Oceanvolt Hybrid Motor

[bridaus]

Originally Posted by Firstbait

I see this as bit heavy to fit on a catamaran

Me too. It's Siemen's. I was just responding to a comment, not trying to make a case for them.

[bridaus]

Originally Posted by saghost

Using the same 4:1 ratio on the engine I have a proper BMEP/bsfc map for, the MB does 206 g/kWh at ~15.5 bar and 2300 rpm. At 2300 rpm and ~4 bar, it's right on the 260 g/kWh line. I don't have the map for the 3YM30AE, but the results are likely similar.

Can you post that again? It's the best way to look at it. Might be the same one you posted before, for the small car diesel?

[saghost]

Originally Posted by bridaus

Can you post that again? It's the best way to look at it. Might be the same one you posted before, for the small car diesel?

It's just a link to wikicommons:

[bridaus]

Ok, decided to source one also, thanks for reposting that one.

See below. A fixed pitch prop is similar to one of the running lines. Never reaches most efficient regime, and even if you could make it pass through by increasing the gearing, you'd run out of headroom and have too much thrust at maneuvering speed.




Most published graphs will only show you the line chosen for the engine, not the whole BSFC map.

[44'cruisingcat]

Originally Posted by bridaus

In no particular order, and no evaluation of quality/suitability. Some of these could be junk. But definitely any size you could need in here, what are you looking for?

https://polarpower.com/marine-dc-generators/

https://www.fischerpanda.de/dc-marin...generators.htm

http://www.hamiltonferris.com/catego...C_Generators/9

https://www.altendc.com/

The Aussie one BigBeakie is using, can't recall the name....

They all seem to use marine diesels or Kubota, which are also ised as marine diesels.

Apparently they can't run at more than 50% rated power. Isn't that what you've been telling us?

[OldMan]

Originally Posted by saghost

What we have here is clearly a failure to communicate, so I'm going to try again, with pretty charts this time.

I did this with the Yanmar 3YM30AE, because it's a common choice for smaller cats and because I knew the data was available, but the results should be generally similar for most modern diesels.

Here's Yanmar's page for the engine, which includes a downloadable datasheet.

On that datasheet, they put three small charts, showing the power, torque, and fuel consumption:

Attachment 182063

Attachment 182064

Attachment 182065

On the power chart, it shows both a maximum line and a propeller curve for the typical fixed pitch single speed tuned to allow maximum power.

As you can see here, the propeller curve is nowhere near the peak efficiency area:

Attachment 182066

The engine should be at it's best making close to 15 kW at 1800 rpm (just off WOT at the torque peak.) But at that speed, the propellor curve means it can only produce 4 kW.

I'm not 100% certain how to translate the Autoprop's "adjusts to the best angle" into horsepower/torque behavior, but it kinda sounds like it holds a constant torque throughout the rev range. It' that's true, and if it was tuned to just hit the maximum power output, the result would be something like the green line - much better, but not perfect.

For the whole "fuel consumption varies by only 12% discussion, I'm thinking you're comparing the power output and fuel consumption curves they provided. Something like this:

Attachment 182067

This is an overlay of the two charts Yanmar gave us, with the 0 and RPMs matched and the fuel chart scaled slightly so the peak output matches.

The charts line up with just over 9 l per 25 kW. 9.1 l * 832 g/l /25 kW means where the lines cross the engine is using 302 g/kWh; the section from 2200 rpm to 3200 is a little below that, the section from 1400 to 2200 a little above.

So yes, along the propellor curve you only see a small variation in consumption for a single speed fixed pitch system. That's not because the engine is equally efficient at all points, though - it's just that you can't harness the areas that are much more efficient.

Using the same 4:1 ratio on the engine I have a proper BMEP/bsfc map for, the MB does 206 g/kWh at ~15.5 bar and 2300 rpm. At 2300 rpm and ~4 bar, it's right on the 260 g/kWh line. I don't have the map for the 3YM30AE, but the results are likely similar.

Thanks! That helps.


But.......actual fuel consumption will follow the power consumed by the prop (plus loss thru the gearbox), it won't use 15KW worth fuel with the prop only consuming 4KW.


Edit: Upon more thought, yes it will use 15KW worth of fuel for 4KW at the prop. But EP would have the same issue with the same prop.

[tp12]

Originally Posted by Dockhead

I hope you're right!


The best thing which could happen would be some terrific breakthrough in energy storage. We are addicted to diesel fuel only because of the incomparable energy density which diesel fuel has. If we could store electrical power at similar densities, even 5x worse than diesel fuel, this would open up immense horizons.

I'm definitely hoping that's the case!

Your other point, noted..

[cyan]

Originally Posted by bridaus

A nice explanation is Tesla forum post I linked, ICE engines throw away massive amounts of energy to supply large amounts. Something like 80%. Source: https://forums.tesla.com/forum/forum...sepower-rating. So a 1% savings here is 0.8% savings overall. Hmm, probably could do something with all that wasted energy especially at 3, 5, 30%...

Your math is not correct.
And.. that forum post does a nice middle school explanation of horsepower. That's cool, I think we agree that HP ratings are funky. I see that it causes confusion, but it doesn't change physics.
For that matter my last hybrid car had funky ratings too. There is literally no physical way a Ford C-Max can ever achieve 47 MPG. Subtract about 15%. Ford sent me a check each year as an apology. Their optimistic smoke and mirrors damaged their brand when there was no need to.

