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Old 22-12-2018, 11:23   #1801
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
. .. Great analysis, unitless helps simplify it a bit without losing the point. We don't totally agree on the bearing count, but not to enough of a degree to matter here. I was backing out all the car gear from 88% and getting 95% as well.

Just out of curiosity, how do you make the bearing count? Boat would be 4 -- two on each shaft. Car 6 in the gearbox -- two on each shaft. Rear axle of a rigid axle car -- another 4 I think. With IRS another 6 plus two CV joints. No?


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This is all assuming this ONE particular study we are using as our input is good, and that we can accurately back out the contributions for the rest of the drivetrain. These are reasonable, but not unassailable assumptions.

Absolutely agree. Would be nice to have some more data points. But if we're after an approximation based on best available data -- I think we got it.




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I still contend that the efficiency is a little lower than 95% based on straight analysis of the gearbox itself, BUT I need better data than what I have so far. 98 or 99% for a helical gear is quite a wide range in the scheme of things. I do think we are bounding the efficiency, in my mind it's no better than 95% and no worse than 90%, and I've updated the DD/EP model I'm working on to reflect that.

I would say no LESS than 95%, and no way to get as little as 90%, at least based on the one data set we have. What was wrong with this: "A percent or two for a set of gears, a percent or two for 4 bearings, and a percent or two for churning -- adds up to roughly what we would expect if we think a boat transmission is roughly 95% efficient"





And WHY are we discussing this? It all started with the idea that losing the gearbox on a hybrid makes up for the conversion losses. So we might want to look at the other side of that equation -- what are the TYPICAL conversion losses in a diesel-electric system.
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Old 22-12-2018, 11:48   #1802
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Re: Oceanvolt Hybrid Motor

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Originally Posted by Dockhead View Post
Just out of curiosity, how do you make the bearing count? Boat would be 4 -- two on each shaft. Car 6 in the gearbox -- two on each shaft. Rear axle of a rigid axle car -- another 4 I think. With IRS another 6 plus two CV joints. No?
The input and output shafts are coaxial and may only have one bearing in the center. Not enough to invalidate your analysis.

Also I'm not counting IRS or mid-engine or...




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Absolutely agree. Would be nice to have some more data points. But if we're after an approximation based on best available data -- I think we got it.
Agree, I am looking over one more source now, but it's an auto transmission which complicates things, and I don't think adds value to the discussion, seems similar results would be found.

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I would say no LESS than 95%, and no way to get as little as 90%, at least based on the one data set we have. What was wrong with this: "A percent or two for a set of gears, a percent or two for 4 bearings, and a percent or two for churning -- adds up to roughly what we would expect if we think a boat transmission is roughly 95% efficient"

And WHY are we discussing this? It all started with the idea that losing the gearbox on a hybrid makes up for the conversion losses. So we might want to look at the other side of that equation -- what are the TYPICAL conversion losses in a diesel-electric system.
What is wrong: 4 bearings at 99% efficiency plus one helical gear engagement at 98% gives you 94% efficiency without any churning losses.

Why are we discussing? Because I'm separately investigating each piece of the equation. Marine gear is one, and so is typical transmission losses in EP. I have that average at 15% right now and DD transmission at 7.5 percent, difference of 7.5%. This is the efficiency the diesel gen duty cycle or solar/regen has to makeup to match DD.
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Old 22-12-2018, 18:35   #1803
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
. . .


What is wrong: 4 bearings at 99% efficiency plus one helical gear engagement at 98% gives you 94% efficiency without any churning losses.

Why are we discussing? Because I'm separately investigating each piece of the equation. Marine gear is one, and so is typical transmission losses in EP. I have that average at 15% right now and DD transmission at 7.5 percent, difference of 7.5%. This is the efficiency the diesel gen duty cycle or solar/regen has to makeup to match DD.

Well, you misunderstood me. I guess I expressed it badly. When I said "why are we discussing this?" I did not mean "what is the point of this useless discussion"; I meant "let's not lose sight of how we got into this discussion in the first place."


