Diesel Electric Propulsion

[a64pilot]

Guy's
I don't think a Hybrid boat will be about fuel efficiency, real hard to beat direct mechanical drive for efficiency, to say nothing of complexity and cost. Trains are more efficient due to the huge amount of weight they transport, not due to Diesel electric, but I do bet they move a ton of freight for 1/10 what a truck does, maybe even more than that.
I think a Hybrid boat will be about "cool factor" and being able to run your AC all night, maybe have an electric stove or something, the cost alone of such a system makes it so that most that can afford one, won't really care about efficiency.
As far as fuel costs, of course having a boat that sails well in light winds will win every time?

If you can buy an automobile that costs less to drive than a Prius, wonderful! Can we put it in a boat?


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[socaldmax]

Originally Posted by med

Big long distance container ships are all big single slow speed diesels.
Fuel consumption economy is the absolute overriding factor for ships like the Emma Maersk.

Smaller coastal shipping has a different set of parameters (varying loads, varying speeds and requirements for manoeveribility for small docks etc).

The Navy uses diesel electric not for efficiency reasons but for other advantages (manoeveribility, acceleration, large difference in trolling and maximum speed modes etc).

If you have a Nuclear reactor, then your idea of effiency changes somewhat!
And of course the easiest way to use a Nuclear reactor is to generate electricity using steam turbines and then use all electric drive.

Railroads use diesel electric in order to be able to start a long heavy train rolling. Electric motors have maximum torque at 0 speed which is exactly what is needed there.

I don't know where you get a 10x efficiency gain of Diesel Electric vs pure Diesel for rail roads - that makes no sense.

http://grist.org/article/freight-trains-19th-century-technology-due-for-a-21st-century-revival/

CSX claims it's 4x more efficient than trucks.

10x torque when starting I will believe. That there is something to be gained overall I will also believe because of the requirement to be able to move a heavy train from standstill is something which would require otherwise much bigger diesel engines if using some kind of direct drive. I think also the relatively big speed range required also has a big impact.

A big container ship will be able to engage its propellor directly almost without changing engine speed. The slippage of the propellor in the water allows that to happen.

On a train the problem is the clutch mechanism to allow the engine to turn much faster than the wheels of the train - i.e. to pull away from standstill.

Electric drive is a very simple solution to that problem (and has been used for the best part of a century).

Check the curves and data in the hybrid propulsion article. Nowhere in that particular set up do they manage to get the same level of efficiency from the diesel engine alone, that the JD electronic engine delivers over a very large part of the entire prop curve. Only at very low speeds (i.e. using less than 30HP from a 180HP engine), does the hybrid set up win.

In which case the most efficient solution is may be to have a 20-30HP engine and a 180HP engine clutched to the same shaft and to use which ever engine corresponds to the speed you require. 20 HP is enough to move a 25tonne boat at a few knots. Some big ships use that approach.

The proof is in the pudding.

If VW, with all of their engineering talent, could get 300 mpg out of a TDI, they would. Yet they DID manage to get 300 mpg out of their diesel electric hybrid. Yes, the XL1 weighs less than a TDI and uses more exotic materials in their efforts to save weight, but the fact that diesel electric was the powertrain they chose to build upon speaks volumes to me: if it was attainable via current diesel engine technology, they would have used a diesel engine.

If converting IC power to electrical energy is so inefficient, why did VW go that route to showcase their highest mileage vehicle? To be clear, it's not slightly more efficient than their TDI vehicles, it's roughly 6x more efficient. Again, exotic materials might help to an extent (it still weighs 1750 lbs, I've seen VW powered dunebuggies with full roll cages that weighed only 600 lbs) but it certainly did not make it 6x more efficient just by weight savings alone.


Interestingly, they're talking about adding sails to huge container ships to help reduce fuel consumption. LOL

[TheThunderbird]

With ihybrid, you can accumulate energy onto battery pack and release it on temporary peak torque/power demand.


