Your next yacht may be powered with a new, but at the same time old and extensively proven, power system-a diesel electric drive. First used in 1903 to propel the triple-screw Russian tanker Vandal on the Volga River and Caspian Sea, diesel electric propulsion is now used in the most modern cruise ships and in thousands of other commercial vessels. Although the idea of powering your yacht with the indirect, two-step diesel electric energy transfer system may appear to be unnecessarily complex, its many advantages can make it a compellingly attractive alternative to a conventional direct mechanical prop-shaft drive.
The benefits of diesel electric drive begin with the design freedom the system affords the yacht's designer. The engine can be installed wherever appropriate to achieve optimum use of space for the accommodation. Noise and vibration are more easily suppressed than in a conventional direct engine-to-propeller drive. Turning the props with electric motors enhances slow-speed maneuverability by providing unrestricted minimum prop speeds with 100 percent torque available to provide immediate power response at all times. Prop synchronization is automatic and extremely precise. When under way all of the electrical power required by the vessel can be supplied from the diesel electric propulsion system, eliminating the need to run a genset. A diesel electric power system can drive multiple propellers from a single engine or use multiple engines to power one or more props. In a twin-engine/twin-prop system, one engine can power both props when operating within the speed limits imposed in many areas. Electrical power from the vessel's genset can be used to propel the boat, providing a built-in backup-especially valuable for yachts with single-engine installations. Conversely, the propulsion system can serve as a backup for the yacht's gensets.
The more than 100-year history of marine diesel electric systems began as a response to the impossibility of quickly reversing the direction of rotation of early direct-to-prop-shaft-coupled diesel engines. With a diesel-powered direct current (DC) generator and a DC motor connected to the prop shaft, the direction of prop rotation could be controlled by a switch. The 100 percent torque, zero-speed capability of the electric motor led to the overwhelming use of diesel electric power for railroad locomotives. Diesel electric drives found a natural application in submarines and many surface ships. Today's cruise ships, where 70-80 percent of the total onboard power is required for the "hotel" side of the vessel, are diesel electric powered. The power demands can be enormous at times. A trivial example: 1,500,000 watts, equal to more than 1,400 hp, is needed to simultaneously power half of the 1,500-watt hair dryers on a 1,400-stateroom cruise ship.
While the equipment designed to serve the massive needs of cruise ships is unsuitable for any reasonable-sized yacht, numerous land-mobile applications including buses, very large trucks and the cranes used in container ports need power levels similar to those required by a yacht. These land-mobile applications require high overall efficiency, installation flexibility, virtually 100 percent torque at close to zero speed and must meet demanding reliability and durability standards. Fortunately, equipment designed and perfected for these uses is ideal for propelling many types of yachts.
