Diesel Electric Propulsion

[nimblemotors]

Sorry, but I have to correct this, as I said, on the highway, the engine DOES generate electricity to drive the car. I was incorrect however it is only 25%, 75% is directly from the engine. The point being that generating electricity to power a motor while not as efficient, is doable.
You can read all the gory details on this writeup,
Whats Going On As I Drive?

A boat could be driven using a prius drivetrain, and while they are issues, given you can buy one for $3,000, sure is a lot cheaper than $300,000 or even $30,000...

Originally Posted by a64pilot

The engine also has a motor / generator on it's flywheel essentially, although it can charge the traction battery at highway speeds, it drives the wheels directly, but the battery can be used for passing, climbing hills etc, but it does not generate electricity to drive an electric motor for propulsion, it drives the wheels directy through the PSD.

What does this have to do with boats? Well a boat could do the same thing, drive the prop either directly by the engine, or directly by an electric motor or both, it could also just charge batteries with a planetary gear system ALA Prius.

[JRM]

What most detractors of electric auxiliary sail boats often ignore is that electric sailing is radically different from motor sailing and pure sailing. I converted our previous boat (coastal cruising) to pure electric with a Honda2000 portable generator for backup and recharging away from the dock. It's still in the family, and I do most of the maintenance on it.

Firstly, regeneration for any reasonable non-cat application is over-rated. To the point of outright lies. You might suggest "creative marketing" but that's being too kind. Way too many folks are sold the "free fuel as you sail." Not happening. We were lucky to regen small house loads over 5 hour sails. Solar has been successful in some applications, but you need radical panel coverage and lots of time, as the math easily shows. So the idea of "free fuel" really only works because the marina doesn't meter electric, so there's no additional charge :-)

Electric auxiliaries allow what some electric boaters refer to as "electric sailing." By applying 100-200 W of electric motor input while sailing the whole game changes. The prop drag is eliminated, which given the giant wheel we fitted is huge. It also adds about a knot of speed in lighter airs. We can point higher and tacking is a breeze. It's basically like silently motor sailing all the time.

As great as electric sailing is, for our use the biggest difference is in docking. Since you don't have to worry about the motor stalling, you can spin the prop at any RPM you want. We just crawl in nice and slow in complete control. You really have to experience it to understand.

The point being that just dropping an electric system in to replace direct drive diesel with the intent to use it exactly the same doesn't make sense. The advantages of adding an electric propulsion component go way beyond just replacing a motor horsepower for horsepower.

JRM

-- generally, the empirically derived formula is one kW of motor per ton of displacement for most monohulls.

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[ranger58sb]

Originally Posted by JRM

So the idea of "free fuel" really only works because the marina doesn't meter electric, so there's no additional charge :-)

And even that doesn't hold true for those of us who have individually-metered electricity at the marina.

-Chris

[Cheechako]

Originally Posted by a64pilot

We have 150K on our 2010 Prius divided by 50 MPG is 3000 gls of gas X $3 a gl is $9k
A SUV getting 15 MPG 150K divided by 15 MPG is 10,000 gl of gas X $3 a gl is $30K
In four years, thats $21,000 I saved in fuel, and 7,000 gls of more gas for everybody else to say nothing of the lower pollution etc. But yes unless you drive a LOT, you do not save money with a Hybrid. A Hybrid for a working slob who drives a lot, makes sense.

But a boat Hybrid will never save you money, it's not going to be more efficient, or at least I don't think so, it's advantages will have to be other things, ecenomy isn't one of them.
I just bought an Autoprop, tremendously expensive thing. Will supposedly increase part throttle efficiency lots, burn less fuel, increase range, make motorsailing much nicer. Taht's if it lives up to the Hype anyway. I am sure it will never save enough in fuel to pay for itself, but if it does the other things it's supposed to, I'll be happy.
I think a Hybrid boat will be similar, if you want to eb able to run your AC all night without a generator, then you will like it, but I think you could accomplish most of the adavntages of a Hybrid with a monster LIFE battery bank and gobs of Solar and a big generator.
Maybe that is what we will see first? Even with electric drive if your going more than a couple of miles on a Hybrid boat, your running a Diesel anyway

You're comparing apples and oranges when using an SUV. Now do the comparison with a 40+mpg gas car about the same size as a Prius! ... and include the higher initial cost for the Prius.
Having said that I love the Prius!

