Will electric outboards start replacing diesel inboards?

[DeValency]

Originally Posted by newhaul

for sailboats its all about energy storage . A lot more energy in 80 pounds of diesel than 80 pounds of batteries.
It also is extremely inefficient to use diesel to make electricity to run an electric motor to move a vessel verses using that diesel motor to drive the vessel directly.
The reason for using hybrids systems on ferries and the like is purely a matter of response times. Whereas the efficiency is not paramount.

I have to disagree, not only being a sailor for 50 years but also an EE for 35....

1. The efficiency of electric engine is almost 80% and it is getting better faster then ever on efficiency, size and weight.
2. Higher efficiency means less heat - e.g, less cooling - one of the major issues we deal with for our diesels.
3. The same electric motor output for marine propulsion, weight is about 30% of the equivalent diesel...
4. When speaking about the energy bank, I didn’t mean the present D8 type... new batteries are way smaller and lighter - yet also way too expensive but costs drops sharply there.
5. You cannot generate diesel by sun and wind, electric potential is generated by these for 100 years now and the technology make it better and better.
6. For the time being, we’ll still need diesel gensets - I have a 7.5KW already anyway, but will be happy to remove my fantastic 75HP Yanmar (that I really love!) or better, get the next boat in a few years with a bad engine or no engine, so can install the electric then...

In other words - the revolution here is much feasible and closer than we think.

[newhaul]

Originally Posted by DeValency

I have to disagree, not only being a sailor for 50 years but also an EE for 35....

1. The efficiency of electric engine is almost 80% and it is getting better faster then ever on efficiency, size and weight.
2. Higher efficiency means less heat - e.g, less cooling - one of the major issues we deal with for our diesels.
3. The same electric motor output for marine propulsion, weight is about 30% of the equivalent diesel...
4. When speaking about the energy bank, I didn’t mean the present D8 type... new batteries are way smaller and lighter - yet also way too expensive but costs drops sharply there.
5. You cannot generate diesel by sun and wind, electric potential is generated by these for 100 years now and the technology make it better and better.
6. For the time being, we’ll still need diesel gensets - I have a 7.5KW already anyway, but will be happy to remove my fantastic 75HP Yanmar (that I really love!) or better, get the next boat in a few years with a bad engine or no engine, so can install the electric then...

In other words - the revolution here is much feasible and closer than we think.

I agree with the efficiency of the engines but the battery tech is nowhere near to competing with the energy density of diesel. I do solar installs and Lfp conversions. Electric propulsion is fine for occasional use but for long term constant use at speed there is no comparison to ice be it diesel or gasoline. Also at the cost of a new electric motor I can fully rebuild my md2b several times. How much battery do you think it would take to move my 4.5 ton sailboat at hull speed for the same 40 continuous hours that my 20 gallons of diesel/ bio diesel. You couldn't fit it on my boat.

[DeValency]

Originally Posted by newhaul

I agree with the efficiency of the engines but the battery tech is nowhere near to competing with the energy density of diesel. I do solar installs and Lfp conversions. Electric propulsion is fine for occasional use but for long term constant use at speed there is no comparison to ice be it diesel or gasoline. Also at the cost of a new electric motor I can fully rebuild my md2b several times. How much battery do you think it would take to move my 4.5 ton sailboat at hull speed for the same 40 continuous hours that my 20 gallons of diesel/ bio diesel. You couldn't fit it on my boat.

In your case you are right of course.
But again: I’m speaking of 5-7 years from now on the new batteries.
And - a diesel genset is still going to stay for the next years. And a good one can provide enough charge to drive an electric propulsion for 40 hours - it is mostly a matter of the diesel tank that should be smaller than the one you would need for a driving diesel.

[newhaul]

Originally Posted by DeValency

In your case you are right of course.
But again: I’m speaking of 5-7 years from now on the new batteries.
And - a diesel genset is still going to stay for the next years. And a good one can provide enough charge to drive an electric propulsion for 40 hours - it is mostly a matter of the diesel tank that should be smaller than the one you would need for a driving diesel.

I myself don't have an installed genset and my main is just 18 HP
But using a genset to make electricity to run an electric motor is much less efficient than using the same engine for direct propulsion
Laws of thermodynamics and all.

[myocean]

Originally Posted by LuvSun

Haha that takes the cake. Would love to know how long that big boy takes to recharge.

The power is transferred to the ship with 10 kV and 10 MW. (...) On board the ship the power from the 10 kV is transformed down to 800 V, and is rectified to direct current (DC) before it is charged to the batteries.
see Water-Cooled Batteries Ensure Fast Charging of Electric Ferries Across Øresund - PBES

[Simi 60]

How much to get one in my 65 tonne vessel and will I still get 3500nm range?

[bluenomads]

Originally Posted by newhaul

I myself don't have an installed genset and my main is just 18 HP
But using a genset to make electricity to run an electric motor is much less efficient than using the same engine for direct propulsion
Laws of thermodynamics and all.

Nope. Factually wrong UNLESS you're talking of something like a workboat/tug that runs at a high (efficient) RPM for the majority of the time. For cruisers, you're entirely wrong.

It's easy to test - turn on your diesel and leave it in neutral. Are you burning fuel? yes. How much? X gph. Now put it in gear at the lowest you can still run. Are you burning fuel? yes. How much? X+a bit more Y gph. A diesel in direct propulsion needs power just to idle doing nothing. Upto it's maximum power, lessening to zero as you reach max, some of the fuel is just to keep that diesel going and not to provide power at the shaft.

