Diesel Electric Propulsion

I believe such a motor could also be configured to serve as a shaft generator. Shaft generators are common in the merchant marine (the big main propulsion engine will always be more efficient then the much smaller auxiliary engines).

Hi,

That is what the words say, not sure he actually means it just like his leaching protection off two aluminium boats.

Zinc protection

Some years ago, the German Navy had two fast PT boats in a yard at the northern part of the Weser River (Brake), for maintenance and major overhaul. Moored next to the PT boats (made of Alloy) was a historical wooden sailing ship with its belly nicely covered with copper. Needless to say, there was a "lot of damage" to the hulls of both PT boats, because the boats were in for new underwater paint and renewal of the anodes. I bet, you could light an electric bulb with that galvanic current in the water.

Why not... leach! Beside designer interiors are expensive and every penny counts.

The idea of a shaft / flywheel / gearbox mounted generator / motor is an old one. The propulsion engines are disconnected / clutched to the drive system.

Underway in transit mode main engines supply propulsion and provide generated power to the grid powered by the main engines. The ships service generators are turned off.

In trolling mode around the harbor the motor / generator powers the propulsion taking power of the grid supplied by the ships service generators.

In high speed mode the motor / generator can be supplied by the ships service generators to add power to propulsion... add a little bit to the top speed.

Sizing is the key what proportions should the system be as to capacity of the main propulsion engines, ships service generators and shaft motor generator.

If one goes to the added complication of a hybrid system with battery storage likely this is more complex.

But I think the shaft motor / generator would be in the range of 10-20% of the power output of the main engines... the ships service generators about the same capacity. Like and example of a 40m displacement yacht twin propulsion engine yacht:
500 KW main engines... 13-14 knots top speed
50 KW shaft motor generators... 7-9 knots top speed electric
100 KW generator sets... 3 generator sets but it could be done with 2.

Underway in transit rather than 40% loading on mains you would be at 50%
loading... but the shaft generators would power entire yacht electrical.

Trolling around mains off and two generator sets running at 80-100%. And yacht able to do about 7 knots perhaps.

I think going to 100KW motor generators would be Ok but you would not get much extra speed for the effort.... but you could run on one for ships service under transit conditions. But this would likely mean definitely the 3 total 100KW gen. sets.

I think this is about the practical sweet spot with some small adjustments.

Hi,

Run it on your small boat and let us know how it goes.

I am currently looking at a much larger project and the weight and cost of a DE install currently outweigh the benefits as the operational profile of this yacht is a lot of time at anchor and some short runs with a few long ones every year.

I have suggested that we run one shaft genny/motor instead of a 4th main genset that could be used on passage, this will be a weight and space saving in itself plus we don't need room for another 500mm Exhaust Pipe to travel through the interior to the outside.

K1W1,

You have exactly hit the nail on the head weight and cost... and complication are upside down on diesel electric for reasonably sized yachts... well if you're building a cruise ship OK. I would love to do a diesel electric or even hybrid... but so far it is fantasy musings.

Whatever configuration you can come up with unless you are willing to invest significantly... sort of like Tom Perkins and the Maltese Falcon... it don't add up... I suppose everyone notices he has downgraded significantly despite his wealth growing... and the huge loss on the Falcon. I have similar situation where I really don't want to go bigger and more complex... but simpler with more quiet reliability and enjoyment.

So I use the forum to muse on ideas... but cannot get excited about signing on the line... . And, just hate the boat shows and broker scene. Its like some guy was talking on the forum about a large cat like Hemisphere... wonder if he knows Derecktor situation on that... .

I was looking out the plane window a few days ago and saw a yacht transport ship and on the long flight got to musing on that too... maybe yachts don't need the complication of propulsion and power generation plants... . Maybe the solution for many would be a fancy barge like one of the 'island' concepts... and get it have a water tractor tug to transport it from place to place... and all the equipment bother on the tug and just an umbilical cord between... at anchor... or in remote locations... and park it at the berth and hook up to shore power otherwise. Or just get it commercially shipped from location to location... with a floating power supply (and the noise and bother) tethered off the umbilical otherwise.

