Is Diesel Electric Propulsion the right choice?

By Luiz Pustiglione, [Caterpillar](http://
As a concept, diesel electric propulsion (DEP) is not new. Diesel Electric Systems have been in use to propel vessels for more than 100 years. Branobel launched the first diesel-electric ship in 1903, and since that day, diesel electric propulsion systems have evolved and today they can be found in all boat sizes and applications. But how do you know when to utilize diesel electric technology for your vessel?

If we analyze marine construction over the last 3 years, we can see that investment in DEP vessels have doubled, while the construction of purely mechanically propelled vessels have slowed down. But what are the reasons for this growth?

Some of the benefits of the DEP systems are:

[B]Effective design:[/B]
The ability to locate your generators in any part of the vessel independent of where the power will be used;
[B]Smaller Engine Rooms:[/B]
Possibility to replace a big slow speed engine with multiple smaller generators;
[B]Reduced Noise & Vibration:[/B]
No need for long drivelines;
Capability to share the power of one unit with multiple devices (main propeller, bow thrusters, hotel load, pumps, etc);
Generators can be reassigned to cover any machine downtime;
Depending on the application the DEP system can provide better fuel efficiency (mainly if there are requirements for long periods of low speed/load)

As a consulting/specifying engineer or marine architect, what are the applications or situations in which you recommend the use diesel electric propulsion?
What other advantages or disadvantages do you see with Diesel Electric Propulsion?
What are some rules of thumb you would advocate to suggest the utilization of DEP versus Mechanical Propulsion?