In so far you need say 100BHP 5% OF the time, and cruising speed is attainable with say 60BHP, it make sense to have, sooner or later, a 60BHP diesel with say 1000Ah 48V battery pack
Lithium costs 4x more, on the decrease, may have 3000 deep cycles down to 10% residual force...
In italy Riva has tested a 120kw electric engine, total unit worth 45keur, say 56k usd

It all adds to the fact that electric generation is needed onboard anyway. Under a. Hybrid, ylu can decide how to shafe output between power shaft and battery refill, while keeping engine on its best efficiency range. Power trim is always. NOxious in any engines ... oops i'm a mechanical eng. :-)

[med]

Originally Posted by TheThunderbird

With ihybrid, you can accumulate energy onto battery pa k and release it kn temporary peak torque/power demand.


In so far you need say 100BHP 5% OF the time, and cruising speed is attainable with say 60BHP, it make sense to have, sooner or later, a 60BHP diesel with say 1000Ah 48V battery pack
Lithiumcosts 4x more, on the decrease, may have 3000 deep cycles down to 10% residual force...
In italy Riva has tested a 120kw electric engine, total unit worth 45keur, say 56k usd

Except it does not work when that 5% all comes together for 4 hours straight into the teeth of a gale. Then your battery pack is woefully inadequate.

Unfortunately the most space efficient way of storing a decent amount of energy is in a diesel's fuel tank. (Nuclear not being an option for most of us here). And a diesel engine directly coupled to the propellor is the most efficient use of that fuel.

[manitu]

OK..Electric engines.

Electric hp/torque: all electrical motors produce maximum torque at 0 RPM.How much depends on the engine and the voltage. Then, torque falls in a LINEAR cuvre, all the way to the maximum free running speed, where you have 0 torque. Speed depends on voltage.

The reason for this is logical. When the motor starts spinning, it acts as a generator. It creates a voltage, fighting against the current from the speed-controller. This voltage is a product of the speed of the motor and nothing else, and is linear. At max free running speed, the generator voltage from the motor is equal to the controller voltage, and therefore there is no current going to the motor, and you have no torque.

When we know that HP=RPMxTorque(ft.lbs)/5252, anyone who would like to predict the shape of the HP curve?

If you compare DC motors or Sep-Ex (seperately exited) motors with ICE engines, especially in the typical cruisers boat, the electric ones are losing. Even more so in a hybrid system, where the prop has to be optimized for the ICE.

But PM (brushless) electrical motors.. If you have tried RC planes the last decade, you know what im talking about. I guess they are at least 30% more effective than the old DC motors.
But they need a speed regulator, and since the magnets are permanent and not a exited magnet field you dont get them that big because of weight.

And prices.. a 5KW cont./15KW peak motor with controller costs about 1000$ +tax. +batteries..

But still, I dont think you will save money compared to a marine diesel engine of the right size, with optimized prop, running at optimal speed.

But, as a real option for budget long distance cruisers, going to remote places, it could work.
Not in a hybrid setup, but pure diesel-electric. If you set up the boat with electric motor, batteries and a charger , and aim to use a standard portable generator as powersource.
No need to pray that you find that SABB exhaust manifoil in samoa,just buy another cheap generator set.


.manitu

[TheThunderbird]

Oh God! Combustion efficiency can not be the sole criteria!

Ability to optimize the output delivery from a mix of solutions, none of them being stretched to the extreme, is by definition a winni g approach in any mix-max theory (vonNeumann).

Instead of trimming diesel RPM on a wide array, say from 600 to 3600RPM (wherein only a rather strict spectrum of top torque applies) (and torque means efficiency.. btw) i prefer to be able to operate a shift between power usage/power accumulation in. Electric form, for both usage and propulsion.

Some power units are already packed into one.
Said that, anyone may feel free to overpower his/her sailing boat with 8+BHP/tonne and pretend to move full throttle around.
MOst do, here in italy, me sailing 3kn and oceans/dufour of 33' ruffling around at 7kn.... happy everyone

[BambooSailor]

The proof is in the pudding.

No need to add more pudding. First, XL1 gets 260 miles per US gallon when battery is recharged every 47 miles. Without recharging it gets 120mpg. Definitely impressive, although far from 300mpg. Second, XL1 powers rear wheels through mechanical seven-speed dual-clutch gearbox. Third, what is definitely very impressive is that they got 48 HP from 800 cubic cm engine. Most marine diesels in this power range are twice as big. I'd love to get marine version of this engine for my boat! In other words, VW does not get its impressive mileage by converting diesel power to electricity. You just cannot beat simple mechanical transmission for efficiency, sorry. All diesel-electric implementations (including hybrids) address different propulsion problem, not "inefficiency" of simple gearbox. And no, I am not Luddite, just real-life, very green-conscious engineer.

