imo eedi general cargo vessels report
DESCRIPTION
Cargo ShipTRANSCRIPT
A study on a fairer inclusion of small General cargo ships and
small Containerships within the EEDI regulatory framework
Place and date: Groningen, 26 June 2012
MARIN Michiel Verhulst MSc.
Conoship International B.V. Jan Jaap Nieuwenhuis MSc.
Wieger Duursema B.MO
Contents
1 Introduction ....................................................................................................................................... 1
2 Causes for low reference line correlation and potential alternative measures ................................ 5
3 Effect of operational profile on EEDIAttained for General cargo ships < 20.000 dwt ........................... 9
3.1 Showing the need for a high minimum operational speed ....................................................... 11
3.2 Systematic assessment of the Attained EEDI for fast General Cargo Vessels ...................... 16
3.3 Analysis of the degree of optimization of General cargo ships for EEDI ................................. 18
3.4 Unambiguous definition of speed for General cargo ships ...................................................... 22
3.5 Correction factor to account for speed differences between General cargo ships .................. 26
3.6 Evaluation of correction factor against IMO requirements ....................................................... 29
4 Effect of Cargo handling gear on EEDI for General cargo ships < 20.000 dwt ............................. 31
4.1 Correction factor for cranes ...................................................................................................... 33
4.1.1 Quantification of crane weights ........................................................................................ 35
4.1.2 Correction factor for Cranes ............................................................................................ 36
4.2 Correction factor for sideloaders and Ro-Ro ramps ................................................................. 37
4.3 Evaluation of correction factor against IMO Requirements ...................................................... 38
5 Effect of additional class notations on scatter of Attained EEDI values ......................................... 40
5.1 Correction factor for additional class notations ........................................................................ 41
5.2 Evaluation of correction factor against IMO Requirements ...................................................... 43
6 Effect of the additional correction factors on the scatter of Attained EEDI values ......................... 44
7 Conclusions and discussions ......................................................................................................... 51
Executive summary
CMTI commissioned MARIN and Conoship International B.V. to investigate the cause of the poor
reference line correlation for small General cargo ships and small Containerships and to propose
alternative measures to improve the inclusion of these vessels within the EEDI regulatory framework.
A project group, consisting of Dutch Shipbuilders, Ship owners, Ship designers, Classification
societies and Tank test facilities have been acting as a critical sounding board during the study.
Furthermore, several parties from the project group delivered a vital part of the data as used for the
study. For this study a database was created with General Cargo Vessels smaller or equal to 20.000
dwt, consisting of detailed ship particulars and design parameters.
The study shows that three key factors can be identified which cause the high scatter. The first factor
is the large variety in minimum required operational speed for small General cargo ships. The second
factor is the variety in loading equipment installed, which causes deadweight variations for vessels
with comparable displacements and main dimensions. The third factor is the variety in additional class
notations (or structural class notations), which causes a variety in lightweight, and therefore in
deadweight for vessels with comparable main dimensions and displacement.
To resolve the high scatter and low R2, it is proposed to implement three additional corrections factors
for General cargo ships with a Capacity below 20.000 dwt :
1. Factor to account for the differences in minimum required operational speed between small
General cargo ships that have been optimised for different trades, fj;
2. Factor to account for the differences between ships with and without cargo handling
equipment, fl;
3. Factor to address differences in additional class notations that can lead to a relatively higher
lightweights, fi,Gen.Cargo.
The study showed that to account for the differences in minimum operational speed a correction on
power is the most suited solution. This correction factor is to consider the block coefficient and the
volumetric Froude number to account for the variation in speed and the vessels displacement and
main dimensions. The resulting factor is:
3.03.2
174.0
b
jCFn
f
In which:
Fn= volumetric Froude Number
Cb= block coefficient
In case fj is equal or larger than 1, a fj of 1 should be applied.
With respect to the factor fl, which accounts for the weight of loading equipment, a proposal is made
for the calculation of the additional lightweight due to cranes. The calculation is based on crane
specific characteristics, namely the Safe Working Load of the crane and the reach.
Capacity
achSWL
f
n
n
nn
cranes
1
11.32Re0519.0
1
A similar method can be applied to calculate the additional weight due to the other types of loading
equipment, such as side loaders and RoRo ramps. The formula's become:
Capacity
Capacityf
ssideloaderNo
sideloader and Capacity
Capacityf
RoRoNo
RoRo
Considering the largely ship specific designs of these two types of loading gear, it is proposed to
define the calculation of the correction factor fsideloader and fRoRo based on a direct calculation method,
analogue to the voluntary structural enhancement correction factor.
Finally a proposal is done for the inclusion of a correction factor for the additional class notations. It is
proposed to account for the additional weight of these notations by means of the voluntary structural
enhancement factor, fiVSE.
Implementation of these three new correction factors is deemed to be justified as they correct for a
variation that is caused in order to be able to provide essential services to the society and therefore
create an additional “benefit for society”, besides their capabilities to transport a certain Capacity. Not
offering these services would result in a modal shift to road transport or otherwise result in increased
CO2 emissions, for example because of the need to operate with a larger number of vessels. Not
including these new correction factors could even lead to an impossibility to replace the existing
tonnage with vessels with equal capabilities, which is expected to be counter productive regarding the
aim of the EEDI regulations. Furthermore, the proposed correction factors follow the criteria for new
correction factors as stated by IMO. They are all based on verifiable characteristics, provide a ship
specific solution, are based on a comprehensive and transparent analysis, are clear and easy to use
and do not create perverse incentives.
By applying these factors, the (mutual) comparison of General cargo ships with a Capacity up to
20.000 dwt improves. For the vessels in the database of this study the R2 increases from about 0.4 to
about 0.55 and the scatter of attained EEDI values thus clearly decreases. The resulting correlation
between reference lines and EEDI values is however still considerably less than the correlation as
found for bulk carriers or tankers. The diversity in mission profiles and the resulting differences in the
design of General cargo ships are so large, that many more correction factors would be required to
reach correlation values similar to those for bulkers and tankers. The correlation for General cargo
ships could further be improved by taking into account aspects such as the effect of the large
differences between design conditions and maximum load conditions of some General cargo ships.
Implementation of the three proposed correction factors improves the inclusion of small general cargo
ships in the EEDI regime. In this way also General cargo ships specially designed for niche markets
with very specific operational profiles can be assessed in a fair manner. However, the inclusion of
correction factors for General cargo ships in the EEDI regime does not take away the need to take
measures to optimize the energy efficiency to fulfil future EEDI requirements, as a substantial number
of the existing designs do not meet the phase1 and phase 2 requirements with the new correction
factors applied.
1
1 Introduction
During the 62nd
session of the Marine Environment Protection Committee a new chapter of MARPOL
ANNEX VI was adopted. This new chapter aims to reduce the emission of Greenhouse Gases by
shipping and more specifically aims to reduce CO2 emissions, since CO2 is the most important
Greenhouse Gas emitted by ships. One of the most noticeable aspects of the new regulations is the
“Energy Efficiency Design Index”, or EEDI, which defines a minimum “energy efficiency level”,
expressed in tons of CO2 emitted per “Capacity mile”, which all new designs should meet.
Even though the new MARPOL regulations come into force as of the first of January 2013 many
concerns regarding the effect of the EEDI regulations for small General cargo ships and small
Containerships still exists. With the currently accepted formula and guidelines there continues to be a
high scatter of Attained EEDI values for the smaller deadweight ranges for General cargo ships and
Containerships, as amongst others shown by Krikke and Anink [1]. Because of the difficulties with the
derivation of a robust reference line for the smaller vessels, Small General cargo ships up to 15000
dwt. have been excluded from the first phase of implementation of the EEDI requirements. Within this
study a slightly wider deadweight range, up to 20.000 dwt, is considered, as in our opinion the large
variety in vessel characteristics can be found up to 20.000 dwt. instead of up to 15.000 dwt. We further
expect that the problems encountered for small General cargo ships are comparable to problems
encountered for Containerships between 10.000 dwt and 20.000 dwt (for Containerships below 10.000
dwt there is no maximum EEDI requirement). A large part of this work is thus considered to be
applicable for small Containerships as well.
Figure 1 The “R2“ factor for General cargo ships as used for the definition of the reference line
by IMO. [MEPC 62/6/4]
2
From January 2015 the small General cargo ships (3000 – 15000 dwt) however do have to comply
with the phase 1 EEDI requirements. In the meantime IMO invites parties to propose alternative
measures or methods to improve robustness of the EEDI methodology for small General cargo ships.
CMTI commissioned MARIN1 and Conoship International B.V.
2 to further investigate the cause of the
poor reference line correlation for small General cargo ships and small Containerships and to propose
alternative measures to improve the inclusion of these vessels within the EEDI regulatory framework.
For this study MARIN and Conoship made a systematic assessment of the scatter as found for small
General cargo ships and Containerships, based on a database containing the detailed characteristics
of over 70 vessels. The vessels in the database are Conoship designs and/or vessels extensively
tested and optimized by MARIN. Please note that the level of detail of the characteristics in this
database is much higher than the data in the IHS Fairplay database and includes over 40
characteristics, such as: lightweight, weight of loading equipment, estimated weight increase for
additional class notations, design restrictions due to foreseen sailing area, etc. All of the vessels in the
database are built and are currently in operation. Although the dataset contains vessels up to 20.000
dwt the majority of the vessels lays within the 10.000 dwt range, as can be seen in Figure 3.
Together the vessels in the database span the deadweight range between 3000 and 20.000 dwt and
cover the wide variety of General cargo ship designs. See for example the vessels in Figure 2, which
are all included in the database, and all represent a different type of General cargo ship.
Figure 2 Overview of wide variety of General cargo ships
1 Maritime Research Institute Netherlands, independent and innovative service provider for the
maritime sector and a contributor to the well being of society, see www.marin.nl
2 A Dutch Ship Design Office, specialized in the design of Short Sea General cargo ships, see
www.conoship.com
3
Figure 2 shows six completely different vessels, which are all considered to be, and classified as,
General cargo ships. Starting in the upper left corner and going clockwise, the first figure shows a
relatively large General cargo ship with a length of over 180 m, equipped with a large variety of cargo
handling gear such as cranes and sideloaders. The second picture shows a General cargo ship
designed for and operating in a container trade. The third picture shows a General cargo ship without
cargo handling gear, optimized for a Short Sea Shipping Trade in Western Europe, the Mediterranean
and the Baltic. The figure in the lower right corner, shows a General cargo ship designed and
optimized for the carriage of bulk cargo. The fifth vessel is a high speed General Cargo Ship,
equipped with heavy load cranes, operating as a “mini heavy lift vessel”. The sixth vessel, in the lower
left corner, is a low speed General Cargo Ship optimized for the sea-river trade.
