Tug of War - Electric vs Diesel

[Scout 30]

Originally Posted by a64pilot

I believe I can get by easily with a 3.5 KW generator, but if I were to use it for propulsion, I'd need a much bigger generator. I would think I would want to size a generator so that it's output alone would push me to say 75% of hull speed, so I'm agreeing that electric propulsion would I believe make sense in the design or build stage. But, I think to make it work, you need to keep it simple, I wouldn't even want regen, believing that I would use it very little as I wouldn't want to give up boat speed for it.

Somebody like Hunter or another larger manufacturer will eventually adapt a simple electric drive meant for the day sailor who is tied up to shore power every night or nearly so, it will happen. I'm surprised it hasn't already.
But you have to realize Joe Citizen is completely ignorant of Solar power, vast majority of the public thought the solar panel on a Prius sun roof would run the Air Conditioner when all it can do is power a puny fan to help exhaust some hot air, they have no idea just how much electricity is required to move something or heat water etc.

I think that if you use a generator to create a hybrid system you would not need a generator large enough to run the motor by itself. It would only have to supplement the battery power to increase your range and/or speed. 7 hours without the generator is already a pretty long time to motor nonstop so you wouldn't need much power to increase that. Solar, on the other hand, is pretty much pointless for this type of system.

[Scout 30]

One of the biggest benefits of electric propulsion for me is the lack of noise. It just makes the whole experience more pleasant.

[goat]

Originally Posted by valhalla360

Sounds great in theory but run the calculations to maintain even a modest 4kts for a typical modern cruising boat and you will see that the claims to be able to refill your batteries on the go isn't going to work.

Quite correct, and as I said, I'm sticking with diesel. However, becalmed, without fuel, 2000 miles from land, which will fill up faster; your fuel tank or your battery bank? As far as I can tell that's the only advantage to electric power until battery and/or solar charging technology catches up. Oh, and the noise...

goat

[skipmac]

Originally Posted by K_V_B

You have to of course make a correct comparison.

The ELCO price is for motor+controller. I wouldn't be surprised if the controller by itself costs several times the motor. The same for the Prius motor: I don't know what it would cost to replace the motor + the brains of a prius, but it will be a lot more than just the motor.

Agree you must compare the package but the Elco website, at least the several pages I looked, was completely silent on the issue of controller and whether or not that was part of a package deal. I tried to select a price that only mentioned the motor but just couldn't tell what was included or not.

Yes, the controller I think is not cheap. I'm trying to recall what the price for the controller was compared to the motor on some other systems I researched in the past. Without going back and looking it all up again I think it was a fairly small percentage of the motor cost, maybe in the range of 20-30%. Of course in the case of the Prius the brains are very complex and includes many functions that would never be needed on a boat.

I have researched other systems in the past that gave a clear breakdown of costs for motor, controller, mounts, etc. and the cost for the motors was still very, very high as in $4-5000 for a 10-12 KW (roughly 15 HP).

[skipmac]

Originally Posted by Scout 30

I think that if you use a generator to create a hybrid system you would not need a generator large enough to run the motor by itself. It would only have to supplement the battery power to increase your range and/or speed. 7 hours without the generator is already a pretty long time to motor nonstop so you wouldn't need much power to increase that. Solar, on the other hand, is pretty much pointless for this type of system.

This brings up a couple of issues with electric vs diesel.

One, from all my research you need less HP (or KW) for an electric motor to get the same performance you would from a larger diesel. Several factors I think relate to this. The electric doesn't have the parasitic loads you get from any ICE like pumps, alternators, transmission and other friction sources. Also you can usually mount an electric motor more advantageously so you get the prop more parallel to the boat so it will be more efficient. Then there's the issue of full torque coming at starting rpm with electric which is important in maneuvering in tight spaces or in emergencies.

Second how much HP do you really use cruising? Motoring in a calm or less than max hull speed you're using much less HP that needed in a tight turn in a marina or punching into a head sea and wind. This would impact the size of the generator needed to power the motor directly for longer range that achievable under battery. How much smaller? Maybe half the max power you would need for the occasional situations. So a 25 KW motor might only need a 12.5 KW generator to power the motor for long range cruising. But that's still a lot of generator.

[Terra Nova]

Originally Posted by skipmac

...So a 25 KW motor might only need a 12.5 KW generator to power the motor for long range cruising. But that's still a lot of generator.

