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Old 12-12-2018, 12:06   #1576
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
I don't see data for your 11%, I could be missing the post, this thread is large.

RE: 15% battery loss, also no data found. When cruising at planned cruise given input power, battery loss is effectively zero. Even if our power needs are off a little bit, loss still very small with slow rate of charge/discharge. Pushing lots of current in or out of bank (really only when exceeding generator power by a lot) there is a definite effect, but now battery chemistry and charge rates/bank sizes/etc. have to be discussed. Are we ready for that yet? No one has answered me on how to calculate the amount of reserve power needed, so I'm not sure we're ready.

Just on sfc alone there's a possibility (depending on engine/etc.) of 30%. I don't have enough data to put this all together yet, but just with that one number I think EP could be more efficient. If done right. Who knows if OV, Elco, others have done it right yet, but I think so there are happy customers.

The loudest proponents of EP here on CF donít have EP....yet. The one or two that do have EP report results pretty much the same as direct mechanical. They are happy but they ainít saving 30% on fuel. And they spent probably 100% more in capital cost.

You need to get your numbers straight. Diesel engines donít have a huge range in fuel consumption per kWh produced like you believe. The range is pretty narrow and no where near 3:1. You can get confused by looking at fuel consumption per RPM. But the main thing that governs fuel consumption in a diesel is power extracted at the crank not RPM.
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Old 12-12-2018, 12:11   #1577
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
The one thing for sure, there are a lot of smart people betting their livelihood on this. They may be wrong, but there is something causing them to bet big. It's not smoke and mirrors when engineers are involved.
You'll also find several engineers in this forum, of all flavors. While few of us are directly [SIC] involved in marine electric propulsion, almost all of us can understand efficiency tradeoffs.

The efficiency debate here has run afoul because people are mixing in real hybrid advantages with make-believe EP efficiencies. The EP better-efficiency argument simply CANNOT be won without including extra hybrid benefits such as regeneration. You simply will not get a more efficient power train by adding components to it that lose heat. There is no free lunch. Trying to beat Newton has every engineer's eyes rolling here.

Now. If we can finally put that nonsense to bed, we could get to the real potential efficiency bonuses, not the imaginary ones:
1. Start-stop savings.
Yes, of course this is an EP advantage. This would be awesome for that weird guy in San Pedro who motors his sailboat around tight quarters all day as part of the Coast Guard Auxiliary. Hell, he could recharge every night from shore power. Cool.
This is trivial to me as a cruiser, as start-stop activity represents less than 0.1% of my diesel engine usage. Doldrums seem to last a while and I'm not on shore power much at all.
2. Regeneration
This is promising. What is the best case? Maybe 1000W coming in with two 15KW OV drives and a beam reach all day, providing an extra hour of motoring when the wind dies? Good stuff.
3. Solar and wind
Using such sources for propulsion is an advantage. How much? We receive more than 1200W per sq meter in the tropics during the middle of the day, but can only collect close to 20% of that. The world record experimental technology is currently pushing 50%. Unfortunately, I would need much more surface area than is practical to help much with EP propulsion. My friends in higher latitudes are simply out of luck here.
Wind? Yeah, that adds a bit too. More than a couple hundred watts would be a big windmill beast, though.

It all adds up, and it all gets better as technology advances. Personally, I'm interested in EP advantages that do NOT involve efficiency. I hate the SOUND of my diesel. To put a genset into a 6-walled insulated/isolated box somewhere away from the aft cabin is almost worth the price of admission for me.
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Old 12-12-2018, 12:24   #1578
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Re: Oceanvolt Hybrid Motor

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You need to get your numbers straight. Diesel engines don’t have a huge range in fuel consumption per kWh produced like you believe. The range is pretty narrow and no where near 3:1. You can get confused by looking at fuel consumption per RPM. But the main thing that governs fuel consumption in a diesel is power extracted at the crank not RPM.
Please review graph of sfc. The sfc chosen for coupled diesel engine is high because you have to run it from idle to wot because it's acting as your transmission. You cannot choose to run it at one RPM and load like a generator.

I do agree it's not three to one though, the one graph I saw/reposted showed about 30% (260 at best versus 206 at best).

