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From seawater to drinking water, with the push of a button

news.mit.edu

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Re: From seawater to drinking water, with the push of a button

#61

Post by bruce511 »

MichaelApproved wrote: post #19
QuikAccount wrote: post #15

Earlier quoted context omitted.

You can pump brine water back but if I recall you can't just dump it all back at once because it's so highly concentrated. Ideally you would be able to find an alternate use for it.

For these small amounts, I doubt pumping it back out would be an issue but is that what they’re doing? I thought the metal plates were collecting the salt but the article and video don’t make it clear.

given the size of the thing it's likely to be positioned very close to the water source, so I expect it just dumps it outside the device. I mean, if I was running it on a boat, or next to the sea, I'd just basically pour the waste out right next to the device.

And I agree, at ounces per hour there's no need to dilute the brine, just dumping it is fine.

Re: From seawater to drinking water, with the push of a button

#62

Post by aaron695 »

denton-scratch wrote: post #51

> requires only 20 watts of power per liter. So if you want a liter, you have to supply 20 watts. For how long? Forever? Does the water instantly become turbid when power is removed? Tsk, tsk, MIT. I would have thought an MIT journo would know what a watt is.

No post body was provided.

Re: From seawater to drinking water, with the push of a button

#63

Post by smiley1437 »

Am I reading this wrong? It uses less energy at higher production rates?

This is a verbatim copy of the text at 1:32 in their video:

Seawater >> Drinking Water

~ 20Wh/L for 0.3L/h of production rate

~ 15Wh/L for 1.0L/h of production rate

so it uses LESS energy to get MORE drinkable water per hour?

That seems odd.

Re: From seawater to drinking water, with the push of a button

#64

Post by ratsforhorses »

MichaelApproved wrote: post #9
siruva07 wrote: post #4

Earlier quoted context omitted.

Maybe. I think Atmospheric Water Generators are much More likely to change the game since they don’t need a body of water other than the atmosphere.

“ Atmospheric Water Generators ” At first I thought you were just using a marketing term for dehumidifiers but I looked it up before posting. I see that term is used for tight mesh fabric that’s hung vertically as a passive matrix to collect condensation. While those are actually game changers, they unfortunately only work in special regions that have the needed weather and topography to make them work. I think there…

Atmospheric water generation (AWG) uses technology to produce potable water from surrounding air.

Here's a cool example of using the sun to do just that...

https://youtu.be/VQRAtwz3Igs

https://en.m.wikipedia.org/wiki/Atmospheric_water_generator

Re: From seawater to drinking water, with the push of a button

#65

Post by BeefWellington »

qayxc wrote: post #57
MichaelApproved wrote: post #20

Earlier quoted context omitted.

The article claims 3x more efficiency in a confusing sentence: ”Their prototype generates drinking water at a rate of 0.3 liters per hour, and requires only 20 watts of power per liter.” So the unit only produces 0.3 liters an hour but if you wait 3 hours and provide 20 watts of power (7watts/hour), you’ll have a full liter.

> So the unit only produces 0.3 liters an hour but if you wait 3 hours and provide 20 watts of power (7watts/hour), you’ll have a full liter. That doesn't make any sense. 20W of power draw over 3⅓ hours is ≈67Wh (Watthours, not Watts per hour), so 67Wh per litre (energy use; independent of time) and it takes 3⅓ hours to get this litre of potable water with 20W of power. In other words to get 1 litre in an hour, the d…

The wording in the article is specifically:

> requires only 20 watts of power per liter.

Whether the article is accurate or not I think you missed that.

Re: From seawater to drinking water, with the push of a button

#66

Post by [deleted] »

denton-scratch wrote: post #52
scoopertrooper wrote: post #44

Earlier quoted context omitted.

The article says they can get 1 liter for every 20 watts. So that'd give them 17,597 ounces per kWh.

It does say that; and you've converted between watts and watt-hours. The article's claim doesn't make sense.

[deleted]

Re: From seawater to drinking water, with the push of a button

#67

Post by qayxc »

BeefWellington wrote: post #65
qayxc wrote: post #57

Earlier quoted context omitted.

> So the unit only produces 0.3 liters an hour but if you wait 3 hours and provide 20 watts of power (7watts/hour), you’ll have a full liter. That doesn't make any sense. 20W of power draw over 3⅓ hours is ≈67Wh (Watthours, not Watts per hour), so 67Wh per litre (energy use; independent of time) and it takes 3⅓ hours to get this litre of potable water with 20W of power. In other words to get 1 litre in an hour, the d…

The wording in the article is specifically: > requires only 20 watts of power per liter. Whether the article is accurate or not I think you missed that.

The point is that 7W/hour is nonsensical. It's a non-unit and physically doesn't make sense in any context. The power is independent from the volume. Total energy use is volume dependent.

20 Watts per litre is mix of units that's nonsensical. Watt is Joules (Energy) per second (time), i.e. power. Either time is irrelevant, that is the device draws 20 Watts of power, in which case you can ditch the litre. Or the power draw is dependent on the performance in that more power equals higher throughput.

Neither case is in any way shape or form correctly described by "20 Watts per litre". Hope that makes it clearer now.

Re: From seawater to drinking water, with the push of a button

#68

Post by bombcar »

MichaelApproved wrote: post #34
dfsdf4sds wrote: post #24

Earlier quoted context omitted.

I want to thank you for your edit, and for keeping the original text. Recognizing something you said ignored portions of the argument, changing the argument, and keeping the original portion to show _why_ you were wrong but still adds to the conversation is very valuable. I commend you for your ability to double guess yourself

Thank you. And you’re right, I am amazing ;) But seriously the main reason I write these comments is to work through my thoughts as I try to articulate them and get feedback on what I’m thinking. I’m actually happy when someone points out a mistake because I learned something. When I’m right, I haven’t gained anything. Sure, my ego enjoys the satisfaction of being right but my already inflated ego doesn’t need anymor…

Heh sounds like what Socrates said - it’s better to be corrected than to be correct.

Re: From seawater to drinking water, with the push of a button

#69

Post by pnutjam »

electroly wrote: post #13
MichaelApproved wrote: post #6

Edit: I wrote out the comment below criticizing the efficiency of this device, when compared to reverse osmosis RO desalination (100x less efficient). However, they’re not trying to be more efficient than RO devices, they’re trying to be more compact, portable, and avoid the need for filters. They’re solving for a different problem than I was measuring them against. In my race to criticize, I overlooked those key det…

FWIW, I think you made a minor math error; you lost track of the 30 minutes. It would be 1 ounce of water for 3 watts of power over 30 minutes , which is 1.5 Wh of energy. That's 666 ounces per kWh.

Whelp... you just killed this tech by linking it to the Devil's number. hope you're happy. /s

Re: From seawater to drinking water, with the push of a button

#70

Post by Stevvo »

photochemsyn wrote: post #14

If this unit is shown to be durable, I imagine it's the kind of thing a lifeboat would have as part of its equipment. Low power means low volume of drinkable water (as energy is needed to separate ions from seawater, by the laws of entropy), so that's really unavoidable with this system. Compare to things like concentrated solar for complete removal of solids from wastewater and seawater, here's an interesting exampl…

This thing is going to cost more and be far less capable than a traditional suitcase or even hand-pump desalinator and you never see those on lifeboats.
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