VESSEL REPORT Tugs
Hybrid Hype? The concept of multiple inputs for tugboat power continues to evolve.
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nytime there’s a legit, suitably notable “first-in-theworld” introduction, it’s usually a big deal. Such it was on a rainy day in 2009 when Foss Maritime unveiled the world’s first hybrid tug, the Carolyn Dorothy. About 300 guests heard speakers from Foss and the ports of Los Angeles and Long Beach tout the new environmental cred of the tug, which was the point of the ports’ $1.3 million grant money that helped build it. The tug’s hybrid concept was developed after Foss analyzed its harbor tugs’ duty cycles in LA/LB and realized that maximum power was only needed a small part of the time, but the 78'×34' tug would still need to have about 60 tons of bollard pull. Foss and its partners, which included Cummins Northwest, Seattle; Robert Allan Ltd., Vancouver, B.C., the vessel designer; and Aspin Kemp & Associates (AKA), a
In 2009, the Carolyn Dorothy was touted as the world’s first hybrid tug.
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Canadian electrical-engineering company, came up with a plan to tailor the tug’s power generation to fit the need at any given moment. This new hybrid idea combined conventional mechanical drives with electric drives. With motor-generators installed in-line behind the main engines and in front of the Z-drives, power from both batteries and diesel generators could all throw horsepower into the drive shaft. And conversely, the motor-generators could generate juice when spun by the main engines. For the Carolyn Dorothy, the full combination included two Cummins QSK50, 1,800-hp diesel engines, two Cummins QSM11, 300-kW gensets, two Siemens 1,200-hp/895kW motor-generators, and 126 12-volt, lead-acid batteries. When standing by or slowly transiting, maybe only the batteries or one of the gensets would be required. Other times, maximum power meant all of the above. Operating in different modes would reduce fuel consumption and lower emissions.
Foss Maritime
By Bruce Buls, Editor-at-Large
www.workboat.com • JULY 2022 • WorkBoat
