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Old 30-06-2020, 17:33   #211
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Re: Replace Diesel with electric engine

Yes, different personal values result in different choices. I am reminded of the Pardeys, who inspired many would-be cruisers but were themselves marching to the beat of a different drummer from more than 99% of cruisers. They had small vessels without any non-wind propulsion systems. They used wind, sweeps, and the occasional tow, and seemingly were happy with that choice. I think it is safe to say that the great majority of cruisers would not be happy with that approach - all that matters is that they were satisfied. The problem I have with these discussions is that they can mislead noobs into thinking these approaches (e.g. no engine or electric motor) are more mainstream and more functional than they really are, or are equivalent to the more common approaches. They work for some people but not the great majority. Choosing to take a different path is fine, as long as it is an informed choice.

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Old 30-06-2020, 17:38   #212
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Re: Replace Diesel with electric engine

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Originally Posted by valhalla360 View Post
Sort of...the multiplier assumes the full days output. You won't get 4 hours where it's pumping out a steady 2.4kw. You might get an hour or two at the peak output but then lower output for the shoulder hours and very little in morning and late afternoon, so total output results in about 4hr at the rated output.

A large battery bank with a few days hanging out at anchor to charge up could mitigate to a degree.

For the Panama Canal, it's a little over 50 miles but call it 60 miles as they aren't going to let you tie up at the locks and you may have to motor in circles staging to get in.

At 5kt, that's looking like 12hr. So if you can generate enough solar to provide 2hr over the course of the day, you need battery sufficient for the remaining 10hr. Assuming 5kw output to maintain 5kt and you maintain a 20% margin in case something goes wrong, you need about 60kwh of battery (yes, I'm mixing miles and nautical miles but close enough for estimation).

Of course, if you hit a strong headwind crossing the lake, that all goes out the window and you will run out of power. To fill 60kwh with the solar will take 6 days...they aren't going to be happy about you sitting half way thru for 6 days waiting to get charged up.

No way 5kW will get that 53 footer anywhere near 5kts IMO. My little 33' Greenline Hybrid cruiser w/ a 32.5 LWL and 7.7kn hull speed will make little more than 5kts at full 150A draw in flat water with its 48V 7kW motor and 12kWh lithium pack.

My guess is at least 15kW needed for the big guy to maintain 5kts in flat conditions. It weighs in at least 3X my 6 tons w/ half tankage, has a hull speed only 1kt faster, and an enormous WSA, not to mention the huge windage in her ketch rig.
The main advantage of the hybrid to me is it's full-time 120V through a Victron 48V/5kW Quattro inverter/charger, and 500W solar array, needing no diesel charging for at least 3 days on the hook - longest so far. All appliances are 120V, inc. a 5'x2'x2' freezer/fridge. The motor becomes a 5kW gen. when running with the 165HP diesel at over 2000 RPM.
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Old 30-06-2020, 18:45   #213
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Re: Replace Diesel with electric engine

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And if the generator is large enough to power the motor continuously (and with a sufficiently large enough tankage) then what has been accomplished by all of the extra cost and complexity? Just hook the diesel genset engine to the prop shaft and get rid of the rest...
See and that is where you go wrong. With the diesel engine, it is selected to move the boat at hull speed. But the generator only needs to be able to power the electric motor for cruise speed and that is an enormous difference. The electric option can still go at hull speed, using the generator plus batteries.

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Shortly after my last Atlantic crossing I talked to 2 other boats that had crossed with electric drives: neither would buy electric again. One of them was a big cat with a huge solar array who had discovered that it wasn't even keeping up with their freezers' needs. The other was a small boat and his small array didn't make much of a dent on requirements - the genset ran whenever he moved the boat.
So there are idiots. That’s all this says, irrelevant to the discussion. Big cats with huge solar arrays and electric drive generate 10kWh or more per day, which is enough to power the Walmart frozen section
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Old 30-06-2020, 19:00   #214
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Re: Replace Diesel with electric engine

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For a motorboat sure you need a fixed install diesel genset that can power the electric motor up to cruise speed besides a decent battery bank. I would have that for a sailboat as well.
Or about 4-5kW of solar plus battery bank plus 5kW alternators on the diesels acting as parallel hybrids . 5 knots pretty easily, 5.5 possible, 6kn don't ask . Oh, and a nice powercat to put them on... unfortunately that doesn't match the OP wanting to replace their diesel rather than augment it.

