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Old 22-07-2011, 13:11   #76
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Re: Electric Propulsion

There are reasons that the hybrids mentioned are successful:

* Cars. They regenerate in stop-and-go traffic for impressive city mileage. Honestly, they are unimpressive on highway mileage (I've rented the Prius a number of times). So, not applicable to cruisers.
* Cruise ships. They run MASSIVE electric systems, including AC, lots of lights, and the casino. Not applicable to most of use, though a person dedicated to AC could find value in a hybrid system (though the generator will run continuously--probably 2 underway and 1 at anchor). Mega yacht stuff.
* Submarines. Really, price is no object and the objectives are completely different. I can't see having a reactor on board and I've been on WWII subs. Irrelevant.
* Railroad engines. The low speed torque is a major benefit (irrelevant to boats) and reactive braking is great (irrelevant).

So we are generally comparing apples to hand grenades. Ridiculous comparisons.

Do I think it can make sense? I'm following the thread, but as many have pointed out, the energy math is difficult without diesel.
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Old 22-07-2011, 15:17   #77
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I can just imagine what the content of this thread would be if it was around when folks first started talking about putting steam or internal combustion engines in boats.

It'll never work because:

Fuel bunkers will take up cargo space.

What if it breaks when you are out to sea.

It's an explosion hazard.

It's never been done before.


Thank goodness someone was foolish enough to ignore the nay sayers back then.
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Old 22-07-2011, 16:14   #78
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Re: Electric Propulsion

Dick Pluta, you might want to recheck your power availability from those batteries. You are not going to get 100 ah from 100 ah batteries. Not going to happen. Most people recommend that you count on 1/3 of the rating unless you can recharge them completely, which takes a lot of time. If you can recharge them completely then you can safely use 1/2 the rating, so you are looking at 96-144 batteries. Better have a big boat.

What is the replacement cost of those batteries?

Their longevity of course depends on how many charge/discharge cycles you put them through and a number of other factors, including how often you charge them to 100% capacity.
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Old 23-07-2011, 01:14   #79
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Re: Electric Propulsion

For DeepFrz

I couldn't agree more. I was just trying to show that with the current state of battery technology the math just doesn't work. Put in allowances for CAR, usable capacity etc. and the case only gets worse. In and out of the dock or for the folks who would gladly go witn no engine at all, it might work. For me and a lot like me who may spend days under power, like going down the ICW, electric is just not happening. Picture this. You leave early in the morning with full banks. 8 hours later you drop the hook (in the dark) in that nice little anchorage with flat batteries. Spend the next day or two sitting there while the solar panel give you enough juice to do it again. Not for me.

As for the "nay sayer" issue, my thanks to those who are willing to put up with the inconvenience to get information for the future when some of the fatal defects, like batteries, have been solved. BUT the math just doesn't work. Were the people who told that guy he shouldn't go over Niagara in a barrel nay sayers?

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Old 23-07-2011, 08:55   #80
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Re: Electric Propulsion

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Originally Posted by Dick Pluta View Post
Picture this. You leave early in the morning with full banks. 8 hours later you drop the hook (in the dark) in that nice little anchorage with flat batteries. Spend the next day or two sitting there while the solar panel give you enough juice to do it again.
Well, more like spend a week there if you have 500 watts of solar, which is a lot for a mono hull but pretty doable. 500W * 6(Florida sun calc, farther north would be 5 hours) = 3kW.

Like in your example, 5-6 knots @ 50A draw * 48V * 8 hours = 19.2kW

So about 6 good sunny days at anchor, not counting other watt draws. Better hope the local LEO doesn't ask you to move the boat while you fuel up off some rich guy's back yard.

But if you're willing to only go 3 knots it gets a lot more reasonable:

3 knots @ 15A draw * 48V * 8 hours = 5.8kW

So you could make that back in your 2 days at anchor.

