Hybrid Propulsion - I Just Don't Get it

[Jd1]

Originally Posted by Tropic Cat

If you want to fantasize, look up Rossi e-cat in Google and consider how to couple this to a marine rated steam engine.

Cool ... er ... hot ..... I had not heard of this before and it looks like we will find out if it is real or not in the very near future.

[Tropic Cat]

Originally Posted by Jd1

I just have to add my 2 cents ........
Oh, if you know that you are going to be motoring 90% of the time then maybe the diesel electric system doesn't offer that much advantage but if you are sailing it has great potential IMHO.

You've missed the point. In the real world, boats have to maneuver under power. Do think you keep sails up in a 60 knot squall with the wind dead on your nose and a close leeward shore? Or that Catamarans sail into their marina slips? Or that 12 volt panels can heat water for showers. I could go on with possibly better examples, but I think I made my point.

I would submit that anyone who thinks these challenges can be overcome with a hybrid system hasn't spent enough time on or around boats, nor does he have enough sea miles.

Diesel electric would work fine, but there's no reason to have it on board when one lightning hit would disable the boat and you'd double the boat's propulsion costs by installing it.

[mbianka]

Originally Posted by twistedtree

Yup, you've got a good point on the whole flexibility of equipment layout.

But if you leave out solar and wind generated power, and just generate your power with the generator, if you burn a gallon of fuel to move the boat x distance, a direct drive system has to burn less than a gallon to move the boat the same distance and speed. That's where the whole physics and thermodynamics thing comes into play.

Also, the efficiency of a diesel is pretty constant across the operating range that you would use for propulsion - say 25% to 80% throttle.

Gas engines are different, with much better efficiency at higher power output, and much worse at lower power output. This is part of where a hybrid car makes gains by loading up the engine more than required for propulsion. You could argue that a gas engine is about the worst choice of engine for a car since most if the time it operates down in it's worst efficiency range, but that's a whole other discussion....

Another interesting point you make is about time-shifting when your engine is running. It's definitely an advantage to a hybrid system, but I think still comes at a cost of efficiency.

I converted to electric propulsion because I spent a whole season crunching my 6 foot 2 inch frame below the cockpit trying to get my diesel to start. Scratching my head at first and then paying diesel mechanics $75/hour to scratch their heads. I did not look at from a thermal efficiency stand point I just knew I did not want to put in another diesel in the boat if I could help it. I'm not sure a direct drive diesel will burn less even with the conversions from generator to motor. My Honda generator will run 5 1/2 hours on a little over a gallon of gas moving my 8 ton boat at 3 knots. Not sure if my my old Westerbeke could match that fuel consumption. When you think about it there is an awful lot of mechanics and parts involved in just removing the excess heat from a diesel engine. Pumps, thermostats, hoses, heat exchangers antifreeze. Those parts are all to remove the waste heat of a diesel. I and I'm sure others have had failures with some of them over the years. My Honda 2000 gas generator on the other hand has none of those parts to keep it cool. There is a fan inside that helps cool it but, that's all. I actually use the vented heat from the generator to help dry my swim towels and hand laundry too. But, the heat generated is nothing near what use to come off my diesel engine. I can put my hand on just about any part of my Honda generator when it is operating. Would not do that around my old diesel. But, I also find I run the generator a lot less than I ran my diesel too. Because I use to have to fire the diesel up before I dropped off the mooring to make sure it was running ok and it was the only way to provide power to move the boat in a crowded harbor. Most times I never turn on the generator to move the boat like getting out or returning back to my harbor. Hell lot's of the time I sail in and out and only use a little boost of electric propulsion if I get into trouble. With the diesel I would fire it up outside the harbor just to make sure it was operating if I needed it and did not want to be surprised if it did not fire up just when it needed it most. Even on trips down the 12 miles of the East River in New York I do not usually fire the generator up. If I had my diesel it would have had to be running the whole way. Things might be a little different with an installed diesel generator but, I'd probably still operate pretty much the same way. But, like I mentioned I see no need to have an installed diesel generator when a 47 pound Honda 2000 has been meeting my needs for the past four years and I'm not even maxing out it's power output either. To me it's just a simpler and more reliable system then when I had my diesel.

[twistedtree]

Originally Posted by Jd1

most reliable small diesel engines get between 30000 and up to 50000 hrs of life yet most boat engines do a major service at maybe 3000 hrs and I doubt that you will see many engines go to 5000 hrs before a re-power. This is the reason why I believe running the engine at low power and short duration is not healthy (besides what all the diesel mechanics will tell you).