For a sailer (yep), Uma is just one example of going electric only. Add in a temporary genset and you'll probably be ok-ish. It really doesn't take too much kW for a long-ish hull to get to 4kn. 5kn is doable. More than that though is exponentially tougher! The difference (in theory) between 5 and 5.2 and 5.5 knots is a lot of kW... Uma's most recent has some stats when they replaced their OV15 leg.

Agree entirely with the values point. But it wouldn't surprise me that long before 50 years, you'll not be allowed in some marinas, rivers and ports without being fossil fuel emission-free. Just look at the major cities going that way for cars. It's coming for boats (see Amsterdam as a start).

There are many people out there making really interesting changes - they're not necessarily blaring it out in the PNW, or Caribbean, or Spain or ... If you're stuck 200nm from your backyard and haven't travelled or read you may not know too much about the rest of the world (let's not go to the videos of people who can't answer simple geography questions - there are some everywhere): there are many forums apart from this one for electrification of boats, from narrow boats to large passenger ferries.
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Old 30-06-2020, 19:35   #215
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Re: Replace Diesel with electric engine

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Originally Posted by PineyWoodsPete View Post
No way 5kW will get that 53 footer anywhere near 5kts IMO. My little 33' Greenline Hybrid cruiser w/ a 32.5 LWL and 7.7kn hull speed will make little more than 5kts at full 150A draw in flat water with its 48V 7kW motor and 12kWh lithium pack.

My guess is at least 15kW needed for the big guy to maintain 5kts in flat conditions. It weighs in at least 3X my 6 tons w/ half tankage, has a hull speed only 1kt faster, and an enormous WSA, not to mention the huge windage in her ketch rig.
The main advantage of the hybrid to me is it's full-time 120V through a Victron 48V/5kW Quattro inverter/charger, and 500W solar array, needing no diesel charging for at least 3 days on the hook - longest so far. All appliances are 120V, inc. a 5'x2'x2' freezer/fridge. The motor becomes a 5kW gen. when running with the 165HP diesel at over 2000 RPM.

The Maramu has a much longer waterline than the Greenline and as a sailboat a shape more optimised for low drag, so it will use significantly less energy per ton to maintain a given speed.

Let's use data from another sailboat to make an estimate.

I used Uma data as a baseline: they use 4.2kW electric to go 5kt. Psychosnail calcs that they would need 8.1kW ICE to go 5.0kt. So about 1.93 times what was measured for electric propulsion.
I used a LWL of 29.2', and a displacement of 15,000lb.

Assuming 41.2' LWL and 40,000lb displacement for the SuperMaramu
Psychosnail calcs 15.9kW ICE to make 5kt.
Using the same ratio as Uma, the Maramu would need 8.2kW. Let's be conservative and say 9.0kW even.

The OP is intending to install a 48kW-hr bank. At 9.0kW usage that would be enough for 5h20m at 5.0kt, that's about 26nm. That's a bit more than half way thru the canal which is 44nm lock to lock. Half way is 22nm which would take 4.4hr using 39.6kW-hr, leaving a bit more than 8kW-hr in reserve.

If there was a 2.2kW Honda putting out 2.0kW then 30.8kW-hr would be used from the batteries to get that far. It would then take about 15hr to fully recharge.

Yes there is distance from anchorage to locks at each end. But the several hours waiting for and sitting in the locks also provides time for the generator to top the batteries back up.

Note none of this involves any solar or wind power. That would just improve the reserve power situation.
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Old 30-06-2020, 22:39   #216
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Re: Replace Diesel with electric engine

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It's a function of the values of the cruiser. You don't value the quieter running, the lack of fuel and lubricant smell nor the freedom from fossil fuels so you aren't willing to make the compromises needed to accept electric drive. That's fine.

Other people's values are different from yours so some are happy to accept those compromises.
Plus you don't value 500W (or more) of regen power at your disposal on passage if doing 6knts or something like that.

