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Diesel Electric Propulsion

Discussion in 'Technical Discussion' started by Crewagency, Nov 26, 2004.

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  1. karo1776

    karo1776 Senior Member

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    I am an electrical and nuclear engineer by training...

    Couple of comment... NO FREE POWER... violates fundamental laws of thermodynamics and physics.
    You can improve the entropy situation (the energy unavailable in a system to get useful power/energy out of the system) but that is not free power out other than its a capture of that lost.

    Actually, DC machines are usually commentated internally... as the fundamental of the arrangement of the electromagnetic parts and the rotation only produce AC.

    In this case, I was talking about very simple machines that have permeant magnet rotors and wound stators. These produce wild voltage and wild frequency depending on the speed of rotation the voltage and frequency output vary.

    Note: To get DC power out... of such a simple electromagnetic machine which produces AC output... you have to electrically switch the leads coming out of the machine to get DC or convert it... in conventional DC machines the bushes and commentator combination do the switching mechanically...

    To get a particular voltage for the hotel loads the wild voltage needs to be electronically modified. But for propulsion it does not as the same simple machines
  2. HTMO9

    HTMO9 Senior Member

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    As far as yachts are concerned, I was more asking than making statements,
    because this is not my primary business. The exact amount of savings are
    not known to me. But I know their purchasing costs and they reduce Gen
    hours.

    For cargo ships my statements are proven and measured and reflect my
    personal experience. You are correct, their is no free lunch, but for ship
    owners it is only important whats under the bottom line. The majority of
    single engine cargo vessels (like feeder ships, small tankers and special
    cargo vessels) in Europe are equipped with shaft generators like shown
    above. There is no fancy business behind them and they are cheaper
    than another Genset and work flawlessly. At least the Ones I operate
    and own! And with the new full DC technology, this setup will work
    even better and more simple.

    On the bigger ships we operate with exhaust heat recovery steam
    turbines and exhaust gas turbo generators (not the turbo chargers)
    on the big 2-stroke diesel engines. That is why big ships are so fuel
    efficient. We achieve specific fuel consumptions of down to 157g per
    KW and hour. With the standard diesel, you will be happy to reach
    200g/KW/h. And that might be the difference between winning and
    being out of business today, because the difference in fuel costs may
    eat up your profit margin.

    If we would have denied all inovations in history, man kind would still sit
    on trees.

    Cheers
  3. Marmot

    Marmot Senior Member

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    I was speaking from the point of view of someone whose current primary business is large yachts and came to this business from the deep sea liner trades where shaft generators are a useful item.

    It is a bit disingenuous to imply that the small PTO generators used on small coasters and feeder ships provide the same numbers to small medium speed engines as waste heat recovery provides to large slow-speed engines operating in the liner trades rather than coasting. Those are two very different types of service.

    I am far from a Luddite or stodgy old steam chief but it is easy for me to say that both of those applications are far far from the type of service all but a very tiny handful of very large yachts will ever see and implying otherwise may be fun but hardly realistic or even on the distant horizon.
  4. HTMO9

    HTMO9 Senior Member

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    Marmot

    Dear Sir,

    Thats why I was asking more than insisting. I have lived my business
    live in the commercial shipping world and I am now planning my / our
    retirement boat. I am on the forum to learn and I do appreciate your
    arguments.

    This discussion is very informative for me and our arguments are not far
    from each other. If it turns out that my ideas in yachting are not worth
    it, I will have learned and I will save money and anger.

