Diesel-electric without batteries?

Discussion in 'Hybrid' started by Red Dwarf, Feb 14, 2013.

  1. Red Dwarf
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    Red Dwarf Senior Member

    I am looking for info on a diesel electric setup as used on a train. I do not want a system with tons of batteries. Of course a small "normal" battery bank can be used for household needs but not for propulsion.

    I have googled train setups but could not find any good info on anything that might be used on a small boat.

    I am interested in details about the design of a diesel electric that uses little or no batteries between the generator and the electric motor. I would appreciate links to examples and design guidelines.

    Also, DC or AC? I have read many threads but they usually drift and I have never seen a convincing answer one way or the other. Are AC generators and motors with a variable frequency drive a good choice?
  2. Submarine Tom

    Submarine Tom Previous Member

    I can't help you but have you checked out the <endlesssphere.com> forum?

    Right up this alley.
  3. DCockey
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    DCockey Senior Member

    What power are you interested in?
  4. Number4

    Number4 Previous Member

  5. dinoa
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    dinoa Senior Member

    Most icebreakers are diesel electric powered. HDW submarines made in Kiel, Germany run as diesel electrics while surfaced or snorkeling.

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  6. CDK
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    CDK retired engineer

    Diesel electric trains come from an era where nobody cared about topics like fuel efficiency or environmental protection. Crude technology with large amounts of electrical energy derived from heat being converted to heat again and removed by fans and air ducts.

    Interesting historical stuff to read about, but you do not want any of that in your boat unless someone else pays your fuel bills. And there is no need to go that road because what you need is of another magnitude.
    The train designers already had the mechanical parts for electric propulsion, they just added the big diesel generator because lots of places could not be reached without one.

    If you want to experiment, buy a modern brushless DC motor with a switch mode controller and a modest battery. Then, once you are satisfied with its performance, add a generator/battery charger to get the range you need. It will also not be the most economical way to travel, but at least you have the advantage of silent running for a limited time.
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    FAST FRED Senior Member

    Nothing electric comes close in efficiency to a std transmission as used for about a century.

    What do you hope to gain by an electric setup?
  8. Red Dwarf
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    Red Dwarf Senior Member

    Right now this is all just conceptual design. I am researching various concept so I can verify the merits of the various concepts before I commit to any one path.

    Number4 - The diesel electric dozers are exactly the concept I am referring to, electric power without batteries. I will try and find more information, thanks for the lead.

    The reason for the interest in electrics is packaging. I am looking at very small hulls and even though there is room to mount a diesel engine there is virtually no room for inspection and maintenance. The thought of having to fix a problem at the worst possible moment (a storm) is a nightmare, and potentially fatal.

    So given the choices for a remote reliable motor are electric or hydraulic I choose electric. Hydraulic is too noisy, messy and inefficient.

    As far as power requirements I am looking at about 120-160Kw max. I intend to use multiple generators to achieve this level of power. This allows me to run only one generator for slow efficient cruise and bring others online as needed. Having, for example, 4 generators will provide the ultimate in safety with literally 3 backups. Only a fuel problem could take them all out, and there are ways of mitigating that issue. Service couldn't be easier as all will be at deck level with tons of walk around room. You could replace any generator from the outside with a forklift on the dock.

    This is an example of the type of generator I am looking at. No use of seawater at all. http://www.hardydiesel.com/perkins-generators/30-kw-perkins-generator.html

    I know many threads discuss batteries and solar panels and such but that is a huge waste of money and payload. AGM Batteries are too heavy and Lithium way too expensive for any kind of propulsion use. I can buy all 4 generators for less money than a bank of Lithium batteries with enough capacity to provide power for only a few hours.

    I can see using the generator only solution for 5-10 years and maybe by then solar panels and batteries will have advanced enough to justify the cost and installation. Being that the boat is already electric powered it won't be a major rebuild to incorporate solar panels and batteries.

    A big issue is efficiency. One gallon of diesel will make about 20 Hp and a direct drive setup will get about 95% of that too the prop.

    So how much electrical power can I get to the prop? If I can hit 85% that is awesome, but I think 80% is realistic. I need to learn more about the merits of AC or DC power. A plus for AC is the generators are readily available and inexpensive.

    So if I end up with a 10-15% hit in fuel use I can accept that for the other benefits of the diesel-electric setup.

    But, as I said this is all conceptual, please tell me where I am wrong and I appreciate any constructive help.

    Edit- I forgot to mention a factor to efficiency is the ability to run at low throttle settings. How efficient will a 200Hp diesel be when I only want idle Hp from it for days and days? My guess is it will burn too much fuel and lead to an early death of the engine. With the diesel electric the 30 Kw generator will happily and efficiently provide 20-30 Hp for low speed cruising. I think if you look at the whole package the diesel electric will overall come out costing less to run per year. I am working on a spreadsheet to verify this and will post it when finished.
  9. michael pierzga
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    michael pierzga Senior Member

  10. DCockey
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    DCockey Senior Member

    Variable speed controllers which use standard AC power and motors from fractional horsepower to several hundred horsepower are available "off the shelf" for industrial use. http://www.driveswarehouse.com/?gclid=CMnQuev3uLUCFexaMgodAygAeg I don't know what modifications, if any, would be needed for marine applications.

    Two technologies are available. One uses DC motors. The other uses three-phase AC motors with variable frequency control.


    It should be possible to power either type of system with a commercially available Diesel generator set.
    Last edited: Feb 15, 2013
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  11. Red Dwarf
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    Red Dwarf Senior Member

    DCockey - thanks, those are excellent references.

    Another aspect of efficiency I forgot to mention is shaft angle. With electric motors the shafts will be horizontal. That can make up for half the drive efficiency loss compared to a direct diesel 8 degree shaft angle which is accepted. If you ask yourself why do people accept an 8 degree shaft angle the answer is packaging, the engine won't fit with a horizontal shaft.
  12. Number4

    Number4 Previous Member

    Attached Files:

  13. WestVanHan
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    WestVanHan Not a Senior Member

    Trains use DE for the seamless power transfer from 0 to maximum speed-the only reason why.

    You can't compare a car to a boat either..on the highway the hybrid cars get poorer mpg than a similar one with a stick.In the city they can recoup some energy-boat can't do that.

    Ice breakers use them for instant reversal,though a CPP can do that, and for electric heating of large areas that will ice up and maybe capsize a vessel-what I've read.

    There's tons of threads on this-if you want to spend money and get poorer fuel economy,go ahead.

  14. MaV
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    MaV New Member

    DE is used in vehicles where loads and speed varry most of the time.
    Like tugs and freight trains.
    This is not the case with most recreational boats, the trottel is probably 80% or more in the same position.
    DE and hybrid are more efficiƫnt with some type of use, even battery powerd can be the best choise.

    Peronly i like the idea of 3 (or 4) generators, 1 (or 2) main verry effetiant generator and 1 or 2 less expensieve units fore high speed and back upp.

  15. El_Guero

    El_Guero Previous Member

    That is NOT TRUE.

    From pure efficiency, diesel electric should easily approach, or exceed direct drive (transmission).

    The difference is COST ....
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