Diesel/Electric Propulsion for Sailboats

About that cake, I have my hopes in the announced intentions of making the Vendeé Globe (alone around the world without stopping) a "clean" race. That means that for energy they can only get it from renewable energies, and they are going to live and race in the boat for a long, long time.

There was an interesting article about it by Antoine Sézérat, published some months ago in "Voiles et Voiliers” and for the 2008 edition of that race, Yann Eliès has announced that he is going to run with a completely "clean" boat.

http://sports.voila.fr/fr/cmc/voile/200615/elies-ma-raison-de-vivre_91620.html

Completely clean boats are not, at least for the next edition, a rule, but there are a lot of competitors that think that’s the way it should be.

Most suggest that the rule should be that all boats should include an identical integrated generator (in the hull) working with water displacement.
They say that, if well done, the drag would be very small, and everybody would be in an identical situation, regarding boat’s competitiveness….

I don’t want to lose a knot of speed (not even half a kn), but losing 0.1 or 0.2 of a knot, without vibrations to have clean and inexpensive energy…I am all for it

 

Brian Eiland is quite right in his assessment of the OSSA Powerlight system. I set out part of an email from OSSA to me dated 12th September.

"Our initial projects have performed considerably better than predicted, however, we feel that there is a history of exaggerated claims regarding diesel electric performance and we are going to be very conservative without solid data from very similar projects. Very generally, we are seeing that around 65 to 70 percent of the diesel horsepower gives an electric powered boat similar performance. This is primarily due to the ability to fit a more efficient prop than can be turned by the diesel without overloading the engine at low speed. However, to match top speed, it is more prudent to fit an engine and generator to match the diesel power.

In the case of the eLeopard, even though the motors are 35 hp, the 25 kW generator is only 33 hp, so each motor can only supply 16.5 hp at full output (assuming they are both throttled equally) In spite of this, the eLeopard does almost 8.5 knots under power, almost a full knot faster than the twin 30 hp Yanmar powered version. We don't know the full reason for such a good showing yet, but I wonder if the props were not well optimized for the Yanmars. It is a sail boat, after all.

Kind regards,

N. Bruce Nelson.

This is my second posting at this site, having recommended OSSA to Bertho in Thailand. I came to this site today having enjoyed Brian Eiland's article about his ideas on sail plans for cats. Very thought provoking.

As it is my intention to begin building an epoxy/ply composite motor yacht next year, I have been investigating propulsion systems. As the proposed vessel's design is full planing, I am considering twin water jet drives turned by two OSSA 400 hp electric motors. At full power they will require 600 kilowatts at 800vdc. Three 200 kilowatt generators for propulsion and one 50 kilowatt generator for everything else all controlled via NMEA 2000 should fit the bill.

The article entitled Sunbird 73 explains the concept extremely well. http://www.ossapowerlite.com/customers/custom_metal_yachts/snowbird.htm

Pericles

 

Jet Drives and Rim-Driven Props

Thanks for the compliment on the rig Pericles

Are you located in Thailand. I just got back from a months visit, mostly pleasure, but I did a tour of 4 boatbuilders there in the Chonburi, Pattaya, Rayong area during my final week for a potential client.

Per your waterjet/jetdrive reference you might have a look at a couple of these discussions:

Jet Drive subjects
http://boatdesign.net/forums/showthread.php?t=11254

Jet Drive vs Prop
http://www.yachtforums.com/forums/technical-discussion/4470-jet-drive-vs-prop.html

Rim-Driven Props
http://www.yachtforums.com/forums/technical-discussion/3961-rim-driven-propellers.html

 

Hello Brian,

No, not Thailand. I live in the UK, presently in London, but will be moving to Lydd on Sea soon. http://www.streetmap.co.uk/newmap.s...z=3&sv=lydd on sea&st=3&tl=Lydd-on-Sea, Kent [City/Town/Village]&searchp=newsearch.srf&mapp=newmap.srf

The area is called Romney Marsh and is situated at the SE corner of England. The prominent point is called Dungeness and gave its name to Dungeness, Washington and thus (probably) your version of edible crabs. http://en.wikipedia.org/wiki/Dungeness

It's a place, unique in so many ways with its own community. http://www.dungeness.org.uk/

Thank you for the links. I was going to notify you about JetPac! On 24th July I received an email from Michael Moses informing me they hope to have all the CE Marking certificates in place by end of August, so they can sell in the EU. He also included US prices, so it's possible we shall be seeing the 200 hp diesel over here for around £14,000. Any more and there could be a problem. http://www.billhigham.co.uk/billhighammarine.htm currently offers the 200 hp Optimax at £8,999 and diesel for recreational craft will no longer be available at commercially taxed rates. A jump from 35 pence to 95 pence per litre is in the pipeline, so why buy diesel boats?

