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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

#31

Post by MichaelApproved »

fiddlerwoaroof wrote: post #26
MichaelApproved wrote: post #21

Earlier quoted context omitted.

Would dry regions that need water have enough cloud coverage for that to be viable? My guess is that any place with sufficient cloud coverage is already getting enough rain water to satisfy their needs.

I think there are parts of coastal California where there are clouds more of the year than rainfall. I'd also suspect if you just raised them up with balloons to cool them off and then brought them down where it's warmer, you could condense evaporation from the ocean, without spending energy directly on cooling.

You’d have to raise them up pretty high to get them colder than the dew point.

The energy it’d take to raise and lower the material would make it cost prohibitive.

I considered that the balloons would be a balancing force but don’t forget the rope length changes as the balloons go up and down. That changing length shifts the weight around. You can’t be balance against it.

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

#32

Post by tomxor »

MichaelApproved wrote: post #12
tomxor wrote: post #10

Earlier quoted context omitted.

From the article it sounds like they are looking for ways to scale down (i.e small portable units are the target form factor, not a mere demo), and this is where it compares favourably against things like reverse osmosis for efficiency.

I was so quick to criticize technology that I completely overlooked those points. Reading the article again, it’s embarrassing to see that I missed it when they were emphasizing it so much. I have one more lingering criticism that I don’t think they addressed (I reread it twice). What happens to the salt after it’s removed? If they don’t have a filter, where does it go? Do they pump brine water back?

Note that they are not merely aiming for portability, but efficient portability.

This particular passage is suggestive of their device being more efficient than RO at small scales, although no figures are given for comparison:

> Commercially available portable desalination units typically require high-pressure pumps to push water through filters, which are very difficult to miniaturize without compromising the energy-efficiency of the device, explains Yoon.

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

#33

Post by yyyk »

I recall similar in function devices already existed for military use - except they made water from air, which is even more available than seawater:

https://www.honeywell.com/us/en/press/2021/05/honeywell-led-...

https://edition.cnn.com/2014/04/24/tech/innovation/machine-m...

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

#34

Post by MichaelApproved »

dfsdf4sds wrote: post #24
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…

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 anymore stroking.

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

#35

Post by zmgsabst »

electroly wrote: post #27
MichaelApproved wrote: post #18

Earlier quoted context omitted.

It wouldn’t be the first time I made a mistake like that by not clearly identifying my units but I think I got it right. Let me rephrase and use watt/hour units. I was assuming it was a 50 watt panel that would only produce 30wh from the weak winter sunlight. Divide 30wh by two (since it was only ru Ning for half an hour) and get 15 watts generated to purify 5 ounces. Had they let it run for the full hour, they’d get…

Wh is a measurement of energy, but W is a measurement of power (that is, the rate of energy). They are different units of measurement and you're mixing them up here. Here, you've doubled the original rating of 15 watts up to 30 watts; that's the result of the confusion between energy and power. You don't divide the wattage in half when you run it for half the time, nor double it when you run it for twice the time; th…

You’re getting confused by their typo on units:

They meant 15 watt-hours in both cases, which would be half of 30 watt-hours — or a 50 watt panel for 30 minutes at 60% efficiency. (Which is the stated working premise.)

15 watt-hours -> 5oz would imply that 3 watt-hours -> 1oz, and hence 1 kWh is 333oz.

I generally try to assume best intentions — so if they repeated otherwise the same correct math, but for misnaming a unit, I try to assume they’re correct and typo’d.

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

#36

Post by MichaelApproved »

tomxor wrote: post #32
MichaelApproved wrote: post #12

Earlier quoted context omitted.

I was so quick to criticize technology that I completely overlooked those points. Reading the article again, it’s embarrassing to see that I missed it when they were emphasizing it so much. I have one more lingering criticism that I don’t think they addressed (I reread it twice). What happens to the salt after it’s removed? If they don’t have a filter, where does it go? Do they pump brine water back?

