Extracting Water from Fog

Most of us take it for granted that water is as close as your kitchen tap. But that’s not true everywhere. Two scientists at MIT have a new method for harvesting water from fog, especially fog released from cooling towers such as those found from power plants. It turns out, harvesting water from fog isn’t a new idea. You typically insert a mesh into the air and collect water droplets from the fog. The problem is with a typical diameter of 10 microns, the water droplets mostly miss the mesh, meaning they typically extract no more than 2% of the water content in the air.

The team found two reasons for the low efficiency. Water clogs the mesh openings which can be somewhat mitigated by using coated meshes that shed water quickly. Even in the lab that only increases the yield to about 10%. The bigger problem, though, is basically only some of the droplets hit the mesh, and even those that do may not stick because of drag. Fine meshes can help but are harder to make and have low structural integrity. Their solution? Inject ions into the fog to charge the water droplets and impart the opposite charge on the mesh.

This seems simple enough and the testing proves it out. Oddly enough, when using the technique, finer meshes do not necessarily translate into higher collection rates due to aerodynamics. Although the test setups were relatively small, the energy consumption scaled up appears to be about 2 kWh per cubic meter which is less than other water recovery methods like desalination. Using a concentrated fog source such as that created by a cooling tower could drop that down by a factor of 10, which is much less than conventional water source energy usage.

We love to see people take their knowledge of bending electrons to their will and use it to improve conditions for mankind. If only there were a prize for that. Of course, it is possible to pull water out of thin air. Electronics can also play a part in cleaning up water you already have.

52 thoughts on “Extracting Water from Fog

    1. They connect the mesh to ground and position a needle 4cm away, perpendicular to the mesh.

      “The needle was connected to a high-voltage generator (Spellman SL600) delivering voltages from 0 to −25 kV. Corona discharge was observed to start at a voltage around −7 kV. The onset of corona was detected by the sudden increase in current as ions were generated and traveled between the two electrodes and by the sudden change in the flow pattern of fog.”

        1. Aha! I missed the typo in the picture text that you were questioning–must have just filled in the missing “s”.
          Anyway, I guess I answered my own question, “How did they create the corona discharge?”

  1. I recall someone doing something regarding distillation research up at Tech using something like this. How do they make it rain, maybe call NOAA and see what they disclose with EMF, I forget? I’d think charge is involved with the breakdown voltage factors for lighting and definitely signals a storm of some sort. Wonder if there is a connection?

    1. AIUI, Sodium chloride flares have mostly replaced silver iodide flares for “rainmaking”. They are cheaper and quite effective, but the moisture needs to be in the air for it to be attracted to the ions.

      1. I was under the impression that there is more electromagnetic frequency (EMF) generating rain versus the chemical methods now days… though chemical methods look like the norm from reading lately.

        I double checked and the wikipedia for weather modification is updated to note “ioinizers” rather vaguely (similar process to cause water to condense and can be found on youtube even though I am not finding at the moment): https://en.wikipedia.org/wiki/Weather_modification


        I’m wondering if there is something related to the Lord Kelvin Water Droplet HV generation, though backwards.

        This is like you’re thinking Ren and for weather modification:

  2. I wouldn’t have thought extracting water from cooling tower fog would make much sense. Surely if you’re running a cooling tower, you have plenty of water to pump into it in the first place? Otherwise you’d be using some other heat-shedding technique.
    Now extracting water from fog in a desert… that is where this idea could really benifit people.

        1. Depending on the water source location to freshwater outlets into the seawater or maybe some regions seawater (I’m not sure about the later maybe)… you may have minerals like precious metals to mine as well as use for other industries.

          Another idea for all the salt other than ship to your local great salt lake… is like the nuclear, solar, coal or whatever thermal based power plants can do is store heat in molten salt in super-insulated containers under or above ground. This will require some critical attention to pipe fitting and materials sciences updates for lining the molten salt loop… though otherwise seems like would keep people busy with lower clearance maintenance jobs, even for R&D and especially for solar… have a method to power the stations at night.

