Diesel/Electric Propulsion for Sailboats

Vega,

Earlier than WW2 P & O had the Strath sisters. http://www.ozhoo.net.au/~strathsisters/strathaird/index.htm

I returned to the UK in summer 1953 from Australia, having lived in NZ since 1949.

Pericles

 

"Your nation developed diesel/electric locomotives very successfully."

The PURPOSE of the diesel electric units was to create a method of STARTING a 2 mile long string of RR cars.

Steam makes max torque at 0 rpm and was IDEAL for RR service, but considered passe.

Yes, the new units will engage a number of engines , as the terrain requires , just as the Passenger boats fire off extra gen sets to accept hotel or propulsion loads.

Weather electric gains anything over a PROPERLY sized diesel is yet to be shown.

I believe hull design and light weight will do far more for fuel mileage today, than electric conversions .

In a 1/4 of a century , IF "room temp" superconducting motors are in the auto scrap yard , there might be an advantage to electric drive boats . But the battery's , and charging goodies will need their efficiency moved one or two decimal places too.

FF

 

After the Lagoon 420, now it is the Moorings 430 that turn to Diesel-electric propulsion.

I guess that, like Beneteau, these Guys are very confident on what they are doing and about the reliability of the system. As everybody knows, the Moorings are charter boats with a heavy and casual use.

The Mooring 430 is a modified Robertson and Caine and the diesel-electric technology is from Glacier Bay.

They plan to extend this type of motorization to the bigger cats.

"The Moorings is proud to lead the way in testing and improving this technology to the point where such an eco-friendly propulsion system is available to the recreational boater and charter customer," commented Lex Raas, President of The Moorings.


The Moorings has been testing this technology for over a year and has brought to the market the first system to be proven in operation in a marine environment. The system is unique in that it does not utilize additional batteries for energy storage but instead combines a custom generator and propulsion unit, making it very environmentally friendly. The OSSA Powerlite propulsion units are driven by an OSSA Powerlite DC generator system by Glacier Bay, which also powers the boat systems, including powerful DC air conditioning units. No additional battery bank is required for propulsion storage, which avoids issues with battery life and disposal, and the addition of weight and reduction of usable space.
This yacht will be on display for the first time in the United States at the Strictly Sail Miami boat show, February 15-19, 2007, booth C39. This unique yacht is currently available for charter with The Moorings charter fleet in the British Virgin Islands and will be available for purchase in The Moorings Advantage Yacht Ownership Program in 2008.

http://www.investors.com/breakingnews.asp?journalid=49463576

http://www.forbes.com/businesswire/feeds/businesswire/2007/02/15/businesswire20070215006173r1.html

On the “Cruisers Forum” they are running an interesting thread about: “Electric and Diesel comparison” and as there are some folks that have diesel-electrics on their boats, it is an informed one.

http://www.cruisersforum.com/forums/f48/electric-and-diesel-comparison-6450-3.html

 

Fred
You are making the assumption that the motor will be run from a set of batteries. I agree that if you count the losses from a charger and a set of batteries efficiency is dismal and added weight is unacceptable. If however the motor is run directly from a variable speed generator it’s a different story. i.e. the batteries are only used for hotel load as they are now. The permanent magnet dc motors/generators efficiency if sized and powered correctly can be 90%+ (some claiming to be over 98%) and the controller at around 95%. This is without having to suspending them in liquid nitrogen

I saw a claim that over ocean swells the reduced load can reduce the generator speed thereby saving fuel I think the claim was 10% on average but haven’t seen any comprehensive independent tests to confirm this. In fact none of these DE players seem to publish comprehensive independent tests under realistic conditions which is suspicious in my book.
As for the regenerative capabilities I’m working on the numbers to figure out if this is at all feasible with or without a controllable pitch prop. Yes I know dragging a prop slows the boat down but if you have sufficient wind and are pushing up against hull speed anyway it won’t make much difference. Light wind is of course a different story but then you can simply feather the CPP. The only reason I’m considering this is because I have a bit of a special case a center cockpit catamaran with a sail drive leg that can lift out of the water if desired.

There seems to be some validity their claims of fuel savings if compared to run of the mill yacht engine.
If this can be used to charge the house bank under sail it’s a small advantage but is most probably outweighed by the cost and complexity of a CPP.
Maintenance is where I can see a real advantage. I know there are a number of unfamiliar parts to this but electronics if built well should outlive the boat.
For the bigger players with fleets the componentized nature of this system provides significant advantages in logistics but we aren’t talking about them.