[a64pilot]

Originally Posted by nimblemotors

Sorry, but I have to correct this, as I said, on the highway, the engine DOES generate electricity to drive the car. I was incorrect however it is only 25%, 75% is directly from the engine. The point being that generating electricity to power a motor while not as efficient, is doable.

You can read all the gory details on this writeup,

Whats Going On As I Drive?



A boat could be driven using a prius drivetrain, and while they are issues, given you can buy one for $3,000, sure is a lot cheaper than $300,000 or even $30,000...

I had read that, years ago, that also is a Gen II Prius, Gen III is a little different, and to be honest I think he is wrong on some things, like the ICE always being in top gear etc. One trick the Prius uses is to run at full throttle, but at very low RPM to reduce pumping losses, remember this is a gasoline engine and not a Diesel, so anything less than full throttle there is a vacuum in the intake manifold and that is in-efficient.
Prius in steady state speed will sometimes draw from the battery, and sometimes charge the battery, computer deciding what is most efficient, I also believe it will use one motor as a generator to drive the other motor, as illogical as that sounds, that having to do I believe with achieving the desired gear ratio with the PSD. When you really dig into the thing, it's operating principles are fascinating, one proposed next Gen will have a digital map topo database and a GPS, the computer will decide if it's more efficient to use the battery power to climb a hill as it will get it back on regen going down the other side, or use the engine as there may be no down hill, or planned route has you making a turn etc.

I think for someone who really wants a hybrid boat, a Prius drive train is worth looking into as it can drive the boat directly without all the losses associated with converting kinetic to electric back to kinetic etc, Prius could drive the boat, charge the battery, draw power from the battery, charge battery from the prop all within it's capabilities now, would be exceptionally quiet and extremely low pollution.
One of the modifications to a Prius that is pretty common is to use one as a stand alone generator to run your house in the event of storms etc knocking out the power grid, Prius will run off the battery until the SOC drops, then crank the ICE to recharge, then turn the engine off. If you camp in a Prius, leave it "running" and set the AC to a comfortable temp, the engine will start a couple of times during the night to keep the battery up, the AC runs directly off the battery of course, so in a boat, run everything of the battery, the engine will start automatically and run at it's most efficient RPM, recharge the battery and shut down, all automatically.


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[a64pilot]

Originally Posted by Cheechako

You're comparing apples and oranges when using an SUV. Now do the comparison with a 40+mpg gas car about the same size as a Prius! ... and include the higher initial cost for the Prius.
Having said that I love the Prius!

Your right of course, just with most Americans, it's an SUV. Look at the roads, they are full of SUV's with one passenger. To make the Prius make sense money wise, you have to drive a lot and keep one for several years. If you drive 10,000 miles or less, you'll probably never break even.

Still like to see a smart guy put one in a boat though, have to be a pretty smart person though.


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[med]

Originally Posted by a64pilot

If you camp in a Prius, leave it "running" and set the AC to a comfortable temp, the engine will start a couple of times during the night to keep the battery up, the AC runs directly off the battery of course, so in a boat, run everything of the battery, the engine will start automatically and run at it's most efficient RPM, recharge the battery and shut down, all automatically.

Just like a standard set up with a generator and a Victron charger/inverter system.

Quattro - Victron Energy

No connection - but my next boat will have a relatively small generator, one of those (or two in parallel) with a biggish battery bank and a bigger single electronically controlled main diesel connected to a shaft. Probably with a fixed propellor although if there is enough difference I might be tempted by a controllable pitch propellor.

[44'cruisingcat]

Originally Posted by Cheechako

You're comparing apples and oranges when using an SUV. Now do the comparison with a 40+mpg gas car about the same size as a Prius! ... and include the higher initial cost for the Prius.
Having said that I love the Prius!

At least in Aus, there are small turbo-diesel cars that use less fuel than the Prius, cost less to buy and are much better to drive.

