Is diesel-electric or all-electric the future?

[peter loveridge]

In reply to Adelie, the range on my Toyota Tundra truck, which is not overly fuel efficient, is 900Km on a full tank. This is about 600 miles

[Simon.Sails]

Originally Posted by Na Mara

1. 43ft monohull
2. 14 ton with full tanks and stores
3. 90hp
4. 6 kn on average under sail, 6.5kn on engine
5. 0.7l per nm so 4.5l an hour.

Just had a crazy thought.

What about installing two indepedent 6kW oceanvolt saildrives sharing one of their 7.6kW batteries. That should give me 10nm of electric motoring, and sufficient power for all but the windiest of days for close quarters stuff (on those days I have the big one in reserve) for the cost of about 25000 euros fitted and vat paid.
(...)

Or am I missing something?

At 6kW is it worth getting expensive inboard electric engines? Why not just get twin electric outboards with regen like the Navy 6.0 for 1kw max regen and some marina motoring? Would cost a fraction of that price as well.

[valhalla360]

Originally Posted by Na Mara

Yes and no. If you are just going for the say 3 or 4 weeks of cruising a year then probably yes it s drop in the bucket. You might do 300nm in those three weeks on average and lets say you are the typical ICW cruiser who sails only half the time. Then on my boat you are only producing about 250 kg of CO2 anyway which is about what you would emit on one shortfall flight. If you are sailing instead of going abroad you have already done the environment a favour.

However if you are living aboard and doing that whole 50/50 thing then assuming 300nm a month (ignoring ocean crossings which are always under sail), then you are pumping out maybe 300kg a month including propane and sundries. That's over 3.5 tons a CO2 a year on my boat. That's just slightly less that what the average Swede emits in a year in total. You are probably still doing the world a favour living aboard and not taking lots of flights, not heating a big house, and doing lots of car miles, but it still an unsustainable amount of emissions.

Full time liveaboards make up a tiny percentage of new boat buyers, so not really relevant when considering the larger market. Even when we were full time on the Great Loop, we were burning a fraction of what we did when we had a house and commuted to work. It was still a drop in the bucket. And again, if it's really that critical to your personal sense of morality, sail more of the time and you can achieve the same thing without the expense complication and risk of a marginal propulsion system.

PS: I would suggest using a more realistic country. Sweden along with Norway enjoy a huge percentage of hydro power (which according to some is also evil). It's an artificially low value in most parts of the world.

Where I see electric as having a way in with boats is on the house load side. With a large battery bank, you can eliminate or reduce generator use on the much more common days when you aren't on the move.

[MikeHoncho]

Originally Posted by Statistical

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

And what is the life expectancy of them?

[valhalla360]

Originally Posted by Simon.Sails

Interestingly in Germany and Switzerland the opposite has been found to be the case; most hybrid cars were bought by companies for tax purposes (green vehicle tax exemption etc.), but used for long distance drives almost daily. With that usage hybrid cars were actually the least environmentally friendly of all cars. That's because the ee was only used for the first 20km or so, after that a slightly more inefficient petrol engine was used.

But yes, in the cited study with the usage pattern of the average urban commuter hybrid make a lot of sense. In a way a fully electric boat with a small backup gas generator approximates that solution the closest.

This is why the govt shouldn't be manipulating the market. Companies buying cars to drive long distances would select the move efficient option...except for the fact the govt distorted the pricing.

It's not a problem of the technology but the govt rules.

[valhalla360]

Originally Posted by Simon.Sails

At 6kW is it worth getting expensive inboard electric engines? Why not just get twin electric outboards with regen like the Navy 6.0 for 1kw max regen and some marina motoring? Would cost a fraction of that price as well.

Hydro regen is a bit of a red herring when discussing the larger market.
- On long ocean crossings, you are sailing anyway and a basic solar setup can handle most house loads. In light to moderate wind, you lose more generating than you would gain using the power generated for propulsion. If it's windy and can generate, you don't need it to maintain good speed.
- Day sailing, you can always plug into shore power or if on a mooring, there is typically several days for the solar to top up between weekend trips.
- Coastal cruising, there just isn't a lot of time under sail in conditions suitable for generation.