An analysis of the vessels in the database shows that also for these vessels calculating the attained
EEDI values results in a wide scatter, especially in the deadweight range up to 10.000 dwt. See Figure
3.
Phase 2
Phase 0
0
5
10
15
20
25
30
35
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, with factors fi and fj applied
Figure 3 Attained EEDI values of the vessels in the database. Correction factors fi and fj for ice
class correction are applied according to the Guidelines of MEPC 63.
Furthermore a substantial number of the current small General cargo ship designs do not meet the
EEDI requirements. Although they are excluded from the phase 0 requirements, they do have to meet
the phase 1, 2, and 3 requirements. A number of the vessels that do not comply are very recent
additions to the General cargo ship fleet, further see chapter 3. The fact that recent designs, optimized
4
with the latest techniques, do not comply makes it a relevant problem as it shows the demand for
these specialist vessels. Without any additional correction factors, it is expected that building and
operating a new ship based on these designs will in the future be no longer possible. The vessels are
already hydrodynamically optimized and the foreseen technological developments to reduce CO2
emissions, such as operating on LNG, will not provide sufficient solace to meet the phase 1 and 2
requirements3, as is further shown in chapter 3. Not including additional correction factors within the
EEDI regulatory framework, to improve inclusion of small General cargo ships and Containerships,
may lead to unwanted effects on future designs and could affect the competitive position of shipping
and limit its growth due to a modal shift to road or air transport.
The aim of this study is to provide an analysis and an explanation for the wide scatter as found for
General cargo ships and small Containerships and to provide alternative measures to improve their
inclusion in the EEDI regulatory framework. The study is limited to General cargo ships and small
Containerships between 3.000 and 20.000 dwt. The study aims to provide an explanation for the
complete scatter, and not only for those vessels that don’t comply with the phase 2 regulations.
In chapter 2 of this report possible causes for a low reference line correlation for small General cargo
ships are identified, which lead to the proposition of a number of additional correction factors. Chapter
3 describes a proposal for a correlation factor to reduce the scatter to account for the large variety
within the operational profile of General cargo ships. Chapter 4 provides a proposal for a correction
factor to include the wide variety loading gear as found amongst General cargo ships. Chapter 5
shows a proposal to account for the wide variety of additional class notations, such as “GRAB”,
“Loading Aground”, or “non-homogeneous load”. In chapter 6 the effect of these proposals on the
reference line correlation is analysed. The report is concluded with chapter 7, providing the
conclusions and recommendations.
3 Phase 3 requirements, from January 2025, are considered to be “far future” for General cargo ships
and are therefore not taken into account. Further the IMO will review the status of the technological
developments at the midpoint of phase 2 and if necessary amend the time periods or reduction rates.
5
2 Causes for low reference line correlation and potential
alternative measures
Previous research has numerous times shown a low reference line correlation for General cargo
ships. See amongst others [1], [2] and [3]. The “R2“ factor
4 for General cargo ships as used for the
definition of the reference line by IMO, based on the IHS Fairplay dataset is as low as 0.334 [MEPC
62/6/4], see again Figure 1.
Especially in the low deadweight range, i.e. the topic of this study, the scatter is very wide. When
Attained EEDI values are calculated for the more than 70 vessels in the database of this study, in a
way similar to the reference line calculations of IMO, thus without considering the Ice Class
Correction, the correlation factor for the vessels in the database becomes 0.403, see Figure 4. See
the R2 of 0.403 corresponding to the trend line in Figure 4. Even though this is higher than the R
2 of
0.334 as found by IMO based on the IHS Fairplay database, it still represents a poor correlation. It is
expected that the dataset of this study is slightly more homogeneous than the dataset of IHS Fairplay,
as it mainly consists of vessels owned by Dutch ship owners and/or designed/built by Dutch shipyards,
resulting in a slightly higher R2.
Phase 2
Phase 0
R² = 0.403
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, without corrections applied
Figure 4 Attained EEDI values of General cargo ships, without correction factors applied.
4 The R
2 coefficient, or the correlation coefficient, is a statistical measure which indicates how close
the regression line approximates the real data points. A R2 of 1 indicates a perfect fit.
6
For other ship types, such as bulk carriers and tankers the correlation is much higher, and R2 values
over 0.92 are found [MEPC 62/6/4].
Figure 5 Correleation of Attained EEDI valus, of tankers equal to or larger than 400 GT. [MEPC
62/6/4]
Amongst others Anink and Krikke showed that General cargo ship designs show a large variety,
regarding speed, installed power, block coefficient and other characteristics, such as Ice Class or
sailing area, even within a small deadweight range [3]. For Short Sea Cargo ships, which most of the
small General cargo ships and small Containerships are, but also for most Ro-Ro ships, the diversity
in mission profile and operational conditions makes it difficult to establish a robust reference line,
which is reflected by a low correlation factor [4]. Further, due to the optimisation of small General
cargo ships for specific trades and routes, especially in the small deadweight range, the vessels are
not able to do each other's work, despite their "branding" as General cargo ship. And, since the EEDI
Reference line is based on all of these vessels a substantial number of vessels cannot meet the
requirements because of their optimization.
7
Phase 2
Phase 0
0
5
10
15
20
25
30
35
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, with factors fi and fj applied
Figure 6 Attained EEDI values, with ice class correction factors fi and fj applied
In co-operation with experienced designers from Conoship International B.V. and through a “ship by
ship” analysis of the differences between the vessels in the database, it is concluded that the diversity
in mission profiles and operational conditions for small General cargo ships, amongst others result in
large differences between vessels within the same deadweight range regarding:
- Required minimal operational speed, resulting in large difference in installed power and main
dimensions (and therefore in the lightweight / displacement ratio);
- Sailing area for which the vessel is designed and optimized, which could result in large
differences of main dimensions (L, B, T), amongst others due to main dimension restrictions in
ports, canals, locks, etc.;
- Ice Class Notation, ranging from no ice class up to 1A Super;
- Loading equipment installed, for example cranes, side loaders, RoRo ramps, or a combination
of these, resulting in large differences in the lightweight / displacement ratio;
- Main engine type, main engine speed, fuel types (HFO/MDO/GO) and fuel consumption;
- Additional Class notations such as “loading aground”, “GRAB”, “strengthened tanktop”, which
consequently can result in large differences in the lightweight / displacement ratio;
- Hold volume, which consequently results in large differences in gross tonnage and lightweight;
- The difference between the design conditions and the vessel’s maximum capabilities. For
example some General cargo ships have a design draft which corresponds with the maximum
scantling draft, while others are optimized (hull form, propulsion system) for a partially loaded
draft which can be considerably smaller (more than 2 meters) than the maximum draft. In
8
similarity, differences between the maximum speed and a substantially lower design speed
are found, which for example affects the design of the bulbous bow.
To improve the inclusion of the small General cargo ships within the EEDI regulatory framework, it is
proposed to implement a number of additional correction factors and consequently reduce the scatter
of Attained EEDI values in the low deadweight range. According to MEPC61/24 a proposal for a new
correction factor can be accepted by IMO, when a proposal for a new correction factor, follows the
following criteria [MEPC 61/24, paragraph 5.27]:
- A: verifiable ship characteristics and application;
- B: need for correction factor;
- C: best addressed with a ship-specific solution;
- D: comprehensive, transparent analysis to develop correction factors;
- E: clear instructions for determining a correction factor;
- F: does not create perverse incentives.
To prevent a strong increase of the number of correction factors, which would hamper the clarity of the
EEDI regulatory framework, we propose to introduce a limited number of correction factors to consider
for the differences between small General cargo ships. A qualitative analysis of the effect of the
various differences between General cargo ship in relation to the Attained EEDI, in combination with a
sensitivity analysis of the various parameters of the EEDI formula, led to the conclusion that the
introduction of a correction factor for the following aspects would have the most effect on the reduction
of the scatter:
- A factor to account for the large variation in operational profile (e.g. regarding range, speed)
between small General cargo ships up to 20.000 dwt;
- A factor to account for the differences in loading equipment for General cargo ships up to
20.000 dwt;
- A factor to account for the many differences in additional class notations for General cargo
ships up to 20.000 dwt.
The following chapters give a further analysis of the effect of these aspects on the Attained EEDI, the
proposals for the additional correction factors and a verification of the proposed correction factors
against the IMO criteria for a new correction factor.
9
3 Effect of operational profile on EEDIAttained for General
cargo ships < 20.000 dwt
General cargo ships below 20.000 dwt are designed and optimised for a large number of different
niche markets. Their common aspect is that all of the designs are suited to carry a wide variety of
cargos, even when they are optimized for a single cargo. For example a General cargo ship
specifically designed to carry steel pipes between Rotterdam and Oslo will be optimized for this trade.
This results in an optimized design for example regarding hold length, deadweight, speed required for
the round trip and tanktop load for this trade. However as a General cargo ship the vessel will be
designed in such a way that it is also capable of carrying grain, coal, or other bulk cargos, either as
return freight or during periods that the main trade is not available. Optimization for a specific niche
market results in a large variety of operational profiles within a deadweight range, especially regarding
the required minimum operational speed of the vessels. Figure 7 gives an overview of the Vref as found
for General cargo ships in this study and indicates the variety in minimum required operational speed.
C11
C7
C8
C9
C12
C5
C4
C14
C10
C3
C2
C6
C13
C1
B2
B1
B3
B4
A5
A4
A3
A2
A1
Slow
Fast
0,00
2,00
4,00
6,00
8,00
10,00
12,00
14,00
16,00
18,00
0 2000 4000 6000 8000 10000 12000 14000 16000
DWT [mt]
Vre
f [k
nots
]
Figure 7 Reference speed versus Deadweight
The wide variety in speed is clearly demonstrated by comparing the Vref of ship C1 and A3, two
General cargo ships with a deadweight of about 3800 dwt, but with a Vref varying between 9 and 15
kts, i.e. a difference of 66.6%.
A rough categorisation of common speeds for small General cargo ships can be found in Table 1.
10
Table 1 Common speeds of small General cargo ships
Deadweight range fast Normal speed slow
3000 – 7000 dwt. > 13 kts. 10.5 – 13 kts. < 10.5 kts.
7000 – 11000 dwt > 15 kts 12 – 15 kts < 12 kts
> 11000 dwt > 15 kts 12 – 15 kts < 12 kts
Bear in mind that these boundaries are not rigid and the definition of slow and fast (and speed in
general) is a fickle and relative notion in ship design, as it is strongly related to a ship’s main
dimensions, displacement, sailing area and trade.