The above doesn't count the solar regen during the day of motoring itself, but then I'm also not counting any other systems draining power.
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Old 23-07-2011, 09:22   #81
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Re: Electric Propulsion

It's not a matter of trying it and seeing whether or not it works. All the physics is already known.

Batteries need to become more energy dense both size wise (stored energy per total powerplant volume) and weight wise (stored energy per total powerplant weight) in order to compete against Diesel.

I would love to see that happen one day because I don't like smelling or having to use diesel either.
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Old 23-07-2011, 09:47   #82
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Re: Electric Propulsion

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Originally Posted by LauderBoy View Post
But if you're willing to only go 3 knots it gets a lot more reasonable: 3 knots @ 15A draw * 48V * 8 hours = 5.8kW
Heh...3 knots on less than one horsepower. Is this possible?
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Old 23-07-2011, 10:41   #83
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Re: Electric Propulsion

I hope nobody tells my ASMO MARINE Thoosa 9000 system it won't work on 30 foot 8 ton cruising sailboat. I'm into my fourth season using electric propulsion. I'm currently finishing a week long cruise that started out with 37 miles of motor sailing as the winds were under 5 knots the whole way except for a sea breeze that kicked up two miles from my destination. As an experiment I ran under battery for over two hours turning the prop just enough (6-7 amps) to eliminate prop drag and give a little boat speed. When my battery capacity dropped to 90% from 100% from a fully charged condition I turned on the generator and adjusted the throttle so there was no draw from the battery bank and I was moving along at 3 to 4 knots. I arrived at my destination with the battery bank still at 90% capacity.
I do agree if you are only going to depend on solar for charging you will be waiting a long time to get things charged up. Might work for a day sailer once a week but, would not work for my type of sailing. Since I'm primarily at a mooring or anchor I rely on the three legged stool approach for charging. I have solar panels, 48 volt wind generator (which is currently off the boat) and a small 47 lb Honda 2000 generator for both charging my 48 volt bank, my 12 volt house bank and whenever I need to use any 120 volt power tools. I can move my 30 foot boat at 3 knots (this is without drawing any amps from the battery bank BTW) using the Honda and the Zivan NG-1 charger. Even then I'm only using 900 watts of the Honda's 1600 watt output so I operate it in ECO mode for even more fuel savings. I could add another small 48 volt power supply into the mix if I wanted to add some additional amps and speed but, don't really feel the need to spend the money. Though the nice thing about electric propulsion is you can easily up grade as the technology changes. Say if generator, battery charger or battery technology changes I could up grade them into my boat rather easily because I have EP. Once you install a diesel engine, well there you are.
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Old 23-07-2011, 16:47   #84
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Re: Electric Propulsion

Mike, I don't think anyone has said it can't be done. Some of us have said it depends on mission and up front expense.
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Old 23-07-2011, 20:33   #85
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Re: Electric Propulsion

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Originally Posted by DeepFrz View Post
Mike, I don't think anyone has said it can't be done.
Actually, that's a lie. Earlier in the thread, someone () stated the following:

Quote:
They work very well in large ships, not so well in cruising boats. They are very nice for local boating in small boats as well. Its getting that magic to work for a cruiser that, so far, has been impossible to achieve.
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Some of us have said it depends on mission and up front expense.
And just exactly how does Cpt. Mike's mission, consisting primarily of occasional coastal sailing, differ from, say, 90% of sailboat owners' missions?

Or is everybody pretty much circumnavigating?
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Old 23-07-2011, 20:57   #86
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Re: Electric Propulsion

I stand by that statement. You can't call it green with the battery bank that is required. Cpt. Mike uses a generator to recharge, so it is a hybrid solution, not a purely electrical solution. His solution uses a gasoline powered generator, larger boats I'm sure would use diesel powered generators and therein lies the rub. A diesel electric solution has so far proven to be less efficient in a "small" (I mean a cruising type sail/power boat, not a super yacht, although I haven't heard of any mega yachts successfully using diesel electric). So, where is the magic?

