10 thoughts on “Desalinating Water”

  1. …and for cleaning brackish wastewater generated from hydraulic fracturing.

    Fools. They put that in the second paragraph. Don’t they know enviro moon-bats’ average ability to remain focused peters out at 3 sentences?

  2. This sounds very promising. If it works, it could be a massive boon, because it would make desalination cheap.

    I predict the envioros will oppose this if it works, because cheap plentiful water would encourage agriculture, which they don’t like.

    I wonder how this new process would be for cleaning a rive, the next time the EPA turns one bright orange? (Something the envoros didn’t seem to mind).

  3. I’m interested to see how much power this really uses. If it’s a fraction of what desalinization needs now…we’re “almost” talking water too cheap to meter.

    1. Gradient’s system is a good example of using cheap thermal energy to substitute for expensive hardware and electricity- when you have byproduct fuel gas that is otherwise unusable, distillation is economical because the fuel is nearly free.

      For large-scale use for agriculture or domestic water, nothing beats reverse osmosis.

  4. Reverse osmosis is already at 50% of the thermodynamic limit for purification. All these other techniques are far less efficient.

    This latest press release is just electrodialysis with a porous medium instead of a membrane to suppress diffusion. There’s no shock wave, only a steep concentration gradient misnamed. It can process highly saline feedstocks that are hard on RO systems, this non-membrane system may have longer life and lower maintenance costs than membrane systems, but can’t and probably won’t be able to compete with RO on a $/kg product basis.

    Just another publish-or-perish academic fluff piece.

    1. Mechanical vapor recompression? In theory, this heat pump-like still is at the thermodynamic limit whereas multi-stage distillation (where the heat of condensation of the upstream stage supplies the heat of evaporation of the stage downstream to it) would need a gazillion stages (called “effects”) to get comparable efficiency.

      You see, one of the laws of thermodynamics tells you that heat always flows “downhill” unless you add mechanical work, and the multi-effect still needs more and more steps on the way to the bottom to get high efficiency. In vapor recompression, you can condense at a (slightly) higher temperature that you evaporate because you add mechanical work to compress the vapor and hence raise the liquid-vapor saturation temperature.

      I see the practical efficiency limit of RO as the energy loss of shoving fluid through resisting membranes whereas vapor recompression is limited by the need to transfer enormous amounts of heat across a low temperature difference. But vapor compression needs only one “effect” (i.e., distillation chamber).

      The big advantage I see to vapor recompression is that you don’t have membranes that can wear out or get contaminated. In small sizes, however (maple syrup production), RO is much cheaper in capital cost than vapor recompression.

  5. It seems the cheapest way to desalinate sea water is to collect rain water.
    And in areas where there is a lack of rain, develop cheap ways of transporting water from areas where there is abundant fresh water.

    In terms of shipping, the lowest cost per ton, to ship is to use pipelines.
    The second lowest cost way to ship is to use boats.

    The cheapest way to use ships to transport over water, would involve using a nuclear powerplant to overcome the resistance of pushing something thru the water. Or one uses a lot of fuel to ship something thousands of km, and nuclear energy is high density energy source.

    So water is cheap because it’s shipped via pipes, and if one lower the cost of shipping over the ocean, one might become somewhat competitive compared to using pipelines.

    So I would say in terms of simple solution, if one had nuclear powered tugs, which were made cheaply one drag large amount of freshwater across the ocean. So the scale of the amount of water is of the order of a cubic km of water, or 1 billion tons of water. And the price of water being about 10 cent per ton, so total gross worth of one shipment being 1000 million dollars.
    Or collecting the water to ship could be about 10 cent a ton, shipping it another 10 cents, and distributing it at the destination point, another 100 cents per ton.
    So wiki:
    “Prices for water sold by tanker trucks in bulk, which is common in cities of some developing countries for households without access to piped water supply, are set in the market. Prices for trucked water vary between about US$1 and US$6 per cubic meter.”
    And:
    Prices for piped water supply provided by utilities, be they publicly or privately managed, are determined administratively (see water tariffs). They vary from US$ 0.01 to almost US$ 8 per cubic meter ”
    https://en.wikipedia.org/wiki/Water_pricing

    So not going to ship water to places paying 1 cent per cubic meter, but you could ship to places paying more than $1 per cubic meter.

