Producing Potable Water in a Oceanic Environment.

It should be possible to pull potable water from the air any place on Earth where deep ocean water is at a temperature well below the local surface dew point.
Pumping water through a heat exchanger that is at a temperature well below the dew point of the surrounding air will generate condensation in proportion to the amount of water being pumped, the area of the cooling/collecting foils, the dew point temperature, and volume of the air being cooled.
What is the best way to collect that condensation?
Once reducing the temperature of the air to the dew point, the heat exchanger must now handle the phase energy of water moving from a vapor to liquid state. This phase energy is about 540 times the energy required to change the temperature of an equal volume of water by one degree C.
Now another question arises; what is the most efficient way to draw the cold water to the surface where it can be used in a heat exchanger to produce potable water.

I didn't mean to interupt any of the pompom shaking political B.S.; but I did want to share this.

Comments

  • It seems like an energy demanding process...imageimage
  • Bull02:
    Thank you for your reply.
    If the return pipe is at the same depth as the intake pipe once the system has been fully charged the energy required to pump the water would be proportional to the resistance of the pipes and heat exchanger plus the small density differential between intake and outlet water volumes.
    Because the return pipe is at the same depth of the intake the net change in gravitational potential would be zero.
    The pumping could be accomplished by a "wave pump" where the energy of tidal or wind generated waves drive an inline pump.

  • Sarem;
    Thank you for your interesting reply.
    Because of the requirement for the MOF materials I believe it would be more efficient to use properly configured Peltier junctions in an oceanic environment where the hot side of the junctions are heated by the sun and the water is collected from the cold sides.
    The challenge is scale and infrastructure cost. Because of this I believe using wave driven pumps and heat exchangers to harvest water from the air is a better approach at meeting this challenge in an oceanic evironment.
  • Because for some reason my memory remains, while my body turns to mush, I seemed to recall that at least ten years ago I wrote a post in this Forum about sea water distillation devices. Having little to do other than to nap, I decided to check my previous posts, and lo and behold I found the post.

    It is about an article I read in the Pacific Islands Report about nine or ten years ago. At that time I did not know how to link to other sites on the internet, so I don't think there is a link to the original article in my prior post. According to my prior post, however, the report in the Pacific Islands Report discusses an article from the Marianas Variety dated September 3, 2009. If either the Pacific Islands Report or the Marianas Variety have extensive archives, maybe our highly talented friends in here can find the original articles.

    But the concept is simple to imagine. Buy some plywood. Cut two pieces, each 4' long, and 12" high at one end, and 8-10" high at the other end. Join them together with end pieces, one 3' x 12", and the other 3' x 8-10". You have built a box four feet long and a foot high at one end, and 8-10" high at the other end. Paint the inside of the box black. With the advent of new technologies, I would imagine that a product called "Flex Paint," a rubberized substance, would be perfect. Now you have a 4' x 3' box painted black inside to absorb sunlight, and higher at one end than the other.

    Take a piece of clear acrylic and put it over the opening at the top of the box. Cut the acrylic to size, and find a way to secure it so that it doesn't slide around. Fill the box with sea water, put the top on, and let the sun do its magic. Soon, evaporated pure water will begin to appear on the underside of the acrylic, and run down from the high end to the low end (gravity is just the absence of levity), and put a tube at the bottom of the acrylic to allow the pure water out into a collection device. Drinking water from sea water with nothing but plywood, a glass or acrylic top, some black paint, gravity and sunlight. All readily available in Micronesia.

    Here is the post I wrote ten or eleven years ago:

    http://www.micronesiaforum.org/index.php?p=/discussion/5732/some-good-news
  • A couple of comments about the sea water stills discussed in my prior post. In reviewing my post from 2009, a couple of comments stood out. The first is from a poster who said he or she preferred good old imported water in plastic bottles. As we now are acutely aware, plastic is possibly the greatest environmental disaster known to man. Once these plastic bottles are drained of their water, what good are they? They are simply discarded, either into landfills, polluting the land, or right into the ocean, where they collect undisturbed and pollute the sea bed. Drinking water from imported plastic bottles is simply a really bad idea.

