Feature 1 | DANISH MARINE INDUSTRIES Index for energy efficient design
Proposal for an energy efficient design index for ships has deep roots at the Technical University of Denmark.
Maritime Organization Energy Efficiency Design Index (EEDI) of vessels presented at the IMO’s Working Group on Greenhouse Gas Emissions (GHG) from Ships in March. Hans Otto Holmegaard Kristensen, senior
O
researcher at the Technical University of Denmark (DTU), explained that the index being planned would mandate a maximum CO2
emission per tonne deadweight per
nautical mile for new ships. According to Mr Kristensen, it would be more correct to call the index “maximum allowable CO2
emissions
per transport unit”, but in the discussions at IMO the index has got the official name “Energy Efficiency Design Index”. Mr Kristensen has, in fact, been working on
an energy efficiency index for ships for nearly 10 years. “I just happened to be working on this important project much before others,” he told Te Naval Architect. His program calculates emissions from different ship types, using a set of input values in a generic computer model for each, where the power can be predicted based on the ship’s main dimensions, determined from statistical analysis of ship data drawn from the Lloyd’s Register-Fairplay ship database. Not only can CO2
emissions be estimated, but also
SOx, NOx and particulates. Furthermore, the program can estimate the influence of various ship parameters, such as changes in the main dimensions, changing the service speed, engine configuration and propulsion layout. Mr Kristensen has been able to work in
close cooperation with different Danish shipowners in order to back-up the theoretical results with real data. Due to the growth in size of containerships since 2000, the model is now being upgraded. During this upgrading the influence of new exhaust gas cleaning technologies will also be taken into account, to be able to judge the influence of selected technology on the total emission picture at the planning stage. As far as discussions at IMO are concerned,
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Mr Kristensen said: “Te goal is to be able to have the theoretical framework ready for the new Energy Efficiency Design Index before the Climate Summit in Copenhagen at the end of 2009 for establishing permitted CO2 emission levels for different ships. I personally do not think this will be implemented before two or three years, but we are working hard on it, and the goal is to reach an agreement on the matter at the next MEPC 59 meeting this summer. “Indirectly, the IMO index will slow
down the speeds of vessels in the future,” Mr Kristensen noted. Te solution is not that simple though, and it is likely that such an index, in its current form, will be problematic for the ferry industry, for example. If the index for a certain ferry required a speed giving a turnaround time of 25 hours instead of 24 hours, for example, this could destroy the timetable and thereby the economy for that particular route because a regular 24 hour sailing cycle could not be obtained. Another problem with the current index is the divergence it gives for Panamax-size vessels as compared to post-Panamax vessels (see graphs on next page). Te very simplified version of the Energy
Efficiency Design Index proposal is;
ne of the key elements of the “Green Ship of the Future” has seen a proposal for an International;
Influence of speed on the proposal for IMO’s Energy Efficiency Design Index.
• CF
where; = a non-dimensional conversion factor
between fuel consumption measured in g and CO2
• SFC = specific fuel oil consumption for the engine in g per kW per hour.
on carbon content (CF 3.1).
• Vref = the ship speed, measured in nautical
• Capacity = the deadweight in tonnes for dry container ships, bulk carriers, tankers,
miles per hour (knots), on deep water in the maximum design load condition (scantling condition) at 75% of the maximum output of the engine(s) and assuming the weather is calm with no wind and no waves. Te maximum design load condition shall be defined by the deepest draught with its associated trim, at which the ship is allowed to operate.
gas tankers, ships, and general cargo ships. For passenger ships capacity is defined as the ships gross tonnage, GT, as such ships are more ‘volume carriers’ instead of
The Naval Architect April 2009
emission also measured in g based = approximately
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