Marine Log - August 2008 - (Page 32) POWER & PROPULSION tricity generated is supplied by the ship’s main switchboard and used in both a Siemens shaft motor/generator that assists in ship propulsion, and for powering shipboard services. A portion of the steam from the exhaust economizer is used for shipboard heating. Siemens explains that using a selfshifting coupling, the power turbine acts on the same turbine shaft that drives the generator. Surplus electrical power can be fed back as mechanical power onto the propeller shaft (shaft motor operation). Power take off operation is also possible. It is possible to operate the heat recovery plant at low main engine load and permanent parallel operation with a diesel generator set. When operating at full engine load, the surplus electrical power generated can be used in full to assist the main engine by feeding back shaft power onto the propeller shaft via the shaft motor. The shaft motor, says Siemens, acts as a variable consumer. In case of a turbogenerator trip, the shaft motor switches over to generator operation and keeps the mains alive without blackout. The good results from the first series of ships built with the system led to the creation of a consortium, including Siemens, Peter Brotherhood (now part of Dresser Rand) and Aalborg Industries. This consortium offered owners and shipyards the system as a package with and guaranteed performance levels. Siemens has assumed the consortium leadership. Siemens says that its SISHIPCIS Boost (the shaft motor/generator part of the package) plus WHT: • Reduces energy costs by about 12% • Requires less auxiliary generator maintenance • Requires less main engine maintenance • Means fewer emissions • Provides more cargo space (less bunker capacity needed). ML Siemens and a consortium of other equipment manufacturers involved in supplying the Maersk WHR systems are now offering a WHR package (left) 32 MARINE LOG AUGUST 2008 www.marinelog.com www.marinelog.com
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