Solar sails and the future of hybrid cats

[Seaslug Caravan]

C'mon BigBeakie you made a promise.

------------------------------------------

12-05-2017, 13:53 #940
BigBeakie
Registered User

Re: Oceanvolt Hybrid Motor

Yes, congratulations! No more EP information to rubbish, yahooo👍

End of posting from this end.


---------------------------------------------

[ssmoot]

Originally Posted by BigBeakie

you could run one in regen while motor sailing on the other.

That would be a net negative in energy compared to just folding the prop. Like trying to ride your brakes in an EV to use regen while accelerating (the ECUs probably just don't allow it, but I never thought to attempt it myself). Whatever power you put into the system to move forward, you're only recovering a fraction of through generation.

...the torque curve is very flat for the OV SD15 and AXC series. It does tail off a bit, a bit, at the highest RPMs, but nothing like a diesel does.

Looking at the data sheets, the couple Yanmars I've looked at actually have impressively flat torque curves off idle. They're massively underloaded at cruising speed, which is why that's what they're rated for a continuous usage duty cycle there.

That creates an opportunity to substitute an electric motor since you don't have to worry about finding a "sweet spot".

Electrics do not run out of oxygen like an ICE does, but you knew that, right?

At these engine displacements and RPMs, I don't think the diesels are necessarily running out of air and the torque curves I've seen from Yanmar don't appear to indicate that.

I'm not suggesting these are bad engines. I just think electric is a better solution going forward, and I don't think it's very honest to talk about "33kW" when that's purely a function of cruising efficiency and duty cycles. It's much more realistic to think of it as the boat builder intended: A ~10kW engine.

It's just marketing basically. Some might call it "lies". Not me. But some of us seem to take all this very personally.

But honestly it's getting boring. You want a bigger motor? Buy a bigger motor and then go on to use a tiny fraction of it's potential because running it at anything above hull-speed is extremely inefficient. Just like with diesel. I don't think it's the best move if you could save 100lbs instead (pulled that number right out of my ass I did), but it's not going to hurt me none.

And just to be clear, Oceanvolt's packaging looks very very pretty, but over $50K for a pair of 15kW motors and a 24kWh battery pack is pretty insane to me. I also question the wisdom of 48v banks, but maybe they were prioritizing a more drop-in solution for repower jobs.

[44'cruisingcat]

Originally Posted by ssmoot

What's a "33kW" diesel? Is it one you can hook up to a 25kW generator and run for a whopping 30 minutes every 10 hours? Because that's the type of engine we're talking about here.

No? That'd be silly?

The feigned ignorance gets old. You can disagree and make a case for what is most important to you without coming off like a child who thinks he's caught his parents in his clever word-games trap.

What sort of magical thinking does it take to pretend we're talking about a "33kW" engine, and not a ~10kW engine that's only capable of 33kW in short bursts when putting ~3.5X the fuel into it? You might want to get the genny manufacturers on the phone. Clearly you're better at this than them and can inform them how to produce a generator for a fraction of the weight and fuel cost they're managing.

I'm looking for justification for the claims of equivalency. So you don't think a 33 kw diesel can run a 25 kw generator continuously? I'm pretty sure it could, but fine, how about a 20 kw generator? How about 15? Can your 15 kw electric motor even run a 15? Nope.

[ssmoot]

Originally Posted by 44'cruisingcat

So you don't think a 33 kw diesel can run a 25 kw generator continuously? I'm pretty sure it could

Yanmar says their 57hp diesel can't.

Yanmar. Not me.

Can your 15 kw electric motor even run a 15?

Of course it can't. Because (say it with me this time please): Perpetual motion machines don't exist.

Now, what 45hp engine are you talking about specifically? Can it run a 15kW generator? We'd have to know it's M1 duty cycle to know that. It might. It very well might not.

But lets suppose we're talking about a Yanmar 4JH45: http://www.yanmarmarine.com/theme/ya...heet_4JH45.pdf

Oh wow. Would you look at that. There's a knee in fuel consumption right at 2,000RPM. It looks like it'll use about 0.7gph right there. That's somehow coincidentally right near peak torque. I wonder how much work it's putting out there? Oh my, that's totally unexpected. About 10kW.

