Oceanvolt Hybrid Motor

[bridaus]

Someone brought up reserve power which is a valid design input. There is no reason that one cannot choose to have reserve power with EP or ICE, the point with EP is that you are not forced to buy it like with ICE ratings.

My question about this factor is how much is enough? How do you calculate how much reserve power is needed? Average storm size, with average angle of intercept and angle of egress with resultant percent of extra speed needed to escape? Use this to calculate the HP needed plus a safety factor to get out of the path? Don't forget to take into account how long it takes to qualify as "safe", whatever that is.

To me, reserve really is asking how much money do you have to waste on fuel and engine to be able to say you can achieve a speed you'll only use once just to see it. "Nice to have" is not quantifiable, it'd be nice to have a bigger boat too, and sizing one for reserve is actually an easier task. To prove me wrong, someone find me a formula that tells me how much "reserve" is needed to avoid a storm. Please be precise, our lives matter.... /s

It was also mentioned that electric propulsion mfg's do not spec like ICE mfg's, that's simply because the products they use (an electric motor) have been spec'ed by engineers for years. The marketing hasn't fully reached them yet because consumers have largely not been involved in their purchase. However at least one mfg does in fact have a continuous and peak published (Elco).

I do think some of the electric folks are underpowering a bit for my taste, but it's because they can, there are no warranties to invalidate choosing too small of an engine.

[transmitterdan]

Regardless of the "rating" provided by a manufacturer the fuel consumption is the same for a given engine, RPM and torque. It seems someone is trying to fog the glass a bit on the HP rating of a particular manufacturer. A HP rating is subjective. Fuel consumption/efficiency is quantitative. I await an EP vendor that proves their "equivalent HP" hybrid system is more efficient than plain ICE + gear drive. By "equivalent" I mean a hybrid system that can motor for 96 hours or longer at near hull speed into waves powered by a diesel genset. Almost any diesel/gear system can do that regardless of the HP rating scheme. As far as I can tell no EP system can do it while burning less fuel than a pure mechanical drive system.

[bridaus]

Originally Posted by transmitterdan

Regardless of the "rating" provided by a manufacturer the fuel consumption is the same for a given engine, RPM and torque. It seems someone is trying to fog the glass a bit on the HP rating of a particular manufacturer. A HP rating is subjective. Fuel consumption/efficiency is quantitative. I await an EP vendor that proves their "equivalent HP" hybrid system is more efficient than plain ICE + gear drive. By "equivalent" I mean a hybrid system that can motor for 96 hours or longer at near hull speed into waves powered by a diesel genset. Almost any diesel/gear system can do that regardless of the HP rating scheme. As far as I can tell no EP system can do it while burning less fuel than a pure mechanical drive system.

You are largely addressing the efficiency part of this discussion.

No fogging here. HP itself is very scientific, not subjective. The problem is rated maximum and the tricks/stipulations/conditions/exceptions used to achieve it. That's fog.

I am also interested in an EP vendor demonstrating the same, but even if it's not quite there yet, it's coming, and the mix of "free" (not free, because it ultimately comes from fusion) energy tips the scales in some implementations. I think based on some calculations and timing that the time is now.

BTW, one thing we largely haven't addressed? These hybrid systems are expensive today. If I were buying now, even though I believe strongly in electric it would still be tough to lay out all the extra cash. However, knowing how inexpensive the components are, it's just a matter of time for this to become incredibly cost competitive. It's all profit taking, and paying off development costs at the moment.

[john61ct]

The market is driven by those with plenty money wanting to look Green, or maybe fooled into thinking EP actually is green.

The only way it is,

solar being a significant source, and

safety + schedule-convenience accounted for,

is when the whole design from the hull up is designed for that.

[bridaus]

Originally Posted by john61ct

The market is driven by those with plenty money wanting to look Green, or maybe fooled into thinking EP actually is green.

The only way it is,

solar being a significant source, and

safety + schedule-convenience accounted for,

is when the whole design from the hull up is designed for that.

EP is a tool enabling green behavior. Depends on how you use/feed it. There is no other choice except sails.

