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

[Jon Hacking]

Originally Posted by a64pilot

Very, very few people tow generators. I’ve never met anyone that does...

Well, you've met one now, if only online. We see them now & then, but you & I are probably as far apart as it's possible to be on this earth, so very different cruising grounds. An old prop off a 6hp outboard will do wonders at 5 knots (towed backwards). Boats don't use brakes the way EVs do, but you can still generate a lot of power for only a tiny loss of speed.

[a64pilot]

Pretty sure Jim made one as well from an old tape drive I think.
However my point is that if they worked all that well, you would see them a lot, they are not any more complex and likely less so than a wind generator for instance.
Doubt you have to worry about overspeed is what I’m saying.
How much power do you get on a good day? How much does it slow you assuming your not at a wind speed where your at hull speed anyway?
There was one I think that could function as both a wind and a towed hydro generator, tow it until you get where your going, then anchor and put it on the pole as a wind generator.
Seemed to be a good idea to me.

[john61ct]

Originally Posted by john61ct

But asking the vehicle to collect its own power via wind, hydro and/or solar, is a non-starter, full stop.

Originally Posted by Jon Hacking

Excuse me?!? One of the big advantages of electric propulsion is that it can recharge the batteries while sailing (assuming your batteries have the capacity to get you to where the wind is blowing). Lots of boats pay good money for towing generators. The biggest problem with electric propulsion is range, as the energy density of batteries is still much lower than diesel.

No, as I said, on-boat hydro, just like wind and solar, doesn't capture enough energy for propulsion.

No matter how much storage capacity you may have.

Except for new purpose-built designs costing millions, and very unusual usage patterns.

And electric propulsion only consumes energy, never charges anything.

[StuM]

Cue BB in 3,2,1...

[Jim Cate]

Originally Posted by Jon Hacking

Well, you've met one now, if only online. We see them now & then, but you & I are probably as far apart as it's possible to be on this earth, so very different cruising grounds. An old prop off a 6hp outboard will do wonders at 5 knots (towed backwards). Boats don't use brakes the way EVs do, but you can still generate a lot of power for only a tiny loss of speed.

Originally Posted by a64pilot

Pretty sure Jim made one as well from an old tape drive I think.
However my point is that if they worked all that well, you would see them a lot, they are not any more complex and likely less so than a wind generator for instance.
Doubt you have to worry about overspeed is what I’m saying.
How much power do you get on a good day? How much does it slow you assuming your not at a wind speed where your at hull speed anyway?
There was one I think that could function as both a wind and a towed hydro generator, tow it until you get where your going, then anchor and put it on the pole as a wind generator.
Seemed to be a good idea to me.

Yep, 64, I did do that, and it was quite successful. That boat did a lot of miles at around 6 knots, and at that speed my homebrew towing gen put out around 10 amps. At 7 knots it was substantially higher, but it would jump out of the water frequently and tie the towing rope in knots, rendering it useless. None the less, it supplied all our domestic power needs. Quite useful, but clearly not capable of recharging a depleted propulsion bank.

It was hard to accurately determine how much it slowed us down. My estimate was between 1/2 and 1 knot, depending on speed and conditions.This was long before good solar systems arrived on scene, and was a good cruising device for its time. Honestly, I'd like to have one now, 'cause my solar panels don't work well in winter or at night, and I hate running the engine to charge batteries.

It seems obvious to me that to extract enough power to service propulsion banks, one would slow all but extremely powerful yachts so much as to be unacceptable. May work for Kato, but likely not for lesser cruising boats... the numbers just are not there. I do believe that the RTW solo racers use a hydro generator to supply much of their electrical needs (mostly autopilots) but again, these are very powerful boats, capable of >15 knots much of the time... a regime where there is more energy to be harvested than in our slower vessels.

Jim

[a64pilot]

Guys remember the be nice rule please

[Jim Cate]

Originally Posted by a64pilot

Guys remember the be nice rule please

Is that directed at me, 64? Or just the vagaries of timing...

Jim

[john61ct]

Originally Posted by Jim Cate

to extract enough power to service propulsion banks, one would slow all but extremely powerful yachts so much as to be unacceptable. May work for Kato, but likely not for lesser cruising boats... the numbers just are not there. I do believe that the RTW solo racers use a hydro generator to supply much of their electrical needs (mostly autopilots) but again, these are very powerful boats, capable of >15 knots much of the time... a regime where there is more energy to be harvested than in our slower vessels.

But the bigger the boat the more propulsion power needed.

If only for occasional short docking, maybe.

But **safety** dictates plenty of power for unanticipated situations, strong tides, wind pushing you onto a reef etc

suddenly running out of juice after 30min in an emergency just doesn't wash with me.

And if you have a diesel for hybrid / backup anyway, it's just so much more efficient to power the prop directly.

And **so much** cheaper!

An electric houseboat puttering around a calm lake, sure.

Cruising at sea, just can't see it except as a rich man's Science Project or for PR status value.

[daletournier]

Currently Lifepo batteries are the most advanced for our purposes or at least the most practical if not considering lead. What batteries are on the horizon, that are as safe or safer and offer greater performance?

Anyone know what's coming?

[a64pilot]

Originally Posted by Jim Cate

Is that directed at me, 64? Or just the vagaries of timing...



Jim

No, I deleted a post that was over the line.

[darylat8750]

Interesting that towed hydro generator worked for Jim. Back in the '70s I read a bit about how that should be one of the arrows in the cruisers quiver. And wind generation still has it propionates. But with the improvement in solar and batteries many who don't sail high latitudes would rather avoid wind and water generators and get by nicely with solar at anchor.

