ee-wg 2-2-1 - various corrigenda items (bimco)

I:\MEPC\EEWG\2\2-1.doc

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INTERSESSIONAL MEETING OF THE WORKING GROUP ON ENERGY EFFCIENCY MEASURES FOR SHIPS 2nd session Agenda item 2

EE-WG 2/2/12 December 2011 ENGLISH ONLY

FUTHER IMPROVEMENT OF GUIDELINES

ON THE METHOD OF CALCULATION OF THE EEDI FOR NEW SHIPS

Various corrigenda items

Submitted by BIMCO

SUMMARY

Executive summary: A number of corrigenda and shortcomings have been identified in the guidelines on the method of calculation of the EEDI, and possible corrective action is proposed

Strategic direction: 7.3

High-level action: 7.3.2

Planned output: 7.3.2.1

Action to be taken: Paragraph 15

Related documents: MEPC 61/WP.10; MEPC 62/5/4 and MEPC 62/24

Introduction 1 BIMCO has developed an EEDI calculator based on the present EEDI calculation guidelines. During the test period of the EEDI calculator, a number of corrigenda and shortcomings in the EEDI guidelines have been identified. These are listed in this submission and possible corrective action is proposed. Discussion 2 According to section 2 of annex 1 to document MEPC 62/5/4, the EEDI is calculated by the following formula:

Note: This formulae may not be able to apply to diesel-electric propulsion, turbine propulsion or hybrid propulsion system.

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In order to equitably accommodate for shaft motor propulsion in the formula, it will be necessary to correct PAE as well as SFCME in the innovative mechanical energy efficient technology for propulsion accordingly. 3 The ship speed, Vref, as defined in sections 2.2 and 2.5 of annex 1 to document MEPC 62/5/4, is believed to have a somewhat unclear definition in case of applied shaft motors. In section 2.5.3 of annex 1 to MEPC 62/5/4, it is stated that:

"PPTI(i) is 75% of the rated power consumption of each shaft motor divided by the weighted averaged efficiency of the generator(s)".

This figure is to be included in the formula for calculating the CO2 emission per nm*tonnes. However, in order to take into account shaft motors, either completely or partly in the ship speed, Vref, during sea trial (where such shaft motors may not be engaged), it will be necessary to calculate the equivalent power from the shaft motors delivered to the propeller. 4 In section 2.5.1 of annex 1 to MEPC 62/5/4, two proposals are given:

"PME(i) is 75% of the rated installed power (MCR) for each main engine (i) after having deducted any installed shaft generator(s): PME(i) = 0.75 x (MCRME(i) – PPTO(i)) [Irrespective of the maximum output of an installed shaft generator, the maximum allowable deduction of 75% of PPTOi within the calculation of PME(i) is to be no more than PAE as defined in 2.5.6. Where power from the shaft generator is being used for cargo loads under normal seagoing conditions, (e.g. reefer containers) then these should not be included in the calculation. For specialized designs, where an engine is installed with a higher power output than the shaft(s) and propeller(s) are capable of delivering, then the value of PME(i) used for EEDI purposes is 75% of the power that the propulsion system is capable of delivering through the propulsor.] (Alternative proposal from BIMCO) [Where power from the shaft generator is being used for cargo loads under normal seagoing conditions (e.g. reefer containers) then these should not be included in the calculation. PME(i) is in all circumstances to be no less than 75% of the power that the propulsion system is capable of delivering through the propulsor.]"

5 An example of the shaft generator's influence on the EEDI value from the above two proposals can be exemplified as follows on a fictive ship:

MCRME(i) 20,000 kW

DWT 20,000 tonnes

Vref 20 knots

SFCME(i) 170 g/kWh

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SFCAE(i) 200 g/kWh

M/E and A/E on HFO

CF 3.114, No WHR

PTI or innovative technologies

All f factors are 1.0

.1 Example 1: No shaft generator

PME(i) = 0.75 x 20,000 kW =15,000 kW

PAE(MCRME≥10000kW) = (0.025 x 20,000) + 250 = 750 kW

EEDI = ((15,000 x 3.114 x 170) + (750 x 3.114 x 200))/(20 x 20,000)

= 21.02 gCO2/nm*t

.2 Example 2: Shaft generator according to proposal number 1

PME(i) = 0.75 x (20,000 kW – 750 kW) = 14,438 kW

Vref

at 14,438 kW = (203.5

x 14,438/15,000)(1/3.5)

= 19,78 knots

EEDI = ((14,438 x 3.114 x 170) + (750 x 3.114 x 170)) / (19.78 x 20,000)

= 20.32 gCO2/nm*t

Reduction of EEDI by fitting of shaft generator: 3.3%

.3 Example 3: Shaft generator according to proposal number 2

PME(i) = 0.75 x 20,000 KW = 15,000 kW (no reduction for shaft generator)

EEDI = ((15,000 x 3.114 x 170) + (750 x 3.114 x 170)) / (20 x 20,000)

= 20.84 gCO2/nm*t

Reduction of EEDI by fitting of shaft generator: 0.9%

The use of proposal number 1 will in general give EEDI reductions of 3-4% (PAE and SFCME(i)). The use of proposal number 2 will in general give EEDI reductions of around 1% (SFCME(i)). 6 In section 2.5.2 of annex 1 to document MEPC 62/5/4, it is stated that:

"PPTO(i) is 75% output of each shaft generator installed divided by the relevant efficiency of that shaft generator."

