Viability of electric only propulsion in 2018 - is there a good option after all?

[john61ct]

Originally Posted by john61ct

And for viability for EP without diesel genny, the ocean-going (even just coastal) liveaboard cruising use case **has to** go out the window.

Perhaps you thought the above meant I think liveaboard cruising requires fossil fuels.

Not at all.

But EP used for liveaboard cruising on the ocean cannot replace fossil fuels, it only increases their usage through its inefficiency in requiring hybrid in order to be practical.

[KTP]

Even if a prop was only 25% efficient vs 100% efficient sculling, this means it would only take 400 watts EP to equal a person sculling with a oar.

That is the output of two or three solar panels in full sun, or just one solar panel + a little extra battery because I bet a person could not scull for more than a couple hours a day in real world (or at least I couldn't).

If sculling works, EP with solar charging works.

[CatNewBee]

Originally Posted by KTP

Even if a prop was only 25% efficient vs 100% efficient sculling, this means it would only take 400 watts EP to equal a person sculling with a oar.

That is the output of two or three solar panels in full sun, or just one solar panel + a little extra battery because I bet a person could not scull for more than a couple hours a day in real world (or at least I couldn't).

If sculling works, EP with solar charging works.

Well, good idea, the galleeres in the roman ages used rowing slaves for propulsion. The greenees are not too far away to re-introduce those methods to reluctant modern boaters with foosile fuel preferrences...

[Peregrine1983]

Originally Posted by GrowleyMonster

I have all electric propulsion. I designed the plant, sourced the components, made it all play nicely together, and I am happy with it for my needs and will be even happier when I have my 2kw of solar canopy up and running. So I think I am qualified to pitch in here.


No, for most applications, a straight serial diesel/electric hybrid plant is NOT more efficient in the long run. As others have said, there is too many stages of energy conversion, and no conversion even remotely approaches 100% efficiency. The only thing you would gain is greater maneuverability (no minimum idle speed, instant on and reverse) and the ability to motor on battery only for short duration quiet runs. And this could better be done with a parallel hybrid setup, anyway. The only way to make a hybrid in sustained, multiday use, more apparently efficient is to get free electricity from a very large solar panel array. Forget about wind. To get a reliable 1kw in most places, you need a turbine with an approximately a 10' diameter swept area. That's just 1kw. At 48v that is just 20 amps. On a sailboat, your solar capacity is severely compromised by shading. Regen robs you of considerable speed under sail, typically a half knot, for a small amount of charge, which is insignificant, usually, at under 10kt anyway.


A motor cruiser with hybrid propulsion and plenty of solar is viable. You won't save much money over the cost of a diesel and fuel, though. You can have range, or you can have reasonable speed, or you can have a manageable battery. You can only have one, your choice. Usually we figure on going slow, having a big bank, and going far. For the size boat you are talking about, the solar needed is just mind boggling, as is the bank required. LiFeP04? Better have deep pockets. Tesla car pack, or Power Wall? I won't touch that in a boat. Nowhere to run to. TelCo cells would be my choice. And high voltage. Maybe a backup bank of NiFe Edison cells. (they last essentially forever)


Best application for electric is a pure electric setup, charging from shore power, for a day sailer or weekender. In fact, for this application, an infernal combustion engine is just plain stoopid. This is where electric drive shines, not cruising. For cruising you have to accept and allow for a lot of drawbacks versus straight diesel drive. Of course with parallel hybrid, you can simply ignore the electric drive motor anyway, and operate in straight diesel mode on a passage. The electric motor simply serves as a big alternator keeping a huge bank charged and keeping your air conditioner and electric range working. And of course maneuvering at the dock.

Nice post Growley. This is the best summation of this debate I've seen yet, and from a person with first hand electric drive experience.

[StuM]

Originally Posted by KTP

Even if a prop was only 25% efficient vs 100% efficient sculling, this means it would only take 400 watts EP to equal a person sculling with a oar.

That is the output of two or three solar panels in full sun, or just one solar panel + a little extra battery because I bet a person could not scull for more than a couple hours a day in real world (or at least I couldn't).

If sculling works, EP with solar charging works.

If you're happy to cruise at 1-2 knots in calm conditions, that's fine.

[valhalla360]

Originally Posted by KTP

Even if a prop was only 25% efficient vs 100% efficient sculling, this means it would only take 400 watts EP to equal a person sculling with a oar.

That is the output of two or three solar panels in full sun, or just one solar panel + a little extra battery because I bet a person could not scull for more than a couple hours a day in real world (or at least I couldn't).

If sculling works, EP with solar charging works.

Sculling a 35' sailboat is going to be very slow going. Yeah, if you are OK with 1kt only in calm conditions, electric is viable now.

Also, in what world do you think sculling is 100% efficent? And hours of 100w output is unrealistic...particularly if conditions are anything less than placid. If the boat is being tossed around in 6-8' waves, good luck skulling for 6-8hrs.

If you are talking about a 20-25' boat that only uses power to get on and off a mooring...I think pretty much everyone here has said electric is viable now...but that is a rare type of cruiser.

[KTP]

Originally Posted by valhalla360

Sculling a 35' sailboat is going to be very slow going. Yeah, if you are OK with 1kt only in calm conditions, electric is viable now.

Also, in what world do you think sculling is 100% efficent? And hours of 100w output is unrealistic...particularly if conditions are anything less than placid. If the boat is being tossed around in 6-8' waves, good luck skulling for 6-8hrs.