Why do you think every bearing loses 1% of efficiency, when a gear engagement loses only 1% or 2%? I think it's far less than this, and I think in the absence of contradictory data (which might exist, but I haven't seen it), we can think that a mechanical marine drive train will typically lose less than 5%, maybe much less.


But none of that is probably really important. Big picture, I don't think there is any reasonable argument that diesel-electric can produce any efficiency advantage which could justify any significant capital costs, and probably no efficiency advantage at all. Either way -- plus or minus the relatively small amounts we disagree about -- efficiency is not an argument for diesel-electric propulsion, contrary to some of the statements on here. We need other reasons.



One perfectly valid reason is that it is cool, and advances the art.
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"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
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Old 22-12-2018, 19:45   #1804
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Re: Oceanvolt Hybrid Motor

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Originally Posted by Dockhead View Post
Well, you misunderstood me. I guess I expressed it badly. When I said "why are we discussing this?" I did not mean "what is the point of this useless discussion"; I meant "let's not lose sight of how we got into this discussion in the first place."


Why do you think every bearing loses 1% of efficiency, when a gear engagement loses only 1% or 2%? I think it's far less than this, and I think in the absence of contradictory data (which might exist, but I haven't seen it), we can think that a mechanical marine drive train will typically lose less than 5%, maybe much less.


But none of that is probably really important. Big picture, I don't think there is any reasonable argument that diesel-electric can produce any efficiency advantage which could justify any significant capital costs, and probably no efficiency advantage at all. Either way -- plus or minus the relatively small amounts we disagree about -- efficiency is not an argument for diesel-electric propulsion, contrary to some of the statements on here. We need other reasons.



One perfectly valid reason is that it is cool, and advances the art.
I can't comment on your bearing question but I can say that we've already addressed the capital outlay in this thread a number of times. If your only motivation is to spend as little as possible you should buy outboards for your fast, easily driven cat or perhaps some smaller, easily driven monos. Diesels for your slow cat or mono. No one is making the argument that going electric, today, will save you on TCO. We're not at that part of the product lifecycle yet. Certainly not for buying an off the shelf solution; 'home brewers' might view that differently but that path has is own inherent risks and is limited to very few people. Certainly not me.

I've also already outlined a number of other reasons why a sailor or cruiser might want to do it, including reducing fuel(s) on board, but I can add yours to that; it's cool. Also, Capex and Opex often come from different pots of gold, with different tax implications and options, and are outlayed at different stages in an individuals earning life / sailing life. So the efficiency discussion may be very relevant to people who might look to do things 'non-traditionally'. These calculations that we've been very lucky to have people like you and bridaus, for example, collaborating on have been useful also for dispelling a few myths. It's turned into a great thread with the occasional derailment attempt.
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Old 23-12-2018, 13:43   #1805
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Re: Oceanvolt Hybrid Motor

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Originally Posted by Dockhead View Post
Well, you misunderstood me. I guess I expressed it badly. When I said "why are we discussing this?" I did not mean "what is the point of this useless discussion"; I meant "let's not lose sight of how we got into this discussion in the first place."
Good point, and I might have misread...

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Originally Posted by Dockhead View Post
Why do you think every bearing loses 1% of efficiency, when a gear engagement loses only 1% or 2%? I think it's far less than this, and I think in the absence of contradictory data (which might exist, but I haven't seen it), we can think that a mechanical marine drive train will typically lose less than 5%, maybe much less.
Because I also have data that states typical helical engagement losses are 4% and roller bearing at 1% and tapered roller bearing (type used here with axial loads) at double that of ball bearings. There's a reason auto mfg's mileage estimates never seem right, actually, lots of reasons... and I expect it to be slightly worse for boats where fuel efficiency is rarely the #1 selling point. One data point does not close the case but it's a great start, and really glad you found it.

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Originally Posted by Dockhead View Post
But none of that is probably really important. Big picture, I don't think there is any reasonable argument that diesel-electric can produce any efficiency advantage which could justify any significant capital costs, and probably no efficiency advantage at all. Either way -- plus or minus the relatively small amounts we disagree about -- efficiency is not an argument for diesel-electric propulsion, contrary to some of the statements on here. We need other reasons.