Originally Posted by bridaus

"Any sufficiently advanced technology is indistinguishable from magic." - Arthur C. Clarke.

Touche'.
Please let me know when Newton's laws are broken by your magic.
I have a motor that I wish to power from a generator that I wish to power from said motor.

Originally Posted by bridaus

You're being silly.

Guilty.
You got an engineer to play along with faulty physics.

Originally Posted by bridaus

If you knew Siemens like I do, you'd know why they miss the mark.

This is a G-rated forum.

[bridaus]

Originally Posted by 44'cruisingcat

They all seem to use marine diesels or Kubota, which are also ised as marine diesels.

Apparently they can't run at more than 50% rated power. Isn't that what you've been telling us?

You're kidding right?

[saghost]

Originally Posted by OldMan

Thanks! That helps.


But.......actual fuel consumption will follow the power consumed by the prop (plus loss thru the gearbox), it won't use 15KW worth fuel with the prop only consuming 4KW.


Edit: Upon more thought, yes it will use 15KW worth of fuel for 4KW at the prop. But EP would have the same issue with the same prop.

Yup. Your attachment is the other type of data set you often get from manufacturers, especially for automotive engines. The fuel consumption numbers they show are for full throttle at the various rpms, in accordance with the DIN test.

There are certainly big losses going from the driveshaft to motion in the water, but that's outside the scope of the discussion because we've been assuming equivalent fixed pitch propellors on both sides, so as you say the losses are similar for either case.

I wasn't trying to say it consumes 15 kW worth of fuel while only making 4 kW. It doesn't. But it does have exactly the same pumping losses, exactly the same effort to turn the crank and slide the pistons - and only a quarter of the power to spread that loss among, so it consumes about 30% more fuel *per unit of energy*.

That's still only about a third of the total amount of fuel per hour it would consume at 15 kW - but you're getting less work per drop of fuel because the engine isn't in the best part of the range.

One benefit of a hybrid (or of a variable pitch propellor or shifting gears) is that you can run the engine at or close to the peak more often. By bringing the battery into it, the hybrid can run at the 15 kW peak for every occasion when the sustained load is less than 15 kW, cycling the engine off when needed. (Of course, cycling power through the battery means paying ~5% in losses for all the power banked and used later. TANSTAAFL.)

[transmitterdan]

You guys know us Luddite mechanical boats use transmissions with gear ratios of 2:1 or thereabouts? And they are pretty darn efficient.

[bridaus]

Originally Posted by transmitterdan

You guys know us Luddite mechanical boats use transmissions with gear ratios of 2:1 or thereabouts? And they are pretty darn efficient.

3-15% in fact.

[tp12]

Originally Posted by tp12

Later on this evening I'll have some time to put together a basic use case, which the more learned people can add to, and that might help this thread stay on track and get everyone talking a common language?

I didn't get a chance to do this last night but started to do it earlier this morning. In doing so it seems I'm trying to achieve what bridaus is already doing with building his/her model.

bridaus, you're best placed to do this, in my opinion, are you able to clearly put your engines, motors, generators in terms of specs and perhaps start to build this system so we're all on the one page? Maybe it could be pasted into posts by those who are commenting on that model?

Just a thought that would help. I'll leave this now.

Cheers,

TP

[cyan]

Originally Posted by transmitterdan

You guys know us Luddite mechanical boats use transmissions with gear ratios of 2:1 or thereabouts? And they are pretty darn efficient.

Yeah, well the Oceanvolt SD15 uses a 1.93:1 gear ratio.
They might use something exotic though. Oil maybe?
Also, you Luddites might try to jam 30KW of power into that gearbox with your crazy affinity for WOT.
15 is roughly half of 30, so the EP gear loss is roughly half your gear loss.
Half a loss is better than a whole loss.
More efficient.
Pretty sure.

[OldMan]

Originally Posted by saghost

Yup. Your attachment is the other type of data set you often get from manufacturers, especially for automotive engines. The fuel consumption numbers they show are for full throttle at the various rpms, in accordance with the DIN test.

There are certainly big losses going from the driveshaft to motion in the water, but that's outside the scope of the discussion because we've been assuming equivalent fixed pitch propellors on both sides, so as you say the losses are similar for either case.

I wasn't trying to say it consumes 15 kW worth of fuel while only making 4 kW. It doesn't. But it does have exactly the same pumping losses, exactly the same effort to turn the crank and slide the pistons - and only a quarter of the power to spread that loss among, so it consumes about 30% more fuel *per unit of energy*.

That's still only about a third of the total amount of fuel per hour it would consume at 15 kW - but you're getting less work per drop of fuel because the engine isn't in the best part of the range.

One benefit of a hybrid (or of a variable pitch propellor or shifting gears) is that you can run the engine at or close to the peak more often. By bringing the battery into it, the hybrid can run at the 15 kW peak for every occasion when the sustained load is less than 15 kW, cycling the engine off when needed. (Of course, cycling power through the battery means paying ~5% in losses for all the power banked and used later. TANSTAAFL.)

The prop still presents the same load to the EP motor, hence the EP has to expend the same KW as a direct drive ICE.



There is more than 5% loss in ICE driven EP, 5-15% in the alternator plus 5% in the EP motor....batteries are additional 4% (? in/out). Minimum loss is 13%.