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Check out Thunderf00t's videos cricising solar water collectors, e.g.: - https://www.youtube.com/watch?v=vc7WqVMCABg https://www.youtube.com/watch?v=vc7WqVMCAB

Check out Thunderf00t's videos cricising solar water collectors, e.g.: - https://www.youtube.com/watch?v=vc7WqVMCABg https://www.youtube.com/watch?v=vc7WqVMCABg - Zero Mass Water: BUSTED! "Honestly, it drives me crazy how many people have reinvented the dehumidifier, put a solar panel on it, and the media has danced around like theyve just saved the world!" - https://www.youtube.com/watch?v=aPvXnmBIO7o https://www.youtube.com/watch?v=aPvXnmBIO7o - Self-filling water bottle: BUSTED! "The fact that its thermodynamically impossible seem to stop 'science communicators' from promoting this. The fact that its a really dumb, and not particularly inventive idea didnt stop the 'science communicators' from promoting this. Kinda depressing really." Problems include: - it's much cheaper to bring in a tanker of water from somewhere else, than for the electricity to do this. - It's a dehumidifier; in places where the air is wet, it rains, and you don't need it. In places where you need it, you need it because there's not much water, so it doesn't work well. - It's going to be prone to growing bacteria; warm and moist. - It needs a vast volume of air; when water becomes steam it expands 1000x. Which means to go the other way you need at least 1000 litres of steam dragged through for a litre of water. Air can be around 4% water says Britannica.com, so 20,000 litres of humid air for a litre of water if it's perfectly efficient. Thunderf00t's estimate is 50,000 litres of air for 1 litre of water; And the air needs to be cooled. That needs big fans and lots of power (air is heavy to move).