    Cheers
  5. Marmot

    Marmot Senior Member

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    There are lots of ways that "commercial" energy management might (and probably should be) applied to large yachts. If you have the cash and the inclination, waste heat recovery is a very good place to start. A small jacket water heated evaporator like one of the Maxims or an Aqua instead of an RO unit is one place where off the shelf items could present real savings.
  6. HTMO9

    HTMO9 Senior Member

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    What I mean with sinergy effects for example is:

    I have been a guest on a friends 187 ft yacht. 2 x 1492 KW engines,
    2 x 270 KWe diesel gens plus emergency gen. During cruise at 14 Kts,
    the engines consumed about 300+ Liters per hour each plus the
    fuel consumption of the gen(s). The ship had two large hot water boiler
    heated only by electrical energy. The ship could only be heated in cold
    weather by the reverse mode AC. Why not using energy which is there
    and otherwise wasted like heat from the engines cooling water or hot
    exhaust. That could be used via heat exchangers to produce hot water
    and to heat the chilled water circuit of the AC system.

    If have seen more things like this on large yachts. On commercial ships
    were money counts, using process heat for services like this, has been
    standard for many years.

    I know, the approach is, keep it simple and equipment which is not there,
    cant break. But EPA Tier 3 and 4 are comming, plus fuel cost will only go up
    and never down again. It will just make me feel better to have a fuel
    efficient and "green" yacht when taking delivery. If I will have to pay a little
    more for that, thats the way it goes.

    Cheers
  7. Marmot

    Marmot Senior Member

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    I agree with you 100 percent. However, the underway time of a yacht is so very small that the cost/benefit is difficult to justify.

    The other side is that adding complexity means that a cellphone enabled engineer can no longer maintain the systems. Most of them don't even understand the concept of waste heat recovery and heat balance.
  8. HTMO9

    HTMO9 Senior Member

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    I know what You mean. The unattended engine room !!! That reminds me
    on my first year as a combined master and engineer. My father gave me the
    command over our oldest and smallest cargo ship in order to gain experience.
    I have never rushed more steps up and down from the bridge to the engine
    room and back in my whole life. Those oil monkeys in the basement had no
    idea what they were doing. Due to the endless mercy of my father, i was
    given a better and bigger ship with a competent engine crew later.

    I have looked up some figures in the our paperwork. On a given ship with
    single main engine and 3 diesel gensets compared with the same ship with
    two diesel gensets plus shaft generator we saved a bit more than 20.000
    US $ in maintenance costs per year, fuel savings not counted. During cruise
    the ship works on shaft gen only, diesel gens switched off, during
    maneuvering and very slow speed, the diesel gens are started and the shaft
    gen is switched to bow thruster.

    Again, I do not want to proselytize my opinions, I just want to learn from
    the vast combined knowledge of this forum, whether some of this
    technology could be downscaled and used for yachting.

    I have asked my R&D department for some of this points, but this forum is
    a high value second opinion to me.

    Cheers
  9. karo1776

    karo1776 Senior Member

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    I think you should look over Voith Marine and some of the products they engineer, build and sale. They have a nice waste heat recovery system using exhaust gas from convention high and medium speed diesels using a steam cycle... used in rail and tug applications as far as I can tell. They are promoting for yacht service.

    Their website is very interesting if you explore. One idea I derived from it was using for a yacht a similar design as to their water tractor tugs.... for hull and propulsion design. It is very different but I suspect yacht and tugs have a lot in common... yes I know that sounds strange. Both do go on ocean trips but not anything like a merchant ship... in other words seldom. Heavens many yachts never see crossing being ferried across. But both spend a lot of time maneuvering in the harbor and now-a-days the yacht harbors are rather tight and require high maneuverability. It has given me ideas on the motor boating side of the world.

    Of course, you could look at the sail boat side of things... which I love. My maternal Grandfather retired from the Merchant Marine as a Master not long after WW2 and he said given the choice he would have a sail boat... due to the noise and machinery aspect. But ultimately he had an impatient nature and though a good sailor he had over time become so used to the powered freedom he could not quite accept a sail boat. Best dead reckoning navigator I know off... Scotsman with a knack for knowing where in the hell he was.
  10. HTMO9

    HTMO9 Senior Member

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    I was lucky, I only had to walk up the ladder in the company until it was
    handed over to me, but my old man (still happily alive and almost 100 years
    old) was forced by his father to start his marine life as a ship-boy on one of
    our square riggers and sail around cape horn. When I listen to his memories
    today, I must say, if anybody would have forced me to live a life like he did,
    I would not be involved in the maritime industry today, period !!!

