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(15,589 posts)
Mon Oct 2, 2023, 05:47 PM Oct 2

Ingenious solar distiller makes fresh water from seawater for less than 1cent a gallon

It’s pretty easy to get the salt out of seawater. All you have to do is boil it, freeze it, or just wait for rain! But those things take a lot of energy and/or time that many of us don’t have to spare. So people have been working on low-cost and low-energy-input ways to do it, such as solar desalination.

We seem to have hit on a really good one here, thanks to a collaboration between MIT and Shanghai Jiao Tong University (SJTU). I couldn’t even cram all the benefits of this thing into my diary title.

This device breaks the record for rate of fresh water production from seawater by a solar device, and as awesome as that is, it’s actually kind of a charming side note. The bigger breakthrough is that the device can keep running up near this rate for a long time without getting fouled by salt accumulation, and it does this by emulating natural processes that occur in the sea. That cuts costs by about 10x compared to typical solar desalination, making the cost of the fresh water it produces comparable to that of tap water.

Oh, and because it doesn’t accumulate salt, it can process water containing up to 20% salt (seawater has only 3.5% salt, and salt-saturated water has about 26%). Other solar desalination devices can’t even operate with water that salty. That means you can use this kind of device to process the wastewater from existing desalination systems, to get even more fresh water.




(109,627 posts)
15. Two questions remain, build cost and scalability
Tue Oct 3, 2023, 12:33 AM
Oct 3

If the build cost isn't prohibitively expensive and it can be scaled up, it will help people all over the planet.

People along the Gulf Coast and much of Florida are going to need this sooner rather than later.


(51,148 posts)
3. Good news. Hope the partnership with the two higher-ed entitines...
Mon Oct 2, 2023, 06:00 PM
Oct 2

works out well bor both.

A question: Can the salt accumulation from other desalination methods be recycled...maybe as table salt, or salt pelletts for home water softening/hot water tank systems?



(2,580 posts)
4. Just in time,
Mon Oct 2, 2023, 06:02 PM
Oct 2

with sea levels rising due to global warming, that surplus seawater can be used to quench our ever growing thirst!


(15,589 posts)
5. it looks to be cheap to build and 1 cent per gallon.
Mon Oct 2, 2023, 06:27 PM
Oct 2

The upshot of all this is that the device can make fresh water from seawater for about 0.2 cents a liter, and a device the size of a simple card table could produce around 5 liters of fresh water an hour (for 1 cent!)


(5,586 posts)
7. Here's an article about this on the MIT website
Mon Oct 2, 2023, 06:41 PM
Oct 2

Engineers at MIT and in China are aiming to turn seawater into drinking water with a completely passive device that is inspired by the ocean, and powered by the sun.

The configuration of the device allows water to circulate in swirling eddies, in a manner similar to the much larger “thermohaline” circulation of the ocean. This circulation, combined with the sun’s heat, drives water to evaporate, leaving salt behind. The resulting water vapor can then be condensed and collected as pure, drinkable water. In the meantime, the leftover salt continues to circulate through and out of the device, rather than accumulating and clogging the system.

The researchers estimate that if the system is scaled up to the size of a small suitcase, it could produce about 4 to 6 liters of drinking water per hour and last several years before requiring replacement parts. At this scale and performance, the system could produce drinking water at a rate and price that is cheaper than tap water.

The team envisions a scaled-up device could passively produce enough drinking water to meet the daily requirements of a small family. The system could also supply off-grid, coastal communities where seawater is easily accessible.


(18,600 posts)
8. Still far too expensive for agriculture
Mon Oct 2, 2023, 07:18 PM
Oct 2

An acre foot of water can sell for $500-$1000 in California for irrigation.

That's almost 326,000 gallons.

At a penny per gallon, it's over 3X as expensive as the most expensive water farms buy today. Crops use insane amounts of water, especially in dry regions with sandy soil.

And agriculture is what consumes the vast majority of water in water-stressed areas like California. Water for cities is a small fraction of the water needed.


(61,940 posts)
9. I Think We Need Scale-up Effects Completed
Mon Oct 2, 2023, 07:50 PM
Oct 2

There are typically significant per unit cost reductions in continuous processes scaled to industrial scale.
Did that for a living for 20 years or so, and we were sometimes surprised at how direct burden per unit mass dropped as scale increased.
Let's hope that's the case here. Don't have enough detail to make an educated guess about thus one.

Red Mountain

(1,598 posts)
11. The price of certain foods is going to go up
Mon Oct 2, 2023, 08:12 PM
Oct 2

the largest fastest rise will be for crops grown in regions they are not well suited for.

I don't know how the cost of irrigation compares to other inputs.....labor, fertilizer, etc.

I'm guessing it's one of the smaller ones.


(4,725 posts)
12. How much fresh water does it produce?
Mon Oct 2, 2023, 08:14 PM
Oct 2

How many gallons per minute, hour or day?

We have a massive desalination plant here on the coast, Adelaide South Australia.
Reverse osmosis - Google it.

How it is powered and how much per gallon it costs is unknown, unfortunately.

It's mothballed at the moment, but in next multi-year draught it will come in use.


(946 posts)
17. I wonder if a method like this could be used for polluted water as well.
Tue Oct 3, 2023, 08:45 AM
Oct 3

It seems like it could potentially be adapted to help with polluted waters as well.

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