Hybrid Engine Systems and Sustainability

Spot on.

The hybrid diesel/electric drive would have (roughly) 10 - 15% loss in the diesel to electricity conversion, a further 10 - 15% loss in the electricity to prop shaft power conversion, so 85hp at the engine gives between 61.5 and 68hp at the prop.

The direct gearbox drive has roughly 5 - 10% loss, so 85hp at the engine ends up as about 76.5 - 80.75hp at the prop.

In simple terms, the gearbox drive is a fair bit more efficient, in simple mechanical/electrical efficiency terms.

 

Apologies in advance if this has been covered in the thread and I missed it, but as Jeremy Harris summarized above, a direct drive (through gearbox or not ) diesel straight to prop will always be more efficient than an electric generator/converter/motor arrangement.

Where the electrics and hybrids start winning is when the comparison is expanded to include more 'real world' scenarios than simply a single design point. For example, the cruise industry were one of the first to adopt this technology on a large scale, and for them it seems to make sense as the power requirements that have nothing to do with moving the ship through the water tend to dominate the load analysis. The flexibility to bring generators online when required, and to run them at ideal efficiency, makes up for additional losses previously described.

Additionally, if electrochemical energy is to be stored via batteries, that opens the door to 'alternative' fuel sources such as solar, wind, fuel cell, spinning prop, etc., that help to make the case for the more complex, but possibly cleaner/greener, energy usage plans.

 

Lets look at an imaginary 10 x 40 ft boat.
Lets pretend we could cover the entire surface with PV panels.
That works out to around 37 square meters.
PV panels that the average person could afford, are about 20% efficient, so if you were somewhere that sunlight provides an actual 1000 w/ per square meter, you could harness about 7500 watts of power. This is in absolute ideal conditions. The kind of conditions that almost never exist on average.
If you could get that power to a 100% effecient motor, you could potentially get about 10 HP out of it.
Problem is, you rarely get 1000w/ m3 of light, you can't buy a 100% efficient motor, and you also can't likely have a boat where the deck is 100% solar panels.

Wind power?
Sure, you could build a boat with a crazy heavy keel like a sailboat, and put up wind towers. Expect about the same power output as the solar, for what you could actually mount on a boat.

Oh, but you want to just store it in batteries to use later?
Electric motors can use up to 100ah of battery reserve at 12v, PER 1 HP.
That means an expensive 250$ 12v EV battery with a 100ah reserve, is good for barely 1 hp for 1 hour.
To run a 50 HP motor for only 1 hour, you're looking at roughly 50 * 70 lbs per battery, or about 3500 lbs of batteries.


I think this all clearly shows, it is not practical, unless you happen to be working on a science experiment styrofoam boat.

 

I believe you were the guy I quoted above,
I also didn't realise marine transmissions were 90-95% effecient, I suppose it makes sense, they have less gears spinning in fluid than a car transmission.

I think that the few boats we do see with electric motors, are built that way for manuverability, not effciency.
-OR...

A GIANT propellor, that the engine can spin at hull speed, but not while towing or pushing an additional load, as a tugboat would do.
Picture a 40 ft long trawler type boat, where it would only take under 100 hp to push 8 knots.
Normally a boat that size might have a prop about 16" to 24" diameter.(roughly)
Let's say we find a 48" diameter propellor desinged to push a boat at 8 knots.
Using an alternator/ eletric motor, we could now actually UTILIZE the TQ of the electric motor to actually do work. We could now push a lot of weight, or tug a larger boat along, at lower speeds, very much like a CVT transmission.
This is still not an "end all solution", as the giant propellor would waste energy to spin in the water, over a smaller one.
But, for a tug, or boat that spends a lot of time trying to apply tractive force (pushing on something that isn't moving much), this would make sense, over a complex gear box.
That is the reason trains use diesel electric systems, not that it's more energy effecient, but it simplifies design, and is capable of applying huge tractive force to get a train moving.

Boats are the opposite of a train, they take less power to get moving, but more power to KEEP moving.
Thus, in general, it should be true, that the system used on a train, would have limited success on a boat.

 

"Lets look at an imaginary 10 x 40 ft boat.
Lets pretend we could cover the entire surface with PV panels.
That works out to around 37 square meters.
PV panels that the average person could afford, are about 20% efficient, so if you were somewhere that sunlight provides an actual 1000 w/ per square meter, you could harness about 7500 watts of power. This is in absolute ideal conditions. The kind of conditions that almost never exist on average.
If you could get that power to a 100% effecient motor, you could potentially get about 10 HP out of it.
Problem is, you rarely get 1000w/ m3 of light, you can't buy a 100% efficient motor, and you also can't likely have a boat where the deck is 100% solar panels."

