Diesel-electric powered offshore vessels are becoming more and more common, with most of them using azimuth thrusters either for main or auxiliary propulsion during dynamic positioning. The thrusters in use are generally mechanical geared thrusters with horizontal power input, and in some cases, electric pod systems.
Both systems have their pros and cons in respect of size, space requirements, and initial and operational costs.
Schottel has developed a symbiosis out of a mechanical Rudderpropeller and the basic design features of a pod drive in order to gain the advantages of both systems, and in turn combine them into one new product using well-known reliable techniques.
In contrast to pod drives with an electric motor inside the underwater pod, the motor in the Schottel Combi Drive (SCD) is integrated vertically into the support tube of the Rudderpropeller. Neither an above-water gearbox nor a shaft line is required, making the system extremely compact and easy for the shipyard to install, particularly in a vessel with very limited space.
Offshore support vessels (OSV), anchor-handling tug supply vessels (AHTS), seismic research vessels, cable ships and other work vessels are ideally suited to this propulsion solution. The space saved by the diesel-electric concept, together with the flexible design of the vessel’s interior, result in a substantial increase in the usable volume.
This is of particular importance with such complex offshore vessels, and increases their economic efficiency. Environmental friendly propulsion solutions are becoming more and more popular, particularly in harbours, where the amount of pollutants emitted by conventional diesel engines is considerable due to operating in the unfavourable partial-load range.
Under the working title of “Green Tug”, diesel-electric concepts for harbour tugs have been developed in the USA and the Netherlands with government support. Moreover, major tug operators worldwide are working on green tug concepts using the Schottel Combi Drive for main propulsion.
The compactness of the Combi Drive makes it an optimum solution for diesel electric tugs where all of the additional components needed for diesel-electric drives take up the limited space, making a compact propulsion system necessary.