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Old 12-12-2018, 01:18   #1546
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Re: Oceanvolt Hybrid Motor

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. .. Hi Dockhead, thanks for contributing. We're probably not as far away as some might think. There's lots of factors at play but growth at the beginning is always slow. . .

I hope you're right!


The best thing which could happen would be some terrific breakthrough in energy storage. We are addicted to diesel fuel only because of the incomparable energy density which diesel fuel has. If we could store electrical power at similar densities, even 5x worse than diesel fuel, this would open up immense horizons.
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Old 12-12-2018, 01:31   #1547
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Re: Oceanvolt Hybrid Motor

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Originally Posted by ssmoot View Post
The most important efficiency aspect, by a large margin, is fuel efficiency.

Your argument completely ignores it. That's where it's gone off the rails.

A Yanmar 3YM20 can produce 15kW at the crank at about 3,100RPM. It will consume about 3.5L/hr at that rate.

A Yanmar 3JH40 can produce 15kW at the crank at a tick under 1,400RPM. It will consume about 1.2L/hr at that rate.

In other words, two engines, producing the same HP. One uses almost 3X as much fuel as the other.

Now guess what engine a genset for a comparable EP system might look more like? The 0.85L 3YM20, or the 1.64L 3JH40?

THAT is how an EP can be more efficient. That 3X efficiency gap leaves a mile wide margin for any conversion losses. They're absolutely meaningless in the face of that.

This "direct drive magic" efficiency argument needs to go away.

What makes you think you will be able to operate a hybrid at that level of efficiency, when you can operate a mechanically driven boat only at the other level? Diesel engines don't vary as much as that that in specific fuel consumption. You get dramatic differences only using a diesel way outside of its normal operating regime. You saw the chart posted earlier -- the difference between the best and the worst regime for a given engine was only about 10%.


Using a better or worse engine (common rail turbo diesel vs indirect injected naturally aspirated) or better or worse propeller (fixed vs variable pitch) is not inherent to either drive system, so you can't claim a better engine or a better prop as an advantage of hybrid -- you can get these on mechanically driven boats as well. I have a variable pitch prop on my mechanically driven boat.



Nor does hybrid drive somehow magically allow you to use your diesel generator in its sweet spot all the time -- because you simply need varying amounts of power in any case.


You are comparing an old fashioned engine running at its max output, overfueled, with a common rail engine running in its sweet spot. That is not an apples to apple comparison -- this difference is not inherent difference between hybrid and mechanical. Use the same engine on the mechanically driven boat and run it at the same output regime, and you will use less fuel than the hybrid.
__________________
"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
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Old 12-12-2018, 02:50   #1548
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Re: Oceanvolt Hybrid Motor

I suspect some of the EP wishful thinkers imagine that hybrid auto tech will improve fuel efficiency for cruisers as it does for drivers. But it will not. Boats don't have regen braking which contributes a lot to auto hybrid efficiency. Also, cruisers run their engines near the most efficient speed when motoring on long passages. And there are no plugin stations on the high seas nor in marinas. So all electricity consumed has to be manufactured on board. Right now for long distance motoring fossil fuel is the only alternative.

Look at fuel burned per kWh generated. Then look at kWh consumed per nautical mile. That's your fuel economy data. You can do the same measurement and math for a mechanical drive. The only way a mechanical drive loses the comparison in cruise mode is if it is poorly designed. And you don't have to risk the warranty to design it properly. Who cares about the economy when slow maneuvering? No one because it is an insignificant use of fuel.
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Old 12-12-2018, 03:26   #1549
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Re: Oceanvolt Hybrid Motor

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Originally Posted by Dockhead View Post
Diesel engines don't vary as much as that that in specific fuel consumption. You get dramatic differences only using a diesel way outside of its normal operating regime. You saw the chart posted earlier -- the difference between the best and the worst regime for a given engine was only about 10%.
This is because the engine is coupled to a prop, you are unable to use the engine at it's optimum SFC. Where you are using it, it has the same 30% worse (that particular engine) SFC. It can never reach the low RPM high throttle low SFC regime for best fuel economy because you can't load it at low RPM's like you can with the engine in the generator. If you were to design it to be loaded it at low RPM's, you'd never reach high RPM's and you wouldn't be able to maneuver. Think about it.

