Trans RINA, Vol 152, Part A4, Intl J Maritime Eng, Oct-Dec 2010


underpowered ships which, de-rated


thanks to the efforts of


Greece, has been somewhat alleviated by agreeing to use an engine’s


MCR in the calculation.


Furthermore, the attention drawn to the issue has resulted in efforts by IACS and others to investigate a “minimum required power” to keep a safe speed in rough weather. Perhaps an even more serious concern relating to this paper is EEDI’s push for the lightest ships possible in order to increase deadweight. On that front too, Greece achieved majority IMO agreement to at least exclude from the calculation the extra steel weight resulting from voluntary structural enhancements which increase safety. The debate on EEDI is far from over and we hope to have the chance to discuss the various facets of the problem in another occasion.


Coming now to Christian Breinholt’s comments, his main argument is that we have not taken into account possible technological advances that may happen during the 20 years of ship A and the 30 years of ship B’s lifetimes, or the combined 60 year super-cycle of both. He also argues that such technological advances will weigh in favour of ship A, as these advances will be significant during a period of 60 years. We have already acknowledged in the paper that we do not consider differences in technology as these are second-order effects. We think it is self evident that the 60 year super- cycle is only an accounting tool to bring two ships of unequal life cycles to a common denominator as regards emissions on a yearly basis. Nobody suggests that one will operate 3 ships of type A for 20+20+20 years in a row, or two ships of type B for 30+30 years in a row.


But even if we want to consider technological advances, the only technological difference between the two ship types will manifest itself during the 10 year time frame from the scrapping of ship A to the scrapping of ship B, is that a ship built to replace the scrapped ship A can perhaps employ some technological improvements which the existing ship B cannot, in the remaining 10 years of its life. But this is so only if these improvements cannot be retrofitted. Unless


one expects miracles in


hydrodynamic developments or vastly more efficient engines within any future 10 year interval (we do not), we think that most technological advances will be retro- fitted (fins/ ducts/props/paints, etc). Thus they could be installed on any existing ship.


For technological developments that cannot be


retrofitted, say, a more efficient engine that the ship A replacement will have at year 20 while ship B will continue to use the same old engine during years 21-30, a similar argument exists with the replacement of ship B at year 30. The ship B replacement


will have a more


efficient engine than the one of the ship replacing ship A for the period between year 31 and 40, and so on.


Furthermore, the argument seems to be a circular one. According to this, a 10 year design life ship will be even better than a 20 year design ship, and so on. However


REFERENCES


18. Houghton, J.T.; Meira Filho, L.G.; Callander, B.A.; Harris, N.; Kattenberg, A.; Maskell, K., eds. (1996). Climate Change 1995.


Change. Published for the Intergovernmental Panel on Climate Change. New York: University Press.


The Science of Climate Cambridge


19. Shipping Emissions: From Cooling to Warming of Climate-and Reducing Impacts on Health by Jan


new IMO SOLAS regulations (Goal Based Standards) require that ships henceforth are designed with a 25 year design life. So one cannot advocate ever shorter design lives. The issue we tackle here is building ships which on paper comply with the 25 year design life requirement (using IACS CSR for their construction) but actually cannot reach that age without excessive, costly and environmentally unfriendly repairs. With some rather minor structural upgrades, as specified in our paper, these ships not only reach their design life with normal maintenance and repairs but can easily exceed it.


Regarding the arguments on CO2 emissions during


building, repairing, recycling etc., although we agree that these will be reduced for all ships in the future, again we need to point out that in comparing the two ship types, the only relevant differences will be those of any 10 year differential period. But some of these activities will work in favour of the longer life ship B (e.g. a ship scrapped at year 20 will emit more CO2 than a ship scrapped 10 years later, due to possible technological improvements in scrapping).


With regard to the steel replacement rates used in calculations, these are real averages for steel repairs of this type of ships (bulk carriers) in China. Repairs at other countries may be slightly faster but much more expensive (shortening the economic life of ship further). Nevertheless, we do state that this rate could be as much as 12 tons/day in some good yards resulting in a best case scenario of 83 days downtime for the last 3 years. The results would not change in substance. Whether an owner will consider such repairs totally depends on the then economic environment. We should also note that the amount of calculated steel to be replaced (based on IACS CSR corrosion margins) has not been challenged to date. It is reminded these calculations have been submitted to IMO and Japan and IACS have commented on other issues of the (original) paper but not on the true wear (corrosion) rates of steel structures used in our paper.


This is because we used actual repair data in conjunction with past classification society studies (fully disclosed and substantiated) which, unfortunately, IACS CSR chose to ignore in setting the rule corrosion margins.


Last but not least, we have no specific response to Sun Jun’s comments, for which we thank him.


© 2010: The Royal Institution of Naval Architects


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