[OldMan]

Originally Posted by transmitterdan

Regardless of the "rating" provided by a manufacturer the fuel consumption is the same for a given engine, RPM and torque. It seems someone is trying to fog the glass a bit on the HP rating of a particular manufacturer. A HP rating is subjective. Fuel consumption/efficiency is quantitative. I await an EP vendor that proves their "equivalent HP" hybrid system is more efficient than plain ICE + gear drive. By "equivalent" I mean a hybrid system that can motor for 96 hours or longer at near hull speed into waves powered by a diesel genset. Almost any diesel/gear system can do that regardless of the HP rating scheme. As far as I can tell no EP system can do it while burning less fuel than a pure mechanical drive system.

Exactly!

In my very poor attempt to illustrate the loss in a hybrid/EP system, I wasn't very clear.

In a cursory look, industry-wide, alternators on gensets have efficiency ratings around 85% - 95%. OV and other EP vendors claim 95% efficiency on their motors.

My earlier swag using a 1KW loss in a 15KW alternator (93% efficient) falls inline with the above numbers. Add to that a 750W loss in the 15KW EP motor and you now have a ICE putting out 16KW so the alternator can deliver 15KW to the EP. The EP then delivers 14.25KW to the drive train. This does not take into account any loss in cabling/controllers/etc.

The bottom line - if you connect the same ICE to the same drive train it only needs to produce 14.25KW to be equal, an 11% drop in load.

[bridaus]

Originally Posted by OldMan

The bottom line - if you connect the same ICE to the same drive train it only needs to produce 14.25KW to be equal, an 11% drop in load.

This is exactly the kind of math I'm working on, but poorly and in my spare time. The key is good attributable input data.

Don't forget the gearbox. 3-15% loss according to Gerr.

Also don't forget duty cycle. One gets to hum at any speed/efficiency we want, one has to go from idle to WOT and back again varying amounts. I find this is the hardest number to calculate.

Edit:

1. Where do you get 93%? I'm looking for sources for my own calculations.
2. Where do you get 750W loss? Same reason, just need to add to my dataset. Thanks!

[saghost]

Originally Posted by transmitterdan

Regardless of the "rating" provided by a manufacturer the fuel consumption is the same for a given engine, RPM and torque. It seems someone is trying to fog the glass a bit on the HP rating of a particular manufacturer. A HP rating is subjective. Fuel consumption/efficiency is quantitative. I await an EP vendor that proves their "equivalent HP" hybrid system is more efficient than plain ICE + gear drive. By "equivalent" I mean a hybrid system that can motor for 96 hours or longer at near hull speed into waves powered by a diesel genset. Almost any diesel/gear system can do that regardless of the HP rating scheme. As far as I can tell no EP system can do it while burning less fuel than a pure mechanical drive system.

If you want to have an efficiency discussion, you'll want to be very careful about defining the conditions for it, because they make a big difference.

Is hull speed the way you normally operate? The impression I'd gotten from readying is that a lot of cruisers motor slower than that, for better economy - cats running a single engine at middle rpms in many cases.

Compared to a single speed fixed pitch system, the hybrid has big efficiency advantages at low speed that fade as speed goes up, likely being less efficient at full speed for systems of similar technology and capability.

[bridaus]

Originally Posted by saghost

If you want to have an efficiency discussion, you'll want to be very careful about defining the conditions for it, because they make a big difference.

Is hull speed the way you normally operate? The impression I'd gotten from readying is that a lot of cruisers motor slower than that, for better economy - cats running a single engine at middle rpms in many cases.

Compared to a single speed fixed pitch system, the hybrid has big efficiency advantages at low speed that fade as speed goes up, likely being less efficient at full speed for systems of similar technology and capability.

Right on! I'd define it as the most common trip someone would take from engine on to engine off. I'm curious as to what everyone thinks that is.

Or if we have to make it more simple, pick the most likely cruise speed for a hull and check fuel consumption at that steady state. This benefits the ICE (removes duty cycle losses), but is a valid conversation starter at least. Can always add duty cycle after based on calculated efficiencies from the exercise.

[Dockhead]

Originally Posted by bridaus

No you cannot, the engines will die during warranty, but they will not be fixed under warranty.

Nonsense.


Marine diesel engines have different power ratings -- intermittent vs. continuous. Continuous duty ratings are important because power boats, especially planing power boats, often use their engines at maximum power for long periods of time.


The difference between the continuous and intermittent duty ratings is usally about 20%, sometimes less.


So as long as you size the engine so that you are not taking more than the CONTINUOUS maximum power rating, you can run it as long as you like.