As well as a big LFP battery bank at anchor, which, if coupled to a big solar array, allows you to go through cloudy days without ever starting the generator.
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Old 30-06-2020, 23:31   #217
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Re: Replace Diesel with electric engine

Hmm.. how comes that an 60 KW engine output is equalized to an 16 KW motor?
this implies an efficiency factor of 3,75

Yes engines efficiencies are rated as 40% BUT it is already calculated by the engineers and when they say 60 KW output it is 60 KW output.

So....
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Old 01-07-2020, 00:52   #218
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Re: Replace Diesel with electric engine

The diesel-hp vs electric-kw difference has been done to death and nothing will change by bringing it up again here...

A summary for those who don't know: there is a claim that an X hp of diesel propulsion is equivalent to a Y kW of electric propulsion. For some people, if X is not the same as Y then physics is no longer and perpetual motion rules and the world order falls. Even this "sensible" discussion (and I use that term advisedly) is marred by the claim that the installation of an X hp diesel in the boat (as against hp-to-get-to-a-speed) is needed versus a much smaller Y kW electric installation, often to "get out of danger".
Typically we may read that someone replaces something like a 50hp diesel with a 10kW electric (which really should read: a diesel capable of 50hp and an electric capable of 10kW).
Usually torque is mentioned, lightning and thunder occurs and nothing is gained in the conversation - those in one camp won't convince those in the other.

For me, even my simple reading finds a lot of people who reports results of using a hybrid or electric motor and that they substantiate the difference in diesel hp propulsion and electric kW propulsion - X does not equal Y where the speed that is wanted overlaps (ie. I wouldn't suggest using electric to go 20knots for a relatively normal boat).
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Old 01-07-2020, 04:00   #219
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Re: Replace Diesel with electric engine

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Originally Posted by mcarthur View Post
The diesel-hp vs electric-kw difference has been done to death and nothing will change by bringing it up again here...

A summary for those who don't know: there is a claim that an X hp of diesel propulsion is equivalent to a Y kW of electric propulsion. For some people, if X is not the same as Y then physics is no longer and perpetual motion rules and the world order falls. Even this "sensible" discussion (and I use that term advisedly) is marred by the claim that the installation of an X hp diesel in the boat (as against hp-to-get-to-a-speed) is needed versus a much smaller Y kW electric installation, often to "get out of danger".
Typically we may read that someone replaces something like a 50hp diesel with a 10kW electric (which really should read: a diesel capable of 50hp and an electric capable of 10kW).
Usually torque is mentioned, lightning and thunder occurs and nothing is gained in the conversation - those in one camp won't convince those in the other.

For me, even my simple reading finds a lot of people who reports results of using a hybrid or electric motor and that they substantiate the difference in diesel hp propulsion and electric kW propulsion - X does not equal Y where the speed that is wanted overlaps (ie. I wouldn't suggest using electric to go 20knots for a relatively normal boat).
Basically I agree with you, however I didn't understand the last paragraph at all.

Torque is clearly better with electric especially at low rpm, but indeed it does not matter at constant boat speed/constant power, and of course has no influence on autonomy.
Typically :

Taken from :
https://www.voiles-aventures.com/new...ie-les-moteurs

Regarding the diesel vs electric hp, let's not forget that 1 kW = 1.34 hp in terms of physical units, but you mentionned something else in the last paragraph right ?
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Old 01-07-2020, 04:11   #220
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Re: Replace Diesel with electric engine

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Originally Posted by PineyWoodsPete View Post
No way 5kW will get that 53 footer anywhere near 5kts IMO. My little 33' Greenline Hybrid cruiser w/ a 32.5 LWL and 7.7kn hull speed will make little more than 5kts at full 150A draw in flat water with its 48V 7kW motor and 12kWh lithium pack.

My guess is at least 15kW needed for the big guy to maintain 5kts in flat conditions. It weighs in at least 3X my 6 tons w/ half tankage, has a hull speed only 1kt faster, and an enormous WSA, not to mention the huge windage in her ketch rig.
The main advantage of the hybrid to me is it's full-time 120V through a Victron 48V/5kW Quattro inverter/charger, and 500W solar array, needing no diesel charging for at least 3 days on the hook - longest so far. All appliances are 120V, inc. a 5'x2'x2' freezer/fridge. The motor becomes a 5kW gen. when running with the 165HP diesel at over 2000 RPM.
I was just demonstrating the math and I was not assume a 50some foot boat.
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Old 01-07-2020, 04:18   #221
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Re: Replace Diesel with electric engine

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Originally Posted by mcarthur View Post
The diesel-hp vs electric-kw difference has been done to death and nothing will change by bringing it up again here...