    I am quite fimiliar with the VSP system. It is very effective, gives great
    bollard pull, makes the boat very maneuverable and is very reliable. Great
    propulsion and steering system for tug boats, ferrys, workboats and ships
    which need dynamic postioning capability.

    But for the implementation into yachts a few points have to be concidered.
    VSP systems are a complex piece of machinery with a lot of moving parts
    (our professor in university, on lectures of mechanical engineering, called
    them a collection of spare parts which fight each other). They work perfect,
    if used daily and all day long. Plus they need proper care and maintenance
    and a spacial hull design (also to protect them) and arrangement of the
    engine room.

    Lets take the example of a typical 500 GT, 150 ft displacement yacht. The
    1000 KW version of the VSP has a system weight of over 16.000 kg and you
    need two of them. If you want to avoid a very long drive shaft with multiple
    couplings, bearings and angular changes in the drive train, you end up with
    the engines also at the stern. On our given example with 2 MTU 8V 4000 at
    1000 KW including gear of 5500 kg each, you end up with 43.000 kg of
    machinery plus all the rest of the engine room equipment at the stern of your
    boat. And that is the place were the buoyancy is at its minimum. It is the
    perfect propulsion for a tug, were the VSPs sit in the front part of the hull
    and the engines with straight shafts in the center of gravity. And I do not
    believe, that a full scale diesel electric propulsion is economical on a 150 ft
    yacht.

    If I remember correctly the study I have red (K1W1 will know much better),
    the break even point for a diesel electric propulsion on a displacement yacht,
    as far as engine room space, weight and costs are concerned, is around 250
    ft upwards. Yachts of this lenghts are normally build for top speeds of around
    20 Kts. This speed cannot be provided, to my knowledge, by a VSP system.


    The other point is, if you ask one of the famous northern European yards for
    building a yacht in the 150 to 250 ft range, they will try to sell you one of
    their proven hulls with your choice of design of the superstructure and the
    interior. A complete new hull design with all the R&D and tank testing will be
    either very expensive or will costs a lot of time because of their engineering
    and naval architecture capacity.

    My personal problem is, my female home commander (beloved wife) has
    decided, that my / our retirement boat has NO sails (sailing in northern
    waters to her means, always freezing, end of statement)! We want to
    take delivery of the boat in about 3 to 4 years time. So, I have no time to
    reinvent the wheel.

    Cheers
  11. karo1776

    karo1776 Senior Member

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    Still worth considering... but its one of those situations where you have to get Voith to do the up front engineering and help with the yacht naval architecture... not something to add on latter or ad to a current design.

    I see the issue of mass on a displacement yacht to be little issue other than in the design stage.

    The issue of shaft drive... in a diesel electric thread... !!!

    The reliability is from what I understand bulletproof.

    I suppose I would just hire them a the propulsion sub contractor and they could supply the whole engine room propulsion section of the boat as a unit to be assembled to the rest at the builder.

    Most luxury yachts cruise around in the 8-14 knot range anyway... maybe a few see 16 regularly but very few can afford that size of boat.

    And, they are darn quiet...
  12. HTMO9

    HTMO9 Senior Member

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    It fits in the diesel electric thread because in a none tug boat
    enviroment, the VSP will be best suited as a diesel electric setup,
    because than their is no shaft drive issue. It will work on a yacht
    which travelles a lot, because VSP do not like algae and mussel groth,
    due to bearing and sealing problems plus inbalance and lowering
    efficency. I am not able to recall the propulsion efficiency of a VSP in
    regard to a normal propeller or a pod drive at the moment, but I will
    find out.

