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>The system [...] was positioned on a Arizona State University roof. It’s still early stages, and the water only measured in the millimeters Millimeters is not

>The system [...] was positioned on a Arizona State University roof. It’s still early stages, and the water only measured in the millimeters Millimeters is not a useful unit of collected water! Granted millilitres wouldn't be much better without time as well.

srott 9y ago
Not bad for a roof of concept...
- organsnyder 9y ago
  Millimeters over what area, though? A millimeter depth over a kilometer^2 area is a decent amount of water; a millimeter depth over a meter^2, less so.
  - extrememacaroni 9y ago
    It's a millimeter towards around up.
  - froindt 9y ago
    They're measuring in a volumetric unit, and you switched it to a linear unit. They're using milliliters not millimeters. 1 milliliter = 1 cm^3 237 ml = 1 cup EDIT: Nevermind regarding the unit confusion. I'm still learning how to read.
    - itp 9y ago
      Unless I'm missing something, (s)he didn't switch any units. The original article as I am reading it clearly just says "millimeters" without any associated area or timeframe.
      - froindt 9y ago
        Hrm...yep...you're right. I read the first comment and could have sworn the quote from the article said milliliter. My eyes are playing tricks on me!
        narag 9y ago
        The linked article does say milliliter. Maybe they corrected it later?
  - jgh 9y ago
    I think TC screwed it up, the MIT article (linked in the article) says milliliters. --- > The test device was powered solely by sunlight, and although it was a small proof-of-concept device, if scaled up its output would be equivalent to more than a quarter-liter of water per day per kilogram of MOF, the researchers say. ... > The next step, Wang says, is to work on scaling up the system and boosting its efficiency. “We hope to have a system that’s able to produce liters of water.” These small, initial test systems were only designed to produce a few milliliters, to prove the concept worked in real-world conditions
  - narag 9y ago
    Millimeters over what area, though? [Edited] It could be any, if the device depends on area. The more area you use, the more water you get. Weather report often uses litres per square metres. One meter high per square metre is a thousand litres, so one mm would be a litre. Edit: in the article I read: These small, initial test systems were only designed to produce a few milliliter. So it's much less :-)
firethief 9y ago
That seems like exactly the unit. Just like when measuring rainfall, the amount collected scales with the area of the equipment. What would you prefer, mm/(mm)^2? I would assume time is on the scale of per day; that seems, at least to me, the only time unit they wouldn't have specified here. Of course, in an article this bloggy it's not a given that the reasonable interpretation of such vague units is the interpretation intended--but I think that there is a reasonable interpretation.
- delecti 9y ago
  Volume per unit of collection area per unit time at a given absolute humidity. It might be a bit too technical, but anything less really can't give you a sense of scale.
  - swsieber 9y ago
    I'd assume that since the thing depends on the day/night cycle, it'd be millimeters / day.
  - nkurz 9y ago
    The actual paper (https://www.nature.com/articles/s41467-018-03162-7 https://www.nature.com/articles/s41467-018-03162-7) actually gives something very close to numbers you want, although they express it as liters/day/kilogram @ humidity. Here's the abstract: Water scarcity is a particularly severe challenge in arid and desert climates. While a substantial amount of water is present in the form of vapour in the atmosphere, harvesting this water by state-of-the-art dewing technology can be extremely energy intensive and impractical, particularly when the relative humidity (RH) is low (i.e., below ~40% RH). In contrast, atmospheric water generators that utilise sorbents enable capture of vapour at low RH conditions and can be driven by the abundant source of solar-thermal energy with higher efficiency. Here, we demonstrate an air-cooled sorbent-based atmospheric water harvesting device using the metal−organic framework (MOF)-801 [Zr6O4(OH)4(fumarate)6] operating in an exceptionally arid climate (10–40% RH) and sub-zero dew points (Tempe, Arizona, USA) with a thermal efficiency (solar input to water conversion) of ~14%. We predict that this device delivered over 0.25 L of water per kg of MOF for a single daily cycle. https://www.nature.com/articles/s41467-018-03162-7 https://www.nature.com/articles/s41467-018-03162-7
nkurz 9y ago
The actual MIT press release has much better information than the Techcrunch article: The test device was powered solely by sunlight, and although it was a small proof-of-concept device, if scaled up its output would be equivalent to more than a quarter-liter of water per day per kilogram of MOF, the researchers say. With an optimal material choice, output can be as high as three times that of the current version, says Kim. http://news.mit.edu/2018/field-tests-device-harvests-water-desert-air-0322 http://news.mit.edu/2018/field-tests-device-harvests-water-d... Edit: And the underlying paper is here: https://www.nature.com/articles/s41467-018-03162-7 https://www.nature.com/articles/s41467-018-03162-7
- sctb 9y ago
  Thanks! We've updated the link from https://techcrunch.com/2018/03/22/mits-new-device-can-pull-water-from-desert-air/ https://techcrunch.com/2018/03/22/mits-new-device-can-pull-w....
- Animats 9y ago
  That's a desert survival device. Not a useful source of water for anything other than dire emergencies.
  - AdmiralAsshat 9y ago
    Arizona air isn't very humid, to my knowledge. I'd be curious to see how much this device can gather in gulf areas. It might be very useful in somewhere like Saudi Arabia, where expensive desalinization plants are pretty much their only source of fresh drinking water.
    - nkurz 9y ago
      Arizona air isn't very humid, to my knowledge. I wasn't sure about the numbers either, so I looked it up. The levels were higher than I would have guessed, generally ranging from 30%-50% relative humidity. https://www.currentresults.com/Weather/Arizona/humidity-annual.php https://www.currentresults.com/Weather/Arizona/humidity-annu...
incompatible 9y ago
It's ambiguous anyway what "only measured in the millimeters" refers to. You can measure any length you like in millimeters, like the distance to the moon. Perhaps they mean less than a meter?