Not surprisingly, the vessels with a high Vref of Figure 8 (A1 till A4) have an Attained EEDI that is much
higher than the maximum acceptable EEDI for phase 1 and 2. Whereas a number of the vessels at the
upper end of the “normal” speed range have some difficulties of making the EEDI requirements (B1 till
B4), while all of the vessels with a low Vref easily comply with the phase 2 requirements (C1-C18). This
indicates a relation between the variety in minimum operational speeds and subsequently a variety in
Vref and the wide scatter as found for General cargo ships.
C1
C13
C6
C2C3
C10
C14
C4
C5
C12C9
C8
C7
C11
B4B3
B1B2
A1
A2
A3A4
A5
0
5
10
15
20
25
30
35
0 2000 4000 6000 8000 10000 12000 14000 16000
DWT [mt]
EE
DI [g
CO 2
/(m
t*n
m)]
Figure 8 Attained EEDI versus Deadweight5
5 Vessels with Ice Class are not considered since the Ice Class correction hampers a direct
comparison between vessels within the same deadweight range.
11
The introduction of a correction factor to account for the large differences in the minimum required
operational speed of small General cargo ships could help to substantially reduce the wide scatter as
found for General cargo ships. Further it improves the inclusion of small General cargo ships with high
minimum operation speeds in the EEDI frame work. Such a correction factor is however only justified
when the need for a high operational speed can be shown, and when the proposal follows the other
criteria as set by IMO for a new correction factor. In the following sections the need for a correction
factor is elucidated and the correction factor itself is further developed.
3.1 Showing the need for a high minimum operational speed
A correction factor to account for the speed differences between General cargo ships, aiming to
reduce the wide scatter, shall mainly affect the General cargo ships with the higher Vref. As a result, a
higher number of the small General cargo ships could comply with the EEDI regulations. This is
considered to be justified whenever it can be shown that there is a clear need for General cargo ships
with a high Vref and that even optimized vessels are not able to meet the requirements. Without the
introduction of a additional correction factor to account for the large speed differences between
General cargo ships, a substantial number of General cargo ships, such as ship A1-A4 from Figure 8,
could no longer be built. This could distort the competition and limit trade and growth in shipping,
which contradicts with the consensus within IMO during earlier stages of the development of the EEDI
regulatory framework, and it could result in a global overall increase of CO2 emissions [5]. General
cargo ships with a high Vref currently cannot comply with the reference line requirements, as these
vessels require considerably more power, because of the third power relation between ship speed and
installed power. Due to the small number of General cargo ships with a high Vref in the IHS database,
the resulting reference line is so low, that faster vessels can never meet it.
General cargo ships with a high reference speed are the ultimate examples of multi-purpose dry cargo
vessels. They are designed for the carriage of special project cargos, containers, or for a combination
of project cargo and containers. However, to be economically feasible they are also suited and
designed for the carriage of dry bulk cargos, such as grain, just as their high operation relatives with
low minimum operational speed. Besides a similarity regarding their high operational speed, the
General cargo ships in the container trade, in general, differ from “dedicated” container feeders, for
example regarding the maximum tank top load, which for the General cargo ships is usually higher
than for a dedicated container feeder. Note that currently, due to the bad market conditions in the
container market, dedicated container feeders, designed exclusively for the carriage of containers, are
increasingly carrying project cargos and general cargos [6]. As it is unclear how IMO intends to deal
12
with these kind of situations6, the actual number of vessels with a Vref that might need to comply with
the EEDI requirements as a General cargo ship is potentially much larger. Without an additional
correction factor, potentially a considerable number of designs would no longer be feasible.
Specialized project cargos that require short delivery times form a special segment of the project
cargo market. Some examples of these kind of project cargos are:
- Yachts;
- Large spare parts for emergency repairs;
- Transport of heavy equipment for relief operations.
Figure 9 M.V. Deo Volente [Courtesy to Hartman Seatrade] and one of the S-gracht vessels
[Courtesy to Spliethoff]
For all project cargos that are transported by a General cargo ship with a high minimum required
operational speed, transport times are an important aspect within an overall project planning and the
differences in transport times between a “slow” and a “fast” General cargo ship are not to be
underestimated. On a trip of 4000 nm, the speed difference between 11 kts and 18 kts results in a
transport time difference of 5.9 days. For example, one of the fast General cargo ships from the
dataset as used for this study once was especially chartered because of its high operational speed to
transport two Azipods to a cruise vessel which suffered a damage to its propulsion system due to
grounding. In another voyage spare parts required for emergency repair of an offshore production
platform were transported. In such kind of voyages a difference in transport time of 6 days
considerably reduces the loss of services to the society.
6 It is not unimaginable that the definition of “exclusively designed for the carriage of containers” is to
be changed to “sailing exclusively with containers” to prevent designs being made as a dedicated
container vessels, while the owner actually intends to operate it as a combined General cargo ship /
container feeder.
13
The “benefit for society” of General cargo ships with a high minimum operational speed is clearly not
dominated by the deadweight they can carry, but especially by their capability to operate at higher
speeds. Their higher speed enables them to provide services which slower General cargo ships
simply could not provide. A number of specific niche markets can be identified, however ship-owners
are continuously working on development to enter new markets which especially for Short Sea
Shipping frequently results in shift from road transport to water.
A common operation for General cargo ships with a high operational speed is an operation as a small
container feeder with a mid-term charter and operating on fixed routes with fixed schedules. An
operation as container feeder naturally requires a higher speed, due to characteristics of the cargo
and the necessity to compete with “dedicated” container feeders. Furthermore, operating with a fixed
schedule requires a certain transport route to be completed within a certain time frame. To maintain
such a liner service requires the capability to make up for lost time due unavoidable circumstances.
This requires a high maximum speed, above the already high service speeds, which consequently
requires a high installed power. The main advantage of these General cargo ships compared to
dedicated Containerships is their flexibility. After finishing their contract as container feeder, they can
easily switch to operations as General cargo ship, or even as mini bulker. In total, as a result of the
multifunctional aspect of General cargo ships, less vessels are required to provide the same services.
Further, more and more liner services are set up for General cargo ships, especially for General cargo
ships with crane capacity, see for example the “Liner Services” as offered by Rickmers Linie ("Round
the world string service") or BBC Chartering. Consequently these vessels also need to have the
capabilities to maintain a schedule and therefore are designed with high maximum speeds (between
16-19 kts) and a surplus in power to be able to keep their schedule. A liner service with General cargo
ships offers transport services which did not exist and which often would have required chartering an
entire (smaller and slower) vessel. It thus substantially improves transportation efficiency considering
emissions.
Figure 10 Rickmers Superflex, example of a fast General cargo ship with a combined load of
project cargo and containers [Courtesy to Rickmers Group].
Numerous programs have been started, amongst others by the European Committee, to shift cargo
from road transport to ships to reduce road congestion and its attendant pollution. For example, the
14
Marco Polo programme, Motorways of the Seas, etc. Many of the initiatives developed within these
programs require a high speed in order to be able to compete with road transport. Substantially
limiting the speed of Short Sea General cargo ships, will seriously limit the future possibilities of a
modal shift from road to water.
With high minimum operational speeds up to 19 knots transport jobs can be carried out in a 30%
shorter time span in comparison to normal General cargo ships with a speed of 12 kts. Even when
transporting the cargo at a lower speed would be possible, to make the same number of trips on a
yearly basis and provide the same service level, for example with respect to the number of port calls,
would simply require more ships. Building and operating a higher number of (slow) ships would
increase the overall Greenhouse Gas emission and therefore contradicts with the aim of the EEDI
regulations. Furthermore, when general cargo ships with the capability of short delivery times,
because of their high minimum operational speed, are no longer available in the market, a modal shift
to other transport types (road/air) is to be expected. For some cargos the longer transport times of
“slow” General cargo ships are not acceptable when an alternative by road or air is available. A modal
shift to road or air transport, especially when taking cargo away from Short Sea Shipping will increase
the overall GHG emissions, and often emissions in the densely populated areas and could further
increase road congestion.
It is expected that in its current form the EEDI regulations could lead to a reduction of installed engine
powers. As a result the service speed of General cargo ships with high minimum operation speeds will
decrease, even when the designs are hydrodynamically or otherwise technically optimized. This
makes the replacement of old and less environmentally friendly fast General cargo ships impractical,
and as a result the effectiveness of Short Sea Shipping and shipping in general is impeded. There are
a number of solutions that make it possible to continue the operation of small General cargo ships with
high minimum operational speeds, within the current set up of the EEDI regulatory frame work.
However these solutions are not the most safe, environmentally friendly and sustainable solutions,
even though they would comply with the EEDI regulations:
- Continue operations with old, less environmentally vessels (not only high CO2 emissions, also
high NOx and SOx emissiosn), as existing vessels do not have to meet the EEDI
requirements;
- Use vessels “exclusively designed for the carriage of containers”, which therefore have to
comply with the higher EEDI reference line for containers vessels according to IMO definition,
as General cargo ships with high minimum operational speed. However as these vessels have
not been optimized for general cargos, for example regarding tank top loads, hatch cover
types, etc. the operations might be less efficient and the chance of structural damages that
might impair the safety of the vessel, its crew and the environment increases [6];
- Classify a General cargo ship with high minimum operational speed below 10.000 dwt as “bulk
carrier” . According to IMO bulk carriers are vessels intended primarily to carry dry cargo in
bulk, therefore the definition leaves room for other kind of operations. Small General cargo
15
ships “classified” as bulk carrier, below 10000 dwt don’t have to comply with the EEDI
requirements, as for bulk carriers below 10000 dwt. no Required EEDI needs to be calculated.
As a consequence it could be required that these vessels meet the bulk carrier rules of the
classification societies in order to be categorized as bulk carrier, which amongst others would
mean the need to comply with the Common Structural Rules for bulk carriers (L> 90, Cb >0.6).
This is expected to result in relatively “heavy” General cargo ships. As a results, these vessels
will than operate with a lower deadweight, i.e. with less benefits for society and with a higher
than necessary CO2 emission while meeting the EEDI regulations;
- For the time being, categorize a General cargo ship with high minimum operational speed as
“Heavy load carrier” or “open hatch carrier”, both for which no EEDIRequired need to be
calculated. In fact, about all of the modern General cargo ship designs could be categorised
within these two groups. This leads to the exclusion of a large group of General cargo ships
from the EEDI regulations and does not result in a decrease of CO2 emissions. Furthermore
not having a EEDI score might also become problematic as some ship-owners foresee that
the “EEDI score” will become a “commercial measure” to rate various ships and that it will
become the basis for port authorities to define harbour dues in the future. Thus besides the
fact that exclusion of a large group of vessels does not help to reduce CO2 emissions, it might
also propose additional problems for governments and port authorities in the calculation of
pilotage, harbour and other dues.