noogle 5y ago
> in places where the air is wet, it rains, and you don't need it. - Rain water collected in ponds/rivers may be contaminated/infested. - Lack of fresh water in the ocean/islands is also an issue. The two things that are available almost everywhere are air and sun.
- kragen 5y ago
  Rainwater cisterns are a viable option if you have rain.
  - RosanaAnaDana 5y ago
    And if you dont?
    - Untit1ed 5y ago
      Then you probably don't have humidity either, so the collector won't work.
      - Xylakant 5y ago
        There are many places that have fog, but no or little rain - the skeleton coast inwards/Namib desert in Namibia for example.
        kragen 5y ago
        There's a very interesting beetle there...
      - kragen 5y ago
        No, that's not true; it's just less efficient because you have to handle more air and cool it to a lower temperature. Air in Earth's atmosphere always has significant humidity. See https://news.ycombinator.com/item?id=30716765 https://news.ycombinator.com/item?id=30716765 for some calculations. It's reasonable to condense drinking/cooking water from air with solar energy in places that lack secure water. Not water for other purposes; you can't run a cooling tower, irrigate a field or an orchard, water a herd of cattle, or even grow a garden that way. But a household-sized dehumidifier powered by a household-sized solar panel can certainly make enough water to drink and cook rice. On the other hand, if you live in semi-arid desert or any wetter biome, a cistern probably has a better cost-benefit ratio. Depending on your aquifer, a well may be better still.
        kragen 5y ago
        It's worth pointing out that the sorbent-based systems in the H2E project don't work by cooling air below ambient temperature.
schmichael 5y ago
A commercial system is in use on the Warm Springs reservation in Oregon: https://www.opb.org/article/2021/08/10/warm-springs-leaders-back-high-tech-in-struggle-for-safe-drinking-water/ https://www.opb.org/article/2021/08/10/warm-springs-leaders-...
vesinisa 5y ago
Their paper is open access: https://www.nature.com/articles/s41586-021-03900-w https://www.nature.com/articles/s41586-021-03900-w They claim that this device with 1m² footprint could "well within thermodynamic limits" alleviate thirst for a billion people living in "tropical regions" (daytime relative humidity 30%-90%). I already look forward to the debunk. It all seems very high-level. My money is on that these regions where the device would be viable do not actually suffer of lack of access to drinking water to start with - not to the tune of a billion thirsty people at least.
- jodrellblank 5y ago
  > "I already look forward to the debunk." How about: Google found a way to alleviate thirst for a billion people and then decided it wasn't worth bothering with, stopped it being a project, and dumped the plans on Github? Norman Borlaug[1] won a Nobel Prize for his contribution to food production which is said to have fed a billion people, so I guess these authors had better things to do at Google than save a billion thirsty people and do Nobel level work? From the paper: "Our assessment introduces a hypothetical 1-metre-square device with a SY profile of 0.2 to 2.5 litres per kilowatt-hour". From the Thunderf00t video, checks out with a Google: it takes about 2,200,000 Joules of energy to evaporate 1 litre of water at 100C into steam at 100C, and so at least that much to condense 1 Litre of water from steam. There's 3.6MJ in 1KWh which is enough for 1.5 Litres. So already in the first paragraph of the abstract their upper estimate of 2.5 litres per KWh seems to be beyond thermodynamic limits (I could be very wrong, I'm no scientist; am I wrong?). I'm not claiming any expertise or more knowledge than watching two videos just now, but their paper describes more than just solar powered condensing, with absorbent gels and materials involved as well (but still, wouldn't those have to take the same amount of energy out of the air to condense the water?). Their paper also shows desalination as being >100x more water per KWh than getting water from air. [1] https://en.wikipedia.org/wiki/Norman_Borlaug https://en.wikipedia.org/wiki/Norman_Borlaug
csours 5y ago
I will never check out a Thunderfoot video. He is a hateful pitiful man.
- seanw444 5y ago
  He's generally not wrong. But I agree, his approach is pretty obnoxious.
  - Isamu 5y ago
    But aren’t the “debunkings” rather cursory and dismissive? Instead I think real engineering relies on tradeoffs, certain areas of a multidimensional space where an idea makes sense - and others where it doesn’t.
    - jodrellblank 5y ago
      Watch them and find out? He explains why it takes so much energy to boil and condense water, calculates out and explains how many Joules to condense a litre of water, how long that would take for various solar panel sizes, compares the solar-water-collector against mains powered dehumidifiers, compares the solar collectors against using the same size panel as a rainwater catcher in different environments, compares it against the price and time to get 10,000 litres of water in a tanker and drive it a thousand kilometers, talks about the product's claimed size, isntallation cost or use cases and how they don't make sense. I see his style is divisive, but I don't think they are cursory, at least the two I linked; he's clearly put hours of time into making them, it's not just him talking and laughing recorded in 20 minutes.
      - traverseda 5y ago
        This doesn't use solar electric though. It (mainly) uses direct solar heat. It also doesn't use any kind of peltier cooling. It's a largely passive device with a few minor electric components that won't draw much power. People using his "rather cursory and dismissive" debunking to debunk other very different technology is kind of annoying.
space_rock 5y ago
Thunderf00t is hit and miss. Some videos are scepticism, small mindedness, long pessimistic rant without substance and no debunking
- manigandham 5y ago
  Which debunking video was like that?
  - space_rock 5y ago
    "Veritasium: BUSTED!" https://www.youtube.com/watch?v=5Hyy1zRZPiQ https://www.youtube.com/watch?v=5Hyy1zRZPiQ This is his area of expertise and is a great "busting" video Trash: "Elon Musk Invents UNDERGROUND Traffic Jam!" "Tesla Bot" No debunking. Small mindedness, pessimistic rant. Just says Elon will fail but not clear how he knows he will fail
    - kisstheblade 5y ago