Wow, that's a lot of hours to expect from a non-marine application. I own several pieces of diesel powered construction equipment and the rule of thumb in that type of application is 5,000-10,000hrs. I've never hear of anyone getting anything close to 30,000, let along 50,000. Another high volume application is trucking. 500,000 miles @ an average of 50 MPH would be 10,000 hrs on the engine. I've always heard that to be a typical life expectancy. 30,000 hrs would be 1.5 million miles on an engine before a rebuild, and 50,000 would be 2.5 million miles before a rebuild. I'm finding that hard to believe.

What application will run 30,000 - 50,000 hours before a rebuild?

By the way, I completely agree that it's bad to run an engine (any kind) for such a short duration or at such a light load that it doesn't come up to operating temp.

In the same way that a hybrid let's you time-shift when you run the diesel (or gas), it let's you concentrate/aggregate run time that might otherwise be fragmented. If you have a usage pattern that never allows your diesel to reach full temp because it's run time is so fragmented, then I can see how a hybrid could help aggregate those fragments into a single, longer run time. I know engines run less efficiently while warming up, but I don't know how much less. There might be a point where a series of short, cold runs has a greater loss of efficiency than the losses in a generator/motor, in which case the hybrid would be equal or more efficient, but only for that corner case of operation.

[twistedtree]

Originally Posted by mbianka

I converted to electric propulsion because I spent a whole season crunching my 6 foot 2 inch frame below the cockpit trying to get my diesel to start. Scratching my head at first and then paying diesel mechanics $75/hour to scratch their heads. I did not look at from a thermal efficiency stand point I just knew I did not want to put in another diesel in the boat if I could help it. I'm not sure a direct drive diesel will burn less even with the conversions from generator to motor. My Honda generator will run 5 1/2 hours on a little over a gallon of gas moving my 8 ton boat at 3 knots. Not sure if my my old Westerbeke could match that fuel consumption. When you think about it there is an awful lot of mechanics and parts involved in just removing the excess heat from a diesel engine. Pumps, thermostats, hoses, heat exchangers antifreeze. Those parts are all to remove the waste heat of a diesel. I and I'm sure others have had failures with some of them over the years. My Honda 2000 gas generator on the other hand has none of those parts to keep it cool. There is a fan inside that helps cool it but, that's all. I actually use the vented heat from the generator to help dry my swim towels and hand laundry too. But, the heat generated is nothing near what use to come off my diesel engine. I can put my hand on just about any part of my Honda generator when it is operating. Would not do that around my old diesel. But, I also find I run the generator a lot less than I ran my diesel too. Because I use to have to fire the diesel up before I dropped off the mooring to make sure it was running ok and it was the only way to provide power to move the boat in a crowded harbor. Most times I never turn on the generator to move the boat like getting out or returning back to my harbor. Hell lot's of the time I sail in and out and only use a little boost of electric propulsion if I get into trouble. With the diesel I would fire it up outside the harbor just to make sure it was operating if I needed it and did not want to be surprised if it did not fire up just when it needed it most. Even on trips down the 12 miles of the East River in New York I do not usually fire the generator up. If I had my diesel it would have had to be running the whole way. Things might be a little different with an installed diesel generator but, I'd probably still operate pretty much the same way. But, like I mentioned I see no need to have an installed diesel generator when a 47 pound Honda 2000 has been meeting my needs for the past four years and I'm not even maxing out it's power output either. To me it's just a simpler and more reliable system then when I had my diesel.

Hey, if it works for you, power to ya.

What got me going on this was really this notion that a hybrid system in a boat must be more efficient. After all, hybrid cars are more efficient, right? So a hybrid boat must be too, right? I see a few manufacturers riding on this falsity, and hate to see people taken in by it.

Several people, including yourself, have identified other benefits to hybrids. But efficiency isn't one of them - I just don't think it's possible given how boats work - and those other benefits come at the expense of efficiency.

[mbianka]

Originally Posted by twistedtree

Hey, if it works for you, power to ya.

What got me going on this was really this notion that a hybrid system in a boat must be more efficient. After all, hybrid cars are more efficient, right? So a hybrid boat must be too, right? I see a few manufacturers riding on this falsity, and hate to see people taken in by it.

Several people, including yourself, have identified other benefits to hybrids. But efficiency isn't one of them - I just don't think it's possible given how boats work - and those other benefits come at the expense of efficiency.