I also agree that if you just add electric in between an engine and prop, you are only adding inefficiency, unless you find efficiency elsewhere, like in your engine loading! There's no point in adding extra steps unless it allows you to gain elsewhere! Isn't that obvious?
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Old 12-12-2018, 12:30   #1579
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Re: Oceanvolt Hybrid Motor

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We should probably not talk variable pitch, that confuses the situation more. Both can use it, both can benefit but it adds a layer of complexity I don't think we want to try to address. I used to have the math skills for it, but not so much anymore. If someone here is an engineer that works with props, open to the real math, but otherwise we should stick to fixed pitch for our apples to apples comparison.
Then pick a fixed-pitch prop for the diesel direct-drive in which the prop power curve meets the shaft power curve at the EFFICIENT ENGINE RPM of the engine which can be used for cruising long term. You have been comparing systems with the typical prop match, at the MAXIMUM ENGINE RPM.
(note, this is not typically done, because it would mean you could never utilize maximum engine power)
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Old 12-12-2018, 12:34   #1580
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Re: Oceanvolt Hybrid Motor

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The efficiency debate here has run afoul because people are mixing in real hybrid advantages with make-believe EP efficiencies. The EP better-efficiency argument simply CANNOT be won without including extra hybrid benefits such as regeneration. You simply will not get a more efficient power train by adding components to it that lose heat. There is no free lunch. Trying to beat Newton has every engineer's eyes rolling here.
No one is saying "adding components" to an existing power-train. No one. The statement is a distortion of the discussion (accidental or otherwise).
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Old 12-12-2018, 12:40   #1581
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Re: Oceanvolt Hybrid Motor

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Then pick a fixed-pitch prop for the diesel direct-drive in which the prop power curve meets the shaft power curve at the EFFICIENT ENGINE RPM of the engine which can be used for cruising long term. You have been comparing systems with the typical prop match, at the MAXIMUM ENGINE RPM.
(note, this is not typically done, because it would mean you could never utilize maximum engine power)
Agree in part, it's a theoretically better target if efficiency is the only goal.

There are problems though:
  1. sfc still too high for all but this specific RPM. Still using engine as transmission. But at least most of your miles would be at best efficiency.
  2. Too much thrust for maneuvering (I admit I'm not a prop expert, but if we are gearing for lower top end then extra acceleration should result at bottom).
  3. As you mention, can't use HP you purchased.
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Old 12-12-2018, 13:19   #1582
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
Little Honda's (AC generators) are not what we are talking about in this thread, we are talking about DC generators specifically designed for propulsion.
Does anyone make one, in the sizes we're talking about? From what I've seen, the hybrid systems in sailboats have used generators that aren't specifically designed for propulsion.
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Old 12-12-2018, 13:30   #1583
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Re: Oceanvolt Hybrid Motor

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....
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Old 12-12-2018, 13:35   #1584
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
Agree in part, it's a theoretically better target if efficiency is the only goal.

There are problems though:
  1. sfc still too high for all but this specific RPM. Still using engine as transmission. But at least most of your miles would be at best efficiency.
  2. Too much thrust for maneuvering (I admit I'm not a prop expert, but if we are gearing for lower top end then extra acceleration should result at bottom).
  3. As you mention, can't use HP you purchased.

The SFC for my engine shows a fuel consumption (g/kW-h) spread of 12% from 1400rpm to 3600rpm. From 2000rpm to 3600rpm the spread is 2%.


In the total fuel consumed on my boat, what percentage do you believe is consumed at 1400-1800rpm? The answer is somewhere in the decimal points to the right of 0%.



This argument is a fools errand.
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Old 12-12-2018, 13:46   #1585
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Re: Oceanvolt Hybrid Motor

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The SFC for my engine shows a fuel consumption (g/kW-h) spread of 12% from 1400rpm to 3600rpm. From 2000rpm to 3600rpm the spread is 2%.

In the total fuel consumed on my boat, what percentage do you believe is consumed at 1400-1800rpm? The answer is somewhere in the decimal points to the right of 0%.

