[HN Gopher] Harvester pulls 1.5 gallons of drinking water from a...
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Harvester pulls 1.5 gallons of drinking water from arid air per day
Author : Brajeshwar
Score : 85 points
Date : 2024-07-05 15:31 UTC (7 hours ago)
(HTM) web link (newatlas.com)
(TXT) w3m dump (newatlas.com)
| mistrial9 wrote:
| I saw a video demonstration of this product in a science context.
| Incredible to see it working completely passively, and also a
| different model with low electrical load assist.
| sparrish wrote:
| This one requires the material to be heated to 363degF 24 times
| a day to wring out the 1.5gal of water. That's a lot of energy
| spent for very little water.
| mistrial9 wrote:
| there is a completely passive device capable of deriving
| water from the air in a desert, without any electrical
| inputs, in the demo I saw. It is based on molecular-level
| action in engineered tube materials.. like a honeycomb but
| with chemical properties at a very small size, repeated in
| long stretches like cloth.
| jzemeocala wrote:
| Molecular seive or nanotubes?
| nashashmi wrote:
| Ironic. Uses heat to harvest water.
| falcor84 wrote:
| Why do you consider that ironic?
| bonzini wrote:
| Probably because vapor in the atmosphere condenses more
| easily as temperature goes down.
| falcor84 wrote:
| But even then, in what sense does it go against
| expectations?
| nashashmi wrote:
| Normally, vapors condense and cool and release heat. This
| uses heat to cause condensation.
| Aloisius wrote:
| The heat is for desorption, not condensation. After the
| water vapor is desorbed from the adsorbent, it's cooled
| in a condenser.
| engineer_22 wrote:
| The news article is a little light on details. Link to the
| original research below:
|
| https://pubs.acs.org/doi/10.1021/acsenergylett.4c01061
|
| Of note - the paper describes the theory and construction of a
| benchtop proof of concept. This has not been deployed at scale.
| Also of note, this is not entirely passive, requiring energy
| input to achieve a yield.
| devin wrote:
| Anyone know of DIY plans for this kind of thing?
| mistrial9 wrote:
| heavily patented materials science in the core - scaling their
| products in various ways is certainly discussed
| konfusinomicon wrote:
| I saw one recently where they used something that looked like
| very fine plastic filament fishnets layered on each other in
| this large cornucopia looking tower. I think they were
| capturing the mist as it came on and off a desert mountain side
| seventyone wrote:
| Yes, take two heat pumps in series and run one as AC and
| another as heat and you'll get far more than 1.5 gallons of
| drinking water out of arid air than this
| geor9e wrote:
| Any dehumidifier will drip water as a byproduct, air
| conditioners included. A friend has a tubes from her AC going
| to her carnivorous plants which like the distilled water.
| ortusdux wrote:
| Full publication -
| https://pubs.acs.org/doi/10.1021/acsenergylett.4c01061
|
| > 11.15-22.81 kWh/L
|
| Are there any advantages over cooling condensation extractors?
| They seem to be in the 0.3-3.0 kWh/L range.
|
| https://us.watergen.com/technology/
|
| https://www.researchgate.net/figure/Liters-of-water-condensa...
|
| https://www.ostfalia.de/cms/en/pws/turtur/solar-projects/con...
| cogman10 wrote:
| Sources of heat tend to be more available than sources of cold.
| You could theoretically marry the two, using the waste heat
| from the condenser to extract water.
| audunw wrote:
| > The potential downside is that this system requires energy to
| release the water - the base of the device needs to reach 184
| degC
|
| There are heat pumps that can go up to 200degC now, and if it's
| already a hot environment I imagine they could be fairly
| efficient. The "cold" side could be connected to some black
| panels facing the sun.
|
| But this would require a facility on an industrial scale so not
| something for a single home. Maybe a small village.
| blfr wrote:
| > Scaled up, that's 5.8 L (1.5 gal) per kilogram (2.2 lb) of
| material used per day, which is enough to satisfy several
| people's daily water needs.
|
| No knock on the device itself but this is barely enough for two
| people, especially in arid conditions.