It is thus shown that the ability to operate at higher than average reference speed is justified for a
special group of General cargo ship and that limiting the installed power of General cargo ships, to
meet the EEDI requirements, might have counter-productive effect, amongst others due to possible
modal shifts to road transport. However to justify including an alternative measure to reduce the wide
scatter, it also needs to be shown that:
- The high EEDI values of vessels sailing at high speeds are actually the results of a high speed
and not of other factors that might affect the EEDI value, which will be shown in paragraph
3.2.
- The ships designed for high speeds that currently not comply cannot be further
hydrodynamically optimized and that new technological developments that become available
will not sufficiently reduce the EEDI Attained, see 3.3;
- That "high speed" is a “verifiable” ship characteristic, shown in 3.4;
- It is possible to develop a correction factor that is clear, transparent, comprehensive and does
not create perverse incentives. See 3.5;
16
3.2 Systematic assessment of the Attained EEDI for fast General
Cargo Vessels
In order for a correction factor on speed to be justified for General cargo ships designed for high
minimum operational speed it needs to be shown that the high EEDI values of these vessels is
actually caused by their high minimum service speed and not by other aspects that could lead to a
high EEDI.
For the vessels in the database as used for this study, a comparison is made between the main
characteristics of the vessels that do not comply and a number of vessels which have no “special
features” that do comply, within the same deadweight range. For an overview of the comparison, see
Table 2 and Table 3.
Table 2 Comparison of vessels within deadweight range 3000 – 4000 dwt
C1 C2 C3 C4 A1 A2 A3
EEDI [gCO2/(mt*nm)] 11,3 12,7 13,1 18,2 31,2 29,3 24,8
Fn 100,0% 99,2% 97,9% 105,7% 155,2% 155,2% 151,7%
DWT [mt] 3710,8 3365,0 3173,0 3433,0 3335,0 3549,0 3450,0
VRef 100,0% 98,5% 97,9% 105,7% 155,2% 155,2% 162,9%
Lpp 100,0% 98,6% 100,0% 100,0% 100,0% 100,0% 115,2%
Bm 100,0% 93,6% 93,6% 89,1% 118,7% 118,7% 116,9%
Dm 100,0% 89,4% 85,1% 92,9% 87,6% 87,6% 105,0%
Tsummer 100,0% 100,9% 94,9% 105,1% 100,3% 100,6% 118,7%
CB [-] 0,86 0,85 0,83 0,84 0,74 0,74 0,60
Gross Tonnage 100,0% 80,6% 90,4% 78,6% 102,8% 102,2% 117,2%
Lightweight 100,0% 99,3% 87,9% 91,7% 144,5% 126,2% 174,3%
Displacement summer draught 100,0% 92,8% 86,1% 92,3% 103,0% 103,0% 112,5%
M.C.R.ME 100,0% 100,1% 100,0% 151,5% 437,9% 437,9% 400,3%
M.C.R.ME / Displacement [kW/mt] 0,15 0,17 0,18 0,25 0,65 0,65 0,55
Lightship / (Lpp x Bm x Dm) [mt/m3] 0,15 0,18 0,16 0,16 0,20 0,18 0,18
Number of cranes 0 0 0 0 2 0 2
In operation from 2011 1995 2009 1997 1999 1997 2012
17
Table 3 Comparison of vessels within deadweight range 4000 – 5000 dwt
C5 C6 C7 C8 A4
EEDI [gCO2/(mt*nm)] 16,4 16,1 14,5 14,4 24,3
Fn 100,0% 99,1% 114,1% 114,2% 121,6%
DWT [mt] 4530,0 4530,0 4510,0 4522,0 4533,0
VRef 100,0% 99,1% 114,1% 114,1% 126,3%
Lpp 100,0% 100,0% 100,0% 99,8% 107,7%
Bm 100,0% 100,0% 102,9% 102,9% 113,2%
Dm 100,0% 100,0% 109,8% 102,8% 123,8%
Tsummer 100,0% 100,0% 102,1% 102,0% 99,5%
CB [-] 0,85 0,85 0,82 0,82 0,78
Gross Tonnage 100,0% 100,0% 99,5% 100,0% 129,1%
Lightweight 100,0% 100,0% 105,4% 103,8% 147,6%
Displacement summer draught 100,0% 100,0% 100,9% 100,7% 111,1%
M.C.R.ME 100,0% 100,0% 100,0% 100,0% 182,2%
M.C.R.ME / Displacement [kW/mt] 0,30 0,30 0,30 0,30 0,50
Lightship / (Lpp x Bm x Dm) [mt/m3] 0,16 0,16 0,15 0,16 0,16
Number of cranes 0 0 0 0 0
In operation from 2002 2002 2007 2002 2007
The comparisons make clear that the vessels A1, A2, A3 and A4 have much higher reference speeds,
on average 50% higher than the baseline vessels C1 till C8, as was to be expected. However they
also have a much higher lightweight, and therefore either have a lower deadweight with a comparable
displacement, or have a higher displacement for the same deadweight.
There are several reasons for this higher lightweight of the vessels sailing at high speed:
- Two out of the four faster vessels are equipped with cranes, which increased the lightweight
due to the weight of the cranes and the additional steel weight of the crane’s foundation;
- All four of the vessels with a high operational speed have a larger width than the “slow”
vessels C1-C8. At first instance this seems to be counter intuitive, as this results in a smaller
Length/width ratio, which is unfavourable from a resistance point of view, although a higher
width does help to lower the block coefficient when the displacement is kept the same.
However as most of the faster General cargo ships are also designed to carry containers, the
additional width compared to the “slower” relatives is probably required to provide sufficient
stability when containers are loaded on deck. An increase of main dimensions (Length, Width)
means that the vessel is simply “larger” compared to the ships C1-C8, which increases the
steel weight.
- Two out of four of the “fast” vessels have a larger length, besides having a larger width, which
naturally increases the steel weight, as it makes the ship bigger. A larger length and width by
a comparable displacement reduces the Cb, which is favourable from a resistance point of
view;
- Two of the four vessels with a high minimum operational speed have a high Gross Tonnage
compared to the “slow” vessels, which means that they have a high “enclosed volume”
compared to the other vessels. This indicates a larger hold volume compared to the “slow”
18
vessels. These vessels with a high minimum operational speed are clear “volume carriers”
instead of “weight carriers”, which is also showed by the larger depth of the vessels. The
larger depth does not necessarily result in “heavier” vessels, as a lower L/D ratio can be
favourable from a longitudinal strength point of view.
To check whether equipping the vessels with cranes could result in the high EEDI values, a calculation
is made according to the design of ship A3, but without cranes, which results in a deadweight increase
of about 280 ton. With this increased deadweight, the EEDIAttained of ship A3 would become 23.0.
Lower than compared to the value of ship A3, but still substantially higher than its Required EEDI.
As the vessels are compared within a deadweight range, the high lightweight of the “fast” vessels did
not results in a lower deadweight, but the higher lightweight results in a higher displacement.
Therefore the “deadweight part” of the denominator is thus comparable to that of the slower vessels
and it can be concluded that the high EEDIAttained values of the faster vessels is caused by their high
maximum speed.
3.3 Analysis of the degree of optimization of General cargo ships for
EEDI
A correction factor for speed is further considered to be justified as all of the vessels sailing at high
minimum operational speed are optimized for high speed operations: low resistance and as low as
possible fuel consumption. Amongst others this is expressed by a low block coefficient, or a low
prismatic coefficient, and an optimized propulsion system, for example regarding propeller diameter.
The block coefficient (Cb) is a measure of the fullness of the hull and affects the resistance of the ship.
Ships with low Cb commonly have a lower resistance than ships with a high Cb. To limit the amount of
power required for propulsion at high speeds, and therefore minimize the CO2 emissions, a low Cb is
required.
TBLC
mpp
b
In which:
Cb = Block coëfficient [-]
= Displacement moulded [m3]
Lpp = Length between perpendiculars [m]
Bm = Beam moulded [m]
T = Draught at summer loadline [m]
19
The prismatic coefficient is a rough measure indicating how quickly the sectional area of a ship
changes. In general a lower prismatic coefficient, results in a lower resistance and thus in lower
engine powers. Therefore it provides an indication whether a ship is designed for high speeds or not.
ppm
pLA
C
In which:
Lpp = Length between perpendiculars [m]
= Displacement [m3]
Am = Area of the midship section [m2]
The faster vessels in our database are optimized for “high speed” operations, as the block and
prismatic coefficients are substantially lower than those of slower vessels within the same deadweight
range. See Figure 11 and Figure 12 in which the block coefficient and prismatic coefficient are shown.
C1
C13C6C2
C3C10
C14
C4 C5
C12
C9
C8
C7
C11B4
B3
B1
B2
A1A2
A3
A4
A5
0,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,80
0,90
1,00
0 2000 4000 6000 8000 10000 12000 14000 16000
DWT [mt]
Cb [
-]
Figure 11 Block coefficient versus Deadweight
20
C1
C13C6C2C3
C10
C14
C4 C5
C12
C9
C8
C7
C11
B4B3
B1
B2
A1
A2
A3
A4
A5
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0,9
1
0 2000 4000 6000 8000 10000 12000 14000 16000
DWT [mt]
Cp [
-]
Figure 12 Prismatic coefficient versus Deadweight
A further optimization for high speeds, for example by further reducing the Cb or Cp, as for example is
proposed by Kristensen [7] to facilitate compliance with the EEDI requirements for bulk carriers, is not
feasible for General cargo ships considering the operational boundaries in the lower deadweight
range. For example to reduce the Cb of ship A3 to 0.45, while keeping the same displacement, width
and draft, its length needs to increase with over 40 percent, which is impractical considering the
dimensions of the harbours Short Sea Cargo Vessels have to call. Length, width and draught
restrictions are a serious restriction for the hydro dynamical optimization of General cargo ships, which
effect is not to be underestimated. There are many more main dimension restrictions for small General
cargo ships as for large bulk carriers, or tankers, as the number of ports these General cargo ships
have to be able to reach is far larger. Well-known dimension restrictions for a General cargo ship,
related to a port, canal, lock, or sailing area are for example:
Trollhättan canal; Bmax 13.4 m Lmax 88m Tmax 5.4 m
Saimaa canal; Bmax 12.2 m Lmax 82 m Tmax 4.35 m
St. Lawrence seaway Bmax 23.8 m Lmax 225.6 m Tmax 8.1 m
Albert canal Bmax 12.5 m Lmax 134 m Tmax 3.4 m.
To further check the degree of hydrodynamical optimization, the combination of Vref, displacement,
length, width, draft and power required to reach Vref of the various vessels is assessed by MARIN.
21
This analysis shows that for most of the fast vessels there is little room for improvement, meaning that
considering their main dimensions, Vref and displacement, they are optimized from a resistance point
of view.
