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Old 13-12-2018, 13:48   #1636
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Re: Oceanvolt Hybrid Motor

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Originally Posted by OldMan View Post
I doubt I can get to 3400rpm....I know I can get to 3200, maybe 3300, fixed props. Target cruise speed is 7-7.5kts @ 2700-2800rpm.


FWIW, that model engine ceased production in 2005 (I think), mine are the last vintage of that model.
Looks like you are hitting 15kW on the nose at 3200 rpm, so 30kW total. More later...
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Old 13-12-2018, 13:52   #1637
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Re: Oceanvolt Hybrid Motor

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But it is braking....the power comes from somewhere, no magic! The regen prop in the water is drag on the boat. If the boat could use that power for faster speed, then yes, it's "braking".


SVReality reported a .5kt slowdown to realize 400W of regen.
Until you reach hull-speed. Then it might actually be more efficient to store excess energy instead of using it to "climb hills".

But the bigger piece of the puzzle is that it allows you to arbitrage power during times of excess, when you can easily afford going from 7.5kts to 7kts, to times of lean, when you'd rather be going 3 or 4kts than 0kts.

If your batteries are already full during times of excess, then make water for free instead. Or run the air conditioning. Or take hot showers. Or run up the motors and point a few degrees higher.

Regeneration isn't not power production. Like you said, that power is already there. Regeneration is the flexibility to decide how and when to use it.
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Old 13-12-2018, 13:58   #1638
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Re: Oceanvolt Hybrid Motor

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I'm going back to lurking for awhile, but I can't resist.

This is a myth. It absolutely does not "contribute a lot" in the way a layman might think of.

It's a generator connected to a shaft. It doesn't matter if it's an axle or a crankshaft.

Say it's 70% efficient. That power gain only applies to kinetic energy. Not all the energy you put into the system to get where you're going. If you accelerate up to 50MPH, then apply the brakes immediately, you'll get the exact same amount of power as if you'd driven on the highway for 100 miles with no braking, and then had to stop at a light.

Not only that, but because it's not 100% efficient it's always more efficient to avoid braking entirely. Which is why hyper-milers try to take curves without slowing down, and coast between lights to avoid using brakes.

Regenerative braking is more efficient than using friction brakes since friction brakes are 0% efficient. But there's nothing more efficient than not braking in the first place.

But wait you say, the Prius gets better City mileage than Highway! Isn't that due to regenerative braking?

The short answer is no. Just think to yourself, how often do you have your foot on the brake pedal vs the accelerator? Sure there's some benefit to it, but nowhere near the 25% difference you might see on the Munroney. You might find this thread of hyper-miler record holders enlightening: https://priuschat.com/threads/top-20...olders.112709/

Compare it to a Chevy Volt with a much larger battery. The Volt is also a hybrid. It also has regenerative braking. It's also direct driven when on engine power. But the city mileage advantage disappears entirely. Or take a look at my wife's Chrysler Pacifica PHEV. It actually gets significantly better highway mileage when the battery is depleted because it's more efficient to run off generator power than use regenerative braking.

If you've got an electric motor moving the wheels, regenerative braking is a no-brainer feature for boosting fuel economy in the city to reasonable levels. But it's not magic. It's actually more efficient to not waste that power in the first place.

It's exactly the same as traveling in a flat vs hilly area. Just because you get to coast "for free" down the hills doesn't make up for all the extra fuel you're burning to climb them. That would make your vehicle a perpetual motion machine if it were true.

If you could drive everywhere at around 45MPH without any stopping or hills, you'd get the most miles out of the vehicle. If you need further proof than me saying so, just read the accounts of hyper-miler record holders and their tips for maximizing mileage.

So if you're going to move a vehicle with electricity, then a boat, running at hull-speed (avoid wasting energy climbing up and down "hills" as much as possible) on passage is actually pretty close to the best case scenario for electric propulsion.

As I stated several posts back, the Honda 2-motor hybrid locks the ICE to the drive train at highway speeds. This supports that DD is more efficient at (highway) cruise speed. Honda uses an Atkinson duty cycle engine, i.e., terrible efficiency at low rpm/power, hence run the engine in it's efficiency range to power the EP. Yes, highway mileage is worse than city mileage. I can't comment on how much regen contributes, but it does contribute.


