Hybrid Engine Systems and Sustainability

I think there is one Major problem in vast so called marine hybrid consepts. "Hybrid" is next to nothing and more like worst than conventional without a regeneration from vessel moving by the forces from waves or wind or some other forces like accelerations to damp and to convert damping to energy propelling a vessel it self. Have some sails, have wave energy "bull" or radically damp accelerations to be converted to propulsion forces by using hydraulics or pneumatics, maybe just foils. Diesel electric or full electric is "no go" with this battery "technology" we have still these days, quite same like 100 years ago. And You can go faster with less (keeping weight in reasonable extent) when cuttin accelerations by using more efficient hull designs with less deadrise when convert the unwanted vertical to energy propelling horisontal, for example....

 

Recovering energy through pitch damping is certainly a concept worth exploring, and I can see how the energy recovered might be used to drive a prop mechanically, Still it seems to me that that even with the present state of technology storing the energy, along with that recovered through all other means, in batteries, and using an electric drive should not be discounted.
Before sail there were no hybrids. In the age of sail if the wind ceased boats were lowered and the crew rowed. With the advent of steam it was possible to progress directly against the wind or in the absence of wind. The development of internal combustion engine and the availability of cheap petroleum allowed us to dispense with the sails and rely completely on one energy source and means of propulsion.
In today’s world there are no slaves to man the oars and if there were it would cost too much to feed them. Petroleum is no longer as cheap and certainly not readily available. On the other hand the wind still blows and the sun still shines and for when they don’t we have batteries.
Considering the title of this tread I think it is ironic that the main driving force behind the pursuit of hybrid technology is the perception that it is petroleum and internal combustion engine based technology that might not be sustainable.

 

Don't Throw out the Baby with the Bath Water

This diesel-electric subject thread has certainly raised some lively and controversial discussions. Many want to claim that converting diesel engine mechanical power into electricity, and then back into mechanical power by an electric propulsion motor, just isn't economically feasible. Therefore chuck the whole idea aside when contemplating DE propulsion systems for boats.

I say don't 'thrown out the baby with the bathwater'. This technology is still in its infancy, and there are many more developments to explore....and some may come with other emerging technologies.

One of these new technologies will likely be the ever-increasing capabilities to store electrical energy....new 'batteries', or other such devices and mediums. This capability to store large amounts of electric energy is a technology we sorely need for our future in all sorts of endeavors, and I'm sure there are presently 100's of experimenters around the world working on this major technology.

I agree Innamore. For a strictly powerboat application that spends a small amount of time idling about or maneuvering at docks, etc, and subsequently mostly at speed on the open water, D-E does NOT make sense.....too many energy conversions between main motor and the prop. Thus many powerboats are not applicable DE candidates.

But one thing those DE systems do is break the mechanical link between the engine and the prop. This opens up a whole lot of possibilities for locating the main engines apart from the drive-props, and even the variety of prop-drives that might be employed.

For vessels with big house loads, a DE systems approach makes sense, as well illustrated by the big cruise ships.

Special maneuvering desires can be accommodated with DE systems. A diesel electric system can be shifted from fwd to reverse and back much more quickly than a conventional transmission. In addition the electric motors develop full torque at any speed, even down to 0 rpm. In conventional propulsion installations, the idle speed of the engine will be between 700-1000 rpms. With a typical displacement hull reduction-gear ratio of approx 2.6 to 1, the slowest propeller speed is 270rpm or more. By contrast, a DE propeller shaft can be turned as slowly as 1-rpm!

Furthermore DE systems are much more adaptable to 'steerable prop-drives. Talk about maneuverability!!

If we move beyond ' strictly powerboats', then we might see a use for DE systems aboard wide variety of other type vessels. I'll just give two examples where I wish to use them:

1) Sportfishing Vessels.
Whether pleasure or commercial types, these vessels spend considerable time in the 'trolling mode', usually quite a bit below their cruising speed. This trolling speed might well be accommodated with a DE system.
Gamefishing Catamaran


2) MotorSailing Vessels.
In light airs, running one engine often is all that is needed to bring the apparent wind forward to make the sails work harder, and the combination provides much better results than either motoring or sailing alone…… sailing synergy/harmony, the motor taking over in the lulls and the rig taking over in the puffs

Motorsailing offshore is by far the most pleasant way to make passage, most of the time. With the engine barely above idle and a moderate amount of sail set, there is a synergy created by the apparent wind which generates more forward thrust than either one alone, with the bonus that you don't have to set large areas of canvas, which will have to come down in a hurry if the wind increases. The boat rides better, makes a better average speed and the batteries are always full. The beneft of using a much smaller sailplan can only be appreciated by someone who's been caught offguard in a squall with too much sail up. "Adventures" like that might be fun for weekend sailors and short coastal passagemakers, but on a long ocean passage they're something to avoid, even if it means a slower passage.
Motorsailing Catamaran

 

The engine will be harmed by overloading. Exhaust temps will go through the roof because full throttle will no longer allow the engine to reach full RPM. The engine will not reach PEAK rated HP but it will be at peak hp for the lower RPM it is able to develop.

 

The torque curve of electric motors is flat. They develop the same torque at 0 rpm as at 2000 rpm, hence the advantage of electric, and why a small hp electric motor can replace a larger internal combustion engine. The ic engine needs to be extra large enough to have sufficient torque at low rpm.

 

Thats not right either with respect to boats. Generally DC motors develop max torque at low RPM and torque goes down with RPM. If you look at a propeller power chart that is exactly the opposite of what is required. Hence any diesel engine usually has an excess of torque at low speeds which the prop can not convert unto thrust. The higher low RPM torque of an electric motor will be of no use here, unlike a car where it will aid with acceleration.

 

Exactly. The electric hp somehow being more than diesel hp is a total myth.

 

I think maybe with cars/bikes/buggies there might be some truth in that the usable power curve is more suitable. But certainly not with boats for the reasons I said.

 

Yes, spot on, and something frequently misunderstood.

Prop power increases in proportion to the cube of rpm (roughly), so pretty much any engine, even a highly tuned two stroke, will be able to develop more torque at low rpm than the prop can absorb.

A prop that absorbs 100hp at 2000rpm would only absorb about 1.56hp at 500rpm, for example.

 

The purpose of electric drive on sailboats is woefully misunderstood.

Maybe this site explains it better than I do.

http://www.propulsionmarine.com/

 

horsepower is not important to turn a prop. Torque IS!

 

agree

 

So you only need 1.5 hp if you only need 500 rpm and have sufficient torque to turn 500rpm!

 

Power = Torque x Rotational Speed
Torque = Power / Rotational Speed
Rotational Speed = Power / Torque

Depending on the units used for Power, Torque and Rotational Speed appropriate unit conversion factors may also be needed.

The relationships above hold for any and every operating point. They do not depend on on the source of the Power and Torque.

Sometimes there is confusion because different operating points are mixed; for example Maximum Power and Maximum Torque.

 

Thankyou Mr cockey