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Old 21-01-2019, 05:04   #1876
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Re: Oceanvolt Hybrid Motor

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Originally Posted by Q Xopa View Post
Ok no argument from me. Although they are termed DC Gens. I did say the definition is murkey. But is there some relevance to that declaration?
There is relevance in that the perceived advantage of DC generators over AC is that some believe they are gaining efficiency by eliminating the conversion from AC to DC. That is not so. And if a boat has any large AC consumers such as water maker or cooking then there are 2 conversions (AC->DC->AC) with a DC generator and no conversions with an AC generator. So the advantages of DC are dependent on the use case. But there seems to be a universal belief that DC generator is always better for efficiency and that is not always the case. In fact, I suspect it is rarely the case.

EP is targeted to the desire for making life on the water more pleasant and simpler. And the desire is so great that wishful thinking begets "engineering facts" that are simply not true. I believe EP is great but facts matter. I also know it is not more efficient than traditional diesel propulsion on typical cruising boats. It cannot eliminate the need to carry diesel fuel on board for 90% of long distance cruisers. It is massively more complex than traditional systems. EP also has many desirable features. It can save a little on fuel for a typical downwind passage. It can enable carrying lots of convenient electrical appliances. It is kewl to pull out of the slip early in the morning and wake no one. It satisfies the geek in some cruisers, and let's face it many cruisers are geeks. I just don't like seeing cruisers become disillusioned because EP is not the tech that will let us thumb our noses as we pass the fuel dock after a long passage. The EP proponents should tout the many other advantages but invariably the first benefit I hear from would be EP users is "hey I found a way to get diesel off my boat, EP+solar+regen will power my cruising lifestyle". If you live like the Pardey's then yes. But not so for most of us.
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Old 21-01-2019, 06:55   #1877
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Re: Oceanvolt Hybrid Motor

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By going with 16% panels your savings are marginal and you’ve handicapped your options to expand. Wholesale prices on similar-wattage panels I can find off-hand are pretty similar unless you narrow your scope to North American branded panels. Anyways, that seems like a pretty big negative to me.

Your commentary on EP aside, I want every watt I can find. Power is luxury. Power is convenience. Power gives you flexibility. I want fresh water, hot water, laundry, an induction hob and I’ll take as much as I can get.

I’ll try to get as much as I can without having to run a noisy, polluting engine to get it. Solar panels are the gift that keeps on giving. That 3kW array, using your own estimated average output, will put out 20-megawatt-hours in 5 years time. That’d be a savings of several thousand gallons of fuel for a generator, and you’d probably not be far off from needing a new generator by the end of it. Which makes solar the lowest cost option by a mile.

The good news is I decide the needs for my boat and you decide the needs for your boat. I have 15 years cruising experience, so I pretty much know what I want.


My only goal, like others on this thread, is to inject some reality into the conversation.
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Old 21-01-2019, 07:01   #1878
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
There is relevance in that the perceived advantage of DC generators over AC is that some believe they are gaining efficiency by eliminating the conversion from AC to DC. That is not so. And if a boat has any large AC consumers such as water maker or cooking then there are 2 conversions (AC->DC->AC) with a DC generator and no conversions with an AC generator. So the advantages of DC are dependent on the use case. But there seems to be a universal belief that DC generator is always better for efficiency and that is not always the case. In fact, I suspect it is rarely the case.
Facts are strange, often inconvenient and seemingly illogical things, aren't they?

The fact is high voltage permanent magnet generators are much more efficient than synchronous induction ones. As a matter of fact, they are enough more efficient to more than compensate for the AC-DC conversion - or even the AC-DC-AC conversion.

Not running at synchronous speeds means the generator can run at more efficient power point in most cases - and that the generator can be smaller for the same peak output.

Compare the Polar Power 8340VP-40 with a Northern Lights M844DW3.


Polar power is using a 1.5 L 4 cylinder Volvo Penta 40 HP motor and a permanent magnet generator with an 85-94% efficiency. This gives them a peak efficiency of 290 g/kWh in DC and a weight of 180 kg outputting up to 20 kW of DC power.

The M844W3 is a 2.2 ltr 4 cylinder, attached to a conventional air cooled induction generator. At 1800 rpm, it uses 6.50 lph outputting 16 kW. Using 832 g/l for diesel, that gives 338 g/kWh at full power. At half power, it's burning 3.9 lph and only producing 8 kW - for 405 g/kWh. And it weighs 440 kg without the sound shield...

