I agree. The efficiency of diesel-electric drive systems is economy of scale. They have to be HUGE to work. Ever seen an 8 cylinder inline stationary diesel engine with 11" cylinders? (Caterpillar makes them in my home town.) They are a great setup for ferries with azipods.
--- In electricboats@yahoogroups.com, "Eric" <ewdysar@...> wrote:
>
> Hi Kerry,
>
> So what you're saying is that installing a diesel-electric hybrid for purpose of gaining efficiency is a non starter becuase diesel alone is more efficient. I'm on board with that. I've never been a supporter of hybrids in our size boats, except in very specific use cases that aren't focused on efficiency.
>
> I have heard that the most efficient internal combustion engines are giant (bigger than my 30' ketch) turbocharged 2 stroke diesels like this one.
> http://www.gizmag.com/go/3263/
> This type of engine exceeds 50% thermal efficiency, but I can't see putting one in a sailboat... :)
>
> Fair winds,
> Eric
> Marina del Rey, CA
>
> --- In electricboats@yahoogroups.com, "Kerry Thomas" <kjthomas@> wrote:
> >
> > Hi
> >
> > Not really correct. For a given constant speed application diesel alone is
> > more efficient.
> >
> > Diesel electric drives are used for controllability in electric locomotives
> > and ships that do a lot of port calls. On passenger ships and submarines
> > they are used because generating capacity is just as important as
> > propulsion. In the past they were also used as a gearbox because the gearing
> > for really large ships engines did not exist.
> >
> > Now, the most efficient ships propulsion are very large direct drive
> > diesels.
> >
> > In yacht sized power plants it would be very rare to gain efficiency by
> > adding an electric motor between the diesel and the propeller. Of course you
> > can have other valid reasons for doing so. Silent running. Weight
> > distribution, Regen etc.
> >
>
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