diesel/electric hybrid

[sandy daugherty]

Calder has further information on his plans in Sail Magazine, June 2008, pg 74. I oversimplify, but he is using two propulsion systems for comparison, a conventional deisel/transmission to shaft driven prop, vs hybrid d/e. The bulk of the article addresses one of the deisel generator inefficiencies concerning battery charge acceptance rates. And it seems to me that we are getting close to being able to say that hybrid d/e has a place in small cruisers.

I, otoh, will still be putputting into an anchorage on my 8hp man-portable yamahas, trailing a cloud of 'eau de city bus' because I'm running my 700# generator to use the anchor windlass. The overwhelming factor in my calculations is "its paid for."

[Alan Wheeler]

Having a diesel electric system with or without batteries can be more efficient than having straight diesels,

Either I am not understanding your comment and the other many similar comments you and others have made (and that is quite possible) or this concept is not being fully understood by others. Can you describe why a Motor/Gen without batteries (in other words serves no other function than just propulsion) is more efficient than and engine/gear box coupled to a shaft.
I can understand advantages in the system when you have a lot of batteries and major power generation and for large vessels that have big gennies running long periods, this would be a good scenario.

just ad a hydrogen generator and a watermaker could be the ultimate answer.

Now see, this is a similar theme. 1: hydrogen generation is waaay to inefficient. It has huge losses. 2: making water to takes energy, turning it into hydrogen takes energy and that all has to come from a generator that takes energy. It would take 90%(just a figure of speach) of your energy production to provide 10% of your propulsion needs.

Now don't take any of the above the wrong way. I am not intending any thing other than just interesting discussion about this. If there is just one person on the face of this earth that wants to see better and more efficient forms of energy production, it's me. Maybe that is why I am questioning these comments so much. I really do want to find better solutions.

[sandy daugherty]

I apologize in advance for another long-winded observation. Feel free to skip to the last few paragraphs.
Let’s limit the discussion to the propulsion needs of a cruising sailor. While we would prefer to be sailing all the time, we need engines. Light, easily driven vessels need engines for a smaller part of the time. Heavier vessels need bigger engines. We want them to be safe and reliable. We want to be able to fix them ourselves when they break down.
For the most part, the state of the art in sailboat mechanical propulsion to meet these needs is a relatively small diesel engine, turning a fixed pitch prop thru a transmission that may reduce the engine's preferred rpm to the prop's. It also lets us move in reverse, or just slow down a little faster. We don't prefer gasoline engines even though they produce more power per pound, because we would have to carry more gasoline which is also more dangerous. This is not a perfect solution; if we consider the total cost of having and using that propulsion over a long period of time, it comes out to a figure that seems very expensive. So we look for little economies.
The most efficient boat propeller has a large diameter, narrow blades, and turns slowly, say 300 rpm. The most efficient speed for the engine is perhaps 2100 rpm. A great deal of engineering has gone into developing the most efficient way to reduce 2100 rpm to 300 rpm, but the general rule is to keep the number of gear sets to a minimum, as in one pinion and one driven gear. That takes up too much room in a place without much room. Multiple sets of gears take up less room but the extra shafts, bearings, and shift mechanisms add up to less efficiency. But we were happy with that for years. We have engines powerful enough to turn the transmission, shaft and propeller for years at a time. All is good.
Science, bored with diesel engines, marched on. Research to develop more efficient electric motors plunged ahead. Almost everything people spend a small pocketful of money on has an electric motor in it. Even a can opener! Incredible improvements have been made, now there are reliable electric motors in hard drives the size of your thumbnail. Small incremental improvements here and there compounded themselves, and now we are faced with a source of rotational force that seems to be a better way to deliver energy. It’s smaller, less complicated, cooler, and so on. That's what they say.
The next problem was to find a source of electricity. Along come single-rail diesel generators, where the generator is built to match the best torque speed of the engine. Just like above you say. Yes. But there is a difference. Electricity can be stored. So you make electricity at the absolute tweeky best conditions and store it. Turn the generator off. When you need more, turn it back on. You don't run it at idle to keep you speed down to the posted limit. You don't start it and run at half throttle to make popcorn in the microwave, or pull the anchor up with the windlass or to run the air-conditioning and watch a movie on your widescreen projector.
Now the numbers are getting close. It appears you can get the same return on life-time investment by replacing that transmission with a generator and a cable and a controller and a cable and a battery and a cable and a motor. So what?
The batteries are the next stumbling block. They weigh a ton. Or two. They have nasty habits, and you can't just pour a lot of electricity into them. You have to pour the last third of all that power at a trickle, which means the generator isn't working hard enough to be efficient. You can only use half of the power the batteries have so you have twice as much weight as you need.
Enter the final key: batteries that can rapidly discharge their power, and can rapidly be recharged, matching the best way to use the diesel engine running the generator. Now your battery bank weighs less. Less weight, less power required, less fuel burned, go further pay less. Make less greenhouse gas.
The point is that these economies work only incrementally, and in combination, and only really show on the bottom line when amortized over a long interval, taking in many more considerations than the MSRP of the equipment.
You may ask why we couldn't just skip this huge loop and bolt that efficient single rail diesel generator to your trusty old transmission. That’s a good question. I think (because I don't really know) that by being optimized for a certain operating range that it becomes much less friendly at any other set of demands. It would be less efficient then what we have without spending another dime. Not a big market for that.