Quote:
Originally Posted by Dockhead View Post
Using a better or worse engine (common rail turbo diesel vs indirect injected naturally aspirated) or better or worse propeller (fixed vs variable pitch) is not inherent to either drive system, so you can't claim a better engine or a better prop as an advantage of hybrid -- you can get these on mechanically driven boats as well. I have a variable pitch prop on my mechanically driven boat.

Nor does hybrid drive somehow magically allow you to use your diesel generator in its sweet spot all the time -- because you simply need varying amounts of power in any case.
Yes you can, it's the USE that allows you to change the engine. One has to idle but not too fast AND also produce a certain amount of power at cruise continuously, and also sell it's max HP to the buyer. The other has one target only, efficent power continuously. A generator engine is NOT the same as a drive engine.


Quote:
Originally Posted by Dockhead View Post
You are comparing an old fashioned engine running at its max output, overfueled, with a common rail engine running in its sweet spot. That is not an apples to apple comparison -- this difference is not inherent difference between hybrid and mechanical. Use the same engine on the mechanically driven boat and run it at the same output regime, and you will use less fuel than the hybrid.
Unfortunately I don't know the two engines ssmoot compared so I'm not sure if you could use the more efficient one in a drive application or vice versa. Still the point remains that you CAN and WILL choose a different more fuel efficient engine for the generator and use it ONLY in it's fuel efficient regime because it CAN be used at it's most efficient. The direct coupled engine CANNOT be used at it's most fuel efficient, because it is unable to run at one speed! USE matters.

Let me add, a couple posts take shots at me for not knowing "your" engines. No problem, I'm not telepathic, tell me what engine you have, and we'll dig up the mfg. specs and find out how long it will run at WOT and with what fuel consumption. I'm sure only those with high duty ratings will speak up, but we can still make the case. Or you can let me keep talking about the specific Yanmars already mentioned, who are fine engines, but whose definition of continuous is 30 minutes every 8 hours. If we are ok with that definition of continuous, then magic does exist and this discussion is pointless, because we can use magic to explain away all the pesky HP, duty cycle, duty rating, SFC numbers, they just hold us back from what we want to believe.

BTW, no one is here to insult what anyone is doing, but I find that sometimes people take new technology as a personal affront to the way they've been doing things. Nothing is wrong with what we are doing now, in fact hybrid solutions are very expensive right now, and therefore it's truly debatable whether it's worth it to choose this in a new build. Whatever you have now, it's right for you and none of this discussion makes it "wrong".
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Old 12-12-2018, 03:42   #1550
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
I suspect some of the EP wishful thinkers imagine that hybrid auto tech will improve fuel efficiency for cruisers as it does for drivers. But it will not. Boats don't have regen braking which contributes a lot to auto hybrid efficiency.
I think most EP proponents understand that regen doesn't apply most of the time except when sailing. I don't count it, I don't sail. It does look like it has potential, but no one should count on it.

Quote:
Originally Posted by transmitterdan View Post
Also, cruisers run their engines near the most efficient speed when motoring on long passages. And there are no plugin stations on the high seas nor in marinas. So all electricity consumed has to be manufactured on board. Right now for long distance motoring fossil fuel is the only alternative.
No they don't, check out the SFC graph posted earlier. Agree that fossil fuel is required for long distance at this time and for the foreseeable future. It's about energy density.

Quote:
Originally Posted by transmitterdan View Post
Look at fuel burned per kWh generated. Then look at kWh consumed per nautical mile. That's your fuel economy data. You can do the same measurement and math for a mechanical drive. The only way a mechanical drive loses the comparison in cruise mode is if it is poorly designed. And you don't have to risk the warranty to design it properly. Who cares about the economy when slow maneuvering? No one because it is an insignificant use of fuel.
Disagree as detailed extensively, direct drive has losses in the design because of the constraints of having to idle, maneuver, run continuous, and sell max HP all at the same time. EP does not have the same restriction.


