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Charged Superhydrophobic Condenser Surface May Make Power Plants More Efficient 72

Posted by Soulskill
from the making-water-dance-to-our-tune dept.
New submitter _0xd0ad sends this news from the CS Monitor: "The activities of bantam water droplets in just one region of a power plant could make a significant difference in the output of power plants, scientists say. ... When a water droplet forms on a sheet of metal coated with a superhydrophobe, the droplet can camp there only so long as it does not merge with another droplet. As soon as it weds with another droplet, the energy produced is so great that the two will 'jump' away from that surface, as if in urgent deference to the surface's severe water phobia. Scientists have proposed that this 'jumping' could be incorporated into power plant design. ... 'To have the most efficient condensing surface, you want to remove the droplets as early as possible,' says Dr. Nenad Miljkovic, [postdoctoral associate at MIT and co-author on 'Electrostatic charging of jumping droplets']. But, in prototypes, this 'jumping' design is not as efficient as engineers believe it could be. Some of the droplets will just fall back to the condenser's surface, recoating it and slowing the process down. ... But a newly discovered component to the 'jumping' process might allow scientists to eliminate this fall back. In an accidental find, the MIT team found that droplets don't just spring from the surface — they also rebound from each other ... because an electrical charge forms on the droplets as they flee the hydrophobic surface. So, if a charge is applied to the condenser system, the water droplets can be electrically prevented from returning to the surface, he said.
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Charged Superhydrophobic Condenser Surface May Make Power Plants More Efficient

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  • by Anonymous Coward

    This allows condensers to have a smaller area.

    FINALLY!

    • by MightyYar (622222)

      Smaller area means less water means smaller pump means less wasted electricity means higher plant efficiency.

  • by Anonymous Coward

    Sounds like Star Trek technobabble.

    • by dbIII (701233)
      That's what you get for watching more Trek than reading about science and technology.
    • Nah it sounds like they need an electrostatic deflector array. Just invert the polarity and add in a magnetic flux transducer coil and voila, you'll be able to achieve an efficiency rating of 93.6%, easy.

      Sheesh, were you asleep in your engineering classes?

  • Claification (Score:5, Informative)

    by Anonymous Coward on Friday October 04, 2013 @04:13PM (#45039003)

    The efficiency that is mentioned is water recovery/usage efficiency, not electrical efficiency. In this case a power plant would use more electrical energy to produce the condensation. This is still good news in that it could reduce water usage which is a big issue with power plants in the water starved west.

    • by mlts (1038732) *

      Not just water, anything with a HVAC system, assuming this technology worked on other refrigerants.

    • Re:Claification (Score:5, Interesting)

      by bobbied (2522392) on Friday October 04, 2013 @04:22PM (#45039081)

      The way I read this it was about heat transfer. If you can get the water droplets off the "cold" side sooner, you don't have to transfer heat through them. So you want the condensed liquid to go away so you can keep as much surface area in contact with the vapor as possible.

      I'm not sure how this makes a closed system more water efficient.

      • Scale (Score:2, Insightful)

        by justthinkit (954982)
        You know what kills heat transfer? Scale. This system will die (i.e. drop to not so fancy smancy levels) as soon as the scale builds up.
        - a chem. eng.
        • by swillden (191260)

          You know what kills heat transfer? Scale. This system will die (i.e. drop to not so fancy smancy levels) as soon as the scale builds up. - a chem. eng.

          Will scale accumulate on superhydrophobic surfaces? I would think the water should move off the surface too fast to evaporate.

          • Re: (Score:2, Insightful)

            by justthinkit (954982)
            All I can give is an intuitive answer -- I think this surface doesn't stand a chance. Surfaces don't stay superhydrophobic or super anything. Things get shut down and serviced but corrosion never sleeps.
            • by dbIII (701233)
              There's buggerall corrosion on the boiler side of condensers. There so little that tiny amounts of ammonia in condensate dripping on tubes is seen as a massive deal when it happens.
      • Sub-cooling (Score:5, Informative)

        by Tokolosh (1256448) on Friday October 04, 2013 @05:12PM (#45039511)

        For any particular pressure (or vacuum) there is an associated dewpoint temperature. In this case, it is where the liquid water condenses from the steam. Condensers use cooling water to remove the heat of condensation and subcooling. Cooling water is often cooled by evaporating some of the cooling water in cooling towers, so that fresh makeup water is needed. The steam condensate is recycled to the boiler to be heated and vaporized back to steam to power the generator turbine.

        However, the condensed water adhering to the condenser tubes is further sub-cooled below its dewpoint. This means that more cooling water is needed, more condenser surface area, and more energy to reheat and vaporize condensate back to steam.

        I speculate that the technology described reduces the amount of condensate subcooling, leading to less cooling and heating duty, improving overall efficiency.

      • I agree, no where does it mention that increased condensation is something that will be achieved or water efficiency itself will be increased, its only discussing the efficiency of the heat transport process. I read the article to figure out what he was talking about....and they did talk about a second application that does mention condensation as a power source.

