Drive for new Drive

Innovation and Environment

Lubricating oil costs are rising – Hansa Mare Reederei is retrofitting the engines of its 4,000 TEU vessels with the Pulse Lubricating System in the current year. The IMO issued new, stricter emission regulations and the large engine manufacturers are responding to this by conducting research into alternative technologies.
Ships’ engines have always been subject to constant modifications. Whereas the primary focus used to be on making vessels faster, low energy consumption is the decisive impetus behind the debate over new propul­sion systems today.

Conventional propulsion systems like steam turbines and diesel engines have been supplemented by gas turbines, i.e. extremely light and high-performance engines from the aviation and power station industry. However, “navalised” gas turbines require more cost-intensive gas or diesel oil as fuel.

Gas turbines, which were tried and tested as a propulsion system in shipping as of 1911, were installed in merchant vessels starting in the 1950s and then also in container vessels, the so-called container jets of an English shipping company, in the 1970s. The gas turbines did not gain acceptance because they were too expensive to operate. Economical diesel engines again took their place.

Diesel-electric engines, used in merchant shipping as of the 1920s, e.g. on reefer vessels operated by United Fruit, were more successful. Four diesel engines drove generators while an electric traction motor drove the propeller. Today all large cruise ships have diesel-electric propulsion systems since they operate with low noise and vibration, develop various power outputs for special vessel requirements and permit continuously variable speed control of the propulsion engines down to minimal levels at higher torques.

However, diesel engines have not yet reached the end of the development capability by a long shot. Currently the large diesel engine manufacturers Wärtsilä and MAN Diesel are jointly working with suppliers on diesel engines with minimal emissions and reduced fuel consumption.

What will the future bring?

At present there are not many alternative propulsion systems to replace diesel engines. Nuclear energy was not able to support itself. Propulsion by means of hydrogen and fuel cell is still in the experimental phase and is currently being tested solely in submarines. In this case the fuel cell modules are fed with liquid oxygen and hydrogen. Chemically pure water, which is used as process water, results as a waste product. Hydrogen can be generated in solar, wind and water power plants.

In future, too, ships will primarily be equipped with diesel engines or gas and steam turbine and will be driven via diesel-electric propulsion or by means of fuel cells. Depending on the environmental scenario or the resulting emission directives, these propulsion systems could be individ­ually supplemented by additional sail “drives” utilising wind energy. Initial tests in this direction have already been carried out in merchant shipping with considerable press coverage. Whether the expected ben­efits justify the expense is regarded by experts with scepticism, however.

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