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Simple, solar-powered water desalination (2020)

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Re: Simple, solar-powered water desalination (2020)

#231

Post by bruce511 »

squarefoot wrote: post #107

FTA: "Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of. In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers." The capabilities are freaking interesting, but let's say someone builds a big enough settlement on a…

There are two counterpoints to the issue of excess salt being an environmental hazard.

A) brine can be introduced back into the ocean combined with waste water. In the Cape Town drought of 2017 some small desalination plants were brought into service very quickly, and the brine was expelled in the same pipe as the outflow from a (treated waste) sewerage plant.

B) the ocean is big - very big - and at least by our coast seldom "calm". So outflow of anything would disperse very quickly. Hot-water outflow from a nuclear power station dissipates very quickly for example - typically within tens of metres of the outflow.

C) the natural salinity of the ocean varies a fair bit at the very local level - think river mouths - storm water - evaporation etc. Outside of specifc closed bodies of water (Dead Sea etc) we'd need desalination on a massive scale to even measure the impact.

Re: Simple, solar-powered water desalination (2020)

#232

Post by jonas21 »

dsr_ wrote: post #202
adrianmonk wrote: post #180

Earlier quoted context omitted.

I don't think they are talking about the impact on the environment. I think they are talking about the procedures for operating the equipment. The way I read it, they mean whoever operates this device does not have to periodically go empty some bin/tank of salt or brine. An analogy would be to a frost-free refrigerator. When you say the freezer compartment of your fridge is frost-free, you don't mean that it never ge…

If you operate it directly on the open ocean, towing it behind your sailboat, you don't have to do anything special. If you operate it in a commercial, protected context where you pump water through it, you will generate brine. If you operate it en-masse in the ocean, the things that are insignificant at the scale of 1 and 10 square meters may become significant at the scale of 1 and 10 square kilometers. All of thes…

It sounds like they're targeting small deployments in the developing world, at the scale of 1 to 10 square meters, not large commercial systems.

From the article:

> In production, they think a system built to serve the needs of a family might be built for around $100... The hope is that it could ultimately play a role in alleviating water scarcity in parts of the developing world where reliable electricity is scarce but seawater and sunlight are abundant.

The problem with brine from desalination plants is that it's released at high concentration in one spot. This would not suffer from that problem.

Re: Simple, solar-powered water desalination (2020)

#233

Post by regularfry »

isthisnametaken wrote: post #103
einpoklum wrote: post #80

> The system delivered pure water That's toxic! We can't drink pure water. You have to maintain _some_ of the minerals in there, you just want to take most of the NaCL out. Does the system avoid this over-distillation? i.e. is the water properly potable, or is it just not-salty?

Sorry, what? Pure water isn't toxic. And you can get minerals from other sources. That's like saying tap water is toxic because it doesn't contain a balanced diet of vitamins.

Distilled water isn't toxic per se, but it's definitely got harmful effects. It'll leach minerals out of your teeth, for instance.

Re: Simple, solar-powered water desalination (2020)

#234

Post by regularfry »

jokoon wrote: post #94
einpoklum wrote: post #80

> The system delivered pure water That's toxic! We can't drink pure water. You have to maintain _some_ of the minerals in there, you just want to take most of the NaCL out. Does the system avoid this over-distillation? i.e. is the water properly potable, or is it just not-salty?

Just add some artificial minerals, it can come in some powder form I guess.

A few years back Coca-Cola got in trouble by doing exactly this. What they were doing was taking tap-water, and purifying it so they could sell it as "Dasani" - not a mineral water product, exactly, but a "lifestyle drink" they called it.

The thing about water when it's pure enough is that it's remarkably odd. It's unpleasant stuff: it'll weaken concrete if it leaks onto it, apparently it'll damage brass and steel, and it'll leach the minerals out of your teeth, but only until the water is no longer pure enough to do so. So what people do is, as you say, add buffer minerals back into the purified water to take the edge off.

