REQUIRED AND ATTAINED EEDI

REQUIRED EEDI

The Required EEDI is the maximum allowable value of the attained EEDI permissible for a specific ship type and size. The Required EEDI represents a minimum energy efficiency requirement for new ships depending on ship type and size. This begins with a baseline in 2013 and is raised successively in three steps until 2025. The baseline for required EEDI is calculated from the EEDI of vessels built after the millennium.The EEDI assesses the energy consumption of the vessel at noral seafaring condition, taking into account the energy required for propulsion and the hotel load for the crew. Energy consumed to maintain the cargo and for the manoeuvring or ballasting is not considered. The Required EEDI is calculated for all ship types using 100% of the dead weight at summer draft,except for passenger ships where GT is used. According to MARPOL Annex 6 chapter 4 regulation 21 Required EEDI is:-
(1-x/100) * Reference line value
The reference value is defined by a line which is mathematically defined as :-
                                                         -c                                                    
Required EEDI = a*b
The value of a,b and c is as follows:-
                                                               a                                 b                                    c
Bulk carrier                                    961.7                             dwt                               0.447
Tankers                                         1218.8                              dwt                              0.488
Containers                                      174.22                            dwt                               0.201

The Required EEDI will be reduced by 'X' % each five year based on initial value (Phase 0) and depending on vessel size. Below a certain size no reduction applies. Above a certain size reduction is in general 10% for each reduction phase. In between of these sizes the reduction is linearly interpolated.

ATTAINED EEDI

It means the EEDI value actually achieved by any individual ship. The attained EEDI is the actual calculated and verified EEDI value for an individual ship based on the data in the EEDI technical file. It shall be calculated for all ships of 400 GT and above. The attained EEDi must be below the 'Required EEDI' limit prescribed in MARPOL. 
                CO2 emission
EEDI= ---------------------
                Transport Work

CO2 emission is computed from the fuel consumption taking into account the carbon content of the fuel. The fuel consumption is based on the power used for propulsion and auxiliary power measured at defined design condition.
   The transport work is estimated by the designated ship capacity multiplied by the ship's speed measured at maximum summer load draft and at 75% of rated installed power. The total propulsion power is also defined as 75% MCR of all main engines.

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