Electric Propulsion

[skipmac]

Originally Posted by Adamante

I am afraid you are misinterpreting the ASMO sales literature.

Well I don't think so. I used exactly what is said on their sales literature and used very straightforward calculations to convert the numbers.

Originally Posted by Adamante

It's just an application guide to help you with the motor selection. All they are trying to tell you is that if your diesel engine is sized somewhere between 25 and 40HP, you should install their 12 KW motor.

Yes that is exactly correct. So I took their guideline and extrapolated the range they gave for the 12KW for 25 - 40 HP to 58-60 HP and turned the data around to look at it from the other side to calculate the same range of KW that would equate to a 58 HP diesel. I described it as the low end and high end but isn't that another way of referring to a guideline, a range or max/min? Seems to me we are saying the exact same thing with different words.

Then as I prefer to err on the conservative side stated I would target on the high end of the "guidelines" which is where I derived my final number.

Originally Posted by Adamante;738130The operative number is upper range of the spec, i.e., the 40 HP . They mean that their 12 KW motor will replace [B

any diesel up to[/B] 40 HP. You could certainly use the 12 KW motor to replace a smaller diesel, but why? If you have a smaller diesel, say a 20 HP, ASMO will sell you a smaller system that will provide a more appropriate power match.

Of course not. That is obvious and I never said anything about using a larger electric motor to replace a smaller diesel. Not sure why you bring this up.

Originally Posted by Adamante

BTW, I don't even see a 12 KW system in the Thoosa product line. The closest one would be the Thoosa 13000, which is a 13 KW system.

Got the data right here from the Annapolis Hybrid Marine who is the exclusive US importer for the Thoosa drives.

http://www.annapolishybridmarine.com...OOSA_12000.pdf

FYI I just had a long talk with a very nice person named Sally Rucker (hope I got the correct spelling on your last name) CEO of AHM and invited her to view this thread. In general she did not disagree with any of the conclusions I have drawn from data I derived from ASMO spec sheets.

They are in the final stages of installing a 12KW system in a 44' Hylas and will be be publishing test results from trials. She felt like a 12 KW in the Hylas was a bit underpowered compared to the stock diesel power. I really look forward to their test results. Should put a lot of speculation to bed.

[Adamante]

Originally Posted by skipmac

Of course not. That is obvious and I never said anything about using a larger electric motor to replace a smaller diesel. Not sure why you bring this up.

Because in the previous post I had originally responded to, you seemed to imply that a 60 HP diesel might require a 28 KW electric motor, which seemed excessive. But maybe I misunderstood your post.

Originally Posted by skipmac

Got the data right here from the Annapolis Hybrid Marine who is the exclusive US importer for the Thoosa drives.

Yes, it appears that ASMO has changed the US distributor from a couple of years ago. And it looks like they also adjusted their product line. The new top of the line is this 12000 system, which appears to be the old 13000. They dropped the 17000 system.

Interestingly, the 12000 system link you provided has a reference to the old 13000 on the right-hand side of the second page of the PDF document. ("Thoosa 13000 Kit" ). I guess they haven't quite changed all their sales literature yet.

But given your requirements of trying to replace a 58 HP diesel, their 12000 system probably won't cut it, so you might need to look for an alternate vendor.

OTOH, if their test installation on 44 footer produces satisfactory results, you may be able to reconsider your power requirements.

In any case, I am glad you found the info you were looking for. I will be interested in what you decide to do.

[LauderBoy]

Originally Posted by Adamante

Yes, it appears that ASMO has changed the US distributor from a couple of years ago. And it looks like they also adjusted their product line. The new top of the line is this 12000 system, which appears to be the old 13000. They dropped the 17000 system.

Interestingly, the 12000 system link you provided has a reference to the old 13000 on the right-hand side of the second page of the PDF document. ("Thoosa 13000 Kit" ). I guess they haven't quite changed all their sales literature yet.

They dropped the 17k system? Wonder what kind of problems they had with it. Or maybe it just didn't sell well enough because it's the sub 40ft boat crowd that's mostly playing with the tech. The only either vendor I know of is Electric Yacht - Electric sailboat propulsion systems that are cost-effective, yet CLEAN, GREEN and QUIET! and I think their top end is a 6.5kW system or a "combo" setup of 2 of those. I'm not sure how they combine them.