But why? Why would you do this?



This whole issue is a big fat red herring. Maximum efficiency of diesel engines is usually at about 75% of maximum power. But the difference in specific fuel consumption between say 35% and 75% is less than 10% in the table posted earlier in the thread, and between 35% and 90% is about the same. You're going to have the same issue running a generator to run a hybrid drive -- if you use the generator wide open, it is NOT indeed going to be running in its most efficient regime, and anyway you're only chasing 10% or so -- and this is a waste of time. Neither with hybrid nor with conventional drive are you going to be able to easily get right into the maximum efficiency groove, and you certainly will never get there with a hybrid drive and intentionally undersized generator where you may need to add battery power during periods of high power demand.


My single diesel engine is a 100 hp Yanmar. I normally need 20hp to 25hp for relaxed cruising speed in good conditions. Specific fuel consumption is higher in this regime than at 75hp, but remember this is SPECIFIC fuel consumption -- per hp/hour of work done -- and if you're using less absolute amount of power, you're going to burn less fuel, even if you are burning MORE fuel per horsepower produced. I don't often need all 100 hp, but when I do need it, I REALLY need it, and I wouldn't have this boat with less power than that (that's about 4.5hp per tonne). Those 100 hp have saved my backside a couple of times.



With series hybrid drive, you are losing 10% or more in conversion losses right out of the box. You'll never make that up out of a better operating regime for the diesel even if you could be more sure of operating in a more efficient regime, which you can't.


So this is simply not an advantage of series hybrid. I am not speaking only from theory -- I have a friend who owns a 200 foot diesel-electric research vessel. It has a whole bank of generators to run the big electric motor driving a single giant screw, and the engineer can run different combinations of generators to get them in their ideal operating regime. Nevertheless, the fuel burn is about 15% greater than a conventional four stroke diesel mechanical drive would be, and more than 20% greater than a low speed Wartsilla two stroke would be. That is despite the giant wheel, something we can't put on sailboats, which adds to propeller efficiency, taking advantage of electric motor torque curve. I know all this because when the existing propulsion system needed an expensive overhaul, he commissioned an expensive engineering study to compare the advantages and disadvantages of diesel-electric vs. mechanical drive. He ended up overhauling the diesel-electric system rather than converting to mechanical, but it almost made sense to carry out very extensive modifications to the vessel to fit a mechanical drive.


There is a lot of pure wishful thinking in a lot of these posts. Using a small diesel generator which cannot produce as much power as the electric motor needs at full power is not a recipe for a long lasting generator, or for better fuel consumption -- it will be operating wide open a much greater part of its life than with a normal drive, burning more fuel and incurring more wear and tear per hour. What this might achieve is to make it possible, by using batteries to supplement generator power for short term requirements for high power, to use a cheaper and lighter diesel engine. For a cat which needs two screws, there might be an advantage in using one bigger diesel compared to two smaller ones. Those might be good things, but the cost will be more fuel burned and faster engine wear.


The other measure which is often touted here is to simply reduce maximum power available. What's the point of this? You guys don't have bad weather, head seas, lee shores, where you sail? An undersized generator is going to be lighter and cheaper, but that's about the only advantage. If you're regularly using more than 75% power, you will be using more fuel than optimum. From a fuel consumption point of view, you might as well go the other way down the curve, regularly use 40% or 50%, get the same specific fuel consumption, and have a bunch of power in reserve when you need it. But I guess undersizing the generator in a hybrid system is needed to make up for the extra weight and cost of the electrical gear. But this is a mere illusion.


Notwithstanding many claims in here, series hybrid simply does not make sense for sailboats. You pay more for more complicated machinery just to lose power and fuel converting from mechanical to electrical and back to mechanical.



Parallel hybrid, particularly on a cat which needs two screws, might be a very different matter. With such a setup you could efficiently drive ONE of the props mechanically, and use that for long distance cruising. For harbour maneuvers or when you need short term max power, you can supplement with the other screw driven by an electrical motor. You could end up with only one diesel engine that way -- a considerable advantage. You might size it somewhat less than the motors needed for conventional drive because you can add battery power for short-term high power needs. You could store cheap grid power by plugging in overnight.


