Oceanvolt Hybrid Motor

[john61ct]

Originally Posted by ssmoot

That's a sticking point. I haven't seen a LiFePO4 bank yet that's that small that has a ~3C rate.

Are you saying 1800A discharge is required? At what voltage?

> plan on firing up your generator before you could motor

That is acceptable if necessary, certainly can't motor now without prior ignition.

The bank has to be so huge per hour of motoring anyway. . .

> And you'd lose all the weight, volume, luxury benefits.

No idea what you mean, please explain. Comparing which scenarios?

> what I want is not more capacity. It's more fast chargers along travel routes.

I do not expect to connect to mains more than a couple overnights per year, if that. Certainly much more rarely than refilling fuel.

> I don't want to drive around with a battery I'll typically only use a few percent of.

Not planning on using battery at all for EP, just House loads

> But do you want to run your generator for 36 hours straight to charge it back up? If you're motoring for the day, better to be running your generator if the dead zone lasts for more than an hour or two.

Exactly my point.

Genset is also for high-gph watermaking and quickly charging large freezer holding plates.

> mega-batteries and carrying all that extra weight and losing all volume in your boat and wallet.

Yes exactly, but I do not understand your point, you seem to be contradicting yourself now ?

> Just get a peak 1C battery pack and call it a day.

I don't know what that means. I don't think I'll be going past .2-3C

[john61ct]

Originally Posted by bridaus

Time for fun!

Super, hope others join in! Especially accounting for those losses?

> 5.5 kt normal cruise at slightly less than 10hp (30% reserve = 3hp, but we'll do more).

Yes, seems small to me.The issues isn't actually gaining faster speed over ground, but maintaining some SOG progress powering against headwind, tides or current, maybe go to 100% reserve?

That speed in calm water could still be the fuel-efficient point though?

> Size the electric motor at 10kW (20-25hp equivalent)

> Size the DC genny at 5kW continuous (might require a 6kW to get cont. 5kW, oversized for normal cruise)

Note I don't want to depend on battery SoC for SHTF powering needs, so I guess genset needs to be matched to cover motor WOT.

Since I prefer not to run the genny much at anchor, in normal cruising usage would be nice to also get a fair bit of water made, eutectic plates frozen solid and House battery topped up, pretend the bank is hardly there for EP purposes.

So this

> 5.8kt conservatively as long you have fuel, and 7.0kts conservative for 30 minutes (based on size of your bank).

changes to "near hull speed is possible as long you have fuel", remember heavy monohull, likely full keel

> 600ah *12v (assumed) = 7.2kWh

24V would be fine if it gains anything?

[Dockhead]

Originally Posted by ssmoot

I definitely missed that.



Agreed. It feels like with the right math this could all be put to bed and everyone could walk away happy feeling like they've learned something.



I think there's potential to do the same as cars. Use a (typically smaller) engine that operates at peak efficiency, overcoming conversion losses compared to using a bigger direct-drive engine inefficiently. Make it just big enough to provide for typical power requirements plus some margin to slowly charge the battery.

But I'd also agree that the overall efficiency advantage is probably very small (under 10% I'd guess) and there'd probably be bigger gains from manufacturers just building better, more modern engines.

If you're going to use electric motors anyways it's a nice to have.

My only issue with the efficiency topic is the unsupported claim that overall efficiency would go down when that flies in the face of all available evidence.



Agreed. There are a lot of reasons to prefer EP I think. Efficiency is way down the list. I just don't think there's any evidence to move it into the "Cons" column.

In fact, I can think of only two Cons (though I'd love to hear more):

1. Repower/Upgrade Cost
2. Redundancy

Maybe someday I'll find a Seawind 1260 that needs a repower at a steep discount.

OK, so it looks like everyone agrees that efficiency is not the most important factor. I agree with this as well -- weight and capital cost are surely much more important to most people than +/- 10% of fuel efficiency, and especially to catamaran sailors.




