Is diesel-electric or all-electric the future?

[peter loveridge]

A touch of reality therapy here. My modest 30 footer has a 20kW engine. Range without auxiliary tanks is 250 nautical miles, 450 with them. Replace it with a 10kW electric motor, ( bigger than that won't fir in the space) and just under your feet in the cockpit you have 100A at 100V going through wires in a space that is always damp. Y'all like the thought of that? Now, I want to sail from my home port , Shelburne, to Halifax, 140 nm. There will be extensive periods of flat calm doing this any time during the summer, yes you can do it all under sail , and I have done so, but it takes 4 days. The 20 nm range doesn't cut it, you'll end up in the Halifax approaches with no power and no electronics, likely in thick fog. Good luck !!

[Na Mara]

Originally Posted by WhiteHill

There's a recent informative discussion on this topic, especially pertaining to electric regeneration and which includes some useful numbers, at the AAC site:

https://www.morganscloud.com/2021/03...sing-sailboat/

I mostly agree with John here. With today's tech it is entirely possible to go all electric and that this has some great advantages in terms of off grid independence, maintenance, avoidance of diesel smells, etc. Its just that doing so is:

1. Very expensive,
2. Not as green as alternatives such as, diesel electric or even just restricted usage of a standard diesel.

If you are going all electric for the advantages listed above then great, go for it! If on the other hand your primary purpose is to help solve global warming, then it seems to me you are simply spending insane money on something that is less beneficial in this regard than cheaper, and in some cases way cheaper, alternatives.

[Na Mara]

Originally Posted by peter loveridge

A touch of reality therapy here. My modest 30 footer has a 20kW engine. Range without auxiliary tanks is 250 nautical miles, 450 with them. Replace it with a 10kW electric motor, ( bigger than that won't fir in the space) and just under your feet in the cockpit you have 100A at 100V going through wires in a space that is always damp. Y'all like the thought of that? Now, I want to sail from my home port , Shelburne, to Halifax, 140 nm. There will be extensive periods of flat calm doing this any time during the summer, yes you can do it all under sail , and I have done so, but it takes 4 days. The 20 nm range doesn't cut it, you'll end up in the Halifax approaches with no power and no electronics, likely in thick fog. Good luck !!

But Peter, isn't this modern attitude to sailing exactly the problem? I must admit to suffering from it as well. We need to get back for work on Monday but holiday time is precious so we head out as far as we can and leave getting back to the last minute. Then the wind doesn't cooperate so we stick on the iron genny and trug home at best speed wishing we were actually sailing.

If we just sailed where the wind took us a bit more and planned a bit better, and left a bit more time for the homeward leg so that it doesn't matter if we bumble along at 3 kns with the asymmetric up, we would still get home in time. What would life be like then? Hell wouldn't it just be great if bosses accepted "becalmed" as a reason for not turning up to work on time. What if.... What if...

[valhalla360]

Originally Posted by Adelie

The ICW is a special case, like the canals of Europe. Extrapolating from observations there to general behavior around the world would lead to false conclusions.

If 95% of sailboats are only daysailing out of marinas then that 5-10gal/yr is a significant fraction of fuel used by all sailboats and switching to electric drive would have significant effects.

It's one of the easiest places to document the phenomenon but most places with dense cruising populations we've seen similar activity. Fact is sailboats make nice efficient slow speed motor boats and most people aren't obsessive about sailing vs motoring.

You have flawed logic on the "significance" of savings. If you are only burning 5-10gal per year, a 100% reduction is not a significant reduction in the big picture of overall fossil fuel consumption. Huge cost for little benefit.

[Hermia II]

First, I live 15 minutes from Lund and I can tell you that the Swedish environmental "research" is grossly politisized through grants paid by the government which is heavily blackmailed by its coalition partner the "Environmental Party" that represents about 3,5% of the population. Anything supporting Greta, no matter how idiotic, is granted taxpayers money.
Second, It happens to most of us that one time or another the bilge is full of salt water. In heavy weather sloshing all over the place, and that is not when you want all the systems shut down.
I will start using LiFePo4 batteries this season, they are probably fabulous, but I'm slightly concerned that they may be too fragile since the have quite some electronics built in.
If sailing along challenging coasts, with tidal streams and tight passages where you just can't go tacking, I would keep my old diesel and run it on pure diesel that would not promote any bacterial growth in the tank.