On the other hand, you could just have two smaller diesels like a normal cat, and forget about it. I would guess that of all of the various combinations discussed in this thread, a bog standard catamaran cruising on one engine has the best chance of hitting the efficiency sweet spot at about 70% to 80% of max power, and gaining the 8% or 10% or whatever you get running the engine at that rather than at 40% or 90%. And with no conversion costs. Plus you have totally redundant drive systems and engines. You can generate domestic power with large second alternators so get rid of the heavy AC generator. Unless you sail in a way which allows you to take advantage of cheap electrical grid power plugged in over night, for short term motoring to get in and out of harbours -- a very narrow use case -- I don't really see how you can beat a totally normal catamaran for cost, robustness, fuel efficiency, or weight. At the current state of the art. It's good of course that someone is playing around with hybrid technology -- otherwise the technology would not progress. I'm sure there will be breakthroughs, but will we live to see them? I'm not sure.

[OldMan]

Originally Posted by bridaus

This is exactly the kind of math I'm working on, but poorly and in my spare time. The key is good attributable input data.

Don't forget the gearbox. 3-15% loss according to Gerr.

Also don't forget duty cycle. One gets to hum at any speed/efficiency we want, one has to go from idle to WOT and back again varying amounts. I find this is the hardest number to calculate.

Edit:

1. Where do you get 93%? I'm looking for sources for my own calculations.
2. Where do you get 750W loss? Same reason, just need to add to my dataset. Thanks!

1. The backend of my genset is Mecc-alte. I checked the specs, 89%-93% efficiency depending on load - higher load better efficiency (given same temperature). I googled a couple of industry white papers that concurred with the 85%-95% efficiency for genset alternators.


2. I remember seeing OV literature stating 95% efficiency. 5% of 15KW = 750W.


BTW, the OV saildrive has gears also, albeit one less set of bevel gears.

[bridaus]

Originally Posted by OldMan

1. The backend of my genset is Mecc-alte. I checked the specs, 89%-93% efficiency depending on load - higher load better efficiency (given same temperature). I googled a couple of industry white papers that concurred with the 85%-95% efficiency for genset alternators.


2. I remember seeing OV literature stating 95% efficiency. 5% of 15KW = 750W.


BTW, the OV saildrive has gears also, albeit one less set of bevel gears.

Thank you! I'm thinking shaft drive, but in any case SD ICE = SD EP so it can be ignored as being equal.

[bridaus]

Originally Posted by Dockhead

Nonsense.


Marine diesel engines have different power ratings -- intermittent vs. continuous. Continuous duty ratings are important because power boats, especially planing power boats, often use their engines at maximum power for long periods of time.

The difference between the continuous and intermittent duty ratings is usally about 20%, sometimes less.

Nonsense to your nonsense kind sir, the engines in this thread are Yanmars. Pleasure duty rated, not your friends hybrid vessel. The difference can be up to 80% dependent on the exact ratings you are talking about.

Originally Posted by Dockhead

This whole issue is a big fat red herring. Maximum efficiency of diesel engines is usually at about 75% of maximum power. But the difference in specific fuel consumption between say 35% and 75% is less than 10% in the table posted earlier in the thread, and between 35% and 90% is about the same. You're going to have the same issue running a generator to run a hybrid drive -- if you use the generator wide open, it is NOT indeed going to be running in its most efficient regime, and anyway you're only chasing 10% or so -- and this is a waste of time. Neither with hybrid nor with conventional drive are you going to be able to easily get right into the maximum efficiency groove, and you certainly will never get there with a hybrid drive and intentionally undersized generator where you may need to add battery power during periods of high power demand.

Disagree respectfully.

You use the generator where it's SFC is best. Not at WOT, this is not how generators are designed.

10% a waste of time? Why are we talking about electric motor loss then at all? Your argument contradicts itself. I'll do the math on anything over 1%, it's worth it.

Originally Posted by Dockhead

My single diesel engine is a 100 hp Yanmar. I normally need 20hp to 25hp for relaxed cruising speed in good conditions. Specific fuel consumption is higher in this regime than at 75hp, but remember this is SPECIFIC fuel consumption -- per hp/hour of work done -- and if you're using less absolute amount of power, you're going to burn less fuel, even if you are burning MORE fuel per horsepower produced. I don't often need all 100 hp, but when I do need it, I REALLY need it, and I wouldn't have this boat with less power than that (that's about 4.5hp per tonne). Those 100 hp have saved my backside a couple of times.

