Top thruster trends for ferries include energy efficiency, fast response and suitability for alternative propulsion
Schottel sales director cruise, ferry and yachts Andreas Witschel tells Passenger Ship Technology, “Fast thrust response and energy efficiency during manoeuvring is of the highest importance for owners. Therefore, we see more and more diesel, gas and battery-electric ferry concepts today where our vertically embedded LE driven thrusters are incorporated. Here the permanent synchronous motor technology is frequently applied due to the extreme compactness of these motors on top of the LE azimuth modules without interference to the deck above. Furthermore, the permanent motor technology shows a higher efficiency, especially under partial load, which is typical for ferry operation. This technology also weighs less than top asynchronous motors.”
Schottel has worked on a range of recent ferry orders where alternative fuels and propulsion is used. It has equipped the world’s first hydrogen ferry Hydra. Hydra, powered by a hybrid mix of batteries and hydrogen fuel cells, is equipped with two Schottel EcoPellers type SRE 340.
Mr Witschel says, “The SRE optimally meets Norled’s requirements as it ensures high efficiency even at very low loads. It is an ecologically friendly propulsion system developed primarily for open seas and coastal operating conditions. Thanks to its efficiency, the azimuth thruster also contributes to the ferries’ low fuel consumption, resulting in low operating costs and reduced emissions. Beyond this, the SRE improves course-keeping stability and thus reduces steering angle corrections.”
Another recent project is the ferry for Canada’s Kootenay Lake in British Columbia. It is equipped with four Schottel TwinPropellers type STP 150 to enable reliable crossings even in shallower waters. Based on the principle of the proven SRP, the STP ensures combined thrust and 360° manoeuvring power with its two co-rotating propellers.
Mr Witschel says, “Distributing the load over two propellers of equal diameter (and therefore across an increased propeller surface) boosts the propulsion system’s efficiency. At the same time, noise and vibration levels underwater and on board are reduced to a minimum.”
Elsewhere, Altera is the latest addition to FinFerries’ fleet. The high-efficiency propulsion system of the ferry consists of two electrically driven Schottel EcoPellers type SRE 430 (950 kW each) which are ice-strengthened.
Mr Witschel comments, “The hydrodynamically optimised design allows the EcoPeller to generate maximum steering forces and enables top values in terms of overall efficiency and course stability. This reduces fuel consumption and ensures both lower operating costs and emissions.”
Schottel has also been working closely with BC Ferries for many years, selected for both Salish-class and Island-class ferries.
Recent products include the Schottel LE-drive (embedded L-drive), which is compatible with electric motors of all types and manufacturers. This allows a free choice of electric motor for diesel-electric or purely battery-powered vessels and, thanks to its compact design, more freedom in vessel design compared with conventional Z and L variants.
Elsewhere, the new HTG bevel gear technology patented by Schottel is implemented into thrusters allowing the transmission of a higher torque at the same gear size and a great reduction of gear noise due to a cyclopalloid mesh. The sound-optimised propulsion units help to reduce underwater noise. For the pump jets, a new feature, the so-called CoaGrid, has been developed.
Mr Witschel says, “This exploits the Coandă effect. In combination with inhouse CFD optimisation, a new streamlined geometry below the pump jet housing was also developed. This allows the water flow to be better directed into the inlet of the pump jet, leading to higher efficiency and lower noise emissions.”
With the MariHub, Schottel offers a data acquisition and IoT gateway system. It records and analyses signals from sensors, machinery and other components which can then be evaluated by Schottel for the customer.
“With the condition monitoring service ProCMS, MariHub allows for early detection of irregularities in the drive train. This predictive maintenance approach significantly increases the availability of vessels: ProCMS can reduce maintenance costs and improve maintenance planning,” says Mr Witschel.
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