[Adelie]

Originally Posted by valhalla360

It's one of the easiest places to document the phenomenon but most places with dense cruising populations we've seen similar activity. Fact is sailboats make nice efficient slow speed motor boats and most people aren't obsessive about sailing vs motoring.



You have flawed logic on the "significance" of savings. If you are only burning 5-10gal per year, a 100% reduction is not a significant reduction in the big picture of overall fossil fuel consumption. Huge cost for little benefit.

I was addressing the world of cruising sailboats not the world as a whole. I was very specific in my second paragraph. Did you miss that or were you intentionally trying to expand the issue?

[kirklkjb]

I'd second the integrel system. It looks like a well designed and well thought out approach. It optimizes diesel engine efficiency and eliminates a generator saving weight and cost. They have a retrofit version also if that's of interest. I have no interest in this company. Just like their approach. https://integrelsolutions.com/

[Dockhead]

In my opinion, the situation with electric and hybrid propulsion of pleasure yachts with technology as of 2021 is pretty simple.

1. Pure electric propulsion is a winner for boats which are at a dock with shore power every night AND which has limited need for range (either sails most of the time or shorter trips or very light vessel or some combination). So perfect for a daysailer or picnic boat etc. or racer.

2. Hybrid propulsion for a cruising boat, whether series or parallel, is pointless. It is more expensive, heavier, AND less efficient -- worst of all possible worlds. Once you have a diesel engine on board, just connect it directly to the propeller shaft and forget about it.


3. A possible exception to the above is a catamaran where you might reduce the number of diesel engines by driving one or both props electrically.

[Dockhead]

Originally Posted by kirklkjb

I'd second the integrel system. It looks like a well designed and well thought out approach. It optimizes diesel engine efficiency and eliminates a generator saving weight and cost. They have a retrofit version also if that's of interest. I have no interest in this company. Just like their approach. https://integrelsolutions.com/

I agree that this is a very good approach -- using one diesel engine for both propulsion via direct drive of the shaft, AND generation of domestic electrical power.


The "Integral" system looks fine, but you can achieve something like this with a much simpler setup -- school bus alternator or Humvee alternator, regulated in a way that you can scale down the power in order not to overload the main engine at certain points on the prop curve. I have the cheapest and simplest school bus alternator on my main engine and get reliably 2.5kW out of it, which make the generator (a 6.5kW heavy duty Kohler) almost superfluous.

[kirklkjb]

One aspect to think about is the optimization of the diesel engine to produce both shaft and electrical power simultaneously. On a boat with a large electrical load being able to charge the LI batteries quickly and efficiently without a generator saves weight and complication. You're using the diesel engine to drive the boat which it's very good at while getting rid of a generator and enabling you to run A/C at night without the hum of a generator. Can be done using the Integrel system or similar home built version with large amperage alternators.

[Dockhead]

Originally Posted by valhalla360

It's one of the easiest places to document the phenomenon but most places with dense cruising populations we've seen similar activity. Fact is sailboats make nice efficient slow speed motor boats and most people aren't obsessive about sailing vs motoring. . .

That's a very accurate observation. I don't know anyone who motors less than 50% of the time in any cruising boat, except on long ocean passages, which make up a tiny % of total miles done in cruising boats.



Day sailer or bay boat or racing boat may be different.

[PeroniPete]

It's clear that YANMAR or someone should build a Diesel engine with an integrated electric motor/generator. How easy would that be...maybe the prop could be used to spin up the generator for regeneration. It's done all over the place with auto hybrids. I think there'd be huge demand. They're too darn slow getting started some of these big manufacturers. Or just run the main diesel for generation if need be, rather than having another great lump of a diesel gen. on board, it's just more weight and expense. Yes, you'll use a bit more fuel, but still much cheaper in the long run.

[Statistical]

Originally Posted by Na Mara

An addendum to all this about the drivetrain is of course the current fad for going all electric in boat systems. Electric water heating, space heating, cooking, bilge pumps, etc. This is supposed to make sense on the all electric boat as you have a whopping great big battery bank anyway to power the drives for a reasonable range, so why not go all in. I suppose this is all fine if you are not using diesel to generate electricity for any of this but if you are then surely this too is nuts. As stated previously, turning diesel into electricity you loose about 70% of the energy stored in the diesel. Now you use that to heat your water for a cup of coffee on your induction stove, which is about 90% efficient. So, allowing for inefficiencies in a diesel stove, about 60% of the energy in the diesel has been lost in this process relative to just heating the water directly. That is nuts. The same goes for water and space heating also. So again one wonders whether the supposed benefit of being able to go all electric for ship systems really holds water. Perhaps if you truly have a totally electric boat with no diesel generator that relies solely on renewable generation and shore power, but that doesn't seem realistic given the energy requirements just for heating and cooking never mind all the other systems and motivation.