Do agree that we need to study fuel burn on the same hull, two correctly designed systems, as apples to apples as we can and until then this is all a theoretical discussion.
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Old 12-12-2018, 03:50   #1551
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by transmitterdan View Post
I suspect some of the EP wishful thinkers imagine that hybrid auto tech will improve fuel efficiency for cruisers as it does for drivers. But it will not. Boats don't have regen braking which contributes a lot to auto hybrid efficiency. Also, cruisers run their engines near the most efficient speed when motoring on long passages. And there are no plugin stations on the high seas nor in marinas. So all electricity consumed has to be manufactured on board. Right now for long distance motoring fossil fuel is the only alternative.

Look at fuel burned per kWh generated. Then look at kWh consumed per nautical mile. That's your fuel economy data. You can do the same measurement and math for a mechanical drive. The only way a mechanical drive loses the comparison in cruise mode is if it is poorly designed. And you don't have to risk the warranty to design it properly. Who cares about the economy when slow maneuvering? No one because it is an insignificant use of fuel.
I guess by that definition every single speed fixed pitch system I've seen is poorly designed.

All the data cards I've seen are set up to have the propeller curve cross the engine power curve right near the maximum engine output at high rpm. This gives the boat access to all the engine's output, and ensures there's plenty of excess torque capability at lower speeds to drive acceleration. It also means you can never get to the efficient part of the bsfc map.

All diesels (virtually all ICEs of any type) are most efficient at the peak torque rpm and at or near full throttle. You develop the highest cylinder pressures and have the lowest relative pumping losses to offset. For diesels, that's typically about half the max power rpm.

The problem with the direct drive system sized for max power is that at that speed the propeller can only absorb about twenty percent of what the engine can generate, so the governor throttles it back to hold rpm and that drops you back to the less efficient part of the bsfc map. I posted a map from a modern small diesel in the previous post.
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Old 12-12-2018, 04:42   #1552
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Re: Oceanvolt Hybrid Motor

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Originally Posted by saghost View Post
I guess by that definition every single speed fixed pitch system I've seen is poorly designed.

All the data cards I've seen are set up to have the propeller curve cross the engine power curve right near the maximum engine output at high rpm. This gives the boat access to all the engine's output, and ensures there's plenty of excess torque capability at lower speeds to drive acceleration. It also means you can never get to the efficient part of the bsfc map.

All diesels (virtually all ICEs of any type) are most efficient at the peak torque rpm and at or near full throttle. You develop the highest cylinder pressures and have the lowest relative pumping losses to offset. For diesels, that's typically about half the max power rpm.

The problem with the direct drive system sized for max power is that at that speed the propeller can only absorb about twenty percent of what the engine can generate, so the governor throttles it back to hold rpm and that drops you back to the less efficient part of the bsfc map. I posted a map from a modern small diesel in the previous post.
Spot on! I know you were kidding, but people are sensitive to feeling their systems are poorly designed. I would contend that they were well designed given the constraints, just that there are more options now that have different constraints.
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Old 12-12-2018, 05:10   #1553
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Re: Oceanvolt Hybrid Motor

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Spot on! I know you were kidding, but people are sensitive to feeling their systems are poorly designed. I would contend that they were well designed given the constraints, just that there are more options now that have different constraints.
Absolutely. The engineers have to make choices. Do you build the system for the best possible efficiency at five knots, accepting that it means a maximum speed of five knots, or do you accept somewhat lower efficiency at five knots to get a ten knot maximum speed from the exact same hardware?