I did get admonished for talking about cars, but reality is the ICE/hybrid EP can't tell a wheel/tire from a prop.
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Old 13-12-2018, 13:59   #1639
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
. . . Ability to downsize the overall power requirement because we are not required to oversize. I have mixed feelings about this. DD folks point to it as a weakness because EP folks are choosing to target cruise instead of cruise + reserve. They also cry "not apples to apples", but that is silly. Ability to size correctly is a benefit that can be counted if the sizing is correct. But I have yet to find anyone who can tell me exactly how much reserve is required. To me (and maybe most EP folks) reserve is wasteful and hard to justify because you can't quantify it. How do I know if 10 or 20 or 50% more power is enough to save my bacon? How do I know that I can't save myself with my existing max cruise power? What do sailboats with tiny engines do for reserve? I would love some math on reserve power, I asked a while ago and no one answered. I will keep this in my calculations, but others don't have to (including DD folks who are used to having it and won't want to give it up regardless of whether it can be quantified, they feel good about it and that's worth something to them). It's important to note that this is not a large savings because the power requirement is still the same at cruise, so we are unlikely to save a large amount just due to engine sizing. Capital cost mostly, but we lose that in our generator because it's duty rating has to be higher (therefore bigger in any case) It might be worthy of calculating if it's 1 or 2%. It's not the largest savings by far however, therefore I list it last.

.



I on the contrary do not have mixed feelings about this. This is a clear advantage of hybrid drive -- being able to size the internal combustion engine for typical loads rather than maximum ones.


I do not believe there is any advantage in fuel consumption in this (see previous post), but there is a big advantage in size and WEIGHT of the engine you need. If the hybrid parts were light enough, not to throw back onto you the weight you saved with a smaller engine, then that itself will save fuel and improve sailing performance. If you could eliminate one diesel engine in a cat by driving the second screw with electric, then maybe you could get some serious savings in weight, and that might be worthwhile even at the current state of the technology.


On the other hand, keep in mind that there are ways to get a lot of reserve power out of mechanical drive diesel, too. A great way to do this is to turbocharge and intercool a small block diesel. This greatly increases the range of power outputs which can be produced efficiently because the high pressure turbo can vary the mass of air in the cylinders. So you can run such an engine in an entirely healthy (and fuel efficient) regime at only 25% of max output, but you have 4x that much on tap if you need it. The fuel map of a high pressure turbocharged diesel has a much larger sweet spot, than a naturally aspirated one does.


Yanmar 4JH3 DTE makes 120 horsepower out of 260kg including the gearbox. About the same weight as my 6.5kW generator, which produces an order of magnitude less power. Makes you think.



How much reserve power do you need? Well, that depends on what kind of sailing you do. A fair weather day sailer hardly needs any. A mild latitude short distance cruising boat needs a bit more, but not that much. A high latitude expedition boat needs a TON of reserve power. Anyone who's ever had to claw off a lee shore against a gale, or fight his way over a bar against a head sea, will know what I'm talking about.
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Old 13-12-2018, 14:22   #1640
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Re: Oceanvolt Hybrid Motor

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Originally Posted by ssmoot View Post
Until you reach hull-speed. Then it might actually be more efficient to store excess energy instead of using it to "climb hills".

But the bigger piece of the puzzle is that it allows you to arbitrage power during times of excess, when you can easily afford going from 7.5kts to 7kts, to times of lean, when you'd rather be going 3 or 4kts than 0kts.

If your batteries are already full during times of excess, then make water for free instead. Or run the air conditioning. Or take hot showers. Or run up the motors and point a few degrees higher.

Regeneration isn't not power production. Like you said, that power is already there. Regeneration is the flexibility to decide how and when to use it.

Agree...just want everyone to realize it takes power from somewhere for regen, if the power would have been wasted anyway, that's great!



BTW, on my boat, after solar has the batteries charged, turn on the ice maker! Going to test the hot water heater next.
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Old 13-12-2018, 14:25   #1641
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Re: Oceanvolt Hybrid Motor

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Originally Posted by ssmoot View Post
Until you reach hull-speed. Then it might actually be more efficient to store excess energy instead of using it to "climb hills".