Again are we, for the sake of some purist fantasy of the all electric boat, actually pursuing an ideal that is in fact more harmful to the environment than an alternative that still involves diesel? Again its an honest question as I too am attracted to the clean simplicity of the all electric sailboat. Its just the article has got me thinking that maybe I'm being sold on something that doesn't pass muster once you really start to think about it.

I think a lot would come down to what percentage of your total energy consumption comes from the diesel. If it is 100% then yeah that makes no sense. If it is 70% it probably also doesn't make sense but what if combined with a large solar arch, wind, and regen it is only 30%. Yes the diesel -> electric would be lower efficiency but it would only be part of the system input.

Is that enough to matter? Not sure but I think the less you could use the diesel the more it "could" make sense.

[Corvidae]

I run electrics on my sailboat now. It works out well. The electrics will get us out to sea easily enough, and we have a large enough generator/chargers to run at 4.5 knots continuously. When we're sitting around, the large bank with a big inverter lets us use big 110v appliances, or 240 if I had any. How long we can sit on the hook without charging really depends on what we cook more than anything. It does take a few hours of generator if we let them discharge fully. We'll have to see how it plays out once we put up our 1kw of solar.

Overall it's a very versatile setup, that's more dependable and repairable, than the diesels we removed. Cost wise we're slightly below the price of replacing our diesel motors which had to be done anyway. Which is mainly the case because I did it DIY. The complete systems would have cost about 1.5x as much or more. Which is more than worth it for what you get, but way too much to spend if you have a dependable diesel. Maybe if you sell an existing diesel it might be more cost effective, but would still leave you with a less powerful engine. That calculus might be shifting though. We didn't really save much by going electric so far, but the price of the motors I bought has dropped, the price of diesel replacements has not. The cost of batteries, solar panels and inverters is all falling, and the selection is expanding.

Right now, electric drives are worthwhile in some cases. There's a lot of considerations, some of them are nothing to do with propulsion. My entire galley runs at 110v with no propane or other fuels. Which cuts down the cost of having to get 12v or propane appliances. But that also depends on weather, or not, you already have working appliances when you're doing a refit, and where that might leave you with repairs down the road.

There's no 'this is the best setup' answer for any boat. Every boat is a list of compromises, no matter what propulsion system you're using. The real question is if it works for what you want to do, or what a bunch of people want to do. Electrics do work the best for the way a lot of people use their boats. Definitely not everyone though.

[Statistical]

Originally Posted by Corvidae

I run electrics on my sailboat now. It works out well. The electrics will get us out to sea easily enough, and we have a large enough generator/chargers to run at 4.5 knots continuously. When we're sitting around, the large bank with a big inverter lets us use big 110v appliances, or 240 if I had any. How long we can sit on the hook without charging really depends on what we cook more than anything. It does take a few hours of generator if we let them discharge fully. We'll have to see how it plays out once we put up our 1kw of solar.

Overall it's a very versatile setup, that's more dependable and repairable, than the diesels we removed. Cost wise we're slightly below the price of replacing our diesel motors which had to be done anyway. Which is mainly the case because I did it DIY. The complete systems would have cost about 1.5x as much or more. Which is more than worth it for what you get, but way too much to spend if you have a dependable diesel. Maybe if you sell an existing diesel it might be more cost effective, but would still leave you with a less powerful engine. That calculus might be shifting though. We didn't really save much by going electric so far, but the price of the motors I bought has dropped, the price of diesel replacements has not. The cost of batteries, solar panels and inverters is all falling, and the selection is expanding.

Right now, electric drives are worthwhile in some cases. There's a lot of considerations, some of them are nothing to do with propulsion. My entire galley runs at 110v with no propane or other fuels. Which cuts down the cost of having to get 12v or propane appliances. But that also depends on weather, or not, you already have working appliances when you're doing a refit, and where that might leave you with repairs down the road.

There's no 'this is the best setup' answer for any boat. Every boat is a list of compromises, no matter what propulsion system you're using. The real question is if it works for what you want to do, or what a bunch of people want to do. Electrics do work the best for the way a lot of people use their boats. Definitely not everyone though.

Thanks for the real world example. Just curious what is the size of your battery bank and how large is your generator?