I used the poorly designed language because that was what he'd used to dismiss the argument, not because I think the engineers chose badly in optimizing the propulsion design for cruising boats.
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Old 12-12-2018, 06:18   #1554
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Re: Oceanvolt Hybrid Motor

I don't know of any EP systems that beat mechanical in efficiency. But assuming it is possible, then at what percent of WOT on the ICE will an optimized EP system overtake a mechanical system in terms of efficiency (fuel burn per nautical mile)?
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Old 12-12-2018, 07:13   #1555
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Re: Oceanvolt Hybrid Motor

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Unfortunately I don't know the two engines ssmoot compared so I'm not sure if you could use the more efficient one in a drive application or vice versa. Still the point remains that you CAN and WILL choose a different more fuel efficient engine for the generator and use it ONLY in it's fuel efficient regime because it CAN be used at it's most efficient. The direct coupled engine CANNOT be used at it's most fuel efficient, because it is unable to run at one speed! USE matters.


A problem with this argument is, for the most part, RPM doesn't dictate efficiency, loading dictates efficiency. Yes, you must match the power output of the ICE to the application, too big or too small leads to inefficient.

But the ICE generator powering EP sees the load from the prop just like the ICE does in a direct drive application.


Determine the best SFC rpm, pitch the prop to meet desired load/performance.



Low speed in/out harbors and marinas doesn't count. I spend $$ more on beer in one week than fuel in a year running low speed. Design the system for efficiency on long passages, that's where the majority of fuel is burnt.
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Old 12-12-2018, 07:24   #1556
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
I don't know of any EP systems that beat mechanical in efficiency. But assuming it is possible, then at what percent of WOT on the ICE will an optimized EP system overtake a mechanical system in terms of efficiency (fuel burn per nautical mile)?


Actually electric is way more efficient, way more, but I assume you mean if your having to make your own electricity via an ICE generator?
Cause yes, that will be significantly less efficient than direct drive.

People have tried to install a second small ďponyĒ motor in the theory that you can operate the little motor at its efficiency peak and drive the boat at slow speed much more efficiently than a larger motor that is loafing at low RPM.
Unfortunately it works on paper, but in the real world when the extra weight and drag penalties are accounted for, itís pretty much a wash, no real gain in efficiency.
You do get a get home motor though.

Turbocharged, electronically controlled high pressure common rail Diesels are slightly more efficient, but not as much as you may think, but the weight lost in a small high performance Diesel isnít insignificant.

Electric propulsionís niche in my opinion is for those that primarily sail, but need a motor to get into and out of a pen or maybe to have as a back up for a bar crossing as a safety net, back down to set an anchor etc.
Itís not for those of us that will crank our motors and run it for days, just cause the wind isnít cooperating.
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Old 12-12-2018, 07:31   #1557
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Re: Oceanvolt Hybrid Motor

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But the ICE generator powering EP sees the load from the prop just like the ICE does in a direct drive application.
In fact it does not. Only the electric motor (and controller + batteries) see the load. The ICE generator puts excess capacity into batteries, and doesn't care about excess load. It is sized and designed to be at optimal load at all times.
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Old 12-12-2018, 07:52   #1558
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Re: Oceanvolt Hybrid Motor

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In fact it does not. Only the electric motor sees the load. The ICE generator puts excess capacity into batteries, and doesn't care about excess load. It is sized and designed to be at optimal load at all times.

And if the batteries are full?
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Old 12-12-2018, 07:57   #1559
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Re: Oceanvolt Hybrid Motor

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And if the batteries are full?
Then you turn the engine off and run on battery power for a few hours in glorious silence.
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Old 12-12-2018, 08:09   #1560
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Re: Oceanvolt Hybrid Motor

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And if the batteries are full?
Let me do the math for the engine being off. Zero, times zero, carry the one..... I believe that comes out to zero fuel consumption. It probably sounds a bit like sailing.

Before someone yells at us for claiming "magic" zero fuel consumption, we know that we have to turn the generator back on at some point depending on how much we are pulling from the batteries based on how fast we are going, but it all contributes in the end to some amount of fuel burn. If we can do it efficiently while burning it, and zero while off, the sum in theory should be more efficient. I believe current properly designed systems can achieve this now, but I'm also interested in the real numbers. I'm skeptical of all claims until I have reproducible data.

Edit: The one thing for sure, there are a lot of smart people betting their livelihood on this. They may be wrong, but there is something causing them to bet big. It's not smoke and mirrors when engineers are involved.
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