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Zurich-headquartered power and automation technology group, ABB, says recent modifications to its Azipod propulsion unit frame design have led to an improvement in hydrodynamic efficiency of more than two percent.

The improvements are the result of an optimized Azipod fin shape and a new pod cap structure, called X-tail. The newly-designed fin structure receives water flow from the propeller at a less acute angle than its predecessor, and its new curved design redirects the flow more efficiently. The unit's new X-tail straightens the flow of water on ejection from the Azipod propulsor, minimising swirling.

Royal Caribbean International's Radiance of the Seas was the first cruise ship to install the modifications during a drydock in May 2011. According to ABB, the vessel’s subsequent sailings between May and September resulted in a two percent improvement in hydrodynamic efficiency compared to a sister vessel and its own previous operating portfolio.

The new features will now be included in new Azipod XO units and can be refitted to existing vessels equipped with older Azipod VO and XO units.

“The fuel efficiency improvements measured on Radiance of the Seas are a welcome reprieve in today’s higher fuel prices,” remarked Anders Aasen, associate vice president of technical services for Royal Caribbean International and Azamara Cruises. “Any improvements we can make on fuel efficiency will serve us well for future operational costs.”

Tomi Veikonheimo, chief hydrodynamist at ABB Marine, commented: “Azipod propulsion has been in the market about 20 years and a lot of hydrodynamic improvements have been made during that time. However, from the hydrodynamic point of view the system still has a lot of potential. More new ideas will be studied, tested and applied to improve ship fuel efficiency.”