| balls187 wrote:
| I think it's regarding daily drinking needs, and not other uses
| for water.
|
| The metric I am familiar with is the average person should
| consume 8 cups of water a day, so 1.5gal of drinkable water
| would support that need.
| complaintdept wrote:
| > So how much fluid does the average, healthy adult living in
| a temperate climate need? The U.S. National Academies of
| Sciences, Engineering, and Medicine determined that an
| adequate daily fluid intake is:
|
| > About 15.5 cups (3.7 liters) of fluids a day for men
|
| > About 11.5 cups (2.7 liters) of fluids a day for women
|
| > These recommendations cover fluids from water, other
| beverages and food. About 20% of daily fluid intake usually
| comes from food and the rest from drinks.
|
| https://www.mayoclinic.org/healthy-lifestyle/nutrition-
| and-h...
|
| (Of course you can _survive_ on less, but it 's not ideal. A
| quick test to see if you're hydrated enough is to go pee. It
| should have the slightest tint of yellow to it. If it's clear
| you're drinking more than you need. source: first aid class I
| took)
| balls187 wrote:
| The article doesn't say drink 11-15cups of water a day.
| yial wrote:
| It says 20% comes from food, (which depends on what you
| eat, right?)
|
| But taking it literally it would then say to drink;
|
| 12.4 cups for men. 9.2 for women.
| whiddershins wrote:
| Despite what common belief might indicate, coffee-soda-
| beer etc all count.
|
| But yes, if you are self supporting you would need water
| to make those things at home so the problem doesn't
| change much.
| bdcravens wrote:
| They count, just not ounce-for-ounce.
| balls187 wrote:
| The numeric recommendation is "fluid" which includes
| water, food, and water included in _other_ beverages.
|
| It may seem like splitting hairs, but the OP's comment
| was regarding 1.5Gal of water not being enough for a
| single person. Using the 8-cups of water a day, 1.5gal of
| water does meet that requirement.
| brianwawok wrote:
| The 8 cups thing is pure tabloid science, like red wine is
| good for your hear, or getting 10k steps a day makes you more
| healthy. It's not actually based in facts.
| krisoft wrote:
| I believe here it is used as a rough estimate of the
| drinking water needs of a human, and as such it is fine?
| The problem is when people take it as an exact number they
| must drink every day or else...
| hinkley wrote:
| They also backpedaled and allowed that your first cup of
| coffee or tea in a day counts as one of those beverages.
| I think beyond that the diuretic effect cancels out some
| of the fluids.
|
| If your pee is clear stop drinking. That's how I
| rehydrate after a workout. That's how a lot of actually
| healthy people do. Over time I'm growing more fond of the
| habit of calling people who aim for the trappings of a
| discipline without following it as cosplayers or LARPers.
| The people carrying the quart bottle of water are
| LARPing.
| rurp wrote:
| This seems weirdly hostile to drinking water. Some people
| like drinking throughout the day and/or feel better when
| they are well hydrated. Drinking enough water is one of
| the easiest healthy habits to pick up and stick with; it
| takes way less effort than exercising or learning to cook
| healthier meals.
|
| > If your pee is clear stop drinking.
|
| Why? A person has to drink a _lot_ of water for it to be
| a problem, far more than someone out and about with a
| bottle is going to consume. More water probably won 't
| help anything if your pee is already clear, but it won't
| hurt anything either and most people drink too little
| water as it is.
|
| Getting mad a people for carrying a water bottle around
| just seems weird. Depending on the area, it's not always
| easy to get a drink any time you want one. I guess if
| people are bragging about how hydrated they are it would
| be annoying. Bragging about how healthy your habits are
| is douchey in any context, but I've literally never seen
| someone act like that because they drink enough water.
| kimixa wrote:
| I read that the other way from the parent - in that you
| should _keep_ drinking until your pee is clear. Then you
| 're back to "normal" after a dehydrating event (the
| workout), so you can continue maintaining that level as
| normal.