But I wouldn't let go this discussion about efficiency, as I don't think we've gotten to the bottom of it. The interesting paper which Big Beakie posted in Post 1665 shows a big ship diesel electric system with 10% conversion losses. This is based on multimillion dollar plant with 97% efficient generators and 96% efficient synchronous motors. Even with this multi million dollar plant, you are starting off around 7% behind direct drive through one set of gears. And this level of efficiency is not available in our smaller plants -- even my friend's 200 foot expedition vessel couldn't get more than 82% efficiency of the diesel-electric drive according to the engineering study he had done. Our generators and motors are less efficient than this, so we start out more than 7% behind direct drive.


No one has answered the question which I posed above -- what makes you think that you can operate a hybrid always at "peak efficiency" of the diesel? You can have a better propeller curve with hybrid than a dumb fixed prop driven mechanically, but "better" is not "perfect", and I doubt it will be significantly better than the propeller curve of a mechanically driven variable pitch prop.


And anyway you will never have "peak efficiency" all the time in a real life boat which needs varying amounts of power. You can theorize about one particular speed in one particular set of weather, wind and sea conditions, but real life is very different -- you operate at different speeds, with the wind, against the wind, head seas, flat water -- you have to vary power, as you do that, you get into different parts of the engine fuel map.



Big Beakie is already saying that the efficiency question is a "wash" -- that's progress compared to the magical "peak efficiency all the time more than making up for conversion losses", and maybe in some cases it could be a wash when comparing to mechanically driven fixed pitch props -- but mechanical drive with a variable pitch prop is going to be much more efficient than hybrid. Because you can get right into the fuel map sweet spot without any conversion losses, with a variable pitch prop.





Others continue arguing on the one hand that car hybrids are irrelevant to the discussion, then keep bringing them up. Note that the Prius (and I believe the Chevy ones too) LOCK the drive in constant speed highway situations, to mechanically drive the car.




OK, but all that being said -- I do agree with others who have said that modest differences in efficiency are not the main thing anyway. If we could downsize the engine a lot, using battery power for short term high power requirements, such that the whole plant is significantly lighter, then this would be a good argument for hybrid in my opinion, even if it were somewhat less efficient. This might be achievable on a cat if you can eliminate a whole diesel engine. Probably not on a mono considering the added weight of generator and motor.


Diesel engines are so reliable, that redundancy is probably not a paramount value for most people. ALL mono sailors live with non-redundant prime movers. I'd like to see a hybrid cat with one diesel engine. That might have some very significant advantages.




P.S. -- to put my money where my mouth is, about efficiency --


I am designing my next boat, a metal boat of about 65' designed for high latitudes. Naturally, it will have a variable pitch prop -- I have been using ONLY variable pitch props since the 90's. In this case, a Hundestedt manually variable prop.


But the main reason for me of variable pitch props is not the 10% or so of fuel savings -- it's noise, engine wear, and especially, motor-sailing. With a variable pitch prop you can operate, especially under low load conditions, with the engine running much slower and more quietly but loaded up nicely for its good health.


I am going to significantly oversize my main engine -- about 200 horsepower for a 25 to 28 tonne boat. with fuel tankage of 1.5 tonnes or so. That will cost me some efficiency, but it's worth it to be able to power out of various high latitude situations which arise, and to simply motor into a strong wind if necessary -- if you get too tired to keep fighting the wind under sail. I will use a high pressure turbocharged/intercooled engine and possibly a common rail one. I will burn quite a bit more fuel than I do in my present boat (20 tonnes light ship, 100 hp), but efficiency is not everything. If it were, we wouldn't sail at all!

[Dockhead]

Originally Posted by john61ct

.. .

24V would be fine if it gains anything?

I think you want at least 48v for propulsion, don't you?

[bridaus]

Originally Posted by Dockhead

I think you want at least 48v for propulsion, don't you?

Yes IMO. For reasons mostly not related to the discussion.

[BigBeakie]

Re efficiency, I think it is important to not discount the role of alternative energy sources that will contribute to the propulsion over the total time the boat is used. From my calcs, for our use case and intended tropical cruising grounds, we expect our 4.2kW solar and the Servoprop regen to contribute very significantly to the overall propulsion time. Both will recharge the propulsion bank, and then for all motoring under about 3 hours, the batts will do their thing, without any genset run time.

