The PTO/PTI solution consists of two GE motor-generator sets that sit on the two propeller shafts while connecting to the GE MV7000 drives. During PTI mode, the motor-generator sets play the role of an electric propulsion system that provides additional motor power - beyond that of the main diesel engines - to propel the vessel.
When the need for propulsion power is reduced, the motor-generator sets switch to PTO mode, harnessing the mechanical energy from the shaft and converting the otherwise wasted energy into electricity to generate power for electrical equipment onboard the vessel, reports Diesel & Gas Turbine Worldwide journal of Waukesha, Wisconsin.
"Typically, one diesel engine can consume as much as eight tons of fuel per hour. Saving even just one per cent of fuel will generate significant savings for the customer, said Marine Solutions project chief Bruno Daubas.
"The two modes are completely reversed processes and, therefore, require robust drives and software to ensure a smooth switch between two modes and to react in a highly responsive manner. During the sea trial of Madrid Maersk, when the modes switched, all equipment kept running without the slightest interruption."
GE's Marine Solutions also provided its digital software solution, Power Management System, to automate the operation. The software is connected to all generators onboard the vessels and, based on the required sailing speed, will optimise fuel usage.
The four containerships to be fitted with the technology are the Madrid Maersk, which is the first container vessel delivered from Daewoo Shipbuilding & Marine Engineering in April 2017. Munich Maersk and Moscow Maersk have both completed successful sea trials, while Milan Maersk will soon be in service.
Said Maersk Line project manager Steffen Hartvig Nielsen: "GE's propulsion and software system creates energy savings and is helping us achieve our sustainability strategy, which aims to reduce carbon emissions per container vessel by 10 per cent."