But the bigger piece of the puzzle is that it allows you to arbitrage power during times of excess, when you can easily afford going from 7.5kts to 7kts, to times of lean, when you'd rather be going 3 or 4kts than 0kts.

If your batteries are already full during times of excess, then make water for free instead. Or run the air conditioning. Or take hot showers. Or run up the motors and point a few degrees higher.

Regeneration isn't not power production. Like you said, that power is already there. Regeneration is the flexibility to decide how and when to use it.

I think this is a sound analysis.


The only problem with regen during sailing is that with the current state of technology, it takes a lot of speed to get any useful power out of it. Might be somewhat useful on a very fast catamaran with a big SA/D, but fairly useless on moderate size cruising monos (and probably condo cats as well).


I do agree with you, though, that there might be a lot of times when you would be willing to suffer a speed hit, to produce power for free, so not just when you are anyway at hull speed and have excess power available. Thinking back on 4000 miles of sailing I did last summer -- there were a lot of times when it was a real bother to run an engine to produce power. Sometimes we were sailing hard and well heeled over, and you worry about oil starvation of a diesel, so you reef down before you start it up . Other times it's just irritating to have an engine running when you are sailing beautifully and don't need a diesel for propulsion. It would have been nice to be able to generate power by regeneration -- and not just for the purpose of saving fuel, or even at all. Plus or minus a few percent of fuel consumption just doesn't move the needle, in the context of all of the other expenses.
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Old 13-12-2018, 14:36   #1642
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Re: Oceanvolt Hybrid Motor

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Originally Posted by OldMan View Post
This supports that DD is more efficient at (highway) cruise speed.
There's no debate that direct drive is more efficient if the engine providing the energy is a constant and is able to operate in it's most efficient range in either scenario.

The question is, can a serial hybrid be more efficient when you're not limited to a particular engine choice and have the ability to time-shift your energy needs (through the use of a battery) to always run your engine of choice at it's optimal efficiency?

I'm not sure what point you're trying to make about regeneration. Having "stop & go" traffic on a boat, would be bad for efficiency.

What's most silly about this thread is that there's literally billions of miles travelled with direct drive, parallel hybrid and series hybrid drivetrains today, and for some reason some people think none of it applies because the viscosity of the liquid travelled through is different. Or because they don't understand that regeneration is a way to arbitrage excess power or recover some of the power you put into acceleration, not a perpetual motion technology that allows you to travel further than one that wasn't having to accelerate frequently.

Would a parallel hybrid drivetrain on a catamaran be more efficient than a series hybrid even though your typical catamaran would necessitate two engines instead of the one engine of a series hybrid because the direct drive parallel hybrid would be so much more efficient? That's a definite maybe. You could get away with a smaller engine than a pure diesel since you presumably don't need more than a few hours of max power at a time. And you'd now have two generators on board, no need for a third. You'd still have a nice big battery bank you could share with luxuries. OTOH you shift the center of gravity aft.

I'm generally inclined to believe that a parallel hybrid is better suited to a monohull, and a series hybrid better suited to a multihull.
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Old 13-12-2018, 14:51   #1643
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Re: Oceanvolt Hybrid Motor

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There's no debate that direct drive is more efficient if the engine providing the energy is a constant and is able to operate in it's most efficient range in either scenario.

The question is, can a serial hybrid be more efficient when you're not limited to a particular engine choice and have the ability to time-shift your energy needs (through the use of a battery) to always run your engine of choice at it's optimal efficiency?

I'm not sure what point you're trying to make about regeneration. Having "stop & go" traffic on a boat, would be bad for efficiency.

What's most silly about this thread is that there's literally billions of miles travelled with direct drive, parallel hybrid and series hybrid drivetrains today, and for some reason some people think none of it applies because the viscosity of the liquid travelled through is different. Or because they don't understand that regeneration is a way to arbitrage excess power or recover some of the power you put into acceleration, not a perpetual motion technology that allows you to travel further than one that wasn't having to accelerate frequently.

Would a parallel hybrid drivetrain on a catamaran be more efficient than a series hybrid even though your typical catamaran would necessitate two engines instead of the one engine of a series hybrid because the direct drive parallel hybrid would be so much more efficient? That's a definite maybe. You could get away with a smaller engine than a pure diesel since you presumably don't need more than a few hours of max power at a time. And you'd now have two generators on board, no need for a third. You'd still have a nice big battery bank you could share with luxuries. OTOH you shift the center of gravity aft.