A summary for those who don't know: there is a claim that an X hp of diesel propulsion is equivalent to a Y kW of electric propulsion. For some people, if X is not the same as Y then physics is no longer and perpetual motion rules and the world order falls. Even this "sensible" discussion (and I use that term advisedly) is marred by the claim that the installation of an X hp diesel in the boat (as against hp-to-get-to-a-speed) is needed versus a much smaller Y kW electric installation, often to "get out of danger".
Typically we may read that someone replaces something like a 50hp diesel with a 10kW electric (which really should read: a diesel capable of 50hp and an electric capable of 10kW).
Usually torque is mentioned, lightning and thunder occurs and nothing is gained in the conversation - those in one camp won't convince those in the other.

For me, even my simple reading finds a lot of people who reports results of using a hybrid or electric motor and that they substantiate the difference in diesel hp propulsion and electric kW propulsion - X does not equal Y where the speed that is wanted overlaps (ie. I wouldn't suggest using electric to go 20knots for a relatively normal boat).
The problem with your last paragraph is it hasn't been substantiated in reports. What typically happens is they change the rules for the electric drive:
- They presume, you don't want to do hull speed.
- They presume, flat water with no wind.
- They talk about thrust.

Now if you want to accept a dramatic reduction in performance, you should rip out the 50kw diesel and put in a 10kw diesel for comparison to a 10kw electric motor.

Where electric motors will outperform is acceleration but that's not a big deal for most displacement cruising boats.
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Old 01-07-2020, 08:20   #222
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Re: Replace Diesel with electric engine

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Originally Posted by s/v Jedi View Post
yes something like the Panama canal means you probably need a genset because you’re not allowed to sail... but you could even rent one for a couple of days if you need more capacity than you have.
Hmm, unlike mooring lines and fenders, I doubt you'll be able to rent a portable generator in Colon that you could return in Panama City. It would be nice if you could!
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Old 01-07-2020, 08:48   #223
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Re: Replace Diesel with electric engine


Taken from :
https://www.voiles-aventures.com/new...ie-les-moteurs


Note : This Graph is from a Porsche study comparing diesel of around 55 hp, to electric motors.

And it clearly shows that indeed, at the typical rpm where the diesel are used on boats, around 2000 rpm, the equivalent(in terms of max power) electric motor delivers more power.
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Old 01-07-2020, 09:50   #224
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Re: Replace Diesel with electric engine

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Originally Posted by valhalla360 View Post
The problem with your last paragraph is it hasn't been substantiated in reports. What typically happens is they change the rules for the electric drive:
- They presume, you don't want to do hull speed.
- They presume, flat water with no wind.
- They talk about thrust.

Now if you want to accept a dramatic reduction in performance, you should rip out the 50kw diesel and put in a 10kw diesel for comparison to a 10kw electric motor.

Where electric motors will outperform is acceleration but that's not a big deal for most displacement cruising boats.
Storage of energy is the flip side of propulsion is Electric Vs Diesel energy storage. My storage of 500 Lt of diesel equates to round 5,000Kwh of energy which equates to about 170 hours at cruising speed of 7-8 kn
Does someone want to do a broad calculation how much battery, how much solar panels and how many days of sunshine to push an equivalent battery powered boat at an equivalent speed for equivalent hours?
On a boat there is no alternative to fossil fuel grunt.
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Old 01-07-2020, 10:03   #225
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Re: Replace Diesel with electric engine

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Originally Posted by yvest View Post

Taken from :
https://www.voiles-aventures.com/new...ie-les-moteurs


Note : This Graph is from a Porsche study comparing diesel of around 55 hp, to electric motors.

And it clearly shows that indeed, at the typical rpm where the diesel are used on boats, around 2000 rpm, the equivalent(in terms of max power) electric motor delivers more power.
So it supports the fact that indeed, when replacing a diesel by an electric motor, the rated electric motor power should be less than the diesel one.
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