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Reducing the fuel consumption of ships

Georgeb

We could greatly reduce the fuel consumption and emissions of ships if we used the energy of waves. This could done by adding a pipe all the way around the ship above sea level. Water enters the pipe at the bow and exits at the stern to push the ship forward. The pipe is higher and wider at the bow than the stern. Waves force water into one way openings at the bow to give pressurised water with potential energy. This pressurised water forces jets of water out at the stern.

All the pipework is above sea level so ships could be retroftted without the need to go into dry docks. There is no change to the laminar flow of water below sea level.

The motion of the ship adds to the kinetic energy of waves. By diverting this energy around the ship we can reduce drag and fuel consumption. This would be a low cost way to reduce greenhouse gas emissions without the need for people to reduce their standards of living.

  • 0
    When a wave hits a ship it causes drag because the ship has to expend energy to push the water to the sides. If some of this water and its pressure and potential energy  is channelled to the rear to be reconverted to kinetic energy, the energy losses to the sides can be reduced. The ship has to expend the same amount of energy to push against the wave but it will recover some of the energy that is channelled to the rear rather than lost to the sides.
  • Former Community Member
    0 Former Community Member

    I'm not a naval architect, but…

    When the waves hit the bow of the ship, they are forced into constricted openings. This increases the pressure of the water (compared to a sharp bow cutting through the wave), pushing back on the ship.

    Interesting idea, but I suspect that it would create more drag than the propulsive force that it generates.

  • 0

    The last time I looked the bow of a ship was above sea level. Due to the motion of the ship,  waves will strike the ship at the pointed front end rather than the sides. Wave energy is more concentrated and available for more of the time than wind energy. The plumbing necessary to capture wave energy would be a lot cheaper than using masts and sails and would be much  easier to operate.

    Wave energy is equal parts potential energy and kinetic energy. When a wave strikes a wall such as the side of a ship the kinetic energy is transformed into pressure energy and more potential energy plus friction losses. This pressure and potential energy can be piped to the rear of the ship to be reconverted to jets of kinetic energy to push the ship forward.

    Waves have potential energy so all the pipework to capture it is above sea level. There is no impediment to flows below sea level to increase drag.

    There will be less energy lost by the ship forming bow waves.

  • Former Community Member
    0 Former Community Member

    Nuclear ships is the obvious answer.

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    now you mention it something like that has been done. But squares are not always the best shape unless you want to run from the wind.

    Ah yes, that's probably what you are thinking of.

     

  • 0

    Georgeb: 
     

    We could greatly reduce the fuel consumption and emissions of ships if we used the energy of waves…... 

    There is no change to the laminar flow of water below sea level.

    This is contradictory. If the pipe is able to take in water at the bow, it must be below the level of the water, and therefore affecting the flow of water round the hull. The amount of energy available from this would be minimal, bearing in mind the engine power required to propel the ship (for a large ship we are talking of tens of MW) and the drag would cause more losses than would be gained.

    For a small ship, the bow would pitch up with the waves and the system might not take on any water anyway.

    I think if you want to reduce fuel consumption on ships it can be done by utilising wind power. There is, after all, a correlation between the height of the waves and the power of the wind. If we were to fit tall masts on the ships with horizontal bars and hang large squares of canvas to be driven by the wind, this might work……. 

  • 0

    Do you have any evidence that this idea works ? - to demonstrate a scale model would be very interesting.

     

    Mike.

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