Approximately equal to a common sailboat auxiliary diesel engine. But larger.

Rating electric power range based on 60% of hull speed is just fooling oneself.

[Scout 30]

Originally Posted by skipmac

Agree you must compare the package but the Elco website, at least the several pages I looked, was completely silent on the issue of controller and whether or not that was part of a package deal. I tried to select a price that only mentioned the motor but just couldn't tell what was included or not.

Yes, the controller I think is not cheap. I'm trying to recall what the price for the controller was compared to the motor on some other systems I researched in the past. Without going back and looking it all up again I think it was a fairly small percentage of the motor cost, maybe in the range of 20-30%. Of course in the case of the Prius the brains are very complex and includes many functions that would never be needed on a boat.

I have researched other systems in the past that gave a clear breakdown of costs for motor, controller, mounts, etc. and the cost for the motors was still very, very high as in $4-5000 for a 10-12 KW (roughly 15 HP).

The Elco packages are "Plug n Play" meaning everything you need is included except batteries & a charger although you can get both of those from them also. It does not appear that they will sell just the motor. They are certainly not cheap but it is a complete system & appears to be very high quality.

Elco EP Motor Benefits

[a64pilot]

Originally Posted by Terra Nova

Approximately equal to a common sailboat auxiliary diesel engine. But larger.

Rating electric power range based on 60% of hull speed is just fooling oneself.

I too think you would need a gen of approximately the same size as a normal engine, but I think rating a generator to give you say 60% to 75% hull speed is OK, as that is sustained, 100% hull speed would be available for several hours on battery bank and generator, then just like the WWII subs, your spending all long time recharging.
But I'd want a generator that by itself would drive the boat at a comfortable speed, seems I've often been offered the opportunity to sit becalmed in sweltering heat for days, or crank the Diesel and go on, guess what I do

It would be nice though to have a monster battery bank and the ability to motor for a short while silently, or to motor sail silently and I think that may be the niche of an electric drive, doesn't take much thrust at all to go from 3 kts to 6 kts+, my boat 1,000 RPM with an Autoprop does it, so maybe just a few hundred watts per hour and you could motor sail all day long without taking too much power?

[Terra Nova]

Originally Posted by a64pilot

...It would be nice though to have a monster battery bank...

Until replacement time comes around.

[Cap Erict3]

A genset is required for reliable continuous electric propulsion. There are many vessels that have utilized EP for decades.

Take subs for example.

http://www.fleetsubmarine.com/propulsion.html



I sleep better on the hook

[a64pilot]

Originally Posted by Terra Nova

Until replacement time comes around.

It just might be possible that these new batteries may last as long as an average Diesel engine? I have no idea really, but often the original purchaser of a boat doesn't care if things last much past 5 yrs or so, as they will have another new boat by that time.
I agree, the simplest, least inexpensive, and probably most efficient and durable way to drive a boat is directly from the Diesel engine, but pure electric would have some advantages for a lot of people I think.

[a64pilot]

I can imagine very similar arguments about automatic transmissions in automobiles back in the 40's, yet look at how many manuals are built now.

[charliehows]

okayyyy...let me get this right; in order to get the same or somewhat less utility as my existing 35 year old diesel, I would replace the diesel engine with a similiar sized or preferably larger diesel generator and add an electric engine as the drive source, complete with all its highly complicated and questionably reliable control systems? At what point does an electric drive system become a diesel drive system?
Sorry guys, i'm only here to enjoy the comedy value.

[Cap Erict3]

Originally Posted by charliehows

okayyyy...let me get this right; in order to get the same or somewhat less utility as my existing 35 year old diesel, I would replace the diesel engine with a similiar sized or preferably larger diesel generator and add an electric engine as the drive source, complete with all its highly complicated and questionably reliable control systems? At what point does an electric drive system become a diesel drive system?
Sorry guys, i'm only here to enjoy the comedy value.

All true.

While it is always possible a true innovator may come along someday, what is offered now just adds to the complexity and cost while lessening the reliability.


Waiting on parts for the 4-154

[StuM]

Originally Posted by a64pilot

doesn't take much thrust at all to go from 3 kts to 6 kts+, my boat 1,000 RPM with an Autoprop does it, so maybe just a few hundred watts per hour and you could motor sail all day long without taking too much power?

???????

Care to explain what you really mean by that?