Forgot... the "island pleasure barge" could have some of the telescoping anchors like Jongert has planned on the 5000 LE concept... doing away with anchors and chain too.

Don't Throw out the Baby with the Bath Water

This diesel-electric subject thread has certainly raised some lively and controversial discussions. Many want to claim that converting diesel engine mechanical power into electricity, and then back into mechanical power by an electric propulsion motor, just isn't economically feasible. Therefore chuck the whole idea aside when contemplating DE propulsion systems for boats.

I say don't 'thrown out the baby with the bathwater'. This technology is still in its infancy, and there are many more developments to explore....and some may come with other emerging technologies.

One of these new technologies will likely be the ever-increasing capabilities to store electrical energy....new 'batteries', or other such devices and mediums. This capability to store large amounts of electric energy is a technology we sorely need for our future in all sorts of endeavors, and I'm sure there are presently 100's of experimenters around the world working on this major technology.

I agree Innamore. For a strictly powerboat application that spends a small amount of time idling about or maneuvering at docks, etc, and subsequently mostly at speed on the open water, D-E does NOT make sense.....too many energy conversions between main motor and the prop. Thus many powerboats are not applicable DE candidates.

But one thing those DE systems do is break the mechanical link between the engine and the prop. This opens up a whole lot of possibilities for locating the main engines apart from the drive-props, and even the variety of prop-drives that might be employed.

For vessels with big house loads, a DE systems approach makes sense, as well illustrated by the big cruise ships.

Special maneuvering desires can be accommodated with DE systems. A diesel electric system can be shifted from fwd to reverse and back much more quickly than a conventional transmission. In addition the electric motors develop full torque at any speed, even down to 0 rpm. In conventional propulsion installations, the idle speed of the engine will be between 700-1000 rpms. With a typical displacement hull reduction-gear ratio of approx 2.6 to 1, the slowest propeller speed is 270rpm or more. By contrast, a DE propeller shaft can be turned as slowly as 1-rpm!

Furthermore DE systems are much more adaptable to 'steerable prop-drives. Talk about maneuverability!!

If we move beyond ' strictly powerboats', then we might see a use for DE systems aboard wide variety of other type vessels. I'll just give two examples where I wish to use them:

1) Sportfishing Vessels.
Whether pleasure or commercial types, these vessels spend considerable time in the 'trolling mode', usually quite a bit below their cruising speed. This trolling speed might well be accommodated with a DE system.
Gamefishing Catamaran


2) MotorSailing Vessels.
In light airs, running one engine often is all that is needed to bring the apparent wind forward to make the sails work harder, and the combination provides much better results than either motoring or sailing alone…… sailing synergy/harmony, the motor taking over in the lulls and the rig taking over in the puffs

Motorsailing offshore is by far the most pleasant way to make passage, most of the time. With the engine barely above idle and a moderate amount of sail set, there is a synergy created by the apparent wind which generates more forward thrust than either one alone, with the bonus that you don't have to set large areas of canvas, which will have to come down in a hurry if the wind increases. The boat rides better, makes a better average speed and the batteries are always full. The beneft of using a much smaller sailplan can only be appreciated by someone who's been caught offguard in a squall with too much sail up. "Adventures" like that might be fun for weekend sailors and short coastal passagemakers, but on a long ocean passage they're something to avoid, even if it means a slower passage.
Motorsailing Catamaran

3) Etc

New Publication

For those interested, a freshly new magazine on these matters is on the market:

"Electric & Hybrid Marine Technology International"

Electric & Hybrid Vehicle Technology International

Rim Drive Propulsion

Dear Karo,
I've not had time to review all of your recent postings on this subject, but two items have caught my eye. (and I do thank you for that input)

1) Do you really think that all of the answers to my questions are the same as 40 yrs ago? Are not the host of new solid state 'controllers' changing some of the 'equations',.....making possible some components and systems that just were not possible before?