[TheThunderbird]

As taken from the RollsRoyce shipbuilding marine components page

"
A diesel-electric hybrid propulsion system similar to SAVe Line, where generating capacity can be reduced by up to 30% with energy storage."

DinDon the siesta time is over...RR whistles, doesn't it??

@ Bamboosailor: Sir, you may end up with a smaller clutch, lower vibration, less strain, more durability and control in power delivery, are all those items negligible?
as an engineer, you should know that There are some more than a DOZEN OF EFFICIENCY FACTORS in an IC engine. Sure it all translates into a mpg measure, but NOT ceteris paribus, all the rest being unchanged.

I feel like US people are driven by mpg indexes only, mammamia... are you all Detroit based old time designers? :-)

[henryv]

Things will get more interesting when some of the new technology currently under development becomes available for use in boats. If you Google eV range extenders you will find a number of companies working on very compact, light, efficient generators using a variety of new approaches such as rotary engines, turbines, free floating pistons, and more. The focus at the moment is clearly for automobile use but in time whatever technology wins out will no doubt become available for other markets.
Henry

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[TheThunderbird]

"

But still, I dont think you will save money compared to a marine diesel engine of the right size, with optimized prop, running at optimal speed.


.manitu[/QUOTE]"

you can answer yourself!
1. The overall design, expected output and delivery conditions/expectations must re-assessed, based on new paradigma, which is nether max ouput nor max. Speed/range nor anything else, but a Desireable/Flexible mix. Wow, great word FLEXIBILITY, never heard about in on CF, sorry
2. No one is claiming for a cheaper solution here! But for a smart compromise of a mix of technologies, only partly new, expensive yes, yet on the decline

Please do not adopt a B/W approach, it doesn't work but for righteous bosses and in politics :-)

[socaldmax]

For many people, the added expense of a large Lipo battery bank and big genny and lots of solar is far more than they want to spend, so they stick with their current diesel engine. After all, these are sailboats first and foremost, it's not like we're chopping off the mast and turning these into power boats.

However, we've already seen a few members convert their dead diesel into a comparable electric motor powered rig for surprisingly low cost (compared to what I would have spent) LOL.

I'm looking at this scenario: a 45' cat with shaft drives. I already plan on 3200w of solar panels and a fairly large battery bank of LiFePo4s just because even if I'm in a remote harbor, I'd like to be able to air condition one hull or the salon off of the inverter overnight, possibly with the assistance of a portable genny, or maybe 6 hrs on the main genny and 6 hrs on the inverter. Plus I plan on a big fridge, big freezer and ice maker.

Now honestly, with that setup, I'd leave the engines alone and possibly upgrade to high output alternators just for more flexible power generation. However, let's say one engine eats itself and the replacement is going to cost...? 15k? At that point, I'd look long and hard at a brushless DC motor in the 15-20hp range. The new motor is going to weigh less than the old engine/trans combo, so I could add more lipo batteries equaling the weight difference.

Now I'd have plenty of solar power, plenty of generator power, tons of battery storage cap., a silent electric motor that could run for a decent amount of time just off batteries (and solar if during daytime) or batteries and genny at night and still have a diesel engine if I needed to motor for hours on end.

So what I'm saying is I wouldn't rip out a perfectly good working diesel to repower with DC motors, but I would definitely consider replacing a dead one with a comparable DC motor and throw the rest of the money into expanding the battery bank.

[a64pilot]

My neighbor has a Lagoon 38 or 40, not sure, He says the thing has a 12KW generator?
Wouldn't that almost drive the boat?
On a Cat, why not one hull Diesel, the other electric? Most of the time I assume the electric would be enough, but if it's not, crank the Diesel too?

Socal, reread your post, we are saying the same. While I don't want a Cat, I can see many advantages to one, dual rudders, can't sink, dual engines, and I think one electric and leave the other Diesel at least sounds very logical from a first look, especially if they come already equipped with monster generators already.

