[HN Gopher] A Better Fog-Trap
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A Better Fog-Trap
Author : edward
Score : 43 points
Date : 2021-05-27 16:50 UTC (6 hours ago)
(HTM) web link (www.economist.com)
(TXT) w3m dump (www.economist.com)
| helios_invictus wrote:
| 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.
| ncmncm wrote:
| 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.
| cbzehner wrote:
| "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
| yboris wrote:
| Unpaywalled link: https://archive.is/Et8xe
| djoldman wrote:
| or if you like it outlined:
|
| https://outline.com/L4Dsm9
| Torkel wrote:
| "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 wrote:
| > "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 wrote:
| 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?
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(page generated 2021-05-27 23:02 UTC)