      He actually has outlined exactly what's wrong with these ideas. I mean the hyperloop was supposed to be "like an air hockey table", well guess what, musk now "advocates for wheels"... It's just a really bad and unworkable idea. The idea of 1000km long vacuum tubes is beyond stupid, when we already have high speed rail. Please tell me how stating these facts are "small minded" or "pessimistic". His main point is usually about the massive unwarranted hype and blind hero worship around these concepts, and usually scams (the water stuff and other kickstarter projects). The truth hurts, I guess.
      - space_rock 5y ago
        I never mentioned hyperloop. Again this is the level of reply I would expect of Thunderf00t. You can do better
        kisstheblade 5y ago
        This relates to hyperloop "Elon Musk Invents UNDERGROUND Traffic Jam!"
kragen 5y ago
Dehumidifiers aren't what's thermodynamically impossible, of course; Fontus was just making quantitative performance claims that were thermodynamically impossible about how small their system would be and how little energy it would use. You don't need to sink to citing YouTubers to figure out how much water air contains. You can just consult a standard psychrometric chart: https://commons.wikimedia.org/wiki/File:PsychrometricChart.SeaLevel.SI.svg https://commons.wikimedia.org/wiki/File:PsychrometricChart.S... You can see from that chart that at, for example, 20 degrees and 30% relative humidity (which, if you're not aware, is pretty dry), you have about 5 mg of water per gram of air, or about 5 grams of water per kg of air, which is about 0.8 cubic meters (1.2 g/liter). So if you want to produce 10 liters of water per day for your family, you need to run 2,000 cubic meters of air through your dehumidifier. (Or a bit more because you can't reduce it to 0% humidity.) That might sound like a lot, but it's per day, so it works out to 49 cfm, which is not "big fans and lots of power". If we're talking about a 300 mm square aperture it's 260 mm/s of airflow, a breeze you can barely feel, which requires a totally insignificant amount of power compared to the actual refrigeration involved. This is not going to fit nicely on your bicycle like in the fraudulent Fontus videos but it is entirely reasonable as a household appliance. Solar electricity is free if you aren't using it for something else. As for bacterial growth and filtering, yeah, that's a real design constraint, and it's one that HVAC systems have fallen down on in the past with disastrous results, but it's not some kind of unsolved engineering problem. Every air conditioner, sea voyage, and water tower deals with it. Here in Argentina just about every house has a rooftop drinking-water tank, where we control bacterial growth with chlorination, by impregnating the tank plastic with bacteriostatic agents, and by making the tanks opaque so algae can't grow. Thousands of years ago, mariners dealt with it by dropping a silver coin in each amphora of drinking water. It would be a more difficult problem if a dehumidifier were warm and moist, but actually it's cold and moist. As for the relative costs of tankers and electricity, well, that varies depending on where you are. Around here supply chains are so unreliable that I'd hate to rely on a weekly delivery from a water tanker in order to not die of thirst in 48 hours. (Fortunately, I live a few kilometers from the biggest river in the world. Water is not a problem here, though in places pollution is.)
- blkhawk 5y ago
  You also need power to take the heat away that is created when the water in the air turns into a liquid. Best case you need to cool for about 0.7kwh per litre of water you make. That means for your 10 litre example you need best case 7kwh. That is a decent sized solar array and if you have any inefficiencies in your heat pump setup it gets much worse. Also you assume per day - solar only works during the day so you need storage as well so your system can work during the night.
deleted 5y ago
[deleted]
ptrklly 5y ago
I don't have views on the credibility of specific technologies but I've hoped that these could be viable in places like coastal California where fog provides quite a bit of air moisture but it never rains--do you not agree with that?
- kragen 5y ago
  If you have fog or dew, you can just use a fog net: https://en.wikipedia.org/wiki/Fog_collection https://en.wikipedia.org/wiki/Fog_collection https://news.climate.columbia.edu/2011/03/07/the-fog-collectors-harvesting-water-from-thin-air/ https://news.climate.columbia.edu/2011/03/07/the-fog-collect... These are mentioned in Table 1 of the Nature article: https://www.nature.com/articles/s41586-021-03900-w.pdf https://www.nature.com/articles/s41586-021-03900-w.pdf In coastal California, redwood trees have been doing this since the Jurassic. In the conditions you describe, fog nets commonly yield 2–3 ℓ/m²/day of water (20–30 nm/second), though experimental projects have reached yields over 13 ℓ/m²/day (150 nm/s): https://www.oas.org/dsd/publications/unit/oea59e/ch12.htm https://www.oas.org/dsd/publications/unit/oea59e/ch12.htm Fog nets are easier to make and easier to repair, and consequently enormously cheaper. This makes them practical not only for drinking water but even for irrigation. They are more tolerant of damage, though they do need yearly maintenance. But they don't work on days without dew, and in some places, that's nearly all days.
WheelsAtLarge 5y ago
" It's a dehumidifier; in places where the air is wet, it rains, and you don't need it. In places where you need it, you need it because there's not much water, so it doesn't work well." I wonder how well it would work as a stand in for a desalination solution. Where there's all the water you want but it has salt (or other contaminant) that makes it impossible to drink. Seems to me that a beach would be the perfect place for it. At $150 price point it's a very good alternative to high price machinery.
- jodrellblank 5y ago
  Desalination produces a lot more water-per-KWh-energy than unboiling water from the atmosphere. Elsewhere in this thread someone linked a paper which estimates up to 100 litres per KWh for desalination, vs ~1 litre per KWh for condensing. Saving on machinery, or chemicals, might be important but $150 of materials for a device will buy you ~25,000 litres of water in bulk (in the USA).
jcranberry 5y ago
The linked nature paper points out that over a billion people without access to safe drinking water live in areas where their design would be high performance (tropical areas).
traverseda 5y ago
Very different technology, this is largely not solar-electric. It's solar-thermal with a bit of electric for a circulating fan and a small motor.