srott 9y ago

Not bad for a roof of concept...

organsnyder 9y ago
Millimeters over what area, though? A millimeter depth over a kilometer^2 area is a decent amount of water; a millimeter depth over a meter^2, less so.
- extrememacaroni 9y ago
  It's a millimeter towards around up.
- froindt 9y ago
  They're measuring in a volumetric unit, and you switched it to a linear unit. They're using milliliters not millimeters. 1 milliliter = 1 cm^3 237 ml = 1 cup EDIT: Nevermind regarding the unit confusion. I'm still learning how to read.
  - itp 9y ago
    Unless I'm missing something, (s)he didn't switch any units. The original article as I am reading it clearly just says "millimeters" without any associated area or timeframe.
    - froindt 9y ago
      Hrm...yep...you're right. I read the first comment and could have sworn the quote from the article said milliliter. My eyes are playing tricks on me!
      - narag 9y ago
        The linked article does say milliliter. Maybe they corrected it later?
- jgh 9y ago
  I think TC screwed it up, the MIT article (linked in the article) says milliliters. --- > The test device was powered solely by sunlight, and although it was a small proof-of-concept device, if scaled up its output would be equivalent to more than a quarter-liter of water per day per kilogram of MOF, the researchers say. ... > The next step, Wang says, is to work on scaling up the system and boosting its efficiency. “We hope to have a system that’s able to produce liters of water.” These small, initial test systems were only designed to produce a few milliliters, to prove the concept worked in real-world conditions
- narag 9y ago
  Millimeters over what area, though? [Edited] It could be any, if the device depends on area. The more area you use, the more water you get. Weather report often uses litres per square metres. One meter high per square metre is a thousand litres, so one mm would be a litre. Edit: in the article I read: These small, initial test systems were only designed to produce a few milliliter. So it's much less :-)

firethief 9y ago

That seems like exactly the unit. Just like when measuring rainfall, the amount collected scales with the area of the equipment. What would you prefer, mm/(mm)^2? I would assume time is on the scale of per day; that seems, at least to me, the only time unit they wouldn't have specified here. Of course, in an article this bloggy it's not a given that the reasonable interpretation of such vague units is the interpretation intended--but I think that there is a reasonable interpretation.

delecti 9y ago
Volume per unit of collection area per unit time at a given absolute humidity. It might be a bit too technical, but anything less really can't give you a sense of scale.
- swsieber 9y ago
  I'd assume that since the thing depends on the day/night cycle, it'd be millimeters / day.
- nkurz 9y ago
  The actual paper (https://www.nature.com/articles/s41467-018-03162-7 https://www.nature.com/articles/s41467-018-03162-7) actually gives something very close to numbers you want, although they express it as liters/day/kilogram @ humidity. Here's the abstract: Water scarcity is a particularly severe challenge in arid and desert climates. While a substantial amount of water is present in the form of vapour in the atmosphere, harvesting this water by state-of-the-art dewing technology can be extremely energy intensive and impractical, particularly when the relative humidity (RH) is low (i.e., below ~40% RH). In contrast, atmospheric water generators that utilise sorbents enable capture of vapour at low RH conditions and can be driven by the abundant source of solar-thermal energy with higher efficiency. Here, we demonstrate an air-cooled sorbent-based atmospheric water harvesting device using the metal−organic framework (MOF)-801 [Zr6O4(OH)4(fumarate)6] operating in an exceptionally arid climate (10–40% RH) and sub-zero dew points (Tempe, Arizona, USA) with a thermal efficiency (solar input to water conversion) of ~14%. We predict that this device delivered over 0.25 L of water per kg of MOF for a single daily cycle. https://www.nature.com/articles/s41467-018-03162-7 https://www.nature.com/articles/s41467-018-03162-7

nkurz 9y ago

The actual MIT press release has much better information than the Techcrunch article: The test device was powered solely by sunlight, and although it was a small proof-of-concept device, if scaled up its output would be equivalent to more than a quarter-liter of water per day per kilogram of MOF, the researchers say. With an optimal material choice, output can be as high as three times that of the current version, says Kim. http://news.mit.edu/2018/field-tests-device-harvests-water-desert-air-0322 http://news.mit.edu/2018/field-tests-device-harvests-water-d... Edit: And the underlying paper is here: https://www.nature.com/articles/s41467-018-03162-7 https://www.nature.com/articles/s41467-018-03162-7

sctb 9y ago
Thanks! We've updated the link from https://techcrunch.com/2018/03/22/mits-new-device-can-pull-water-from-desert-air/ https://techcrunch.com/2018/03/22/mits-new-device-can-pull-w....
Animats 9y ago
That's a desert survival device. Not a useful source of water for anything other than dire emergencies.
- AdmiralAsshat 9y ago
  Arizona air isn't very humid, to my knowledge. I'd be curious to see how much this device can gather in gulf areas. It might be very useful in somewhere like Saudi Arabia, where expensive desalinization plants are pretty much their only source of fresh drinking water.
  - nkurz 9y ago
    Arizona air isn't very humid, to my knowledge. I wasn't sure about the numbers either, so I looked it up. The levels were higher than I would have guessed, generally ranging from 30%-50% relative humidity. https://www.currentresults.com/Weather/Arizona/humidity-annual.php https://www.currentresults.com/Weather/Arizona/humidity-annu...

incompatible 9y ago

It's ambiguous anyway what "only measured in the millimeters" refers to. You can measure any length you like in millimeters, like the distance to the moon. Perhaps they mean less than a meter?