    Where you get freshwater could be where there is the most water- which are polar caps, or places which rain say more the 1000 inches of water per year or river outlet which has clean water which accessible to ships.
    An advantage of polar sea ice is could tow it with having to contain the water in some vessel, or tow 2 billion tons and arrive with +1 billion tons. Other source of freshwater one need a way to contain the freshwater so it doesn’t mix with sea water. One aspect is that freshwater is less dense than sea water, so it’s similar to shipping crude oil, but unlike crude oil there isn’t much problem with oil spills- so triple hull supertankers not needed. But one would have to go much bigger than supertanker and one could not be planing going thru say, the panama canal.
    So the dimension of a ship might be 1 km wide by 20 km long, which if held 10 meter of water would only be .2 billion tons. Or if only .2 billion one could consider it needs roughly 5 times the speed of 1 billion ton ship.
    And generally speaking the range of speed might be within 1 to 10 mph.
    One allow lower speeds around 1 mph [24 miles per day] were the vessel able to withstand any kind of weather, and faster speeds capable of mitigating or avoid larger storms.
    With bigger ships one is basically a floating island, and could think of ship hull having a function similar to a break water one could have on island. Or main structural element of the ship functions as a break water.
    So for example have 10 meter diameter steel pipe, which is 1/2 thick steel. And have this as perimeter, and roughly have something like a huge plastic bag which is attached to the perimeter, separated 20 meter of open water. So you tow the perimeter and it tows the “plastic bag”.
    And the perimeter is 2/3rd filled with water, or it floats 3 meter above the water. And one picks up and drops off these “plastic bags” by perimeter becoming neutral buoyant and sinking below it, or one end opens and closes to contain the “bag”. And the “bag” would cost more to make than the perimeter. And say it’s made from 1/4″ steel and it big- and the 10 by 50 km was a bit small, 10 by 100 km which has draught of 20 meters depth and it’s going float on bubble of air.
    And since so large will have to be made in huge sections, say 1 km long by 20 meters wide and deep. So in this simple shape, it’s 1000 meter by 20 and 20, 400,000 square meter, and .25″ thick [0.00635 meters]
    and so cubic meter of steel: 2540 cubic meter times 7.8 is, 19812 tonnes, for just perimeter need 220 of them. 19812 times 220 is
    4.35864 million tons. And assume millions of tons cost billions of dollars. Now with inner wall of this perimeter, remove 10 meter of it along top, and assume this amount metal used from structural members.
    In the donut hole have plastic liner, which will have air in it, and fill the ship with water. So one can have middle section filled with about 5 meters of air and have 10 meters of water on top of that air. So going
    to hold about +10 meter by 10 km by 100 km of water, and float fairly high in the ocean. And cost about +2 billion dollars.
    Now important bit is can it be economical, so has to make somewhere around 400 million per year. 10 x 100,000 x 10,000 is 10 billion cubic meters. Hmm made it too big. Oh it was 1 by 20 km for .2 billion cubic meters. So one should start smaller, as said somewhere around 1 cubic km and the nuclear tug probably the biggest cost.
    And were one start by dragging polar sea ice, this seems like lower start cost cost, but dragging around other source of water could evolve from it, if nuclear tugs existed and were off the shelf.

  6. ” if nuclear tugs existed and were off the shelf …”

    I would buy one, scrap all the bits that looked like a “boat”, and re-purpose the power plant / engine systems towards, well, any darned application I wanted, possibly including desalination.

    Ceteris is never paribus. I can’t see all else remaining the same once vehicle-sized mass-produced (and about three-decades over-due) nuclear-fission power systems are available.

    1. ” if nuclear tugs existed and were off the shelf …”

      I would buy one, scrap all the bits that looked like a “boat”, and re-purpose the power plant / engine systems towards, well, any darned application I wanted, possibly including desalination.

      Ceteris is never paribus. I can’t see all else remaining the same once vehicle-sized mass-produced (and about three-decades over-due) nuclear-fission power systems are available.–

      True. But I didn’t mean off the shelf to mean cheap.
      Though it could be cheap.
      But something on order of getting a nuclear powerplant for say 1/2 billion dollars.
      So if have 1/2 billion dollar one can buy nuclear tug.
      Though maybe it’s 1 or 2 billion dollars- point is if have enough money one get the tug- it’s available to buy- not how much how much the price is..
      Unlike something Bill Gates doing- spending million dollar and year’s of his time trying to get a nuclear electrical power plant which are widely available and cheap- and off the shelf.

      Could there be large market for nuclear engines for tugs and cargo ships, cruise ships, etc, probably- if it was legal to do this.

      Point is if access to cheap freshwater was actually important, government could take steps, so as to allow there to be commercial nuclear tugs for this purpose.

      But perhaps, since the US is allowing a terrorist State to make nuclear weapons, we can now scrap the Nuclear Proliferation treaty- if it’s not to prevent terrorists from getting nuclear weapons, what other purpose could the treaty have?

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