In 2007 before the advent of today's lithium ion batteries and 21% efficient flexible ultra light weight solar panels the "Sun 21" a real 14 meter solar electric cat equipped with full cruising gear for six, crossed the Atlantic at an average speed of 5 knots.

 

Proving it cane be done, and proving it can be done feasibly, are two totally different things.

There are cars that have been built to run on solar panels, but I sure as heck am not bolting any solar panels to the roof of my truck anytime soon.

 

I like TEG better than solar panels.

 

http://www.ybw.com/forums/showthread.php?70031-what-size-outboard

quote
After a similar experience this summer we bought a Seagull Forty Plus which, clamped onto the stern of our 9ft tender, lashed alongside, moves our 10 ton displacement boat quite creditably.

I recall that Don Street gets "Iolaire", larger and engineless, about, using just this method.

The reason for lashing the tender alongside rather than trying to fit the outboard on the yacht is that a little wash or small waves will swamp an outboard attached direct to the parent yacht.

Seagulls are favourite for this as they give a lot of thrust, don't overheat when used in this way, and can sit in a locker for years until needed.
end quote

Seagull s 5hp gas with 5 blade 11x10 prop and 4:1 reduction.
But I doubt ANY IC engine actually produces the hp claimed for it.
Electric motors mfgrs more accurately rate their motors IMHO

 

The power of an engine may be measured or estimated at several points in the transmission of the power from its generation to its application. A number of names are used for the power developed at various stages in this process, but none is a clear indicator of either the measurement system or definition used.

In the case of an engine dynamometer, power is measured at the engine's flywheel. With a chassis dynamometer or rolling road, power output is measured at the driving wheels. This accounts for the significant power loss through the drive train.

In general:

Nominal is derived from the size of the engine and the piston speed and is only accurate at a pressure of 48 kPa (7 psi).[18]
Indicated or gross horsepower (theoretical capability of the engine) [ PLAN/ 33000]
minus frictional losses within the engine (bearing drag, rod and crankshaft windage losses, oil film drag, etc.), equals
Brake / net / crankshaft horsepower (power delivered directly to and measured at the engine's crankshaft)
minus frictional losses in the transmission (bearings, gears, oil drag, windage, etc.), equals
Shaft horsepower (power delivered to and measured at the output shaft of the transmission, when present in the system)
minus frictional losses in the universal joint/s, differential, wheel bearings, tire and chain, (if present), equals
Effective, True (thp) or commonly referred to as wheel horsepower (whp)
All the above assumes that no power inflation factors have been applied to any of the readings.

http://en.wikipedia.org/wiki/Horsepower

 

and do you think that the losses of a car's transmission, and differential + powers teering pump and AC are relevant when talking about boats?
Jeremy has covered the transmission losses in his examples (smaller than equivalent losses for the electric motor). Boat's transmission is simple reduction gear with far less going on compared to the drive train of a car.

You obviously just have decided that electric is better. !st its the super sweet low end torque - when its pointed out that its useless for normal boating use you move on to finding another angle. Suite yourself.

 

SERVICE FACTORS:
Motors are available in either NEMA or 1.0 service factors. A 1.0 service factor motor will perform to its nameplate rating. A NEMA service factor motor can exceed its horsepower rating periodically. (See table under NEMA Service Factor Ratings.)

http://www.rselectricmotors.com/terminology.html

 

Thats a brand specific argument.
Electric motors are also rated their HP at a certain temperature, so if they get worked hard, they don't make as much power as advertised.

You keep thinking of the electric motor as propulsion engine, when in fact, in a boat, it is closely resembling a transmissions duty's than an engines.
There really isn't many situations at all where a boat is propelled using batteries, other than a small trolling motor which puts out a screaming 1/3hp.

So since most of the boats employ the electric system as a transmission, rather than an engine, take a look at a regular old mechanical marine transmission.
-Cheaper
-More reliable
-More energy efficient

What can electric do for you?
-Massive low end torque (Almost impossible to make any use of)
-Can run on batteries (If you can pull a barge behind you're boat, with hundreds of batteries... yay for the TQ! lol)
-Science projects

 

I understand all the engineering wisdom promulgated.
I'm not an engineer, just a captain with 44 years sea experience on many types/sizes of vessels.

I believe from experience, that diesel electric has advantages in certain applications.

obviously, I'm not alone, because there are numerous diesel electric powered ships still being constructed.

For my own boat/boats, i'll use diesel electric.

I just don't see the "IC engine reduction gear is best in all cases" is any more valid than if someone claimed 'electric best in all cases". which I am not claiming.

 

Isn't the thread hybrid engine systems?
or is it a Hybrid won't work thread?

 

Electric motors have a place; azipod thrusters.
While the power coupling might not be as efficient as a gear box, the design allows the placement to overcome that burden.