The exception case when the DC genset will run for extended periods will be when becalmed even below what the screecher can help with. How much of our total motoring time will therefore be on the ICE? Dunno yet, but I'm thinking probably not over 20%?

The point is, so what if the serial hybrid is not quite as efficient as the diesel propulsion? The proportion of time we're using the genset is low, whereas the proportion for the diesel only boat is 100%. If we take efficiency to be the amount of diesel consumed divided by the total miles under ICE, which one do you think would return the lower diesel consumption per mile motored?

You have to take EP as the whole system to comprehend the benefits and TCO, not just focus on diesel use efficiency as the Holy Grail, that it isn't.


Sent from my iPad using Cruisers Sailing Forum

[Dockhead]

Originally Posted by BigBeakie

Re efficiency, I think it is important to not discount the role of alternative energy sources that will contribute to the propulsion over the total time the boat is used. From my calcs, for our use case and intended tropical cruising grounds, we expect our 4.2kW solar and the Servoprop regen to contribute very significantly to the overall propulsion time. Both will recharge the propulsion bank, and then for all motoring under about 3 hours, the batts will do their thing, without any genset run time.

The exception case when the DC genset will run for extended periods will be when becalmed even below what the screecher can help with. How much of our total motoring time will therefore be on the ICE? Dunno yet, but I'm thinking probably not over 20%?

The point is, so what if the serial hybrid is not quite as efficient as the diesel propulsion? The proportion of time we're using the genset is low, whereas the proportion for the diesel only boat is 100%. If we take efficiency to be the amount of diesel consumed divided by the total miles under ICE, which one do you think would return the lower diesel consumption per mile motored?

You have to take EP as the whole system to comprehend the benefits and TCO, not just focus on diesel use efficiency as the Holy Grail, that it isn't.


Sent from my iPad using Cruisers Sailing Forum

I entirely agree with all of this.


I've said before -- if you can get significant amounts of non-internal combustion power into the system, that changes everything. I'm skeptical about regeneration as a major source of power, and storage is a big issue in any case, but for someone who can plug in every night, I think there's no doubt that hybrid makes sense.


Yet another thing to think about is engine hours. Fuel is only about half the cost of motoring -- by my calculation, for my own boat, at least, and once you include amortization of the cost of the main engine. If you can significantly reduce engine hours, you will save significant money, and there are a couple of different scenarios where hybrid could do that. Again, however, limited by storage.


Big Beakie sails all the time and uses his engine as a true auxiliary. That's not true for most of us. Most of us motor more than 50% of our miles. I motored for four days and nights straight in a dead calm in the Arctic Ocean last summer, and often motor for days on end in different situations. So wearing out the main engine is a significant concern for some of us.

[john61ct]

Yes my comments about alternative energy being insignificant were for my use case. A fast boat that can fit 4+kW of panels, completely different, makes a big bank worthwhile.

[john61ct]

Originally Posted by Dockhead

I think you want at least 48v for propulsion, don't you?

I dunno, but yes I was surprised by the 12V "assumption".

But that's fine, needs must.

I was just researching power supplies, sorry if OT, came across a reco for HP's ESP120 used for their data centre rack servers

if genny or mains is 220-240 output, designed to produce 51.4V at up to 57A, ~3kW continuously 24/7, built like a tank, very smart, fully regulated

also put out 5V, easy to convert to 12V

batches regularly show up on eBay for $30-50 @ including shipping

[OldMan]

Originally Posted by BigBeakie

Re efficiency, I think it is important to not discount the role of alternative energy sources that will contribute to the propulsion over the total time the boat is used. From my calcs, for our use case and intended tropical cruising grounds, we expect our 4.2kW solar and the Servoprop regen to contribute very significantly to the overall propulsion time. Both will recharge the propulsion bank, and then for all motoring under about 3 hours, the batts will do their thing, without any genset run time.