C14
A3A4
B1
A2
A1
A5B2
5
10
15
20
25
30
35
0 5000 10000 15000 20000 25000
EED
I
DWT
EEDI with Ice corr.
unknown
0-5% potential
5-20% potential
20+% potential
Baseline
Phase 2
Figure 13 Design improvement potential
The vessels in the database were compared to the MARIN database in order to qualify the powering
performance of the ships. For each ship the Vref from the database was compared to a set of 10
similar vessels from the MARIN database and where classed according to their ranking among the 10
ships. Three classes were used, depending on the amount of hydrodynamical improvement potential,
expressed as a percentage of the power at constant speed: 0-5% potential, 5-20% potential, > 20%
potential.
The 10 comparable ships for each general cargo design were automatically selected based on the
ratios of main dimensions like prismatic coefficient and slenderness ratio. Before comparison all 10
ships are scaled to the same main dimensions as the general cargo design, using a modified Holtrop
& Mennen method. In this way effects of main dimensions and displacement are not included in the
qualification. The Holtrop & Mennen method is a statistical power prediction method based on
regression analysis of random model data.
22
Results of the benchmark show that only for 2 of the vessels that do not comply with the baseline a
high improvement potential seems to be present. However a part of this potential could be caused by
inaccurate determination of Vref, which is very sensitive for differences between trial conditions and
model tests (e.g. regarding draft, sub-optimal working of the bulbous bow during trials, etc), which
could strongly affect the calculation of Vref at summer draught based on the trial results. A slightly
higher actual Vref drastically reduces the estimated improvement potential.
Another option to reduce the EEDIAttained, besides hull form optimization, would be to implement
(alternative) technologies to reduce CO2 emissions, such as: use of advance low resistance coatings,
optimize the propulsion system with for example contra rotating propellers, apply waste heat recovery
systems, or switch to LNG as fuel. For more examples of alternative technologies, see amongst others
[8]. Most of these technologies reduce the required installed power with a couple percents. Such a
reduction will decrease the EEDIAttained, but will not sufficiently lower the EEDIAttained to the EEDIRequired
values. Switching to LNG does substantially lower the EEDIAttained, but also not sufficient to reach the
required values. For example when vessel A3 is recalculated as if it was operating on LNG, the
EEDIAttained would decrease to 21.9, still above the EEDIRequired.
3.4 Unambiguous definition of speed for General cargo ships
For an unambiguous and transparent correction factor to reduce the wide scatter due to minimum
operational speed differences between General cargo ships, a clear and unambiguous definition of
speed for General cargo ships is required, which considers the relativity of speed in relation to the
main dimensions and its deadweight.
A common choice in ship design is to use the Froude number as a parameter to define speed in
relation to the vessels dimensions, i.e. its length.
Lg
VFn
[-]
In which:
V Speed [m/s]
g Gravitational acceleration [m/s2]
L Length [m]
The vessels from this study for which the EEDIAttained lies substantially above the reference line (A1,
A2, A3 and A5) clearly have a higher Fn than the other vessels as can be seen in Figure 13. However
A4 has a Froude number which is much closer to Froude numbers of vessels that do meet the EEDI
requirements. Not accounting for its deadweight (or displacement) in relation to its length and speed
23
could explain why a ship with a relatively low Froude number could has difficulties meeting the
requirements.
C11
C7
C8
C9
C12
C5
C4
C14
C10
C3
C2
C6
C13C1
B2
B1B3
B4
A5
A4
A3A2
A1
0,00
0,05
0,10
0,15
0,20
0,25
0,30
0 2000 4000 6000 8000 10000 12000 14000 16000
DWT [mt]
Fn[-
]
Figure 14 Froude number versus Deadweight
Therefore simply using the Froude Number to define the speed of a General cargo ship, although easy
to use and to administer, does not seem to provide the desired indubitable distinction.
To account for the relation between speed and displacement, the Volumetric Froude Number (Fn) is
commonly used. The Fn relates the speed of a ship with its dimensions, independent of its Length,
Width and Draft. Fn is defined as:
3
1
g
VFn
ref
In which:
Vref Reference speed [m/s]
g Gravitational acceleration [m/s2]
Displacement moulded [m3]
24
All of the vessels with a high minimum operational speed in the database of our study have a Fn that
is substantially higher than the other vessels in the database, as shown in Figure 14.
C1
C13C6
C2
C3
C10
C14
C4
C5
C12
C9
C8
C7
C11
B4
B3B1
B2
A1
A2
A3
A4
A5
0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0 2000 4000 6000 8000 10000 12000 14000 16000
DWT [mt]
Fv
ol[
-]
Figure 15 Volumetric Froude number versus Deadweight
The approach to use the Fn to distinguish between “fast” and “slow” vessels is similar to the
approach as used by the IMO in the High Speed Craft Code to define “high speed”, except for the
value of the “constant” in the formula. IMO defines “high speed” craft as: “A craft capable of maximum
speed in m/s, equal to or exceeding 3.7 1/6
, in which = volume at design waterline”.
In a further refinement of this approach, also the block coefficient is taken into account. By taking into
account the block coefficient, the Length, Width and Draft of the vessel in relation to its displacement
(and therefore its deadweight) are considered as well, we propose to do so with the use of a block
coefficient - volumetric Froude number coefficient, denoted as fCb,Fn.
c
b
bCFna FnCb,f
In which:
a Constant [-]
b Constant [-]
c Constant [-]
Fn Volumetric Froude number [-]
25
Cb Block coefficient [-]
The constants in this formula have been defined by MARIN, based on their database of General cargo
ships up to 20.000 dwt., and come from the regression line as shown in Figure 16. This figure shows
the relation between EEDIAttained/EEDIRequired versus the combination of the volumetric Froude number
and the main dimensions of a ship through the Cb.
By multiple selective regression analysis using several dimensionless hull form and speed
parameters, it was found that the two parameters Fn (volumetric Froude number) and Cb (block
coefficient) explained a large part of the variation in EEDIAttained/EEDIRequired, with a Fn to the power
2.3 and a Cb to the power 0.3. :
3.03.2
FnCb,f bCFna
Plotting the Attained EEDI over the Required EEDI from the phase 0 baseline is versus the Froude
number and block coefficient product with the given powers above, for the vessels in the General
cargo ships database, gives the following result:
0.174
A2
A1
A5A4A3
y = 5.737x
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
0 0.05 0.1 0.15 0.2 0.25 0.3
EED
IAtt
ain
ed
/EED
IRe
qu
ire
d (
-)
Fnv^2.3Cb^0.3 (-)
Figure 16 Attained EEDI/Required EEDI versus the combination of the volumetric Froude
number and block coefficient
The plot shows also a reasonable correlation for the EEDI ratios in this general cargo database. The
constant of 5.737 determined in the least squares linear trend line can be considered as an average
value, with roughly an equal number of ships above and below the line.
The analysis thus shows that with these variables the relation between dimensions, volume, speed
and Attained EEDI can be fairly accurately described. This provides a solid basis for the definition of a
correction factor to account for the speed differences of General cargo ships.
26
3.5 Correction factor to account for speed differences between General
cargo ships
It is proposed to account for the variation in speed of General cargo ships through a correction factor
on power. The previous section has shown that it is possible to define a relation between the
dimensions, volume and EEDI values in a transparent and well defined way. We propose to define this
correction factor in such a way that vessels with a low and normal speed for their displacement and
main dimensions are not entitled to a correction on speed.
To improve the clarity of the Guidelines and regulations, we propose to limit the number of correction
factors and therefore extend the definition of the existing correction factor on power7, fj, to include the
power correction factor to account for the variety in minimum operational speed of General Cargo
ships below 20.000 dwt.
The formula of the regression line in Figure 16 provides a relation between EEDIAttained/EEDIRequired and
the volumetric Froude number – block coefficient parameter, Fn2.3
*Cb0.3
on the x-axis. This relation
can be written as:
3.03.2
Re
737.5 b
quired
Attained CFnEEDI
EEDI
See again figure 15. The ships indicated by A1 to A5 all are, as has been shown earlier, ships which
are sailing at relatively high speed. These ships have the highest ratio between Attained EEDI and
Required EEDI. Subsequently the low speed ships have the lowest ratio between Attained EEDI and
Required EEDI. So, roughly the right half of the selection of ships are relatively fast sailing ships and
the left half are slow sailing ships. As shown, applying a correction factor for speed would only be
reasonable for ships that sail fast for their dimensions and displacement. So a threshold value needs
to be defined from which the correction should account. Moreover, the correction is never larger than
the difference between the value of the trend line at the particular x-value and EEDIAttained/EEDIRequired
is 1. We further propose to correct the vessels in such a way, that ships which are on the average line
and for which the x-value is larger than 0.174 are corrected to a ratio between Attained EEDI and
Required EEDI of 1 and therefore could comply with the regulations.
3.03.2
Re
737.5 b
quired
Attained CFnEEDI
EEDI
7 See MEPC63, Annex 1, 2.8
27
quiredAttained
b
EEDIEEDICFn
Re3.03.2
174.0
We further propose that the vessels on the average line, with an 3.03.2
bCFn larger than 0.174
should be corrected to a ratio of EEDIAttained divided by EEDIRequired of 1. Vessels above the average
line thus do no receive sufficient correction to meet the requirement with only the correction on speed.
Consequently the correction factor to account for the differences in operational profile for General
cargo ships below 20.000 dwt, denoted as fj, becomes:
3.03.2
174.0
b
jCFn
f
In which:
Fn= volumetric Froude Number as defined in section 3.4.
Cb= block coefficient as defined in section 3.4.
In case fj is equal or larger than 1, a fj of 1 should be applied.
Please note that left of this x value of 0.174 there are also ships that do not comply with the EEDI
requirements, however the cause of this non-compliance is likely other than the speed as these are
vessels with a below average or average speed.
The formula to calculate the Attained EEDI remains:
refwci
ME
neff
i
FMEieffieffAEFAE
n
j
nPTI
i
neff
i
iAEeffieffiPTIjAEFAEAE
nME
i
iMEiFMEiME
n
j
j
VfCapacityff
SFCCPfSFCCPfPfSFCCPSFCCPf
EEDIAtt
1
)()(
1 1 1
)()()(
1
)()()(
1
.
The effect of the factor fj is further shown through a number of example calculations in the following
section.
Example calculations:
In chapter 3.4 it was shown that the vessels A1, A2, A3, A4 and A5 are all to be considered as vessels
designed for high operational speeds. Calculating fj for these vessels shows that for all of them fj is
smaller than 1, see Table 4, and therefore the correction factor fj is to be applied within the attained
EEDI calculation.
