The future of maritime propulsion

Kongsberg Maritime continues to lead the way with innovative propulsion solutionsthat meet the demands of modern naval vessels. With growing demand for electricpropulsion, one such groundbreaking development is the Elegance electric podpropulsor, designed to offer unparalleled efficiency, manoeuvrability, and environmental benefits.

Per Nahnfeldt, Kongsberg Maritime’s Product Manager for Pods shares insights into the development and advantages of this cutting-edge technology.

A natural evolution

Kongsberg Maritime has a long-standing reputation for excellence in thruster technology, particularly in the 1-7MW range. Recognising the growing trend towards electrification, the company drew on its extensive earlier experience with the larger Mermaid pods (with cruise, offshore and naval references) to create a product that fits perfectly within this power range. 

“We saw a strong electrification trend coming and knew we had the expertise to develop a product that would meet future demands. While the larger Mermaid pod is no longer produced, we gained so much experience with this technology, which has helped us to create ELegance, a propulsor that’s focussed on future demands,” says Per Nahnfeldt.

Mermaid is installed on the French and Egyptian Navies’ Mistral class amphibious assault ships. “We have many years of operating experience of Mermaids on these five ships, and the performance has exceeded expectations. With no moving parts, other than the rotor, there is little need for maintenance and these propulsors just run and run. Position keeping is critical for helicopter operations, and azimuthing pods, combine power and responsiveness.”

The ELegance pod – the El in the name relating to electric - was developed to address some earlier technical challenges associated with mechanical thrusters, such as complex gear arrangements. Unlike traditional thrusters, the ELegance pod features a direct connection between the motor and propeller, eliminating the need for gears and therefore reducing drive train losses. 

Per Nahnfeldt adds: “For the naval market the diving support vessel for Italy is aprime example of where manoeuvrability, station-keeping and flexibility are crucial. Low noise is also a key requirement, and we’ve designed the pod and motor to be exceptionally quiet, which is ideal for diving and submarine rescue operations.”

Three key factors define the performance of the Elegance pod: low noise, high efficiency, and excellent manoeuvrability. The standard configuration typically involves two pods at the aft, providing superior manoeuvrability and eliminating the need for tunnel thrusters in the stern. This simplifies vessel design and enhances overall performance. The compact design of the Elegance pods allows for greater flexibility in vessel layout, freeing up valuable space for other critical systems and equipment. This is particularly beneficial for naval vessels, where space optimisationis often a key consideration.

Kongsberg Maritime has also explored hybrid configurations for Elegance, combininga single shaft line propeller in the centre, with wing pods to each side, to offer the best of both worlds. “This setup is particularly suited to naval and cruise vessels, providing high power, excellent manoeuvrability with a compact installation,” adds Nahnfeldt.

Advanced Features and Environmental Benefits

The Elegance pod boasts several advanced features that set it apart from traditionalpropulsion systems. It has a very low oil content and environmentally friendly sealswith an air space between the water and oil, which virtually eliminates the risk of oilspillage.

The pulling option features twin fins, which improve steering and cavitation performance, recovering losses from rotational flow more effectively than other solutions.In-house capabilities at the Kongsberg Hydrodynamic Research Centre (HRC), which include test tunnels and CFD (Computational Fluid Dynamics) capability, allow for customer involvement in product optimisation. The pods are made from castings, allowing for optimal hydrodynamic shaping.“The shaping of the unit is close to perfection hydrodynamically, and in combination with being fully electric, we settled on naming the units Elegance.”

Per Nahnfeldtsays. “The immediate access to our research centre has been key in optimising theperformance of these pods.”The Elegance pods are designed for easy installation and servicing, with underwater replaceability and the ability to be delivered later in the build process, benefiting both shipyards and owners.

The pod uses a Permanent Magnet (PM) electric motor, known for its robustness, compactness, and high efficiency. This motor, combined with a fixed-pitch propeller made of bronze or stainless steel, ensures optimal hydrodynamic performance.