As for costs, there are only a few boutique players in this market at the moment so they charge what they will. You could build your own system for probably a 3rd of the price of the Solomon system using electric car parts.

 

Single Engine Drive on Catamaran

Do you presently have this vessel, or contemplating such?? I've written a few words on this idea before, so I would be interested in tracking such installations:

If I were looking to use my auxiliary engine in a strictly aux manner, rather than in a motor/sailing demand, I would seriously consider a single engine installation. This engine would be conveniently mounted in an enclosure on the cockpit deck and would belt drive a steerable out-drive leg that would be incorporated into the rear portion of the central nacelle structure. Maybe this rear nacelle might appear as on "Earthling's pod" (attached photo and/or www.earthling.co.nz/boating.htm). This saves the cost and weight of the second engine, trans, shafting, prop, etc, and opens up the rears of the hullsfor a nice master bath, or whatever.

 

Brian,

The Yellowfin system http://www.yellowfin.com/media_coverage.asp offers two VSD propellers driven by one motor. This Variable Surface Drive has a full blade feathering facility. If the single motor could be DC electric and a complete assembly itted into each hull, far less space would be used and two baths might be fitted.

The http://www.ossapowerlite.com/products/generators/generators.htm generators are much more compact than conventional AC units.

For amusement, would large flippers be of any use? http://www.hobiecat.com/kayaking/models_mirage.html

Pericles

 

Brian

Wow, now that is a catamaran!
Mine is a considerably more modest beast but yes it’s an existing cat, quite an old girl. The installation I’m contemplating, been researching this for a number of months, is a Sillette sail drive leg that can be raised from the cockpit either manually or electrically to two different heights. 1. For beaching or shallow water to bring it above the draft. The prop for an electric installation would be larger than a standard installation so when motoring should be nice and deep, no cavitation plate in this case. 2. And the second level to bring it out of the water entirely. This is difficult to do with a diesel engine attached but with an electric motor it is more practical.
For power I’ve been looking at the LEM-200 motors with the new controller they have coming can be run at 92vdc 16Kw continuous. These motors seem to be limited by the available controllers currently 72vdc. I was looking at a few variable speed DC generators, but these are pricey, so I may build my own using a decent generator controller for polar for example. For raising I’m looking at something like the lenco hatch lifts. The tricky parts are working out what reduction ratio to use, weather regen is worth it and designing a circuit board to automate most of the functions.

It’s a great idea in theory, being able to have only one engine and to raise the prop out of the water in light air but weather this is practical is yet to be proven.

The alternatives as you mentioned seem wasteful. i.e. Hydraulics or twin engines.
I’ll let you know how it goes but I have quite a bit of research still left to do before the project starts. I should start in a few months.

 

This is indeed a very interesting topic. It would seem to me that normal use case for sail boats has been forgotten. It would seem likely for me that traditional properly designed diesel would give as good as or equal fuel efficiency than DE.

But if I look my own sailing, most of the time I run the engine while in harbor (speed limit often 3kts) or in purpose of recharging batteries, cooling fridge or using windlass. How is the efficiency on that case (95% of the time)? It would seem logical that generator (AC or DC) would outperform diesel engine on that case.

Even when motoring, and usually that means calm conditions, I do not remember ever running diesel on high revs in order to get full hull speed. I usually opt for 70% of hull speed and 50% less noise. So for me DE would seem better option if I can get better fuel economy on those cases (and better yet quieter operation). In a 34ft boat space is not easily available for dedicated generator so that is also a strong argument.

It would be interesting to see objective numbers or plots of how well diesel engine transforms energy stored in the fuel to kinetic energy trough propeller. And compare that to generator turning fuel into electric energy and from there kinetic energy through motor and propeller. I am not expert, but that kind of experiment shouldn't be too difficult arrange in a tank or other controlled environment. Plot where Newton meters are in x axis and consumed fuel in y axis should give good comparison.

 

Keep in mind the very significant thrust force generated by the prop, and the lever arm of this force depending on the length of your outdrive.

You are also driving the diesel torque thru 90 degree gears, so those gears must be very strong and close toleranced

For these reasons I prefer to consider a belt drive to avoid the 90 degree gears, and then the potential to rotate the drive leg about its engine driven sprocket, out of the water.