noogle 5y ago

> in places where the air is wet, it rains, and you don't need it. - Rain water collected in ponds/rivers may be contaminated/infested. - Lack of fresh water in the ocean/islands is also an issue. The two things that are available almost everywhere are air and sun.

kragen 5y ago
Rainwater cisterns are a viable option if you have rain.
- RosanaAnaDana 5y ago
  And if you dont?
  - Untit1ed 5y ago
    Then you probably don't have humidity either, so the collector won't work.
    - Xylakant 5y ago
      There are many places that have fog, but no or little rain - the skeleton coast inwards/Namib desert in Namibia for example.
      - kragen 5y ago
        There's a very interesting beetle there...
    - kragen 5y ago
      No, that's not true; it's just less efficient because you have to handle more air and cool it to a lower temperature. Air in Earth's atmosphere always has significant humidity. See https://news.ycombinator.com/item?id=30716765 https://news.ycombinator.com/item?id=30716765 for some calculations. It's reasonable to condense drinking/cooking water from air with solar energy in places that lack secure water. Not water for other purposes; you can't run a cooling tower, irrigate a field or an orchard, water a herd of cattle, or even grow a garden that way. But a household-sized dehumidifier powered by a household-sized solar panel can certainly make enough water to drink and cook rice. On the other hand, if you live in semi-arid desert or any wetter biome, a cistern probably has a better cost-benefit ratio. Depending on your aquifer, a well may be better still.
      - kragen 5y ago
        It's worth pointing out that the sorbent-based systems in the H2E project don't work by cooling air below ambient temperature.

schmichael 5y ago

A commercial system is in use on the Warm Springs reservation in Oregon: https://www.opb.org/article/2021/08/10/warm-springs-leaders-back-high-tech-in-struggle-for-safe-drinking-water/ https://www.opb.org/article/2021/08/10/warm-springs-leaders-...

vesinisa 5y ago

Their paper is open access: https://www.nature.com/articles/s41586-021-03900-w https://www.nature.com/articles/s41586-021-03900-w They claim that this device with 1m² footprint could "well within thermodynamic limits" alleviate thirst for a billion people living in "tropical regions" (daytime relative humidity 30%-90%). I already look forward to the debunk. It all seems very high-level. My money is on that these regions where the device would be viable do not actually suffer of lack of access to drinking water to start with - not to the tune of a billion thirsty people at least.

jodrellblank 5y ago
> "I already look forward to the debunk." How about: Google found a way to alleviate thirst for a billion people and then decided it wasn't worth bothering with, stopped it being a project, and dumped the plans on Github? Norman Borlaug[1] won a Nobel Prize for his contribution to food production which is said to have fed a billion people, so I guess these authors had better things to do at Google than save a billion thirsty people and do Nobel level work? From the paper: "Our assessment introduces a hypothetical 1-metre-square device with a SY profile of 0.2 to 2.5 litres per kilowatt-hour". From the Thunderf00t video, checks out with a Google: it takes about 2,200,000 Joules of energy to evaporate 1 litre of water at 100C into steam at 100C, and so at least that much to condense 1 Litre of water from steam. There's 3.6MJ in 1KWh which is enough for 1.5 Litres. So already in the first paragraph of the abstract their upper estimate of 2.5 litres per KWh seems to be beyond thermodynamic limits (I could be very wrong, I'm no scientist; am I wrong?). I'm not claiming any expertise or more knowledge than watching two videos just now, but their paper describes more than just solar powered condensing, with absorbent gels and materials involved as well (but still, wouldn't those have to take the same amount of energy out of the air to condense the water?). Their paper also shows desalination as being >100x more water per KWh than getting water from air. [1] https://en.wikipedia.org/wiki/Norman_Borlaug https://en.wikipedia.org/wiki/Norman_Borlaug

csours 5y ago

I will never check out a Thunderfoot video. He is a hateful pitiful man.