As far as your question about a d/e system without a battery bank, I think the answer is less clear, that there is little more than an incremental economy, that may not stand as much if the issue were limited to the cost of replacement and operating costs alone.

[Brent Swain]

This leaves you with the tough decision., how much diesel to carry and how much batteries?

[Alan Wheeler]

I am really sorry, but your post really looks like the wording from a Glossy Brochure.

The most efficient boat propeller has a large diameter, narrow blades, and turns slowly, say 300 rpm.

I think that is one hole in your theory for a start. 300 RPM maybe fine for large ship propellors, but we are not working with large ships. There are to many constraints to boat design that determine what propellor is best suited rather than engine. For a start, if you are going to spin a prop at only 300 RPM, have you considered the pitch required to get your boat to say 7kts. That's about 31.5" of pitch. That would not be a very efficient propellor at a diameter of say 17" through to say 27" which would mostly be what is represented by most of our members.

You don't run it at idle to keep you speed down to the posted limit

I am not sure what you are trying to say here, but do you assume that the Diesel is using the same amount of fuel at slow RPM as it is at high RPM? You see, this is the one major advantage of a Diesel over a petrol engine. The Diesel is using a set dose of fuel with each revolution of the engine. The faster it reves, the more fuel is consumed. The slower it revs, the less fuel it consumes. A Diesel does not magically use less fuel at a certain high RPM. True, engines, both Diesel and Petrol, have a "best efficiency" area of operation and that tends to be at around 75-95% of their maximum RPM. But that is not corresponding to fuel efficiency. It is a combination of all operating parameters of the engines performance and has a lot to do with heat. It is actually quite complex, but in a nutshell, it is about the maximum heat the engine generates as it creates the power and how that heat equates to power. It's kind like a point of max power output vs the engine not going into over heat. Depending on engine manufacturer and how they use the specs, it can be considered the Max continuous RPM point of most engines.

Now the numbers are getting close.

To what?? I am not getting your point.
A genset runs at full RPM for one single reason. Frequency. And the really good gensets tend to run at 1500RPM. That is to keep noise down. The cheapies tend to run at 3000RPM. That doesn't make the cheapies any more economical than the 1500RPM ones, in fact quite the opposite. Yet you would propose that running the genset at 3000RPM would make it more efficient. If you think a genset works at full RPM for efficiency, then the you have yet to be introduced to the "inverter genset". This idles if that is all the power requirement needed and revs up to match the the load. Ask anyone that has one. They will inform you how cheap to run they are.

Now your battery bank weighs less. Less weight, less power required,

Sorry, did I miss the release of a new Battery design?? I thought that was still in development and is still only found in a few experimental electric cars.
I am sorry, I am not attacking you, please don't take it that way. But you seem to have a lot of words that mean very little after reading it all. It really does sound like you have just printed an advertising brochure that has a lot of colourful description but no susbstance.

[fastcat435]

Hallo Alan to come back to your last remark on batteries first , we have been using lithium Ion batteries for 2 years now and are very happy with these units the only part we do not like is the price , around 1000 euro per 100 amps usable or 1300 watt or a factor 5 compared with agm units

Our motors run of DC power and the generator(s) supply dc energy so they operate on variable rpm settings to make them as efficient as possible ( anywhere between 2600 and 3400 rpm )
We have chosen for high rpm setting to save on weight since low rpm generators weight a lot more
In our case we always use batteries for propulsion so at least we can store generated electricity and be more efficient.

Prop RPM on the Green Motion system is between 0 and 1200 RPM max and this creates a better efficiency than the usual 900 to 1800 RPM on diesel motors.

Hydrogen is not very efficient to make and it will cost speed to generate the electricity needed to both make water and from the water the hydrogen but if one is not in a hurry why not ?
So we will cruise at an average speed of 8 knots in stead of 10 if we can save on fossil fuels and sail clean it should be worth it is my feeling
In mean while we are already saving a lot of fuel by not using the generator or diesel when entering or leaving a harbor , the only time we start the generator is if we are in a hurry without wind .