I'm generally inclined to believe that a parallel hybrid is better suited to a monohull, and a series hybrid better suited to a multihull.

Regen for city driving works, I have one. Not trying to draw parallels with regen for a sailboat, there are times it'll work, but a much narrower range than city driving.


The biggest issue for hybrid on a boat is cost. The ROI ain't there (yet), even with a new build.
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Old 13-12-2018, 15:25   #1644
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Re: Oceanvolt Hybrid Motor

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.. . .

The question is, can a serial hybrid be more efficient when you're not limited to a particular engine choice and have the ability to time-shift your energy needs (through the use of a battery) to always run your engine of choice at it's optimal efficiency?

I don't think that any possible savings from optimum engine regime could ever cover the cost of not only generating electricity and converting it back to mechanical power PLUS storing it in batteries, and then taking it back out of batteries. That's going to be very inefficient compared to mechanical drive.



This is not why hybrids store power in batteries. They store power in batteries in order to use cheap plug-in power, or to store power from regeneration (car hybrids), or to provide supplemental power during short term high demand situations.








I'm not sure what point you're trying to make about regeneration. Having "stop & go" traffic on a boat, would be bad for efficiency.

What's most silly about this thread is that there's literally billions of miles travelled with direct drive, parallel hybrid and series hybrid drivetrains today, and for some reason some people think none of it applies because the viscosity of the liquid travelled through is different. Or because they don't understand that regeneration is a way to arbitrage excess power or recover some of the power you put into acceleration, not a perpetual motion technology that allows you to travel further than one that wasn't having to accelerate frequently.[/QUOTE]


I don't understand your point here. Regeneration in a car is fantastic in city traffic because you have no choice but to stop and go, and without regeneration a ton of power is wasted through the brakes. That's the raison d'etre of Priuses and so forth. Boats don't have brakes so don't waste any energy this way, so nothing to recover. You can only recover energy during sailing when EITHER you are willing to take a speed hit OR you are sailing in conditions where you have excess sail power -- you are already hitting hull speed. Also, you need quite a lot of speed in order to produce useful power from regeneration -- totally different cases from Priuses which produce useful power constantly in city traffic.




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Would a parallel hybrid drivetrain on a catamaran be more efficient than a series hybrid even though your typical catamaran would necessitate two engines instead of the one engine of a series hybrid because the direct drive parallel hybrid would be so much more efficient?

I don't think you would do it that way. I would think you would have a single diesel driving a large generator plus direct drive of one screw. The second screw would have only an electric motor.


I suppose this could REALLY be more efficient than conventional drive -- maybe the unique case where the hybrid drive system would actually be lighter than the conventional system.


Direct drive of one screw would give you the option of skipping the conversion losses when motoring with just one screw.


Only problem with this is, as far as I understand (not a cat sailor personally), you don't always use the same screw -- depends on what direction the wind is coming from and what point of sail you are on. So you might get stuck motoring in series mode half the time. Or maybe the situation which you particularly need to use that side is less than 50%, because in a certain percentage of situations it doesn't matter.


In a mono -- yes, parallel for sure, or series/parallel which could be used either way. I could imagine that there could be some benefits of a switchable series/parallel system, where you might get some benefit say at very low speeds using the electrical motor in series mode.



But I still think lots of storage capacity and a use case making it possible to frequently plug into the grid, is probably the best use case for hybrid at this point.
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Old 14-12-2018, 01:48   #1645
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Re: Oceanvolt Hybrid Motor

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But it is braking....the power comes from somewhere, no magic! The regen prop in the water is drag on the boat. If the boat could use that power for faster speed, then yes, it's "braking".


SVReality reported a .5kt slowdown to realize 400W of regen.
I wouldn't call that "braking", more substracting part of the energy under sail to charge the batteries resulting in a "constant" slightly lower speed, yes.

In a car when you need to brake you need to brake, so capturing the that energy makes sense, but it never happens on a long period of time (except going down a slope), it is just recapturing a small part of the energy that you spent to gain speed, no external source of energy compared to a sailboat under sail.
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Old 14-12-2018, 05:31   #1646
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Re: Oceanvolt Hybrid Motor

And the braking regen is the main factor adding city mpg for land vehicles, counteracting the losses when departing from direct drive.

