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Old 09-12-2018, 06:45   #1456
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Re: Oceanvolt Hybrid Motor

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Originally Posted by Pete7 View Post
So 2 out of the last 10 start ups have used 3/4 revs, the rest less have 1/2 revs. I need to move into a marina for power and water for jobs or cleaning which we have been doing quite a bit of during that last couple of months.
Exactly.

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What I am not going to do is tear out a perfectly good diesel and replace it with lots of expensive batteries and an electric motor costing ???? and seriously reduce the yachts range.
You are right, no one in their right mind would replace a less efficient system with a more efficient system for a much larger cost. The ROI is not there and is also a completely different discussion than what I was saying (Magic HP and Efficiency).

I don't think anyone in this post is suggesting people rip out good working equipment, I think the post started with a new build. And for a new build, people are thinking about new ways of accomplishing their goals.
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Old 09-12-2018, 06:52   #1457
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Re: Oceanvolt Hybrid Motor

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Not sure this is true. An electric motor could be recieving huge current at zero rpm.

And also with no load at maximum rpm.
Huge current at zero rpm? Only if buried or bound by rope, and throttle pegged. I'm not sure how this is relevant.

No load at max rpm? Nope, not possible, even if you tried counting driveline friction/drag you'd have to admit that those count as loads.
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Old 09-12-2018, 06:58   #1458
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Re: Oceanvolt Hybrid Motor

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There is no chance that an ordinary sized yacht even with LifePO4 could power along for 11 or 12 hours at cruising speed.

Yes I agree, spilling diesel on the boat or me, the fumes if the wind is from astern etc, but any alternative is going to have to be cost effective if we want wide spread adoption.
"no chance"? Don't count on it, one thing about technology, by definition it is change. And the only thing that stays constant in the world... is change.

Your point about cost effective is right on. Right now the technology folks are profit taking from early adopters. Once their sales are slower, they'll adjust to reach more buyers.
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Old 09-12-2018, 08:18   #1459
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Re: Oceanvolt Hybrid Motor

Interestingly we met our first electric powered yacht in August. We were rafted 4 or 5 deep in Weymouth harbour, rafting being a very common occurrence in NW Europe.

The elderly owner of a small 25-26ft old wooden sloop let everyone know he wanted to leave. So all hands on deck as we untied the outer yachts so he could move. Not a problem we all mucked in together moving yachts about. The sloop's owner was Dutch and had spent the whole summer sailing from Holland down to the Scilly Isles and was now on his way home. He untied his yacht and pushed off. Slightly alarmed I was about to grab the boat hook fearing it all going pear shaped if his engine didn't start. He then turned a rotary switch and the sloop quietly slipped out of the harbour with its electric drive. He had a couple of solar panels perhaps 150w, but I doubt any fancy batteries.

The one advantage he really had was time. He could afford to wait in harbour or at anchor until the weather and tide turned in his favour. A great lifestyle and very much on the lines of a £200 millionaire.

https://www.woodenwidget.com/milionaire.htm

Sadly it will be another decade for us.

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Old 09-12-2018, 10:49   #1460
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Re: Oceanvolt Hybrid Motor

The hulls designed for EP and mounting massive panel watts will be what makes the long-distance powered cruising off solar practical.

Meantime doing conversions from existing designs to EP is just putting a huge bank between an ICE genset and an electric motor, increasing fuel consumed per mile not reducing it.

In that scenario, solar making any significant contribution requires the owner adapting their usage pattern to the drivetrain rather than v/v.
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Old 09-12-2018, 12:47   #1461
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Re: Oceanvolt Hybrid Motor

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I'm also making the case that the losses in conversion from mechanical to electric to mechanical are offset by the ability to optimize the load on the ICE. To that end I ask: Of the last 10 engine starts and stops on your boat, what percentage of the time where you operating at the most efficient load for the engine? Honest answers appreciated, do not throw away any starts/stops for testing/maintenance/I was moving slips/babying it/etc., it all counts.
We're full time cruisers and we don't visit marinas. So generally our engines are either idling while we pull up or lower the anchor, or they're operating in a good efficiency range.

Living aboard and cruising full time, we use maybe 500 litres of fuel per year. Much of that in the dinghy, which travels some distances.

So even if a hybrid system was able to cut that in half, how long would it take to pay for itself?

