Probably makes sense in a smaller scale “let’s replace our water coolers because water is scarce but we have enough energy” scenario like South Africa.
In the summer, certain parts of the Bay Area still has high humidity levels without rain for months on end.
Some basic napkin math says at normal temp and humidity that is roughly 84 cubic miles of air you'd need to reduce to 0% humidity. Assuming the process isn't instant, you couldn't contain that volume of air in a structure humans know how to build. You'd also have to build massive air inlet pipes going 5 miles in each direction just to be able to circulate it into the machinery.
Edit: the comment I replied to was talking about areas with "humidity but not rain." I was just pointing out trying to replace rain is an insurmountable problem. You can do all sorts of things to optimize water usage, but that isn't the point. I picked San Francisco because it is a scale most people on HN can understand, but it is still tiny compared to farmland in the central valley.
1) for the whole city when these things are usually intended for households (and cities have many miles of pipes anyway.)
2) without mention of the rate of water extraction or energy use per liter which is usually what makes these obviously useless.
You just need enough for the water that ends in taps or in the garden/farm.
I'm not saying this is preferred over desal, water recycling, or other water conservation/generation possibilities.
This brings back my summer Berlin memories. The temperatures are pushing 40, the air is so thick you feel like in Amazon rainforest. But no rain in sight.
Honestly I think it would be nice to have a magic drinking water creator, but wouldn't it be distilled water? (which isn't good for you, depleting minerals)
That's a $100 premium which values the "fog" water at roughly $500 / gallon. So if you have a market willing to pay $500 / gallon extra for water harvested from the air this business might work. Not sure how many of those there are.
This will often be more expensive than having a truck bring the water to you when running a dehumidifier especially when you are looking to get out enough for farming.
Why?
I have seen how gross dehumidifiers can be. But they are designed to dehumidify, not to provide drinking water. What is preventing one from purifying the water and keeping it that way?
[0] https://edition.cnn.com/2016/11/18/africa/fog-catchers-moroc...
[1] - https://www.amazon.com/NUBE-Generator-Ecological-Sustainable...
[2] - https://suntowater.com/
[3] - https://islandsky.com/products/
[4] - https://www.youtube.com/watch?v=yL3Ps86N2nM
There are states in India for example that get 2000+ mm of rain every year and still have severe water shortages.
Areas which get 2000+ mm of rainfall a year aren't always the ones with the most intensive agriculture. Water shortages are partly because of (a) the huge variation in the amount of rainfall from year-to-year in any area in India, and this variation has grown with climate change/warming (b) rivers down in the south of the country are not perennial but largely rain-fed during the monsoon. So "build more dams/infrastructure" doesn't make sense if there's not much rain to feed the rivers, (c) certain crops grown (sugarcane,paddy) just require tons of water, and are more likely to face issues due to variable rainfall compared to something like millet cultivation (d) rain is required not just for flow into rivers but for recharging groundwater, which is then used for agriculture. So, no rain = no groundwater and not just no rain = less flow in rivers.
> huge amounts of energy
Condensation doesn't require energy. The energy mentioned in the article seems to be releasing the water from the hydrogel, but in my off-the-top-of-the-head metal funnel example a sufficiently steep big metal funnel can collect the water without any mechanical energy at all.
> Any such scheme isn't reliable in any case, and especially unreliable when things are dry and you really need the water. It works best precisely when you don't need it.
Water is stored easily enough, as long as you keep a surplus on hand for dry spells I don't see the problem?
EDIT: I am curious why my post is being downvoted. This doesn't seem particularly controversial.
Hot air can hold a lot of moisture, cold air can hold less. Water condenses on surfaces when the air cools down to the point that air would have to carry more water than it can at the new temperature.
Problem with that: it only works great in very humid areas. If you're in a desert, and have 10% humidity, you have to cool down your air by a lot for it to become too saturated and condensation to happen. Not enough cooling, and the moisture stays in the air.
Deserts tend to have pretty wild temperature swings. They usually cool down at night. So much so that in most cases you can make ice. You can use the sky as a heat sink (effectively radiating heat into space).
https://www.fieldstudyoftheworld.com/persian-ice-house-how-m...
* If you have high humidity, you almost always have plentiful rain and water around.
* If you're in a desert, then there's extremely little for any device to work with.
* It takes absolutely enormous amounts of air to extract meaningful amounts of water even in favorable conditions. * It takes a huge amount of energy, too.
* Any such scheme isn't reliable in any case, and especially unreliable when things are dry and you really need the water. It works best precisely when you don't need it.
* You don't want to drink water from any kind of dehumidifier. It may have started clean, but won't stay that way.