An integrated permanent-magnet electric motor lowers efficiency losses, installation space, oil use and maintenance costs
Voith Turbo Marine has developed an electric version of its Voith Schneider Propeller (eVSP) for tugboats providing emissions-free towage and ship manoeuvring.
It has a powerful permanent-magnet electric motor to convert electrical drive power into thrust with virtually no losses, delivering high torque and fast response without a gearbox.
Voith Turbo Marine vice president of research and development Dirk Jürgens says this robust electric propeller reduces maintenance requirements, cutting costs for servicing and lubricant oil, improving its ecological footprint while decreasing operating expenditure.
“Demand for eco-friendly propulsion systems is continuously increasing,” he says. “In this context, we are also registering growing demand for the eVSP, which is ideally suited for use in tugs and various offshore and special ships’ applications.”
An eVSP can be deployed on tugs running just on batteries or with generators delivering electric power for the propellers. “With the eVSP, we make it easy for tug builders to switch to more sustainable technologies without having to compromise on performance, efficiency and safety,” he says.
Voith Turbo Marine vice president for engineering Jörg Maier says the price of high-performance batteries and power electronics components have fallen rapidly in recent years enabling more applications of electric propulsion, especially if there is limited space for drives and motors.
“Because the motor is no longer positioned outside the propeller, the drive system requires less installation space,” Mr Maier says. “The shaft train between the motor and propeller is also eliminated. This not only means less installation space, but ship designers can also dispense with a high-maintenance element.”
Other savings include a 12-30% reduction in propeller weight compared with a conventional VSP, and improved efficiency of the propulsion system. There are less energy losses resulting in higher efficiency. “With eVSP, we use a permanent-magnet synchronous motor,” says Mr Maier.
“Particularly in the partial power range, this motor is more efficient than the otherwise common asynchronous machines.” Propulsion systems are designed for a target speed or bollard pull in their rated power but tugs rarely run on nominal speeds in real operations, with engines running at partial loads most of the operational time.
Voith Turbo Marine sales application manager Patrick Denning says eVSPs can help meet the changing demands on tug propulsion from operating in harbours.
“Precise manoeuvring and safe tug operations are crucial factors for efficient cargo handling in the world’s ports,” he says. “Our eVSP enables very sensitive and extremely fast control and performance over almost the entire power range. These capabilities are crucial factors in reliable and precise ship assistance.”
Tugs using eVSPs can berth and undock ships quickly and efficiently while minimising emissions in harbours. “Less energy is needed for operations and the eVSP requires less installation space than conventional drives,” says Mr Denning. “This makes it possible to save costs when building a tug.”
He emphasises the lower maintenance costs, effort and component replacements with eVSPs, and that there are several enquiries from tug owners for these electric propellers.
The company is also working on a research project to develop remote-controlled VSPs using all-electric units powered purely by batteries, ready for unmanned tugs that could be remotely controlled from shore.
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