seanw444 5y ago
He's generally not wrong. But I agree, his approach is pretty obnoxious.
- Isamu 5y ago
  But aren’t the “debunkings” rather cursory and dismissive? Instead I think real engineering relies on tradeoffs, certain areas of a multidimensional space where an idea makes sense - and others where it doesn’t.
  - jodrellblank 5y ago
    Watch them and find out? He explains why it takes so much energy to boil and condense water, calculates out and explains how many Joules to condense a litre of water, how long that would take for various solar panel sizes, compares the solar-water-collector against mains powered dehumidifiers, compares the solar collectors against using the same size panel as a rainwater catcher in different environments, compares it against the price and time to get 10,000 litres of water in a tanker and drive it a thousand kilometers, talks about the product's claimed size, isntallation cost or use cases and how they don't make sense. I see his style is divisive, but I don't think they are cursory, at least the two I linked; he's clearly put hours of time into making them, it's not just him talking and laughing recorded in 20 minutes.
    - traverseda 5y ago
      This doesn't use solar electric though. It (mainly) uses direct solar heat. It also doesn't use any kind of peltier cooling. It's a largely passive device with a few minor electric components that won't draw much power. People using his "rather cursory and dismissive" debunking to debunk other very different technology is kind of annoying.

space_rock 5y ago

Thunderf00t is hit and miss. Some videos are scepticism, small mindedness, long pessimistic rant without substance and no debunking

manigandham 5y ago
Which debunking video was like that?
- space_rock 5y ago
  "Veritasium: BUSTED!" https://www.youtube.com/watch?v=5Hyy1zRZPiQ https://www.youtube.com/watch?v=5Hyy1zRZPiQ This is his area of expertise and is a great "busting" video Trash: "Elon Musk Invents UNDERGROUND Traffic Jam!" "Tesla Bot" No debunking. Small mindedness, pessimistic rant. Just says Elon will fail but not clear how he knows he will fail
  - kisstheblade 5y ago
    He actually has outlined exactly what's wrong with these ideas. I mean the hyperloop was supposed to be "like an air hockey table", well guess what, musk now "advocates for wheels"... It's just a really bad and unworkable idea. The idea of 1000km long vacuum tubes is beyond stupid, when we already have high speed rail. Please tell me how stating these facts are "small minded" or "pessimistic". His main point is usually about the massive unwarranted hype and blind hero worship around these concepts, and usually scams (the water stuff and other kickstarter projects). The truth hurts, I guess.
    - space_rock 5y ago
      I never mentioned hyperloop. Again this is the level of reply I would expect of Thunderf00t. You can do better
      - kisstheblade 5y ago
        This relates to hyperloop "Elon Musk Invents UNDERGROUND Traffic Jam!"