The exception case when the DC genset will run for extended periods will be when becalmed even below what the screecher can help with. How much of our total motoring time will therefore be on the ICE? Dunno yet, but I'm thinking probably not over 20%?

The point is, so what if the serial hybrid is not quite as efficient as the diesel propulsion? The proportion of time we're using the genset is low, whereas the proportion for the diesel only boat is 100%. If we take efficiency to be the amount of diesel consumed divided by the total miles under ICE, which one do you think would return the lower diesel consumption per mile motored?

You have to take EP as the whole system to comprehend the benefits and TCO, not just focus on diesel use efficiency as the Holy Grail, that it isn't.


Sent from my iPad using Cruisers Sailing Forum

Yes, there are benefits you mention. But, the holy grail of diesel usage is from the long passages. You have to look at it from the percentage of fuel burn, not time. Putzing in/out of anchorage or to/from a marina even at low in-efficient rpm is so small of a percentage of overall fuel burn, it's insignificant.

[john61ct]

For some owners. For others that's all they use power for.

Some make do with oars

[bridaus]

Originally Posted by ssmoot

I was using 20kW motor as the baseline. Your 10kW number may be more realistic.

I'm not assuming that. C-rate doesn't depend on SoC. If you don't have enough C-rate to meet your discharge requirements you need to run the generator or risk damaging the pack.

Totally agree. The best thing about an EV is never visiting a gas station (and the performance, and the TCO, and... well, you get the idea ). And even though I have no reason to feel anxious, I rarely let mine go lower than 50% SoC. I couldn't imagine owning an EP boat and not keeping the pack around 80% as a general rule. Maybe if I felt like running the air-conditioning I'd plan to let it get down to around 40% by morning, but I'd still check the forecast before going to bed.

My pack lives between 50% and 90% pretty much all the time. I've only had it down to ~10% once, when I calculated I could skip the last charge station on a road trip back home and still have ~15 miles in reserve. I can't imagine that being any different on a boat. Force of habit I guess.

In a perfect world I'd have digital switching and just turn on the generator automatically once SoC hit 40% and stop it at 80% (for battery longevity and charge efficiency). And automatically turn off power to all non-essential devices besides propulsion if power ever hit 30%. In fact, if I could figure out a way to pack in 3kW of solar, I'd probably just skip the diesel generator entirely and carry a pair of parallel gas generators for peace of mind.

I treat my battery SoC exactly like I treated my gas tanks. Fill it any opportunity less than half and empty it any time more than half. When storms are coming, fill 'em to full and sit back and wait for a reason to book it. Electricity is just another form of energy with different but understandable rules.

Digital switching? A perfect world is not required, just a switch to tell the generator to run and not run when the loads will be in the spot you want. Pretty sure that's not hard to figure out (bank < 50% SoC OR load on bus 95% or whatever you want and up!).

Nirvana is when solar + storage is efficient enough to keep up with demands. I'm not sure it will ever get there for the folks always on the move, but for those who stay places a couple of days, or when batteries get reasonable per kWh, we are styling. I'm betting on this, but not everyone has to...

[OldMan]

Originally Posted by BigBeakie

Nice to see some analysis on EP Hybrid vs DD by both sides. At the end of the day, this is a topic that can be resolved, because it comes down to demonstrable facts, not agenda driven opinions.

Just wanted to point out and share the DC genset efficiency re fuel useage mistake I was making, and that has been corrected by the head engineer of Eniquest who makes our DC genset.

The engine charts for Yanmar fuel used vs RPM ( and probably all other marine diesels for the common sizes for sailboats) is only applicable for direct propulsion use, not when used as the power plant for gensets.

So for our DC genset we take the given fuel use per kWh power produced times the kW produced as output, which is 260 grams diesel per kWh produced, divided by the efficiency of the alternator, which in our case is 93% to give the total fuel used in grams per kWh. Then to convert to liters per hour AT THAT POWER OUTPUT divide by specific gravity of the diesel or 830.