PPTO(i) is used in the formula: PME(i) = 0.75 x (MCRME(i) – PPTO(i)). If a shaft generator with poor efficiency is chosen, the resulting PME(i) and final EEDI value will be better.

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7 In section 2.11.1 of annex 1 to document MEPC 62/5/4, the capacity correction factor, fi, for ice-classed ships should be taken as the lesser value of fi0 and fi,max as tabulated in Table 1, but not less than fi,min = 1.0.

Table 1: Capacity correction factor fi for ice-classed ships

Ship Type

fi0 fi,max Depending on Ice Class

IC IB IA IA Super

Tanker Capacity

L00115.0 36.3PP 05.0

PPL31.1 07.0PPL54.1 09.0

PPL80.1 11.0PPL10.2

Bulk Carrier Capacity

L000665.0 44.3PP 05.0

PPL31.1 07.0PPL54.1 09.0

PPL80.1 11.0PPL10.2

General Cargo Ship Capacity

L000676.0 44.3PP 1.0 1.08 1.12 1.25

Container Ship Capacity

L1137.0 29.2PP 1.0 04.0

PPL25.1 08.0PPL60.1 12.0

PPL10.2

Gas Carrier Capacity

L1749.0 33.2PP 04.0

PPL25.1 08.0PPL60.1 12.0

PPL10.2 1.0

8 For Gas Carriers in 1A Super ice class, there appears to be a problem with the content of Table 1 . An example with a Gas Carrier with a length, Lpp, of 153 metres and a capacity of 20,000 DWT would give the following result:

Ship Type


IC IB IA IA Super

Gas Carrier

1.06 1.02 1.07 1.15 1.0

The resulting correction factor, fi, would then be 1.0 for a Gas Carrier of ice class 1A Super and 1.06 for a Gas Carrier of ice class 1A. In this case the Gas Carrier with ice class 1A will have the lowest EEDI value. This is considered to be incorrect. Proposal 9 In order to equitably incorporate shaft motor propulsion into the EEDI formula it is proposed to amend the existing formula as given in section 2 of annex 1 to document MEPC 62/5/4, as follows:

* If part of the Normal Maximum Sea Load is provided by shaft generators, SFCME may –

for that part of the power – be used instead of SFCAE ** In case of PPTI(i)>0, the average weighted value of SFCME and SFCAE to be used for

calculation of Peff

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PAE(MCRME≥10000KW) = 25075,0

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10 In order to get an explicit definition of the shaft power, at where the ship speed, Vref, is measured, a new paragraph needs to be inserted in section 2.5.4 of annex 1 to document MEPC 62/5/4:

PPTI(i)shaft is 75% output of the rated power consumption of each shaft motor multiplied by its motor efficiency.

The propulsion power at which Vref is measured is: ∑PME(i) + ∑PPTI(i)shaft. 11 As a shaft generator is just another diesel generator, there seems to be no logical reason for deducting it from MCRME(i), when calculating PME(i) and corresponding EEDI, except in cases where the maximum allowable propulsion power is lower than the engine MCR. However, as shaft generators are driven by main engines which usually have a better fuel efficiency compared to auxiliary diesel engines, it is equitable to use the better SFCMCR(i) instead of SFCAE(i) in the formula. 12 It is therefore proposed to use the the text in section 2.5 of annex 1 to document MEPC 62/5/5:

Where power from the shaft generator is being used for cargo loads under normal seagoing conditions, (e.g. reefer containers) then these should not be included in the calculation. PME(i) is in all circumstances to be no less than 75% of the power that the propulsion system is capable of delivering through the propulsor.

13 The EEDI calculation guidelines seem to incentivise use of shaft generators with poor efficiencies in the calculation of the EEDI. This means that a shaft generator with a low efficiency will give a better EEDI. Shipowners investing in shaft generators with high efficiencies should not be penalized in the EEDI formula. Section 2.5.2 of annex 1 to document MEPC 62/5/4 is proposed to be amended as follows:

PPTO(i) is 75% output of each shaft generator installed.

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14 In section 2.11.1 of annex to document MEPC 62/5/4, the capacity correction factor, fi, for ice-classed ships should be taken as the lesser value of fi0 and fi,max as tabulated in Table 1, but not less than fi,min = 1.0. For Gas Carriers in ice class 1A Super, there seems to be a problem with the table. Until the formula has been rectified, it is proposed that the ice-class factors for 1A Super and 1A are identical:

Ship Type


IC IB IA IA Super

Gas Carrier Capacity

L1749.0 33.2PP 04.0

PPL25.1 08.0PPL60.1 12.0

PPL10.2 12.0PPL10.2

Action requested of the Intersessional Meeting 15 The Intersessional Meeting is invited to consider these proposals, and take action as appropriate.

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ee-wg 2-2-1 - various corrigenda items (bimco)

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