kragen 5y ago

Dehumidifiers aren't what's thermodynamically impossible, of course; Fontus was just making quantitative performance claims that were thermodynamically impossible about how small their system would be and how little energy it would use. You don't need to sink to citing YouTubers to figure out how much water air contains. You can just consult a standard psychrometric chart: https://commons.wikimedia.org/wiki/File:PsychrometricChart.SeaLevel.SI.svg https://commons.wikimedia.org/wiki/File:PsychrometricChart.S... You can see from that chart that at, for example, 20 degrees and 30% relative humidity (which, if you're not aware, is pretty dry), you have about 5 mg of water per gram of air, or about 5 grams of water per kg of air, which is about 0.8 cubic meters (1.2 g/liter). So if you want to produce 10 liters of water per day for your family, you need to run 2,000 cubic meters of air through your dehumidifier. (Or a bit more because you can't reduce it to 0% humidity.) That might sound like a lot, but it's per day, so it works out to 49 cfm, which is not "big fans and lots of power". If we're talking about a 300 mm square aperture it's 260 mm/s of airflow, a breeze you can barely feel, which requires a totally insignificant amount of power compared to the actual refrigeration involved. This is not going to fit nicely on your bicycle like in the fraudulent Fontus videos but it is entirely reasonable as a household appliance. Solar electricity is free if you aren't using it for something else. As for bacterial growth and filtering, yeah, that's a real design constraint, and it's one that HVAC systems have fallen down on in the past with disastrous results, but it's not some kind of unsolved engineering problem. Every air conditioner, sea voyage, and water tower deals with it. Here in Argentina just about every house has a rooftop drinking-water tank, where we control bacterial growth with chlorination, by impregnating the tank plastic with bacteriostatic agents, and by making the tanks opaque so algae can't grow. Thousands of years ago, mariners dealt with it by dropping a silver coin in each amphora of drinking water. It would be a more difficult problem if a dehumidifier were warm and moist, but actually it's cold and moist. As for the relative costs of tankers and electricity, well, that varies depending on where you are. Around here supply chains are so unreliable that I'd hate to rely on a weekly delivery from a water tanker in order to not die of thirst in 48 hours. (Fortunately, I live a few kilometers from the biggest river in the world. Water is not a problem here, though in places pollution is.)

blkhawk 5y ago
You also need power to take the heat away that is created when the water in the air turns into a liquid. Best case you need to cool for about 0.7kwh per litre of water you make. That means for your 10 litre example you need best case 7kwh. That is a decent sized solar array and if you have any inefficiencies in your heat pump setup it gets much worse. Also you assume per day - solar only works during the day so you need storage as well so your system can work during the night.

deleted 5y ago

[deleted]

ptrklly 5y ago

I don't have views on the credibility of specific technologies but I've hoped that these could be viable in places like coastal California where fog provides quite a bit of air moisture but it never rains--do you not agree with that?

kragen 5y ago
If you have fog or dew, you can just use a fog net: https://en.wikipedia.org/wiki/Fog_collection https://en.wikipedia.org/wiki/Fog_collection https://news.climate.columbia.edu/2011/03/07/the-fog-collectors-harvesting-water-from-thin-air/ https://news.climate.columbia.edu/2011/03/07/the-fog-collect... These are mentioned in Table 1 of the Nature article: https://www.nature.com/articles/s41586-021-03900-w.pdf https://www.nature.com/articles/s41586-021-03900-w.pdf In coastal California, redwood trees have been doing this since the Jurassic. In the conditions you describe, fog nets commonly yield 2–3 ℓ/m²/day of water (20–30 nm/second), though experimental projects have reached yields over 13 ℓ/m²/day (150 nm/s): https://www.oas.org/dsd/publications/unit/oea59e/ch12.htm https://www.oas.org/dsd/publications/unit/oea59e/ch12.htm Fog nets are easier to make and easier to repair, and consequently enormously cheaper. This makes them practical not only for drinking water but even for irrigation. They are more tolerant of damage, though they do need yearly maintenance. But they don't work on days without dew, and in some places, that's nearly all days.

WheelsAtLarge 5y ago

" It's a dehumidifier; in places where the air is wet, it rains, and you don't need it. In places where you need it, you need it because there's not much water, so it doesn't work well." I wonder how well it would work as a stand in for a desalination solution. Where there's all the water you want but it has salt (or other contaminant) that makes it impossible to drink. Seems to me that a beach would be the perfect place for it. At $150 price point it's a very good alternative to high price machinery.

jodrellblank 5y ago
Desalination produces a lot more water-per-KWh-energy than unboiling water from the atmosphere. Elsewhere in this thread someone linked a paper which estimates up to 100 litres per KWh for desalination, vs ~1 litre per KWh for condensing. Saving on machinery, or chemicals, might be important but $150 of materials for a device will buy you ~25,000 litres of water in bulk (in the USA).

jcranberry 5y ago

The linked nature paper points out that over a billion people without access to safe drinking water live in areas where their design would be high performance (tropical areas).

traverseda 5y ago

Very different technology, this is largely not solar-electric. It's solar-thermal with a bit of electric for a circulating fan and a small motor.