The latest water collection fad:

>>8885547
>engineers

The majority of them are art and design students. Either that or they're continental Euro """engineers""".

>>8885553
There's a recent one (with a published study) by MIT engineers?

File: 0413SNOWWaterHarvester.jpg (57KB, 699x792px) Image search: [Google]

57KB, 699x792px

>>8885547
What the fuck are you even talking about? The current breakthrough that everyone is talking about does not use a peltier cooler:
http://www.sciencemag.org/news/2017/04/new-solar-powered-device-can-pull-water-straight-desert-air

File: ajk6un2jg7jqm2nvse4t.jpg (87KB, 1200x630px) Image search: [Google]

87KB, 1200x630px

>>8885927
There are quite a few overly designed peltier condensers that have come out very recently.

>>8885547
They're fucking retards all of them

All these engineers working on this shit and didn't put a lick of thought into any thermodynamics or as to why this shit either doesn't work or isn't efficient at all

>>8885940
This one was just a gigantic blunder. Someone calculated that even at 90% humidity it'd take like 48 hours of perfect daylight to make a liter of water or something

>>8885927
>grabs and holds water molecules

How do they grab water but not air? Diatomic oxygen is larger than water molecules

File: 54c9747317a53_-_silica_packet_0410-lg.jpg (53KB, 500x375px) Image search: [Google]

53KB, 500x375px

>>8885955
Think of it as a giant silica gel packet. Like silica gel it can release water and be dried out when heated. Except it does so at a much lower temperature than silica.

>>8885927
This is really interesting. But for some reason I feel like it should need some sort of work input to do what it does.

>>8885955
One, Metal Organic Frameworks (MOFs) have a fuckload of surface area per unit mass or volume.

Two, water is a polar molecule and is attracted slightly to metal sites in the MOF. So when water diffuses into the MOF it tends to stay there.
This paper has a more indepth discussion:
http://pubs.rsc.org/-/content/articlelanding/2014/cs/c4cs00078a

A better question though is how the fuck can these things absorb water and not get destroyed by the water.

>>8886022
And there is, you need a temperature differential between day and night. Otherwise, the MOF just gets filled with water and doesn't release any

Won't you need a fuckload of air to go through that "sponge" even in a humid place?

>>8886031
>absorb water and not get destroyed by the water
It is clearly stated in the abstract of the article you linked to: water is aDsorbed, not aBsorbed. Big difference.

File: DSCN3393b.jpg (95KB, 1024x768px) Image search: [Google]

95KB, 1024x768px

>>8885547
I literally did this like 3 years ago. Only I hooked them up to my old exercise bike that I turned into a recumbent electric generator. I got water, but it was a shit load of work and only works well when the dewpoint and humidity are in the right ranges. The solar version I made was better, but not really worth it for me.

There's actually a indiegogo or something that does the same thing, only it uses a normal bicycle and you create the energy as you pedal. Google, "Fontus". The unit makes water as you ride. (There is also a solar version I think.) Terribly inefficient of course and getting that much power to dehumidify would put a lot more work into your bike ride. I can attest to this personally. You literally sweat out more water than what it can make for you, while you are trying to make water, even if you are merely using the bike for normal travelling.

>was going to post a pic of mine, but turns out I only took like 1 pic and not of the working model.

>>8885927
The device on the bottom is a Peltier heat pump, you muppet. Look at their current mock up.

>>8886177
I see they changed it to all solar now. lol I guess they realized how terrible the cycling for power was.

https://www.indiegogo.com/projects/fontus-the-self-filling-water-bottles-sport-camping#/

>>8886186
That is only for testing purposes. They don't need one for a practical device

>>8886198
How? How is it going to stay cool without work done to cool it down (which would be a heat pump)?
Here's something that might aid your thinking:
>https://www.youtube.com/watch?v=EGTRX6pZSns

File: MIT-Solar-Water_0.jpg (268KB, 948x632px) Image search: [Google]

268KB, 948x632px

>>8886198
Also, I found a neat picture of the current device:
>Note the heat pump below the crystals.
>Note the giant heat-sink below the device.
Mhm, that's 'really' going to work without a heat pump.
Without a heat pump, it will be even more infeasible, as it would heat up to the point of not being able to condense the water vapour.

>>8886205
>42mins

Nah, fuck that.

>>8886210
>TL;DR: It doesn't work on a fundamental therodynamic level. And the claims of litres condensed haven't been achieved and are rather their GOAL. However, due to poor reporting it was twisted. And he it would take about a year of constant work for it to achieve the litre goal.
I think that is the general summary.

>>8886217
Thanks.

I wonder how long it'd take me to pedal enough to make a liter with mine. Though, I'd have to rebuild it since I've used those Peltiers for tons of things since then. I wonder why they don't have a heat sink on both sides.

>>8886205
>>8886209

It cools down at night. The researchers were impatient so they made it 'night' with a peltier cooler.

>>8886322
Do you still know how inefficient and ineffective that will be?
Please, watch the video if you don't understand it in a such an overt way.

>>8886322
Also, let's conduct a thought experiment:
>Box is opened, 'filling' it with humidity.
>The desiccant adsorbs a measure of water.
>The Sun heats the desiccant and releases water vapour.
>As is cools a large amount of the water vapour is re-adsorbed due to the water vapour rising up back into the desiccant as it hasn't cooled enough to lower its energy state.
>Sun starts to go down and it soon becomes night, during this, the remaining smaller amount of water vapour cools enough to be collected.
Whoa, so efficient. :^)

>>8886334
Can I get a quick run down?
>>8886344
>> readsorbed
Close off the MOF once it has been desaturated with a divider

>>8886366
You're smarter than MIT engineers, well done.

>>8886366
>Can I get a quick run down?
I did one here: >>8886217

>>8886369
So why doesn't it work?

>>8886370
Basically, it takes a mammoth amount of energy to lower its energy state and even once you have, the amount of water it would collect (even with an active Peltier device), it would take something along the lines of a year just to manage a litre, let alone three litres.

>>8886382
And thats at optimal conditions, so in a desert, with far lower humidity, it would be much longer.

>>8885927
Thats literally a peltier cooler

They don't have any evidence that supports this 2.8L per 12 hours bullshit

it takes 2200kj to make 1 L of water go from liquid to gas, 2.8L is pretty much 3L so thats 6600kj for 3 liters.

Where is all that fucking energy coming from? certainly not the solar panel and certainly not the peltier device running that much energy.

Its another fucking farce by a bunch of retarded graduate students at MIT who didn't think about basic thermodynamics

>>8886370
Basically it takes a buttfuck ton of energy to condense water from a gaseous state and this dinky solar technology shit can't do it

File: 1490493955566.gif (911KB, 360x202px) Image search: [Google]

911KB, 360x202px

>>8887132
>6600kj

That's 1.833kwh. Solar energy is about 1kw per square meter. The best world record solar panels only get 46% efficiency (0.46kw per square meter). The device only uses passive solar, not active, and isn't actually powered using a Peltier cooler (that is for day/night cycle testing only.) The square area of solar energy is only 17.78cm squared (there's 10k square cm in a square meter). That's only 0.1778% of a square meter. Which is only 0.1778kw.

Their 6600kj device is powered by 0.1778kw of solar energy to give 3L in 12 hours.

>mfw

>>8887169
12 hours of direct over head sunlight good luck getting that consistently

>>8887209
Answer that's 100% gaseous water, not 100% humidity which is much much lower. Guess what happens at 100% humidity? It fuckin rains

>>8885558
If it's the one I'm thinking about, it was an entry into a contest sponsored by MIT. The students building it weren't MIT students.