Page 63: of Marine News Magazine (April 2012)

www.marinelink.com MN63cially benefits vessels with Dynamic Positioning. Energy storage can also be used to absorb rapid power fluctu- ations seen by the diesel engines, thereby improving their fuel efficien- cy. The Onboard DC Grid is an open power platform which easily allows reconfiguration in number and types of power sources and consumers, power levels and other moderniza- tions. Alternative energy sources that will become significant during a typi-cal vessel lifetime of 20+ years will be easier to adopt in a vessel with Onboard DC Grid because they will not be bound to an AC system, nor will they require redesign of a main switchboard. DESIGNPRINCIPLESBy far the largest proportion of the total power load on board a vessel is for propulsion and thrusters. This power must be processed as a DC input to the variable frequency inverter that performs the speed con- trol of the motor. Actually distribut- ing at a DC level allows the losses in a switchboard and transformer to be eliminated from this power flow. - When diesel-electric generators run at constant RPM with control of the power delivered, fuel efficiency is compromised. In a DC distribution system the generator and diesel speed can be var- ied to achieve the optimum fuel effi- ciency at every power level. Each power source and consumer on the Onboard DC Grid is an AC or DC island? and the only connection between them is the DC bus. This yields two advantages: Each power source and consumer can be con- trolled and optimized independently. Complex interactions that can arisebetween units that share an AC con- nection will never occur. Consumers fed by the Onboard DC grid are designed not to interact even under fault conditions. AVAILABLE NOWAs MarineNews went to press, ABB had recently won an order from ship owner Myklebusthaug Management to supply the first ever direct current (DC) power grid on board a ship. ABB will provide its full onboard DC system, including all power, propul- sion and automation systems for the93 meter long, 5,000 ton multi-pur-pose oil field supply and construction vessel, which is scheduled for delivery in the first quarter of 2013. www.abb.com/marine Marine Sanitation SystemsWastewater Treatment SystemsWastewater Treatment Systems for Commercial and Marine Applica
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