|
| And I agree that "constantly carrying the bottle" has
| become as much about the fashion as anything - there's a
| guy at work who _always_ has a metal bottle on him,
| taking it _everywhere_. But they rarely use it - they 've
| never refilled it at work, and less than 1l (I've never
| seen it less than half full, but assuming it is used over
| the day) over 1/3 of the day doesn't feel like theyre
| _over_ hydrating.
| kragen wrote:
| most people don't drink too little water; you're
| reasoning from a false premise there
|
| if you do develop this habit, your kidneys adapt by
| eliminating water faster. this is usually not dangerous
| in today's world, but it's inconvenient to need to carry
| around a water bottle and frequently find a bathroom.
| occasionally it can lead to mild dehydration if your
| access to water is interrupted for a few hours
|
| also, inevitably, you do lose some salts with all that
| urine, which you have to replace, so drinking too much
| water mildly increases the risk of, in particular,
| hypomagnesemia (hypocalcemia and hypokalemia are much
| rarer, and you _really_ have to be pounding the water
| bottle to get hyponatremia; on the plus side, you don 't
| have to worry about being in acute hyponatremia for more
| than a few hours). these are a little more dangerous for
| the type of food faddist who believes things like
| 'drinking more water is good for you' because they're
| disproportionately likely to also believe that salt is
| bad for you
|
| drinking extra water can be really dangerous for people
| with renal insufficiency, because they _can_ get
| hyponatremia from fairly mild overdoses of water, but
| generally they 're already aware of this problem if they
| have any access to proper health care at all
|
| so basically it's an addictive habit with mild negative
| health consequences, similar to eating a low-fat diet,
| drinking coca-cola, or injecting heroin
|
| under unusual conditions, like going to the black rock
| desert, continuing to drink when your pee is already
| clear is actually a good idea, because then you actually
| can get dehydrated without any urge to drink. but you
| should probably be drinking stuff with salt in it, like
| gatorade, though homemade oral rehydration solution is
| enormously cheaper
| EasyMark wrote:
| I think people get tired of being harassed about drinking
| water like you're constantly in danger of falling over
| from dehydration. It's not bad per se to drink more water
| than you need as it does help the kidneys flush the
| garbage out of your system. I think drinking when you're
| thirsty and having meals is fine. Most food has a ton of
| water in it as well.
| insane_dreamer wrote:
| better to over-hydrate than under-hydrate
| blooalien wrote:
| Both can pretty easily do you _serious_ harm if taken too
| far, up to and including death. Thankfully the survivable
| "buffer space" of "too far" is large enough that people
| generally _pretty rarely_ ever get to the actual danger
| zone.
|
| Here's one fairly famous(ish) example of over-hydration
| being fatal: https://www.nbcnews.com/id/wbna16614865
| EasyMark wrote:
| Studies have shown that less that 400mg of caffeine a day
| is fine for a healthy adult. Just watch drinks it after 4
| or so unless you like it affecting your sleeping pattern.
| xnx wrote:
| In a dry climate it is very reasonable to calculate 2
| liters of water (~8 cups) lost through respiration and
| perspiration. If this water isn't being replaced by food or
| drink, that's trouble.
| https://www.ncbi.nlm.nih.gov/books/NBK236237/
| Symmetry wrote:
| There was one study back in the 1940s(?) that justified it.
| The researchers who did the study intended it to include
| water that was in the food a person consumed but the person
| doing the press conference didn't know that and so
| responded incorrectly when some reporters asked him about
| that issue.
| insane_dreamer wrote:
| > tabloid science, like red wine is good for your heart
|
| please don't burst my bubble
| EasyMark wrote:
| Many studies have shown that even 5000 steps a day can be
| associated with considerable better health outcomes than
| those who sit at a desk all day and work remote and get
| maybe 1000. Personally that's my baseline and I take a walk
| like that every morning before I shower for the day. I do
| some mild strength training a few times a week and walk and
| that's about it, and I can usually keep up with my homies
| when the occasional group hike or basketball game comes up.
| My doctor seems happy with my annual exams and bloodwork
| dn3500 wrote:
| My family uses about 20 liters a week per person. That's for
| drinking and cooking.
| treflop wrote:
| I suppose if I'm doing nothing, I'll drink 8 cups in a day.