I can certainly find plenty inverters that claim better than 86% (290/338) efficiency to make the AC-DC-AC trip more efficient than the straight AC case - but the fact is most folks never load a generator to anywhere near 100%, so the AC generator efficiency will be much less than that, whereas the EP use case means that the DC generator can be run at peak efficiency at nearly all times - the situations where there's an extended propulsion load beyond battery range needing more power being the lone exception.
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Old 21-01-2019, 08:14   #1879
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Re: Oceanvolt Hybrid Motor

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Originally Posted by saghost View Post
whereas the EP use case means that the DC generator can be run at peak efficiency at nearly all times
First, thanks for the comment. I've been curious about exactly that comparison, but didn't feel like doing the grams conversion myself. So you've done some of the homework I was too lazy for.

I am a bit lost on your comment here though. In an EP scenario, I would assume you would run either generator at peak efficiency at all times, directing any excess to your batteries, and then just shutting off the generator until you hit 20% SoC or so again.

For the Polar Power I think I recall that being around 16kW, but don't quote me on that. I'm not sure if the 290g/kW number is when tuned for peak output (20kW) or max efficiency (16kW)?

Where you lose me is talking about partial loads for the AC generator being less efficient though. I can't think of a good reason to run the generator at anything less than 100% assuming that's where it's most efficient.

Either way it's nice to see that the Polar Power generator is in general more efficient. Their choice of engine is a bit off-putting since it seems like the complaints about the Volvo exhaust elbow corrosion are near universal. But even so.
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Old 21-01-2019, 08:22   #1880
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
advantage of DC generators over AC
depends on the use case, owner's design preferences.

> large AC consumers such as water maker or cooking then there are 2 conversions (AC->DC->AC) with a DC generator and no conversions with an AC generator.

that assumes the genset is running to feed the consumers. Otherwise you're converting to charge the bank, then inverting back later.

If you have no AC consumers, or only a few low-current ones fed off the bank, everything changes.

> EP is targeted to the desire for making life on the water more pleasant and simpler.

I doubt that. Its purpose is to move the boat. Ancillary benefits toward House loads are ancillary, and only realized from generating the electricity aboard.

The **marketing** USP is the dubious belief that EP on a boat can be green. IMO that's just for status, virtue signaling. To be real, more than single digit % contribution from non-fossil-fuel, requires bespoke designed boats and huge **sacrifices** in comfort and convenience.

The economy and simplicity factors went out the window before even trying to be truly green.

> It can enable carrying lots of convenient electrical appliances.

That is a downside IMO

> "hey I found a way to get diesel off my boat, EP+solar+regen will power my cruising lifestyle". If you live like the Pardey's then yes. But not so for most of us.

Not even then, and the truly green Pardey lifestyle is inherently antithetical to even considering such complex, expensive and inefficient tech.
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Old 21-01-2019, 08:32   #1881
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Re: Oceanvolt Hybrid Motor

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Originally Posted by ssmoot View Post
First, thanks for the comment. I've been curious about exactly that comparison, but didn't feel like doing the grams conversion myself. So you've done some of the homework I was too lazy for.

I am a bit lost on your comment here though. In an EP scenario, I would assume you would run either generator at peak efficiency at all times, directing any excess to your batteries, and then just shutting off the generator until you hit 20% SoC or so again.
Yes, exactly.

Unless you needed to supply an average power that's more than the generator's peak efficiency power for longer than the battery can make up the difference - running the drive motors wide open running away from a storm for a couple days or something. That's what I meant.


Quote:
For the Polar Power I think I recall that being around 16kW, but don't quote me on that. I'm not sure if the 290g/kW number is when tuned for peak output (20kW) or max efficiency (16kW)?

Where you lose me is talking about partial loads for the AC generator being less efficient though. I can't think of a good reason to run the generator at anything less than 100% assuming that's where it's most efficient.

Either way it's nice to see that the Polar Power generator is in general more efficient. Their choice of engine is a bit off-putting since it seems like the complaints about the Volvo exhaust elbow corrosion are near universal. But even so.
Because the AC generator is responding to loads directly. It has to hold 1800 rpm to produce 60 Hz power, and the big loads - air conditioning, watermaker, etc cycle on and off. What's more, folks don't want to schedule which one load they'll run at a given time, so they usually size the AC generator so it can handle most or all of the loads simultaneously - which means that unless everything actually is running at the same time, the generator is running at a fraction of its total output capacity.