If you are talking about a 20-25' boat that only uses power to get on and off a mooring...I think pretty much everyone here has said electric is viable now...but that is a rare type of cruiser.

I was trying to counter an argument that said EP isn't viable for cruising when people are currently cruising using just an oar (well I only know about Lin and Larry so very small sample size). I was saying that the electric equivalent of sculling with an oar is a teeny 100 to 400 watts. If you were happy with the speed you obtain from sculling your sailboat, you would be happy with the speed from a 400 watt motor.

Someone with a 10kWh battery bank could more reasonably motor at 2kW and likely obtain speeds of 3 to 4 knots in calm conditions for 5 hours. Maybe even a little better than 4 knots depending on boat.

[a64pilot]

Originally Posted by KTP

I was trying to counter an argument that said EP isn't viable for cruising when people are currently cruising using just an oar (well I only know about Lin and Larry so very small sample size). I was saying that the electric equivalent of sculling with an oar is a teeny 100 to 400 watts. If you were happy with the speed you obtain from sculling your sailboat, you would be happy with the speed from a 400 watt motor.

No, they are sailing, sculling only we needed, which I’d assume if your not in a hurry and plan, is rare, cause you know that has to get old pretty quick.
An oar can just lay there or be lashed to the stanchions for a long time until it’s needed, and it will work, it doesn’t t require recharging, adding water or anything, it just works.

However what we seem to be missing here is their form of Solar propulsion is Sails, not EP.

Hoping Boat Alexander will chime in and explain why he abandoned EP and went to an oar, my assumption is that the oar works pretty well, well enough anyway, and the sails work very well.

[StuM]

Originally Posted by KTP

I was trying to counter an argument that said EP isn't viable for cruising when people are currently cruising using just an oar (well I only know about Lin and Larry so very small sample size).

Boat Alexandra here on CF is the archetypal sculling cruiser.


If you want to travel around the world like him, feel free to do so.

[valhalla360]

Originally Posted by KTP

I was trying to counter an argument that said EP isn't viable for cruising when people are currently cruising using just an oar (well I only know about Lin and Larry so very small sample size). I was saying that the electric equivalent of sculling with an oar is a teeny 100 to 400 watts. If you were happy with the speed you obtain from sculling your sailboat, you would be happy with the speed from a 400 watt motor.

Someone with a 10kWh battery bank could more reasonably motor at 2kW and likely obtain speeds of 3 to 4 knots in calm conditions for 5 hours. Maybe even a little better than 4 knots depending on boat.

Lin and Larry make fun reading but their style of cruising has almost nothing to do with a typical cruiser. (and there is discussion occasionally where they had to get tows because they couldn't safely get into some harbors).

2kw might get you 3-4kts on a very small boat but the size and feeding needs of a 10kwh battery bank on a 20' sailboat starts becoming problematic and only gets those kinds of speeds in the calm conditions.

We had a mount for our dingy motor on our 34' cat (not a particularly large cruising boat) that allowed it to run as the backup. At 5hp (a little shy of 4kw), in a couple tests we were able to get it up to just around 3kts in glass calm conditions. In anything rough, I'm not sure it would have gotten us any headway. I'll give you 10-1 a skulling oar with 100w input, wouldn't get us 1/2kt in calm conditions.

[john61ct]

Originally Posted by KTP

I was trying to counter an argument that said EP isn't viable for cruising when people are currently cruising using just an oar (well I only know about Lin and Larry so very small sample size).

As has been said many times, EP without fossil fuels is perfectly "viable" for

those willing to radically change their usual use case,

or (maybe) using a purpose designed vessel built from scratch.

But for 99.99% of those currently cruising long-term at sea, EP without fossil fuels is simply not viable.

I wish it were! But wishing doesn't make it so.

[KTP]

Well I will report real world what 2kW does for a 15,000 pound PS34 since we are moving forward with EP. Based on what I saw for diesel consumption when bringing this boat from Seattle to Blaine, WA (about 1/2 gallon per hour which I would estimate was about 6kW going to the prop from the engine based on energy content of diesel and efficiency of non turbo diesel engine).

That 6kW got us 6 to 6.6 knots in calm water.

[CatNewBee]

Originally Posted by KTP

Well I will report real world what 2kW does for a 15,000 pound PS34 since we are moving forward with EP. Based on what I saw for diesel consumption when bringing this boat from Seattle to Blaine, WA (about 1/2 gallon per hour which I would estimate was about 6kW going to the prop from the engine based on energy content of diesel and efficiency of non turbo diesel engine).

That 6kW got us 6 to 6.6 knots in calm water.

there are LiIon outboards on the market, they have a similar power, just buy and try....

[KTP]

Originally Posted by CatNewBee

there are LiIon outboards on the market, they have a similar power, just buy and try....

I have a Torqeedo 1003 which can put out around 1000 watts to the prop IIRC. We have used it on our little Montgomery M17 to push us at about 4.8 knots full throttle but it would push us at 2 knots using only 60 watts!

I will eventually put an outboard bracket on the PS34 but have not gotten around to it.

[CatNewBee]

Originally Posted by KTP

I have a Torqeedo 1003 which can put out around 1000 watts to the prop IIRC. We have used it on our little Montgomery M17 to push us at about 4.8 knots full throttle but it would push us at 2 knots using only 60 watts!

I will eventually put an outboard bracket on the PS34 but have not gotten around to it.

https://youtu.be/9qipWHayS-c

How about solar panels printed on the sails?