Wonder if there's problems with the tech on larger boat installs. You see quite a few people happy with the 9k on down systems.

[chris07732]

I had a bad experience with ASMO 3-4 yrs ago, repowering my 40' motor sailer with the THOOSA 17000 system. ASMO, in my opinion, hung their US rep out to dry with promises of delivery of components for my project that never happened. I've never been "next month'd" to such a degree. For my $4k deposit, and 2 yrs of involvement, I only got the 17kw Lynch motor. ASMO, being offshore, is untouchable and the rep was at their mercy. Ultimately, I abandoned the project and installed a new Yanmar. Be careful dealing with ASMO thru reps.

It's probably not proper to go into much more detail on this forum, but if anyone wants more info, contact me privately.

Chris Francy

[Adamante]

Originally Posted by Lowcountry

I have two sets of friends who own Lagoon 420 Hybrids.

OK, so that's a sample size of two. Not overwhelming... but not insignificant either.

Let me try to help. I myself have recently seen a Lagoon 420 for sale on Yachtworld that was advertised as having been converted from a hybrid to a diesel. So that would make a sample size of three.

Unless, of course, that Lagoon 420 on Yachtworld was actually one of your friends' boats for sale, in which case we would be back to a sample size of two.

But... at least you have friends! and with Lagoons! ... I am soooo jealous!

What would really help this thread, as well as any prospective electric propulsion buyers, would be if you, or your friends, were willing to post some details of why they felt the need to convert to diesel power.

Were the motors undersized, not allowing the yachts to achieve adequate speeds?

Were the motors unreliable, perhaps tripping out on overheat? Was there adequate ventilation?

Were the controllers unreliable? In what way?

Was the battery bank undersized?

Did they buy their hybrids for the wrong reasons, i.e., visions of eco-friendliness, fuel savings, weight savings, regeneration, etc.?

Any additional information would be appreciated.

[skipmac]

Originally Posted by Adamante

What would really help this thread, as well as any prospective electric propulsion buyers, would be if you, or your friends, were willing to post some details of why they felt the need to convert to diesel power.

Were the motors undersized, not allowing the yachts to achieve adequate speeds?

Were the motors unreliable, perhaps tripping out on overheat? Was there adequate ventilation?

Were the controllers unreliable? In what way?

Was the battery bank undersized?

Did they buy their hybrids for the wrong reasons, i.e., visions of eco-friendliness, fuel savings, weight savings, regeneration, etc.?

Any additional information would be appreciated.

Yes. Would really like to hear this info.

[skipmac]

Originally Posted by Adamante

Because in the previous post I had originally responded to, you seemed to imply that a 60 HP diesel might require a 28 KW electric motor, which seemed excessive. But maybe I misunderstood your post.

I believe that was based on another calculation based on different assumptions.

1. Depending on whose estimates you see, an ICE will lose +/- 25% of the rated power in friction and parasitic loads. So 60 HP at the flywheel = +/- 45 useable HP at the shaft.

2. Assuming other efficiencies and higher torque at low rpm from electric fudge that down another 20-25% to 45 HP to 35-40 HP.

3. 0.746 KW / 1 HP yields 26-30 KW.

Obviously the real world math is a bit more complex, but again, you have to start somewhere to begin the comparison and where to start more detailed research. And, other than the undocumented statement on the Thoosa spec sheet for the 12 KW = 25-40 HP ICE, I have seen no hard evidence or data of any kind to refute this calculation.

Until I can see performance results on same boat, same conditions with X KW electric vs X HP diesel I will remain skeptical.

[Adamante]

Originally Posted by LauderBoy

The only either vendor I know of is Electric Yacht - Electric sailboat propulsion systems that are cost-effective, yet CLEAN, GREEN and QUIET! and I think their top end is a 6.5kW system or a "combo" setup of 2 of those. I'm not sure how they combine them.

