Hi
Diesel electric drives on large ships are not for propulsion fuel
efficiency.
They are for ease of manoeuvring and in passenger ships, with large house
loads, there are advantages in placement and generator use.
The most fuel efficient setup is a large slow revving direct drive diesel.
I cannot think of a case in small boats where hybrid propulsion would save
fuel unless you have solar, wind or regen while sailing.
Unlike a car you cannot recover energy from braking.
-----Original Message-----
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com]
On Behalf Of Eric
Sent: Monday, 8 November 2010 7:53 a.m.
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Re: house boat + hybrid
John,
You have made my point exactly. Would I operate a sailboat with an ICE and
a 1 gallon tank? Yes. Would I operate a 40' ICE houseboat with a 3 gallon
gas tank? Absolutely not. Would I build a ski boat with a 2 gallon gas
tank? Nope.
For power boats, the power requirements are typically too high and the
electric "tanks" are too heavy for driving range that goes past tens of
minutes. While sailboaters are used to slow speeds, very few people buy a
power boat to motor along at 4 kts. For most power boaters, 8 to 10kts is
consdiered a slow boat.
You don't have to convince me about how sailboats are appropriate candidates
for electric power. But not all sailboats. My F-27 Trimaran has a new 9.8
HP outboard. I could have converted to electric. But the whole outboard
driveline with enough fuel to motor over 40nm weighs less than 2 group 31
batteries. Since weight is very critical on this boat, I could not "afford"
the extra weight. That type of motoring range is a safety requirement for
offshore racing, I wouldn't be allowed to race without it. So no electric
drive for my trimaran
On the other hand, I am already converting my 1964 Cheoy Lee Bermuda 30
ketch to electric using a system from Propulsion Marine in Santa Barbara.
Their product, like many other 5-6kW systems available from other vendors,
is a direct drop-in replacement for an Atomic 4 for sailboat installations.
However, they are not good replacements for boats like the old A4 powered
speed launch in my marina. Completely different use cases and duty cycles.
As for hybrids in pleasure boats, for me the positives don't outweigh the
negatives. If I had a perfectly functional deisel drive, then I wouldn't
add the weight and complexity of an additional electric drive for occasional
use. But that is for how I use my boat. For other people, it may make more
sense.
And for all of the people expounding the efficiencies of deisel-electric
drives, it is a matter of scale. Container ships, Cruise lines and
railroads can all take advantage of turbo diesel 2 stroke engines that are
bigger than an RV and operate at close to 60% thermal efficiency. But have
you seen any deisel-electric semi trucks? If it could be made to work more
effeciently than a regular deisel driveline, you would see them everywhere.
Now try to make them even smaller and lighter, to something that would fit
in a pleasure boat. Some ideas don't scale down so well.
So the bottom line is that I use the gas tank analogy to do the 15 second
feasability analysis when someone talks about converting to electric. If it
seems like the idea is not even close to working, no amount of calculations
or creative engineering is going to change that.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "John Green" <v_2jgree@...> wrote:
>
> Eric, Good points.
> Now, do the same musing regarding a sailboat, and the whole thing
changes....
> The way to make electric power take off, is for a company with foresight
to produce the "New Atomic 4" of electric systems. A unit that could be sold
to boat builders. Then for a houseboat application, just double up on the
units....
> The point is good though Eric, electric is like ICE except that the gas
tank costs more than the engine...
>
> John
>
> Posted by: "Eric" ewdysar@... ewdysar
> Date: Fri Nov 5, 2010 5:42 pm ((PDT))
>
> Capt. Bill,
>
> You might want to look at this from another direction. 500 pounds of
> Lead/Acid batteries (10kWh) is equivalent to less than 1 gallon of
> gasoline, already adjusted for the increased efficiency of electric
> drive. (1 gallon of gasoline = 33kWh) These batteries will cost about
> $1200.
>
> So if you add 1000 pounds of batteries to your boat ($2500) you've got
> an electric gas tank that holds the equivalent of about 1 3/4 gallons.
> How far will your houseboat run on that size tank? A full ton of
> batteries ($5000) will last almost as long as 3 1/2 gallons through
> the ICE that drives the boat today....
>
> Even for a hybrid, the math stays the same for "silent running" mode.
> The battery bank with an electric motor is just like a little gas
> tank with an ICE drive.
>
> Fair winds,
> Eric
> Marina del Rey, CA
>
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