It still comes back around to how to generate the significant power needed in a reasonable time frame and carry it around on the boat. The electric motors are not the issue.

You can extend range with electric by slowing down...but then a fair comparison would be to downsize the diesel and slow down with that, not as is commonly done of comparing a full power diesel running at 80% of hull speed to an under powered electric running at 40% of hull speed.

[moseriw]

Simon.Sails It can not be what has to be.

[Na Mara]

Originally Posted by Simon.Sails

At 6kW is it worth getting expensive inboard electric engines? Why not just get twin electric outboards with regen like the Navy 6.0 for 1kw max regen and some marina motoring? Would cost a fraction of that price as well.

That right there is fricking genius!!!!

Seriously.

I can absolutely see exactly how I could do that as well. A neighbour in my marina has exactly the same make of boat as mine and he has a WattSea mounted on his boarding platform on one side. I would just do exactly like him but would instead have the Navy 6.0 on both sides. I could put power tilts on them and even have some way of coupling and decoupling them from the helm. With those and my bow thruster I could really make my boat dance in the marina. When in harbour or in really light winds I can lift them. When powered up I lower them for the recharge. If really crappy weather is coming I just take them off and stow them below. Hell I could even loan one for the dinghy when needed. No holes in the bottom of my boat and its cheap in comparison with alternatives.

You wouldn't want to rely on them in any kind of sloppy seas or for serious distances but then that is not the point.

TOTAL FRICKING GENIUS!!!

I am going to look very seriously into this!!

P.s. Even just as an alternative to an aft thruster this is a seriously cool idea. My wife will love it.

[Adelie]

Originally Posted by Na Mara

I'm sorry but I don't agree with this assessment. The full electric sailboat with regen using hydro generation and solar is absolutely possible today and more efficient in use than the alternatives. My back of an envelope calculation earlier showed this. With 20kW of engines and an induction stove you would need on average to generate maybe 30kWh a week. Hydro generation will get you 5-10 of those, so you need enough solar to supply 20-25kWh a week. Make it 21kWh to make the math easy, then you need enough solar to generate 3kWh a day. In the Caribbean average daily insolation is 5kWh/m^2. The efficiency of todays solar panels in charging batteries is about 20%, so you will need about 3m^2 of panels. That is easily doable on a catamaran and not impossible on a monohull.

The fossil free cruising sailboat is possible with today's tech and in use it will be massively greener than the fossil fuelled alternative. Its just that the embodied emissions of such a boat and its enormous initial cost (and how that money could accomplish way more carbon abatement elsewhere) entail that while it is possible it is not advisable if your goal is saving the planet.

The full electric displacement motorboat is a totally different kettle of fish. Let's imagine a 45ft cat with very skinny easily driven hulls powered by two 10kw motors. You will want that boat to be able to motor continuously 24/7 and to be able to do that even in inclement weather when full power is needed. Here we can ignore ships systems as the drives totally dominate the calculation. 2x10x24 is as near as makes no difference 500kWh a day including drive inefficiencies. Even with the multilayered solar panels of the future (45% efficient) capable of netting you on average 2kWh/m2 a day you are going to need 250m2 of panels. At most the footprint of a 45ft cat is 14x8=112m2. Basically you would need twice that real estate to have a hope of making this work, but then you would have greater windage and more mass and so you would need bigger drives and thus would need even bigger panel area. It just does not work. The full electric long-range motor cruiser is just not possible with today's tech or even with tech available in the near future, period. Also for reasons outlined earlier series hybrids aren't clever either (max75% efficiency of straight diesel).

Basically, until we have commercially available hydrogen and a means of storing onboard at really high pressures SAFELY (at least 10000psi, see footnote) then the motor cruiser is stuck with diesel. .....

Current technology allows for a 40’ motor cat that can motor indefinitely at 4kt in calm winds.

You want to do ocean passages it won’t work.

