Class approval by ABS will open the market for more hybrid propulsion tugboats. ABS has granted approval in principle for Rolls-Royce’s hybrid propulsion system for tractor tugs.
This approval was offered after inspecting the hybrid propulsion system on Baydelta Maritime’s new tractor tug, built by Nichols Brothers Boat Builders in the US to assist the new generation of ultra-large container ships.
This tug was designed by Jensen Maritime and constructed to comply with ABS rules for building and classing steel vessels of under 90 m. It also complies with ABS Advisory on Hybrid Electric Power Systems and ABS Guidance Notes on Review and Approval of Novel Concepts.
Nichols Brothers is due to deliver the tug in February 2019 to Baydelta, when it will enter service at US west coast container terminals.
The approved Rolls-Royce hybrid propulsion system on this tug consists of power take-in units, electric motors, and main propulsion engines connected to Rolls-Royce azimuth thrusters.
Hybrid units enable tugs to be operated in either a diesel-mechanical, diesel-electric or boost mode configuration. Rolls-Royce senior vice president for commercial marine in the Americas, Griff Lane said Baydelta’s hybrid tug will be capable of safe and reliable operations and maximum bollard pull.
“Our hybrid system enhances the tug’s escort capability, providing assist support to the ultra-large container ships that operate from US west coast ports,” he said.
“The key benefit of a hybrid configuration is that it reduces the power requirement,” Mr Lane continued. “Typically, a tug the size of the Baydelta vessel would need a power output of 2,500 kW. The hybrid arrangement allows operators to achieve the required bollard pull from a smaller engine.
“It provides greater operational flexibility which allows for the system to provide improved fuel efficiency, redundancy and reduced emissions,” he explained.
ABS’ approval helps confirm the safety and functionality of the Rolls-Royce hybrid tug concept, said Rolls-Royce vice president for integrated ship systems Atle David Monsen. Integration between engines, electrical equipment, thrusters and automation systems is crucial in hybrid vessels.
“With a system integrator, the risk and complexity for both owner and yard is significantly reduced,” said Mr Monsen.
For the Baydelta tug, Rolls-Royce supplied all electric motors, shaft generators and a power management and control system. This hybrid arrangement provides power to a pair of US255 azimuth thrusters, which feature ducted fixed pitch propellers that can be rotated 360˚ around the vertical axis.
Rolls-Royce said this arrangement optimises omni-directional thrust and manoeuvrability and improves the crash stop capability of a tug.
In August, Rolls-Royce launched a lithium-ion based energy storage system for use in marine applications including tugs and offshore support vessels.
ABS has co-operated with Jensen Maritime this year to develop methods of using 3D models of tugs for class approval of vessel designs.