28
Table 4 Influence of the factor fj on the Attained EEDI value
A1 A2 A3 A4 A5
Attained EEDI (uncorrected) [gCO2/(mt*nm] 31.2 29.3 24.8 24.3 19.7
Cb [-] 0.74 0.74 0.60 0.78 0.66
Fn [-] 0.57 0.57 0.59 0.52 0.58
fj [-] 0.68 0.68 0.67 0.85 0.69
Attained EEDI (corrected) [gCO2/(mt*nm)] 21.2 19.9 16.6 20.7 13.6
Required EEDI [gCO2/(mt*nm)] 18.6 18.4 18.5 17.4 14.9
Including the factor fj reduces the attained EEDI, however not all of the vessels than directly comply
with the regulations for phase 1 and 2, see for example vessel A2 and A3. Thus, the introduction of
this correction factor does not take away the need for technological developments to further reduce
CO2 emissions, in case ships according to these designs are to be built in the future.
It is further checked whether this correction factor does not provide any “perverse incentives” by
facilitating compliance with the regulations for fast vessels which are not optimized for high speed
operations and thus have a relatively high Cb. This is done through a number of calculations in which
the speed of high Cb vessels is increased until fj becomes comparable to the fj values of the fast
vessels.
Consider for example vessel C2. This vessel has a reference speed of about 9.1 knots and a Cb of
0.853, clearly not optimized for high speeds. For high speed operations with such a full vessel very
high propulsion powers are required. For example to increase the speed to 11 knots requires an
installed power which is already about 2.4 times higher. In that case f j remains higher than 1. For a fj
equal or smaller than 1, the speed should increase to 11.8 knots. For fj values comparable to the
vessels A1-A5, around 0.68, a speed of 14 knots is required. In that case the required propulsion
power is 5456 kW and even though the correction factor for speed can be applied, there is such a big
difference between the required EEDI and the attained EEDI that also after applying the correction
factor, the vessel will not comply. See Table 5.
Table 5 Various calculations of the Attained EEDI
C2 C2 - Increased
speed
C2 - fj = 1 C2 - fj = 0.68
Cb [-] 0.853 0.853 0.853 0.853
Displacement [m3] 4415 4415 4415 4415
Reference speed [knots] 9.1 11 11.8 14
Installed power [kW] 750 1821 2440 5456
fj [-] 1.79 1.15 1 0.68
Attained EEDI (corrected) [gCO2/(mt*knots)] 12.4 24.9 31.4 59.3
In general the required propulsion power increases very rapidly (with the third power or higher) when
ships which are not optimized for high speeds are to be operated on a high speed. Therefore even
when the factor fj is applied, the reduction will be insufficient to let these vessels comply with the
29
requirements, as they are placed far above the “average” as represented by the regression line in
Figure 16.
See Figure 24 for the influence of the correction factor fj for minimum operational speed on the scatter
and R2.
3.6 Evaluation of correction factor against IMO requirements
In order for a correction factor to be considered as a reasonable correction factor and eventually to be
accepted, the proposal for the new correction factor needs to comply with the requirements for a
correction factor as defined by IMO as shown in chapter 2. In this paragraph, it is shown that the
proposed correction factor to account for the differences in operational profile complies with the
requirements.
A Verifiable ship characteristics and application;
The proposed correction factor is based on the volumetric Froude number and the block coefficient
which both are to be defined based on parameters which are known during the design phase and
which are clearly verifiable. A number of these parameters is also used within the formula to calculate
the attained EEDI, or within the definition of other correction factors.
B Need for a correction factor;
The need for a correction factor is shown, by showing that there is a need for fast General cargo
ships, and that optimized fast General cargo ships are not able to meet the EEDI regulations. It was
further shown that not including a correction factor to account for the differences in the operational
profile could lead to increased CO2 emissions, amongst others due to a modal shift to road transport.
C Best addressed with a ship-specific solution;
The proposed correction factor is based on ship specific characteristics and therefore provides a ship-
specific solution.
D Comprehensive, transparent analysis to develop correction factors;
The presented analysis in this chapter is believed to be a sufficiently comprehensive and transparent
analysis to act as a basis for the development of the proposed correction factor.
E Clear instructions for determining a correction factor;
For instructions to determine the correction factor, see section 3.5 which gives an overview of the
definition of the correction factor and an example calculation. Further instructions could be developed
if required.
30
F Does not create perverse incentives.
With a number of example calculations (one of them shown in section 3.5) it is examined that the
proposed correction factor does not create perverse incentives. Application of the correction factor will
not make it possible for non-optimized General cargo ships (i.e. full ships) to operate at high speeds
while meeting the EEDI requirements.
31
4 Effect of Cargo handling gear on EEDI for General cargo
ships < 20.000 dwt
A typical characteristic of General cargo ships is that these ships are designed to be versatile and
have to operate in a large number of ports, even when optimized for a specific trade. To enhance their
flexibility a considerable number of General cargo ships are equipped with cargo handling gear. Many
of the General cargo ships with cargo handling gear provide services to ports in which shore cranes
are not available, or when cranes are available, their capacities are insufficient to provide efficient
cargo handling services. Further, cargo handling gear is used to lift objects directly from the water onto
the ship’s deck, or into the hold, or to lift cargo from one ship to another.
General cargo ships equipped with cargo handling gear thus provide an additional benefit for society,
as they are able to quickly and safely load and unload heavy or outsized cargoes in area's and ports
lacking adequate equipment. Without General Cargo Ships equipped with cargo handling equipment,
all cargo first has to be transported by road or train to ports with the adequate equipment, before it
could be shipped overseas. Subsequently the same is true for the unloading part of the transport
chain. The increased “pre and post” transport would increase the overall CO2 emissions within the
transport chain, as most of it will be done by truck.
Several types of cargo handling gear are commonly used on board of General cargo ships:
Cranes, of various types:
o Hydraulic or ram type luffing cranes;
o Wire luffing cranes;
Side loaders;
Ro-Ro ramps.
For examples of cargo handling gear for General cargo ships, see Figure 17.
32
Figure 17 Various examples of cargo handling with use of loading equipment
Equipping a vessel with cargo handling gear reduces it deadweight, compared to vessels with the
same main dimensions and displacement, as the lightweight increases. Consequently the Attained
EEDI of these vessels will be higher as they have a lower deadweight. As a result the Attained EEDI
values show more scatter in comparison to groups of vessels where there is less variety in cargo
handling gear, such as bulk carriers or tankers. Cargo handling gear especially affects the Attained
EEDI of the smaller General cargo ships. For the smaller vessels installation of cargo handling gear
can result in a deadweight loss of about 10%.
An additional correction factor that considers the differences between General cargo ships in cargo
handling gear would reduce the wide scatter as found for small General cargo ships. It is proposed to
introduce a correction factor to account for cargo handling gear, consisting of correction factor to
account for cranes, side loaders and RoRo ramps. Other types of cargo handling gear could be added
in the future. This correction factor, fl, should correct the Capacity of the vessel, in analogy to the
correction of the Capacity as for example done through the Ice Class Correction factor.
RoRosideloadercranesl ffff
cranesf = 1 If no cranes are present.
sideloaderf = 1 If no sideloaders are present.
33
RoRof = 1 If no RoRo ramp is present.
It is proposed to include the correction factor fl as follows:
refwlci
ME
neff
i
FMEieffieffAEFAE
n
j
nPTI
i
neff
i
iAEeffieffiPTIjAEFAEAE
nME
i
iMEiFMEiME
n
j
j
VfCapacityfff
SFCCPfSFCCPfPfSFCCPSFCCPf
EEDIAtt
1
)()(
1 1 1
)()()(
1
)()()(
1
.
In the following sections the proposal for fl is further developed. A detailed proposal is made for the
correction factor to account for cranes, as cranes are the type of loading gear which is most frequently
applied. A simplified proposal is given to account for sideloaders and Ro-Ro ramps, which could be
further developed in a later stage.
4.1 Correction factor for cranes
Cranes are the most common cargo handling gear for small General cargo ships. Common types are
hydraulic cranes (ram luffing crane), up to 60 ton or wire luffing cranes which on General cargo ships <
20.000 dwt could go up to a capacity of more than 250 tons.
In Figure 18 it can be seen that a considerable amount of vessels in the database are equipped with
cranes.
A2
A1
0
5
10
15
20
25
30
35
0 5000 10000 15000 20000 25000
DWT
EE
DI
Figure 18 Blue dots represent ship without cranes, pink dots represent ships with cranes
34
A clear indication of the effect of cranes on the Attained EEDI of small General cargo ships can be
obtained by comparing ships "A1" and "A2" from Figure 18. These ships are identical, except for the
fact that ship A1 is equipped with two cranes, whereas A2 has no cranes, see Table 6. Clearly the
differences of the EEDI values are a direct result of differences in the deadweight, coming from the
differences in lightweight due to additional weight of the cranes, the pedestal, the crane columns and
the crane foundation in the ship’s side.
Table 6 Comparison of ship "A1" and ship "A2"
Ship A1 Ship A2
EEDI [gCO2/(mt*nm)] 31.2 29.3
Fn 100% 100%
DWT [mt] 3335 3549
VRef 100% 100%
Lpp 100% 100%
Bm 100% 100%
Dm 100% 100%
Tsummer 100% 100%
Gross Tonnage 100% 99%
Lightweight 100% 87%
Displacement summer
draught
100% 100%
M.C.R.ME 100% 100%
M.C.R.ME / Displacement 100% 100%
Lightship / (Lpp x Bm x Dm) 100% 87%
There are ships with cranes that comply with the current EEDI regulations and there are ships with
cranes that not comply with the current regulations. Thus a correction factor for loading gear does not
only affect the vessels above the reference line. Accounting for the effect of loading gear, reduces the
overall scatter, as the effect of differences in capacity are reduced.
It is proposed to correct the EEDI parameter Capacity with the additional weight of the cranes, the
columns, the pedestals and the additional steel for the foundation in the ship side. In that way, the
correction factor provides a “ship specific” solution to account for the actual additional weight.
Therefore in each case the additional weight of the cranes need to be calculated, so:
Capacity
Capacityf
CraneNo
cranes
In which:
Capacityno crane = the capacity of the vessel increased with the weigh of cranes;
Capacitycranes = the actual capacity of the vessel, as defined as “capacity” in the EEDI regulations.
35
4.1.1 Quantification of crane weights
For ships with cranes, the increase in lightweight is equal to the sum of all weights corresponding to
the components of the cranes. Cargo cranes mainly consist of the following parts: the crane, including
the jib and the crane house, a pedestal, a crane column and the crane foundation and for additional
equipment such as the necessary hydraulic power packs in the engine room.
