Feature 1 | GREEN SHIP TECHNOLOGY Triality tanker design interests owner
DNV’s new tanker design presented to the public in early December in London is a “refreshing” concept said Maersk. Te design incorporates a new hull geometry with existing technology that could reduce CO2
emissions substantially. I
n designing the new Triality tanker the DNV team set out to determine what would be the over-riding
needs for the future and they concluded, very quickly, that the environmental footprint of the ship was of paramount importance. Solutions for reducing emissions
needed to be simple, there was to be “no complexity to the ship,” explained Torrill Grimstad Osberg, Triality project manager. “We were working with a knife at our throats,” she laughed describing the short time scale that was afforded the team to come up with a new concept vessel. In fact the DNV team started work in mid-August and had completed their work in just three months. With these parameters and the short
time scale in mind it was a relatively simple step to decide that the fuel the new ship should use would have to be liquefied natural gas (LNG). It was the only fuel available that would reduce all the key emissions, substantially, including CO2
by
34%, SOx and particulate matter by 94% and NOx by 82% for the Triality vessel as a whole. That meant more time could be
afforded to the design of the hull which was, said Ms Grimstad Osberg, the most challenging element of the vessel design. Te rest of the ship has been fitted with existing technology.” Maersk’s manager of the innovations
department Gunnyar Bjornsson, who is a naval architect and master mariner and specialises in the use of LNG as a fuel, was impressed by the hull design and the ballast free elements of the concept vessel. “It’s a completely different geometry, on an ordinary tanker the cross section is rectangular, with the Triality it is a V-shape, but with a 10m or so flat bottom”. However, with the ship operating at a
draſt of around 8m aſt and 6m at the bow when operating empty there could be
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The 300,000dwt tanker has a 70m beam giving it extra stability in its, ballast free, empty operational mode.
issues with stability, agreed Mr Bjornsson, who had also seen DNV’s presentation on the Triality vessel. “I couldn’t tell about stability without model tests and further calculations, but there would definitely be an issue there, particularly when manoeuvring and in a beam sea.” Tough he did not consider these design difficulties insurmountable. In fact a mitigating factor for the vessel
would be its 70m beam, which is 10m wider than the standard VLCC. Te vessel has also been made longer at 361m and has a loaded draſt of 21.6m. Loading of
Two large deck houses contain the cargo tanks, each of 6750m3 range of 25,000nm.
giving an operational
the vessel, which has its tanks arranged five across, would have to be completed by filling all the centre tanks simultaneously to prevent bending moments. However, the shallow draſt of the vessel
when operating empty did create another problem with the propeller. It meant that the team opted for two MAN ME-GI engines with direct drives for two 7m overlapping propellers rather than the standard single 9-10m propeller which would have been too large for the shallow draſt vessel. Te two propellers overlap by 1m and
give “extra efficiency”, said Ms Grimstad Osberg and the cost of two smaller MAN engines compared to a single larger engine “was not great”, she added. A tougher nut to crack, however, has been the dilemma over CO2
emissions
and in this case DNV opted for LNG as the best possible existing technology. Although Ms Grimstad Osberg conceded that LNG is not the only answer to the maritime sector’s emissions conundrum she said that the fuel would reduce CO2 by around 34% while particulates and SOx
The Naval Architect January 2011
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