    I would like to tell you my favorite DE setup for a larger yacht:

    Array of diesel Gensets of MTU 16V4000 and/or 16V2000 with oxidation
    catalytic converter and particle/soot filter with diesel rearheat into dry
    exhaust stacks. In order to prevent soot residuals on the boat, the top
    of the stack would be equipped with spoilers to direct airflow and soot
    away from the boat. Their was an excellent article (from Lürssen)
    about this subject in the boote exclusiv magazine.

    For propulsion, I would use a pod drive from Schottel. As I personally
    beleave that water and electricity do not belong together, I would take
    the Schottel Combi Drive (see picture). A very simple design, very easy
    to install and the electric motor is outside water combined with a very
    small and sleek underwater part. In combination with a Schottel
    Pumpjet, It would be a very maneuverable boat (DP) and would give a
    very smooth, silent and vibration free vojage.

    The only problem with this setup is, I do not want to build another
    Topaz yacht. I may transport oil, but it is not my oil.

    Cheers

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  13. karo1776

    karo1776 Senior Member

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    I think that is a very sensible solution. And, it is one I'd would likely go with the Combi-drive too, although, the VSP is intriguing. Actually, have all of Schottel information in my "new boat ideas folder". The primary advantage of the diesel electric is elimination of the drive shaft and freedom in arranging the machinery in the yacht. I would recommend going with fewer gen sets than more... two large and one small for in port... and placing so for easy access for changing out the entire piece without disassembling the entire yacht.

    After having to change a shaft intermediary bearing in mid ocean... once a long time ago... I cannot dispute... diesel electric. No one much thinks about it but those (conventional drive shafts) when they go wrong it is worse than a serious engine problem due to accessibility issues.
  14. K1W1

    K1W1 Senior Member

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    Hi,

    The AMELS Yacht Maupiti now Karima was built with 4 x 3508 gensets and 1 x 3406 set.

    This set was worked to death and was not in anything like an easy place to extract.

    When using a std AC Bus you will have much better power management with the use of several smaller ones instead of running two big ones at 50% you could run 3 or 4 smaller ones at MCR.

    The Combi Drives are great, I speced them for a boat that was supposed to go to Fassmer but it never happened.
  15. karo1776

    karo1776 Senior Member

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    K1W1... I suppose you are right on the large number four gen sets and emergency. And, certainly you have much more experience to draw on.

    Yes, that no place to slip them out and replace easily is just poor engineering and short sightedness.

    As age and the family situation deteriorates as to ability to enjoy a snail boat... and the motor boat is looking more and more like the right situation.

    I have very seriously considered this set up on a 40-45 meter motor boat. But not to any place far along enough ready to jump in though. The problem I have is the mass of the gen sets being larger than I would prefer. Just in my opinion too heavy... as I would like to go with an aluminum hull which is ballasted much like Huisman did with Arcadia. See my thinking was to have the generator room fwd of the garage, stern opening, and have the bulkhead between the two removable (bolts or rivets) for service on the gen sets... just slip them out and replace rather than the bother of rebuilding in situ... just buy new better overall value and less problems with all the little things than rebuilt. But on serious evaluation the issue was they would be in a line and too close across the beam, four across... if mounted transversely then you end up with two rows in each direction... the best set up as to the one large engine room space... but the drives would be in the garage and that complicates and enlarges the garage too. Remember the drives stick up and you are not going to have floor area over them.

    So the idea was floated of a more fwd. garage with side opening doors and short two engine / auxiliary rooms fwd and aft of the garage... with two gen sets in each. But this adds to overall length and you know what that means as to displacement of the boat Mass cubed and costs to the 4th power. Though my opinion is its not fancy guest space just machinery space... but somehow that don't count in the yacht building world as much as it should. And, importantly, the garage doors need to be shut when conventionally berthed stern to. Also, as the length goes up the operation situation changes as to costs and where you can berth the darn thing at home and elsewhere. So that was the driver in my thinking on the two bigger sets, and the side opening doors hurt this too.