Back to water jet drives. Both Hamilton and Ultradrive state that their pumps do not overload engines and you and I understand why that is so. http://www.ultradynamics.com/sections/news/passenger.asp

A number of vessels are fitted with 4 waterjets to match service requirements. Two smaller jets are used for stooging around and when the call comes, the two other power units come on line to drive at max knots. The reasons I am considering the use of OSSA electric motors to drive the waterjets are better weight distribution increased cabin volume within the vessel, greater economy, quietness and cutting edge style.

Pericles

 

Diesel electric

I think DE is the absolute future. I've been researching many aspects of DE systems as it pertains to the 50ft+ crowd and how various bleeding edge technologies (currently available) can be put together into a single system that would render DE systems that are twice as efficient as current offerings. The current plan (for ships 50ft+) is:

1. Get a 8 cylinder revetec engine converted to support diesel fuel. Supercharge it. This conversion is already underway (except for the supercharging, that one is on the house). The revetec engine is more than twice as mechanically efficient as a regular engine and offers insanely high torque (i.e. torque, not HP is what's important when it comes to driving electric generators).
2. Remove the poppet valves from the revetec engine and replace them with Coates spherical valves. This valve system is awesome and drains 90 to 95% less energy from an engine. It also requires no maintenance and is unlikely to even break down (compared to poppet valves). Also requires next to no lubrication and cooling.
3. At first, the use of a traditional electric generator will be required, but Siemens has started production of HTS (High Temperature Superconducting) generators. They currently offer a 4000 kV generator which would probably fit into 130ft+ ships. Obviously smaller HTS generators would be required for smaller ships. The efficiency of these generators is much greater than traditional generators at less than half the size and weight.
4. A set of capacitors would be used as a buffer between the electric drives and the electric generator. This is useful when it comes to constantly running the diesel engine at it's most efficient RPM (i.e. the sweet spot) when the prop RPM fluctuates.
5. Apart from requiring only a single engine to drive two props, a smaller secondary generator would be required as backup (can't just have ONE engine, what if it breaks down). Having a backup would allow the ship to limp to port if required.
6. I believe that using podded drives with the electrical motor INSIDE the hull of the ship (i.e. the pod is a glorified drive shaft) makes it easier to maintain and protect the electric engine. If the engine is inside the pod and something goes wrong, this means a trip to drydock is required. There would be one electric motor per pod (i.e. two pods). So if one electric engine breaks down, the ship can sail on using a single prop (i.e. sail to port if need be). The caveat is that this will increase vibration a little bit, but since the shaft is connected to a near zero vibration electric motor, then this should be very minimal indeed.
7. Using podded drives also means that no rudder is required. Beauty in simplicity. Podded drives offers the best possible maneoverability in all directions.
8. Any extra electric power generated would be used to power the ships electrical power system. So while cruising, the ship would only really need the main engine to be powered up. This greatly reduces noise levels as well as resonance vibrations that would occur between two main engines and the electric generator.

Since the engine and the actual props are not mechanically linked in any way, the engine can be placed/oriented pretty much anywhere on a boat. It can also be exceptionally well insonorized.

Oh did I forget to talk about the use of micro-bubble emitters on the hull in order to reduce water friction by up to 20%? Did I also mention that the revetec engine is much smaller than regular engines. All together, such a system using a retractable pod drive on a sailboat would be advantegeous.

What do you think about that? We think the entire system (including micro-bubble emmiters) will increase the cruising range of a vessel by almost 100% and reduce noice by up to 83%.

cheers,
GumbyTheBorg

 

Gumpy,

Thanks for the info on the Revetec. What a machine! I went to Wikipedia and that got me here.

http://home.iprimus.com.au/stevewest/feature/Piston Broker.html

At first sight, it looks as if the engine could ALSO work on steam power. Where are these machines in use?

Pericles

 

Go to www.revetec.com to check it out. I don't remember seeing anything about running on steam, so who knows... I just don't think it would be efficient. As I said before, the engine could be made even more efficient if the poppet valves were replaced by spherical valves from Coates. The engine is remarkably small compared to similar engines and it provides astounding torque. Make it into a supercharged diesel and you got yourself a kick *** engine that insanely efficient.

BTW, for those wondering, NO I am not affiliated with Revetec or Coates in anyway, shape or form. I just like really cool technology.

cheers,
GumbyTheBorg

 

Hello Gumby,

Apologies. I mispelled your name on my last post. I have been to Revetec site and I hope they get their finance sorted.
I also had a look at the Coates site.

As for now, the OSSA Powerlite system is the one I am going for, because it is available with NMEA 2000 and I shall be starting the build next year. Please keep in touch.

