Hybrid Engine Systems and Sustainability

This "which is best" argument is pointless unless you specify the operating point and type of use the system will have.

If you want best efficiency, in terms of converting potential energy in fuel into propulsive energy at the propeller, then it's a no-brainer, mechanical drive from the engine to the prop wins hands down.

If you need flexibility in layout, such that the engine can be positioned pretty much anywhere in the boat, then hybrid electric drive or hydraulic drive wins.

If you have a boat/ship that has a high domestic electrical power load, so needs big generators anyway, and you want thruster-type manoeuvrability, then hybrid electric drive wins.

As with all things, there are big trade-offs here. Both hydraulic drive and hybrid electric drive will waste more power than direct mechanical drive, so the boat/ship specific fuel consumption will suffer and it will cost more to operate. This is the price you pay for some of the advantages, like being able to place the main engines where you like and having better manoeuvrability (assuming something like the steerable pod Azipod system). The higher fuel cost may be offset by the need for fewer (or no) tugs when berthing, for example, or the better manoeuvrability may give the boat/ship access to restricted waters, or able to perform tasks that might otherwise be difficult, if not impossible, for direct mechanical drive. There may be a saving in generation capacity and engine room space by having big gensets running domestic power and propulsive power.

There's a whole host of boat/ship specific variables here that will determine the best choice, based on whole life cost versus performance (where whole life cost is purchase cost plus through life operating and maintenance cost).

 

I agree completely.
For my OWN application, advantages are:
2 boats, at times configured as a catamaran, each has a diesel.
Either diesel, as a genset, can provide power to both electric driven props.
Primarily use, it's a marina boat rather than a cruiser. There is ample opportunity to charge the battery banks from shore power.
The electric props supposedly (mfgrs claim)also serve as current powered generators to charge batteries.
A wind generator, solar panels, and/or tegs, also provide some battery charging.
I really only need the diesel gensets for emergency power/charging.
If I needed to buy the diesels, I wouldn't.
Since I already have the diesels, de-coupling them from the shafts, and coupling them to a motor that generates electricity, or functions as a motor to drive the prop, seems reasonable.
My boats are ALREADY hybrid, before installing/converting anything to electric drive.
All auxiliary powered sailboats are hybrids. Sail and engine, two separate power sources.

 

And OTHER aplications.
Low speed maneuvering auxiliary power for a sailboat.
The ability to run multiple electric propellers from a single diesel genset.
The ability to operate off batteries, for short periods of time.
The ability to use electricity from OTHER sources than the diesel gen.

As to science project? Why NOT use our boats to experiment with alternative power?
Maybe somebody will stumble on a break thru technology, that benefits us all!
Don't expect it will be me, but, if lots of folks are trying, odds are better, someone will be successful. :idea:

 

You mean like while driving, or while anchored, and the passing current spins them?

 

As to what can you do with high torque and low rpm?

You can turn a VERY large prop!

Here are two vessels I sailed on in 1970 and 1972. I was not a licensed officer, but an AB then. (able bodied seaman)
The Sylvania was 1000hp, coal fired, and made 10 knots, turning a 20 ft plus propeller at 80 rpms and less.

The Raymond H Reiss was originally a steamer of 2000 hp, but repowered with a 3 story tall diesel of 4300 hp, and made 10 knots as steam or motor.

Steam engines can produce static torque, as can electric motors. (hint, hint)

http://boatnerd.com/pictures/historic/perspectives/Sylvania/default.htm

http://www.boatnerd.com/pictures/historic/perspectives/RaymondHReiss/default.htm

 

But again, you can power exactly the same very large prop with a diesel and an appropriate reduction gear. And you can do it with higher overall efficiency, as previously mentioned.