Note that they are not merely aiming for portability, but efficient portability. This particular passage is suggestive of their device being more efficient than RO at small scales, although no figures are given for comparison: > Commercially available portable desalination units typically require high-pressure pumps to push water through filters, which are very difficult to miniaturize without compromising the energy…

Good point. I wish articles like these would include figures. I’d love to know what they calculate RO efficiency to be at small scales and how far away they are from beating it.

Sure, that might be boring for some readers but they could throw a couple of sentences about it at the bottom.

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

#37

Post by MichaelApproved »

zmgsabst wrote: post #35
electroly wrote: post #27

Earlier quoted context omitted.

Wh is a measurement of energy, but W is a measurement of power (that is, the rate of energy). They are different units of measurement and you're mixing them up here. Here, you've doubled the original rating of 15 watts up to 30 watts; that's the result of the confusion between energy and power. You don't divide the wattage in half when you run it for half the time, nor double it when you run it for twice the time; th…

You’re getting confused by their typo on units: They meant 15 watt-hours in both cases, which would be half of 30 watt-hours — or a 50 watt panel for 30 minutes at 60% efficiency. (Which is the stated working premise.) 15 watt-hours -> 5oz would imply that 3 watt-hours -> 1oz, and hence 1 kWh is 333oz. I generally try to assume best intentions — so if they repeated otherwise the same correct math, but for misnaming a…

OP here. Thanks for understanding what I’m trying to say and putting it in the correct terminology.

However, I think I’d still make the same mistake in the future because I don’t understand how to express what the (assumed) 50 watt rated panel is generating over half an hour.

If it’s running at 60% efficiency then it’s generating at 30 watts per hour.

After an hour of running, we’ve accumulated 30 watts of energy.

If we only ran it for half hour, we’d have 15 watts.

Dividing that out tells me that 3 watts of energy will provide 1 once of water.

Does it matter if those 3 watts are provided over an hour via a 3wh power source or over 10 minutes via a 16wh power source?

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

#38

Post by zmgsabst »

MichaelApproved wrote: post #37
zmgsabst wrote: post #35

Earlier quoted context omitted.

You’re getting confused by their typo on units: They meant 15 watt-hours in both cases, which would be half of 30 watt-hours — or a 50 watt panel for 30 minutes at 60% efficiency. (Which is the stated working premise.) 15 watt-hours -> 5oz would imply that 3 watt-hours -> 1oz, and hence 1 kWh is 333oz. I generally try to assume best intentions — so if they repeated otherwise the same correct math, but for misnaming a…

OP here. Thanks for understanding what I’m trying to say and putting it in the correct terminology. However, I think I’d still make the same mistake in the future because I don’t understand how to express what the (assumed) 50 watt rated panel is generating over half an hour. If it’s running at 60% efficiency then it’s generating at 30 watts per hour. After an hour of running, we’ve accumulated 30 watts of energy. If…

This is what the other person was trying to say:

“Watt” is the unit of power which is the rate of change in “joules”, which is the unit of energy. In the way that “velocity” is the rate of change in “position”.

1w = 1J/s

A “watt-hour” is another way to represent joules/energy by integrating watts/power over time.

30 watts * 30 minutes = 15 watt-hours or 54 kJ.

30 miles/hour * 30 minutes = 15 miles or 24km

> Does it matter if those 3 watts are provided over an hour via a 3wh power source or over 10 minutes via a 16wh power source?

You have the units backwards:

You can get 3wh from 1 hr @ 3w or 10 min @ 18w.

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

#40

Post by timonoko »

Those specifications are much worse than 30 year old PUR-06. It makes one liter per hour with 20 Watts and fits in your pocket.

I tried solar panel and windshield wiper motor. But direct-drive windmill was much better as wind blows 24/7 on Baja. https://youtu.be/9xYXWISWv5I?t=390

Durability was the issue. I destroyed three units and average was 200 days / 1000 liters, because all-plastic construction. Found no limits on filter durability.

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