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  #31  
Old 04-27-2008
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I find it interesting that a pro-electric-propulsion side prefers to talk about perception, rather than provide any numbers. I am sure that means something, but I can't quite put my finger on it
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  #32  
Old 04-27-2008
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Quote:
Originally Posted by brak View Post
I find it interesting that a pro-electric-propulsion side prefers to talk about perception, rather than provide any numbers. I am sure that means something, but I can't quite put my finger on it

We never got there. People haven't got past the point of understanding that these systems are already proven, used for over 100yrs, used in most of industry (including the shipping industry) and used every single day in everything from trains to the car down their street.

It is a very long way from that to talking about the numbers. Those numbers are not can it be done but is it cost effective to use on such a small scale as a 5 ton sailboat. It seems so given the success of the 420 Cat but is it for a conversion? Maybe.

Still talking about how impossible such systems are preclude any discussions about numbers. At least numbers of value. Look at the numbers used so far, they mean nothing. When people refuse to even read the link explaining the reality of such systems it is safe to say that posting numbers is best saved for another thread.

Maybe start another thread? It is going to be hard to get this one to be taken serious.
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  #33  
Old 04-27-2008
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Quote:
Originally Posted by Architeuthis View Post
This was actually a very informative thread. Not so much about technology but how it is perceived. Thanks.
Interesting comment.

I agree.

Intelligent people can see a sales pitch of an, shall I say, 'undeveloped product', when it hits them in the face.
If it doesn't actually work more efficiently than current technology, it doesn't have a hope.

Keep working on it, and get back to me in a few years.
Good luck.
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  #34  
Old 04-27-2008
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Ok, more wishy-washy stuff, no numbers still. I am not aware of any significant number of large ships that use battery-stored electricity as their source of energy, but perhaps you can point me in the right direction.

I would also be interested to see a simple and specific example or proposal on powering a small craft (such as an average sailboat) using electric propulsion with battery stored energy, for a realistic use profile.
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BTW, it looks like lithium-ion batteries may not be much better in terms of energy density. A search on the web revealed a company that makes large capacity li-ion batteries.
A 15v 160 amp-hour battery weights about 38 lbs. Thats not too different from similar lead-acid battery (perhaps a little more, actually).
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Hybrid power is a solution looking for a problem. The technology as applied to sailboats, needs time to mature at the very least. Yes, diesel subs and EMD offshore supply boats have been around for ages but the technology as applied to sailboats is very new. Diesel subs could only stay under water for so long, and then they had to return to the surface so their batteries could be recharged by a diesel engine. Ice breakers, locomotives and offshore supply vessels that use EMD systems have very large diesel engines attached to a very large generator whichis then attached to a very large propulsion motor...which amounts to a large percentage of a vessels displacement and a subsequent loss energy as heat energy. The application for sailing yachts is very different from the previous applications and this is the critical difference.

Converting mechanical energy to electrical energy, to then be used or stored and then converted back to mechanical energy is inherently very inefficient. Each time energy is converted, part of that energy is lost as heat energy. Even if a boat could be run purely off solar and wind energy, one must consider the increased number of batteries in terms of additional weight added to the boat and pollution to the environment in the process of making those batteries.

Another factor is sustained cruising, where within a 24 hour period, with a hybrid boat you are limited to the generators output minus your shipboard loads, minus the inefficiencies. Hey, stuff happens and the iron jenny becomes necessary for hours and sometimes days. An eight kW generator is the equivalent of 10.8 horsepower minus any inefficiencies in converting watts to mechanical energy and minus the shipboard load. With a 20 kW generator, the equivalent horsepower is 27.2 horsepower. Is it feasible to place a 20 kW generator aboard a sail boat that only needs less than a 27 horsepower engine for its propulsion?
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  #37  
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Arch...

Start another thread.

Start it with the battery calculations.
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Old 04-28-2008
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Forgive me for not wanting to see this thread die....

I can't help thinking the discussion missed certain marks.

1. A boat does not have to cross the Atlantic to be good for it's intended purpose.

2. Some people just sail for fun. It's not always a fight to the death with the elements to test ones manhood.

3. Typical sailboat usage is a truly IDEAL application for electric propulsion. We fire up the motor, leave the dock, raise the sails, turn off the motor- repeat in reverse. Leave boat at pier for several days to recharge. For a lot of people a golf cart motor would be great.

4. The advantages to a successful electric propulsion system are so incredible it is certainly worth a considerable effort to make it work-
a. instant start
b. almost no winterization
c. QUIET - (sneaking out of the marina a 0500 without annoying the livaboards)

5. Many of the above argument was based on a comparison to large diesel/electric systems but that's not what we are talking about. This would be a primarily electric system with a small motor to recharge the battery bank for extended motoring. Many people would not need the motor.

6. For all the pro and con arguments presented- where is the guy who bought the system and can now say if it does or does not work? I'm thinking maybe this exchange was so hostile that guy chose not to participate.

Perhaps my perspective comes from the advantage of being unencumbered by knowledge or experience.
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  #39  
Old 04-28-2008
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hertford...right...in and out of the harbor on the weekends is an ideal application though not without its problems as well. We were arguing about cruising applications and regenerative power of passive sources...not whether short term "18 holes and recharge at the dock" uses are practical.
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  #40  
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Rockter will become famous soon enough
But you will not get extended motoring without a huge battery bank.
What is meant by "extended motoring"?
Just one hour motoring on my ship would, I reckon, ask me for about 1900 Ahr.
From where will I get that?
My engine uses one gallon of diesel by comparison.
One hour is not very long in this game.
The idea that a reversible reaction in a battery can compete with the violence of diesel combustion is dream land. It cannot. There is simply so much more energy in the diesel combustion. A gallon of it weighs about 7 lb. What does 1900 Ah of battery weigh?, and that's for one hour only.
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