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[manitu]

Originally Posted by TheThunderbird

"

But still, I dont think you will save money compared to a marine diesel engine of the right size, with optimized prop, running at optimal speed.


.manitu

you can answer yourself!
1. The overall design, expected outputand delivery conditions/expectations must re-assessed, based on new paradigma, which is nether max ouput nor max. Speed/range nor anything else, but a Desireable/Flexible mix. Wow, great word FLEXIBILITY, never heard about in on CF, sorry
2. No one is claiming for a cheaper solution here! But for a smart compromise of a mix of technologies, only partly new, expensive yes, yet on the decline

Please do not adopt a B/W approach, it doesn't work but for righteous bosses and in politics :-)

If you read my post as being against electric motors, perhaps I didnt express myself correctly. Im a great belliever in electric bikes, and I get 80km range from my bike, on a 72volt 15AH battery. Fullly charged for less than a dollar.

But boats are different beasts all together..

First, to your questions: 1: My priorities are first of all max output for a prolonged period. Like the mentioned lee-shore situation. Second is range per pound of ballast. Sorry.

2.I meant consumption! And electric engines are way cheaper, if you dont look at the big brand integrated solutions. Electric motors has been around since the invention of electricity, and the BLDC/PMAC controllers has been around for a decade.

Electric Car Motor, Brush Motor - DC Motors


Electrics in boats..

Since the optimal prop for a electric motor making the same thrust would be way bigger and slower turning than the diesel prop, hybrid drive on the same prop would demand massive gearing for one of the motors.

Prolonged electric motoring would require either a massive battery bank, or close to 100% generator capacity.

I was close to choosing electric propulsion on my boat, but got me a 10hp kubota for cheap. I was planning 80% generator capacity, 2x4hp generators on a mars 4201 motor using about 7KW.

Electrics are quiet, systems can be made more flexible, and you can construct it using independent subsystems wich are easier to replace by wichever brand.

But some people seems to feel that electric engines are far more efficient than diesels.
In cars, yes, but because of variable load. Compared to a diesel running at optimum RPM, not so much.

.manitu

[manitu]

And one more thing:
A 36 or 48volt system you can legally work on yourself, in europe at least. 48volt stings a little.

72volt from Lithium cells will burn you bad in best of cases, we call it "kentucky fried fingers".
96 or higher can and do kill.

.manitu

[ranger58sb]

Originally Posted by a64pilot

My neighbor has a Lagoon 38 or 40, not sure, He says the thing has a 12KW generator?
Wouldn't that almost drive the boat?
On a Cat, why not one hull Diesel, the other electric? Most of the time I assume the electric would be enough, but if it's not, crank the Diesel too?

Might do. Our 8KW genset uses a Yanmar 3-cylinder 3TNE74 diesel, which gives 14-hp at a constant 1800 RPMs (and up to about 24-hp at 3600 RPMs, looks like for non-generator applications). I'd guess the engine on a 12KW genset might give around 20-hp at 1800 RPMs...

FWIW, I'd guess two 8KW (for example) gensets would be better than one single larger one. They could be combined when necessary, but otherwise the duty cycle could alternate days or whatever... which means easy maintenance on one while the other is running. And the two could maybe be better located for service access, for balance, for ballasting, etc.

I would expect conversion to diesel-electric can be a decent option for examination when an existing propulsion system needs replacing anyway. Otherwise, conversion may add some owner-perceived improvements, even if it's not cheaper to run... but at a cost many wouldn't want to bear. And original installation may be -- or become -- closer to cost-bearable, but it may still remain for a long while that it's not cheaper.. and that the other perceived improvements (installation location, service access, azipod drives maybe, lower ambient noise levels, etc.) are really driving the train. So to speak.

In my mind, a diesel-electric installation similar to the Torquedo video in a cat would be well-worth it, even if it's (bearably) more expensive than a standard diesel/straight shaft propulsion system. But it still would depend very much on the size of that bear.

And I'd need a cat with a decent flying bridge, and at least one walk-around (master) berth. Which means thee basic boat is out of my reach in the first place no mater what the aux propulsion system.

-Chris