[med]

Originally Posted by 44'cruisingcat

At least in Aus, there are small turbo-diesel cars that use less fuel than the Prius, cost less to buy and are much better to drive.

For the same price as a Prius you can have a Mercedes Benz C200 CDI which is a much nicer drive and consumes no more fuel than the Prius in real life use.

A good site for checking out real life fuel consumption is:-

Real MPGs | Honest John

Before you get over excited, remember that those are imperial gallons

[socaldmax]

Originally Posted by med

Diesel is more efficient than diesel electric.

Diesel electric does not make sense for long range constant speed use. The diesel will have been chose and set up on a fixed shaft and propellor to work the diesel at its optimimum specific fuel consumption.

Diesel electric is used in cruise ships for convenience in manouevering. It allows the use of pod drives and avoids the need to pay for tugs when docking. They also dock very often.

All big long distance container ships use a single big diesel on a single fixed shaft and propellor for optimimum efficiency. They also use heat recovery and steam turbines to get more out of the fuel and can compete with the best oil fired land based power stations in the efficiency stakes.

Diesel electric makes little sense in a boat when you start looking at the specific fuel consumption maps of a modern, common rail, direct injection, electronically controlled, turbo charged, diesel engine.

An interesting article here:-
The Science of Hybrid Propulsion: Part 2 | | PassageMaker

Note the last question which went unanswered. A straightforward fixed propellor shaft installation on a modern 6 liter John Deere is always at least as efficient as the diesel part alone in the hybrid installation - not accounting for any electrical losses.

I'm afraid that statement is wrong.

The largest freight carriers in the US is the railroad system, and they've been using diesel electric hybrid systems for decades, according to their statistics, their diesel electric locomotives are nearly 10 times more efficient than diesel trucks at moving freight.

The largest freighters are now being built with diesel electric hybrid systems, as well as the US Navy is now expanding their fleet with diesel electric hybrids.

Their subs are nuclear powered, and the steam used to be piped to 2 huge steam turbines which turned a 20ft tall reduction gear spinning a single shaft and huge propeller. They also used 2 steam generators (SSTGs) to produce electrical power to control the reactor and provide all ship's power, including hotel services. The newest generation will be powered by electric motors attached to a much shorter shaft, fed by larger SSTGs.

I believe it's safe for me to mention that their huge propellers have changed design, they now use a shrouded screw, vs the open screw of the past. This allows greater power application before the onset of cavitation at various depths, more efficient power transfer and higher top speeds.

This efficiency also translates to cars as well. VW is well versed in diesel engines with their TDI engines getting around 50 mpg, but their XL1 diesel electric car got 300 mpg, even though it only goes 22 mi on the batteries, it's primary power source is a 1l diesel engine, powering a 27hp electric motor.

There's no reason why a similar, properly sized diesel electric hybrid powerplant couldn't be installed on a sailboat.

[TheThunderbird]

I see hybrid future soon!

Mastervolt has listed a diesel - electric engine combo.

They may add to the other in need, like on Porsche 918 :-)

Ability to sneak noiselssly in coves and marinas, while keeping long range ability..
And please,let's take it down to 3-4 BHP/tonn, please!

[TheThunderbird]

@socaldmax
Be careful
On large ships, diesel works onto a dynamo, since electric transmission is easier to control and transfer efficiently. In the end, thou cant escape IC :-)but can better compound reserve of energy, peak requirements, engine room, maintenance etc on a global, full life approach :-)

[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.

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.

[RaymondR]

Also power from electric vs ICE is different. Electric motors develop full power at initial rpm but diesels only develop full power at much higher rpm. Depending on the engine and design in the range of 1500-2500 rpm.

I think DC motors develop full torque at initial rpm rather than full power. If stalled they develop full torque without rotation and at max freewheeling speed maximum rpm without torque so the power curve tends to show maximum power as about mid speed.

[med]

Originally Posted by 44'cruisingcat

At least in Aus, there are small turbo-diesel cars that use less fuel than the Prius, cost less to buy and are much better to drive.

In europe for the same price as the Prius you can have a Mercedes C200. This has the same mileage and IMHO is a much nicer drive.