Oceanvolt Hybrid Motor

[bridaus]

Originally Posted by BigBeakie

Sorry for delay bridaus, busy time of year and I've been more lurking than participating lately...

Yes that breakdown is correct. The Freeflow 46 uses Brunton Autoprops 16.5" don't know the pitch.
The Slyder 47 I don't know the props but for performance cats they are "usually" 17" Gori feathering.

Apologies, the ">" was a typo, I meant to put in a ":: .
I did not mean that the boatspeed was greater than 7 knots

On the issue of regen, this sounds like some thing that would be right up your alley. The analysis, I mean. Because the understanding of why regen is so attractive will come down to math. I think I understand the principles, but don't have the math skills to tackle it even if I had the time.

What some of our engineer friends could do for us is take the hull resistance values for a given cat, then calculate the force produced by a given sail area (main + jib) that results in a resultant boatspeed from a given wind speed, and then make a prediction on how much of that force the regen would "rob" from the sails and therefore how much the boat would slow down. The nice thing about science is that it looks for falsifiability, and can make predictions if the hypothesis is correct.

So here is my guess. The force produced by the sails to move a cat at a given speed is so large that, the regen produced that acts in the opposite direction ( yes, Mr. Newton was exactly correct about conservation of energy) is a very small percentage of the total resultant sail driving force. We guesstimate it at 1 to 2 %. Thus, the speed does not drop by much. But I would LOVE to see the math done.

Here are some data for starters ( Merry Christmas ) from our hull resistance analysis.

Values are hull resistance in Newtons (N) at boatspeeds calm water in Knots (kts):

3.0 kts 320 N
4.2 kts 710 N
5.4 kts 1,380 N
6.5 kts 2,832 N
7.7 kts 3,482 N
8.9 kts 7,634 N

Mainsail 70 square meters, Jib 42 square meters

All I can tell you from direct observation of the regen from Oceanvolt is that when you "push the button" to turn on the regen, you do not see the boatspeed drop very noticeably. It is tenths of a knot, maybe up to half knot from what I have seen. This also accords with the reports from several OV SD15 owners, because i always ask about their regen experience, as I did with SV Reality. His result seems to be an outlier as far as the kW produced, and I look forward to hearing more from him as he gathers more information.

Strangely, from my point of view, nobody seems to ever record good data, which is frustrating.

Here is the Slyder 47 with the older SD15 motors on a reach producing about 1 kW ( per motor) from 9.5 knots boatspeed. When I spoke to Slyder, they did not notice the boat slow down appreciably as they put it in and out of regen, so what can I say? Let's do the math, shall we? It would be a valuable contribution, and I for one would love to get to the bottom of it.

Thanks!

My "tiny fraction" was overstated, and I might not do the numbers on this for a while due to time and I want to focus on efficiencies/design of drivetrain first, I'm not big on regen (I confess I'm not a sailor).

A quick thought on the value, if I can generate 2kWh by pressing a button, I think I'm going to do it every time. I am having trouble envisioning the downside, except maybe the upfront cost? If the wind is blowing, and I have extra speed, I'd be happy to push some of that energy into my battery bank. 2kWh isn't tiny! Nor is it enough to overload anything since the boat would have to take that load anyways. In other words, the loads are exactly the same with or without regen. In other words, pushing the button doesn't make the wind push harder... mother nature simply doesn't care...

[BigBeakie]

Originally Posted by bridaus

Thanks!

My "tiny fraction" was overstated, and I might not do the numbers on this for a while due to time and I want to focus on efficiencies/design of drivetrain first, I'm not big on regen (I confess I'm not a sailor).

A quick thought on the value, if I can generate 2kWh by pressing a button, I think I'm going to do it every time. I am having trouble envisioning the downside, except maybe the upfront cost? If the wind is blowing, and I have extra speed, I'd be happy to push some of that energy into my battery bank. 2kWh isn't tiny! Nor is it enough to overload anything since the boat would have to take that load anyways. In other words, the loads are exactly the same with or without regen. In other words, pushing the button doesn't make the wind push harder... mother nature simply doesn't care...

