Am I crazy- Fire Suit ON!

StianX,

The Ossa system works by automatically switching generators on or switching off in programmed sequence, according to propulsion requirements. Hence the economy. The Ossa generators are unlike any others you may have experience with.

However, to throw another hat into the ring, how about Yellowfin? http://www.yellowfin.com/pr_shipnboat.pdf

According to their site, they would be interested in working on a large boat build. http://www.yellowfin.com/VSDTechnology.asp

Check out their videos. Usual disclaimer, for now.

Pericles

 

That is how all modern diesel electric system works. Often has some locking function preventing generators shuting down if the ship is in a operating mode where mutch power could sudenly be neaded. Or can be locked by the crew if they know they will nead more power soon. In that case Ossa is nothing new, but defently still a interesting product for smal vesels.

 

Hi Stian,

I agree in principal with you 100% but our world is changing by leaps and bounds. From what I gather they use small automotive size engines to drive the dynamo. A Mercedes, BMW or VW-Audi common rail engine is very efficient and they have high power per liter. The whole gen set weights less than a medium duty engine like a small Deere, Cummins or Yanmar.

As far a bow thrusters; yes that is part of the plan as is a stern thruster. My first mate is all of 105 pounds and I am not ready to see how she does against a 40 ton boat!! Ossa lists a bow thruster and it is most likely $$ I have not herd back from them so I can't say what they are indeed using. My best guess the VW TDI for the smaller gen set and Audi TDI for the bigger ones?

Regarding using more or less generators, having six gives you more flexibility in power. I can't say that throttling a electronic engine is a bad idea. Optimizing engine speed and load is a way to save fuel. I think we are seeing a paradigm shift in what we all knew to be true with electronic engine controls. I remember when starting a turbo jet engine was a major event, now you push a button and everything is automated and monitored so a child can do it. I remember when Flight Engineers used to change "Jugs" cylinders on airplanes as part of the normal routine.

We have seen remarkable changes in durability and reliability of engines, electronics. We take for granted that a car will last 250-300 thousand miles today, turbine engines run with no fixed overhaul time and diesels are lasting twice or longer than they did just a few short years ago. Where I am going with this is I don't we can rule out car base engines as being up to the task given the right kind of load imposed and a generator is a good model.

Steve

 

Pericles,

That Yellowfin drive is amazing. Add that to the back of a couple of electric motors and away you go. The numbers they show are eye raising.

Steve

 

I looked a litle closser to Ossa and it don't seam there data is corect.
There data:
Caterpillar
3406C Generator 200kw 6cyl turbo N/R 311.4volume (8.82)
excl. sound shield 6,374 (2,897) weight

Caterpillar:
260 ekW (325 kV•A) at 1800 rpm 60 Hz
320 ekW (400 kV•A) at 1800 rpm 60 Hz
215 ekW (269 kV•A) at 1500 rpm 50 Hz
245 ekW (306 kV•A) at 1500 rpm 50 Hz

2409-2591 kg (5300-5700 lb)

Not only are there numbers a litle wrong they are allso comparing to a engine with a cylinder volume off 14.6 L (893 cu in) and this engine is welded solid on a frame. It's like comparing a Rolls royce and a Lotus.

Dair is making a diesel producing a 100hp and weigh below 100kg.
The Steyr is also a ligther engine.

I looked trough the caterpillar web pages and it seam like they got lighter engines with same output, seam like Ossa tryed to find the worst case.

They also don't supply informatio on there web page about the fuel consumption g/kW and I gues the reason is that they did not test it or they know it's not bether than the oposition. No system is perfect.

I would demand to see some data on g/kW and I would put in some serious efort to find out how mutch you could get the weight down on a diesel. Aluminium gearbox, use the diesel with the highest weight to power ration.

Then find out how many m off cable you nead to power your electric engines.
This pluss the extra fuel I defently think this smaler and numberious engines nead. and the weigh off the boat will be about the same.

You seam to be quite shure you want to go for diesel electric so I would advise you to reduce the speed and go for a displasement hull.

 

3xOssa 200kW + 1xOssa 800hp motor=2741kg

1xCat 3406E 800bhp + ZF 500 gear=1359kg

The cat with gear option weight 1382kg less and now cabling distubution and controls is not included.

I also gues the coupling betwen engine and gearbox is a few kg and I also gues I have calculated the engine and gerboxs dry weight, but I don't think lube oil, colingwater and a coupling will weight more then 1tonn.

