Home Made Hydrogenerator?

Discussion in 'OnBoard Electronics & Controls' started by Slowboat35, Jun 7, 2020.

  1. Slowboat35
    Joined: Jun 2020
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    Slowboat35 New Member

    Apologies if this has been done before, I didn't find anything with a search.

    Given the availability of small outboard parts it seems an atractive idea to replace the motor with an alternator or generator and suitably pitched prop to act as a transom mounted hydrogenerator.

    Has this been done successfully? Anyone have views on this?
     
  2. Will Gilmore
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    Will Gilmore Senior Member

    Last edited: Jun 7, 2020
  3. Yobarnacle
    Joined: Nov 2011
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    Yobarnacle Senior Member holding true course

    Towed Water Generators: Are They Worth It? - Practical Sailor https://www.practical-sailor.com/blog/towed-water-generators-are-they-worth-it.

    "One thing I did like was the apparent ease (the key word is apparent, because I did not try this at sea) with which the Duogen deployed: It is suspended over the stern like an electric outboard. In its water-gen mode, it looked very similar to the Watt & Sea hydrogenerators that Practical Sailor contributor Dan Dickison examined during the Velux 5 Ocean Race. These are now available in a cruising version, but they are expensive units, and again we have not tested them."
     
  4. Rumars
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    Rumars Senior Member

    You have to solve two problems, gearing and controlling.
    For gearing you do some tests on your chosen repeller to see loaded rpm at different speeds then transform that rpm to something usable by your chosen generator.
    Controlling depends on the generator. Conventional alternators are simple, PM alternators more complicated, the easy version beeing a controller with a diversion load.
     
  5. Will Gilmore
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    Will Gilmore Senior Member

    Our Technology | AC vs DC | Elco Motors https://www.elcomotoryachts.com/our-technology/

    How to Rewire an Electrical Motor to Generate AC Current https://sciencing.com/rewire-motor-generate-ac-current-8016485.html
    [​IMG]
    From what I've read, AC induction motors are the way to go, but you will need to add a larger blade designed for power instead of speed, to turn gears that spin the motor faster than 5% or more than its rated running speed and wire in a start capacitor to get the electromagnets charged.

    Perhaps an old dryer motor would be good to use.

    -Will (Dragonfly)
     
  6. Yobarnacle
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    Yobarnacle Senior Member holding true course

  7. gonzo
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    gonzo Senior Member

    Way too complicated. 12V alternators can be bought for less than $50.
     
    Will Gilmore likes this.
  8. Yobarnacle
    Joined: Nov 2011
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    Yobarnacle Senior Member holding true course

    Yes, you're correct, both economical and simple valid points. Moderation in all things including moderation. Sometimes you need to blow a gasket. Let it out! Get exotic. Old car alternators may once have been exotic but grandma was quite an attraction in her early days, too! LOL.
     
  9. Will Gilmore
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    Will Gilmore Senior Member

    I agree with the simple approach. It gets the job done.

    The neat thing about converting an AC motor is the possibility of having both a motor and a generator in one.

    Put a high gear ratio transmission in between the motor and the prop and you just went from powering the motor off the house bank to charging that bank while the sails and the wind are up.

    -Will (Dragonfly)
     
  10. seandepagnier
    Joined: Oct 2020
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    seandepagnier Junior Member

    I 3d printed a 16 inch repeller and it produce 0.5 amps at 2 knots tidal current with belt gear up to speed up dc brush motor.

    It is key to use a repeller not a propeller. Existing propellers do not work very efficiently at all.
     
  11. Will Gilmore
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    Will Gilmore Senior Member

    So that's what you call that thingy that uses a lifting foil shape to take energy FROM the moving fluid instead of using energy to generate drive thru lift in the fluid.
    [​IMG]
    Even the Google doesn't know that term. It kept insisting I meant impeller.

    So, for reclamation energy generation under sail, it would be best if you could change out your prop, or possibly turn it around or rotate the pitch 120 degrees?

    -Will (Dragonfly)
     
  12. DCockey
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    DCockey Senior Member

    DC motors can also be used as generators and DC motors can be use as generators. We had a 1960's vintage Cub Cadet garden tractor with a unit which served as both the starting motor and the generator. It probably was not very efficient.
     

  13. seandepagnier
    Joined: Oct 2020
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    seandepagnier Junior Member

    you can't turn the prop around to make it a repeller. You also cannot rotate the blades to change it either. You can call it an impeller or repeller whatever just don't confuse it with a standard propeller.

    To generate under sail, it's best to have a separate system with different sizes for different speeds/power needed.

    I will use a brushless motor for the generator in the future with syncronous rectification to avoid voltage drop on diodes.
     
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