Diesel/Electric Propulsion for Sailboats

[westsail42]

Anyone experienced an EMotion Hybrids Installation?

Looks like they are doing Calders new Malo.

[masalai]

Thanks westsail42, have bookmarked the site for reference...

[Pericles]

African Cats seem to have all bases covered in regard to powering cruising catamarans. http://www.africancats.com/

They are using Lithium ion batteries.
http://www.africancats.com/resources...NG15062006.pdf

westsail42,

Thanks for the link.

Regards,

Pericles

[mp459]

Wow, this is quite a thread. I'm interested in repowering my current boat in the next 3 years or so, and am looking quite a bit into DE. The only thing missing here is pricing–that 98k figure is rather high. But apparently not too–just got a reply back from Glacier Bay:
First, they didn't sound too optimistic:
" I am not sure that what we have at the moment will be ideal for your boat. We have done a retrofit of a Nauticat 43 motor sailer that would be the closest similar project."
Second, price:
"The list price for the motor, controllers, power distribution box, and helm station would be $$49,231."
Yipes! 50k. So let's say a direct-drive repower costs 15k. Add another 5k+ for a generator (more on this later), and some electronics etc…lets say you get by with 25k. That's twice the price.

But more to other stuff…most of the comparisons I've seen extol or criticize DE systems compared to direct-drive systems. I'm on a 38ft monohull sailboat, adn use the engine for propulsion about 10% of the total underway time in inland /coastal sailing (say 2 hours a day to motor in/out of a marina out of a 10 - 48 hour trip, without going into specifics I'll posit this is on average 10%). On the other hand, I need to charge the batteries regularly—I don't have much space for a separate generator nor oversize battery bank. And we all agree that using the propulsion engine for battery charging is less than ideal. This said, the appeal of DE systems to me is not the energy savings while powering/motorsailing. The appeal is that I replace my propulsion engine with a generator that takes care of the electrical loads, battery charging, and allows me to anchor out more frequently. The fact that I can run an electric motor to propel my vessel is in some ways a secondary concern: True, I would not replace my propulsion engine with a generator and go sail-only; but if a generator can produce enough power to propel my vessel, and if the system is efficient and silent enough to allow me to have a smaller battery bank, then I see some definite advantages.

On the other hand, are those advantages worth the extra $25k? Additionally, I'd like to attach some type of generator to a freewheeling prop to generate some power while sailing. No answer from other Glacier Bay nor whisperprop/fischer panda on this. (No reply from whisper prop period.)

Interestingly, it seems that most DE systems are installed in catamarans. Perhaps it makes sense here because you can get rid of two diesels. But the emphasis even here seems to be on propulsion.

Last note, although a good number of people I respect seem to prefer the hybrid solution/parallel solution (motor can be powered from hundred-volt battery bank), it seems to me this solution adds a lot of weight to the boat. On a new installation where you can use the batteries as ballast, that may make sense. But I haven't found the motor+generator in DE to weigh significantly less than engine+transmission (in direct drive) to offset the extra battery weight: 100Ah batteries @144V weigh in at over 800lbs. (Sure you can get that weight down to about 50-100lb if you use smaller batteries, but then there's not enough capacity to drive the motor under battery power, so the motor has to start up anyway.) Moreover, the freewheeling prop in these configurations serves to recharge the motor batteries, not the house bank. And since I've given up on carrying an extra half-ton of batteries and therefore resigned to propelling with the engine running, I want to minimize engine time precisely when I'm not motoring.

Am I completely off-base here? Any comments?

Again, I'm amazed by this thread. Thank you all for your insight, and I'll keep posting updates as I find them. I've already contacted Glacier Bay (and have some diagrams from them if anyone is interested), and F. Panda. I think I'll try the EMotion guys as well.

Best,
mickey

[westsail42]

Originally Posted by mp459

Am I completely off-base here? Any comments?

Mickey,

No, you are right on target with all of reasoning as far as I am concerned. All valid issues you raise.

I think a lot of it depends on whay type of boating you do. For example, take the issue of battery weight. If you dont mind running a generator (GB) and are concerned about weight (144v bank systems) you can use small batteries if you are so concerned about weight.

If you are more of a cruiser and less concerned about performance, you can go big 8D 144V bank to accomodate alternate input sources (wind/solar/whatever).

It seems once of the niceties of D/E is that there is a degree of flexibility in the configuration when dealing with a new build/build out. Not so much on a retrofit.

[mp459]

Thanks, Robert . Sometimes I feel like either I'm not getting the whole world, or the whole world is not getting me. Had a chat with GB just a while ago. The guy said, "If you're happy with 6-6.5 kts, then we have a good fit". 6.5kt? I get 5.5 now! He also said that they're working on a 240V DC bank and power 'regeneration' stuff. Now if the price goes down a bit…although I doubt I'll be installing for another year or two so there's plenty to happen between now and then. He also mentioned that it'd be possible to drive a separate 12V dynamo geared to the prop shaft, which is my plan for direct-drive anyway.

Nothing else new and exciting to report from them. Still no word from F-P or anyone else. I am excited about the new battery technologies though. Any tests yet on discharge rates on these? If we can maintain battery life while increasing max discharge they're a no-brainer.

Out of curiosity, Robert, how far along are you on your Westsail? I've perused your blog but haven't dug too deeply. I sail-while-i-work-on (or work-on-while-i-sail) a 1980 CR38. Not quite from bare hull, but seems I've had to get ot bare hull and back in a few areas…and had to redo the whole deck. Rebuilt the old perkins to give DE a few more years to mature.