To me a hydro unit is just like wind or solar, just another input, all **very** minor compared to the energy most EP usage requires, and completely irrelevant to cruising under power for many hours a day, much less having reserve HP for when SHTF.
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Old 14-12-2018, 06:29   #1647
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Re: Oceanvolt Hybrid Motor

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And the braking regen is the main factor adding city mpg for land vehicles, counteracting the losses when departing from direct drive.

To me a hydro unit is just like wind or solar, just another input, all **very** minor compared to the energy most EP usage requires, and completely irrelevant to cruising under power for many hours a day, much less having reserve HP for when SHTF.

Regenerative braking is so effective in city driving that it probably justifies hybrid cars all by itself. Efficiency gains up to over 30% are reported in Teslas: https://electrek.co/2018/04/24/regen...-how-it-works/


Why is easy to understand if you think about it -- in city driving you are constantly burning energy to accelerate and then putting the brakes on, so a large part of the energy used is being blown out into the atmosphere via the brakes. I guess in really dense traffic probably well over half. Then on top of that you get to plug in and use cheap grid energy, further increasing efficiency, plus you might get special parking places and/or tax breaks!! In my opinion hybrid cars make perfect sense, and I would totally buy one if I drove much (which I don't).


Interestingly -- regenerative braking doesn't work nearly as well on electric bikes. Apparently, electric bikes are too slow to get that much useful power out of regenerative braking. I think regeneration on hybrid boats is a similar case -- the amount of power you can get out of them goes up exponentially with speed, so it works somewhat on really fast boats, but hardly at all on slow cruising boats. Something like wind generators I guess. And as noted you are dealing not with waste energy from brakes, but excess energy from the sails, which is not likely to be available nearly as consistently as braking energy from a hybrid car.
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Old 14-12-2018, 07:52   #1648
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Re: Oceanvolt Hybrid Motor

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Regenerative braking is so effective in city driving that it probably justifies hybrid cars all by itself. Efficiency gains up to over 30% are reported in Teslas: https://electrek.co/2018/04/24/regen...-how-it-works/
No, that's a Tesla marketing site. The writer makes a living off Tesla referrals.

Here's the snippet you're referring to:
Quote:
Model S drivers have reported recapturing as much as 32% of their total energy use while driving up and then back downhill. This would effectively increase a 100 mile car’s range to 132 miles, for example.
The first sentence is fine. If I spend 1,000wh going up a hill, and then re-capture 320wh going down the other side my total wh is 680wh. Nothing wrong with that claim. But that makes regeneration (when using potential energy from a hill-climb, so the best case scenario!) 32% efficient. Nowhere near 70% they took the Tesla marketing guy's word at. Because unlike braking, coasting down a hill gets to recover (some of) the extra energy you spent climbing the hill as potential energy. In braking you only get to recapture the energy you spent on acceleration, not distance travelled.

This is how a gravity battery (pumped storage being a popular form) works.

Anyways, the second sentence is total and complete nonsense. If going up and down hills extended range that would mean Tesla has managed to create a perpetual motion machine.

I guarantee that traveling the same distance over perfectly flat land would have expended less energy overall with no regeneration at all. I've linked to a thread where people manage to get over 90MPG out of a non-plugin Prius, mostly by avoiding braking whenever possible, keeping to average speeds under 20MPH (easier to avoid braking, less drag), RPMs low (more efficient fuel burn, less energy loss to friction or heat) and drafting, etc.

I've owned a Nissan Leaf, now a Chevy Bolt and my wife drives a Chrysler Pacifica PHEV. All three of those have regenerative braking. My Bolt has a realtime display for power in/out. It's much more efficient to avoid braking entirely. Getting to 45MPH might consume 20kW for 10 seconds. That's 56wh. Traveling 1 mile on flat land takes about 200wh. Using regenerative braking alone (no friction brakes) to come to a stop takes about 5 seconds, will peak around 30kW for a fairly quick stop, and drop in an inverse logarithmic fashion precipitously from there. The average over the entire braking event is probably under 10kW, but let's use that number anyways. That's about 14wh recovered. The more braking events you add to cover the same distance, the more energy it covering that distance consumes. Because regenerative braking isn't 100% efficient. Im my contrived single-braking event per mile scenario I could turn it off completely and only lose about 5.5%. Hills would increase that number significantly, but the energy required to travel up them would increase even more. Avoid hills.

