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Old 29-06-2016, 05:49   #76
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Re: Why not electric engine powered boats

Relax about 50% throttle vs 50% of power.


I haven't put it on a dyno to test but I would estimate it's putting out around 12hp to make 80% of hull speed. (sister ship with 15hp, uses around 80% throttle for similar speed in calm conditions).


Even if it's only 6-8hp, that's still drastically more than the 2.5hp the generator can produce continuously. Yeah, some people have larger generators but those usually come with larger boats that have larger propulsion engines, so the effect is the same:
- A generator sized for house loads will be too small for propulsion.
- A generator sized for propulsion will be inefficient for house loads.


It's only in bizzaro world where 2kt speed capability or skulling a 40' boat is described as just as capable as a propulsion system that can cruise at hull speed all day long.
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Old 29-06-2016, 07:04   #77
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Re: Why not electric engine powered boats

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Originally Posted by skipmac View Post
OK, this has reached point of tedious and silly. Are you really seriously suggesting blocking a major road would be a good thing and might save lives?
It sure would be a good thing to block a major highway for several reasons.

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On average in 2012, 92 people were killed on the roadways of the U.S. each day, in 30,800 fatal crashes during the year.
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An the Colregs do not specify a minimum size vessel where constrained by draft applies. It is constrained by "draft" not length or size.
Then it wouldn't apply in the ICW between 2 typical sail boats as both have similar draft. If you are going to say you have right of way with a 5ft draft over a boat with a 4ft draft it's crazy because there is no way to know by looking at the other boat wo has the deeper draft. Maybe you can ask on the radio?

The channel is already 12 ft deep, so one of the boats would have to be huge and have a draft approaching this.

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I've answered every single question and addressed every single issue you've raised and you continue to ignore half of what I say and talk in circles around the rest. It appears to me that you only want to prolong and provoke with no wish to actually learn.
By "learn" you mean changing my opinion from not accepting burning fuel as reasonable, to your opinion, that it is reasonable as a "convenience" even when it isn't more convenient and is literally burning the world. Then yes, I don't want to "learn" from you.
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Obviously getting nowhere and I've got some family matters to deal with so enjoy the thread.
I have worn you out; fair enough.
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Old 29-06-2016, 07:24   #78
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Re: Why not electric engine powered boats

Funny how simple minded some people are not thinking about the consequences but only how it impacts them directly.


Surface streets have crash rates literally 50 times higher than major freeways...so if you make a habit of blocking major freeways, what do people think will happen to crashes when traffic is forced off the major freeways? Also, how will that help when granny has a heart attack and it takes 3hrs to get her to the emergency room because some idiot blocked the road?


Also the colregs are very specific in that they don't give "right of way" as many misinformed sailors assume. If your tacking back and forth forces other boats of similar size out of the channel, you will be at fault. Many parts of the ICW have significant currents...particularly in narrow sections...expecting other vessels to idle while you block off the channel can cause these vessels to lose steerage and put them at risk of drifting out of the channel...invoking the constrained by draft clause of the colregs. In a channel with a current, an upstream boat is generally responsible for getting out of the way of downstream boats.


Even if it wasn't against the colregs, what would someone say if unsafe boats were towed to deep water (when the owner goes ashore) and sunk because someone decided to take it upon themselves to fix what they thought was a problem. Not much different from intentionally blocking channels because they don't care about how it affects others.


Really ironic that someone is complaining about petroleum product usage while ridding around on a few tons of petroleum products.
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Old 29-06-2016, 17:04   #79
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Re: Why not electric engine powered boats

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Originally Posted by StuM View Post
The math is quite straightforward.

1HP = 745.7 Watts.

25HP = 18.6 kW
50 HP = 37.3 kW

9kW = 12HP

That is, of course, ignoring other factors such as efficiency. Is it more efficient to directly drive a prop from a diesel engine or is it more efficient to generate electricity with a diesel engine and use the electricity to drive a prop?
So you'd need an 18kw genny to run a 24 hp electric motor, and 36 kw genset to run a 48 hp electric.
Hmm.
Don't know about efficiency. How big is an 18 kw generator? How much fuel an hour does it use? And then to, if your running a lot of solar and wind then you would have that helping too.
So I don't know how efficient it would be, I would think it would be smaller than a 25 hp diesel engine, but I don't know. It is interesting though.
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Old 29-06-2016, 17:16   #80
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Re: Why not electric engine powered boats

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If I am sailing or rowing and you are motoring I have right of way, you better stay out of my way.

