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A to Z of azipods: revolutionary new propulsion systems drive 21st century cruise liners
Cruise Travel, May-June, 2002 by Phil Shapiro
One of the many criteria that the cruise lines considered in choosing the engine type was the environmental impact of the exhaust smoke from ship funnels. Environmentally friendly, smokeless power-generation systems release no soot or visible smoke. Smokeless engines for the power-generation system would be ideal. Royal Caribbean's Radiance Class and Celebrity's Millennium Class ships have advanced-design turbine engines that approach this smokeless goal, partly by using a more refined, cleaner-burning fuel. Carnival has taken a different tact, developing smokeless diesel engines called EnviroEngines. These newest ships from Royal Caribbean, Celebrity, and Carnival are probably the most environmentally friendly cruise liners sailing today. Planet watchers should be pleased.
Another advantage of the azipod system is increased fuel efficiency, which, according to Holland America, allows its 61,000-grt Amsterdam to save "up to 40 tons of fuel per week." This is primarily due to the overall improved efficiency of the azipods. In classic installations, where propellers are attached to drive shafts, the rotating shafts set up a swirl in the water preceding the propellers--a situation analogous to sailing upstream. The arrangement of the azipods with their front propellers working in water not distributed by shaft lines is more like a ship sailing on a lake. Another way the azipod-propelled ship achieves greater fuel efficiency is through the use of the latest materials--many stronger and lighter in weight than were used in construction in an earlier era.
Also, ships with azipod systems have higher cruising speeds, not always concurrent with fuel conservation, which may result in more or longer port calls. This also allows some lines to have itineraries with ports at greater distances from each other. Norwegian Cruise Line's Norwegian Star provides year-round Hawaii service with a visit to Fanning Island, Republic of Kiribati, about 600 miles from Hawaii, for a day at the beach. Traveling at about 25 knots, the Norwegian Star covers the distance in just 24 hours, giving passengers two sea days--and a remote island call--on a seven-day cruise.
Initial inferences by the cruise lines that there would be space savings with the new azipod system have not materialized in passenger areas. When queried, Carnival public relations personnel responded, "Please be advised that we didn't actually `save' space; the space is used for other purposes, such as a second incinerator. A parallel benefit was the reduction in mechanical equipment. Azipods allow us to delete shafts, shaft bearings, rudders, thrusters, and associated equipment, which reduces maintenance and improves efficiency."
Engineers report that azipod systems have quieter power plants than those of the last generation. Their electrical power generators, although within the hull, are more vibration free than former installations, resulting in a quieter ship. Acoustic design using sound insulation helps further reduce any power-plant and propulsion-system noise, improving in-cabin passenger comfort. Onboard noise also is lower because azipod propulsion motors are mounted outside the ship's hull.
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