|
| But most days when I'm out and about, I'm drinking about a
| gallon. And if it's hot, it's more.
|
| There was a short and dumb period where I started buying
| plastic waste bottles and I was blowing through like 6-8
| plastic bottles per day.
| michpoch wrote:
| > I'm drinking about a gallon. And if it's hot, it's more.
|
| Can I ask how tall / heavy are you? Gallon is almost 4
| litres of water, I can hardly imagine anyone being able to
| drink more in a day, and even that sounds like a lot.
| erikaww wrote:
| On hot days, I'll drink nearly two gallons. Most days 1.5
| gallons. Just water. I have a very large cup that is a
| pint and a cup. I'll drink 8-10 of those a day. Though I
| eat a lot of salty/dry foods. America baby. If I go for a
| long bike ride I'll be able to wring my shirt/sweatshirt
| and sweat will come pouring out.
|
| After a long ride I'll drink nearly half a gallon of
| water. Likely excessive but it tastes really good.
|
| It's likely there is a very large variation in the water
| people need to consume. During college, I knew
| individuals that would drink merely a glass or two all
| day (minus before/after going to the library). Very small
| water bottles. Though these individuals looked to be <100
| lbs.
| EasyMark wrote:
| I think you're talking to someone who is very serious
| about water consumption. Most people do not need a gallon
| a day. Not even close. While there is nothing wrong with
| it, we are not nearly as dehydrated a nation as the local
| news station seems to claim every 6 weeks or so or
| r/hydrohomies
| treflop wrote:
| 6' 165lbs
|
| I remember drinking half of a 1 gallon plastic water jug
| in an hour changing a tire in the middle of a desert when
| it was 110degF.
| kleiba wrote:
| The usual recommendation around here is to consume around 3l
| of water per day just to stay hydrated, i.e., not for hygiene
| or other uses.
| Mountain_Skies wrote:
| Finally, thunderf00t has something new to make a video about that
| isn't beating a dead horse.
| fourteenfour wrote:
| Haha, I enjoy thunder's spirit, but his vids are so drawn out
| and repetitive that it makes them hard to watch.
| throwfkk wrote:
| It's Hacker News. Most of the people here are lot smarter than
| him.
| upon_drumhead wrote:
| > in air with 30% humidity (classed as arid)
|
| TIL my house is arid
| brianwawok wrote:
| Most wood products, thinking my floors and my actual made of
| wood dressers, want 35-55% humidity year round. For me I have
| to add back humidity in the winter, and take away with humidity
| in the summer.
| fred_is_fred wrote:
| We had these on my uncle's farm. They are finicky especially in
| dry environments with lots of sunshine. Robots can assist with
| the repairs and programming. They can be difficult to find second
| hand, but if they can program a load lifter they can probably do
| it.
| htrp wrote:
| I think you had the moisture vaporators, not these harvesters.
| galangalalgol wrote:
| To keep them yp and running do you need power converters?
| fred_is_fred wrote:
| That was mainly just something my friends and I messed around
| with, but primarily it was an excuse to get to Tashi Station
| - so much cool stuff there.
| hiddencost wrote:
| I'm sorry for your loss.
| fred_is_fred wrote:
| Thanks - it's been a rough few years. Lost my aunt and uncle,
| my dad, and pretty much all my other relatives except for my
| sister. I've tried dealing the anger in healthy ways but
| despite my calm outer demeanor, I am quite angry and
| generally wearing all black these days.
| ozim wrote:
| Totally relate, I also hate the sand it gets everywhere.
| pimlottc wrote:
| I didn't realize you had a sister!
| jzemeocala wrote:
| I bet you and your sister have a "close" relationship.
| jzemeocala wrote:
| Tell me your Luke Skywalker without saying your Luke Skywalker
| Someone wrote:
| FTA: _"The potential downside is that this system requires energy
| to release the water - the base of the device needs to reach 184
| degC (363 degF) to wring it out. But the team says the device can
| tap into waste energy or heat from other systems, like buildings
| or vehicles."_
|
| I guess it's fairly hard to get 184degC of heat out of buildings.