        But the finding also suggests another possible new application, Miljkovic says: By placing two parallel metal plates out in the open, with

  • What? (Score:1, Insightful)

    by Anonymous Coward

    No, sorry OP, you're gonna need to spell out exactly why it'll make things more efficient. Start from the assumption I don't know what a 'bantam' water droplet is, cos, as far as I understand it, powerplants make electricity by heating up water into steam (via coal/gas/nuclear/whatever) then expanding it through turbines to spin generators. Where, in that process, does this efficiency gain come in? Where is this 'sheet of metal' that drops are forming on? What drops? Why are they forming there? How is stopp

    • After going through the turbine, the steam is condensated to water, creating vacuum at the turbine "output", and thus increasing its efficiency. That's why improving condensation improves the turbine efficiency as well.
      • I just got to tour a power plant - very interesting! The running units were all combined cycle (close to 60% thermal efficiency), and the volume difference on steam in/steam out is really tremendous! The steam was vacuumed out of the LP turbine. And they were complaining about their cooling/condensing system not being efficient enough in the summer to run the plant at full power. Interesting too that the vast majority of the plant was about steam generation/handling/reheating/processing. The turbines a
        • Yes, after all these years we're still running on steam. Everything we are and do is based on the interaction between the water and the sun.

          • In a combined cycle plant, steam is the mechanism, like gears or levers. The original fuel is natural gas. Burn that in a gas turbine, spin a generator for electricity. Use the exhaust heat to create steam - run the steam through a steam turbine to spin another generator to make even more electricity. This results in very cool steam (barely steam at all), run this through a cooling system to get water which is cycled back into the exhaust stream to be converted to steam, etc etc.

            Steam is just a convenie
            • and where did the natural gas come from? Dead plants... covered over my erosion caused by weather patterns... all water and sun my friend.

              I wasn't denigrating steam. I've a small DIY steam engine myself and take my kid to a steam engine fair every fall. It's a great technology. I plan on building a larger one some day to power a generator as literally any fuel will work to heat it and there-by generate electricity.

    • Re:What? (Score:5, Informative)

      by bobbied (2522392) on Friday October 04, 2013 @04:38PM (#45039179)

      Yea, the OP did make some assumptions about the understanding of the reader and basic heat engine operations.

      Most power plants have a boiler that converts the working fluid to a gas. This gas is piped at high pressure though a turbine which drives a generator. This lowers the temperature and pressure of the gas which is then sent to a condenser where the gas is converted back to a liquid. This liquid is pumped into the boiler and the cycle starts over.

      What they are talking about is the place where they take the working fluid from a low pressure gas to a liquid by removing heat. This takes place in a condenser. A condenser has cold surfaces that are exposed to the low pressure vapor. These cold surfaces have liquid condense on them that then runs off to be pumped back into the boiler. Apparently being able to get the liquid off the cold surfaces quickly makes the transfer of heat more efficient and faster.

      Of course, the real question about their theory here is if the process they claim can be engineered to happen and provide more energy savings than it consumes. So far they have not been very successful doing this on an industrial scale.

      • Re: (Score:1, Informative)

        by Anonymous Coward

        Apparently being able to get the liquid off the cold surfaces quickly makes the transfer of heat more efficient and faster.

        You got it exactly wrong. Being able to get the liquid off the cold durfaces quickly stops the transfer of heat to liquid that has already condensated. The warmer the liquid getting out is, the less heat you need to revaporize it. And the less energy you need for cooling the condenser. It has done its job once it produces liquid. Cooling liquid is a waste of energy: its purpose is to cool vapor.

      • Re:What? (Score:4, Informative)

        by marcosdumay (620877) <marcosdumay.gmail@com> on Friday October 04, 2013 @05:24PM (#45039613) Homepage Journal

        Another small detail to add to your comment. The faster you turn the vapor into liquid, the lowest is the pressure at the condenser, reducing the work of the pump that creates vacuum after the turbine* and increasing the overall efficiency of the system.

        Also, if you have a bigger heat conductivity, you can apply a smaller temperature gradient into the vapour. That could theoreticaly improve the efficiency, but I don't know how that part works in practice.

        * Yes, the vapor goes from the turbine into a pump. Seems counterintuitive, but you want to condense it, what is easier to do in a highter pressure, but the turbine works much better with vacuum... In the end big plants gain efficiency by putting some work back into the steam.

  • Conversely it would be better if the outside of beer glasses were more hydrophilic, because the longer every drop of water can be delayed from rolling off the surface and leaving more room for condensation to take place, the more time we would have to drink the beer at a suitably low temperature.
    • by Dishevel (1105119)

      Conversely it would be better if the outside of beer glasses were more hydrophilic, because the longer every drop of water can be delayed from rolling off the surface and leaving more room for condensation to take place, the more time we would have to drink the beer at a suitably low temperature.

      Beer cozy?

    • You know, most people solve that by using a smaller glass. An insulating one is normaly a good enough second option (but it's nice to feel the glass temperature).

      Discovering a more hydrophilic material that's a worse heat conductor than glass looks like a huge enterprize for too small a gain.

    • Have a G&T with ice.
      The ice keeps it cold and it doesn't taste like beer. Double bonus.

  • by Animats (122034) on Friday October 04, 2013 @04:58PM (#45039389) Homepage

    Super-hydrophobic coatings are now easily available. [homedepot.com] They work very well when new, but customers complain about the coating wearing off rapidly. Something with a more durable bond will be needed.

    This is yet another of those materials science articles which jumps from "minor discovery in materials science" to "huge commercial breakthrough Real Soon Now." It's bad for MIT's reputation that they put out so much hype.

  • Would a coating like this help lower the weight of water clinging to the inside of an insulated steam balloon?

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