In recent months, several of the largest thruster manufacturers have launched new products with environmentally-friendly credentials
The rising demand for hybrid propulsion is reflected in the latest offerings from Caterpillar, ZF and Veth and Rolls-Royce, with the latter also experimenting with permanent-drive magnets.
After four years in development, Rolls-Royce has launched two pod-propulsion units designed to meet consumer demands for more compact systems.
Rolls-Royce’s ELegance pod-propulsion units have been designed to meet consumer demands for more compact systems
Called ELegance pods, one is an open propeller and the other is a ducted configuration, but both are designed to fit with Rolls-Royce's new proprietary battery propulsion system.
Rolls-Royce product manager Per Nahnfeldt said the company was “responding to growing electrification trends”.
The ELegance pod designs are based on a permanent magnet thruster design. This provides up to 99% efficiency through a motor drivetrain that offers low vibration and minimised noise, thanks to few moving parts and a low aspect ratio.
The twin-tail design reduces cavitation and noise vibration while increasing efficiency.
“For many years we have recognised the gap in the propulsion market for smaller pods, including ice-class, in the 1.5 MW to 7 MW power range,” said Mr Nahnfeldt. “These new pods – based on our permanent magnet technology – complement our broad product portfolio and sit well with our range of frequency drives and electrical systems. We can now provide a complete, fully electric propulsion package.”
In addition to the integration with the new battery system, the pods are linked to the Rolls-Royce Health Management system, which is geared towards a future of autonomous shipping, according to Mr Nahnfeldt.
“All of our products are built to make sure we can meet the requirements of autonomous vessels,” he said.
Mr Nahnfeldt said the cruise sector was a target market, along with platform supply vessels; he said a pilot version of the propulsion unit is under construction in Finland, due to be launched at the end of 2018. He also explained that Rolls-Royce has “several customers” signed on to the pilot project to test the pod and noted the design was underpinned by the company's Mermaid pod design, that has more than 50 units in operation and over 4M operating hours to date.
Meanwhile, Caterpillar Marine has announced a new generation of azimuth thrusters, the MTA v3.
Based on the existing v2 design, the MTA v3 is designed with hybrid systems in mind and aims to boost fuel efficiency and give customers the best operational modes for their performance needs.
The v3’s hybrid interface means it can switch between mechanical and electric power easily, allowing users to achieve high average engine loads by running only the necessary engines or generator sets.
Users can select between standby and low-speed transit, high-speed transit and light towing, full power and firefighting modes.
The new line is 20% lighter than its predecessor, with 27% less oil volume, increased power density of 25% and a 3% bollard pull increase. Auxiliaries, such as the hydraulic power pack, gravity tank, cooler and clutch hydraulics are integrated into the azimuth unit itself, giving it a smaller footprint overall.
Thrusters from Cat’s 3500 range, including the MTA 524, MTA 627 and MTA 628, are available in MTA v3 versions at power ranges from 1,500 kW to 2,525 kW.
Caterpillar Marine’s tug and salvage segment manager Jorgen Karlsson said: “The addition of the new MTA v3 to our marine product programme really completes our offering to the tug segment and provides a leaner, simpler and more efficient integrated solution to our customers.”
The first Veth integrated L-drives were installed on Damen's utility vessel Volt Processor
Elsewhere, Veth’s first integrated L-drive propulsion system has gone into service. The L-drive is part of a diesel-electric configuration that provides propulsion and vessel power.
The first installation of an integrated L-drive is on a Damen Shipyards-built utility vessel operated by Remoy Management, which completed sea trials at the end of April.
Veth supplied a compact electric propulsion solution to Volt Processor, which uses 750 kW of electric power for propulsion, positioning and driving deck machinery. Integrated L-drives are suitable for other types of hybrid-powered workboats and tugs and could be used for dynamic positioning.
A water-cooled permanent magnet motor is integrated in the slewing bearing, said Veth general sales manager Martin van der Jagt. The mounting method, the alignment of the headsets and adjustments to the control box make this integrated L-drive extremely compact he said, adding, “The difference in height between a traditional L-drive and the integrated L-drive is about 2 m”.
Mr van der Jagt said the integrated L-drive is more efficient in part-load modes than other hybrid propulsion units because the permanent magnet motor is water cooled, rather than air cooled. At 25% load, the improvement in efficiency with this motor is 5.2%, while it produces less noise than an air-cooled asynchronous motor, according to Mr van der Jagt.
Veth’s integrated L-drive is available with power ranging from 300 kW to 2,350 kW.
ZF Services has announced its latest propulsion range of thrusters and hybrid transmission systems for workboats in July. It included the ZF AT 3000 retractable thruster that can be used as an auxiliary propulsion system for increasing speed and bollard pull, or improving station keeping capabilities.
Another development from ZF Services is the ZF 3300 transmission, with a power take-in (PTI) as an alternate power source. This is the latest in hybrid-ready propulsion technology from ZF Services for workboats and leisure vessels.
ZF 3300 PTI has a power range of up to 1,940 kW (2,600 hp) derived from a standard diesel engine input or a PTI power source. This which means ZF 3300 PTI has the flexibility to be integrated into a wide variety of hybrid vessel propulsion solutions.