 

Hi Stian,

I do like a number of aspects of DE but I am not married to the concept. The idea of using power modules is not new as you know. On a boat this size combining ships power with the prime movers makes sense from a reliability and space consideration as well as being able to take a prime mover off line with out much loss fuss. Taking the diesel prime as an example even with an aluminum gear box you are at or near the weight of DE system and you will have to add a ships power generator and what ever redundant system on to that. The Yellowfin system sounds good on paper too and with their claim, you could say go from a 1200-1500 engine to perhaps a 1000 HP. A cat C18 weights 2000 pounds less than a 3114 or C32.

The C18 is an option I thought about in addition to the DE system, 2000 installed hp is more than enough to push the size and weight. I can load the engines up with dual 300 amp 24 alternators and run everything off inverters. The big question is still are two diesels producing say 400 hp each burning more fuel than a DE system at the same power to the props? I am not sold on the idea of DE until somebody can prove to me that an apples to apples test shows the facts. We all agree that a modern diesel burns so much fuel per horsepower hour in direct drive. I want to know that turning diesel fuel into electrons is more efficient in this application. I know it works for trains and larger boats so have to think it should work but that may not be the case or it could be great in one segment and be far worse everywhere else.

I have been touting the merits of this with out any first hand data so all my optimism is theoretical at this point. Again I think it has a good chance of being most of what it claims but I can't say. Regarding using bad examples in comparison, I think every one does this, it is marketing 101.

I have asked for the data you questioned and, a lot more I will relate it as soon as I get it.

Steve

 

Stian,

A 3406E or C15 with gear option? Is that the PTO/PTI, what do the other parts weigh in at and how much space do they require? Even the bigger 18L cat engines are lighter than the DE system by almost 1000KG per side.

Steve

 

The gearbox I used in my litle comparison have PTO(live and clutch) as option. Engine can be clutched in and out with a 12VDC or 24VDC clutch.

And I think as long as you want a planing hull you should concider the weight. 1000Kg extra is something you don't want when you are going to rife on top off the water.

Converting Diesel to electric energy cost a litle, you have loss in cables and you also loss 1,5% when its converted back to mecanical movement in the electric engine so I gues you lose 3-4% in the electric system and this together with the added weigh off 1000kg make me lose belife in anny fuel savings on this kind off boat. 1000kg extra would not be sutch a problem in a displasement hull.

If you runn one large diesel on low load it will result in that the turbo won't charge proper and fuel cunsumption/kW will increase and you will get more carbon resedues in the engine.

 

I have to creditt ossa for one thing, there propulsion motors are really light, not even the aluminium AC motors from abb can beat the ossa's DC motors.

Normaly AC is mutch ligheter than DC motors. There must be someone making AC engines that are even ligther, but I can't find them.

 

Steve,
You seem hooked on diesel-electric, and I tend to agree that it's the way to go for what you want.
For the size and weight range you're looking at, I would target a comfortable cruise speed in displacement mode of 10-11 knots. Your 20-knot top end, though, is somewhat too slow for a hull of that size and weight to be fully on plane, at least not without a ridiculously wide planing surface (which brings with it an uncomfortable ride and poor low-speed efficiency). Are you absolutely sure semi-displacement is out? Because a 70-foot waterline at 20 knots is operating at a speed/length ratio of 2.4, generally considered semidisplacement territory, while you'd probably not get something that size on full plane until at least to 25-30 knots. The Downeast fishing/lobster boats whose style you mentioned as an inspiration are largely semidisplacement hulls.
Now as to the DE drivetrain. You're essentially going to have two modes here. Cruising at 10 knots or flying at 20. If you optimize the hull for those speeds, then anything in the 15 kt range will be uncomfortable and inefficient. So I'd optimize the DE powertrain accordingly. Might I suggest American Superconductor's lightweight ship generators and motors, http://www.amsuper.com/products/motorsGenerators/index.cfm as a starting point. I'd use a single continuous-rated diesel generator optimized for low speed cruise, and fire up a second, larger, higher-rated diesel to get the extra power for your fast dashes.
OSSA's system is really optimized for smaller, lighter craft than yours, operating in a fast displacement condition. I think you'd be better off in terms of cost and fuel consumption to go with one engine optimized for low speed, and one that's added at high speed.