There is also Dave Tether's E Motion Hybrids Motors

He's got an 18 KW motor with a hellacious torque spec, but probably a hellacious price too. The 9 KW version of that system lists for $18K, as compared to $8K for the 9 KW Thoosa with the Lynch motor. But the torque is almost double compared to the Thoosa.

[daddle]

Originally Posted by skipmac

1. Depending on whose estimates you see, an ICE will lose +/- 25% of the rated power in friction and parasitic loads. So 60 HP at the flywheel = +/- 45 useable HP at the shaft.

2. Assuming other efficiencies and higher torque at low rpm from electric fudge that down another 20-25% to 45 HP to 35-40 HP.

#1 above is incorrect. The rating for diesels from all reputable manufacturers is 'shaft horsepower. That is the power you can extract from the engine. The prop will see maybe 5% less due to losses in the transmission. All the other losses in the engine are accounted for in that calculation. Of course the alternator takes some power if charging, but that should be ignored for this comparison as the electrical loads of the boat subtract from the electric driven case as well.

#2 is incorrect. There are no other inefficiencies. The particular property of propellers is that they cannot use that extra torque at low speeds. Huge torque at low speed is useless to the typical cruising boat. You'd need a variable pitch prop, like on a tugboat, or Dashew's boat, to make any use of it.

It's interesting that I asked for proof of this claimed 250% disparity between "diesel hp" and "electric hp" and have received none at all. Interesting but not surprising. Consider my small boat. She has nominal 20hp/15kW Beta diesel. At around 1200rpm at the prop she has about 100Nm of torque. Not surprisingly the Thoosa 12000 (12kW) datasheet claims about the same: 1270rpm and 90Nm. Do you think the prop can tell the difference? Does it taste different of something?

Diesel hp and electric hp are the same. I'm actually pro electric propulsion. But I'm pro truth too. Watch your wallets folks.

[I did find one engineering reference that recommended that in some constant load industrial applications (unlike boats) that a diesel needed to be about 5% more powerful than the replacement electric motor because the slightly exponential (>1) power curve of the diesel may never allow it to get to the rated rpm. Like downshifting a car to accelerate up a hill, maybe)]

[Dick Pluta]

[QUOTE=daddle;738187]Agreed. So you just shot yourself in the foot? Your equation proves that one diesel HP is equal to one electric motor HP. Thanks.
QUOTE]

EXACTLY!!! 1 HP is 1 HP no matter where it comes from!!!

It is torque alone that matters. Your propellor dosn't understand HP. It only knows how hard you are trying to twist it.

The problem is that horsepower is a misleading rating. A toy motor puts out about 1/2 ft.lb. If you ran it at a million RPM it would put out an astonishing 32000 HP. At 1000 RPM it has nothing. Similarly, my diesel puts out 100HP at 2000 RPM. At idle it has just enough to keep itself running. If I apply a greater load, it simply stalls. Why? Because it does not produce its maximum torque until 2000 RPM.

I tried to make a little chart that illustrates this. I think I have attached it. It's a JPEG. It shows that the diesel makes very little torque at idle, while the electric can produce maximum torque immediately. The demand line shows that the diesel doesn't produce enough torque to drive the load until about half throttle. The electric has it immediately. The only reason a diesel has to be "bigger" is to shift the torque curve upward so that you can get more "horsepower" at a lower RPM. If you need 100 HP at 1000 RPM it does no good to have it at 2000 RPM.

It's a tough thing to understand. Even trained engineers don't always get it. Try this. You're trying to remove a screw. You apply a little torque to the screwdriver. Nothing happens. You apply a little more and then even more. Finally you overcome the resistance of the screw and it turns. There's horsepower in there somewhere but it doesn't really matter. It's all about TORQUE!

As a prime mover, electric is great. The problem is not the motor. It's getting the electricity to drive it.

[Adamante]

Originally Posted by daddle

It's interesting that I asked for proof of this claimed 250% disparity between "diesel hp" and "electric hp" and have received none at all. Interesting but not surprising.

What's really interesting (but not all that surprising) is that you apparently missed my post #111 which directly addressed your request for this proof. You know, the post that starts with "If you are willing to accept the notion of "the proof is in the pudding", there are numerous examples of boats with electric propulsion..."

