4 ms·

A Better Fog-Trap

51 points by edward 5y ago

yboris 5y ago
Unpaywalled link: https://archive.is/Et8xe https://archive.is/Et8xe
- djoldman 5y ago
  or if you like it outlined: https://outline.com/L4Dsm9 https://outline.com/L4Dsm9
helios_invictus 5y ago
A 50% increase in collection efficiency of water for the same amount of trap space with no additional product cost is pretty amazing! There is a capital cost of changing the way the traps are manufactured though.
- JulianMorrison 5y ago
  A thread that electrostatically traps things might have several other uses. Can it be spun fine, and sieve out particulates?
Torkel 5y ago
"A typical trap, with a 40-square-metre collecting area, yields about 200 litres a day. That is enough to supply around 60 people with drinking water. Such a collector costs $1,000 or so, and will last a decade." To me that sounds cheap already. 13c/month/person. $1.37/m3. I pay more than that per m3 (Sweden). To scale things up for agriculture or forests, I would assume a more industrial scale for the whole thing would make more sense. Feels like it could lead to an order of magnitude in lower cost - mainly because $1000/40m2 seems expensive. Growing forests in the desert using fog-water... could it be something for Elon's carbon capture contest? I don't know about relevant data points to make the calculations - how much water do you need to grow a forest in a desert? How much co2 does a forest capture when "completed"? How much time does that take?
- amelius 5y ago
  > "A typical trap, with a 40-square-metre collecting area, yields about 200 litres a day. That is enough to supply around 60 people with drinking water. Such a collector costs $1,000 or so, and will last a decade." Is that a linear mechanism? I.e., 1 square-metre yielding 5 litres a day?
  - Torkel 5y ago
    Good question... wikipedia did not yield an immediate answer. Could there be an "area effect", where one fog trap decreases yields of adjacent fog traps?
    - adrianN 5y ago
      There is only so much water in fog.
cbzehner 5y ago
"What I really need is a droid that understands the binary language of moisture vaporators." "Vaporators? Sir, my first job was programming binary loadlifters—very similar to your vaporators in most respects." ―Owen Lars and C-3PO
- JulianMorrison 5y ago
  Or wind traps and dew collectors from Dune.
ncmncm 5y ago
The tech for producing the fibers might be just what is needed to extract energy from wind with no moving parts. What is needed is such a fiber with a surface charge–electrons–readily stripped off by passing air molecules, and slightly conductive. To collect energy, a wire grid is held erect in a steady wind with streamers of this fiber at intersection points. As the wind carries away surface charges, the grid builds up a voltage relative to the ground. Electron current flowing from the ground to replenish the charge in the grid can do work. Alvin Marks patented such a design in the '80s, without going into detail about how it would shed charge. (Alvin Marks is known for winning a bitter fight with Edwin Land, of Polaroid, for the patent on polarizing sunglasses.) The grid would best be on a kite, with the wire to ground also the kitestring. Or it could be stretched between bridge uprights, or skyscrapers. The absolute efficiency, the fraction of wind energy extracted, is not very important if the construction and operating cost are low enough, as would be the case here. (The maximum practical efficiency of wind power extraction is about 1/3; if you try to extract more, the waste air blocks air you want to collect more from.) Stretched between existing structures, collecting too much of the energy would load the structures beyond their design limits anyway. The real wind bonanza is way high up, thus at the end of a kitestring. Wind energy goes up as the cube of wind speed, and wind speed (and steadiness) goes up with altitude, so available energy goes up as the fourth power of altitude before leveling off. There are structural limits on how tall you can build a wind turbine, but kites follow different rules. Any absolute inefficiency could be made up with multiple grids, one behind the other. Where to situate the kites, out of the way of air traffic, is an interesting problem. Probably the best place is on a former nuclear power plant reservation, that already has a big no-fly zone around it, and a power distribution network attachment point in the middle. There are other no-fly zones that could co-exist with kites. At some point, all the existing wind tower blades will degrade to uselessness, and you can stretch grids between their leftover towers. The space between existing skyscraper towers is all going to waste already, and buzzing them is frowned on.
- JulianMorrison 5y ago
  Story prompt: the kites of Chernobyl...
- jfengel 5y ago
imoverclocked 5y ago
As someone who lives on a well that sometimes dries up, I'd love to have a backup/redundant technology like this around. I wonder though, does it also capture pollutants? ie: what kinds of things would someone in a developed region with gas/coal/etc have to worry about with a system like this?