In theory you could have big battery chargers for the house batteries that respond to the other loads on the generator and eat up the rest of the available power if the house pack was big enough, but I've never seen such a thing described - instead, they become one more thing the generator is sized big enough to cover that may or may not be running at the time.
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Old 21-01-2019, 08:48   #1882
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Re: Oceanvolt Hybrid Motor

For me, the genny is run **only** for

charging the bank
high gph watermaker, freezing charge plates
if EP, then propulsion

maybe occasionally supporting heavy loads like an air compressor, welding, winch or windlass

but no aircon, no electric kitchen, heat-producing appliances, laundry, dishwashers etc on my boat thanks
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Old 21-01-2019, 10:16   #1883
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by transmitterdan View Post
There is relevance in that the perceived advantage of DC generators over AC is that some believe they are gaining efficiency by eliminating the conversion from AC to DC. That is not so. And if a boat has any large AC consumers such as water maker or cooking then there are 2 conversions (AC->DC->AC) with a DC generator and no conversions with an AC generator. So the advantages of DC are dependent on the use case. But there seems to be a universal belief that DC generator is always better for efficiency and that is not always the case. In fact, I suspect it is rarely the case.

EP is targeted to the desire for making life on the water more pleasant and simpler. And the desire is so great that wishful thinking begets "engineering facts" that are simply not true. I believe EP is great but facts matter. I also know it is not more efficient than traditional diesel propulsion on typical cruising boats. It cannot eliminate the need to carry diesel fuel on board for 90% of long distance cruisers. It is massively more complex than traditional systems. EP also has many desirable features. It can save a little on fuel for a typical downwind passage. It can enable carrying lots of convenient electrical appliances. It is kewl to pull out of the slip early in the morning and wake no one. It satisfies the geek in some cruisers, and let's face it many cruisers are geeks. I just don't like seeing cruisers become disillusioned because EP is not the tech that will let us thumb our noses as we pass the fuel dock after a long passage. The EP proponents should tout the many other advantages but invariably the first benefit I hear from would be EP users is "hey I found a way to get diesel off my boat, EP+solar+regen will power my cruising lifestyle". If you live like the Pardey's then yes. But not so for most of us.
Ok, you consider the relevent factor to be conversion. I do get your point. And indeed agree with the fact there are losses in extra conversions. Thats plain to see, no arguments from me on your point.

I can only speak for myself, but thats not my perception of why a 'DC gen' can be more efficient. Obviously I am not 'Universal'. In fact most people touting DC gens seem to understand this too.

However as I was attempting to say before, but my bad, not very successfully, that is not the predominating factor in why 'DC gens' or for that matter AC Invertor gens can operate more efficiently is load averaging.

This of course depends on usage patterns. If a resonably constant load, in the 2/3rds of max rated capacity was the norm then yes you are correct that there would be little to no benefit to a DC Gen.

However this seems to be rarely the case. Hence the success of Inverter 'suit case' style generators. So its not a case of being pro DC Gens, although they do work quite well for many cases.

The same applies with Inverter AC Gens, ie Honda EU2000i's etc, which operate on the same principle (mostly) of matching loads to RPMs.

This is my point- RPMs matched to Loads. Instead of the traditional AC gen screaming away at high RPM with often light loading.

Honda 2000i 's are certainly the right end of the price scale.

However 'DC gens' are diesel, which of course has some efficiency advantage, and generally bigger capacity than Honda 2000i's.
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Old 24-05-2019, 20:13   #1884
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Re: Oceanvolt Hybrid Motor

Oceanvolt published some white papers on their site (support->download), where they claim (range whitepaper) :
"In a typical real-life scenario, owners notice that they are able to motor roughly three times further with the same amount of fuel, when using the generator and electric engines, compared to only diesels. This is exactly the same principle that is applied in today’s shipping industry – all modern ships have diesel generators powering electric engines due to this efficiency gain."
Some real data would be nice to have ..
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Old 24-05-2019, 21:21   #1885
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Re: Oceanvolt Hybrid Motor

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Originally Posted by yvest View Post
Oceanvolt published some white papers on their site (support->download), where they claim (range whitepaper) :
"In a typical real-life scenario, owners notice that they are able to motor roughly three times further with the same amount of fuel, when using the generator and electric engines, compared to only diesels. This is exactly the same principle that is applied in today’s shipping industry – all modern ships have diesel generators powering electric engines due to this efficiency gain."
Some real data would be nice to have ..
Seems like they are expanding the fantasy! THREE times the fuel economy???

Now that's REALLY hard to support or to believe.

Good grief.