Yes, exactly right. The idea that you have to strengthen your hull substantially to support the demands of regen are a bit "counter-intuitive" for me.

The benefits of being able to harness that energy when sailing is a game changer for cruisers. You would be unlucky indeed to be under conditions of no wind and no sun at the same time. Sure, there are regions where that can be expected, such as where we want to go one day, the inside passage down the BC coast, but then, OK, we've got to run the genset for continuous motoring. So be it.

I would venture to say that the vast majority of the time, either enough solar ( if you have the space) or the regen from something that delivers as much as the Servoprop, (assuming it delivers as expected), would completely change energy balance on a long distance cruising boat, and make running an electric house on the boat completely feasible. That's pretty much why we've chosen this system, so we'll see how it works out.

[bridaus]

Originally Posted by BigBeakie

Yes, exactly right. The idea that you have to strengthen your hull substantially to support the demands of regen are a bit "counter-intuitive" for me.

The benefits of being able to harness that energy when sailing is a game changer for cruisers. You would be unlucky indeed to be under conditions of no wind and no sun at the same time. Sure, there are regions where that can be expected, such as where we want to go one day, the inside passage down the BC coast, but then, OK, we've got to run the genset for continuous motoring. So be it.

I would venture to say that the vast majority of the time, either enough solar ( if you have the space) or the regen from something that delivers as much as the Servoprop, (assuming it delivers as expected), would completely change energy balance on a long distance cruising boat, and make running an electric house on the boat completely feasible. That's pretty much why we've chosen this system, so we'll see how it works out.

I was thinking one more thing about regen. As soon as you get to certain speeds, a lot of energy goes into pushing the hull just a tiny bit faster (equally for engines and for sail). Essentially this is "wasted wind". Conversely, if you regenerate at these speeds, you'll get a lot of energy for very little speed loss (note that it's not one for one, there are losses, not sure how efficient the prop is at regeneration speeds). I personally would use regen anytime the speed penalty did not affect my plans. Yes, subjective, but so is how much fuel should I burn, how quickly do I want to get somewhere, how much sail should I put up, etc. If "saving" makes you happy, there is extra value in that happiness just like the happiness found in "reserve" power for some people.

BTW, I am a realist. I don't know if solar and regen will change the balance for you, it depends a lot on your use of each. The thing everyone forgets about regen/solar (especially solar) is that time is on your side. While you are out and about in the dingy or snorkeling or whatever, those things are working for you. They don't need supervision, they are very reliable, they just work.

For instance, I installed solar at my home (New England, not the best place for them). Did it myself, and payoff calculated at 2 -3 years, and looks like it will be 2.5 years. Am I happy? Damn right I am, will be in this house another 8-10 years they will have paid themselves off 3-4 times by then and electricity keeps going up. I may add more.

Good luck for sure! Letting us know what you see, even if it's better or worse than what you expected is useful for all!

[DumnMad]

Originally Posted by BigBeakie

So here is my guess. The force produced by the sails to move a cat at a given speed is so large that, the regen produced that acts in the opposite direction ( yes, Mr. Newton was exactly correct about conservation of energy) is a very small percentage of the total resultant sail driving force. We guesstimate it at 1 to 2 %. Thus, the speed does not drop by much. But I would LOVE to see the math done.

Here are some data for starters ( Merry Christmas ) from our hull resistance analysis.

Values are hull resistance in Newtons (N) at boatspeeds calm water in Knots (kts):

3.0 kts 320 N
4.2 kts 710 N
5.4 kts 1,380 N
6.5 kts 2,832 N
7.7 kts 3,482 N
8.9 kts 7,634 N

Mainsail 70 square meters, Jib 42 square meters

So increase in speed 1.2knots for each step and get a big jump around 8 knots;
3 to 4.2k = 390 extra resistance.
4.2 - 5.4 = 670
5.4 - 6.5 = 1452 (maybe an error here.)
6.5 - 7.7 = 650
7.7 - 8.9 = 3,252 = big jump in resistance. WHOA, is this hullspeed.