So our 16kW DC genset from Eniquest produces 15kW so:

(260g/kWh x 15kW) divided by .93 = 4194 grams of diesel. Divided by 830 = 5.05 liters per hour to produce 15kW.

At half power producing 7.5kW we'd use 2.5 liter per hour of diesel.

When I compared that to the designers recommended Yanmar engine for the same boat, the 4JH5E Series, I see that that at the cruising rpm for that engine (2250) to give the same boatspeed as the Servoprop 15kW, the kW output is about the same and fuel useage is about the same.
So, it's a wash on direct drive diesel vs electric hybrid as far as I can see.

My conclusion way back then when I worked through this with the help of a marine engineer experienced in sizing engines for sailboats, as it is now, is that the cruising speed performance is about the same between the two options, ie the 15kW Oceanvolt Servoprop and the Yanmar 54HP (40kW).

The Yanmar 4JH5E will give a higher top speed by about a knot to 1.5 knots on the same boat when its at WOT.

Nothing I have seen or heard, whether on this forum, or otherwise, has changed what I saw way back then, and when I posted that you need a diesel approximately 2 to 3 times larger than the OV 15kW to get the same cruising speed. And it seems, some other OV users are reporting the same conclusion on this forum.

Here is a paper on the benefits and system considerations for the rationale for electric hybrid. Note that it is from a marine diesel manufacturer, Man Diesel.

About = 19%!

The 4JH5E @ 2250rpm provides 17KW to the prop. Input of 15KW to the Oceanvolt Servoprop provides 14.25KW to the prop. The 4JH5E will burn less than 5L/hr at this output.

Assume like props, the direct drive will burn less fuel and provide 19% more power to the prop than the OV.

https://www.yanmarmarine.com/theme/y...heet_4JH5E.pdf

[OldMan]

Originally Posted by john61ct

For some owners. For others that's all they use power for.

Some make do with oars

At that point, the ROI on the upcharge to EP goes way out of whack! You could hire a tug to pull your boat to the next destination and still save $$ over a 10 year period.

[bridaus]

Originally Posted by john61ct

Super, hope others join in! Especially accounting for those losses?

> 5.5 kt normal cruise at slightly less than 10hp (30% reserve = 3hp, but we'll do more).

Yes, seems small to me.The issues isn't actually gaining faster speed over ground, but maintaining some SOG progress powering against headwind, tides or current, maybe go to 100% reserve?

That speed in calm water could still be the fuel-efficient point though?

> Size the electric motor at 10kW (20-25hp equivalent)

> Size the DC genny at 5kW continuous (might require a 6kW to get cont. 5kW, oversized for normal cruise)

Note I don't want to depend on battery SoC for SHTF powering needs, so I guess genset needs to be matched to cover motor WOT.

Since I prefer not to run the genny much at anchor, in normal cruising usage would be nice to also get a fair bit of water made, eutectic plates frozen solid and House battery topped up, pretend the bank is hardly there for EP purposes.

So this

> 5.8kt conservatively as long you have fuel, and 7.0kts conservative for 30 minutes (based on size of your bank).

changes to "near hull speed is possible as long you have fuel", remember heavy monohull, likely full keel

Ok, reserve at 100% and continuous. We don't have to resize the electric motor (it was already oversized).

Generator has to resize to push WOT continuous. House bank won't be counted on anymore, which I think is a shame because it's a nice "there when you need it" for a statistically low percentage of the time you actually need it and allows you to save some capex. I wouldn't design it this way, but it is YOUR boat not mine. Sooo, genny at 10kW, which might require an 11/12kW unit.

Your speeds don't change, but now you can do 7.0kts until the diesel runs out instead of for 30 minutes. Overkill? That's your call, your money.


Polar says 290g/kWh which should be 1.7 liters per hour (call it 2.0 until I see real life data) and WOT is 3.4 lph (call it 4 for same reason).


I'm going to write a different post for efficiency losses. I do not believe they are large, or wildly greater or less than DD therefore could be ignored for the purpose of the overall thread, but should not be ignored in your design if you got serious about it. It's your ROI, your money....