
Scientists create device that cuts desalination costs by 90% - ohjeez
https://tass.com/science/1083191
======
_Microft
They seem to be using a fast moving rotor with holes in the backside of the
blades that extract the steam from the cavity and then condense it.

\--- Links and related articles:

University: [http://www.sfu-kras.ru/en/news/22304](http://www.sfu-
kras.ru/en/news/22304)

Related paper: [http://research.sfu-
kras.ru/publications/publication/5140807...](http://research.sfu-
kras.ru/publications/publication/514080724-710372260) (doi:
10.1007/s11431-014-5631-0)

List of articles of the mentioned researcher (Kulagin) is at
[http://research.sfu-
kras.ru/publications/author/24184408](http://research.sfu-
kras.ru/publications/author/24184408)

(Nothing stands out on arXiv when searching for either desalination,
cavitation or Siberian Federal University)

~~~
this_was_posted
[https://sci-hub.tw/https://www.sciencedirect.com/science/art...](https://sci-
hub.tw/https://www.sciencedirect.com/science/article/abs/pii/S0011916418313912)
I think this paper is relevant

~~~
robocat
So you can suck the gas vapour through the back of the rotor blade, so long as
the rotor velocity is not exceeding the sound velocity of the gas?

It seems like you could make one at home or maker workshop with a hollow
shaft...

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jimrandomh
Headline is a lie; it's 90% cheaper only compared to a process that isn't
actually used. Flagged.

~~~
ChristianBundy
Could you add some more info on which process isn't actually used, or links to
resources that discuss it? I'm not familiar with the state of the art of
desalination.

~~~
nullc
The article is comparing to using atmospheric pressure distillation, which
isn't used for commercial scale desalination... reverse osmosis is primarily.

(Where waste heat is available for 'free' flash distillation , which is
already a lot more efficient than atmospheric pressure distillation, can be
attractive... but if heat isn't available for free, RO uses about 80% less
energy than multi-stage flash)

So it sound to me like it may well be in an apples to apples comparison the
method discussed in the article may be similar to or less energy efficient
than RO. But maybe it could be used to enhance the usefulness of flash
distillation for lower levels of waste heat.

------
5351254578
From what I can tell, its a cavitating bubble in a very fast flowing tube.
Then water vapor is extracted from inside the bubble (not sure how). Given the
energy required to keep the flow going, and the drip of clean water that would
result it should be easily calculable what the energy input/volume of water
is.

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darksaints
Membrane-based technology has already cut costs significantly over distilling,
and it is already commercially mature. It would be more interesting to compare
the costs of this to membranes.

~~~
dangerboysteve
Israel has been using the membrane process for some time. I think their only
issue how is dealing with the brine waste water.

~~~
ori_b
Dump it in the ocean? It's not like we're extracting water in sufficient
quantities to affect the salinity of the Mediterranean.

~~~
SAI_Peregrinus
The issue there is with the mixing rates. While we won't affect the overall
average dumping will create local zones of increased salinity, which can be a
problem.

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vavooom
What is the expected timeline for desalination technology? Even with continued
investment all efforts have seemed to plateau at some point when costs and
feasibility reaches a critical point.

~~~
barbecue_sauce
The major issue with desalination as far as I can tell is that it produces
toxic brine that proves problematic as far as disposal.

~~~
kardos
If the toxic brine is purely the extracts from the ocean water, you can toss
it back into the ocean (with appropriate dilution). If the toxic brine has a
bunch of additives that are a byproduct of the desal, then this is indeed
problematic. The article mentions that this method eliminates the need for
chemical additives so this could be a pretty low-impact method of desal.

~~~
ninkendo
> you can toss it back into the ocean (with appropriate dilution)

... what are you going use to dilute the brine? The water you just
desalinated? What's the point then?

Seems to me if your input is seawater, and your output is a separated-out set
of {fresh water, saltier sea water}, and you put the saltier sea water back in
the sea, you're going to create a localized concentration of high salinity,
no? Seems kind of unavoidable to me.

~~~
sachdevap
Not necessarily. You could mix it in processed sewage. Assuming processed
sewage is appropriately disposed off in the sea at limited locations with
precautions, this should work. One concern may be the sheer volume from
desalination might overburden the sewage disposal.

------
joshwa
There's a good review of existing and novel desalinization technologies,
including OP's supercavitation method, here:

[https://www.researchgate.net/publication/271673255_Large-
sca...](https://www.researchgate.net/publication/271673255_Large-
scale_water_desalination_methods_A_review_and_new_perspectives)

------
ars
90% compared to heating. But at scale no one desalinates by heating, it's all
membrane based.

I'd like to see an energy comparison to that.