Re your assertion that electric motors are better than ICEs of more than double the rated power, this hasn't proven to be the case in reality.

Torqeedo's 4 kW outboards don't match a 9.9hp. (7.4 kW)

And the recently installed OV sysyem above is showing similar performance between electric kW and diesel.
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Old 09-12-2018, 13:58   #1462
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Re: Oceanvolt Hybrid Motor

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I'm also making the case that the losses in conversion from mechanical to electric to mechanical are offset by the ability to optimize the load on the ICE. To that end I ask: Of the last 10 engine starts and stops on your boat, what percentage of the time where you operating at the most efficient load for the engine? Honest answers appreciated, do not throw away any starts/stops for testing/maintenance/I was moving slips/babying it/etc., it all counts.

I think you are too optimistic. If you can optimize the load on the ICE when attached to an alternator, you can do the same for direct coupled (gear ratio/prop size). You are also taking the heat produced by the alternator and EP motor too lightly.
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Old 09-12-2018, 23:33   #1463
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Re: Oceanvolt Hybrid Motor

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Originally Posted by 44'cruisingcat View Post

And the recently installed OV sysyem above is showing similar performance between electric kW and diesel.
So glad to hear you say that 44 Just bear in mind that the OV system is 15kW motors i.e. 21HP, and Leopard 46's would normally have 45HP diesels installed, at least. So you've agreed at last with the proposition, from the data that has been given for Kato, Jajapami and now svReality?

So that's all that has been said from the very beginning, that you can get pretty much the same cruising boatspeed from a good electric system that is nominally half the "size", kW for kW.

As the article links from bridaus discussed, there is a fundamental difference in how the power is produced and applied (torque and efficiency wise), so in fact a horsepower in a diesel engine is not equal to a "horsepower" of an electric motor. It actually makes no sense to try and compare them on that basis.

I have always said that in terms of the relative kW rating of both types of propulsion, the work done by an electric, of the SAME kW RATING is more ( by a factor of somewhere between 2 and 3) than the same kW rated marine diesel.
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Old 10-12-2018, 00:03   #1464
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Re: Oceanvolt Hybrid Motor

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Originally Posted by BigBeakie View Post

I have always said that in terms of the relative kW rating of both types of propulsion, the work done by an electric, of the SAME kW RATING is more ( by a factor of somewhere between 2 and 3) than the same kW rated marine diesel.
And I have always wondered why, if this is true, nobody uses an electric motor to power their generator.... would you need a 30 kW rated diesel to run a 10kW generator?

BTW, what I said was that from the numbers quoted, electric kWs seem to be about equal to diesel ones.

The main difference being that the electric motor was running at 100% throttle, while the diesel wasn't.
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Old 10-12-2018, 01:49   #1465
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Re: Oceanvolt Hybrid Motor

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Originally Posted by 44'cruisingcat View Post
And I have always wondered why, if this is true, nobody uses an electric motor to power their generator.... would you need a 30 kW rated diesel to run a 10kW generator?
Actually they used to do exactly that on ships to produce power at a higher frequency 400Hz, but now there is electronics which made that use case obsolete.

BTW, what I said was that from the numbers quoted, electric kWs seem to be about equal to diesel ones.
Which example are you using? Kato was compared to 75HP diesels, that's 15kW OV compared to 55kW Yanmars. Jajapami Saba 50 was 15kW OV compared to 42kW diesels and svReality is 15kW OV compared to 34kW diesels all at CRUISING boatspeed.

The main difference being that the electric motor was running at 100% throttle, while the diesel wasn't.
Did you just make that up?
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Old 10-12-2018, 08:20   #1466
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Re: Oceanvolt Hybrid Motor

What svReality reported makes sense. They get about the same STW using diesel powered electric as diesel mechanical running similar HP. But most boats have bigger diesels and can go faster because the diesels will have more HP in reserve while the EP was maxed out.

Also, they reported about 600watts produced by the regen at about 5 knots with a loss in speed of 0.5 knots. That sounds about right.

But the data doesn’t support the idea that an electric HP does more work than a diesel HP. A HP is a HP is a HP no matter how you get the energy to produce said HP.

Someone proposed that diesel engine suppliers “stretch the truth” about the HP rating of their engines. I don’t agree with that. And, of course, no EP supplier would ever do that.