But 44 says multihulls don't have hullspeed. Posts 1654 & 1658.

[BigBeakie]

Originally Posted by bridaus

I was thinking one more thing about regen. As soon as you get to certain speeds, a lot of energy goes into pushing the hull just a tiny bit faster (equally for engines and for sail). Essentially this is "wasted wind". Conversely, if you regenerate at these speeds, you'll get a lot of energy for very little speed loss (note that it's not one for one, there are losses, not sure how efficient the prop is at regeneration speeds). I personally would use regen anytime the speed penalty did not affect my plans. Yes, subjective, but so is how much fuel should I burn, how quickly do I want to get somewhere, how much sail should I put up, etc. If "saving" makes you happy, there is extra value in that happiness just like the happiness found in "reserve" power for some people.

BTW, I am a realist. I don't know if solar and regen will change the balance for you, it depends a lot on your use of each. The thing everyone forgets about regen/solar (especially solar) is that time is on your side. While you are out and about in the dingy or snorkeling or whatever, those things are working for you. They don't need supervision, they are very reliable, they just work.

For instance, I installed solar at my home (New England, not the best place for them). Did it myself, and payoff calculated at 2 -3 years, and looks like it will be 2.5 years. Am I happy? Damn right I am, will be in this house another 8-10 years they will have paid themselves off 3-4 times by then and electricity keeps going up. I may add more.

Good luck for sure! Letting us know what you see, even if it's better or worse than what you expected is useful for all!

I like the way you think Obviously you "get it".

You are absolutely correct (again) about the energy harvesting with regen. You don't have to be going very fast to start harvesting some of the energy, just look at the hull resistance data I put in my post. For us to go the extra 1.2 knots from 8.9 knots instead of 7.7 knots, it takes an extra 4.2 kW.!!! We are now on the steep part of the log curve.

This is why it isn't worth it to go WOT on EP; the speed increase is bugger all but the extra power consumption is massive. But sails generate LOTS of power and as the wind gets up past 10 knots, there is enough to "divert" a bit to regen. Let's do the math on how much sail power we're talking about, I think it would be surprising to many of us.

It's not that catamarans don't have a hull speed theoretical limit, it's that their hull resistance curve is so much "less steep" (awkwardly put ) than a mono. I've seen the hull resistance curve for a Lagoon, and it was pretty frightening as well. Hull shape hydrodynamics is really important in this regard.

And that is why the diesels CAN go about 1 to 2 knots faster than EP at WOT, because they have all that energy density that they can just throw away with the extra revs, along with heat & noise & friction. Assuming you've sized your diesels 2 to 3 times bigger than the electric, of course, as you have so elegantly shown.

Sometimes I have to smile when the diesel guys crow about DD "efficiency" compared to hybrid. It may be true (marginally) but it's only because diesel is so massively energy dense in comparison, that they can AFFORD to use such inefficient ICE which puts only about 25% of that energy density to work.

[OldMan]

Hmm, discussion went from engineering to marketing....

[bridaus]

Two people agree and it's marketing?

Nah, you guys just aren't satisfied when the rebels form an alliance.

When I have some time this week I'll stir up some controversy. I'm planning on questioning Gerr's transmission efficiency numbers. I don't believe them.

[bridaus]

#1
Freeflow 46
Yanmar 54HP 4JH5E
7 knots on one engine at 2250rpm using ~17kW output at prop
Brunton Autoprops 16.5" don't know the pitch.

#2
Slyder 47
SD15
7 knots using 15kW (not output at prop)
I'm assuming this is the OV prop, not the 17" Gori feathering that the Slyder usually uses?