It's almost like there's a reason generators use bigger displacement engines, weigh so much more and drink more than twice as much fuel to provide the 25kW number you're looking for. Who would have thunk it?

Let's look at the Northern Lights M864W3. It weighs twice as much! It's got about 20% more displacement. Unlike the square cylinder Yanmar it's a longer-stroke undersquare design for higher torque. And yet it's only rated at 39hp and burns 2.23gph! Because unlike the Yanmar it's actually putting something in the ball-park of 28kW into the generator to get 25kW of electricity out. So it's doing pretty good.

Turns out it's not magic. The Yanmar drinks 3.5X the fuel at WOT because it really is putting out ~30kW at that RPM. In brief spurts at least. Let's see what they say in the operation manual (you might actually want to read it sometime or you might be replacing your diesel a lot sooner than you'd hoped):

The 4JH common rail series engines are designed to be operated at maximum throttle for less than 5% of total engine time (30 minutes out of every 10 hours) and cruising speed.

It's almost like using such an engine as a generator would be an incredibly bad idea.

I mean, it looks like you could probably safely drive a 7kW generator with it if you needed to. That's just a bit short of the perpetual motion machine you were looking for though.

And since the power output at cruising RPM is actually a fair bit less than a 15kW motor, it's almost like... wait for it... It's entirely reasonable to consider them at least somewhat equivalent and fit for purpose?

To the surprise of no one who actually bothered to look at any of the links, it sure is lookin' that way.

Maybe the next time you don't understand something, your first instinct shouldn't be to call it "magic". Just a thought.

[Simi 60]

Originally Posted by Thalas

You're absolutely right. This will never be a solution for sailors who motor most of the time.

If they motor most of the time then sailors they not be.
I point this out regularly to my yachty friends who laugh at us for motoring everywhere while they motor everywhere.

[44'cruisingcat]

Originally Posted by ssmoot

Yanmar says their 57hp diesel can't.

Yanmar. Not me.



Of course it can't. Because (say it with me this time please): Perpetual motion machines don't exist.

Now, what 45hp engine are you talking about specifically? Can it run a 15kW generator? We'd have to know it's M1 duty cycle to know that. It might. It very well might not.

But lets suppose we're talking about a Yanmar 4JH45: http://www.yanmarmarine.com/theme/ya...heet_4JH45.pdf

Oh wow. Would you look at that. There's a knee in fuel consumption right at 2,000RPM. It looks like it'll use about 0.7gph right there. That's somehow coincidentally right near peak torque. I wonder how much work it's putting out there? Oh my, that's totally unexpected. About 10kW.

It's almost like there's a reason generators use bigger displacement engines, weigh so much more and drink more than twice as much fuel to provide the 25kW number you're looking for. Who would have thunk it?

Let's look at the Northern Lights M864W3. It weighs twice as much! It's got about 20% more displacement. Unlike the square cylinder Yanmar it's a longer-stroke undersquare design for higher torque. And yet it's only rated at 39hp and burns 2.23gph! Because unlike the Yanmar it's actually putting something in the ball-park of 28kW into the generator to get 25kW of electricity out. So it's doing pretty good.

.

Well thanks. Turns out a 30 kw diesel can run a 25 kw generator. So a 15 kw electric motor falls a fair way short of being equal.

It's always interesting to note which side of the argument descends into personal insults. And it's always the same side.

Re perpetual motion. You perhaps should be trying to tell your mate big beakie about it not being possible. He's the one claiming that having one engine generating and the other running simultaneously can provide a net gain.

[BigBeakie]

NEVER did I EVER say that there would be a net gain. Once again, you spin and misrepresent to suit your own predetermined position.

Let me lay this out for you so clearly that you can understand. We can only try.

