The study shows very large variations in design efficiency between the best and worst years for individual ship types. For instance, the best-designed bulkers built around 1990 were some 14% better than those built today. For tankers the best designs for new builds around 1988 were 10% better than those built today.

The difference for container ships was far greater. Those built in 1985 were about 25% better than those built in 2013. However, this does not reflect the large reductions in CO2/TEU/mile for containers due to increasing ship size and improving engine efficiency over this period.

Are IMO’s design efficiency standards fit for purpose?
There is a growing interest in the fuel efficiency of ships because of rising oil prices, climate change, and energy security issues. From 2013, new ships need to meet the IMO’s Energy Efficiency Design Index (EEDI) targets, which become more stringent over time. Currently, the IMO is reviewing these targets and one of the main questions being addressed is their effectiveness and stringency.

Factors affecting ship efficiency
Depending on the ship type or size, this study shows that ship design efficiency improved in the decade of the 1980s by 22% to 28%. This trend seems to have been purely market driven, principally by a combination of sharply increasing oil prices and constant or low freight rates. Looking more deeply at the factors that contributed to improvements in the 1980s shows that in some, but not all cases, efficiency improvements were brought about by reductions in design speed.

In other cases, the size of the ships has increased. However, these two developments cannot fully explain the improvements. In many cases, the evidence points to improvements in hull design and propulsion efficiency as having contributed significantly to efficiency improvements. Likewise, the deterioration after the 1990s appears to be due, at least in part, to designs in which cargo capacity or capital costs were given more importance than fuel efficiency. This is a potentially important finding given current lower oil prices.

More stringent design efficiency standards within reach
The relevance of this study for the review of the IMO’s design efficiency standards is that it suggests that ships can improve their design efficiency by 5% to 15% on average just by going back to 1990s designs. Analysis of the design efficiency of ships that have entered the fleet since 2009 would appear to show this has in fact been happening.

And since hull, rudder and propeller and engine designs have likely improved in the past 25 years because of technological progress, such as the development of computational fluid dynamics, much larger efficiency improvements are probably within reach. Lower design speeds could improve design efficiencies even more where appropriate.
(Source : European Federation for Transport and Environment, Seas At Risk)