Energy efficiency is the name of the shipping game these days. In addition to lowering operational costs, increased efficiency often translates to fewer emissions and can mean better compliance with environmental legislation. Over the last few decades, shaft generator systems have become a more common option to help ship owners and operators achieve profitability in a sea of fierce competition and keep those waters cleaner for future generations.
Shaft generators on board ships are driven by the main engine to supply power to the mains. The mains have to be supplied with constant voltage and frequency by the shaft generator whilst the speed of the main engine changes, i.e. when the vessel travels at different speeds or if the propeller speed strongly varies in heavy seas.
On ships with fixed pitch propellers, the speed is set via the propeller speed. If using controllable pitch propellers, the shaft speed and the propeller pitch are adjusted simultaneously in order to achieve optimum propeller efficiency in this so-called combinator mode. Even with this type of propeller, it is thus economical to use shaft generator systems with frequency converter for variable speed in order to permit combinator mode from pier to pier.
Benefits at a Glance
Due to the numerous advantages of shaft generator systems, more and more vessels are equipped with them. In summary, some of the greatest benefits include the following:
Lowering of fuel and lubrication costs
Reduction of maintenance costs and personnel on board
Return on investment in 2 to 4 years
Increased safety for ship and crew
Low noise power generation
Smaller or fewer diesel generator sets