While motorsailing on EP, it is possible to use one motor to assist pointing up a few degrees by just ticking over the leeward motor, while at the same time using the windward side motor to regen some power. Got it? The amount of the regen will depend on SAILING speed, and can never balance the Kw used to motorsail. But its better than nothing, THAT was the point.

Sailors who actually USE EP, instead of just making stuff up and get their jollies being contrarian, will tell you it is a nice motorsailing facility of EP.


Sent from my iPad using Cruisers Sailing Forum

[sailingharry]

Originally Posted by Thalas

It's true the solar sails are not ideally positioned, but working for them is the INSANE surface area (especially double sided if reflected light really does allow the back side to generate 40% power vs direct light). I'd love to see real world numbers on the prototypes currently in the wild. As the technology improves, I'd imagine photovoltaic thread will be directly woven into the fabric itself.

Real world performance numbers would be great. As would real world procurement cost and life expectancy (sails are typically good for 5-10 years if you aren't terribly interested in performance). Also real world sailing reports -- sail shape, furling issues, etc.

[ssmoot]

Originally Posted by 44'cruisingcat

Well thanks. Turns out a 30 kw diesel can run a 25 kw generator.

I spoon fed you exactly how that's not the case for the "30kW diesel" you're using to drive your sailboat, and that's what you get out of it?

Why not strap a bottle of NOX to your diesel then and run a 50kW generator with your apparently infinitely durable engines?

It's always interesting to note which side of the argument descends into personal insults. And it's always the same side.

If you've decided there are teams here, that's probably where the issue is.

As far as insults... I was pretty rude. At worst. If you can't take what you're dishing out for several pages now, maybe you should drink a cup of concrete and cut it out.

Re perpetual motion. You perhaps should be trying to tell your mate big beakie about it not being possible. He's the one claiming that having one engine generating and the other running simultaneously can provide a net gain.

I'm pretty sure I did just that.

I don't know what your guys problem is with each other. I imagine it might have something to do with the way you've behaved here, but I don't know the history. You should probably just buy each other a beer.

[ssmoot]

Originally Posted by BigBeakie

The amount of the regen will depend on SAILING speed, and can never balance the Kw used to motorsail.

Then fold the prop and spend less power. Or even freewheel it.

Think of an electric bike. You've got a generator on the front hub to run your lights, and a motor on the rear hub. Any power you get out of the front hub had to come from the rear hub. So you're paying efficiency losses to get the rear tire spinning, and more losses getting the generator on the front tire to make power.

The best solution would be to remove the front generator and wire the lights into your battery. The lights aren't going to get more efficient, but getting power to them is.

If you know someone claiming they can run a motor in generation while powering the other, and that results in lower net power usage than just folding or letting a fixed prop spin, I'd love to read more because that's a bit hard to believe.

[44'cruisingcat]

Originally Posted by ssmoot

I spoon fed you exactly how that's not the case for the "30kW diesel" you're using to drive your sailboat, and that's what you get out of it?

Why not strap a bottle of NOX to your diesel then and run a 50kW generator with your apparently infinitely durable engines

Where did you get the idea I am using a 30 kw diesel to drive my sailboat? Just another assumption?

[44'cruisingcat]

Originally Posted by BigBeakie

NEVER did I EVER say that there would be a net gain. Once again, you spin and misrepresent to suit your own predetermined position.

Let me lay this out for you so clearly that you can understand. We can only try.

While motorsailing on EP, it is possible to use one motor to assist pointing up a few degrees by just ticking over the leeward motor, while at the same time using the windward side motor to regen some power. Got it? The amount of the regen will depend on SAILING speed, and can never balance the Kw used to motorsail. But its better than nothing, THAT was the point.

Sent from my iPad using Cruisers Sailing Forum

The point you don't get is that in reality it would be worse than nothing.

[Seaslug Caravan]

Originally Posted by BigBeakie

While motorsailing on EP, it is possible to use one motor to assist pointing up a few degrees by just ticking over the leeward motor, while at the same time using the windward side motor to regen some power. Got it? The amount of the regen will depend on SAILING speed, and can never balance the Kw used to motorsail. But its better than nothing, THAT was the point.

