Desalination system that uses no external energy except the Sun and does NOT get fouled by salt accumulation. Cost: cheaper than tap water.
Unfortunately it’s still in prototype mode, but there’s no expensive components/materials. If there are any problems with commercializing it, they’ll likely be legal, since it was developed by a joint US-Chinese team (MIT & Shanghai Jiao Tong University).
Cool find. But …
“Doesn’t get fouled by salt” is a great feature. But desalination at any municipal or urban scale will still produce mountains of salt. Which is not a nice thing to have lots of piling up anywhere.
I suspect that even if we posit “unlimited free” electricity from solar, the salt disposal problem is what will prevent desalination from ever being more than a rounding error in humanities’ total fresh water supply & consumption.
The salt disposal problem could increase costs significantly.
But for a “household” (that is, small scale use) the increased salinity in the area in which it is being used may not be significant.
In addition to coastal areas this could be of benefit in arid regions where local water might also have an increased salinity.
I wonder if it is useful for water purification in general? In fresh water areas could it be used to produce cheaper tap water from local sources by removing pathogens, silt, etc.?
I think this is important.
Getting rid of the high salt brine is a real problem for any desalination plant.
It’s great they can make fresh water for little cost. That’s huge and exciting technology. Just gotta get rid of the salt.
I think the very same group had. some ideas for what to do with at least some of that salt…
Question: could the salt be used instead of mined salt? Salt mining is at least sometimes ecologically hazardous, and/or hazardous to the people working in the mines.
I expect the salt from desalinization would need more refining than salt from mines; but I don’t know whether that would make such use impractical.
Apparently the mining of other minerals from desalination concentrate [“brine mining”] could be an attractive proposition, if the NaCl content could be commercially viable.
Wait a minute. Bitterns?!?
Oh. Never mind. Bitterns.
Human language is confusing!
This is what I immediately thought of. But, there are countries that currently run desalination plants on a municipal or urban scale. The island of Aruba gets all their drinking water that way; when Mrs. Solost and I honeymooned there we were told that Aruba had (at least at the time) the second largest desalinization system in the world; second only to, I think it was Saudi Arabia. What do those countries do with all the excess salt, I wonder (though my wondering isn’t strong enough to spend a few minutes googling right now)…just dump it back into the ocean?
Yup. Right back into the ocean. Where it creates a large dead zone.
For round numbers there is about 5 oz of salt in a gallon of sea water. How much salt do you use in a day? How much fresh water?
Salt from salt mines is shipped long distances to places with no salt mines. I presume that salt from places that need desalinization plants could similarly be shipped to the many places that don’t need them. Everybody needs salt.
[quote=“LSLGuy, post:10, topic:990950, full:true”]
Yup. Right back into the ocean. Where it creates a large dead zone.
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yes, those become the chimneys into the sea of the future
good news is … that if done “right” you can just dillute it suffieciently (my means of currents and undertow, etc…) to spread it out - via many smaller diffusers - over a sufficienty large volume of sea to not really make that a problem.
Plus - chances are you not going to see one desal. plant next to the other …
but yeah … pretty much all we are ever doing is pushing a bottleneck up to the next problem.
Yes, everyone needs salt, and not only for seasoning food.
But the point of my numbers is the volume of salt produced by desalination is so gigantic compared to the volume of fresh water produced that even tiny amounts of desalination will produce more salt than all of humanity can use. 100% of the remaining salt will simply be a pollutant to be (expensively) disposed of.
If desalination somehow became widespread and routine we could indeed close all the traditional salt mines. And we could divert WAG 1% of the desalinator salt to replace 100% of worldwide salt mine output. Still leaving us with 99% of the desalinator salt to dispose of.
tldr: It would be a way to stop salt mining. It would not be a way to dispose of meaningful amounts of waste salt.
The answer to the waste salt problem is to put it back into the ocean. But spread out enough that it doesn’t create ecological disaster at the point(s) of effluence. Unlike current practice.
There are ways to cope with the excess salt but the issue is it is expensive to do well (responsibly).
Seems like the fresh water created also ends up back in the ocean eventually, after going through people’s showers and toilets, etc. Maybe put the salt back in at that point? Add the brine to the outflow of the sewage treatment plant. Would be mostly a closed loop (with some losses to evaporation) so the water going back to the ocean would be only a little saltier than came out.
Wouldn’t be at the same place on the coast (folks don’t want the drinking water intake by the sewage outflow even if it has been processed to be safe) so would take some pipelines.
Good thinking. Some fraction certainly does, but a lot of fresh water goes to agriculture and to landscaping. Very little of which goes anywhere capturable after that; it’s evaporation or into the ground or incorporated into the vegetation.
Whether the amount of capturable runoff and sewage treatment plant effluent would be a meaningful dilution to the high-test desalination brine effluent is an interesting analysis. Or could we do just as well in terms of dilution with less total plumbing just by spreading the raw desalination effluent out in the ocean across miles of small outlets, rather than 1 or two big ones?
Not a question I can answer, but certainly one that engineers in the business could.
When i was in Israel this summer they told me all the tap water chimes from desalination. So Israel and Saudi Arabia and… We already have nation-sized desalination programs. Making it cheaper seems like a win.
Wonder if we could dump the salt on already existing salt pans? Those are places already covered over with a layer of salt, after all, with large areas devoid of life.
(Let’s not dump it in desert areas that do have life, however scanty)
You’d have to pay to truck that salt out there and have bulldozers spread it out. Expensive (desalinization plants produce a LOT of salt).
With nation-sized brine discharge environmental impacts.