You might consider that Sillette had a number of problems in the past with there 'reverse lockdown'

 

The big difference

It seems we shall all need more empirical information on the efficiency issue. Meanwhile, I’d like to keep focus on the chief purpose(s) of engines on a cruising, sailing yacht, and to me that seems to be self-reliance. A system such as that in the Lagoon 420 and 440 can recharge your propulsion system. This is not a percentage difference from diesel power, it is an absolute divide that cannot be bridged. I have been in more than one situation where diesel theatened to run out, bringing down not only my propulsion but my onboard navigation systems as well. I would pay a great deal to eliminate that possibility.

For a cruiser, it seems to me also a little off the mark to be concerned with maximum hull speed under power and similar issues. Sure, sailors motor more than they care to admit, but we still insist on sailpower being our main system. To defend that, we have clung to all sorts of solutions to minimise electrical power consumption, an Achilles heel of unassisted sailpower.

DE systems go a long way towards solving these dilemmas. I would compare them to the desalination plants. They too have their problems, they are if anything far more troublesome to maintain, but the prize – the prize is a form of self-reliance no other system can provide. To me, that matters.

I agree with some of you that answers to efficiency and speed will ultimately be found in build weights, sail systems and hull shapes. If we can merge that trend with the move to DE and also DC gensystems onboard, it points to more lightfooted vessels with less engine power and very little reliance on shore supply. In short, a crusing sailor’s dream.

 

Berserk,

On page 82 0f the latest edition of PBO you will find Nigel Calder's assessment of
Diesel Electric economics.

http://www.proboat-digital.com/proboat/20070809/

Regards,

Pericles

 

Thank you, Pericles. Calder's analysis is indeed thorough. I still want to point out that his comparison is power-to-power, i.e. strictly for non-sailing vessels. I look forward to his next instalment; at the end he foreshadows an article on the "other" advantages/efficiencies of DE.
Some of the variables for a sailing craft may be elusive and very hard to get a universal measure on. Many of us deploy "power-assisted" sailing quite often, i.e. motoring with a headsail or main during light wind or at unfavourable angles of attack. This would be a typical example of a diesel running at less than full throttle. In heavy seas we may add sail to steady the boat.
Another moving target is the "hotel" load. Consumption of electrical power in small yachts has crept up steadily since the 60's; bringing the cutover point for DE economics to ever smaller boats. But this too introduces design dilemmas: at least on non-US yachts, adding a genset is rarely favoured on yachts below 40ft, primarily for lack of space. We tend to go for ever larger "dynamos" on the main engine instead, not altogether kind to shafts and bearings, and leaving us with the dilemma of running the main engine in harbour just to keep up supply.
A factor that ought not to be swept under the carpet is the inefficiency of running multiple sources of supply. My boat has a remarkable number of diodes and circuit breakers and transformers and converters to deal with shore power, a windmill, solar and the main engine. Only recently we added diodes to compensate for voltage differentials between the windmill and the engine dynamo causing battery overcharging and voltage being pushed around the windmill circuit. Our main inverter is a power consumer of considerable concern. The more I could consolidate our system to "pure" DC, the less hardware and losses all around. Sadly, the combination of DC and DE has not been fully deployed in some of the test systems around, but I am sure this is the future.

 

Retractable Prop & Drive

Here is another unusual one,...not quite as 'Galactic' as Earthling

How about the retractable rim-driven prop unit I utilize here?..driven by DE

http://www.runningtideyachts.com/dynarig/...scroll down

 

Really interesting topic indeed, although not very familiar with both yachting wolrd and engineering-propulsion issues.
I would like to ask some questions here.

It appears that individual companies manufacture electric generators (like Fischer Panda) to be combined with conventional diesel engines. I wonder if there is a marine engine manufacturer (like Volvo, CAT etc.) producing a whole system of DE propulsion system. Are there any issues of incompatibility?

Also, electric generators (in order to make a hybrid engine) is it possible to be combined with diesel engines ranging from 10bhp until 2000+ bhp? Hybrid propulsion is suitable only for relatively small boats or even mega-yachts?

Thanks a lot for any information you can provide

 

Hi alexandros, just briefly: To your last question: Indeed, very large commercial ships use hybrid power extensively, way ahead of the small craft; even the slightest fuel saving there amounts to $$$ per day.
For small craft I am only aware of the Panda and one US system, both used in experimental catamarans - see e.g. the Lagoon site. Bavaria is also experimenting. As far as I know, none of the major engine manufacturers have announced a complete hybrid system.