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

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

#91

Post by jillesvangurp »

sp332 wrote: post #78
qayxc wrote: post #55

Earlier quoted context omitted.

> Desalination will never scale to a level suitable to supply that industry. Are you sure about that? It's simply a question of economics. As long fresh water from other sources is significantly cheaper, no one's going to invest in large scale desalination. Once this changes it becomes a question of which is more expensive - shutting down the agribusiness or running large scale desalination (which has options, from n…

It is true in California, because you need to dump the concentrated brine somewhere, and doing that at industrial scale will run up against environmental protections.

There's a big bucket right next to California called the Pacific. Perfect place for sourcing water to desalinate and dumping brine back into without doing anything measurably harmful to salt concentrations in the Pacific. It's like a literal drop in the ocean. Most big Californian metropolitan areas are right next to it. There is no water shortage; just a reluctance to pay a fair price for it.

The challenges in California are not technological but political and policy related. Local consumers of water seem to assume that water is like manna from heaven that has to be perpetually subsidized by the government. They feel entitled to it but are not really willing to pay for it; or even invest in common sense ways to reduce their consumption of it because it doesn't really cost them anything.

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

#92

Post by xtracto »

netsharc wrote: post #56
yellow_lead wrote: post #49

Anyone else notice in the beach video that the researcher filled the cup using tubing that was previously on the ground, then drank it? Looks cool though :)

He did wipe the sand off the output tubing... good enough? I guess if I dropped a drinking straw on the ground in an e.g. parking lot, I'd throw it away, but if I dropped it on sand in the beach, I would think "just wipe the sand off and it's clean!"

Back in the day when I went camping with my parents we used to "wash the dishes" using seawater and sand from the beach. Nowadays people are unnecessarily germophobic.

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

#93

Post by denton-scratch »

SamBam wrote: post #75
denton-scratch wrote: post #52

Earlier quoted context omitted.

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

I feel like nobody watched the video (although I do wish the article text had been clearer). The video specifically shows (at 1:34) that the machine operates at 15Wh/L (for the larger version, the smaller version is 20Wh/L). This is 15Wh/33 oz (since we seem so set on using customary units), or 2200 oz per kWh.

I didn't; I don't generally follow video links, unless I deliberately went looking for a video. Specifically, I don't follow many video links from HN; I treat HN as a text/plain site.

So my remarks were only about the article text.

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

#94

Post by denton-scratch »

soVeryTired wrote: post #53
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.

> Their prototype generates drinking water at a rate of 0.3 liters per hour, and requires only 20 watts of power per liter. Not great phrasing I agree but the information is there.

The trailing "per liter" seems the problem: I think maybe what they mean is that 20W gets you 0.3 liters per hour? So their machine produces 0.3 liters per hour, and draws 20W?

I wish journos wouldn't bandy around terminology and statistics they don't understand. It's getting worse.

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

#95

Post by qayxc »

BeefWellington wrote: post #81
qayxc wrote: post #67

Earlier quoted context omitted.

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…

Science reporting is not great but colloquially people use 20W per as a way of meaning Watt-hours. If this is correct, they're saying it takes 20 watts (meaning Wh) to deliver a Litre of water, over three and a bit hours. The time is provided just obfuscated by their "we deliver 0.3L/hour" statement, so by saying 20W/L it does sort of make sense within the context. ~6W/hour (if it means we use a total of 6Wh) would b…

> Science reporting is not great but colloquially people use 20W per as a way of meaning Watt-hours.

After watching the video I can confirm that it's actually 20Wh/l for 0.3l/h and 15Wh/l at 1l/h (I'm a bit puzzled how that works, but hey - that's what the inventor says).

> It could be worded better but I think this is what they're trying to say is that they're consuming 6W.

I would be happy if they'd manage to simply repeat what was said in the video. This is the official MIT news portal after all and I would expect it to be run by people smart enough to use the correct units, but alas...

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

#96

Post by tzot »

sandworm101 wrote: post #87

>> The researchers also created a smartphone app that can control the unit wirelessly and report real-time data on power consumption and water salinity. No no no no. I was all onboard with this seemingly wonderful product until I hit that line. The things that provide fresh water, that actually enable life functions, should NEVER involve controller aps. Switches. Dials. Positive on/off switches. Maybe the occasional…

>> The researchers also created a smartphone app that can control the unit wirelessly and report real-time data on power consumption and water salinity.

> No no no no. I was all onboard with this seemingly wonderful product until I hit that line. The things that provide fresh water, that actually enable life functions, should NEVER involve controller aps. Switches. Dials. Positive on/off switches. Maybe the occasional touchscreen. But please do not put the need for a working/charged/connected cellphone between the user and their source of fresh water.

You are objecting to a strawman of your own creation. Before you hit that line, you read “The technology is packaged into a user-friendly device that runs with the push of one button.” and “The researchers designed the device for nonexperts, with just one button to launch the automatic desalination and purification process.”

And then comes the line that triggered your reaction: “The researchers also created a smartphone app that can control the unit wirelessly and report real-time data on power consumption and water salinity.”

The key word is “can”. “Can control”, “can report”.

So you have the simplest possible device: press a button on the device, extract drinkable water. You want status updates / remote control? Use the app, which is optional; nowhere in the article it is stated that the app is necessary.

So you might reconsider your stance and get back onboard with the product.

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

#97

Post by antisthenes »

bombcar wrote: post #68
MichaelApproved wrote: post #34

Earlier quoted context omitted.

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.

It's even better to be correct after being corrected by yourself.

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

#98

Post by SamBam »

dehrmann wrote: post #22

> The suitcase-sized device...can also be driven by a small, portable solar panel, > Yoon and Kang used machine learning to find the ideal combination of ICP and electrodialysis modules. These bits feel like they were added because ML and solar power will get more clicks.

ML maybe, but solar power definitely not. They show an example use-case as a single-family house in a site of flooding and devestation. An emergency desalinator would definitely need to run off of a small generator or solar.

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

#99

Post by SamBam »

denton-scratch wrote: post #94
soVeryTired wrote: post #53

Earlier quoted context omitted.

> Their prototype generates drinking water at a rate of 0.3 liters per hour, and requires only 20 watts of power per liter. Not great phrasing I agree but the information is there.

The trailing "per liter" seems the problem: I think maybe what they mean is that 20W gets you 0.3 liters per hour? So their machine produces 0.3 liters per hour, and draws 20W? I wish journos wouldn't bandy around terminology and statistics they don't understand. It's getting worse.

It isn't, though, because that would be 60Wh per liter, but the video actually specifies it's 20Wh per liter.

They just stupidly used watt instead of Wh in the article text.

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

#100

Post by SamBam »

smiley1437 wrote: post #63

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.

They show that the 1L/h version uses more elements.

I assume there are some efficiencies as you get larger.

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