New Aframax design concept from GL

29 Sep 2011
GL's Ronnie Westerman: 16% improvement in EEDI base scores if owners opt for BEST-plus practices

GL's Ronnie Westerman: 16% improvement in EEDI base scores if owners opt for BEST-plus practices

A new conceptual design of Aframax tanker launched recently by Germanischer Lloyd (GL) shows the extent of efficiency improvements that are possible, writes Paul Bartlett.

The German class society’s ‘BEST-plus’ design scored a 16% improvement on the assumed baseline Energy Efficiency Design Index (EEDI) for tankers in this category.

The new Aframax concept is geared to US Gulf trades where the new US-Canada ECA is due to enter force in August 2012. Another regional ECA covering coastal waters off Mexico is likely to be introduced soon, say experts. The new design aims to raise fuel efficiency, vessel productivity and safety as compared with existing vessels in the size range.

Working with the National Technical University of Athens, the study assessed and systematically varied a wide range of parameters in the drawing up of no fewer than 2,500 design variants. The variables included power, speed, ship dimensional constraints, cargo capacity, hull structural mass, cargo oil tank and ballast tank layout, double bottom height, double hull width and therefore the risk of pollution as measured by the oil outflow index. The possibility of using LNG as a fuel for the main engine was also considered.

“Oil tankers, with their relatively large deck area, offer sufficient space for the installation of the required gas tanks and for the gas preparation room,” comments GL. “The design concept calculates 2,000 m3 of LNG for two round trips. Using LNG as ship fuel could reduce SOx emissions by 90% and CO2 emissions by 20%.”

According to Ronnie Westerman, a senior surveyor at GL and business development manager for Scandinavia, the class society identified the Aframax sector as likely to require fleet replacement before other size ranges. There are fewer Aframax units on order as a percentage of that fleet as compared with other sectors, he said, and this is borne out by industry statistics which show about 120 Aframaxes on order and an existing fleet in which almost 170 units are more than 15 years old.

GL believes that tanker design has really not moved forward much since double hulls were introduced. Shipyard productivity may have advanced, Westerman points out, but little attention has been paid to the life-cycle performance of ships and overall transport costs. Now though, as the IMO’s EEDI has a growing impact on ship design, fuel efficiency is coming under close scrutiny, especially for sectors of the fleet – such as tankers, container ships and bulk carriers – which contribute most to global shipping’s CO2 emissions than most others.

According to GL figures, for example, tankers are amongst the most energy-efficient vessels today but they still kicked out about 115 million tonnes of CO2 in 2009, an 8% increase on the figure two years before. Tanker emissions in 2009 accounted for about 12% of global shipping’s total.

The BEST-plus design concept, which also considered the possible use of LNG as a fuel, was significantly more efficient than existing vessels in various ways. Apart from being safer, faster and with better cargo-handling equipment – enabling one additional round trip per year – the design is more economical. Reduced fuel consumption, reduced emissions and improved productivity result in a lower overall cost of transport., down by 7%, Westerman says.

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