I think in the end we don't have enough data to tell what is going on. Autoprops aren't efficient? Yanmar old/not producing? Yanmar specs incorrect? Slyder slightly faster hull/clean hull? There are so many possibilities here I don't know if we can get any more out of these examples.

[tp12]

Originally Posted by bridaus

Two people agree and it's marketing?

Nah, you guys just aren't satisfied when the rebels form an alliance.

When I have some time this week I'll stir up some controversy. I'm planning on questioning Gerr's transmission efficiency numbers. I don't believe them.

Thanks for your contributions, it's good to see numbers challenging myths and preconceptions. It's a very useful thread.

[ssmoot]

Originally Posted by john61ct

The **critical** advantage of EP in my use case is **I hope** it will make diesel electric feasible for running the (heavy for such a small boat) House loads.

So if I understand correctly, the only reason you're considering EP is to have a large generator onboard for house loads since you only have room for one diesel?

You accept that you'll:

1. Run the generator whenever you need to propel the boat
2. Increase weight with the large generator plus motor
3. Will loose some amount of volume in the engine bay at least

Have you considered a large alternator? A 12V/180a alternator would put you at a comfortable 0.33C charge rate without having to buy a huge generator or motor and will weigh less while probably being a bit more efficient.

I'm not trying to be difficult. I just don't understand the motivation for such a setup.

[44'cruisingcat]

Originally Posted by BigBeakie

Here is the Slyder 47 with the older SD15 motors on a reach producing about 1 kW ( per motor) from 9.5 knots boatspeed. When I spoke to Slyder, they did not notice the boat slow down appreciably as they put it in and out of regen, so what can I say? Let's do the math, shall we? It would be a valuable contribution, and I for one would love to get to the bottom of it.

Did we watch the same video? On the one I watched, one motor seemed most of the time to be producing a bit less than 1 kW, the other closer to around 500W

Speed mostly 9.5 to 10.

[ssmoot]

Originally Posted by transmitterdan

Regen is not efficient.

People seem to think it's damn near magical in cars!

Originally Posted by transmitterdan

It requires about 10 times more power from the rig than the energy it produces to the batts. So to get 1kW regen the sails have to produce about 10kW.

Citation needed. I don't see many claims that Watt & Sea 600s are blowing out sails and ripping off transoms. Do you? Their lowering mechanism certainly doesn't look up to the task.

[bridaus]

Originally Posted by ssmoot

So if I understand correctly, the only reason you're considering EP is to have a large generator onboard for house loads since you only have room for one diesel?

You accept that you'll:

1. Run the generator whenever you need to propel the boat
2. Increase weight with the large generator plus motor
3. Will loose some amount of volume in the engine bay at least

Have you considered a large alternator? A 12V/180a alternator would put you at a comfortable 0.33C charge rate without having to buy a huge generator or motor and will weigh less while probably being a bit more efficient.

I'm not trying to be difficult. I just don't understand the motivation for such a setup.

I tend to agree, ripping out perfectly good equipment for EP is a big deal when you could just upgrade.

I'd only consider it on new, repower, or if I was looking for a project.

[bridaus]

Originally Posted by 44'cruisingcat

Did we watch the same video? On the one I watched, one motor seemed most of the time to be producing a bit less than 1 kW, the other closer to around 500W

Speed mostly 9.5 to 10.

I saw one at about 1kW and the other at about 500W and also wondered... How can they be different?

[ssmoot]

Originally Posted by 44'cruisingcat

Going downwind, slower = more apparent wind. If you have the same sails up, loads will be higher.

Anyway, this should be obvious - if you're extracting power when sailing, that power has to come from the sails.

That's... exactly what I said. I mentioned that when considering slowing down for comfort, you might use that extra power instead. No where did I suggest to change your reefing strategy.

Of course "loads will be higher". But that's just pedantry. The claim that regeneration is only 10% efficient, and that you'll be exposing your boat to dangerous loads by pulling 400w off a sail drive aren't credible assertions on their own however.