| Getting it out of ICE vehicles is easier, but the device will add
| weight to the vehicle, and those are on the way out (slowly).
|
| So, that leaves getting it out of waste energy such as excess
| solar or wind energy. If that's your heat source, an important
| metric is "how many Watt hours per liter"
|
| I skimmed the paper. AFAICT, it only mentions usage of current
| state of the art devices, at 11 to 23 kWh/l, compared to 5 to 7
| kWh/l for conventional passive systems.
|
| What did I overlook?
| sandworm101 wrote:
| Getting 184c out of a typical car engine won't be easy. You
| might use exhaust gas but that would be difficult to regulate
| and seems wasteful. But if you have a car engine then you have
| a fuel source. Getting 184c out of a gasoline flame is dead
| simple.
| bee_rider wrote:
| What humidity levels do the conventional passive systems work
| at?
|
| In regions where there's excess solar energy and insufficient
| humidity, the tradeoff seems maybe worth it?
|
| Excess solar energy brings to mind stuff like putting it
| through solar panels, which can be limiting. But if we just
| need to convert photons to phonons, no need to stop by in
| electron-vill, a big dumb array of mirrors could do it, right?
| datameta wrote:
| Yeah, no need to do sunlight->electricity->thermal as mirrors
| would be much more efficient.
| datameta wrote:
| Hmm, desert sand can typically reach 150-200F, so there's a
| start.
| nomel wrote:
| And a couple of mirrors can double it.
| rs999gti wrote:
| > The potential downside is that this system requires energy to
| release the water
|
| Damn you physics!
| ramesh31 wrote:
| >11.15-22.81 kWh/L
|
| Goodness that's a lot of energy to generate a liter of water.
| mensetmanusman wrote:
| Just a hint at the crazy amount of power available from the sun
| we take advantage of without knowing.
| MR4D wrote:
| So, somewhere in the area of a Tesla battery at full charge to
| get a gallon (+/-) of water.
| itake wrote:
| If this is deployed at scale, I wonder how this would impact the
| plants and animals that depend on that water.
| crazygringo wrote:
| In absolutely no way whatsoever.
|
| First of all, the proportion of water from the atmosphere would
| be absolutely minuscule.
|
| But second, people drink the water and then breathe the
| moisture back into the air, or pee it and it winds up back in
| the water cycle.
| 101011 wrote:
| I'm not saying one way or the other, but "minuscule" varies
| on the scale and just because there's a closed loop cycle
| doesn't mean there's not a local impact to removing water
| from the area.
| hinkley wrote:
| Local being your neighbors downwind.
| cogman10 wrote:
| > But second, people drink the water and then breathe the
| moisture back into the air, or pee it and it winds up back in
| the water cycle.
|
| Not for nothing, but in really arid locations (like las vegas
| for example) human consumed water is fairly well captured.
| The water cycle ends up looking like a series of plumbing
| turning piss into potable water.
| hinkley wrote:
| If your condensers drain into the sewer system, and its so
| hot outside that people are obliged to stay indoors... yeah
| for the part of the year where water matters the most I
| could see what you're saying being true.
| hinkley wrote:
| This is the same sort of thinking that leads people to say,
| "how can we be so arrogant as to think that humans could ever
| have enough power to change the climate?"
| wavemode wrote:
| That is an exceptionally uncharitable reading of his
| comment.
| masayune wrote:
| I'm glad my peeing into the wind is helping the circle of
| life
| whitehexagon wrote:
| Hmm, This has got me wondering if I could use my daily ~4kWh
| spare solar energy for watering my dozen chilli plants, maybe
| something like a dehumidifier running outdoors. It is hot here,
| and in recent years has some higher humidity in summers. I'm
| guessing the extracted water is ok for plants?
| Marsymars wrote:
| Well, doing some math, energy efficient dehumidifiers look to
| be around 2 L/kWh for midrange RH numbers. (Which is _much_
| better than the systems in the article.) So you could get maybe
| 8L per day.
|
| Probably doesn't compare very well to rain water storage. A
| standard blue barrel will store 250L, or about a month's worth
| of solar dehumidifier production. Can do some more math on roof
| surface area and rainfall to work out barrel requirements.