Cheers,
mickey

[Pericles]

Mickey,

Check the Nigel Calder articles in Professional Boatbuilder.

http://www.proboat.com/digital_issues.html

Page 74 Issue 112

Page 104 Issue 111

Page 140 Issue 109

They should help.

Regards,

Perry

[mp459]

Perry,
many thanks for summarizing the issues here. I have seen you and others post them earlier in the thread and have read what I can find. I have a lot of respect for Nigel Calder so I take what the articles say quite seriously. As expected, these articles were very informative, indeed; but I must agree with an earlier poster: most of what's out there seems to focus on the DE vs. Direct-drive comparison. The way I see it, I use my propulsion engine for battery charging more than propulsion so I prefer to look at the entire power consumption equation. I liked the 3-part series in electric propulsion, but even that focused on traditional vs DE for propulsion efficiency (the third article mentioned additional benefits, but the efficiency part of it still focused on propelling the boat).

Bottom line as I see it: A DE system is the way to go–but the question is when? I think the list price on a DE system is still too expensive compared to traditional systems…but it's not so far off that if retail is reasonably below list the extra money wouldn't be worth the price. further, with production boats getting on board, I would expect the price to drop in the next year or two, which is why I am reconsidering DE now for a possible installation in the next year or two. When I first looked into it, about 2 years ago, the product was not quite there yet.

Thanks again for all your input in this thread!

Y

[masalai]

mp459,
You may like to keep an eye on these linked threads which we set up to keep tabs of sites and developments here is one http://www.boatdesign.net/forums/sho...d.php?p=205049 - all the threads have cross-links at post #1....

[mp459]

Thanks, Masalai. That's one thing I still need to do: subscribe to all the linked threads. i've read through some of them, but certainly not all.

[masalai]

Because the first page/post is cross-linked I only bookmark one, and check all through the links periodically....I may hive off an extra one if developments occur in solar panels (University of Queensland media release)... there are 6 or 7 threads...

[westsail42]

Originally Posted by mp459

Out of curiosity, Robert, how far along are you on your Westsail? I've perused your blog but haven't dug too deeply.

Slowly but surely as they say. This year we are doing the "rough-in" of bulkheads and dividers. Also mocking up cabinetry to get a feel for proportions. With the detail to work to start next year. The big $$ thing is we hope to have the rudder and steering installed by the end of year.

Things are slow now as we prepare our 28 foot sloop for a summer trip.

[westsail42]

Originally Posted by mp459

Bottom line as I see it: A DE system is the way to go–but the question is when? I think the list price on a DE system is still too expensive compared to traditional systems…but it's not so far off that if retail is reasonably below list the extra money wouldn't be worth the price. further, with production boats getting on board, I would expect the price to drop in the next year or two, which is why I am reconsidering DE now for a possible installation in the next year or two. When I first looked into it, about 2 years ago, the product was not quite there yet.

Y

I see things the same way. One of the reasons we are not in a rush to build out the Westsail. We havent decided upon D/E, but I sure would like it to be a "viable candidate" when the time to install propulsion comes.

[mp459]

Good to hear you have a sailable boat while you're working on it. When I first started taking major things apart on Bahia, a wise soul (not to be compared with a wise guy told me to get projects small enough that I can go sailing in between. Keeps the sanity that way!

P.S. Masalai, thanks for the link to your 'summary' thread. Bookmarked that as well.

[mp459]

Originally Posted by westsail42

I see things the same way. One of the reasons we are not in a rush to build out the Westsail. We havent decided upon D/E, but I sure would like it to be a "viable candidate" when the time to install propulsion comes.

On a slightly different tack, one of the things I haven't been able to figure out is two different ideologies in the power requirements. Sure, I'll agree that the propulsion engines we use now are not used at peak performance most of the time, but we fit a 50-horse engine because of the 5% of the time when we might actually need all that power, to free from a soft grounding, for example, or in rough weather. Whether either of these is good practice or not is irrelevant, I'll just posit that this is common practice.

Nigel Calder and others claim that a lot of the efficiencies claimed by DE systems are gained by (sometimes "radical") power reduction in the propulsion engine as well as the generator. He says a better comparison would be a DE setup vs. a reduced-power conventional installation.

On the other hand, DE evangelists say that you don't need the extra power because you have a more efficient power transfer, and besides it's the extra torque you need, not the horsepower.

Even so, both parties seem to agree that there is not enough loss with this "radical power reduction" to make any significant difference in powering, even in seaway and headwinds. However I have heard nobody advocate for reduced power in a conventional engine as a means of gaining "efficiency".

So some math: say I have a 50hp engine which has about 30% loss to the shaft…that's about 35hp/26kW to the shaft. This is about the DE generator produces in a matched setup, as far as I've seen. However, the electric motor paired with this is usually about 40% smaller, 16kW/21hp. (And again, no one has advocated that I replace my 50hp with a 30hp conventional-drive engine). Most answers to this have something to do with torque: the 16kW motor provides as much torque as the 50hp diesel.

Based on hp = torque x rpm / 5252 (from Emotion), a 50 hp @ 3500RPM diesel can provide 75lb.ft. The EMotion guys claim their 16kw can provide 120lb.ft. In order for a similar diesel (max hp@3500rpm) to provide 120lb.ft you'd have to get an 80hp diesel. So, assuming Torque is the Answer, here is the 40% less power. If your engine provides max hp at 4000 rpm these numbers get even better in support of DE claims.

Glacier Bay paired this engine with a 26kW (35hp) motor, producing 102lb.ft@1800 rpm, and we can make similar claims.

But if it's that simple, then how can someone claim that a true efficiency comparison should be between DE and a similarly-sized conventional-drive systems, when the conventional system would not have the necessary torque to power the boat?