF used in the paper is
somewhat expensive as it uses zirconium, but it is possible that MOFs based on
other metal ions could be used.

[0][https://cen.acs.org/articles/91/i51/Materials-Chemistry-
Meta...](https://cen.acs.org/articles/91/i51/Materials-Chemistry-Metal-
Organic-Frameworks.html)

~~~
philipkglass
Zircon (zirconium raw material) isn't very expensive. Removing hafnium from
zirconium compounds to reach nuclear-application purity is expensive. Reducing
zirconium compounds to metal is expensive. The authors start with zirconyl
chloride, which doesn't have either of those expensive requirements.

For anyone else wanting to read the full paper, it's open access in Nature
Communications:
[https://www.nature.com/articles/s41467-018-03162-7](https://www.nature.com/articles/s41467-018-03162-7)

------
m1el
This won't work. Purely because of thermodynamics. We already have devices
that suck water out of the air - dehumidifiers. They don't collect enough
water to drink.

Similar concepts were tried before:

\- [https://www.indiegogo.com/projects/fontus-the-self-
filling-w...](https://www.indiegogo.com/projects/fontus-the-self-filling-
water-bottles-sport-camping)

\- [https://www.waterseer.org/](https://www.waterseer.org/)

They're all bust because it can't work.

------
abakker
How much can it reduce indoor humidity in San Francisco...I'd love to have
that be a more energy efficient process, too.

------
tomc1985
Didn't some kid in Africa come up with a similar device with spare parts? How
come the MIT one needs all this exotic tech?

------
MentallyRetired
Now, can they make one that harvests drinkable water from the ocean?

------
thisacctforreal
>The system [...] was positioned on a Arizona State University roof. It’s
still early stages, and the water only measured in the millimeters

Millimeters is not a useful unit of collected water! Granted millilitres
wouldn't be much better without time as well.

~~~
firethief
That seems like exactly the unit. Just like when measuring rainfall, the
amount collected scales with the area of the equipment. What would you prefer,
mm/(mm)^2?

I would assume time is on the scale of per day; that seems, at least to me,
the only time unit they wouldn't have specified here. Of course, in an article
this bloggy it's not a given that the reasonable interpretation of such vague
units is the interpretation intended--but I think that there is a reasonable
interpretation.

~~~
delecti
Volume per unit of collection area per unit time at a given absolute humidity.

It might be a bit too technical, but anything less really can't give you a
sense of scale.

~~~
nkurz
The actual paper
([https://www.nature.com/articles/s41467-018-03162-7](https://www.nature.com/articles/s41467-018-03162-7))
actually gives something very close to numbers you want, although they express
it as liters/day/kilogram @ humidity. Here's the abstract:

 _Water scarcity is a particularly severe challenge in arid and desert
climates. While a substantial amount of water is present in the form of vapour
in the atmosphere, harvesting this water by state-of-the-art dewing technology
can be extremely energy intensive and impractical, particularly when the
relative humidity (RH) is low (i.e., below ~40% RH). In contrast, atmospheric
water generators that utilise sorbents enable capture of vapour at low RH
conditions and can be driven by the abundant source of solar-thermal energy
with higher efficiency. Here, we demonstrate an air-cooled sorbent-based
atmospheric water harvesting device using the metal−organic framework
(MOF)-801 [Zr6O4(OH)4(fumarate)6] operating in an exceptionally arid climate
(10–40% RH) and sub-zero dew points (Tempe, Arizona, USA) with a thermal
efficiency (solar input to water conversion) of ~14%. We predict that this
device delivered over 0.25 L of water per kg of MOF for a single daily cycle._

[https://www.nature.com/articles/s41467-018-03162-7](https://www.nature.com/articles/s41467-018-03162-7)

------
anonyx69
House Harkonnen will be pissed.

------
dogma1138
Looks like a peltier dehumidifier powered by a solar panel any one has any
idea what the breakthrough is exactly?

~~~
Zaak
No, this device is explicitly not one of those:

> The system, based on relatively new high-surface-area materials called
> metal-organic frameworks (MOFs), can extract potable water from even the
> driest of desert air, the researchers say, with relative humidities as low
> as 10 percent. Current methods for extracting water from air require much
> higher levels ... above 50 percent for dew-harvesting refrigeration-based
> systems

~~~
dogma1138
Thanks for trying to explain instead of simply cluelessly down voting but this
still does not answer my question.

This is a Peltier device you can see the power wires and the heat sink on the
hot side.

Are MOFs used in the construction of the Peltier for example are Cu3-BTC MOFs
used to increase the surface area of the cold plate which improves
condensation or are MOFs used as a membrane to increase the humidity in the
condensation chamber to above ambient?

I really don’t understand why people get triggered by honest questions and
decide to burry them.

~~~
philipkglass
The full paper is open access. Those wires are going to thermocouples, not
Peltier devices:
[https://www.nature.com/articles/s41467-018-03162-7/figures/2](https://www.nature.com/articles/s41467-018-03162-7/figures/2)

There _is_ a heat sink, but it's not dissipating electrically produced heat.
From the paper:

 _During day-time water production, the enclosure is closed and the solar
absorber side is covered with an optically transparent thermal insulator (OTTI
aerogel). The MOF layer is heated by exposure to solar irradiance, causing
water release (desorption). The desorbed water vapour diffuses from the MOF
layer to the condenser due to a concentration gradient. Accumulation of vapour
in the enclosure leads to saturation conditions and consequently, the
condensation process occurs at ambient temperature. The heat of condensation
is dissipated to the ambient by a heat sink._

~~~
dogma1138
Brilliant! Thank you for taking the time linking the paper looks very
interesting.

