2 Energy Efficiency Existing Ship Index (EEXI)
2.1 EEXI formula
The attained Energy Efficiency Existing Ship Index (EEXI) is a measure of ship's
energy efficiency (g/t*nm) and calculated by the following formula:
* If part of the Normal Maximum Sea Load is provided by shaft generators,
SFCME and CFME may – for that part of
the power – be used instead of SFCAE and CFAE
** In case of PPTI(i) > 0, the average weighted value of
(SFCME · CFME) and
(SFCAE · CFAE) to be used for calculation of
Peff
- Note: This formula may not be applicable to a ship having
diesel-electric propulsion, turbine propulsion or hybrid propulsion system,
except for cruise passenger ships and LNG carriers.
Ships falling into the scope of EEDI requirement can use their attained EEDI
calculated in accordance with the 2018 Guidelines on the method of calculation of
the attained EEDI for new ships (resolution MEPC.308(73), as amended, the "EEDI Calculation Guidelines"
hereafter) as the attained EEXI if the value of the attained EEDI is equal to or
less than that of the required EEXI.
2.2 Parameters
For calculation of the attained EEXI by the formula in paragraph 2.1, parameters
under the EEDI Calculation Guidelines apply, unless expressly provided otherwise. In
referring to the aforementioned guidelines, the terminology "EEDI" should be read as
"EEXI".
2.2.1 PME(i) ; Power of main engines
In cases where overridable Shaft / Engine Power Limitation is installed in accordance
with the 2021 Guidelines on the shaft / engine power limit to comply with the
EEXI requirements and use of a power reserve (resolution MEPC.335(76)), PME(i) is 83% of the limited
installed power (MCRlim) or 75% of the original installed power
(MCR), whichever is lower, for each main engine (i). In cases
where the overridable Shaft / Engine Power Limitation and shaft generator(s) are
installed, in referring to paragraph 2.2.5.2 (option 1) of the EEDI Calculation
Guidelines, "MCRME" should be read as "MCRlim".
For LNG carriers having steam turbine or diesel electric propulsion,
PME(i) is 83% of the limited installed power
(MCRlim, MPPlim), divided by the electrical
efficiency in case of diesel electric propulsion system, for each main engine
(i). For LNG carriers, the power from combustion of the excessive natural
boil-off gas in the engines or boilers to avoid releasing to the atmosphere or
unnecessary thermal oxidation should be deducted from PME(i) with
the approval of the verifier.
2.2.2 PAE(i) ; Power of auxiliary engines
2.2.2.1 PAE(i) is calculated in accordance with paragraph 2.2.5.6
of the EEDI Calculation Guidelines.
2.2.2.2 For ships where power of auxiliary engines (PAE) value
calculated by paragraphs 2.2.5.6.1 to 2.2.5.6.3 of the EEDI Calculation Guidelines
is significantly different from the total power used at normal seagoing, e.g. in
cases of passenger ships, the PAE value should be estimated by the
consumed electric power (excluding propulsion) in conditions when the ship is
engaged in a voyage at reference speed (Vref) as given in the
electric power table, divided by the average efficiency of the generator(s) weighted
by power (see appendix 2 of the EEDI Calculation Guidelines).
2.2.2.3 In cases where the electric power table is not available, the
PAE value may be approximated either by:
-
.1 annual average figure of PAE at sea from
onboard monitoring obtained prior to the EEXI certification;
-
.2 for cruise passenger ships, approximated value of power of
auxiliary engines (PAE,app), as defined below:
.3 for ro-ro passenger ships, approximated value of power of
auxiliary engines (PAE,app), as defined below:
2.2.3 Vref ; Ship speed
2.2.3.1 For ships falling into the scope of the EEDI requirement, the ship speed
Vref should be obtained from an approved speed-power curve
as defined in the 2014 Guidelines on survey and certification of the Energy
Efficiency Design Index (EEDI), as amended (resolution MEPC.254(67), as amended).
2.2.3.2 For ships not falling into the scope of the EEDI requirement,
the ship speed Vref should be obtained from an estimated
speed-power curve as defined in the 2022 Guidelines on survey and certification
of the attained EEXI (resolution MEPC.351(78)).
2.2.3.3 For ships not falling into the scope of the EEDI requirement but
whose sea trial results, which may have been calibrated by the tank test, under the
EEDI draught and the sea condition as specified in paragraph 2.2.2 of the EEDI
Calculation Guidelines are included in the sea trial report, the ship speed
Vref may be obtained from the sea trial report:
-
[knot]
-
where,
-
VS,EEDI, is the sea trial service speed under the
EEDI draught; and
-
PS,EEDI is power of the main engine corresponding
to VS,EEDI.