    The second point is related to the first. It discusses the use of black polystyrene to line the stills. Polystyrene is plastic. Like plastic bottles, it does not bio-degrade. Hopefully if this idea is attractive, those who might pursue it could find a better, more environmentally acceptable way to line the stills with black liner to absorb the sun's life giving heat.
  • Good stuff Sarem:
    I think Rain Water Collection is the best way to go.
    Desalination by distillation is an interesting idea. But if you collect the water from the atmosphere the creator has already put most of the energy into the process.
    I can see your box collector working quite well IF the collecting area is kept well below the condensation temperature inside the box; which increases as temperature rises. This becomes more problematic given the thermal transfer required for condensation to take place. There is also the issue of solids building up on the collection service and dissolving back into the condensate.
    Also; is poly, heat, and potable water a good mix?
    For drinking I have been wanting to make a rain water collection system because of the expense of bottled water. 9 square meters of water collecting area would gather about 228.6 liters (60.39 gallons) of water for each 2.54 centimeters (one inch) of precipitation.
    Area X depth = volume.
    9*.0254=.2286 cubic meters= 228.6 liters = 60.39 gallons.
    I think this is right but check to be sure.
    If it is close then I think Rain Water Collection seems the best way.
  • As long as it rains, Gavilan. Rain water collection is extremely problematic during times of drought. Even in times of drought, however, there is always water in the ocean.

    Sort of like solar and wind power. Solar is great, but only when the sun shines. The wind blows most of the time. Each compliments the other, like rain and solar distillation systems.
  • Solar and wind can be blended and stored in pumped hydro, batteries, or flywheels.
    Tidal currents are both predictable and dependable and require small storage capacities since slack tide is so short.
    For scaled collection of water from the air a cold deep water - surface heat exchanger - deep water return seems to be the most effective means other than Rain Water Collection.
    Solar distillation requires very large collection areas and presents numerous problems that are not present with water condensed from the air.
    The energy input for distillation methods is greater than 540 cals per gram of water processed.
  • @Gavilan/You're alright my friend we need more topics like this.This forum has become a nightmare.

    There are many ingenious ways being thought of or already in the works to create genuine water supply.For is natives of the Pacific its challenging.Eventually success will come along.
  • A reverse osmosis system, powered by solar energy, is now possible. Example is the RO system used by some of the outer islands in RMI to make their drinking water which was quite useful during the drought that hit that part of the country last year. Just another option that is easy to set up; with parts already available in the market.
  • In the islands, you just bring the RO unit to a location near the ocean; so your intake ocean water is accessible. Connect the plumbing from RO unit to the ocean--not deep; just deep enough so the end of the intake pump does not pump in air.

    Then, you connect the solar unit to provide the power to the RO unit. Turn on the RO unit; and it starts to make purified water. It is a desalination system that will operate as long as the sun does shine; as long as the ocean water is accessible. You can also store electricity from the solar panels--to be used during the cloudy or rainy days. Sounds like a good and appropriate technology for the islands in Micronesia.
  • Marc;
    Thank you for your reply.
    I believe Reverse Osmosis requires the use of consumable filters and membranes. I believe the quality of water produced is a function of the condition and efficiency of those filters and membranes.
    Atmospheric condensate should be of the highest quality; the same as rainwater.
    The issue is scale.
    Perhaps FSM could capture and use one of the boats that are probably poaching marine resources and adapt it to a water condensation production system where the boat is outfitted with storage tanks for collected water that could rapidly break down and run for cover during storms.
    If there is deep cold water near the shore then the whole system could be land based.
    The defining variables are cold water temperature and average atmospheric dew point. If the water is very cold and the average dew point quite high then it seems reasonable that scaled production is possible.
  • MrNobody95:
    Thank you for your encouragement.
    Given consumer energy prices in FSM alternative energy could be gold plated and still compete against the hydrocarbon cartel.
    FSM would be the ideal testbed for testing tidal and solar energy. I like tidal because power production can be closely approximated far out into the future and short slack tides require small storage capacity.
    Oceanic environments need hardened modular girds that operate without a hydrocarbon tether. Potable Water Production and storage fits nicely in that mix.
  • imageExcellent idea!
Sign In or Register to comment.