This argument is a fools errand.
I asked you what your engine was, no answer. Do you have the graph? If it's a straight line, you are reading it wrong. Look at the sfc graph I reposted. See the circle at the top? Your engine is never reaching that.

You are probably looking at a single line graph. It doesn't tell the whole story.

Please post what you are looking at so we can get on the same page.
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Old 12-12-2018, 13:57   #1586
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Re: Oceanvolt Hybrid Motor

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No one is saying "adding components" to an existing power-train. No one. The statement is a distortion of the discussion (accidental or otherwise).
You start with a diesel engine, a shaft, and a prop.
You add a generator, an inverter, an electric motor.
You did change the engine model and location and you changed the prop.
Why are you confused by this?

Simple physics tells us that the components you indeed ADDED to the conventional propulsion system will generate heat. Each stage of heat loss subtracts from the original efficiency. To compensate for these losses, you run your new diesel genset in a more efficient manner than in the original direct drive system. Well done. You have made up for SOME of the losses. Not all.

If you think that you have significantly surpassed the direct-drive efficiency while using the identical fossil fuel, then you are distorting the direct-drive efficiency for your own purpose.
Carry on, if it's fun.
There are some perpetual motion machine claims that are fun too.
Personally, I like the ones with permanent magnets.

FYI, a company called Siemens has been designing and refining EP systems for decades. They have scaled down some of their (expensive) systems to yacht size, and they proudly declare that they are almost as efficient as direct drive.
I applaud OceanVolt for bringing their innovations to this market, with even smaller applications. Their approach, including regeneration, looks very promising. Real world results are coming, no doubt.
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Old 12-12-2018, 14:19   #1587
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Re: Oceanvolt Hybrid Motor

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Originally Posted by cyan View Post
You start with a diesel engine, a shaft, and a prop.
You add a generator, an inverter, an electric motor.
You did change the engine model and location and you changed the prop.
Why are you confused by this?
Ok, that's not what you had said, but that's ok, we're mostly on the same page now. Maybe I read you wrong.

Don't forget you also change the ICE RPM, load, and duty cycle, remove a gearbox, add a buffer for reserve power (which can allow you to decrease gen size OR increase top speed) and increase your capital outlay (at the moment). I probably forgot something, it's not just a simple swap is my point.

Quote:
Originally Posted by cyan View Post
Simple physics tells us that the components you indeed ADDED to the conventional propulsion system will generate heat. Each stage of heat loss subtracts from the original efficiency. To compensate for these losses, you run your new diesel genset in a more efficient manner than in the original direct drive system. Well done. You have made up for SOME of the losses. Not all.
This is where we diverge. 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%...

Quote:
Originally Posted by cyan View Post
If you think that you have significantly surpassed the direct-drive efficiency while using the identical fossil fuel, then you are distorting the direct-drive efficiency for your own purpose.
Carry on, if it's fun.
There are some perpetual motion machine claims that are fun too.
Personally, I like the ones with permanent magnets.
You're being silly. My silly response: "Any sufficiently advanced technology is indistinguishable from magic." - Arthur C. Clarke.

Quote:
Originally Posted by cyan View Post
FYI, a company called Siemens has been designing and refining EP systems for decades. They have scaled down some of their (expensive) systems to yacht size, and they proudly declare that they are almost as efficient as direct drive.
If you knew Siemens like I do, you'd know why they miss the mark.
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Old 12-12-2018, 14:25   #1588
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Re: Oceanvolt Hybrid Motor

Turns out I might have been wrong. Maybe they have hit the mark?

https://www.siemens.com/innovation/e...hing-boat.html
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Old 12-12-2018, 14:45   #1589
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Re: Oceanvolt Hybrid Motor

I see this as bit heavy to fit on a catamaran
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Old 12-12-2018, 14:49   #1590
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Re: Oceanvolt Hybrid Motor

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The SFC for my engine shows a fuel consumption (g/kW-h) spread of 12% from 1400rpm to 3600rpm. From 2000rpm to 3600rpm the spread is 2%.


In the total fuel consumed on my boat, what percentage do you believe is consumed at 1400-1800rpm? The answer is somewhere in the decimal points to the right of 0%.



This argument is a fools errand.
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:

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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:

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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:

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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.

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