There are times when the "rational" engineer will realize that the math and physics are too complex and arcane to be of much practical use, and will grudgingly accept the empirical evidence presented by the real world. I know it's not easy, but it can definitely be done!

[Adamante]

Originally Posted by Dick Pluta

The problem is not the motor. It's getting the electricity to drive it.

That is 100% correct, IMO. The focus of some skeptics on electric motor ratings are just an unfortunate distraction in a debate about the real issues faced by electric propulsion systems.

[skipmac]

Originally Posted by daddle

#1 above is incorrect. The rating for diesels from all reputable manufacturers is 'shaft horsepower. That is the power you can extract from the engine. The prop will see maybe 5% less due to losses in the transmission. All the other losses in the engine are accounted for in that calculation. Of course the alternator takes some power if charging, but that should be ignored for this comparison as the electrical loads of the boat subtract from the electric driven case as well.)

First, let me say that I am not personally endorsing the assumptions used in the calculations, just using some commonly stated numbers as a starting point for a calculation. If you just convert diesel HP to KW and assume that you need an electric motor of that size then my 58 HP diesel would require a 43 KW electric motor! Real world results seem to indicate that this would be gross overkill, so there have to be some adjustments in the conversion somewhere. So where are they.

I will question a couple of your claims in point #1. By parasitic losses I am referring to alternators, water pumps (2 in the case of most marine engines) etc which I have read from numerous sources can consume several HP in addition to the 5% loss you mention in the tranny. I can't say how all engine makers do it, but again my understanding is that these loads are not factored in to most engine HP specs.

Then electrical loads on the boat do not take any power away from the electric motor drive (from the total power supply available to the motor yes) so are not relevant to calculating the size of the electric motor needed to push the boat.

Originally Posted by daddle

#2 is incorrect. There are no other inefficiencies. The particular property of propellers is that they cannot use that extra torque at low speeds. Huge torque at low speed is useless to the typical cruising boat. You'd need a variable pitch prop, like on a tugboat, or Dashew's boat, to make any use of it.)

Don't know. Again, as I said, this was just a fudge factor tossed in to allow for claims from the electric drive suppliers that the electric motor gives more bang for the KW.

Originally Posted by daddle

It's interesting that I asked for proof of this claimed 250% disparity between "diesel hp" and "electric hp" and have received none at all. Interesting but not surprising.

I would assume that builders that offer both options would have some performance comparisons. For example Lagoon? Any published figures?

Watch your wallet? You bet. The best numbers I have seen so far indicate an overall cost double to triple that of a comparable diesel to go electric when you factor in power generation to give you equivalent cruising range.

[skipmac]

Originally Posted by Adamante

What's really interesting (but not all that surprising) is that you apparently missed my post #111 which directly addressed your request for this proof. You know, the post that starts with "If you are willing to accept the notion of "the proof is in the pudding", there are numerous examples of boats with electric propulsion.

Read that post and, while interesting, observing similar transit times for electric vs diesel on a long passage does not show equivalent power and performance. Typically on a long voyage the engine is run to motor during calms, a situation where one can achieve cruising speeds with a fraction of the HP needed to motor against wind and waves.

I want to know if an electric motor can do the job in a demanding situation, not in a calm where I could get reasonable speed towing my boat with a dingy and a 10-15 HP outboard. Will I have the power it takes to get me under a lift bridge with a strong counter current and cross wind pushing me into the pilings? If someone in a dingy pulls out in front of me while I'm motoring down a narrow canal will I have enough power to reverse and not run the guy down?

Put two identical hulls with different power and motor against a 15 kt wind and 3-4' seas then compare the results.

[Adamante]

Originally Posted by skipmac

Typically on a long voyage the engine is run to motor during calms, a situation where one can achieve cruising speeds with a fraction of the HP needed to motor against wind and waves.

I am not sure I would agree with that generalization. Maybe it depends on one's individual cruising style, but I note that many cruisers will often motor when faced with adverse winds and sea state, in addition to motoring in calms. If you read the blog of the Green Motion on their passage from South Africa to Holland, they frequently ran their motors to counteract precisely those conditions.

Anyway, I think we are doing a pretty good job of beating this one to death. (now where is that dead horse icon...)