the acceptable SOx levels emitted by ships as enshrined in MARPOL Annexe VI which stipulates that vessels operating with emission control areas (EMA) will have to pay fines if their SOx emissions exceed 0.1% of current levels. Mr Bjornsson said, “It is refreshing to
Torril Grimstad Osberg delivering DNV’s presentation.
would be reduced by 94%, NOx by 82% and volatile organic compounds (VOC) by 100%. Tese figures are all compared to a base vessel which has a 333m length overall, 60m beam and a loaded design draſt of 21m. Although the CO2
levels would
remain high if the ship were built as it was presented, DNV said that if all the ameliorative extras now available to retrofit onto ships to improve their efficiency were added to the Triality it would improve its efficiency, further reducing its CO2 emissions to around 50% of a standard, comparable, VLCC. Tese additional extras would include,
air lubrication, waste heat recovery and the propeller and hull appendages that improve hydrodynamic performance. Triality is already fitted with some
innovative systems that would improve its energy efficiency such as using the low temperature of the LNG fuel, which is stored under pressure in two 6750m3 tanks at -163°C, to cool the ignition
New cargo tank divisions eliminate the need for ballast, including during cargo operations.
temperature of the main engines, reducing NOx emissions and improving efficiency. Low temperature LNG can also be used for re-condensation which recovers VOCs that DNV said will then be used to power auxiliary units such as the air conditioning system and freezers or can be used as fuel along with LNG in the auxiliary boilers. According to DNV an estimated
500-600tonnes of VOCs are lost in each VLCC voyage, about 0.2% of its cargo. Re-condensation units using the low temperature of the LNG fuel preserve the VOCs to produce auxiliary power. In addition the vessel is designed to
operate without ballast in its cargo free leg, which reduces fuel consumption considerably as well as relieving the owners of the problem of having to buy and operate expensive ballast water cleaners and to train operators to work them. Te LNG fuel system similarly allows
the owner to do away with the expensive, and large SOx scrubber systems that are being developed in the light of changes to
see some new thoughts and ideas being developed”. He was particularly interested in the way that DNV had used the LNG fuel to cool the main engine and to eliminate VOCs. “It is interesting to see just what optimisation can do,” he said. For Maersk’s vice president of maritime
technology, Bo Cerup-Simonsen, the most pressing issue was the price of LNG and how that would develop when demand increased. “There is a lot of good thinking – a lot of good ideas [in the Triality design], but one of our major concerns is future gas prices,” he said, “It is only an attractive solution if the cost of the whole package, that is the total cost of ownership, remains attractive.” In anticipation of this view DNV
looked at the expected development of the price of heavy fuel oil (HFO) compared to LNG over the next 20 years as described by the US Energy Information Administration. Their findings reveal that as long as the price of HFO remains at the reference level or at the higher prices the cost savings over a 20 year period for the Triality tanker would be up to US$24 million. If the price of oil is low then the conventional tanker would prevail. Long term expectat ions are,
however, that the price of mining oil along with increased demand and the costs associated with pollution from conventionally designed vessels will make their operation are far more expensive than the DNV equivalent. If owners believe that the associated
costs of operating the Triality will improve their profitability by reducing their costs then the probability that further development on the Triality will take place are high. And at the moment at least one major owner is making all the right noises. NA
Scavenger air cooling may provide an energy efficiency gain of up to 3%.
The Naval Architect January 2011 43
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