Greetings

Gideon

[gosstyla]

"Having a diesel electric system with or without batteries can be more efficient than having straight diesels"

Is possible - but hard to accomplish.
My OSSA 25KW gensets (originally designated as 28KW) use the SmartCar 45 bhp diesels. The gensets then drive the 35 hp (originally designated as 37hp) electric motors.

"the other advantages are of course also having less noise ..."
My installation was quieter at slow speeds, say in a harbor. However, while on passage the noise difference was not that noticeable since all the noises from:
shaft
prop
waves
wind
rigging
autopilot
etc.
were not affected.

Also, concerning props. Originally my boat was fitted with 22"x16" Flex-o-fold 3 bladed props with the electric motors max rpm set at 900. It was thought the electric motors could handle any size prop we could fit. The boat was over propped and was refitted with 21"x14" and the electric motors max rpm was changed to 1100.

[Alan Wheeler]

Hi Gideon, Don't get me wrong, I am not complaining nor complaining about the battery side. What I am trying to get across is that it seems some believe a Diesel/Generator/electric drive (and only that scenario) is more efficient and less maintenance than a Diesel/Gearbox system. The other stuff was more "on the side". I do think an efficient and affordable electric system will eventually happen, due to the hard work and determination from ones like yourself in the industry. In fact I feel envious because I would love to play with the concepts myself. I want to see some system other than what we have as convention now. But I think they only way we can really truely see "a real" solution to the issue, is for ones that have some knowledge to also try knocking the system. This is a challenge. I want you to prove me wrong. I want to see some real forward moves in this industry and I believe you guys are doing well at achieving it. But I think the true advancements are going to come from some very outside the box thinking.
Good luck.

[fastcat435]

Hallo Alan

I will prove you wrong this year much to your and my pleasure.

All the testing on a land based basin is completed including regeneration and propulsion of the Green Motion system We are finishing of the first Green Motion FastCat 455 around the end of August and I expect to be able to sail this cat to Europe from Durban South Africa via Miami without or with minimal use of fossil fuels .
This system will only work well in a very efficient vessel under both sail and power and I have to go all the way to make it work so Lithium Ion will be on board combined with a lightweight generator, solar panels, wind generator and all the energy efficient lights, induction stove, instruments, watermaker, Autopilot, etc that are presently available.
This 46 foot cat will weight no more than 7000 kilo all complete to go
We will have 1600 watt of solar panels on board combined with a mast head mounted wind generator a 13 Kw diesel generator 15000 watt of usable power for the propulsion system and 5000 watt usable for the service system.
The idea is not to use any fossil fuel at all but we will have 300 liters of diesel on board for emergency use only.
Even the hot water is made by wind generated electricity.
I have no fantasys regarding not having luxurys on a yacht this size so even a dishwasher is on the boat .
The heat from the electronic controllers will warm up the hot water system both when under electric propulsion or when generating electricity
This will also minimize the extra heat normally created in a boat that we can do without.
In a previous trip of around 15000 NM i have used close to 1500 liters of diesel and it will be a challenge not to use any but even if we end up with having used all 300 liters of diesel that is still a saving of 80 %
Once we start the actual testing in the water we will start a Log update with the test results. I am sure many sailors will find it interesting .
So far most of the electrical systems have used of the shelf motors , generators , props etc. while in our case everything is new designed from the prop to the retractable motogen, controller and generator even the Lapp cable is made to minimize resistance Even the FastCat 435/455 was originally designed with a retractable system propulsion/generating system in mind

Greetings

Gideon

[Alan Wheeler]

Cool, so when do you send me a boat and system for testing and evaluation ;-) :-)

[Maren]

I think I know what Sandy is saying here. His information comes mostly from three articles Nigel Calder (NC) wrote for Professional Boatbuilding but there are others where the information is summarized. As I understand it there are three technologies that are not totally online yet; there are:

Smaller diesel generators with high out put.
Smart charge controllers
Battery storage
In my opinion, the lynch pin here not the engine vs generator issue but rather the battery technology. But this is true not only for either set-up but for multiple industries and applications.

To be fair (see March ’06 Sail Magazine, pg 98-103), NC also had time wrapping his head around why a D/E system would be more efficient. And he doesn’t know that it will be but is willing to take the risk. He believes that since diesel generation has been used in other industries prior to, it will be easier to make the leap and engineer for the needs of the recreational boating industry. NC has also pointed out that he is in a unique position in that he can write any problems or merits and be paid for it.

Still, NC anticipates some advantages. If he didn’t why would he get rid of his own boat just to emplace a D/E system in copy? Among the perceived advantages are:

Less wiring due to a ‘three wire boat’
Lighter wiring due to an increase in voltage
Lighter generator compared to an engine
Cats can have their two engines replaced by one generator and two electric motors

The ability for relocation is, to me, an underrated advantage. Should the whole set up work, it should be possible to soft-mount a generator on a platform on rails, much like file cabinet. Pull the pins, slide the generator out and you are now working in a more open area. Of course, this would be dependant on other structures and might not work for all boats.