[a64pilot]

I think the difference is Solar is much better now and a fraction of the cost it used to be, where kinetic generators are about where they have always been cost and efficiency wise.
I think it’s primarily cost. I know when I was looking to set up my boat only a few years ago I looked at wind vs Solar and a little at towed, and it boiled down to for the same money I could get a Whole lot more out of Solar, but I cobbed up my own mounts from scrap aluminum extrusion and bought excess house panels for .50c a watt too. So I have 1000 W of Solar for about $1,000, which is awful cheap by comparison to wind or a towed generator.

[Augi]

Excuse me if this has been covered here or on another thread but tell me what I am missing?

Why is a hybrid parallel diesel / electric not viable?

For example take a 50'-60' cruising mono hull that has a direct drive diesel(not sail drive). Put an electric motor / generator between the diesel and the prop on the drive shaft.

Load up on batteries lithium or other type of batteries if you are concerned lithium will catch fire.

Of course do everything else that makes sense, using solar, wind generator, and hydro generator.

With a hybrid parallel diesel / electric won't you have the best of both worlds? You have your same diesel engine, and batteries. Then you get your 20 NM miles or whatever it is using electric propulsion only. When the diesel is running and providing the propulsion it can use the electric motor / generator installed in parallel on the same direct drive shaft to re-charge the batteries or just use an alternator per the typical set up. Then every however long it takes to recharge your batteries, you have 20 NM or whatever on electric propulsion only available.

So unless I am missing something the only difference between the hybrid described above and diesel only solution is the extra money for electric motor / generator that will be installed on the direct drive shaft that the diesel is connected to + the cost of gearing / transmission / control system etc to go back and forth between electric propulsion and diesel propulsion.

The extra investment for the electric motor probably does not make economic sense but it is partially offset by using less diesel, and less wear on your diesel engine. Plus you get the advantages of electric some of the time: instant higher torque / better maneuverability / quiet, no fumes.

A negative is you would have another set of equipment to take care of by adding the electric motor, etc.

If you have good luck and have wind you would never have to use the diesel engine because the 20 NM or whatever it is you would have on electric propulsion is almost always enough to get in and out for most.

The only complication I can think of ( I am not an engineer), is the different power and torque curves of diesel versus electric and therefore the prop optimal for diesel is not automatically optimal for electric. To solve that you need either some kind of gearing or a prop that can be adjusted.

I don't think very many people are using the above solution. A good many large, production, cruising yachts offer direct drive. So why is the above not being done? Is it just the extra expense is not worth it for the 20NM miles or whatever you get on each charge to have electric propulsion? Or is there some technical reason plus you only get 20NM or whatever per charge on electric propulsion?

[john61ct]

Yes entirely do-able, but

noobs come into this topic with greenie dreams of environmental purity, no gains in that direction, in fact lower efficiency per gallon of diesel consumed.

And lots of extra resources consumed in producing the new capital equipment.

Violates KISS, complexity is less reliable, especially cruising in less developed locations.

Finally, comes down to, what is the upside? Why do it at all?

[Augi]

Originally Posted by Augi

Excuse me if this has been covered here or on another thread but tell me what I am missing?

Why is a hybrid parallel diesel / electric not viable?

For example take a 50'-60' cruising mono hull that has a direct drive diesel(not sail drive). Put an electric motor / generator between the diesel and the prop on the drive shaft.

Load up on batteries lithium or other type of batteries if you are concerned lithium will catch fire.

Of course do everything else that makes sense, using solar, wind generator, and hydro generator.

With a hybrid parallel diesel / electric won't you have the best of both worlds? You have your same diesel engine, and batteries. Then you get your 20 NM miles or whatever it is using electric propulsion only. When the diesel is running and providing the propulsion it can use the electric motor / generator installed in parallel on the same direct drive shaft to re-charge the batteries or just use an alternator per the typical set up. Then every however long it takes to recharge your batteries, you have 20 NM or whatever on electric propulsion only available.

So unless I am missing something the only difference between the hybrid described above and diesel only solution is the extra money for electric motor / generator that will be installed on the direct drive shaft that the diesel is connected to + the cost of gearing / transmission / control system etc to go back and forth between electric propulsion and diesel propulsion.

The extra investment for the electric motor probably does not make economic sense but it is partially offset by using less diesel, and less wear on your diesel engine. Plus you get the advantages of electric some of the time: instant higher torque / better maneuverability / quiet, no fumes.

A negative is you would have another set of equipment to take care of by adding the electric motor, etc.

If you have good luck and have wind you would never have to use the diesel engine because the 20 NM or whatever it is you would have on electric propulsion is almost always enough to get in and out for most.

The only complication I can think of ( I am not an engineer), is the different power and torque curves of diesel versus electric and therefore the prop optimal for diesel is not automatically optimal for electric. To solve that you need either some kind of gearing or a prop that can be adjusted.

I don't think very many people are using the above solution. A good many large, production, cruising yachts offer direct drive. So why is the above not being done? Is it just the extra expense is not worth it for the 20NM miles or whatever you get on each charge to have electric propulsion? Or is there some technical reason plus you only get 20NM or whatever per charge on electric propulsion?

For example I saw on the Hanse website they offer a parallel hybrid solution similar as described above. I was curious so I asked a USA dealer for Hanse. They said yes it is on the website but no they have not sold a boat equipped with a parallel hybrid set up. I guess no one wants to be the guinea pig for minimal range on electric propulsion plus it costs more.