2.2.3.4 For containerships, bulk carriers or tankers not falling into the scope of
the EEDI requirement but whose sea trial results, which may have been calibrated by
the tank test, under the design load draught and sea condition as specified in
paragraph 2.2.2 of the EEDI Calculation Guidelines are included in the sea trial
report, the ship speed Vref may be obtained from the sea trial
report:
-
[knot]
-
where,
-
VS,service is the sea trial service speed under the
design load draught;
-
DWTS,service is the deadweight under the design
load draught;
-
PS, service is the power of the main
engine corresponding to VS,service;
-
k is the scale coefficient, which should be:
-
.1 0.95 for containerships with 120,000 DWT or less;
-
.2 0.93 for containerships with more than 120,000
DWT;
-
.3 0.97 for bulk carrier with 200,000 DWT or less;
-
.4 1.00 for bulk carrier with more than 200,000 DWT;
-
.5 0.97 for tanker with 100,000 DWT or less; and
-
.6 1.00 for tanker with more than 100,000 DWT.
2.2.3.5 In cases where the speed-power curve is not available or the sea
trial report does not contain the EEDI or design load draught condition, the ship
speed Vref can be obtained from the in-service performance measurement
method conducted and verified in accordance with the methods and procedures as
specified in the Guidance on methods, procedures and verification of in-service
performance measurements (MEPC.1/Circ.901).
2.2.3.6 In cases where the speed-power curve is not available or the sea trial report
does not contain the EEDI or design load draught condition, the ship speed
Vref can be approximated by Vref,app to
be obtained from statistical mean of distribution of ship speed and engine power, as
defined below:
-
[knot]
-
For LNG carriers having diesel electric propulsion system and
cruise passenger ships having non-conventional propulsion,
-
[knot]
-
where,
-
Vref,avg is a statistical mean of distribution of
ship speed in given ship type and ship size, to be calculated as
follows:
-
Vref,avg = A ✕ BC
-
where
-
A, B and C are the parameters given in the appendix;
-
mV is a performance margin of a ship, which
should be 5% of Vref,avg or one knot,
whichever is lower; and
-
MCRavgis a statistical mean of distribution of MCRs
for main engines and MPPavg is a statistical mean
of distribution of MPPs for motors in given ship type and ship size,
to be calculated as follows:
- In cases where the overridable Shaft / Engine Power Limitation is installed, the
ship speed Vref approximated by Vref,app
should be calculated as follows:
-
[knot]
-
For LNG carriers having diesel electric propulsion system and cruise
passenger ship having non-conventional propulsion, the ship speed
Vref approximated by Vref,app
should be calculated as follows:
-
2.2.3.7 Notwithstanding the above, in cases where the energy saving
devicefootnote is installed, the effect of the device may be
reflected in the ship speed Vref with the approval of the
verifier, based on the following methods in accordance with defined quality and
technical standards:
-
.1 sea trials after installation of the device; and/or
-
.2 in-service performance measurement method; and/or
-
.3 dedicated model tests; and/or
-
.4 numerical calculations.
2.2.4 SFC; Certified specific fuel consumption
In cases where overridable Shaft / Engine Power Limitation is installed, the
SFC corresponding to the PME should be interpolated by
using SFCs listed in an applicable test report included in an approved
NOX Technical File of the main engine as defined in paragraph 1.3.15
of the NOx Technical Code.
Notwithstanding the above, the SFC specified by the manufacturer or confirmed
by the verifier may be used.
For those engines which do not have a test report included in the
NOX Technical File and which do not have the SFC specified by
the manufacturer or confirmed by the verifier, the SFC can be approximated by
SFCapp defined as follows:
-
SFCME,app = 190 [g/kWh]
-
SFCAE,app = 215 [g/kWh]
2.2.5 CF ; Conversion factor between
fuel consumption and CO2 emission
For those engines which do not have a test report included in the NOX
Technical File and which do not have the SFC specified by the manufacturer,
the CF corresponding to SFCapp should be defined
as follows:
Otherwise, paragraph 2.2.1 of the EEDI Calculation Guidelines applies.
2.2.6 Correction factor for ro-ro cargo and ro-ro passenger ships
(fjRoRo)
For ro-ro cargo and ro-ro passenger ships, fjRoRo is
calculated as follows:
-
; if fjRoRo > 1 then
fj = 1
-
where the Froude number, FnL, is defined as:
-
-
and the exponents ɑ, β, ɣ and δ are defined as follows:
| Ship type
|
Exponent:
|
|
|
ɑ
|
β
|
ɣ
|
δ
|
| Ro-ro cargo
ship
|
2.00
|
0.50
|
0.75
|
1.00
|
| Ro-ro passenger
ship
|
2.50
|
0.75
|
0.75
|
1.00
|
2.2.7 Cubic capacity correction factor for ro-ro cargo ships (vehicle carrier)
(fcVEHICLE)
For ro-ro cargo ships (vehicle carrier) having a DWT/GT ratio of less than 0.35, the
following cubic capacity correction factor, fcVEHICLE, should
apply:
Where DWT is the capacity and GT is the gross tonnage in accordance with the
International Convention of Tonnage Measurement of Ships 1969, annex I, regulation
3.