Not to be an ass, but if you're tacking up a narrow channel, and you're faced by a tug/tow.....you do not have right of way.
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Old 29-06-2016, 17:29   #81
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Re: Why not electric engine powered boats

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Originally Posted by landlockedsquid View Post
So you'd need an 18kw genny to run a 24 hp electric motor, and 36 kw genset to run a 48 hp electric.
Hmm.
Don't know about efficiency. How big is an 18 kw generator? How much fuel an hour does it use? And then to, if your running a lot of solar and wind then you would have that helping too.
So I don't know how efficient it would be, I would think it would be smaller than a 25 hp diesel engine, but I don't know. It is interesting though.
https://www.northern-lights.com/recr...864w3-2520-kw/ (20kW, but close enough) - 450kg

Yanmar 3JH23A 25HP diesel = 187 Kg

Fuel comsunption for both should be pretty much the same for the same HP output.
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Old 29-06-2016, 18:07   #82
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Re: Why not electric engine powered boats

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Originally Posted by rsn48 View Post
Electric engines are powerful, strong enough to move the modern train diesel, which is an electric powered engine. Wouldn't it make more sense to put in an electric engine to power a boat, with a generator as the power source, thus giving a boat a dual use engine, a better one for charging batteries, etc on the go and on the hook. I'm thinking sailboats in this thread.

Think bow thrusters on large ships; the electric propulsion need not be that big, but it seems you could get a sufficient sized electric engine as motive power.

I'm sure I'm not the first to think of this, so what is the flaw in the design.

Diesel-electric motive power in trains is used as a means of bypassing the need for an extremely high power transmission. A mechanical transmission would be hard to construct for the speed ranges involved and the amount of power and torque transmitted to the wheels and would be a maintenance nightmare.

Diesel electric is used on some ferries because of the ability to shift from forward to reverse quickly on command from the bridge. There is a significant sacrifice in efficiency that is acceptable for some shorter range vessels.

In most water borne vessels a direct mechanical connection is very feasible. Since most water borne vessels are interested in long distance efficiency then mechanical transmissions are dominant, they cost 2-5% of engine output instead of 25-30%.

For daysailors electric drive from battery storage is starting to gain market share.

For cruisers diesel-electric drive doesn't make sense because it would cost several hundred miles in range for the same amount of fuel needed to motor thru calms.

Betamarine has or had a hybrid system that claimed increased efficiency but haven't heard anything about it recently.

Finally I'm going to climb up on my pedantic grammarian hobby horse to say: It's an electric motor not an electric engine. An engine uses heat to create motion, a motor uses any form of energy to creat motion.


A house is but a boat so poorly built and so firmly run aground you would never try to refloat it.
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Old 29-06-2016, 18:17   #83
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Re: Why not electric engine powered boats

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Originally Posted by StuM View Post
https://www.northern-lights.com/recr...864w3-2520-kw/ (20kW, but close enough) - 450kg

Yanmar 3JH23A 25HP diesel = 187 Kg

Fuel comsunption for both should be pretty much the same for the same HP output.
Stu,

Sincere question follows, ..and I admit ignorance here as I do not have personal buying experience with big gensets for boats.

Why is the generator so much heavier? What is it that adds so much weight?

Are all gensets proportionally heavier than Diesel propulsion engines of similar output?
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Old 29-06-2016, 20:46   #84
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Re: Why not electric engine powered boats

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Stu,

Sincere question follows, ..and I admit ignorance here as I do not have personal buying experience with big gensets for boats.

Why is the generator so much heavier? What is it that adds so much weight?

Are all gensets proportionally heavier than Diesel propulsion engines of similar output?
All a generator is, is a propulsion motor hooked up to a very large alternator and very precise govener.

But in order to work a generator has to produce a given amount of power at a very specific rpm. For marine generators that rpm is typically 1800rpm (60hz power). So what you really have is a propulsion motor that has to put out say 10 kW at 1,800rpm, where a 10kw propulsion motor would generate that output at probably 4,200-4,500rpm.
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Old 29-06-2016, 22:45   #85
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Re: Why not electric engine powered boats

[QUOTE=Steady Hand;2155882
Why is the generator so much heavier? What is it that adds so much weight?

