Focus on Fuel

Trends at the shipbuilding fair SMM 2008

At the end of September, almost 52,000 visitors from the industry were enlightened on the latest developments in shipbuilding at the "Shipbuilding, Machinery & Marine Technology" fair (SMM) in Hamburg. And a total of 1,965 exhibitors from 56 nations showed that increased efficiency and environmental protection are not a contradiction.

"A lot of things have gained a new importance," Carsten Lehfeld, who visited the SMM for Hanseatic Lloyd, summed up the frequently changing viewpoint. Many methods are not new, but from present day perspectives and with adapted technology they are mostly worth far more than just a passing inquisitive glance.

The rise in bunker prices (at mid-year the oil price had reached an alltime high of almost 150 US Dollars a barrel) has adjusted the focus. To reduce fuel consumption is the overriding target. To this end a great deal of work is being done on the design of new ships, and further optimisation development of the main engines is one of the main aims by the manufacturers. More work on usable energy from exhaust gases is also on going.

Hull optimisation

In new ships, engineers are looking for the lowest possible resistance of the hull in the water. Recent developments in software and hardware, in particular fast computers, today make it possible with corresponding programmes to calculate hundreds of variant forms for the hull in a short time.

The boundary conditions such as for example length, beam and deadweight tonnage are fixed. Individual factors are changed and optimised by the software in repeated calculations until a sensible result has been obtained. "The user must nevertheless know what he is doing," Carsten Lehfeld underlines the importance of the experience of the engineers despite huge advantages of the heavily automated processes.

There have been approaches to the problems from this direction for a long time, but in the meantime the software has been improved and meets market requirements. "Each kilowatt that I don't have to install saves space, fuel and costs and automatically reduces pollutant emissions," states Project Manager Lehfeld.

Variable turbine blades

To go some way towards compensating bunker prices, cruising speeds have been lowered on many routes. Although reducing speeds saves some fuel, the main engines are in fact optimised to a certain operating point tailored to the original cruising speed. "At a reduced cruising speed the engine no longer works at the operating point," explains Lehfeld. If you improve the boundary conditions again, further fuel savings are possible. For this, MAN has for example developed a turbocharger with variable turbine blades ("VTA"). The angle of incidence of these can be changed in such a way that the combustion air blown into the engine is adjusted to the injected fuel - so that even at lower rotation speeds optimum conditions again exist.

Recovering energy from the exhaust gas

For decades work has been carried out on improving the efficiency of big diesel engines on ships. This has meanwhile reached some 50 %. And yet further improvements are decreasing in size from step to step.

Looking at this from the other side means that 50 % of the energy content of heavy oil is still being lost largely unused. About half of this is directly blown out through the funnel. One approach is to use the heat from the exhaust gas ("waste heat recovery"). A few years ago, concepts for this were already developed for recovering energy from the exhaust gas via steam and exhaust gas turbines and thus to be able to switch off for example auxiliary diesels while at sea. "Two years ago hardly anyone was interested in the papers on this," says Carsten Lehfeld about the new point of view. It may be possible to achieve a significant improvement in overall efficiency and fuel savings in the region of 10 %. However, when the costs - which go into the millions - can be recouped through lower fuel consumption naturally depends on the price of oil. At 150 US Dollars a barrel, some investments in connection with new ships could already pay for themselves in short order.

 

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