All-electric ship. Propulsion, electrical distribution and power production

Applications of electricity to electric propulsion are almost as old as industrial electricity, and have always existed for certain specific applications. Let's take just one example: in the 1930s, the prestigious liner Normandie was equipped with an electric propulsion system comprising 4 synchronous motors, each driving a 40,000-horsepower fixed-pitch propeller.

Until recently, however, the vast majority of ships used propulsion units consisting of turbines and/or diesel engines coupled to a propeller shaft. In addition, several autonomous power generation systems were available for servitude, combat systems (military vessels) and hull auxiliaries.

In the "all-electric" ship (i.e., with integrated electric propulsion), the production, distribution and overall use of energy for the entire vessel are taken into account. Distribution between the main users is carried out via power cable networks.

Nowadays, however, a new concept of vessels known as hybrids, combining a purely electrical system with thermal propulsion equipment, is gaining ground, driven by new forms of clean energy production and decisive technical and economic advantages in terms of installation and operational performance.

An electric ship comprises two main components: power generation and propulsion.

The power plant is similar to the one used on all ships to supply the on-board network, but with much greater installed power. It supplies all on-board users, including one or more propulsion units.

Propulsion equipment generally comprises a variable-speed electric motor and a converter (there are a few cases of electric propulsion using a fixed-speed motor driving a controllable-blade propeller).

Generally speaking, the aims of the electric vessel are :

• Flexibility in maneuvering: electric propulsion allows almost instantaneous reversal of direction and full-power reversing, resulting in very short stopping distances. It offers stability of motion at very low speeds, and great maneuvering precision;

• improved overall nautical efficiency, achieved by splitting up the power plant so that the thermal units can operate at a load rate corresponding to optimum efficiency;

• reliability and a reduction in logistics and maintenance. These improvements are achieved by eliminating certain mechanical complexities (propellers with controllable blades) and the robustness of electrical machines with no wearing parts. Redundancy, a powerful factor in improving reliability, is present in power generation, easily reconfigurable electrical networks and multi-wound electric propulsion...