Electric propulsion technology changes the way a ship transmits power from the main engine (prime mover) to the propeller and the way it manages and distributes
electrical power to both the propulsion and nonpropulsion loads.
History of Electric Propulsion Technology
It does not change the primary power source of the ship, which remains the diesel engine, gas turbine, or steam turbine.
The ship propulsion system with mechanical drive and reduction gears was first developed in the United Kingdom. Following the development of the first large electric motor and generator in 1910, electric propulsion for ships was developed in the United States and elsewhere.
Both systems competed against one another until 1920, when the British developed a lightweight, high-efficiency mechanical drive system, which dominated ship propulsion technology around the world for the decades that followed.
The U.S. Navy revived electric propulsion technology during World War II for destroyer escorts because the U.S. gear-cutting capacity at the time was insufficient.
The first electric propulsion for ice-going vessels was introduced around 1939, when the Finnish icebreaker SISU was delivered with a Ward–Leonard dc electric
propulsion system.
Since then, various types of electric propulsion systems have been used for hundreds of icebreakers and ice-going vessels with propulsion power
approaching 50 MW.
After World War II, mechanical drive technology continued to improve and remained dominant. Among warships, electric propulsion technology was widely adopted only for submarines, for which the diesel-electric power plant became the standard system. It permitted the submarine to propel itself submerged for limited periods of time on battery power, without access to the atmosphere for oxygen to burn diesel fuel onboard.
Start of Electric Propulsion Technology on large Cruise Ships
Electric propulsion technology was also reexamined for use on navy ships other than small diesel-electric submarines. On commercial ships, electric propulsion was used in a few large cruise ships, such as Normandie in 1936 and Canberra in 1960.
These experiments, however, periodically confirmed that electric propulsion technology, while promising, was not competitive with mechanical drive technology for large submarines and surface ships until the 1980s, when the technological developments in motors, particularly in power electronics motor drives, made electric propulsion potentially more cost effective than the mechanical drive for large naval ships.
In 1985, the United Kingdom began building the Duke class type 23 frigates, which used a combined diesel-electric and gas turbine-mechanical drive propulsion plant.
It used a lower-power diesel-electric propulsion system for quiet sonar-towing operations at speeds up to 14 knots and a gas turbine-mechanical drive for higher speeds up to the maximum sustained speed of 28 knots for these ships.
In 1987, the Queen Elizabeth II (QE2) cruise ship underwent an overhaul when its onboard mechanical drive system was replaced with an integrated electric power (IEP) system. This system was operated successfully and set the stage for widespread adoption of electric propulsion technology for cruise ships.
Today, most cruise ships in the world are being built with electric propulsion.