2) I wasn't able to fully understand some of this technology in the development of Rim Drive Propulsion units that you addressed,.....nor that were addressed here:
https://www.escholar.manchester.ac.uk/api/datastream?publicationPid=uk-ac-man-scw:134227&datastreamId=FULL-TEXT.PDF

I brought this link to this paper up over in this dedicated discussion to Rim Driven Propellers over HERE:
http://www.yachtforums.com/forums/technical-discussion/3961-rim-driven-propellers-4.html

Seeing as how you really like to dig into the specifics of these 'electrics', I thought it would be interesting to hear your comments on this PHD paper.

And it might well be a good idea to post your comments over on that Rim Drive discussion subject thread?
Thanks, cheers, Brian

Brian:
First your posting on the new magazine was very appreciated. I think that first issue pretty much covers the state of the art technology in marine hybrid and diesel electric drive.

I will read the paper on the rim drive motors etc you posted... but in glancing through it... it is a very good description of the technologies involved. As you notice it is 248 pages long. I will learn a lot I am sure.

The issue in posting here and trying to describe the technology and the core issues is very hard... is simply to describe the technical challenges in general understandable terms to most forum members. So I try but the core issues in marine diesel electric propulsion as to yachting are hard to generalize in technical detail but this is what I understand they are in a larger sense:

Mass and volume vs power output. Power densities of the entire installation. If the overall system is hugely larger and heavier than conventional system it makes the system impractical. This is the number one technical driver.

Specific fuel consumption per unit of propulsion. That is how much fuel does it take to power a given propulsive horsepower. I know that this is a factor but the numbers are not hugely upside down.

So my belief is that owners will accept less fuel effeciency for additional quiet reliable enjoyment. I pay not personal interest in the "carbon reductions" so common now... only applies if you are running a nuclear system. If you have a hybrid and store generated electricity (created by carbon consumption) what does it matter if you produce it or a power plant does.

Technical complication. If the system requires too much attention in maintenance and operation, and gathers too much expense in those areas it interferes with the quiet reliable enjoyment of the yacht. These can be significant cost drivers and aggravation if the yacht proves unreliable.

In a yacht the intent is to have as little machinery interference with quiet reliable enjoyment of the marine environment. I consider the target use size of yacht would be 30-50m, and that is in the emerging technology category for diesel electric marine propulsion. Why not larger... those are a rare breed and basically billionaire only affordable. And, I think having a cruise ship sized yacht defeats the purpose in the first place unless you are trying to win questionable friends and influence important "meaning richer" people. One more comment, when I am looking at a yacht or at building my concern is what is the maximum use and space I can get in a given size. Size relates to cost and complication... as these increase in geometric progression in relationship to size. Geometric means an exponent "power" is involved in the equation for the number of increase. Besides many of my favored ports don't accept "cruise ship" sized boats, and the 'ladies' absolutely hate anchoring out... and also the getting in and out of intermediary boats and the ride to and from... heavens the gang plank is often proves a bearer to the enjoyment of the outing.

I really don't see diesel electric has being impractical unless perhaps you add in batteries or maybe fuel cells. Both of these are heavily dependent of type. Notice Boeing has a fleet of new jetliners grounded for some time with "battery problems". Does anyone think more engineering effort is applied to a boat than an aircraft! Only in the case of nuclear power is that true. Usually I have found electrical equipment is easier to maintain and more reliable than the turbines and engines that power it. But batteries added in and that goes upside down. And, I worry that the newer batteries are dangers to life at sea.