~~~
bluGill
No citation, but from what I've heard in previous discussions heat and
membranes need about the same energy input. With heat you use the steam in
heat exchangers so you recover most of your input heat and only need to add
more to make up for inefficiencies (the system of course is never 100%
efficient). With membranes you need to supply power to the pumps to keep the
membranes at the correct pressure differential.

The above assumes engineering went into designing an efficient system. Pumps
are easier to make efficient, but at scale they are not necessarily better.

------
everdrive
Where does the salt go when you desalinate? At a large enough scale, would we
risk salting some area (or body of water) to death?

~~~
journalctl
The oceans are big. Like... really really really big. According to [1],
humanity uses about four trillion cubic meters of water per year. The oceans,
per [2], contain about 321,003,271 cubic miles of water. Adjusting units and
turning that into a percentage, we would use 4.154*10^-4 percent (0.0004154%)
of the ocean’s water per year.

My guess is we can just dump the salt back in. :)

Edit: actually add sources.

[1] [https://ourworldindata.org/water-use-
stress](https://ourworldindata.org/water-use-stress) [2]
[https://oceanservice.noaa.gov/facts/oceanwater.html](https://oceanservice.noaa.gov/facts/oceanwater.html)

~~~
orf
That didn't work for sewage or plastic though. The ocean is huge, which is why
if you look at the numbers then you can put all human garbage into it and it
won't even take up 0.001% of it.

In reality, the ocean is huge. So all that salt/garbage/whatever is
increadibly uneavenly distributed and will naturally collect in certain areas.
In the case of extra salt it could easily have an adverse effect on local
ecosystems.

~~~
BubRoss
The ocean is made of saltwater already, it wasn't made of garbage or plastic.

Also salt dissolves in water which is why desalination is needed in the first
place. Really think for a moment about what are saying must be true.

~~~
orf
Ocean water has a specific level of salt. Increasing that in specific areas,
by even a small amount, could have disastrous consequences. Life has evolved
in the ocean at a particular saline level.

The point is not that plastic dissolves I’m water, it’s that the saline
concentration won’t be spread evenly throughout the entire expansive ocean
without first increasing it locally.

~~~
BubRoss
That's not what you said originally, you said it would cluster together like
garbage and plastic.

~~~
orf
Did I? Or did I say it would be unevenly distributed?

> Really think for a moment about what are saying must be true.

Indeed.

~~~
BubRoss
> So all that salt/garbage/whatever is increadibly uneavenly distributed and
> will naturally collect in certain areas.

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maerF0x0
I dont understand why desalination is an interesting problem given that it can
be done whilst wasting minimal heat for processes that already need heat (or
cooling due to too much heat). Things like smelting, power plants, nuclear,
data centers...

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ncr100
How could this impact political problems?

My understanding of the Golan Heights and Israel vs Palestine is that it's
about water. Will this technology help with that problem?

~~~
shahar2k
it'll definitely help, israel already uses a massive percentage of it's
electric generation to desalinate water. (since the country grows quite a bit
of its own food)

from wikipedia "By 2014, Israel's desalination programs provided roughly 35%
of Israel's drinking water and it is expected to supply 40% by 2015 and 70% by
2050.[18] In recent years, Israel's annual use of water from the Sea of
Galilee has shrunk from 513 million cubic meters (in 2001-2) to just 25
million cubic meters (2018–19) as desalinated water has taken its place."

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EugeneOZ
This site should be added to the list of non-trustful sources. TASS is a
propaganda agency. Two last "S" are for Soviet Union (Sovetskyi Soyuz in
Russian) - this agency was made by communists as a propaganda tool and still
plays this role.

This news article, in particular, is a bs without proofs, without scientific
magazines citations - they post such bs to create an impression of "positive
news".

~~~
WaylonKenning
If requiring scientific magazine citations (which itself seems like a low
bar), is our standard for if submissions are accepted, then there ain't going
to be much news on Hacker News since most articles here don't meet that
threshold.

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EugeneOZ
This article is about scientific research.

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benevol
Here's the ultimate desalination technology that scientists will end up
implementing:

1\. Use nano-technology "bots" to attach magnetic particles to the salt in the
water.

2\. Activate strong magnets to extract the salt.

Among the two byproducts will be the water that will have healing properties.

The day this will hit the news, remember:

You read it here first.

~~~
jonwachob91
Why would they use nano-bots instead of just ligands ?