The weight of a crane is related to the maximum allowable moment on the crane. The moment is the
product of the safe working load (SWL) and the reach at which this SWL can be applied. The rationale
is that the higher the moment on the crane, the 'stronger' the crane and its foundation should be.
However, other factors are of influence, for example the crane type, height of crane column, the depth
of the cargo hold and the width of the side tanks.
Based on the data of two large crane manufacturers the relation between the weights of a cranes and
its maximum allowable moment is defined. See Figure 19. A relatively high R2 has been found, which
indicates a fair relationship between the weight of a crane and the maximum allowable moment on the
crane.
For a number of vessels the actual weight increase due to the installation of cranes could be defined.
The weights as shown in the figure are the weight increase per crane, see again Figure 19 for the total
weight increase per crane (incl. pedestal, column and foundation) compared to the weight of the crane
(jib and crane house). A fair relationship is found for the total weight increase per crane as function of
the maximum allowable moment on the crane.
36
y = 0,0349x + 13,906
R2 = 0,8955
y = 0,0519x + 32,11
R2 = 0,6558
0
20
40
60
80
100
120
140
160
180
200
0 500 1000 1500 2000
SWL * Reach [ton*m]
Weig
ht
[mto
n]
Figure 19 Blue dots are the weights of the crane units, the orange dots are the sum of all crane-
related weights.
The analysis shows that the weight of the crane itself is a dominant factor within the total weight
increase due to cranes. For larger cranes the share of the crane weight slightly reduces, which is to be
expected as larger cranes will require more robust foundations, while for smaller cranes the “normal”
ship’s construction is sufficiently strong to take up the crane forces and moments. Furthermore, larger
cranes are commonly placed on larger vessels which have higher ship sides, and consequently the
crane foundation extends over a larger depth and therefore is increased in weight. In the proposal of
the correction factor for loading gear, the lightweight increase due to the installation of cranes is
further estimated with the regression formula as found for the vessels in the database. I.e.:
11.32Re0519.0 achSWLcranesatodueincreaseWeight
In which:
SWL Safe Working Load, as specified by crane manufacterer [mt]
Reach Reach at which the Safe Working Load can be applied [m]
4.1.2 Correction factor for Cranes
With the known relationship between the weight of the crane and the maximum allowable moment on
the crane, the correction factor can be determined. The number of cranes installed on board a ship
varies. As such, the correction factor should be the sum of the corrections to be applied for each crane
separately. Thus:
37
Capacity
Capacityf
CraneNo
cranes
Which can be rewritten as:
Capacity
achSWL
f
n
n
nn
cranes
1
11.32Re0519.0
1
In which:
SWL Safe Working Load, as specified by crane manufacturer [mt]
Reach Reach at which the Safe Working Load can be applied [m]
n Number of cranes [-]
In case there are no cranes, fcranes is 1.
This calculation of the factor fcranes is straightforward and easy to apply, which is further shown in the
following example:
Consider a General Cargo Ship equipped with two container cranes, each with a Safe Working Load
of 40 mt @ 21.5 meters. The capacity of the vessel based on the definition as given in the MEPC63
Guidelines is 4500 dwt. The calculation of the correction factor will be than as follows:
Capacity
fcranes
11.325.21400519.011.325.21400519.01
034.14500
488.1531
488.1531
Capacityf cranes
4.2 Correction factor for sideloaders and Ro-Ro ramps
The design of Sideloading systems and Ro-Ro ramps for General cargo ships are commonly ship-
specific solutions with a much lower degree of standardisation as found for cranes. Sideloaders are
often applied on board ships where cargo is loaded piece by piece and where the cargo is to be
placed in position by means of for example forklifts. A typical example of a cargo type loaded by
means of sideloaders are paper reels. See Figure 17. Sideloaders normally consist of side doors
enabling cargo to be transported in and out of the ship and a lift enabling the cargo to be transported
to the designated deck. Key benefits of side loading systems are amongst others: low damage rates,
38
high degree of independence from port facilities and high loading capacities. Safe Working Loads
commonly vary between 4 to 20 tonnes, with an outreach of about 2 m. Ro-Ro ramps are not often
applied on General Cargo Ships.
Ro-Ro ramps are used on board of General cargo ships with a high degree of flexibility, which often
are capable of carrying containers, general cargos, naturally Ro-Ro cargos and sometimes even
passengers. Due to their capability to carry a combination of cargo types, they are not categorised as
“Containership”, or “Ro-Ro vessel” but as “General cargo ship”.
Sideloaders as well as Ro-Ro ramps result in an increased lightweight, because of the additional
equipment that needs to be installed (elevators, ramps, hydraulics, etc.) and reinforcements in the
construction that are required due to the large openings in the ship’s hull. We foresee two possible
ways to account for the additional lightweight of a ship due to sideloaders and/or Ro-Ro ramps:
Define the weight increase in a way which is analogous to the proposal as made for the
increase in lightweight due to e cranes. Thus define the weight increase based on a statistical
analysis of component weights and overall weight increases.
By direct calculation:
Define the increase of lightweight based on the actual weight of the components as stated on
the dimensional drawings and specifications of the manufacturer of the Side loader and RoRo
ramp. And, define the weight increase of the hull reinforcements by comparing the
constructional design of the vessel with the constructional design of a similar vessel without
RoRo ramps or sideloaders, in analogy with the methodology as proposed for the correction
factor for voluntary structural enhancements.
With both methods the weight of the vessel with and without the loading gear can be calculated,
resulting in:
Capacity
Capacityf
ssideloaderNo
sideloader and Capacity
Capacityf
RoRoNo
RoRo
Considering the largely ship specific designs of these two types of loading gear, it is proposed to
define the calculation of the correction factor fsideloader and fRoRo based on the direct calculation method.
See Figure 26 for the influence of the correction factor fl on the scatter and R2.
4.3 Evaluation of correction factor against IMO Requirements
In order for a correction factor to be considered as a reasonable correction factor and eventually to be
accepted, the proposal for the new correction factor needs to comply with the requirements for a
correction factor as defined by IMO. In this paragraph, it will be shown for each requirement that the
proposal for the new correction factor complies with the requirement.
39
A Verifiable ship characteristics and application;
The fact that loading equipment is present can be easily visually verified. The parameters used to
calculate the effect of loading gear on the lightship are also verifiable as they are stated on the
drawings and specification of the equipment. Any effects on the hull construction to be shown by direct
calculations is verifiable by comparing the constructional design of a vessel with and without loading
gear.
B Need for a correction factor;
The need for a correction factor for loading equipment is demonstrated by showing the difference in
attained EEDI values for otherwise identical vessels. Further not accounting for loading gear could
result in a modal shift as some ports simply lack the right equipment to efficiently load and unload
certain cargos.
C Best addressed with a ship-specific solution;
The best way to correct the Attained EEDI value is by means of a correction factor. The proposed
formula for the correction factor for cranes is based on the Safe Working Load and the Reach at which
this SWL can be applied, which is specific per crane and thus per ship. A similar method can be
developed for other loading equipment, such as sideloaders and RoRo ramps. Furthermore, the total
increase of lightweight is the sum of the weights of all loading equipment. However, if the method of
calculating the Attained EEDI by means of correction factors is not adequate, the possibility of
calculating the increased weight by means of the construction plans exists.
D Comprehensive, transparent analysis to develop correction factors;
The analysis performed for the determination of the relationship between the maximum applicable
moment on the crane, defined by the product of Safe Working Load and the Reach, and the total
weight increase of lightweight due to cranes has been presented in this chapter and is believed to be
sufficiently comprehensive and transparent. For other types of loading equipment to correction factors
could be further developed in a later stage.
E Clear instructions for determining a correction factor;
The formula for calculating the correction factor is presented in paragraph 4.1.2 together with a
calculation example providing clear instructions.
F Does not create perverse incentives.
The correction factor is not expected to create perverse incentives, as the factor can only be applied
for vessels which actually have loading gear installed. Furthermore only the actual additional
lightweight is accounted for.
40
5 Effect of additional class notations on scatter of Attained
EEDI values
Many small General cargo ships have additional class notations8 besides their “main” class notation as
represented by the class symbol and the construction mark. Additional class notations that are
frequently used are for example:
Strengthened for discharge with grabs:
For the class notation "Strengthened for discharge with grabs" structural enhancements are
applied on the tanktop and lower parts of the inner hold plating. As a result there is less
damage when the ships are discharged by means of a grab loader.
Strengthened bottom for loading/unloading aground:
The class notation "Strengthened bottom for loading/unloading aground" is often applied on
ships intended for operation in shallow drafts. The enhancement of the bottom plating allows
the ship to be in contact with the ground without damaging the bottom.
Strengthened for heavy cargoes:
The class notation "Strengthened for heavy cargoes" is frequently applied on General Cargo
Ships. This enhancement of the tanktop is necessary to withstand the high loads due to heavy
cargoes.
Strengthened for non-homogeneous loads:
The class notation "Strengthened for non-homogeneous loads" is applicable to a ship which
has been designed in such a way that the cargo spaces may be loaded non-homogeneously.
For example one hold can be fully loaded while the other is empty. The ship's construction is
strengthened accordingly to be able to withstand the high bending moments.
Strengthened to resist collision impacts:
Ships of which the side structures are specially strengthened in order to resist collision
impacts, may be assigned the notation "Strengthened to resist collision impacts".
Strengthened for loading operations with wheeled vehicles
The voluntary structural enhancement due to If cargo is handled by means of wheeled
vehicles, the deck and supporting structure are to be designed on the basis of the maximum
loading to which they may be subjected in service. If the structure is strengthened accordingly,
than the ship gets the notation "Strengthened for loading operations with wheeled vehicles".
In contrast with the installed loading equipment aboard a ship, the structural enhancements due to the
additional class notations are usually not visible at first sight. However, these enhancements do have
a (considerable) impact on the lightweight, and consequently on the Attained EEDI. Although these
enhancements could be considered as being 'voluntary' enhancements, bearing in mind that it is not
8 Also commonly called “structural class notations”. Bureau Veritas uses the term “additional class
notations”, within most IMO documents reference is made to “structural class notations”.
41
required by any authority to apply the additional class notations, in practice ships intended to transport
certain types of cargo or to sail in certain area's cannot avoid these structural notations, without putting
the safety of the vessel and the environment at risk.
When for example the bottom is no longer strengthened for loading aground, because a ship-owner
wants to minimize its EEDI value by maximizing the deadweight of the vessel, but the ship does end
up in a situation that it is loading or unloading aground, there is an increased chance of damaging the
hull. Damage to the double bottom could amongst others lead to oil spills. Transferring all cargo to
deepsea ports, so no “loading aground” is required, requires more “pre and post” transport, which is
usually done by truck, and increases the overall CO2 emission of the transport chain.