Pericles

 

JetPac has already got CE marking for their 150 and 200 HP diesel units. I think they already have a distributor in the UK, but I don't remember the name now.
I see this concept's possible market in professional boating, not recreational, as price is a major disadvantage there. At least in Spain.
(£14.000 is around 21.000 Euros. I would rather point to a price in the range of 23.000 Euros+VAT for one 200 HP unit)

 

"JetPac has already got CE marking for their 150 and 200 HP diesel units."

However they refuse to publish thrust/gph/rpm so the suitability of their units for any specific application are a Huge gamble.

These might be a great answer for a proposed " container shippable" cruiser ,but no way of doing any math.

FAST FRED

 

Yeap! They have to do something to improve their site and info offered on the system.

 

For powering via propellers, under is my own personnal understanding :

For a fixed pitch propeller, the power curve is nearly a cubic : If you want to turn x faster your propeller, you will need x * x more torque and hence x * x * x more power. You need 20 hp to turn your propeller at 500 rpm, you will need 160 hp to turn it at 1000 rpm. And at 1000 rpm, your engine will deliver 4 time the torque it delivered at 500 rpm. This is independant of the boat speed or anythinh else.

Said another way, if you run at 80% of the max RPM reacheable of your engine, you will need only 64% of the max rpm torque, and will use about 51% of the power used at max RPM.

That why propeller are sized for full speed full throttle. Once this point is met, all is OK. On most engines, rpm for maximum torque is lower than max rpm, and maximum torque is bigger than torque at max rpm.

So the story of better flatter, or anything else torque curve for electric engines are irrelevant.

What can really affect power is the way and condition it is measured. Power for pleasure craft engine quoted are frequently intermittent power, at flywheel. You have to take continuous shaft power if you want to compare to electric. Another point are accessories. I do not know how sea water pump for cooling, mechanical bilge pump or alternator power are taken for power figures. A 100A alternator steals around 4 hp from your engine. I do not think you put an alternator on an electric engine nor PTO.

The S4L2 industrial engine is quoted as 37 hp intermittent by mitshubishi http://www.diamonddiesels.co.uk/DOWNLOADS/s4ldd.pdf , 32.3 hp when used in a genset ( http://www.sdmo.com/files/pdf/FR/T27HK.pdf ), and 42 hp when marinized by westerbeke 44B http://www.westerbeke.com/brochures/DSLENG, 44B Four (Jan 06).pdf , sole M44 or vetus M4.17. All this at the same maximum 3000 rpm for all engines. I think all this come from what accessories are taken (alternator, sea water, cooling fan, exhaust back pressure etc ...), where the power is taken, and how long you expect this power. Between 32 and 42 there is nearly 25% variation.


Now, for this 42 hp diesel engine, an electric engine 32 hp (24 Kw), may be a match. But anything lower is not true.
Either they do not have true same performance. Near hull speed, the last half knot is ultra expensive (around 30% more power for 5% more speed). One engine is 7.7 kts, the other is 8.2 and both are rounded to 8 by the marketing dept. Or one propeller/gearbox is mismatched. And nobody cares of it because overall performances are still considered acceptable, and nobody will recover engeenering costs.

 

Hum, I can't remember and I have no time to look (too much work), but I know that they had said to me (the engineers from Panda) that the difference in efficiency is greater than what you say. I am almost sure it has to do with torque.
I know that the answer is on one of the Panda sites that I have posted in this thread.

Another difference between an electric and a diesel engine is that in an electric engine, the max speed is practically the cruising speed. In the case of the Lagoon 42, if I remember correctly, the cruising speed is 8.5k. It would be impossible, if you only consider the conversion of kW in HP.

Fcfc, if I have learned something on this forum about engines, is that the engineers that adapt the right power to a boat, or the several engine possibilities, know what they are doing. You can be pretty sure that the Lagoon 42 motorization is all right and I will bet that the cruising speed is not very different than the one you got with the two 40hp diesel engines.

When I have time I will take a better look at it. I have several tests of the Diesel-electric Lagoon 42 and I will see what they say about power and cruising speed.

 

Interesting to check up on Revetec again.... in the few months since I last looked them up, they've made incredible progress with that thing. I'm going to take some time later to go over the engineering in more detail, but I can readily see why the thing is getting so much coverage, it is a very, very promising concept. The fact that they can maintain this pace of development while losing as little cash as they are is pretty good indeed.

 

Revetec gets Australian Federal Government Commercial Ready Grant

Matt,

Thanks for the timely reminder about Revetec. http://www.revetec.com/?q=latest-news

The X4 aero engine is astonishing, so incredibly compact, but imagine it fitted into a motorbike? There are plans to develop diesel versions and those would revolutionize recreational boating. I shall buy shares if and when they are available.

Pericles