    So my opinion is that on a boat under about 50 meters it becomes just very much more difficult... and maybe for now diesel electric should be confined to the larger boat... where I think it makes huge sense.

    I suppose turbine gen sets would just be the thing... but I have no inclination of going through that engineering effort or increasing fuel bunker space and costs 30-40%... along with the associated maintenance costs down the road... those you do rebuild but it is a send in to a manufacturers facility deal.
  16. K1W1

    K1W1 Senior Member

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    Hi,

    I was onboard MAUPITI in Cairns in late 1998, they were cutting a hole in the hanger inner wall to allow refitment of the afore mentioned 3406.

    It had previously been removed in Singapore and re manufactured by the area CAT Dealer. Not long after returning it to service it dropped a valve and was out of action. It had to be removed in New Guinea and returned to the dealer in Singapore to rework it again.

    Because the hanger was open to deck and the penetration to remove the genset was into the engine room it was re welded each time.

    The only saving grace being they could get the engine onto the helicopter elevator and lift it up to deck level.

    The use of soft patches is a very good idea, I have introduced these to a well known yard and they are now standard fitment.

    You could look at having a garage just forward of Frame 0 and have your pods and gear in the space aft of this.

    Look at the Lurssen yacht ICE she is pretty much arranged this way.

    Turbine gensets are fine as long as the load is constant and is right in their designed power band, drop the load and the fuel burn will make you wonder why you fitted them.
  17. HTMO9

    HTMO9 Senior Member

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    The fastes thing on a diesel electric yacht with a turbine powered generator (like a vericor TF 40) would be the pointer of your fuel indicator going towards empty. The TF-40/50, the best (and only) available small gas turbine for genset purpose on the market has a SFC of about 265 g/KW/h and has an output of 3000 KW or more. And you would be the most loved boat in your harbour (noise ?).:)

    But there is one possibility to get a smaller genset or a genset with more power. Taking a genset with a given diesel engine. This engine for example is rated at 1800 RPM for continuous operation. But in your 50 Hertz Genset you have to run it at 1500 RPM in order to get your AC frequency. So, if you want the power, this engine gives at 1800 RPM, you need a bigger engine or may be a larger number of Gensets. Why not have a (reduction) geared generator. The Diesel engine is running at the rated speed of 1800 RPM, but a bigger Generator is running at its wanted speed of 1500 RPM with higher output. Or the other way round a smaller engine for the given generator.

    On smaller pleasure boats they can take the easy way. With smaller boats, the average genset gets less than 500 hours a year. They can use a 3000 RPM genset with a perfect cocon (like Fischer Panda). Almost half in size and weight in comparison with with a 1500 RPM Genset. With a projected lifetime of 10000 hours for a high RPM genset durability is no issue.

    But still, as far as engine room size, weight and costs and complexity of a DE setup are concerned, I do not see a 45 to 50 meter DE yacht. I would love to see it, if it would be possible or would make sense.

    I can see the shells of your arguments already flying. You are cleared to fire gentleman.:D
  18. K1W1

    K1W1 Senior Member

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  19. HTMO9

    HTMO9 Senior Member

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    I know that but If one would like a 50 Hertz boat. The 60 Hertz users are always in advantage of their 300 more RPM.

    The turbine shown at 200 eKW was developed from an aircraft APU. The durabilty of this small turbines in extended use over the year in maritime enviroment has yet to be proven. But smaller turbines are comming. Like You said, the worst thing you can do to a turbine and to your budget, run it outside its optimum envelope.
  20. K1W1

    K1W1 Senior Member

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    A 50 Hz hotel service can easily be obtained by Static Inverters such as ATLAS, if you are worried about Harmonic Distortion of the 7th Order or the chopping of the sinewave damaging bearings in the motors of the hair dryers or blenders a motor genset will sort all this out.

    There is a lot of 60 Hz stuff out there that is widely used in the marine business so don't be afraid of it because it seems to originate in the US.

    Most of the planes you have flown probably did too since the first one in NZ.