Re: Electric/Diesel Hybrid Cat Proposal

["Peter VanDerWal" <peter_vanderwal@msn.com>]

>My proposal is that we collect some information . . . and then I could go
>off to see how I could apply it to the
>boat I am building, a 60 foot powered displacement catamaran.  The goal
>would be to be able to turn the props with electrical power from a bank of
>batteries.  What I am interested in is determining how much range I could
>reasonably get out of such a set up.  I understand that it could never be
>enough to make passages, but perhaps it is possible for the time spent in
>coastal cruising.  Then for passages, it would be necessary to supplement
>the energy stored in the batteries with energy stored in the diesel fuel
>tanks in a hybrid fashion.


-snip-

>where I plan to be at for coastal operations.  All power ratings are at the
>propeller shaft.  Right now, I'm trying to decide if I want the ability to
>put more than 200 hp total to the two shafts; since that is what I need for
>the 12 knot objective for coastal operations.


While this sounds like an exciting project,  I'm not sure if it's feasible.
I did a few quick calculations and I'd like to get the list's opinion on
whether I got them right or not.

He's looking at producing up to 200 hp continuous and I'll assume he'd like
to go for at least 2 hours.
Assuming that the motor is 90% efficient and the controller is 95% (and
ignoring losses in cabling etc.)
he's going to need about 174kw from the batteries or about 348 kwh (2 hours)

If we use 168 volts, that's about 1035 amps (continuous - yikes!)
If we use optima YTs he'll need about 560 (?) of them.  Those will weigh
about 12.6 tons!
I'm going to guess that a motor(s) that can produce 200hp continuous, plus
controller, plus assosiated wiring, contactors, fuses etc. will weigh around
3/4 to 1 ton.

The boat is only projected to displace 30 tons with the fuel tanks empty,
it's going to be quite a challenge to fit 13.5 tons of electric drive system
in there.

Of course he could alway use NiCads, they'd only weight about 8 tons for a
total weight of 8.5 to 9 tons.
Or if he could get some of those lithium-poly batteries....