Now the comment of the 40 years ago. Is true. Yes, you can purchase electronic drives and power supplies and controllers and PM motors of all kinds, now-a-days. But nearly everything I can think of existing now has been of use in aerospace for a long time. Much of it was invented in the 1950s... but not available over the counter until the last twenty years or so. The toothless PM motor/generators invented by Joe Denk (a hungarian immigrant to the US) at Allied Signal are really the only new motor/generator concept in the last 30 years other than variations on older concepts. But he did this 25 years ago or so. The US Army experimented with rim drive propulsion motors for trucks (wheel motors) in the late 1950 through 60s is one example. Samarium Cobalt electronically commentated motors / generators were used in many advanced aerospace programs in the 1950s and 1960s... some of this was classified. As I have posted on this forum the electronic fuel controls now common on diesel engines invented and proven done in 1957-1958 by my friend Warren Boardman at Marquardt Corp...

Brian I always your posts are very well thought out and very interesting and informative. Mine tend to edge on the dreamer at times but I think that adds interest. I really don't have the time to really investigate this matter fully but do like to dabble as a little intellectual get away...

Fortjes Pod Propulsion from Reintjes

Dear HTM09,
Are you familar with this pod propulsion system, FORTJES pod? What do you think of it.?


It appears to offer a number of good features, and being a 'pair of counter-rotating props' (one at each end) it could provide generous blade area in an overall shallower draft unit, and a simplified engineering as co-axial shafts are not needed.....other features as well.

https://www.navalengineers.org/ProceedingsDocs/FAST2011/FAST_C/C7-2.FAST2011.Weber_Schulze.pdf

http://www.reintjes-gears.de/fortjes/pdf/fortjes.pdf

Claimed to be 30% less fuel consumption in one installation?
Break-away capability, and other features....

Yes I am. It combines the Pod drive with the advantage of the counterrotating prop. The counterrotating prop converts a large part of the centrifugal force of the thrust into forward thrust, if made correctly!!!! Just like counterrotating propeller on some military aircraft.

But the Reintje pod does not turn. It needs a rudder behind and therefore destroys part of its advantage.

I have heard, the had to fix it for some reasons ????? This pod with 360 turn angle and the electric motor build gearless in its vertical shaft would be the most ideal and effective DE pod drive in the world (for yachts). Both for efficiency and performance. But even as a mechanical pod drive with gear and shaft to an conventional diesel engine would be great, if it would turn.

The greatest advantage with this pod drive would be, it is usable both for displacement and planning hulls with different props and gear ratio. There are most likely some kind of legal reasons behind all that. Volvo Penta IPS, ZF Zeus, Schottel and Reintje, they are all fishing in the same pond. I cant say more.

- Reintje will not build turnable drives for some reasons.

- Schottel will not build counterrotating props (for simplicity ?).

- Volvo Penta owns the counterrotating pulling prop with internal exhaust.

- ZF owns the counterrotating pushing prop.

- Schottel owns the Twin prop and rudder propeller and SCD

I have no solution for that mess. But this excisting Reintje pod drive could be adapted to existing planning hulls even with prop tunnel. Part of the design is the assymetrical airfoil of the shaft fairing. It would at least be much more effective than these 20 degrees downward pointing standard shaft drives.

That is strange isn't it

Pod Drives (DE or mechanical)

All those companies like Volvo Penta, ZF, Schottel or Reintje have excellent engineers and are industrial leaders in their market segments. But they all have this Apple and Samsung syndrom.

They know exactly how their product would have to look like, to be just perfect. But everything or at least parts of it have been invented or developed already and are covered by Patents or trademarks of somebody else. So, they develope a variant or even something completely new, just to stay outside patent coverage and legal trouble.

Volvo Penta for example owns all patents and legal rights of the (IPS) Poddrive System with counterrotating pulling props and intergrated exhaust system. They were the first. And it can be mounted directly to the bottom of the hull, excepting existing deadrise. The pulling counterrotating prop is the most effective, because it chews undisturbed water and the exhaus gases exit within the laminar flow propeller stream and exit the water far behind the boat. Easy to install, works excellent in pair or quadrupple arrangement. In tripple arrangement the middle pod is blocked in the center position, because the steering computer does not know, what to do with it. So you either install 2 or 4 IPS. It works with 3 pods also, but not as effective, 2 pods are the minimum, single drive does not work. Biggest disadvantage, the system is only usable for planning or semi planning hulls and you are stuck with Volvo engines.