What Coca-Cola got wrong was the dosing: they put ten times the amount of buffer minerals into the water as they should have, and made it toxic. So they'd taken a perfectly safe tap-water supply and ruined it.

Re: Simple, solar-powered water desalination (2020)

#235

Post by youngtaff »

jarenmf wrote: post #53
rorykoehler wrote: post #44

Would it be possible to re-green deserts with this technology? Does anyone know of any studies on using this technology to combat climate change?

Greening deserts is not a good solution for climate change. In fact it might worsen climate change due to albedo changes. A nice video about this: https://www.youtube.com/watch?v=lfo8XHGFAIQ

Challenge with that video is it takes a very industrial approach to green deserts - mono cultures for trees, massive desalination plants to provide water etc

Some of the original ideas for greening deserts are permaculture based (https://www.youtube.com/watch?v=sohI6vnWZmk) which are a way more sustainable approach but won't bring around carbon reduction fast enough.

Re: Simple, solar-powered water desalination (2020)

#237

Post by shellfishgene »

EricE wrote: post #185
shellfishgene wrote: post #151

Earlier quoted context omitted.

Can you provide a source for that? I dove near a desalination plant exit pipe in Saudi, the impact on the marine live did not seem to big in the area. But it was a small plant for a few thousand people and we did not do a proper assessment. I don't doubt there is an effect, but am not convinced that the "release area just dying" is correct.

https://www.keiken-engineering.com/en/brine-disposal-how-eff... Brine disposal is indeed a complex issue. Should be noted the above URL is from a desalinization industry proponent so I would say it's probably a little more optimistically biased but it was one of the better summaries I found so it still has value from that perspective. If you do more digging around each of the solutions they discuss you can find more…

The link does not really show any evidence that marine ecology at brine outlets is disturbed. It does however suggest that pouring the brine on land or roads (for de-icing) are alternative solutions, which I doubt ;).

I was more thinking of proper studies, such as reviewed in [0], which says in the abstract: "Ecological monitoring studies have found variable effects ranging from no significant impacts to benthic communities, through to widespread alterations to community structure in seagrass, coral reef and soft-sediment ecosystems when discharges are released to poorly flushed environments. In most other cases environmental effects appear to be limited to within 10s of meters of outfalls."

So, impact yes, but "release area is just dying", probably not.

[0] https://www.sciencedirect.com/science/article/abs/pii/S00431...

Re: Simple, solar-powered water desalination (2020)

#238

Post by Scoundreller »

SamBam wrote: post #225
Scoundreller wrote: post #220

Earlier quoted context omitted.

Reminds me of a post here where it was some neural network chat/excuse generator. Just two people back and forthing about why they couldn’t meet up. I lost it when one of the excuses was, 3 weeks later “oh, I can’t meet for lunch on July 29th, I have to go to my mother’s funeral”

Amy way you can link to that conversation? I tried to find it on Google.

I think the convo is different each time. You’d have to search here for the chat itself. It was 2-3 months Ago

Re: Simple, solar-powered water desalination (2020)

#239

Post by justshowpost »

kevmo wrote: post #171
underwater wrote: post #52

Earlier quoted context omitted.

Yishan Wong, of Reddit CEO infamy, has been working on this for a few years: https://www.terraformation.com/

I seriously considered taking a job there (I did not for personal reasons, namely not wanting to move) and would recommend looking at them to others. I think they are poised to be a key player in the forestry and reforestation space in the next 2 decades.

But... the reforestation occurs naturally for last 2 decades (at least, more like for 3 or even 4)

Re: Simple, solar-powered water desalination (2020)

#240

Post by vr46 »

creshal wrote: post #145
Chris2048 wrote: post #129

Earlier quoted context omitted.

Can salt be compressed and then just buried?

Sure, it's just that in this regard it has no advantage over other desalination technologies. You always have to deal with the excess salt, MIT is dishonest in waving away these concerns.

Yes, the waste always has to go somewhere, the choices are really about how quickly and how concentrated the waste is. (And where it goes, I suppose)
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