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Old 25-05-2019, 05:11   #1891
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Re: Oceanvolt Hybrid Motor

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Originally Posted by BigBeakie View Post
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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Should be interesting indeed ! When will you have your OV installed ? And is this set up a temporary set up or meant to be kept like that ?

By the way, can the servoprop be fitted to an AXC 20 or only on the SD 15 ?
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Old 25-05-2019, 05:57   #1892
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Re: Oceanvolt Hybrid Motor

Well the launch is probably 6 months away as we've just taken over the build ourselves and there is some setup to do in the new factory, but I expect this " one of each" to work out quite well.

The Servoprop is not currently available on the AXC series, but I believe it will be at some point.

By the way, both the AXC20 and the Beta 45T are shaft drive and both have exactly the same propeller, Flexofold 16" x 12pitch, so this will be, to my knowledge the first true, side by side (literally&#128514 test of diesel vs electric in the same boat.

Predictions anyone?


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Old 25-05-2019, 07:02   #1893
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Re: Oceanvolt Hybrid Motor

Quote:
Originally Posted by BigBeakie View Post
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.[emoji106]


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I wouldnít bother.
It is true that there is a ďsweet spotĒ for any engine, one set RPM and torque that it is itís its most efficient for delivering power.
However this sweet spot never occurs at the hulls sweet spot, and hull drag is far more relevant to fuel consumption over distance than the engines sweet spot.

If desired itís actually easy to prop for the engines sweet spot, particularly if you have a controllable pitch propeller. However you would need a torque meter, and Iíve never heard of one on a cruising boat.

The efficiency problem is actually very simple, itís most efficient to use mechanical force directly, than it is to convert it to another force, and then use that other force, whether it be compressed fluids, a gas or electric.
Locomotives are an excellent example of why a hybrid diesel / electric drive train is sometimes more desirable than a direct drive, itís less efficient and there have been direct drive Diesel locomotives, but they have all been mechanically complex. Something that the hybrid drive overcomes.

But if you chose, there are many fuel flow meters, better ones couple into the NMEA bus and give you range and MPG etc.
However a Diesel engine requires two fuel flow meters because the return fuel has to be subtracted from the supply fuel, and therefore isnít as inexpensive a a gas engine one.

To be really significant though they need to be identical engines, at identical power settings.
The power setting is what is going to be hard to determine, cause you need to know how much power is being produced, and you canít get that with just RPM. That is why you need to have a torque meter.
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Old 25-05-2019, 07:05   #1894
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Re: Oceanvolt Hybrid Motor

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Originally Posted by BigBeakie View Post
Well the launch is probably 6 months away as we've just taken over the build ourselves and there is some setup to do in the new factory, but I expect this " one of each" to work out quite well.

The Servoprop is not currently available on the AXC series, but I believe it will be at some point.

By the way, both the AXC20 and the Beta 45T are shaft drive and both have exactly the same propeller, Flexofold 16" x 12pitch, so this will be, to my knowledge the first true, side by side (literally&#128514 test of diesel vs electric in the same boat.

Predictions anyone?


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Indeed that should provide some key data !

Was looking up threa and you were mentioning 2 sd15 with servoprops I think, and a 16kw dc genset, so you have changed your mind since then ? For what reasons ?
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Old 25-05-2019, 07:06   #1895
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Oceanvolt Hybrid Motor

You may be able to get a decent test of each drive system by determining RPM required by each engine in flat water, no wind or current.
Then run each engine at that hull speed with the other engine off and compare fuel consumption.
My prediction is if itís a very well matched generator / electric motor combination, it will be 10% less efficient than the direct drive system.
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Old 25-05-2019, 07:10   #1896
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Re: Oceanvolt Hybrid Motor

A hybrid automobile at a set highway speed should be significantly less efficient than its mechanically driven brother.
Itís not, not because of the efficiency of the electric drive, itís because the electric drive enables a different type of internal combustion engine that is much more efficient than an Otto cycle engine.

Unfortunately, we donít see a similar advantage in boats
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Old 25-05-2019, 07:13   #1897
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Re: Oceanvolt Hybrid Motor

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However, can it be said that a diesel on a sailboat typically does not operate at its top efficiency, contrary to a DC generator ?
Cruising boat diesels actually aren't typically that far off from the sweet spot unless wildly inappropriate drive-trains are used. If they were claiming 5-10% improvement...maybe even 20%, I might consider the possibility that better matching of diesel efficiency to load could be in play. 200% improvement, is just silly talk. The standard cruising sailboat isn't running anywhere close to that inefficient.

Of course, better diesel efficiency is typically balanced out by losses converting to electric and then back to mechanical, so even the 5-10% improvement is unlikely. Given the wild unsubstantiated claims oceanvolt has made to date, I'm betting its a significant loss in efficiency.
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Old 25-05-2019, 07:37   #1898
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Re: Oceanvolt Hybrid Motor

A64pilot - noted on the conditions for the fuel flow meter needing to account for the nett used diesel, good point, thanks.

Yvest- there were multiple reasons for our change from 2 x Servoprop Sd15's to 1 x AXC20's and 1 x diesel. The most important was that we revisited our thinking on adverse conditions and cruising grounds. We now intend to do some cruising in somewhat higher latitudes ( not really high latitudes) and upon review of pilot charts of those regions and our wind resistance analysis, and in conversation with experienced cruisers of those areas, we felt that for extended motoring, feeding two electrics from the 16kW DC genset, ie 7.5kW each continuous, was just a bit underpowered for conditions when sailing room was restricted and high winds could present lee shore risk. If we had purchased a 30kW DC genset, our decision would have been different, but we had the 16kW genset already.
We thought it prudent to feed one electric at least 75% power from the genset, ( instead of two at 50% power maximum) so that pointed us towards the AXC20. And it is shaft vs saildrive, which we also preferred if we were going with one diesel shaft drive. We also viewed the AXC as their most robust, industrial design/spec motor that is going into use for ferries and other commercial applications.
The lower regen numbers was the only downside of the decision, but the tradeoff was worth it, since we have alot of solar.