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Old 24-05-2019, 21:59   #1886
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by yvest View Post
Oceanvolt published some white papers on their site (support->download), where they claim (range whitepaper) :
"In a typical real-life scenario, owners notice that they are able to motor roughly three times further with the same amount of fuel, when using the generator and electric engines, compared to only diesels. This is exactly the same principle that is applied in today’s shipping industry – all modern ships have diesel generators powering electric engines due to this efficiency gain."
Some real data would be nice to have ..

Magic horsepower again. It's scientically/physically impossible. Making a claim like that just confirms that you can't put any reliance on any of their other claims.
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Old 24-05-2019, 22:00   #1887
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Re: Oceanvolt Hybrid Motor

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. This is exactly the same principle that is applied in today’s shipping industry – all modern ships have diesel generators powering electric engines due to this efficiency gain."
.
This is wrong on many levels.

Most modern ships still use direct drive diesel. They run for days at steady speed and fuel efficiency is their primary consideration.

Some cruise ships, ferries and military use diesel/electric systems. This is not due to efficiency but flexibility and maneuverability considerations that outweigh efficiency. Example: If a cruise ship has a 10hr port stop and the tug boats are held up, the passengers will be angry and want refunds if they miss their tour. By using diesel/electric pod drives, they can eliminate the need for tugs.

The advantage of diesel/electric in large shipping is it acts as a transmission capable of handling massive amounts of power with great precision.

Once again, OceanVolts marketing department has only the loosest grasp of how physics works.
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Old 24-05-2019, 23:42   #1888
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Re: Oceanvolt Hybrid Motor

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This is wrong on many levels.

Most modern ships still use direct drive diesel. They run for days at steady speed and fuel efficiency is their primary consideration.

Some cruise ships, ferries and military use diesel/electric systems. This is not due to efficiency but flexibility and maneuverability considerations that outweigh efficiency. Example: If a cruise ship has a 10hr port stop and the tug boats are held up, the passengers will be angry and want refunds if they miss their tour. By using diesel/electric pod drives, they can eliminate the need for tugs.

The advantage of diesel/electric in large shipping is it acts as a transmission capable of handling massive amounts of power with great precision.

Once again, OceanVolts marketing department has only the loosest grasp of how physics works.
Indeed agree that they are not doing themselves a favor with such wrong statements (plus in one of the paper diagram they have "kW/h" as unit instead of kW, kind of a shame ...)

However, can it be said that a diesel on a sailboat typically does not operate at its top efficiency, contrary to a DC generator ?
The root of their claim :
Quote:
A key driver for hybrid yachts is the fact that the generator is much more fuel efficient than a diesel engine. Fuel efficiency comes from the fact that the generator is built to operate at an optimum 2800-3200 RPM range. A diesel engine in a boat usually runs at 1500-1800 RPM, which is a very inefficient operating speed for a diesel motor. In a typical real-life scenario, owners notice that they are able to motor roughly three times further with the same amount of fuel, when using the generator and electric engines, compared to only diesels.
note : below direct link to the paper if it works :
https://www.dropbox.com/s/825qds4co9...lsion.pdf?dl=0
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Old 25-05-2019, 01:12   #1889
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by yvest View Post
Indeed agree that they are not doing themselves a favor with such wrong statements (plus in one of the paper diagram they have "kW/h" as unit instead of kW, kind of a shame ...)

However, can it be said that a diesel on a sailboat typically does not operate at its top efficiency, contrary to a DC generator ?
The root of their claim :


note : below direct link to the paper if it works :
https://www.dropbox.com/s/825qds4co9...lsion.pdf?dl=0



"A key driver for hybrid yachts is the fact that the generator is much more fuel efficient than a diesel engine. Fuel efficiency comes from the fact that the generator is built to operate at an optimum 2800-3200 RPM range. A diesel engine in a boat usually runs at 1500-1800 RPM, which is a very inefficient operating speed for a diesel motor. In a typical real-life scenario, owners notice that they are able to motor roughly three times further with the same amount of fuel, when using the generator and electric engines, compared to only diesels. This is exactly the same principle that is applied in today’s shipping industry – all modern ships have diesel generators powering electric engines due to this efficiency gain."

What a load of utter nonsense! Wrong on every possible level.



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Old 25-05-2019, 03:10   #1890
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Re: Oceanvolt Hybrid Motor

I will be able to test this statement on fuel efficiency if we get a fuel flow meter hooked up to both our Eniquest 16kW DC genset driving the OV AXC 20 in port hull, and the Beta 45T in our starboard hull. Should be interesting.

I'm not really sure which fuel flow system to to, let alone how to hook it up, so any suggestions will be gratefully accepted.👍


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