Making water from the air

[Elcid]

I ran across this Kickstarter campaign. I was wondering if this idea could work for boats.


20l per day is not too bad at 400W.


https://www.kickstarter.com/projects...rtles/comments


Disclaimer: I am not connected to this project in any way or form. I am not advertising for this Kickstarter campaign. Personally I would not back a new/unproven technology on Kickstarter. I would prefer to wait for the final product on the market event at a higher price.

[rslifkin]

I wouldn't consider that a viable replacement for a desalination based watermaker. The idea is good, but the power consumption isn't workable for a boat. 480wh to make a liter of water means it burns about 1.8 kwh per gallon. That's an entire day of power for some boats. Compare to the more efficient watermakers on the market that can make water far faster and for 15 - 17 wh/gal. This is using about 30 times more power, making it entirely impractical.

[Elcid]

You are right. For sailboats it's a no-go, but for catamarans who have the spare power? It also dehumidifies which can be quite the advantage.

[rslifkin]

Originally Posted by Elcid

You are right. For sailboats it's a no-go, but for catamarans who have the spare power? It also dehumidifies which can be quite the advantage.

Even on my powerboat I'd consider the power usage unmanageable. Unless I'm at a dock with power or wanted to run the generator all day, there's no way I'd have that much spare power. And it doesn't make very much water anyway. They say 20 liters (so just over 5 gallons) per day, and that's with it running non-stop. That's 9.6 kwh of power per day just to make 5.2 gallons of water. You'd need at least 2kw of solar panels and a large battery bank just to run this thing, not including any other power usage onboard.



Even outside of a boat, I'd consider the thing pretty much a last resort for when there's no other way to obtain drinkable water. It somehow manages to be less efficient than a traditional dehumidifier at extracting water from the air (possibly to keep the packaging small and handle filtration, etc.).

[Elcid]

I guess you did the math Maybe like you say, for places where you can connect to shore-power cheaply and the water quality is poor. But even then there are probably better solutions. e.g. an AC and a proper water filtration solution.

[Pete7]

Originally Posted by rslifkin

480wh to make a liter of water means it burns about 1.8 kwh per gallon. That's an entire day of power for some boats. Compare to the more efficient watermakers on the market that can make water far faster and for 15 - 17 wh/gal. This is using about 30 times more power, making it entirely impractical.

If you boiled a kettle of salt water for a couple of hours, I wonder how much steam that when cooled to fresh water it might produce?

Plus all that lovely sea salt for cooking

[thinwater]

Dumb on so many fronts, most mentioned above. A few more.



* Vs. tap water, calcium and magnesium are removed, which according to EPA and WHO is a bad thing. Good for batteries, but that's about it.

* Dehumidifier water is not all that clean. Everything in the air, concentrated. You can purify it ... but you might as well just filter the tap water...
* ... Unless tap water is unavailable. But if you live in a desert I bet it doesn't work (less water in the air).


Just dumb.

[rbk]

* Vs. tap water, calcium and magnesium are removed, which according to EPA and WHO is a bad thing. Good for batteries, but that's about it.

Not just bad, it can kill you if you keep it up long enough without supplementation. Strips the electrolytes and minerals from your body. Even drinking lots of potable water very fast can have similar effects leading to over hydration, water intoxication and death.

[Celestialsailor]

Originally Posted by rbk

Not just bad, it can kill you if you keep it up long enough without supplementation. Strips the electrolytes and minerals from your body. Even drinking lots of potable water very fast can have similar effects leading to over hydration, water intoxication and death.

I wonder if this is true (to a degree) with de-sals

[rbk]

Originally Posted by Celestialsailor

I wonder if this is true (to a degree) with de-sals

It would depend on how much dissolved minerals are removed by the de-sel and your diet. You can make up for the effects of drinking distilled water as long as you’re getting enough elec/minerals to replace those that are being removed. There is a well documented case where a radio station had a contest of how much water contestants could drink, short story the women died due to water intoxication. Being on a boat there is always the possibility that your diet is strictly limited and if you only have distilled water available and don’t know to mix in some sea water, your survival could be short lived. Same thing for high intensity activities, sometime even mineral water alone is not enough to replace the elec/minerals you lose through sweat.

[RaymondR]

You could put a little bit of sea water into it to add back salts and minerals.

Since one does not get a lot of cardio enhancing exercise on a boat, building a pedal powered high pressure pump to feed a membrane would probably produce more water whilst keeping you healthier.

Give it some thought, not as crazy and off the wall as it first might appear.

[valhalla360]

Originally Posted by Celestialsailor

I wonder if this is true (to a degree) with de-sals

I think it's one of those theories that have to be taken to the extreme to actually work out.

If it's the only water that you ever drink and you eat only an extremely low salt (and other minerals) diet...it may be an issue.

Reverse osmosis has the same concern but so long as you mix in some other water occasionally and salt your food to a reasonable level, it's not going to be an issue.

[valhalla360]

Originally Posted by Elcid

You are right. For sailboats it's a no-go, but for catamarans who have the spare power? It also dehumidifies which can be quite the advantage.

Back calculating 480wh/l...20l per day is going to need somewhere around 2400w of solar panels just to feed this device.

Keep in mind, the other power needs would require additional solar panels.

I don't know too many folks who have the space to oversize their solar system by 2400w. Heck even most catamarans would struggle to install 2400w of solar.

If you really want more water and don't want to buy a reverse osmosis system, you might look into a solar still. You could set it up on deck and mess around with it without spending a ton on a massively oversized solar array.

[thinwater]

Originally Posted by valhalla360

I think it's one of those theories that have to be taken to the extreme to actually work out.

If it's the only water that you ever drink and you eat only an extremely low salt (and other minerals) diet...it may be an issue.

Reverse osmosis has the same concern but so long as you mix in some other water occasionally and salt your food to a reasonable level, it's not going to be an issue.

Sail Delmarva: RO Water--What Are We Missing


There are links to WHO studies and some data here. Yes, it has to be extreme to cause the proven risks. Boat desal units are not good enough to cause the problems, plus unless you never leave the boat, you are drinking other water. No worries.


But it is not internet myth. The science is long -term and accepted by WHO and EPA. RO and distilled water for land dwellers are not a good thing unless there is no practical alternative, and then it should be supplemented.


But it does illustrate just how dumb the dehumidifier idea is. A lot of power and expense for not good drinking water.

[RaymondR]

Originally Posted by valhalla360

If you really want more water and don't want to buy a reverse osmosis system, you might look into a solar still. You could set it up on deck and mess around with it without spending a ton on a massively oversized solar array.

On my previous boat I had sun shades fixed to the boom and pondered building solar stills into them. They would have provided about twelve square metres of area when deployed and according to data I found somewhere (Israel military I seem to recall) during the summer would have provided my daily consumprion.