A Better Fog-Trap

51 points by edward 5y ago

yboris 5y ago

Unpaywalled link: https://archive.is/Et8xe https://archive.is/Et8xe

djoldman 5y ago
or if you like it outlined: https://outline.com/L4Dsm9 https://outline.com/L4Dsm9

helios_invictus 5y ago

A 50% increase in collection efficiency of water for the same amount of trap space with no additional product cost is pretty amazing! There is a capital cost of changing the way the traps are manufactured though.

JulianMorrison 5y ago
A thread that electrostatically traps things might have several other uses. Can it be spun fine, and sieve out particulates?

Torkel 5y ago

"A typical trap, with a 40-square-metre collecting area, yields about 200 litres a day. That is enough to supply around 60 people with drinking water. Such a collector costs $1,000 or so, and will last a decade." To me that sounds cheap already. 13c/month/person. $1.37/m3. I pay more than that per m3 (Sweden). To scale things up for agriculture or forests, I would assume a more industrial scale for the whole thing would make more sense. Feels like it could lead to an order of magnitude in lower cost - mainly because $1000/40m2 seems expensive. Growing forests in the desert using fog-water... could it be something for Elon's carbon capture contest? I don't know about relevant data points to make the calculations - how much water do you need to grow a forest in a desert? How much co2 does a forest capture when "completed"? How much time does that take?

amelius 5y ago
> "A typical trap, with a 40-square-metre collecting area, yields about 200 litres a day. That is enough to supply around 60 people with drinking water. Such a collector costs $1,000 or so, and will last a decade." Is that a linear mechanism? I.e., 1 square-metre yielding 5 litres a day?
- Torkel 5y ago
  Good question... wikipedia did not yield an immediate answer. Could there be an "area effect", where one fog trap decreases yields of adjacent fog traps?
  - adrianN 5y ago
    There is only so much water in fog.

cbzehner 5y ago

"What I really need is a droid that understands the binary language of moisture vaporators." "Vaporators? Sir, my first job was programming binary loadlifters—very similar to your vaporators in most respects." ―Owen Lars and C-3PO

JulianMorrison 5y ago
Or wind traps and dew collectors from Dune.

ncmncm 5y ago

The tech for producing the fibers might be just what is needed to extract energy from wind with no moving parts. What is needed is such a fiber with a surface charge–electrons–readily stripped off by passing air molecules, and slightly conductive. To collect energy, a wire grid is held erect in a steady wind with streamers of this fiber at intersection points. As the wind carries away surface charges, the grid builds up a voltage relative to the ground. Electron current flowing from the ground to replenish the charge in the grid can do work. Alvin Marks patented such a design in the '80s, without going into detail about how it would shed charge. (Alvin Marks is known for winning a bitter fight with Edwin Land, of Polaroid, for the patent on polarizing sunglasses.) The grid would best be on a kite, with the wire to ground also the kitestring. Or it could be stretched between bridge uprights, or skyscrapers. The absolute efficiency, the fraction of wind energy extracted, is not very important if the construction and operating cost are low enough, as would be the case here. (The maximum practical efficiency of wind power extraction is about 1/3; if you try to extract more, the waste air blocks air you want to collect more from.) Stretched between existing structures, collecting too much of the energy would load the structures beyond their design limits anyway. The real wind bonanza is way high up, thus at the end of a kitestring. Wind energy goes up as the cube of wind speed, and wind speed (and steadiness) goes up with altitude, so available energy goes up as the fourth power of altitude before leveling off. There are structural limits on how tall you can build a wind turbine, but kites follow different rules. Any absolute inefficiency could be made up with multiple grids, one behind the other. Where to situate the kites, out of the way of air traffic, is an interesting problem. Probably the best place is on a former nuclear power plant reservation, that already has a big no-fly zone around it, and a power distribution network attachment point in the middle. There are other no-fly zones that could co-exist with kites. At some point, all the existing wind tower blades will degrade to uselessness, and you can stretch grids between their leftover towers. The space between existing skyscraper towers is all going to waste already, and buzzing them is frowned on.

JulianMorrison 5y ago
Story prompt: the kites of Chernobyl...
jfengel 5y ago

imoverclocked 5y ago

As someone who lives on a well that sometimes dries up, I'd love to have a backup/redundant technology like this around. I wonder though, does it also capture pollutants? ie: what kinds of things would someone in a developed region with gas/coal/etc have to worry about with a system like this?