PORTFOLIO | COVER STORY
WATER RESISTANCE. The computer-generated design optimizes the hydrodynamic properties to conserve fuel.
SELECTION. Many designs are better than the refer- ence design – but only one variant will be accepted.
Designing for Energy Efficiency
which tells us how much power a ship is consuming on a certain leg,” says Höppner.
Poring Over the On-board Systems A frequent cause of energy wasted is the way the equipment is run. In addition, many systems operate at full load permanently, without even offering the option of reducing their energy use. In a two-day workshop, GL consultants will work together with a ship’s crew, going over every single system on board to identify the oper- ating routines. In many cases, the main engine is over-dimensioned. Coolant pumps are frequently poorly adapted, running constantly at full capacity. By installing a frequency converter, 70 per cent of the energy consumed by these pumps could be saved. “But most ships do not have a frequency converter,” says Höppner. “And what is more, many ships with a design speed of 25 knots are run at no more than 18 knots. Since their bulbous bows are not op- timized for that speed range, the generated wave patterns cause the water resistance to increase.” As a result, fuel costs rise.
Dr Karsten Hochkirch, one of the founders of Friendship Systems, heads the Department of Hydrodynamics at FutureShip.
“We usually begin our calculations by generating a reference design – a plan for a ship that needs to be optimized.” Using the parametric modelling tool Friendship-Framework and the custom- developed flow simulation software FS-Flow, the experts put 500 processors to work to calculate more than 20,000 hull variants within as little as two days. The resulting diagrams look like mod- ern art - seemingly random patterns of red colour sprayed onto a sheet of paper. But each single dot represents one particular hull variant. The two axes of the graph represent water resistance and load carrying capacity, respectively; the “100” mark on each axis corresponds to the reference design. As many as one quarter of the computer-generated designs beat the reference design on both criteria.
A Gigantic Design Space The FutureShip experts then begin to add other criteria, such as an optimized centre of buoyancy or higher stability. In a rigorous selection process, they extract a short list of about five designs to present to the customer. “It is usually not until this stage that the owner determines where he wants to go,” says Hochkirch. The next step is a detail analysis. “The design space is huge,” Hochkirch explains. The search for the right solution resembles a hike across unknown terrain. At the end of the analysis there will be one single variant – a “peak”. This is the only design that will be tested physically in a ship model basin. “In most cases our design turns out to be four per cent more efficient,” Hochkirch reports. “Once we actually achieved as much as 20 per cent.” But for a Panamax containership sailing 260 days per year, 4 per cent of fuel conserved translates into savings of 1470 tonnes of HFO annually. ■ HS
For further information: Volker Höppner, Managing Director FutureShip, Phone: +49 40 36149-3244, E-Mail: firstname.lastname@example.org
THE TIP. The shape of the bulbous bow must match the typical cruis- ing speed of the vessel.