    1. Cooling towers are the second highest use of fresh water in the U.S. Agriculture being number one.

      Depending on the type of building (office, MFG plant, hospital, school, datacenter, etc.) 40%-60% of total water used goes to the cooling tower. I’m going to take a guess but maybe 60%-80% of all water used in that cooling towers is evaporated into the air (fog). If someone could capture this water without using too much electricity, it would be a huge success.

      I work at Flozone and we use a non-chemical treatment for cooling tower water and the water that we drain into the sewer is so clean some of our customers use it to water their lawns.

  3. The problem is, you have really low output of water. Or you have to build a tower that’s really massive. Would probably be better to just use trucks to haul water.

      1. News flash you can’t have fog without water nearby, it may be SALT water but it’s near, at least as the crow flys, Chile I am looking at you.
        So let me ask you something, do Chileans think significantly differently from North Americans? Because I can’t say what they would do but I can guess what we would, we would continue to expand our proven system until we were 3/4 of the way to a total collapse and then when it was far too late we would maybe invest in desalination infrastructure.
        Sound about right?
        How about this?
        Maybe, and I’m just spitballin’ here, you shouldn’t try and remove large amounts of environmental moisture from a desert, might just be me but that sounds like a bad thing.

    1. Aerodynamics, the air has move through it. What about a fine mesh that’s vibrated to encourage condensate to form drops and run away? Lower tech so easier to maintain. And should be significantly less than 2kwh / meter (I assume that’s 2kwh/ day.)

      1. I was just thinking that. The ionic insertion idea is high tech, but what about determining what frequency (or frequencies) resonating the mesh would produce higher yield?

        Also, what about heat recapture for use in industrial and home heating? Thermodynamic transfer can cool much of the water used in a power plant, the trick is to pipe it into a city or community effectively. I’ve always thought that evaporation is the quick and dirty method of the heat exchange cycle. Utilize that to heat homes/businesses and their water, you then kill 2 birds with one power plant. Plus save on real estate for said plant.

        Mind you, hot water distribution networks within a city aren’t inexpensive. The result would be effective use of the thermal energy (approaching 90+ percent if you don’t factor in what it costs to pump the steam/water) and savings in the carbon footprint since the heat you’re providing to the homes and businesses keep them from needing to generate the heat locally.

        1. (lack of edit)
          And also a lot of greenhouse are located near nuclear plant to recycle hot water in winter.
          There is even an alligators park near a nuclear plant in France (hey we are the one that made gozilla first!).

  4. In South Africa, we have many Coal power stations with massive cooling towers which were built when water scarcity was not on the Governments priority list. Our power utility is one of the largest single users of fresh water in the country. Many years later, now that water supply is at risk (Cape Town almost recently ran completely dry), solutions like this could be retrofitted onto the cooling towers to create somewhat of a closed-cycle cooling system, greatly reducing the water demand of the lumbering coal-fired stations.



  5. Something like this could be a game changer in water-scarce countries. In South Africa, the majority of our power stations use huge evaporative cooling towers fed by fresh water from rivers and dams. This wasn’t a problem when they were built years ago, but now fresh water is becoming increasingly scarce (Cape Town nearly ran out of water a month or two ago… #DayZero).

    The power utility, Eskom, is one of the single largest users of fresh water in the country. Retrofitting something like this to the cooling towers could allow significant water recapture and create somewhat of a closed-loop cooling system, freeing up a few billion litres a year.



  6. If the fog is from a cooling tower (vs. “natural” fog) it will be in moving air.
    My first thought: pump it up one side of a double helix / screw shaped tower, let a vortex push the water against the walls, and run the condensation off in channels.
    At the top, a fan forces the air down the other side of the helix to double the water capturing area.

    1. I’ve thought about that design a lot, but the problem is the cost to make it vs. water saved.
      Water per 1000 Gallons is only around
      $3 in Nashville TN, Huntsville AL, Hanover MD
      $4 in Richmond VA, Newnan GA
      $5.60 in Miami FL.
      Some cooling towers a year use 300,00 gallons, 1,000,000 gallons, 3,000,000 gallons, 5,000,000 gallons depending on what type of building they are cooling (schools, offices, MFG plants, casinos, datacenters, power plants) and how much they run. Some building run cooling all year, some only during the summer.
      The device needs to be small, cheap, it can not overcome the height restrictions of some customers, very structurally strong as to not blow away and damage property, or restrict the flow of air (fan pointed down) of the cooling tower. – Flozone Services

  7. Now this has a use in the industry I work in.

    Anti legionella.