 

Built by the American Ship Building Co. of Lorain, OH as hull # 715. Launched on July 15, 1916 as the EMORY L. FORD for the Franklin Steamship Co. of Cleveland, OH. Dimensions: 600’ loa x 60’ beam x 32’ depth; 7986 GRT, 6225 NRT. Capacity 14,000 tons. Powered by a 2,000 ihp triple expansion steam engine and three Scotch marine boilers.

http://www.boatnerd.com/pictures/historic/perspectives/RaymondHReiss/default.htm


Only made 10 knots with the 4300 hp desel as she made 10 knots with 2000 hp steam.

Granted it's easier to fuel with liquid than coal cars, but it took 4300 hp diesel to replace the 2000 hp steam, and that was a bunker-C diesel, not #2 fuel oil.

The Reiss Steamship Co. of Sheboygan, WI bought the vessel on April 7, 1965 and renamed her RAYMOND H. REISS. During the winter of 1965 - 66 the ship was repowered with a 4,320 bhp, 16 cylinder, four stroke Nordberg diesel engine, a bow thruster was installed and a controllable pitch propeller at Fraser Shipyards at Superior, WI. Tonnage changed to 8220 GRT, 6496 NRT.

 

http://www.electricyacht.com/products/gen-drive/
quote
Gen-Drive™
The new EY Gen-Drives offer the cruising sailboat or trawler unprecedented value. They retain the range offered by a diesel engine while adding the benefits of electric propulsion. In addition, they serve as a generator when at anchor. Their high output can greatly reduce engine runtime needed to charge batteries for propulsion AND house loads. Combined with high charge acceptance rate (CAR) batteries, lights, electronics and refrigeration can be accommodated without running the engine for 1 or more hours every day. With proper sizing, air conditioning can be supplied without the noise and fuel consumption of a constantly running ac generator.
end quote

 

But we don't know what the engine was putting out?
Just because it's a 4300 HP engine, doesn't mean it uses all 4300 HP.
More than likely, it was only loaded 50% or so of maximum power.

 

Hee Hee. it was broke down most of the year I was aboard!

 

and

I think you may still be missing the point here. Even the most high revving, low torque, internal combustion engine can produce very high torque at low rpm. All it needs is a gearbox, and that gearbox will be massively more efficient that the combination of a genset and electric motor.

Electric drives certainly have their place, and as someone who's built an entirely solar powered small river boat I am an enthusiast for electric power, but there is no getting away from the fact that, at the moment, any electric drive system is pretty inefficient in overall terms (primary energy input to propulsive energy output).

My small solar powered boat is woefully inefficient, for example. Around 1500 W of sunlight falls on the solar panels on the canopy in very bright conditions, yet only about 200 W or so makes it to the batteries, and only around 120 W makes it to the water as propulsive power. Luckily it only needs around 100 W to cruise at 4 mph, and as long as the operating duty cycle is such that the batteries have time to charge between cruising periods each day it should hold it's own.

 

is this your design, jeremy?
http://www.eco-rally.org/uks-first-solar-powered-ferry

 

"My small solar powered boat is woefully inefficient, for example. Around 1500 W of sunlight falls on the solar panels on the canopy in very bright conditions, yet only about 200 W or so makes it to the batteries, and only around 120 W makes it to the water as propulsive power"

I was under the impression that solar panels are now more efficient than photosynthesis. It certainly would not be possible while underway, to grow the vegetable matter necessary on board, convert it to bio diesel, and motor along almost indefinitely . I could be wrong but from what I have read I understand it is now possible to circumnavigate the world using current nascent solar electric technology, Ultimately which is more efficient or if you like "sustainable" a fossil fueled combustion system or a solar electric one?

 

Current PV panels are between twice and three times the efficiency of photosynthesis, but the very best plants at converting sunlight to energy only manage around 8%. This is the really big issue with bio fuels, you need far more land area to grow them than we have available, just because plants aren't great at energy conversion.

If you want to use land to produce energy then solar panels will produce far more for a given area.

 

Alas it's nothing so grand! I don't have any finished photos (and the boat is virtually in bits again having another experimental motor system fitted), but there is a discussion here covering part of the build: http://www.boatdesign.net/forums/boat-design/efficient-electric-boat-27996.html