|
| Is also not economically great - e.g. at $0.20/kWh your
| electricity is worth about $1.6, but in my municipality 8L of
| water is worth under $0.03.
| whitehexagon wrote:
| Valid good points, but it doesnt rain most of the year, and
| it would cost me to be grid connected. Connection fee, taxes,
| hidden taxes, and they dont pay for excess above what you use
| over the year. Hence off grid with some batteries and spare
| capacity.
|
| I saw a unit for 149e that claims to extract 12l/day, only
| 210W, compressor based, but you are right of course,
| equivalent water is a couple cents a day! quite some time for
| ROI. Probably solving drinking water, which is currently a
| supermarket run for bottles would be a better investment.
| racl101 wrote:
| This is the kind of thing we should be putting a lot of resources
| in figuring out.
| dsego wrote:
| Nothing to figure out, not feasible just by simple basic
| physics. These types of machines have been busted to death.
| Sort of like investing resources into harnessing perpetual
| motion.
| rcarmo wrote:
| I am happy to see that we are ensuring the Fremen will have the
| technology they need to survive on Arrakis.
| edm0nd wrote:
| The spice must flow!
| rcarmo wrote:
| Of course, we are almost on the cusp of the Butlerian Jihad
| :)
| motionthings wrote:
| Another dehumidifier from MIT Thunderf00t is going to have a
| field day
| kragen wrote:
| the copper foam is a really nice idea. for those not familiar
| with the problem space, the issue is that when you condense water
| with an adsorbent or other desiccant, it releases a lot of heat,
| which limits how fast you can condense water: quickly enough your
| hot desiccant is in equilibrium with the air until you remove
| some of that heat
|
| nrel did a record-breaking design in the last couple of years
| with i think calcium chloride on aluminum fins, optimized to
| provide air conditioning (cooling) rather than water harvesting.
| if you're interested in this news item you might want to look
| that up, i don't think i saved the link
|
| (how do they keep the chloride from eating the aluminum? i don't
| know, maybe i'm misremembering. zeolite avoids that problem)
|
| my own thought is that you ought to be able to rapidly blow the
| air through a closed loop consisting of a recuperator and the
| desiccant, thus allowing it to reach the desiccant's
| deliquescence humidity at the temperature of the temperature
| reservoir the recuperator interchanges heat with, rather than at
| the brine-bulb temperature of the desiccant (zeolite doesn't form
| a brine or have a deliquescence humidity but the principle is the
| same). this will surely have a lot more frictional losses than
| simple passive conduction through copper or aluminum, but on the
| other hand, it's a lot easier to fabricate
|
| in my proposal, once you've reached the desired low humidity
| inside the closed loop, you open it up and pump your charge of
| cool, dry air into the place you want cool, dry air, and then
| begin the desiccant regeneration process with new air circulated
| in the same way, but passed through a heat source
|
| a somewhat more elaborate version of the system uses a series of
| heat reservoirs at different temperatures to recover about two
| thirds of the heat rejected at the first recuperator, using it to
| heat the regeneration air
|
| but who knows, i haven't built a prototype yet, and my grasp of
| thermodynamics and psychrometrics is shaky at best; maybe the
| idea is flawed in some way i haven't figured out
| m463 wrote:
| I've always wondered about these sorts of things.
|
| Do they actually make "drinkable water"? If it is distilled
| water, it is not drinkable, it is dangerous and will leach
| necessary minerals out of your body.
| dyauspitr wrote:
| Distilled water is very drinkable for a long time. You just
| need to make sure you get the minerals from other sources which
| are readily available in deserts. For instance in Kuwait that
| relies 100% on desalination plants for its water supply, they
| mix in 10% sea/brackish water to replenish the minerals.
| Am4TIfIsER0ppos wrote:
| Is is a dehumidifier? Fins, requires energy, some part gets hot.
| Yep its a dehumidifier. Dry areas are dry because there is no
| humidity to condense and fall as rain.
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(page generated 2024-07-05 23:01 UTC)