Now turn on a DC genset directly connected to an electric motor in neutral. Is it burning fuel? Yes. How much? I'm told by the DC guys that it's a lot less than X because there's no load and it's a DC gen. Now put it in gear at lowest setting. You're burning fuel in the genset BUT as a DC genset you're running at an efficient conversion factor. For an AC genset (and personally I'd do it for DC as well unless lightning had fried my battery bank), put a battery bank between the genset and the electric motor and then the efficiency really starts to show.

[myocean]

Originally Posted by Jim Cate

do they actually exist and run as described?

Don't want to belive?
Here an interesting video, showing even the charging robot
https://youtu.be/dgg_pohK-q8

[sailorchic34]

Originally Posted by bluenomads

Now turn on a DC genset directly connected to an electric motor in neutral. Is it burning fuel? Yes. How much? I'm told by the DC guys that it's a lot less than X because there's no load and it's a DC gen. Now put it in gear at lowest setting. You're burning fuel in the genset BUT as a DC genset you're running at an efficient conversion factor..

Oh dear...

As the kind EE in a post above indicated a electric motor can be up to 80 percent efficient. Most are 75 ish percent eff or less, but I digress. At lower electric motor speeds efficiency drops as well, down to as low as 50 percent ish.

So a 60 percent eff. diesel engine will be more efficient then a diesel electric system that has a 60 percent eff. diesel, running a 80 percent motor. That gives you at best 48 percent system efficiency. That drops even more as the electric motor reduces RPM.

That does not even address the 3-5 percent drop in a dc speed control or VSD.


What the electric motor gives is higher starting torque, which is a really handy thing with a diesel electric locomotive. Less so with a diesel electric boat as the prop will just cavitate.

In ships it allows electric pods to be powered via diesel/electric. which allows larger vessels to dock (many cruise ships do this) by rotating the pods at various angles (360 degrees). That is handy and offers a lower overall installed cost.

For small yachts <100 feet, there is not currently a benefit going diesel electric. Well not much of one.

Though one can recapture regenerative power when sailing. That is pretty cool. Of course lithium tends to react a tad with water vapor so a non sealed LIpo cell could get exciting.

Everything is a trade off.

[valhalla360]

Originally Posted by Herb Shallcross

We have had, at several times in the past, and currently do "have" flying cars. Generally the compromises involved build out into a combination of a mediocre to poor car and a mediocre to poor airplane.

We have had small scale test models but never a readily available mass production model.

But you prove my point...with electric boats, you can have poor range, poor speed or excessive cost and complication.

[valhalla360]

Originally Posted by myocean

When talking about massive - have a look here. FULLY BATTERY DRIVEN, FULLY ELECTRIC
https://new.abb.com/marine/references/hh-ferries

And look at it's use pattern. It's much more akin to a sailboat that only uses the motor to get in and out of harbor...or in the ferries case, a short run before plugging in to recharge before the next run.

[valhalla360]

Originally Posted by AKA-None

any rate back to auxiliary electric powered sailing. At some point battery charge density will improve. Just imagine what some in 1950 would say if you tried to describe a t-105 battery which isn’t even the most power dense battery available.

While the average individual might not have been familiar, deep cycle lead-acid batteries were around in 1950.

Likewise, electric motors with similar efficiency and durability were around in the 1950's.

Lots of vaporware articles out there but really not a lot of significant new technology.

They've improved the costs of lithium batteries and solar panels (both in commercial production for a few decades now) but the easy cost savings due to economy of scale have been had. In fact, with limited supplies of lithium, we may see them increase in cost if there are any market disruptions in the mining countries...which is a real possibility.

[valhalla360]

Originally Posted by Simi 60

How much to get one in my 65 tonne vessel and will I still get 3500nm range?

At what speed?

EV proponents tend to gloss over this critical design criteria.

If you are willing to plod along at 2-3kts, it's literally 100 times easier than if you want a more typical cruising speed of 7-12kts (rough estimate given the size of your boat).

[DeValency]

Originally Posted by newhaul

I myself don't have an installed genset and my main is just 18 HP
But using a genset to make electricity to run an electric motor is much less efficient than using the same engine for direct propulsion
Laws of thermodynamics and all.

Will try not turning it into a two people discussion but stay on the general concept. Hybrid may not work for every boat/sailor/sailing plans etc.
But!
* For an electric propulsion to replace a 18HP diesel you need a relatively small electric motor considering the 2x++ efficiency, no gear etc!

* In your case, hybrid propulsion kits are already feaseaable and there is a great Youtube showing a couple doing just that when they got stuck with a dead diesel en rout from Canada. I’m not proposing anyone throwing a good diesel just in order to hybrid.

* And a 3KW genset is more than enough for almost any boat for charging and occasionally inverting for systems running on AC (not if you want to run 3 ACs, washer, dryer etc. all at the same time... )

[valhalla360]

Originally Posted by DeValency

* For an electric propulsion to replace a 18HP diesel you need a relatively small electric motor considering the 2x++ efficiency, no gear etc!

The myth of magic electric HP.

For the same performance, you need the same HP at the prop.

You might gain a few percentage points omitting the transmission. If you want to claim you could use a 15hp electric because you can omit the transmission and run at a higher percentage of rated HP, I'll buy that but you aren't going to replace an 18hp diesel motor with a 9hp (or less as you imply) electric and get the same performance.