To me, the weak point for generator argument is prolonged use. If I run a smaller generator that is optimally engineered to running the exactly sized prop at the best speed with just a little extra for other uses, what happens when I need all that power and more for a prolonged time? We would hope the less important systems would be automatically shut down in a lowest to highest priority, but I am not all that sure I trust engineers and programmers to do that.

Originally Posted by Alan Wheeler

Sorry, did I miss the release of a new Battery design?? I thought that was still in development and is still only found in a few experimental electric cars.

Kind of, but not really. It isn't online but was written about in one of the articles.

Just because it is Nigel Calder, so what? We have some of the best in the industry here as members

Just out of curosity, who are you referring to? I know for sound related gear you're an expert and I know Mr Kollmann is for refridgeration. There are a few boat builders and some diesel mechanics, too. But I don't really know any for something like this.

One last thing. I think there was a side by side comparison between an Outremer with a D/E system vs a conventional. No weight savings noted. Fuel for the D/E was about 50% that of the conventional. Worth it price wise? That would be up to us as individuals to decide.

[sailvi767]

Originally Posted by ess105

I am reminded that there are many folks who manage extensive travels without use of a motor. I doubt they get out and push when the wind drops. I may be proved wrong but I'm gearing myself to wait when the wind drops and just enjoy myself where I am.

I'm not sure what hybrid system you are referring to when you say the speed loss is "huge". On the hybrid Lagoon 420's the cost of regeneration is at worst 1 knot. That is assuming the system is used correctly. If you don't let the props spin (by leaving it switched off) then the drag is greater. Along with sitting around when the wind drops this will add to trip time. Given that the 420 is a very livable boat this is not an issue for us.

While you are correct you are only losing one knot to regenerate you are also losing speed on top of that from the large size props required on the boat in the first place. I would suspect you start out with about a .75 to 1 knot disadvantage from the props. This comes from a Lagoon 440 electric sailing alongside a regular 440. Then if you add in the additional advantage that can be gained on a regular boat with folding props you could be talking a significant number.

The bigger issue I worry about is reliability of the propulsion system. Electrics hate salt air. Gensets are not nearly as reliable as propulsion diesels especially in charter operations. I have had one main engine failure in 20 years that quickly restarted. I have lost count of the number of generator failures I have had. I am aware of two 420's that have been left without any power in the BVI in the last year. One was on a lee shore and the situation could have turned nasty had quick action by the crew not been taken. The number one killer of a generator is cycles. The genset on the Lagoon 420 seems to cycle on and off quite often. The G2 upgrade may help with this. I would be very surprised if the 420's in charter can go more then 4 years on the original genset perhaps far less. The cost to replace a 22k genset is going to be expensive. The fuel burn issue with such a large genset when AC is in use at night is already well know. Most of the above comments apply to charter use since that is my focus. I am really watching the 420's because I do like the potential of the technology. I am just not sure its ready for prime time yet particularly for charter operations. My next boat will be purchased in 3. to 5 years. I am hoping that the technology will be there for that boat. There is a story on sailnet now about a 420 in charter in the Bahama's with electric issues. I know the BVI boats have had far more issues then conventional boats. The cost to the owners gets high with chase boat calls.

[jzk]

Originally Posted by Maren

One last thing. I think there was a side by side comparison between an Outremer with a D/E system vs a conventional. No weight savings noted. Fuel for the D/E was about 50% that of the conventional. Worth it price wise? That would be up to us as individuals to decide.

I remember reading the article. Do you have data so support the weight and savings conclusions?

[fastcat435]

Cycling of generators or the number of cycles is always a problem the lower number the better of you are Our generators are preset to start at 40 % of battery power and stop at 90 % to keep cycles to the minimum If a second generator is installed since that is an option the 2th unit will start when the power level of the lithium ion batterys, drops below 30 % and will switch of again when 85 % is reached.
the Sequence or of these 2 generators can be switched to start up in a 1 2 sequence or the ohter way around , it gives redundancy
In Green Motion , the FastCat 455 that is being build for testing of the system we install a 11 and a 13 KW genset while in most other cats we have sold one 18 Kw generator is installed .

Greetings

[sailvi767]

Fastcat, I always thought that having two gensets was the way to go in this type of application. You gain redundancy and it should dramatically cut fuel burn. If the Lagoon 420 had two gensets you could have had a 15 or 16KW and then a small 6KW. The 6 could be used at night for AC and house uses really cutting down the fuel consumption. It would also provide a backup to the main genset for propulsion.
George