One perfectly valid reason is that it is cool, and advances the art.
You hit the nail on the head RE: capital costs currently, I would only disagree with the "probably no efficiency advantage at all". That used to be true, but it's my theory that it's not true anymore and I'm trying to prove it either way...

More later.... wrapping presents... Happy holidays all!
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Old 23-12-2018, 19:56   #1806
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by bridaus View Post
. .. . .Because I also have data that states typical helical engagement losses are 4% and roller bearing at 1% and tapered roller bearing (type used here with axial loads) at double that of ball bearings. . . .

Well, if that were true, then the most efficient automotive gear train would barely crack the 60's % in efficiency (with 9 or 10 bearings and three gear engagements), and yet we have one actually measured set of results of a car at better than 90% under many conditions (and above 95% under some) -- at least one data point.


So color me highly skeptical about helical gear sets costing 4% each and bearings 2%.


Here are some actually measured figures from tapered roller bearings, showing worst case of 12 watts of power lost.



http://www.wseas.us/e-library/confer...M/ACSAM-22.pdf



This is a car application, so presumably transmitting at least 50 kW. 12 watts is 0.024% of 50kW, and indeed 0.12% of even 10kW. Much more like the kind of losses I would have expected, and orders of magnitude off 2%, which would make machines with 9 or 10 bearings practically grind to halt from inefficiency.



But anyway, I think we agree on the methodology and approach, so I will look forward to seeing any more data anyone can dig up.


Merry Christmas, everyone!!
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"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
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Old 24-12-2018, 06:19   #1807
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Re: Oceanvolt Hybrid Motor

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Well, if that were true, then the most efficient automotive gear train would barely crack the 60's % in efficiency (with 9 or 10 bearings and three gear engagements), and yet we have one actually measured set of results of a car at better than 90% under many conditions (and above 95% under some) -- at least one data point.
Not all bearings in the auto drivetrain are taper roller bearings (in fact most aren't). Also when I do the math at these numbers, I get more like 85%, not sure where you get 60...

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So color me highly skeptical about helical gear sets costing 4% each and bearings 2%.
Remember, not all bearings/gears are the same. Even the finish of the gear surface can affect efficiency (lots of those types of studies, but they always talk in terms of "improvement", not absolutes). And since there is zero data on marine gear, we are forced to use automotive studies on car transmissions where efficiency is much more important...

For the record, I don't think it's 4% either, given rpm and load I estimate it's:

Helical gear engagement: 2%
Taper bearing @1K and 2K rpm: 1.0-1.5%
Churning: 2% (would like to pin this down better).

Quote:
Originally Posted by Dockhead View Post
Here are some actually measured figures from tapered roller bearings, showing worst case of 12 watts of power lost.
http://www.wseas.us/e-library/confer...M/ACSAM-22.pdf

This is a car application, so presumably transmitting at least 50 kW. 12 watts is 0.024% of 50kW, and indeed 0.12% of even 10kW. Much more like the kind of losses I would have expected, and orders of magnitude off 2%, which would make machines with 9 or 10 bearings practically grind to halt from inefficiency.
85% wouldn't grind to a halt from efficiency, but it would help explain real world fuel consumption findings.

I had reviewed this study, but have trouble applying it's findings even after rereading it:
  • It's a study for an experimental bearing.
  • It looks like you pulled the 12 watts from the experimental bearing. I doubt marine gear are using experimental bearings, and I doubt even that they are using standard automotive bearings (because the application demands reliability over efficiency).
  • All measurements are below 900 RPM. If you look at the original bearing (not experimental) it was climbing quickly until they reached their RPM limit.
  • No data I found that is in any way relevant to this application (given rpm and load) supports bearing efficiencies below 0.5%.

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Originally Posted by Dockhead View Post
But anyway, I think we agree on the methodology and approach, so I will look forward to seeing any more data anyone can dig up.

Merry Christmas, everyone!!
Agree completely, as more data (even data that we question) is evaluated, it at least sets boundaries.

I'm ready to let this part rest and move on, as I think the accuracy of between 90-95% efficiency is enough to continue the discussion. It is probably not worth our time to find a 2.5% reduction or improvement here when it's all theoretical.