I personally would like to see the breakthroughs (yes, plural) that 1. batteries that are more efficient. 2. batteries that last longer 3. batteries that do not require the energy that is now needed to produce them 4. batteries that are easier to recycle
5. generators that are efficient enough to be used successfully in hybrid diesel/electric cruising boats 6. breakthrough in propeller design to make them more efficient. (I'm sure there are more items that would help make these boats cost effective)

By the way, all of the above improvements could be used quite nicely in a normal cruising boat as well. And i have always stated that solutions are highly dependent on mission.

Adamante, you might be a little more careful in choosing your words.
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Old 23-07-2011, 21:01   #87
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Re: Electric Propulsion

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Originally Posted by David M View Post
The primary problem is that the energy density (Stored energy per amount of weight) of Diesel is still much greater by many factors than the most efficient batteries. Were this not the case then we would have battery powered commercial aircraft.


Since boats are sensitive to weight and there is no way around this fact, then batteries will have to become much lighter per amount of energy stored, and not physically larger either, if it is ever going to compete equally with Diesel.
In a discussion about current auxiliary electric propulsion in sailboats, this type of energy density comparison is nothing but a red herring, so often trotted out by those who appear to be opposed to the idea simply on ideological grounds.

No one in their right mind is proposing that a cruising sailboat be equipped with electric propulsion without having a fossil-fuel generator back-up -- in addition to a deep battery bank and a relatively massive solar array.

It will likely be more expensive, but electric propulsion is all about the possibility of added flexibility and convenience, as opposed to the rigid requirements and limitations of traditional diesel systems.
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Old 23-07-2011, 21:25   #88
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Re: Electric Propulsion

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I stand by that statement. You can't call it green with the battery bank that is required. Cpt. Mike uses a generator to recharge, so it is a hybrid solution, not a purely electrical solution.
This smells like strawman argumentation.

First of all, I am not calling it "green", some other folks might be, but in my opinion electric propulsion is far from being "green". There are other factors that may make it attractive to a certain class of boaters, but being green is not one of them.

And secondly, I wasn't aware that the current discussion was limited to a "purely electrical solution", I thought we were discussing electric propulsion in sailboats in general. All of the realistic solutions I have seen so far involve some type of hybrid energy storage and production, including fossil-fuel generator back-up.

Quote:
Adamante, you might be a little more careful in choosing your words.
Which part did you find objectionable?... I believe I was simply calling attention to a couple of your statements that seemed to be contradictory. I welcome any clarification.

I would hope we all all trying to learn from each others' perspectives and not become entrenched in ideologically demagogic exchanges.
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Old 23-07-2011, 21:32   #89
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Re: Electric Propulsion

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I would hope we all all trying to learn from each others' perspectives and not become entrenched in ideologically demagogic exchanges.
Hmmm. Yes.
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Old 23-07-2011, 22:09   #90
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Re: Electric Propulsion

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Yeah, but it really doesn't. Let's look at a 4JH3E which is rated at 55.3HP(41.25kW).
Thanks for that analysis, LauderBoy.

It's fairly apparent to me that any direct comparison of the power rating of diesel vs. electric involves some relatively complex math and physics and is much more than likely to result in an endless and confusing argumentation.

So rather than a bottoms-up approach of trying to define an equation that captures all the characteristics involved, I think it might be more productive to look at actual examples of boats that have been successfully equipped with electric propulsion. In examining those configurations, it becomes apparent that as a rule of thumb, an electric propulsion motor horsepower should be sized at approximately 40% - 50% of the rated diesel engine horsepower.

Another words, if your boat is equipped with a 58 HP diesel, a minimum replacement electric motor should be 58*0.40, or a 23.2 HP electric motor, which is about 17 KW.

For those that care, there are numerous examples on the web of actual implementations in sailboats, including Lagoon, Fastcat, Nonsuch (), etc., to support this power relationship formula.
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