Dr Chris Craddock
Technical Advisory & Ship Performance Manager
In the second of our two-part series looking at decarbonisation and its impact on the global fleet, Dr Chris Craddock – Technical Advisory & Ship Performance Manager at LR – discusses the path towards compliance and the need for a context-sensitive approach to regulations like EEXI and operational carbon intensity indicators (CIIs).
The Energy Efficiency Existing Ship Index (EEXI) will be adopted in June this year. When it comes into force in late 2022, all ships will need to meet strict new limitations on the amount of CO2 emitted per capacity tonne mile. They will need to do so before the date of their next survey for issuing the International Air Pollution Prevention Certificate (IAPCC), in line with IMO-provided requirements for their size and type.
This doesn’t leave much time to prepare should a vessel’s survey date fall within days of the compliance deadline. Those with later scheduled surveys will have a little more time, of course.
EEXI isn’t the only decarbonisation measure on the horizon, however. Operational Carbon Intensity Indicators (CIIs) will soon put even further scrutiny on vessels of 5,000 gross tonnage or over. Ships in this category will be given a rating from A to E (where A is best), based on a calculation of AER =
for the majority, and cgDIST=
for cruise ships, vehicle carriers, and ROPAX vessels. The former uses deadweight tonnage in the calculation, the latter gross tonnage.
While the new EEXI regulation presents an initial target to aim for, the introduction of CII ratings may require more action. It is advisable, therefore, that technical managers and owners take the opportunity presented by their EEXI analysis today to take a rather more strategic approach to decarbonisation for tomorrow.
Overridable power limitation (OPL) – including both engine power limitation (EPL) and shaft power limitation (ShaPoLi) – offers an immediate compliance option for EEXI. It is relatively non-invasive, has a low capital cost, and is applicable to most ship types. At the same time, however, its ability to impact subsequent CII ratings will be limited due to existing operational speeds and average main engine loads.
Put simply, while OPL may offer a ticket to the decarbonisation game, it is unlikely to be enough to keep you in it for long. Therefore, should adaptions or changes to vessel operations be required to meet the incoming EEXI requirement, it may make commercial sense to also consider steps to address operational carbon intensity reduction simultaneously. That way the vessel can avoid making further adaptions in the relatively near future.
For vessels that will fail to meet the required EEXI and where options need to be assessed for compliance, the approach employed needs to also consider how the options will impact the CII rating of the vessel and maintain ratings of A to C.
At LR, we do this by utilising the guidelines from the Marine Environment Protection Committee. This allows us to explore:
- The percentage of engine or shaft power limitation that would be required to achieve compliance.
- The extent to which the vessel’s maximum speed could be reduced if EPL was employed.
- The minimum power of any ship subject to MARPOL Annex VI Regulation 21 for which a non-overridable power limitation or de-rating will be used to achieve EEXI compliance.
- The potential application of innovative Energy Efficiency Technologies (EET) as a practical alternative to EPL.
- The expected performance improvements and costs of EET retrofitting (including technologies such as pre-ducts/stators, propeller boss cap fins, wind assist technology, advanced hull coatings and air lubrication).
A bespoke approach like this is key because the energy efficiency of every ship can vary greatly depending on its class, size, age, and the extent to which it has been modified since it was delivered.
Context is key, particularly in the case of EPL – something that can be problematic for two ship types in particular: ROPAX and steam turbine-powered gas ships.
ROPAX vessels have hotel loads (lighting, air conditioning, galleys, and more) and strict route timings to contend with. Many owners will naturally question whether EPL is a suitable method of decarbonisation.
While EPL can still work for ROPAX ships, the alternative of hydrodynamic retrofits such as bulbous bows and aft appendage modifications can have a considerable positive impact on operational performance.
In the case of steam turbine-powered gas carriers, specifically older vessels with no reliquification systems, their Liquefied Natural Gas (LNG) cargo boils during a journey. The resultant boil-off needs to be burnt through the engines. But with EPL levels as much as 50% to 60% required for compliance, it may prove impossible to consume the natural boil-off gas. The IMO has already acknowledged this and intends to make allowances for these vessels to prevent harmful methane emissions to the environment, and ensure the safety of the vessel and her crew.
The full ramifications of EEXI and CIIs will continue to become clear as implementation dates draw closer. In the meantime, flexibility – and the ability to think about long-term benefits rather than just short-term gains – will be key.
There is no “best way” to improve a ship’s CII rating or EEXI compliance – only the one that delivers the greatest decarbonisation impact at an acceptable return on investment.