BTW, I'd love to find a study on a new boat that details fuel efficiency as predicted versus real world. If cars can't achieve stated MPG in the real world, do we think boats will fare any better? And why don't they achieve it? Just throwing that question out there...

Ideally one day two identical hulls with EP and DD are studied in the real world using the same duty cycle/conditions and fuel consumption is measured. Until then, we estimate.
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Old 07-01-2019, 20:47   #1808
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Re: Oceanvolt Hybrid Motor

Managed to check regeneration whilst reaching at around 8.4-8.8knots. Was averaging about 1.2kw with fluctuations up and down. It was difficult to accurately determine what the loss in speed was with regeneration on and off as conditions were a bit choppy.

Overall I am happy that the OV does pretty much what i expected it to. It is best suited to lighter catamarans rather than 15t Leopards but I am happy with the performance and the crew are happy with the electric hob and oven and 24hr hot water
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Old 07-01-2019, 23:02   #1809
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Re: Oceanvolt Hybrid Motor

Wow that's sweet!
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Old 08-01-2019, 06:57   #1810
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Re: Oceanvolt Hybrid Motor

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Managed to check regeneration whilst reaching at around 8.4-8.8knots. Was averaging about 1.2kw with fluctuations up and down. It was difficult to accurately determine what the loss in speed was with regeneration on and off as conditions were a bit choppy.

Overall I am happy that the OV does pretty much what i expected it to. It is best suited to lighter catamarans rather than 15t Leopards but I am happy with the performance and the crew are happy with the electric hob and oven and 24hr hot water

Respectable!


How much solar do you have?
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Old 09-01-2019, 12:27   #1811
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Re: Oceanvolt Hybrid Motor

trying the video again
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Old 09-01-2019, 16:30   #1812
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Re: Oceanvolt Hybrid Motor

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Originally Posted by svReality View Post
Managed to check regeneration whilst reaching at around 8.4-8.8knots. Was averaging about 1.2kw with fluctuations up and down. It was difficult to accurately determine what the loss in speed was with regeneration on and off as conditions were a bit choppy.

Overall I am happy that the OV does pretty much what i expected it to. It is best suited to lighter catamarans rather than 15t Leopards but I am happy with the performance and the crew are happy with the electric hob and oven and 24hr hot water
Nice! I'd love to see what you're getting at say 12 knots.

If you can shrink the video or get around whatever it is that's giving you grief that would be awesome.
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Old 10-01-2019, 06:17   #1813
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Re: Oceanvolt Hybrid Motor

Just to put this in perspective, regen @ 1.2kw for 10 hours produces 12kwh. Assuming that is stored in the battery, 12kwh is equivalent to about 3 liters of diesel.


Calc: a liter of diesel has ~10kwh of power, common rail ICE are up to 45% efficient. 3 liters of diesel = 30kwh * 40% = 12kwh.
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Old 11-01-2019, 03:14   #1814
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Re: Oceanvolt Hybrid Motor

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Originally Posted by svReality View Post
Managed to check regeneration whilst reaching at around 8.4-8.8knots. Was averaging about 1.2kw with fluctuations up and down. It was difficult to accurately determine what the loss in speed was with regeneration on and off as conditions were a bit choppy.

Overall I am happy that the OV does pretty much what i expected it to. It is best suited to lighter catamarans rather than 15t Leopards but I am happy with the performance and the crew are happy with the electric hob and oven and 24hr hot water

Wow that's quite impressive !
I forgot, is that with the "servoprop" or "normal" propellers ?
And maybe the best is to put the video on youtube.
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Old 11-01-2019, 12:15   #1815
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Re: Oceanvolt Hybrid Motor

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Just to put this in perspective
Perhaps you think that some too idealistically believe such a power source would be sufficient for "normal" usage patterns of propulsion energy?

I agree that is not realistic, we're not saying this is amazingly revolutionary; the use case for me is House loads, maybe contributing to reducing some small % of overall ("normal" level of) fossil fuel costs, on a similar sort of scale to solar and wind inputs.

But within that context, incrementally compared to existing real-world demonstrations, I'm pretty sure this is genuinely impressive?
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