If you want to do the ICW and into the Caribbean, sure. You just have to use a bit more discretion waiting for weather windows.

https://www.azura-marine.com/aquanima-40

[Dirk01]

Originally Posted by CarlF

I'd go even farther. I don't believe that diesel electric makes sense in most cruising applications where there is a single genset.

Unlike a car, a marine diesel can be run 90%+ of the time at exactly its most efficient rpm and there is essentially no energy loss in a modern marine transmission. The power all goes to the spinning shaft.

In a diesel electric the genset is a diesel engine using the same amount of fuel per Kw as the propulsion engine - but then they mess it all up with huge energy losses by converting the diesel rotational energy to electricity with an alternator, then maybe convert the electricity through a charger to battery chemistry through voltage-loss causing wires, and then converting it all back again through a controller and wires to rotational energy in an electric motor to turn the shaft. I believe you lose well over 20% of the energy doing all this compared to a diesel engine directly coupled to a shaft through a transmission to the same shaft.

Large diesel electric ships (or trains) have multiple generators and run just the the number needed for the situation. This obviously saves fuel.

And you don't see diesel electric trucks because there is only one engine. Even hybrid cars are not like diesel electric. The gasoline engine directly drives the wheels through a clutch with little energy loss. The electric motor can also drive the wheels from battery power providing two power sources to the wheels.

It's simply Newtonian physics.

Sorry, but you are wrong. A modern genny run with there optimum rpm (best efficiency) depending on load. That saves a lot of diesel per produced kW.
A diesel-propulsion system runs at the rpm given by the speed you'd like to have. And that will nearly never with and at 90% load, where the best efficiency point is. Only at or nearby this point you're better than an diesel-electric system!
You're comparing oranges and apples!
(And that has nothing to do with Newton - is pure power chain math.)

Cheers
Dirk

[moseriw]

Thought this is a cruisers forum though I expected partipiciants with boats > 30 ft. but it looks like a sailing in my swiming pool forum

[moseriw]

E propulsion is such a good idea. You use 100% 300% comes from solar and at minimum 150 % from recuperation.

Shhhhh, time to wake up.

Same with the climate preservers. It can not be what one do not want to be.
Pure fiction of supervised thinkers.

[Adelie]

Huh??

[Simon.Sails]

Originally Posted by Na Mara

That right there is fricking genius!!!!

Seriously.

I can absolutely see exactly how I could do that as well. A neighbour in my marina has exactly the same make of boat as mine and he has a WattSea mounted on his boarding platform on one side. I would just do exactly like him but would instead have the Navy 6.0 on both sides. I could put power tilts on them and even have some way of coupling and decoupling them from the helm. With those and my bow thruster I could really make my boat dance in the marina. When in harbour or in really light winds I can lift them. When powered up I lower them for the recharge. If really crappy weather is coming I just take them off and stow them below. Hell I could even loan one for the dinghy when needed. No holes in the bottom of my boat and its cheap in comparison with alternatives.

You wouldn't want to rely on them in any kind of sloppy seas or for serious distances but then that is not the point.

TOTAL FRICKING GENIUS!!!

I am going to look very seriously into this!!

P.s. Even just as an alternative to an aft thruster this is a seriously cool idea. My wife will love it.

Very cool, that's exactly what I had in mind!
I've been contact with them already regarding a single Navy 6.0 on a trimaran. According to their rep the hydro regen only works with their own branded 48v batteries, but a) they're quite reasonably priced and b) it's no problem at all coupling it or using it as a house bank.

At decent speeds the regen of twin outboards should be amazing. And for marina manoevers they should also work great.

Keep us posted about that idea, it could be a really great concept for a lot of boats!

[moseriw]

And yes I know someone who goes electric with a 36 feeter.
He sails right to the entrance of the marina and the rushes in with 6 knots for 10 minutes to proof himself how good his motor is.

Without wind and 8 miles to go he reduces speed to 2 knots after calculating if he will make it or not.

I hope he never ever needs a powerful engine beeing adrift.