Norwegian Ferry Propulsion Retrofit a Money Saver
Rolls-Royce has won a contract to supply its Promas Lite propulsion system to the Norwegian ship owner Hurtigruten for their cruise ship MV Richard With. Propeller efficiency improvement for the ship is estimated to be between 11-14 per cent at 15 knots.
MV Richard With: Photo courtesy the owners
Promas Lite is a version of the Rolls-Royce Promas integrated propeller and rudder system which is designed specifically for vessels already in service. It is well known that with advances in propeller design, propeller blade changes, or the fitting of new propellers, can have a significant effect on propulsive efficiency, fuel consumption and, therefore, emissions.
With Promas Lite these improvements can be maximised, as the propeller and rudder are treated as a complete system, and further increases in efficiency can be achieved with improved manoeuvrability for only a small increase in cost. First, extensive modelling work is carried out at the Rolls-Royce Hydrodynamic Research Centre in Sweden to refine the design in order to deliver optimum fuel economy and performance.
In the retrofit process the existing rudder is retained, but is fitted with a prefabricated bulb, while the new propeller is equipped with a special hubcap and new blades. The propeller is designed to utilise the fitted bulb and is matched to the vessel's current operational profile, which may have changed since the vessel was built. Rolls Royce say that installation of a complete Promas Lite upgrade kit can normally be undertaken within a normal 7-10 day docking period.
Propulsion system 'Promas Lite': Image courtesy of Rolls-Royce
The MV Richard With was originally equipped with twin Rolls-Royce controllable pitch propellers (CPP). With the installation of Promas Lite propulsion, Hurtigruten will receive up to 80 per cent of their total investment from the Norwegian Government's NOx fund, which encourages ship operators to invest in technology that will reduce NOx emissions.
Rolls-Royce have documented a case study of a PromasLite propulsion system that was installed in the DFDS cruise ferry Pearl Seaways operating on the Copenhagen-Oslo route. A twin 4.8m Promas Lite propulsion system was installed during the vessel's regular dry-docking at Fayard shipyard in Denmark in early 2011. The existing CPP blades, originally designed for a higher operational speed, were replaced by blades specifically designed to maximise the efficiency of the Promas Lite system.
Subsequently vessel performance was then monitored over a period of normal operations. The DFDS Technical team calculated the efficiency improvement to be up to 12.5 per cent, representing a payback time of about 1.5 years.