Electric rim thrusters can offer a number of benefits over more traditional propulsion systems, such as low emissions and reduced noise, said German firm Schottel, which has released a high power density, 500kW version of its SRT thruster, the SRT-R.
The firm noted that through extensive use of CFD (computational fluid dynamics) the hydrodynamic design of the blades has been optimized to minimize cavitation. The thruster can be orientated 360°, yet when retracted, does not add to the drag of a vessel’s hull. The SRT-RT version can also be used as a transverse thruster when retracted, which is useful in shallow water operation.
Key to the power density of the thruster is the motor layout, whereby the motor stator is situated in the outside part of the thruster tunnel, with the blades attached to the inside of the motor rotor, meaning a motor does not need to be packaged around the propeller hub. This layout also aids cooling as the rotor and stator both have water flowing over their external surfaces.
Further aiding the environmental credentials of the new thruster, the SRT-R also offers the option of using biodegradable oils, making vessels fitted with it compliant with the current VGP regulations of the US Environmental Protection Agency.