I'd be interested to know how much of the 100HP saved your backside, and why the same amount of electric HP (even at 1:1) wouldn't? The argument for less electric HP is based on not needing the HP. However, if you feel you need it, buy it. EP or ICE, this argument doesn't matter if you want the reserve, but does matter if you don't.

Originally Posted by Dockhead

With series hybrid drive, you are losing 10% or more in conversion losses right out of the box. You'll never make that up out of a better operating regime for the diesel even if you could be more sure of operating in a more efficient regime, which you can't.

And gearboxes can lose up to 15%. "Never"? What data do you base that on? I'd like to see any data you have on this.

Originally Posted by Dockhead

So this is simply not an advantage of series hybrid. I am not speaking only from theory -- I have a friend who owns a 200 foot diesel-electric research vessel. It has a whole bank of generators to run the big electric motor driving a single giant screw, and the engineer can run different combinations of generators to get them in their ideal operating regime. Nevertheless, the fuel burn is about 15% greater than a conventional four stroke diesel mechanical drive would be, and more than 20% greater than a low speed Wartsilla two stroke would be. That is despite the giant wheel, something we can't put on sailboats, which adds to propeller efficiency, taking advantage of electric motor torque curve. I know all this because when the existing propulsion system needed an expensive overhaul, he commissioned an expensive engineering study to compare the advantages and disadvantages of diesel-electric vs. mechanical drive. He ended up overhauling the diesel-electric system rather than converting to mechanical, but it almost made sense to carry out very extensive modifications to the vessel to fit a mechanical drive.

Almost... but we know that diesel electric on large ships is very common, this example doesn't apply well here for positive and negative reasons. I would avoid the comparison due to confusion it causes. The use cases are not close to similar.

Originally Posted by Dockhead

Using a small diesel generator which cannot produce as much power as the electric motor needs at full power is not a recipe for a long lasting generator, or for better fuel consumption -- it will be operating wide open a much greater part of its life than with a normal drive, burning more fuel and incurring more wear and tear per hour. What this might achieve is to make it possible, by using batteries to supplement generator power for short term requirements for high power, to use a cheaper and lighter diesel engine. For a cat which needs two screws, there might be an advantage in using one bigger diesel compared to two smaller ones. Those might be good things, but the cost will be more fuel burned and faster engine wear.

Marine generators are normally sold on continuous power, not max rated power. You can target best SFC at power needed, rather than something that has to idle, cruise, and WOT with one prop and be efficient at all speeds.

Originally Posted by Dockhead

The other measure which is often touted here is to simply reduce maximum power available. What's the point of this? You guys don't have bad weather, head seas, lee shores, where you sail? An undersized generator is going to be lighter and cheaper, but that's about the only advantage. If you're regularly using more than 75% power, you will be using more fuel than optimum. From a fuel consumption point of view, you might as well go the other way down the curve, regularly use 40% or 50%, get the same specific fuel consumption, and have a bunch of power in reserve when you need it. But I guess undersizing the generator in a hybrid system is needed to make up for the extra weight and cost of the electrical gear. But this is a mere illusion.

Almost all strawman here. Generator sized for continuous power at speed. Batteries to soak up any ups/downs. Reserve already discussed and addressed, it's ALWAYS an option with EP.
Ironically it's one of the greatest strengths of EP as you have a choice. You don't have to buy a huge engine, but you can! Also, weight is not the number one concern as this implies.

Originally Posted by Dockhead

It's good of course that someone is playing around with hybrid technology -- otherwise the technology would not progress. I'm sure there will be breakthroughs, but will we live to see them? I'm not sure.

On this we can almost agree. But I believe we are seeing them now.

[44'cruisingcat]

Doesn't matter, because in many (most?) Installations you can't run the electric motors at 100% continuously either, because you'll run ouy of electricity.

[ssmoot]

Originally Posted by OldMan

Not sure where the infatuation with WOT comes from, it's a ludicrous argument as nobody does such

Peak HP is what diesel-only fans keep claiming as the most important point of comparison.

I think that's silly, but nobody arguing that EP is viable is making the argument that you need to match peak diesel HP. They're making exactly the opposite argument.

In short, you agree with the EP proponents and disagree with the Diesel proponents. Claiming you would size a Diesel for peak HP is at best an unusual strategy and at worst dishonest.

But in your words, nobody actually does that. Finally some common ground.