Feasibility of Diesel-Electric propulsion for large planning hull vessels?

[fallguy]

I'm liking my Prius Prime and think it could translate into boat. Its an extra 300lbs of battery in a small car with 1.8L lawnmower engine with 98hp, plus big generator/motor so maybe total 400lbs extra. I guess it could make a boat plane but not with too much extra weight.

The concept falls apart in boats, I'm afraid.

Well, maybe a boat that uses electric if on foils?

The issue for 'planing' boats is they require a minimum power to stay afloat. The hybrid car can run in a sort of glide mode boats only get under certain scenarios. Boats don't have low friction wheels.

But I like the mention of it because it is sort of inspirational. Like, what is the equal of a Prius in a boat? Probably not really a boat.

 

[DogCavalry]

Yes, a hundred pounds of batteries equals a gallon of gas.

 

[rxcomposite]

We did build patrol planing crafts with Volvo high speed marine diesel. You just have to choose the service rating of the engine. Pleasure or intermittent use have short TBO and lightweight while continous duty ratings for commercial use weighs about a ton. Refer to engine selection manual. Some engine manufacturers have up to 6 categories.

Of course, converting DE to electric has been done before as they have used high speed turbine engine geared down to power generators, then electric motors. It was for big marine vessels.

Refer to Jane's book for vessels that have been built using this system.

 

[Squidly-Diddly]

The concept falls apart in boats, I'm afraid.

Well, maybe a boat that uses electric if on foils?

The issue for 'planing' boats is they require a minimum power to stay afloat. The hybrid car can run in a sort of glide mode boats only get under certain scenarios. Boats don't have low friction wheels.

But I like the mention of it because it is sort of inspirational. Like, what is the equal of a Prius in a boat? Probably not really a boat.

I'm mostly thinking the Prime concept would be nifty as a boat even more than as a car because there are lots of situations where running at low power or having extended hotel power would matter more on a boat than a car. If a Prime transplant power unit could sustain planing when boat loaded I think it would be perfect, since system is designed to get max mpg from ICE operation but still has battery boost which might get tapped to get up on plane. Whole system is well integrated and goes from ICE to EV to combo to ICE + batt charge and you don't need to pay any attention unless you want to play with pure EV vs charging battery. Will cruise at up to 86mph and/or "burn rubber" on EV before engine starts if desired.

The Glide Mode and energy recovery is cool and fun to play with and watch if going down long hill but don't think it would matter on a boat (unless on LONG fast downwind sailing leg). Main feature for boat use is you've got always ready instant Full Power (fully computer controlled and aftermarket hack-able) without need to think about any ICE considerations.

I was seeing "not repairable" but lightly re-ended Primes going for under $4K with less than 20K miles. Rear hatch is carbon fiber and its all space frame unibody so once it gets into that can never be "like new" specs. Main battery goes for $1000 on Ebay.Salvage Toyota Prius Primes For Sale https://erepairables.com/salvage-cars-auction/toyota/prius+prime
Could a Prime engine be made boat legal and what would that take besides maybe custom exhaust manifold? AFAIK at least the alternator and starter is all integrated deep inside and not blowing sparks.

 

[fallguy]

Yes, a hundred pounds of batteries equals a gallon of gas.

Does hydrogen have an equivalent?

 

[rangebowdrie]

Of course, converting DE to electric has been done before as they have used high speed turbine engine geared down to power generators, then electric motors. It was for big marine vessels.

Yeah, back in the 1930s the US built a class of battleships that used steam turbines to run generators.
The electric propulsion motors could turn the props directly without needing reduction gears.
In those days large reduction gears that could absorb the power requirements were very expensive and in short supply.
Turbo-electric drive has been used in all sorts of large civilian ships also, but now diesel has supplanted steam.
The biggest usage of diesel-electric propulsion today seems to be cruise ships and some types of tug/tow boats, none of which operate at high speeds, but can use the advantageous of infinitely variable thrust for maneuvering.

 

[Squidly-Diddly]

Does hydrogen have an equivalent?

2022 Toyota Mirai Specs & Options https://www.toyota.com/mirai/features/mpg_other_price/3002/3003
They don't make it easy to get basic facts, of course. IIRC they only lease the cars and you can only refuel at certain Toyota dealers in big cities. My question is does that get done at VIP speed or is it 6+ hours like my oil changes.

 

[Ad Hoc]

Does hydrogen have an equivalent?

Yup... check it out here:

 

[fallguy]

Yup... check it out here:
View attachment 179995

I am surprised it is so poor...sort of

The steps to process hydrogen are much easier.

Somehow, I always expected hydrogen to be nearly as good as gasoline. Surprised it is only 25% in a compressed liquid form.

I guess for now, water is still safe.

thanks...I learned something

 

[Rumars]

The short overview about diesel-electric and alternative energy propulsion:

1. Series propulsion: the total weight of the two electric motors, controller and battery (optional) is greater then that of a mechanical gearbox. The total efficiency tank to prop is also lower. Classic marine uses are submarines, tugs, cruiseships, military.
2. Parallel propulsion: more weight since it adds motor, controller and batteries to a normal mechanical gearbox. Used by some new sailboats. More prevalent in the military as turbine-diesel parallel.
3. Trough the water parallel propulsion: like 2, only with two completely independent propshafts. Seldom used.
4. Series-parallel propulsion: engine power is partially converted to electricity and added back to the shaft. To my knowledge not used in marine settings.
5. Trough the water series-parallel propulsion: used extensively in marine service for thrusters.

Alternative "green" energy:
1. Batteries: most efficient option (generation to propshaft), does not profit from the economy of scale effect. Limited to small/medium applications depending on infrastructure.
2. Hydrogen: next step down the efficiency scale, highly dependent on infrastructure. Rapid refueling but difficult on board storage. Profits from economy of scale but mobile large scale remains difficult.
3. Ammonia: another step down, good emission values, suitable for large scale.
4. Methanol: yet another step down, simpler tech then ammonia.
5. Synthetic gasoline/diesel: worst efficiency, simple tech.

Some comments on the anterior posts:
The Toyota Prius (and others) hybrid system is of the series-parallel type and performs the function of a CVT. Boats don't need CVT's so this particular system offers no advantages.

The Toyota Mirai exemplifies the problems with hydrogen. The full tank weighs 90kg (only 5kg are hydrogen), and is good for ~500km. The tank to wheel efficiency is up to 65% (it's a fuel cell vehicle) the total system weight is higher then the equivalent diesel, and volume is also higher.

 

[DogCavalry]

One of the biggest problems with hydrogen is that it can't be stored for long. It literally soaks into and through every material there is. Coupled with the 6.4% energy density you get a massive fuel tank that leaks steadily. Not very appealing to me.

 

[Ad Hoc]

...the total weight of the two electric motors, controller and battery (optional) is greater then that of a mechanical gearbox. ...

In the DE drive vessels we have done, this is circa 3 times the weight.