It absolutely works for me and I would never go back to diesel. I am certainly glad I made the switch. Your point about hybrid cars is a good one. Yeah they are efficent if you can take advange of the efficiency. I bought a new car a few years ago but, I did not consider buying a hybrid. Why? Because I traveled so little in my car less than three thousand miles a year and mostly local roads I would never be able to take advantage of the efficency considering my driving needs. Others who drive more highway miles it would make perfect sense.
But, I do think electric propulsion is a good match for many "sailboats" because of the way most boats use their engines as has been mentioned. Short hops into and out of harbors and docking is not the best way to use diesel engine as has been mentioned. Are there limitations with electric propulsion yes (battery storage) my boat is speced for a twenty mile range at four knots but, there are ways around those limitations. Such as using a generator to extend the range. Which is easy to and scalable to ones needs. Plus as technology improves in areas like battery storage etc... those improvements can be easily incorporated into an EP boat as they come along. I also take advantage of solar and wind power for charging and keeping the battery bank topped up. I have also been able to regen (turning the motor into a generator) while under sail to help charge the battery bank too. All these other methods of being able to charge up the battery bank help to decrease the need to fire up the generator. The less you fire up the generator the less fuel you'll use. The less fuel you use the less money comes out of your pocket. I'd say that all helps make it more efficent. Now I would never advise that a perfectly good diesel be pulled out of a boat to put in electric propulsion but, I have to smile when people say electric propulsion will not work. Because sailing for me has become much more enjoyable and involves less maintenance and expense since I made the switch.

[Dame.n.Jess]

Some times a Diesel/Electric combo is used for the instant torque that could only be achieved from Electric drive (or Steam). ie; Ice breakers use Electric coupled directly to the props so that should the prop become frozen in they can apply full torque from 0rpm. this is not possible if a diesel engine is connected to the prop (unless there is a clutch mechanism but even then its a bit dodgy, think dropping the clutch on your 5,000hp Diesel).

This may be a little off the topic in relation to small boat hybrids, but should you take your small yacht through the Northwest passage with a diesel electric system you will be able to spin your prop regardless as you watch the ice crush your boat when frozen over in a northern winter.


Personally I like the Diesel Electric setups for many of the same reasons Capt. Mike has already pointed out. in theory they are not as efficient but in practice they are more efficient (depending on your specific usage).

Regarding reducing the fraction in electric systems there are ways to improve this.

http://www.ecoboats.com.au/bellmann/submersible_pod.php

These two are 87-91% efficient. When combined with the increased efficiency of a smaller generator running at a more optimal power setting, these set-ups cant be two far off a stock direct drive diesel.

And as for cost we priced it as cheaper to go with an electric pod, 3.5kw diesel generator and 12 deep cycle batteries than buying a new diesel/g/box combo.

Plus with the pods outside the boat (tucked in tightly against the hull and well protected by the full keel) we now have a shower box where the diesel used to be. In our 28ft boat any additional space found feels like the council just added another 1/2 acre to your back yard.

Electrics can have more efficient props as well (ie large dia with more aggressive pitch turning at a much lower rpm, as the ability to apply 100% torque from 0rpm lends itself to spinning a big prop from startup. A diesel (or petrol) needs to start a prop from a speed where the engine is not every efficient. This means either a gearbox (which adds friction, wear, maintenance and heat) or a smaller prop (or both a small prop and gearbox). This is why they use diesel electric in locomotives the diesel just wouldn't be able to get the load moving as it needs to start at 800rpm, versus the electrics 0rpm.

I am certainly not saying electric are better than diesel, but nor am I saying diesel is better than electric. its comes back to the way you use your boat.

MANY weekend boaters could actually be better off by being electric, if they have zero intention of doing anything with there boats than motor off their slip to race round the cans then reverse back in, electric and batteries make a huge amount of sense here. it would be lighter and could be recharged over the week from shore power. Cheaper and almost zero maintenance compared to the norm.

Im assuming I will get flamed for being another idiot electric fan, but thats cool. if it isnt for the crew that take things up early nobody gets to experience the refined versions in later generations.

Happy boating (diesel or electric)

[cbax]

Take a look here
TWIN DISC - We put horsepower to work
and here:
bluEmission | Oceanomare Delphis Onlus
http://www.oceanomaredelphis.org/dru...luEmission.pdf

[pdf27]

If you're interested I'd recommend reading the HYMAR report - European Union funded report into the feasibility of a hybrid diesel-electric drive and what the value to it is.

For those who don't have time to read the whole thing, a good summary would be that a diesel-electric system doesn't save very much fuel, but that engine run hours are expensive and a lot of those get used at idle. Their conclusion is that a parallel system is the optimum for most small craft (so a lot of idling engine hours can be provided by the electric motor running on batteries, and consolidated into a few generator hours taken when the engine is running anyway), and interestingly marine diesel companies like Steyr and Yanmar have started offering that as an option recently.

The ability to use the propulsion system to generate what is really rather a lot of electricity for minimal extra weight/complexity is I think rather a major advantage for long-distance cruising, but given the current low level of reliability I think it'll be some time before that is exploited in any major way.

The issues so far have been fairly typical early-adopter ones. None of the technology involved is new, but it's being produced in small numbers and used in a new and hostile environment. That's always going to give major teething troubles.