diesel electric for 70-100ft boats? 200-300 hp equiv

Discussion in 'Boat Design' started by aktxyz123, Aug 24, 2020.

  1. aktxyz123
    Joined: Aug 2020
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    aktxyz123 Junior Member

    It seems that all the pod'ish diesel electric systems are currently for larger boats or ships, like the Volvo IPS or the Veth L Drive.

    Has anyone tried to use one of these in a "smaller" boat ... around 70-90ft?
     
  2. bajansailor
    Joined: Oct 2007
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    bajansailor Marine Surveyor

  3. aktxyz123
    Joined: Aug 2020
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    aktxyz123 Junior Member

    that is the cutest tug ever ... looks like it should be in a cartoon
     
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  4. gonzo
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    gonzo Senior Member

    Considering the losses on converting diesel generated power into electric, and then electric into mechanical, you will need about 215 - 325 HP of power.
     
  5. aktxyz123
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    aktxyz123 Junior Member

    thanks, I was wondering what the general losses were in the extra step ... sounds like a bit less than 10% in general?

    from a fuel standpoint, is the difference offset much by things like being able to always run the diesel at a constant/optimum speed? not needing a separate diesel for the genset? and any other things I am not thinking of
     
  6. gonzo
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    gonzo Senior Member

    The extra initial cost and maintenance. There is a weight penalty too. It works for some applications. For example, I worked on survey ships where speed control was critical. If the plan is to run the diesel at a constant speed it is possible to simply size it properly. Diesel electric works well when there are a bank of generators. The load determines how many generators are running simultaneously.
     
  7. SamSam
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    SamSam Senior Member

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  8. philSweet
    Joined: May 2008
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    Location: Beaufort, SC and H'ville, NC

    philSweet Senior Member

    Transfluid has some commercial hybrid offerings, and one dedicated E drive -

    [​IMG]
    [​IMG]

    Electric Propulsion System - Marine - EPS - Transfluid https://www.transfluid.eu/en/product/eps-marine-system/

    They also have hybrid HM series transmissions that can handle up to 400hp of electric input and output ( 4 x 100hp pto/pti), and up to 1100kW of diesel. Smaller units are available. These hybrid systems seem to be sorting out such that the electric machine power is 20% to 30% of the diesel power.

    Yanmar is advertising a 400hp hybrid paired with some Transfluid kit.

    These have integrated control and management systems, which has long been the bugbear with these systems.
     
  9. Squidly-Diddly
    Joined: Sep 2007
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    Squidly-Diddly Senior Member

    "These have integrated control and management systems, which has long been the bugbear with these systems." Why not adapt a well proven and recently upgraded system with already a billion dollars and decades of IC and MS perfection built in, with all sorts of bells and whistles like Radar Cruise Control, and after market $1000 add on Full Self Driving (just hook the electric steering to the rudder, might need to make a little diorama of a road for the camera to look at, sitting on a big compass lol) ?

    I'm thinking my Prius Prime would be nice system to convert for boat use, mostly because it would be neat to be able to cruise at low speed without the motor running. I did read somewhere they were thinking about diesel Prius but haven't heard since. Prime is rated at 121hp when engine (direct to mechanical CVT) and two electric motors are combined, so two Prime Drive Trains would be in your ballpark. You could rig it so you run either both engines, or one engine, or "EV Mode" but still drive two props. Or put two PDT on one shaft. The idea would be to find cheap PDT from wrecked Primes, since there wont be a market for these newer units as replacements for worn out cars for a few years still. To adapt a FWD unit to prop shaft I guess you could run the prop shaft parallel to the FWD shafts and place a gear between them so both FWD shafts think they are on a straight road. If it was a motor-sailor you'd have re-generative power when under sail. :) Prime can use its big traction battery for AC household voltage but only for Japanese market :( (so I guess its 220). Current Prius engines are rated at over 40% thermal efficiency, so I guess that is why they aren't doing diesels.

    No reason you couldn't make custom water-jacket exhaust, once out of the car.

    I'd guess you could get complete Prime drive train from wreck for about $10-15K, which is peanuts.

    UPDATE: 2018 Prius Primes with "rear end damage"(barely AFAIK) and 24K miles going for $5K! Given you could get maybe $1000 or more for rest of car minus engine that is practically FREE! Damaged Toyota Prius Prime Car For Sale And Auction | Jtdkarfp8J3074801 https://erepairables.com/salvage-cars-auction/toyota/prius+prime/vid-43487518

    SO, given there would be SOME learning curve and initial investment to converting a Prime into marine application, but the Primes are practically free, it would make more sense to use at least two, but why not 4 or 6? Especially if they can be rigged on a common shaft turning a big boat's big prop at widely varying power levels. If one or more units crap out, you'd still have others on the shaft. I think you'd have better luck finding totaled rear ended Primes for sale on distant shores than getting Marine diesel-elec units from Germany or Norway.
     

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    Last edited: Aug 26, 2020
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  10. JSL
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    JSL Senior Member

    Not sure if I am correct but I believe Steyre ( Austria) marine has off the shelf diesel/electric engines. Electric is less power for auxiliary cruising in the quiet zones.
     
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