So now we expect to use the AXC20 almost all the time for most motoring situations, and have the 45HP diesel at the ready if things get hairy.


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Old 25-05-2019, 08:45   #1899
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Re: Oceanvolt Hybrid Motor

I think your smart for not going full hybrid, reliability is pretty well known as are parts and mechanical expertise for a straight mechanical system.
Maybe less so for hybrid, but a back up is good, many boats of course get by with only one engine and propulsion system, so worst case with the hybrid, I think you just join the ranks of us single propulsion guys.

Regen isnít very likely I donít think, it assumes of course excess propulsion from the sail is available, or you will accept a significantly slower cruise speed, neither of which I think is very likely.
The rest of the sailing world is spending Billions on speed, and your going to give it away? Maybe sometimes, but not very often I donít think.


To compare the sweet spots effectiveness, what your looking for is called BSFC or brake specific fuel consumption which will show exactly how efficient an engine is at producing power.
Itís actually pretty flat once you assume operation in the middle 1/3 or the RPM band, where most of us do operate, there are no big gains.
Turbos as they harvest otherwise waste heat do increase efficiency some, but not as much as you would hope, common rail again some, but not as much as you would hope. A turbos main efficiency boost may come at allowing a smaller, lighter engine to do the same job, which may mean a smaller, lighter boat.

Way back in the 70ís a study was commissioned that showed that if you remove the spare tire from a vehicle in the design phase, you saved a 1/4 ton of weight. The removal meant a slightly smaller car, which means a smaller engine, transmission, brakes, etc, it snowballs until a 1/4 Ton is saved.
Yet we still drive around with spare tires .
The biggest significant difference in fuel consumption that you can control is simply speed, slow down and burn far less fuel, and or motorsail.
A huge amount of fuel can be saved in my opinion by having a good light wind sail available.
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Old 25-05-2019, 08:46   #1900
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Re: Oceanvolt Hybrid Motor

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You may be able to get a decent test of each drive system by determining RPM required by each engine in flat water, no wind or current.
Then run each engine at that hull speed with the other engine off and compare fuel consumption.
My prediction is if it’s a very well matched generator / electric motor combination, it will be 10% less efficient than the direct drive system.
The issue with this test is that the DC generator may also charge the batteries when running (most probably will), so the test should start at some batteries level with the genset on, continue for a while, then a some point stop the genset and continue with the Electric motor at same RPM untill the batteries are back to their starting point (provided no other loads on the batteries in the process), not that easy...

But I would also bet on slightly less efficiency.
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Old 25-05-2019, 11:12   #1901
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Re: Oceanvolt Hybrid Motor

Or the reverse, in which case the electric motor (and the boat) should be stopped, and the DC gen left running up to the point of the batteries being at the starting point .
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Old 25-05-2019, 14:48   #1902
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Re: Oceanvolt Hybrid Motor

Some interesting thoughts from someone who has gone to electric propulsion on a catamaran.

Starts at 18:33

https://youtu.be/o6kOvjS1ytE

AND

Starts at 13:45

https://youtu.be/nchKhM_TxYk
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Old 25-05-2019, 17:11   #1903
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Re: Oceanvolt Hybrid Motor

The test I was planning on doing is to keep it simple. To run the electric at 15kW from batteries which is the maximum continuous charge from the 16kW genset, so we are putting full genset output into propulsion only. Note boat speed in no wind no current conditions and run for set time, say an hour if possible, and note distance covered and fuel used.

Then find rpm on the Beta that replicates the same boat speed, and run same time at those RPM for same distance, and note fuel used.


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Old 25-05-2019, 17:35   #1904
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Re: Oceanvolt Hybrid Motor

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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 ..
Ain't going to happen. The engine powering their genny will output power as efficiently as a diesel operating a propeller, but then the generator power has to be converted to DC to charge the batteries and there will be inefficiencies in the power conversion and the resistance of the batteries and then the DC power from the batteries has to be inverted to operate the Oceanvolt motors. The Oceanvolt motors are low voltage, high amperage machines hence from an electric vehicle systems perspective they are comparatively inefficient versus high voltage machines on vehicles.

Now if one was to top up a large bank with shore power then of course that stored energy could be drawn upon to motor a certain distance and not require hybrid drive to regenerate power for the batteries. But you will not motor long before consuming the power in the batter bank, e.g, say an hour or less.

Cry Bull.
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Old 26-05-2019, 03:16   #1905
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Oceanvolt Hybrid Motor

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Originally Posted by BigBeakie View Post
The test I was planning on doing is to keep it simple. To run the electric at 15kW from batteries which is the maximum continuous charge from the 16kW genset, so we are putting full genset output into propulsion only. Note boat speed in no wind no current conditions and run for set time, say an hour if possible, and note distance covered and fuel used.

Then find rpm on the Beta that replicates the same boat speed, and run same time at those RPM for same distance, and note fuel used.


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Lots of variables there. Transmission ratio, prop dia and pitch are just a few.

Itís unlikely the mechanical drive and electric drive will be optimized with the same propeller.

The real test will be which system has the most hours on it after a couple years full time cruising.
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