All other companies had to come up with a new approach for the same task.

ZF uses pushing counterrotating props but the pods have to be mounted vertically. That means, the hull has to be specially designed (pod steps). Biggest advantage, choice of engine manufacturer and even single drive is possible. Up to now not as many different types available. It seems to have better break away capability, less damage to the hull, in case of ??? Also for planning and semi planning hulls.

Schottel lives in the big and heavy commercial world and just starts to look for yachts and smaller river cargo and cruising ships. Their systems are ment for the displacement market and are not easily adaptable for planning hulls. Because their pod drives are designed for much higher torque and power transmissions, Schottel is very reluctant to adapt the counterrotating principle of Reintje because of its more filigree design.

So, what was left for Reintje, they were last in the race. What you see is their answer to paticipate on that cake and stay out of legal trouble.

One should force those companies to cooperate and put their ideas together for the ideal DE or mechanical pod drive. But here we are back to the Apple and Samsung problem.

"It is easier for a camel to go through the needles eye than profit-orientated companies working together"

Cheers

Turning the mechanically driven pod is a bit problematic. All the torque that's destined for the props is turning away in the vertical shaft. If you have any resistance to the props turning (say a gear chips and the fragments end up in between the teeth) then suddenly all the mite of the engine is working against whatever is holding the pod still. If it's a little electric motor there to turn the pod it can probably be overcome with negative results.

Hi,

It might surprise you to know that Outboard Motors and Stern Drives have a very similar arrangement in their gearboxes, gear chips sufficient to jam the thing up are not very common in well manufactured and maintained constant mesh gears.

Not at all surprising, it's just a possible reason (an answer to HTM09's question) for why they would choose not to. I suspect that gears chipping are an infrequent reason for problems, and it was just one example off the top of my head of something that could happen, not a weakness in the gear arrangement, but even the best gears occasionally with chip off a little fragment, nothing lasts forever. Something happening to jam the apparatus and cause the torque that drives the prop to come largely to bear on the pod from whatever source probably happens often enough to warrant needing to plan for it and take care. A line fowling the prop would have probably been a better, and more common, problem to illustrate the situation. It's not an insurmountable technical problem, I think that Volvo Penta IPS uses a shaft and much the same gear arrangement, I just wanted to present a reason why someone might decide not to make such a pod azimuthing.

Forgive the commercially thinking boater, but it is all about costs and amortisation and profits.

Some years ago, we asked ZF for a special designed gearbox in the 1500 KW range. They said, it costs us more than a million Euros to develope this version. And then we need to sell at least xx numbers of it, in order to make a return and a profit. So, it is better, that you (as the customer) build your ship around one of our excisting gearboxes. A company, well known for its flexibility, made the deal and it did not cost millions.

Will say, profits on pleasure boating equipment are not very high. They make their profit by numbers. Making changes or being flexible is counterproductive for them. The only way for the customer to control and direct the evolution, is the way how and what he buys. As long as the old stuff is being bought, they will produce it.

If you would know, how old the basic designs of some boat engine blocks are, you would be surprised. And that counts for all companies.

Cheers

Every new design is a new chance for something to go horribly wrong.

The space shuttle has now been retired, but before it was the flight computer systems were never once upgraded. A computer system from the late 70's ran until 2011. They chose not to upgrade it because the extra functionality, weight savings, and power savings that they might achieve wouldn't be worth it if anything went wrong. A space ship is a different kind of vessel, but the logic is sound for all ships, reliability is a golden asset.

Edit: Turns out it was upgraded in 1990. The entire system was the same, except that they changed out the memory and processor, swapping gear developed a decade prior for gear developed 12 years prior.