Modern lithium based hybrids (older ones used NiMH batteries) with much more efficient chargers only manage to match highway efficiency (sometimes) even though they don't have to contend with highway drag. The RAM eTorque system has no regeneration ability and still manages to increase power while improving economy approximately 10% with only a 500wh battery.

Here is a Tesla hyper-miler's tips: https://cleantechnica.com/2016/09/26...-driver-world/

Quote:
It is more efficient to use mass going down the hill than using regen because regen is only 30–50% efficient (sic: compared to using momentum).
So what does this have to do with boats? Boats don't sit in stop & go traffic. They are at an inherent advantage compared to a car in an urban setting.

People on this forum need to stop using regenerative braking as a reason to justify why hybrids couldn't be efficient on boats. Especially with zero evidence beyond unsourced assertions that represent the opposite of demonstrated practice. It's a clear misunderstanding of what regenerative braking is and isn't.

Boats are at an advantage, not a disadvantage on this count. That's as hard a fact as you're going to find in this entire 110 page thread. I hope that we can all agree on that by this point at least.
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Old 14-12-2018, 08:18   #1649
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Re: Oceanvolt Hybrid Motor

The need for braking is an inherent inefficiency unique to land vehicles.

Regenerative braking is restoring energy into land EP systems that otherwise is lost to that inefficiency.

Boats do not suffer from that particular inefficiency.

Therefore EP does not give them the same level of efficiency **improvement** that it delivers on land.
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Old 14-12-2018, 08:46   #1650
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Re: Oceanvolt Hybrid Motor

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No, that's a Tesla marketing site. The writer makes a living off Tesla referrals.

Here's the snippet you're referring to:

The first sentence is fine. If I spend 1,000wh going up a hill, and then re-capture 320wh going down the other side my total wh is 680wh. Nothing wrong with that claim. But that makes regeneration (when using potential energy from a hill-climb, so the best case scenario!) 32% efficient. Nowhere near 70% they took the Tesla marketing guy's word at. Because unlike braking, coasting down a hill gets to recover (some of) the extra energy you spent climbing the hill as potential energy. In braking you only get to recapture the energy you spent on acceleration, not distance travelled.

This is how a gravity battery (pumped storage being a popular form) works.

Anyways, the second sentence is total and complete nonsense. If going up and down hills extended range that would mean Tesla has managed to create a perpetual motion machine.

I guarantee that traveling the same distance over perfectly flat land would have expended less energy overall with no regeneration at all. . . . .

That makes perfect sense. Thanks.


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Originally Posted by ssmoot View Post
People on this forum need to stop using regenerative braking as a reason to justify why hybrids couldn't be efficient on boats. Especially with zero evidence beyond unsourced assertions that represent the opposite of demonstrated practice. It's a clear misunderstanding of what regenerative braking is and isn't.

Has anyone said that? I think there's a problem of logic here -- I think people have said merely that you can't prove that hybrid boats must be efficient, just because hybrid cars are efficient -- hybrid cars have regenerative braking, a big advantage which boats don't have. This doesn't mean, by itself, that hybrid boats can't be efficient (there are other facts supporting that proposition) -- it just means you can't use the efficiency of hybrid cars as your evidence of the efficiency of hybrid boats.






Quote:
Originally Posted by ssmoot View Post
Boats are at an advantage, not a disadvantage on this count. That's as hard a fact as you're going to find in this entire 110 page thread. I hope that we can all agree on that by this point at least.

Indeed. So it's a problem which cars have, which hybrid drive with regenerative braking partially solves. A significant hybrid benefit which does not apply to boats.



Quote:
Originally Posted by john61ct View Post
The need for braking is an inherent inefficiency unique to land vehicles.

Regenerative braking is restoring energy into land EP systems that otherwise is lost to that inefficiency.

Boats do not suffer from that particular inefficiency.

Therefore EP does not give them the same level of efficiency **improvement** that it delivers on land.

Indeed.
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