New materials allow 2.8l/day of solar-powered desert water-vapor extraction


#1

Originally published at: http://boingboing.net/2017/04/14/metal-organic-frameworks.html


#2

Now that is pretty nifty. Be interesting to know what the downstream effects are of taking the water vapor out of the system that way.


#3


#4

I was thinking more:


#5

At 3 litres a shot, you aren’t going to make much difference. The need for sunlight to allow the MOF to release the water vapour sort of leaves it out-of-phase with most other passive collectors, though: they tend to work on the difference between higher absolute humidity during the day and lower dew point at night.


#6

Spoiled brats these days. I remember when living on a desert planet meant wearing a suit that distilled your bodily waste.


#7
I can't believe the  "Bad science" of saying the volume produced without stating the size of the substrate. Is that per 10 sq cm or 10 sq meters?

#8

This gives a rough idea…


#9

Per kg of MOF, according to the abstract.


#10

I can’t believe you formatted your post that way.


#11

That helps, but a solar technology should indicate it’s area needed.


#12

Phone glitch of some kind. No idea why. There’s some weirdness with the chrome.


#13

01d Sk001.


#14

I don’t know what you all are Tarkin about. I gots your Moff right here…


#15


#16

Okay, they aren’t trying to dump the waste heat of condensation into the ground, like Waterseer. That would be an automatic failure.

It looks like the waste heat is dumped into the air, through a radiator:

Still, isn’t that a Peltier cooler? So this is going to need a solar panel to power it, and will be limited by how fast the cooler can remove the heat from the condenser. (Magic zirconium or not, if that heat isn’t dumped elsewhere, it’s not going to work.) Too lazy to calculate the heat of condensation for 2.8l of water, efficiency of a Peltier cooler, to get the size of the solar panel required.


#17

From the abstract:

This device is capable of harvesting 2.8 liters of water per kilogram of MOF daily at relative humidity levels as low as 20%, and requires no additional input of energy.

“Capable” is a weasel-word. Do they mean “has been observed to” or “our theory predicts”?

As for “no additional input of energy”, hmm, removal of energy is the problem. The air passing through the radiator will be cooler than the inside of the box, true, and if they bake their super-sponge, then it might work.


#18

The area of adsorption is going to be determined pretty accurately by the weight of the material, as, in a porous material, most of the surface area is internal. This MOF uses IR to release the water vapour. I suspect, however, that the material is not going to require anywhere near the kind of energy levels needed to bridge the band gap in photovoltaic panels to release its water vapour, and will probably be much less sensitive to the area used to collect the energy source as a result. I can’t get the figures as the full article is behind a Science paywall, but, if they give a figure in kilograms in the abstract, I’m willing to bet that adsorption is the more critical factor. (Must check to see if there is an ArXiv preprint…)

For the condenser, however…


#19

Have to look at this later. As long as it isn’t a con job like Waterseer.


#20

In principle, it should work — the devil is in the details:

  • Can it get enough volume of air through their material in the night to collect the water, depending on the wind?
  • Can it collect enough heat during the day to free the water from their MOF material as vapor?
  • Can it dissipate enough heat to keep the condenser below the dew point of the inside of the box/oven?
  • How long does their MOF material last until it needs to be replaced?

This system does have an advantage over a regular dehumidifier in that it’s not wasting energy chilling a lot of air below the normal dew point to extract the water.