    Cooling tower vapour is the major carrier of legionella bacteria from a poorly maintained tower. We already use drift eliminatators to minimise the vapour put out from the towers, but add this tech…

  8. Archaeologists realized at some point that some ancient civilization had solved their water problems in an interesting way. They built huge piles of rounded rocks, with as many air gaps as possible. As the moist morning air blew through the night-cooled rocks, it condensed and dripped to the ground.
    Thousands of years later, this system still works, with water coming out the bottom, no further effort required.

    1. 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!

  9. “Harvesting water from fog is not a new idea”…..yes, it is called rain and condensation. What a breakthrough!!!! Zero Mass Water is a huge scam. It is not cost effective by ANY measure and has been debunked all over the place.

  10. “Last October, a University of California, Berkeley, team headed down to the Arizona desert, plopped their newest prototype water harvester into the backyard of a tract home and started sucking water out of the air without any power other than sunlight. The successful field test of their larger, next-generation harvester proved what the team had predicted earlier in 2017: that the water harvester can extract drinkable water every day/night cycle at very low humidity and at low cost, making it ideal for people living in arid, water-starved areas of the world.”

  11. The cost of the water harvester vs the amount water collected makes it a losing proposition. It would be more cost effective to truck water in. If the thought of the truck violates your environmental sensibilities then the manufacture and trucking of the water harvester and its raw materials should at well. Water is a zero sum game. There is a certain amount of hydrogen and oxygen on Earth. Increasing world temperature cause polar fresh water to be released into the oceans where the increased temperature would evaporate more of it. More vapor + high temperature = more storms and more water inland. When the earth cools sufficiently, more water gets sequestered into polar ice. The problem is humans insist on living in areas that are not able to support them, whereas other animals migrate, go extinct or develop in more hospitable areas. Humans using machinery, energy, and vehicles to force water into areas where it does not want to be just expends energy and resources.

    1. Youre the fun guy at parties i guess. You use the internet, which expends energy and resources, to tell others that technology is shit and we rather should still sit in caves, while men walked on the moon…were water doesnt want to be.

    2. Damn…I thought I was the one with pipe dreams. Maybe try a pipe or figure the coefficient of performance on a refrigeration evaporator condenser operation is more cost effective. Still, we need to move forward with advancing technology and sometimes the starting point isn’t as efficient until all the sciences (usually I find materials and energy… oh yeah scientists with mass info and apps and engineers with energy and mass info and apps) leaders and followers with the bolder ideas that aren’t completely wrong in intent, or just for grant/subsidy money, converge to be wowed. No poop… it worked. Fire it up! :-)

      Well, we’re not flooded out with ice caps covering where the current migratory routes and settlement are. Just take a look outside where there are stream, creeks, rivers and valleys. Way dryer than was at one time. Huh, go figure… not wrong though.

      My personal opinion is we need to as humans, since were are more advanced domesticate complex social systems thinkers and appliers can, develop the most inhospitable areas for human life that are reasonable to develop (like maybe we want ice caps and the death valleys though the later seems more logical for solar concentrating trough greenhouse utilities and dryer climate operations) and let the more lively areas be our natural backup minus the deadly predators and most poisonous life forms unless they are needed for medicine or maybe safer other life form biocides (pesticide, herbicides, etc.). Seems with more renewable’s, recycling, re-using and restoring… that will help with not wasting energy as heat.

  12. These water harvesters are an age old idea. Look up solar still in any survival manual and you will see this exact device. If this is what our Universities are studying then we really have problems because I learned this exact process in military survival school a long time ago. It works but it is so inefficient in terms of energy expended vs water supplied that it is only viable if your life depends on having a very small quantity of water available.

  13. We had similar systems to get the coolant mist out of the air in one of the shops I worked in. I think they were called foghogs or something. You dont even need the screen when you use electrostatics. The fog is attracted to plates after being charged and drips down and out the drain.

    Problem with electrostatic discharge systems is they also attract any dust or other particulates in the air and you are going to get a lot of that in the water too.

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