MOF’s sound like normal dehumidifier with extra steps. The way I see it and from what I understand from reading this.
Put MOF outside so it absorbs water from air.
Heat MOF up to boiling( 100C) to get the water out. ( as something lime squeezing it would probably destroy it, though would be cool)
Cool the water vapor back down using normal dehumidifier means.
Why spend the energy to heat the MOF up. Just cool the air down using normal dehumidifier means. It take a ton of energy to heat water up.
Hi_ImSomeone@lemmy.world 2 days ago
MOF behaves like a sponge, but wouldn’t feel like a sponge. Squeezing it would be nice, and could definitely eliminate the hassle of having to heat it up.
As for the energy, the thermodynamics of dehumidification basically requires an external energy source. To cool the air, you have to have a heat engine which removes the active ambient thermal energy out of a system. Such a system would look like a traditional dehumidifier hooked up to solar panels. The issue with that is the associated capital expenditure costs to build up such a system, as that already costs significantly more than “some random metal sponge” (assuming we could make it at scale).
For now, the only ways to cool the air down would be to use traditional refrigeration techniques, or peltier coolers. Peltier coolers are super inefficient, and traditional heat pumps require alot of energy. When in a low humidity environment, the coefficient of performance for heat pumps goes way down because the outdoor temperature could be very high, and the humidity very low. To reduce the air temperature to below dew point would mean cooling the air to near 0c, which is pretty much putting a freezer in a desert.
Solar energy is free, but absorbing it and converting it into useful work takes a good bit of engineering effort to make happen. What MOFs and similar materials can take advantage is being able to be left out in the sun like a sun dried tomato and covered in a black painted cover. Couldn’t be simpler!
zephiriz@lemmy.ml 2 days ago
Now from this it sounds like a fancy dew collector with extra steps.
Why most certainly there is some niche uses for it and every situation is different. I highly doubt it has a real would massive scale use and when people promise the world( like pulling drinking water out of air) I think they are nothing more than a pipedream.
I stand by a post I made here elsewhere. It would be cheeper to load up a truck with water and move it to where you need it, or better yet build a pipeline. MOF while, like I have their uses, we already have very efficient ways yo clean and move water and no supper SciFi techno babal will replace what we already use. It the same thing as data centers in space.
Hi_ImSomeone@lemmy.world 1 day ago
Actually, this isn’t quite as simple as a dew catcher. For MOFs specifically, there’s a fundamental physical chemistry principle going into it which is able to capture the water. At the molecular level, the MOF structures are super porous, which allows the water in the air to become trapped inside. The difference between that and dew catchers is dew catchers aren’t able to actually harvest gasseous H2O. They only harvest what is able to be deposited in liquid form. Water from air technology is a real thing, and there are at least decades of research on it.
You may have some experience with a slightly different form of vapor harvester, silica gel packets! Those use a chemical based methodology to bond with water molecules in the air instead. There are two major difference between those and MOFs is that MOFs are reusable, and silica gels are not quite reusable. The other difference is in the holding capacity of MOFs. They can hold significantly more water than silica based gels.
The economics of the emerging MOF field is definitely uncompetitive in it’s current form. The current price to performance ratio isn’t something that can currently compete with existing technologies, whether it is trucking water, or desalination. The industry knows this, and knows it must get the price down to competitive levels. However the reason why it is nobel prize winning this time is that now the performance is in a ballpark where it could be commercially viable. It would be more environmentally friendly to setup some solar water harvesters one time, rather than to be constantly trucking or piping in water from elsewhere. Extremely remote communities would be more self reliant if they don’t have to be paying exorbitant amounts of money each time for new water delivery.
zephiriz@lemmy.ml 1 day ago
I still think it’s a pipedream. The energy needed vs what you get in return doesn’t add up for me.
I would imagin they are similar to molecular sieves. They are very porous and that’s how they trap the water. If it was easy to get out then it wouldnt trap water very well. To pull that water back out you have to really heat it up to force it to find its way out like a maze. If you where to say used black plastic, I have doubts you could get anywhere near boiling so it might be free an easy you wouldn’t be putting enough energy in to get enough water out. So you would need an external power source. No matter where (magic solar panels).
If your going to use an external power source might as well use it to put a pump on a pipe and I would guess move an infinite more amount of water for the power used.
While trucking water would be expensive. I would imagen these would be even more so. You have to buy them move them set them up and im sure do some sort of maintains. And if you want a long term solution look no further than Las Vegas. Where a big pipe is cheap and easy, well compared to what I would imaging what this would cost at the same scale.
Also to my understanding many places do have some form of water but its not safe to drink. I would rather spend the money on a filter/ purification system of water than try to pull it out of the air that would still probably need to be filtered, dust is crazy.