BB You have an interesting concept.
I really want to be a believer in EP. I have seen no evidence to make me believe.



Yes Yes I know anything helps when trying to get a multihull to windward, but the use of EP as you describe sounds interesting.

The way I understand it is that as the boat points higher and starts to slow the leeward motor tickles it along a little, as the regen/drag from the windward prop reduces with the loss in speed. then as the auto pilot struggles to get the boat to fall off the wind and gather speed the windward motor starts to automatically regen, increasing the DRAG and causing the boat to scew up into the wind a little , slow a little , then repeat.

Certainly not the quickest way to get to windward, and depending on the boat and autopilot may end in the boat spending a lot of time in irons. Certainly nothing here that a properly set sail plan and a WINDWARD diesel ticking over would'nt do better. ( or the windward EP if thats your fancy)

[ssmoot]

Originally Posted by 44'cruisingcat

Where did you get the idea I am using a 30 kw diesel to drive my sailboat? Just another assumption?

So I said "your" engine when I should have said "the engine we've been talking about for the last six pages".

If that's really the best you can do at this point it might be time to just grab a beer, a comfy seat, and reflect a bit.

You're looking at a light-duty engine and characterizing it as a work engine that weighs significantly more and uses significantly more fuel thinking it's going to deliver 45hp in anything but short bursts. You've fallen for marketing and (in your words) "lies" basically.

Just to be clear, I don't think that's a fair statement at all, but that's the position you've been peddling.

It's more accurately a 12kW engine that can be overdriven 5% of the time. The graphs are freely available. From the manufacturer. Please don't take my word for it. I'm running out of ways to say the same thing over and over.

There is no one single number you can pin on it realistically. It totally depends on your duty cycle. The duty cycle for continuous cruising efficiently with the upgraded 4JH57 engines on a Lagoon 42 puts them at about 12kW.

You can overpower an electric motor as well if you need a hole-shot, but you don't see me claiming that makes it a 20kW motor.

It seems you might not have been aware of that. Here, I'll help you out: LMGTFY

You might also find this interesting: https://youtu.be/dwKyuAErMfg

Here he's put 4X the power into a motor and the primary concern is bearings and heat. So does that mean we get to call our 15kW motor a 60kW motor? Of course not! First off, Oceanvolt (or whomever) has to warranty the thing so they're not likely to let you do it in the first place. Secondly, that wouldn't be a continuous duty cycle. You could probably go 20% above the rating continuously with no ill effects if the controller allows it (it's pretty common to overspeed a 50hz motor at 60hz or more), but how much further and how much you may be risking your motor is between you and whomever is warranting it.

So now that we've established that electric motors also have duty cycles, but the number they're sold at is typically the equivalent of a diesel's M1 duty cycle.

EV manufacturers take advantage of this as well. Both Tesla and Porsche (in the 918) will boost the current to the electric motors for brief periods. They usually just refer to it as "launch/passing mode" or similar.

Do you understand yet? You've been comparing a peak rating to a continuous one and calling the latter a lie. You're apparently very misinformed about how much power a diesel on a sailboat is actually producing 95% of the time and have been implying that other people are fools who don't know what they're talking about. You've been making snarky, disingenuous comments the entire time, and not doing your own homework. I've explained numerous times how all this is just a cruising efficiency consideration and you can buy whatever size motor you think makes sense, and you haven't acknowledged it once (even Oceanvolt will sell you 50% more power for 10% more cost).

Have at it buddy. I'm going back to lurking. Sorry for helping to spoil your thread Thallas.

[valhalla360]

Originally Posted by ZULU40

this obtuse method of accusing people of lying ..

As has been stated several times, the torque curves are the inverse of one another...

If you are driving a car in stop and go traffic, this all makes perfect sense. On a displacement cruising boat set at 6.5kts and just chugging along, it's irrelevant.

Nothing obtuse about it. If you claim a 15kw electric motor has the same hp as a 45hp diesel, that is a lie and there is no way around it.