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The annual Hellenic Technical Committee Meeting of Germanischer Lloyd (GL) discussed the technical implications and commercial benefits of using gas as ship fuel.

According to Torsten Schramm, Chief Operating Officer of Germanischer Lloyd, the global availability and low emissions make gas a more favourable source of energy for the main propulsion in shipping.

"Natural gas is the cleanest of all fossil fuels. It already provides about a quarter of the total global energy. Furthermore, the combustion of natural gas results in lower levels of emissions. Given the fuel price development and lower emission limits, LNG is going to be an attractive alternative to distillate fuel in Emission Controlled Areas (ECA)," GL said in a statement.

Professor Apostolos Papanikolaou, Director of the Ship Design Laboratory, National Technical University of Athens (NTUA), and Dr. Pierre Sames, Senior Vice President Strategic Research and Development at GL, discussed the creation of novel ship design concepts with advanced optimization environment.

As an example of this approach, Dr. Sames, presented an advanced new Aframax crude oil tanker design concept which aims to reflect the ongoing trend towards greener shipping by improving energy efficiency, reducing CO2 emissions per unit transport, and offering a smart solution by cutting fuel costs due to the optimized hull form and increasing cargo capacity. Furthermore, it addresses the need for safer shipping by reducing the oil outflow in case of an accident.

"It offers a best-in-class cargo capacity with unrivalled speed performance while the main particulars of the vessel are comparable with those of similar-sized Aframax tankers," GL said.

The Aframax tanker design approach used an advanced optimization environment by integrating software tools to predict required propulsion power, stability, oil outflow index, cargo capacity and hull structural scantlings according to IACS Common Structural Rules. The optimization targeted speed at three different drafts, a cargo capacity taking due account of cargo volume and mass, hull structural mass, hull cargo, oil tank, ballast tank layout as well as double hull width and double bottom height, which determine the oil outflow in accidents, are the main features of this Aframax tanker design.

Related design parameters were systematically varied and approximately 2,500 design variants were generated and assessed. The resulting optimized hull form facilitates a speed of 15.6 knots at design draft. The speed requirements of ship operators were considered with regard to the upcoming Energy Efficiency Design Index (EEDI) requirement to ensure superior competitiveness of the vessel.

"With this high speed and large cargo capacity, the vessel easily meets future EEDI requirements. The attained EEDI value is merely 83 percent of the latest published reference-line value for this ship size. This means the vessel would be in compliance with EEDI regulations even if the first reduction to the required EEDI has already begun," GL said.

According to GL, estimates indicate that this will take place at the earliest on January 1 2015. Although a vessel contracted before EEDI has entered into force does not formally need to comply, competitive vessels entering the market, e.g., in 2017, will be more energy-efficient and therefore, more likely to attract cargo.

For safety reasons and to reduce oil outflow in accidents, the double hull side width was eventually set to 2.65m. In addition, to further reduce cargo tank penetration in grounding events, the tank inner bottom of the cargo oil tank 1 was raised. To ensure structural continuity, an inclined inner bottom is proposed between two frames.

The design study is based on a project by GL and the National Technical University of Athens (NTUA). Feedback from shipyards and oil tanker operators initiated the continuation of the project work, which resulted in the novel design concept called BEST plus. BEST plus aims to enhance the attractiveness of the initial design concept by integrating hydrodynamic optimization of the hull form and state of the art features to improve energy efficiency on board.