Declining efficiency or flawed study?

A study commissioned by environmentalist lobby group Transport & Environment and carried out by CE Delft is stated to show that the average design efficiency of new bulk carriers, oil tankers and gas carriers was worsened last year compared to 2015. Green groups are citing the report as a need for the IMO to tighten the EEDI requirements for future vessels.

The analysis shows that 14% of bulk carriers, 52% of containerships, 23% of tankers, 21% of gas carriers and 55% of general cargo ships that entered the fleet in 2016 already met the 2025 design efficiency standard. But that improvement was not continued in 2016.

However, the study might be considered to be flawed in that it does not use the actual EEDI of the vessels but instead calculates what it may possibly be using the formula that the IMO used to establish the reference line for EEDI purposes in 2008.

To calculate the reference line, an estimated index value for each ship contained in the set of ships per ship type built between 1999 and 2009 was calculated using a simplified version of the EEDI formula that took into account main and auxiliary engine power, ships deadweight and speed. The details can be found in IMO document Resolution MEPC.231(65).

Importantly the formula did not make any correction factors for ice class, voluntary structural enhancement, etc. or for innovative mechanical energy efficiency technology, shaft motors and other innovative energy efficient technologies. (points 6 and 7 of the Resolution formula explanation).

When calculating the reference line in 2008, the IMO had no knowledge of the ships’ details other than that contained in the HIS Fairplay database. It certainly did not know what if any efficiency improvements in the way of hull energy saving devices were fitted, or if the propulsion arrangements and engines had been properly matched. Which is why these items were excluded from the formula used to calculate the reference line.

In using the same basic information for ships delivered after EEDI and attempting to calculate an estimated Energy Efficiency Design Index (eEEDI), the report from CE Delft could be considered flawed. It makes some qualified statements such as this appearing on P10 of the report:

Table 5 shows the Estimated EEDI for bulk carriers (eEEDI), defined as 90% of the EIV value. The results suggest that not all ships that have entered the fleet in 2016 have an attained EEDI that is below the reference line, as they are required to have unless they have obtained a waiver.

It is entirely possible that some ships have been given waivers – although this would be the flag state’s decision – but equally it is more likely that the ships in question are fitted with ESDs of some type. Becker’s Mewis Duct of which several thousand have been fitted is claimed to improve efficiency by between 6% & 8% on bulk carriers and tankers.

Nor does take into account when orders for the ships built in 2016 were placed, whether the ships delivered in 2016 were series ships of less efficient design than one-offs built in 2015 or if they were earlier designs with delivery dates delayed at owners’ request due to market conditions.

In its conclusion, the report points out that however, that the changes in the average and mean design efficiency are small compared to the standard deviation, so that it is not possible to draw firm statistical conclusions. That point alone should mean that the report does not actually show in decline in efficiency at all.