Are all gensets proportionally heavier than Diesel propulsion engines of similar output?[/QUOTE]

The generator is a system...an engine with an attached electrical generator, which is a heavy beast, with iron cores on which the copper windings are placed or wound in which the voltage is generated.

A propulsion engine weight may be listed without the transmission weight included. If so, the "system" weights may be more comparable.
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Old 30-06-2016, 01:34   #86
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Re: Why not electric engine powered boats

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Diesel electric is used on some ferries because of the ability to shift from forward to reverse quickly on command from the bridge. There is a significant sacrifice in efficiency that is acceptable for some shorter range vessels.
D/E is used in many cruise ships. The reason cited is efficiency - as I said before the diesel can run at its most efficient speed whether the ship is moving a 5 or 20 kts. This also allows them to use azipods for the manoeuvring (and other) benefits.
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Old 30-06-2016, 05:36   #87
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Re: Why not electric engine powered boats

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D/E is used in many cruise ships. The reason cited is efficiency - as I said before the diesel can run at its most efficient speed whether the ship is moving a 5 or 20 kts. This also allows them to use azipods for the manoeuvring (and other) benefits.
Cruise ships are in a class of their own. They have massive non-propulsion electrical requirements compared to other vessels of a similar size. When most of your power requirements are non-propulsion, it makes economic and engineering sense to upsize your generating power to provide your propulsion as well from a single system.

It's a totally different situation compared to small pleasure craft.
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Old 30-06-2016, 06:22   #88
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Re: Why not electric engine powered boats

It seems as though there are lots of people working on electric powered boats.
Cheap high energy density batteries will be the key.
.

https://www.google.com/search?q=elec...HeicChEQsAQIIg
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Old 30-06-2016, 06:35   #89
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Re: Why not electric engine powered boats

Exactly. When batteries that can store enough energy come on market (tesla?) then it will make sense for mainstream cruisers, not the fringe who accept major compromises.


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Old 30-06-2016, 10:04   #90
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Re: Why not electric engine powered boats

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Originally Posted by StuM View Post
Cruise ships are in a class of their own. They have massive non-propulsion electrical requirements compared to other vessels of a similar size. When most of your power requirements are non-propulsion, it makes economic and engineering sense to upsize your generating power to provide your propulsion as well from a single system.

It's a totally different situation compared to small pleasure craft.
Just like raising the fact that trains use D/E it's true but really misses the point. As mentioned by StuM cruise ships have massive hotel loads compared most ships. Some of the larger ships operate five sycronized generators of which only one or two are used for propulsion the rest can be turned on and off during the day to cover the required hotel loads.

Cruise ships also have unusual propulsion issues. Most vessels are designed to run about 95% of the time at the same speed thru the water. Generally within just a few tenths of a knot because this matched the hulls maximum efficiency curve. Cruise ships however match their speed to a specific arrival time, so they operate at a wide wangle of speeds.

But the biggest issue for cruise ships is that they need azipods in order to have maximum maneuverability. Because most of their ports of call do not have tug boats, and the azipod thrusters allow them to operate independently of outside support. This opens up a lot of ports that typically couldn't handle ships close to as large as modern cruise ships.

For trains... It's all about the transmission. It isn't just the wide gearing involved, that could be gotten around. The real issue is that trains have somewhere north of 18 drive wheels. Think about trying to mechanically connect 18 different drive wheels. The losses would be massive. So it's either hydrolic connections or electric, and electric is more efficient that hydrolic.

Not to say this may not change. If battery technology ever gets to the point that they can store a reasonable amount of power then who knows. As batteries slowly get better the reasonable range gets longer and they become a more reasonable replacement for diesel.

So how much better to batteries need to get?

Diesel has a usable energy density of 48mj/kg. Compare this to fla batteries that have an energy density .17mj/kg, and lifepo is around .5mj/kg.

Now the upside is that electric storage is far more efficent converting to propulsion since you loose about 60% of the available power converting diesel to drive power. So the effective storage capacity of diesel is about 19.2mj/kg.

How much better do batteries need to get? It depends on how far you want to go.
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