Go back and reread svReality’s report. The results make sense and do not require magic EP HP to do so.
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Old 10-12-2018, 11:48   #1467
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Re: Oceanvolt Hybrid Motor

Seems the non-magic HP point is still not clear. Using svReality's situation:

ICE: The minimum rated HP I must buy is 108HP (80kW) (Rated Maximum) in order to USE 40HP (30kW) continuously at cruise. I CANNOT choose half size engines and cruise continuously at this speed because the half size engines will break down, they are not rated for continuous use, nor could they do it.

Electric: I can buy 30kW (Rated Continuous) in order to USE 30kW continuously at cruise. I don't have to buy 80kW unless I wish to cruise faster and less economically (most people are not making this choice because they do not have to, but could).

The difference is:

Electric HP/kW: I can USE the rated HP/kW I buy.

ICE HP/kW: I can only use the rated HP/kW I bought for a period of time depending on it's duty rating.

Sidenote: IC engines can be derated for continuous use, and conversely electric motors can be overdriven for periods of time. Both are limited purposefully for reliability and marketing purposes. Lookup the continuous duty rating for your engines, you might be surprised.

Alternatively stated:

We have to buy IC engines at 2 times the HP/kW of an electric motor because we need it to have enough power and be efficient for our intended USE (cruise speed, not WOT). We have to buy more rated HP than we need. Any less and it wont cruise.

We can buy an electric motor at half (or less) the HP/kW of an ICE because we do not NEED to cruise at WOT. But we have a choice, if what was most important to us was WOT speed, we can buy a bigger motor and use only the power we want. BUT we are not forced to and therefore we can size our motor at half the kW. It's not magic.


PS: I say it's stretching the truth to sell me something that I cannot use most of the time. If I bought a 1600 sq ft house, but I could only use all 1600 for 6 out of every 24 hours, 800 the rest of the time (look up light duty ratings!) Might just be me, but that's a stretch!

Linky: MARINE ENGINE DUTY RATINGS

Edit: Not even light duty, those Yanmar's are "pleasure duty" rating, from Yanmar themselves:

Quote:
Rating definition: PD

Max output less than 5% of total operation hour, continuous operation duration (full throttle) less than 30min
Standard operation; less than 90% of the maximum engine speed
Typical operation hours from 250hrs (private) to 500hrs (rental), consult Yanmar for the use of light duty commerial applications
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Old 10-12-2018, 12:25   #1468
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Re: Oceanvolt Hybrid Motor

A quick check of a Yanmar 3YM20 (15 kW rated)
manual shows:

Fuel stop power: 15.3 kW at 3600 rpm
CONTINUOUS POWER: 13.9 kW at 3489rpm.

I don't know where you learned arithmetic, but where I did, 13.9 kW is a fair bit more than half of 15 kW.

https://www.yanmarmarine.com/Product...s/3YM30AE-426/
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Old 10-12-2018, 12:36   #1469
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Re: Oceanvolt Hybrid Motor

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Originally Posted by 44'cruisingcat View Post
A quick check of a Yanmar 3YM20 (15 kW rated)
manual shows:

Fuel stop power: 15.3 kW at 3600 rpm
CONTINUOUS POWER: 13.9 kW at 3489rpm.

I don't know where you learned arithmetic, but where I did, 13.9 kW is a fair bit more than half of 15 kW.

https://www.yanmarmarine.com/Product...s/3YM30AE-426/
I'm confused by your post, I'm not sure what part of my math you are questioning.

Edits (sorry, way too many as I worked to understand you and Yanmar).

My source for pleasure duty: https://www.yanmar.com/global/suppor...epleasure.html

Maybe Yanmar rates pleasure duty differently than most? Everything is possible.

I do see the engine you reference, which lists continuous power, but they still rate it as pleasure duty, on the page I linked above with the asterisks/definitions they put at bottom. I'm not a Yanmar expert, but I have worked with duty ratings before. Pleasure duty is very light use and does not match the numbers you are showing. Their documentation is contradictory, but I can't debate their words, only they know. Duty rating is still an input no matter what single data point you find. Maybe there's some honest engine manufacturers, maybe there's some dishonest electric motor manufacturers, I wouldn't be surprised by either.
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Old 10-12-2018, 12:40   #1470
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Re: Oceanvolt Hybrid Motor

From that page you can download the engine manual, covering a range of 3 cyl engines.

The manuals show continuous power outputs much higher than 50% of rated maximum output.
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