When, due to the EEDI requirements, it would no longer be feasible to design and build ships with an
strengthened tanktop for cargo discharge by grab, the consequences for the environment are
considerable. One possible consequence is a modal shift in cargo transport, i.e. if the cargo can no
longer be transported with General Cargo Ships, the cargo might be transported by means of trucks,
which will lead to a higher emissions over all. Another possible consequences mainly concern the
structural integrity of the ship. For example when the cargo is transported by means of General Cargo
Ships without a strengthened tanktop, the risk of damaging the cargo inner hold plating would increase
and might lead to fuel leakage into the cargo hold, contaminating the cargo leading to considerable
losses.
5.1 Correction factor for additional class notations
In Figure 20 and in Figure 21 the ships within the database of this study with respectively a "GRAB
discharge" notation and a "Loading/Unloading Aground" notation are indicated by means of the pink
dots. The blue dots are the ships without these notations. It can be observed that a considerable part
of the General Cargo Ships in the database have such class notations. Based on the detailed weight
estimates of a number of recently constructed ships, the impact of grab is estimated to be about 2
percent of the lightweight. The impact of the notation "Loading/Unloading aground" is estimated to be
about 3 percent of the lightweight.
Example 1:
Consider a ship with a "GRAB" notation with a Displacement of 15.000 ton and a Deadweight of
11.700 ton. The lightweight is 3300 ton, included with a strengthened tanktop weighing approximately
65 ton more than a non-strengthened tanktop. Compared to the Deadweight, the additional steel
weight is 0.6 percent of the Deadweight. In other words, the deadweight is decreased with 0.6 percent
and the Attained EEDI increases with 0.6 percent.
Example 2:
Consider a ship with a "Loading/Unloading Aground" notation, with a Displacement of 15032 ton and a
Deadweight of 11700 ton. The lightweight is 3332 ton, included with a strengthened bottom weighing
42
approximately 97 ton more than a ship without a strengthened bottom. Compared to the Deadweight,
the additional steel weight is 0.83 percent. The Attained EEDI will than also be 0.83 percent higher.
0
5
10
15
20
25
30
35
0 5000 10000 15000 20000 25000
DWT
EE
DI
Figure 20 Grab
0
5
10
15
20
25
30
35
0 5000 10000 15000 20000 25000
DWT
EE
DI
Figure 21 Loading unloading aground
As it is unavoidable for certain vessels to apply an additional class notation and therefore strengthen
the construction, the lightweight is considered to be a "penalty" on the Attained EEDI value. Therefore,
it is believed to be justified to correct the Attained EEDI value with a certain factor in order to
compensate for this penalty, in other words there is a clear need for a correction factor.
We would propose to not implement a new additional factor for this purpose, but to consider these
kind of structural enhancements within the correction factor for voluntary structural enhancements.
One of the benefits is that in this way the correction is ship-specific. Further this solution does not
create perverse incentives, as only the actual weight increase is considered, as the factor is based on
two specific construction plans. However, in the current version of the MEPC63 guidelines it is
43
observed that accounting for additional class notations through the voluntary structural enhancement
factor, fiVSE, is not explicitly mentioned, although it might be included.
The adopted text of the current EEDI guidelines concerning the calculation of the correction factor fiVSE
is based on a submission from the International Association of Classification Societies (IACS), see
EE-WG 2/2/10. This submission in fact is an amendment of the original text as provided by Greece. In
the original submission, it is explicitly mentioned that the 'structural class notations' are an example of
voluntary enhancements. For the sake of clarity it might be good to re-adopt a number of examples of
voluntary structural enhancements, including enhancements due to structural or additional class
notations within the guideline, especially since "voluntary"and "class" seem to be a contradiction.
The formula to calculate the attained EEDI than becomes:
refwlci
ME
neff
i
FMEieffieffAEFAE
n
j
nPTI
i
neff
i
iAEeffieffiPTIjAEFAEAE
nME
i
iMEiFMEiME
n
j
j
VfCapacityfff
SFCCPfSFCCPfPfSFCCPSFCCPf
EEDIAtt
1
)()(
1 1 1
)()()(
1
)()()(
1
.
5.2 Evaluation of correction factor against IMO Requirements
The correction factor fiVSE is already present in the formula for calculating the Attained EEDI. It is
therefore assumed that it is meeting the IMO requirements and that it is not further required to
evaluate the correction factor against the requirements.
See Figure 28 for the influence of the correction factor fiVSE on the scatter and R2.
44
6 Effect of the additional correction factors on the scatter
of Attained EEDI values
Application of the proposed additional correction factors should result in a decrease of the scatter of
Attained EEDI as identified for small General cargo ships. As a starting point the Attained EEDI is
calculated for the vessels in the database of this study in a way which is comparable to the way the
IMO calculated the EEDI values to define the reference line. This results in Figure 22 and a R2 of
0.403.
Phase 2
Phase 0
R² = 0.403
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, without corrections applied
Figure 22 Attained EEDI values, without correction factors applied
Application of the Ice Class Correction factor as defined in MEPC 63, gives the following results:
45
Phase 2
Phase 0R² = 0.5011
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, with factors fi and fj applied
Figure 23 Attained EEDI values, corrected for ice class
Consequently the correction factor to account for the variety in operational profiels is applied, which
gives the result as shown in Figure 24. In this figure, no correction for ice class is applied. It can be
seen that the R2 of 0.403 increases to 0.4929 as a result of the correction for speed.
Attained EEDI, with factors fi and fj (for ice class) applied
46
Phase 2
Phase 0
R² = 0.4929
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, with factor fj for a high minimum operational speed applied
Figure 24 Attained EEDI values, corrected for speed
However, if both the correction on ice class and on speed are applied, the R2 is even higher: 0.5218.
See Figure 25.
Phase 2
Phase 0
R² = 0.5218
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, with factors fi, fj and fk applied
Figure 25 Attained EEDI values, corrected for ice class and for speed.
Attained EEDI, with factors fi and fj (for ice class and a high operational speed) applied
47
If the correction for loading equipment is applied, the R2 increases from 0.403 to 0.4193, in which only
the factor for cranes is considered. See Figure 26.
Phase 2
Phase 0
R² = 0.4193
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, with factor fl applied
Figure 26 Attained EEDI values, corrected for the additional weight due to loading equipment
If the correction factors for Ice Class, speed and loading equipment are being applied, than the scatter
decreases considerably and the R2 increases to 0.548. See Figure 27.
48
Phase 2
Phase 0
R² = 0.548
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, with factors fi, fj, fk and fl applied
Figure 27 Attained EEDI values, corrected for ice, speed and loading equipment
By applying the correction factor for structural class notations the scatter decreases slightly. The R2
increases from 0.403 to 0.4076. See Figure 28.
Phase 2
Phase 0
R² = 0.4076
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, with factor fvse applied
Figure 28 Attained EEDI values, with correction factor for additional class notations applied
Attained EEDI, with factors fi and fj (ice class and high operational speed) and fl applied
Attained EEDI, with factor fiVSE applied
49
With all correction factors applied, the scatter decreases considerably. The R2 increases from 0.403 to
0.5553, which is a substantial improvement of the correlation. See Figure 29.
Phase 2
Phase 0
R² = 0.5553
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
0 5000 10000 15000 20000 25000
EE
DI [
gC
O2/(
nm
*mt)
]
DWT [mt]
Attained EEDI values, with factors fi, fj, fk, fl and fvse applied
Figure 29 Attained EEDI values, corrected for ice, speed, loading equipment and additional
structural class notations
Even after the application of these new correction factors, there still are 12 vessels that do not meet
the phase 2 requirements. Introduction of additional correction factors does not mean that all General
cargo ships designs below 20.000 dwt meet the EEDI requirements. Also with inclusion of the new
factors in the EEDI regulatory framework, designers are still forced to adopt and develop technological
developments to improve the energy efficiency of ships. This is further shown through an example.
Consider ship A2, which is a General cargo ship optimized to operate as a small container feeder. The
Attained EEDI value of this ship is reduced by almost 30 percent from 29.3 to 20.7, through the
application of the new correction factors. However, the Required EEDI value for this vessel is 18.0
thus the vessel does not meet the requirements. When a new vessel according to this design is to be
built, a “technological development” is thus required to further reduce its attained EEDI. The hull form
is already optimized, so not much room for improvement in that area. However the current design is
operating on Diesel Oil/Gas Oil with a carbon content factor of 3.206. Changing the design to operate
on LNG would lower the carbon content factor to 2.75, resulting in an attained EEDI which is about 14
percent lower and becomes 17.6, which means that the vessel would comply with the EEDI
Attained EEDI, factors fi and fj (ice class and high operational speed), fl and fiVSE applied
50
requirements. Without the additional correction factors switching to LNG would be far not provide
sufficient solace to meet the EEDI requirements.
51
7 Conclusions and discussions
The study shows that the wide scatter and low square of the regression factor is caused by the
differences in ships-characteristics, which is a consequence of the diverse operational and mission
profiles for which the ships in the small ship segment of the General cargo ship type are designed. In
other words, the General cargo ship characteristics are far from homogeneous. The following three
aspects mainly cause the high scatter as found for small General cargo ships and Container Ships
from 3000 DWT to 20.000 DWT:
- The minimal required operational speed for vessels in the small ship segment
strongly varies. General cargo ships with a high minimal required operational speed,
for example General cargo ships which are also equipped to operate within a
container trade, have substantially higher attained EEDI values as the other General
cargo ships and have difficulties in fulfilling the attained EEDI requirements;
- Small General cargo ships show a large variety of Additional, or Structural Class
Notations. This results in large deadweight variations between vessels with similar
main dimensions and displacements. The additional lightweight as coming from the
structural enhancement required for the Additional Class Notations have a far greater
impact on the EEDI outcome for small ships than for bigger ships.
- There is a large variety in loading gear installed, such as cranes and side loaders, for
vessels in the small ship segment. This has a large effect on the deadweight of
vessels, which are otherwise comparable and therefore affects the outcome of the
attained EEDI calculation. The effect is stronger for smaller ships, as the ratio of the
additional lightweight for loading gear versus deadweight is larger for ships in the
small ship segment.
It is proposed to implement three basic correction factors to enable a fair comparison between diverse
operations whilst at the same time implementing the intent of the EEDI to incentivise improvements in
efficiency for new ships. It is further proposed to only apply these three new correction factors for
General cargo ships below 20.000 dwt. The proposed correction factors are:
- fj Factor for General cargo ships to correct for large variety in minimal required
operational speed;
- fiVSE Factor for small General cargo ship to correct for variety in additional class
notations;
- fl Factor for small General cargo ship to correct for variety in loading gear.
Implementation of these three new correction factors is deemed to be justified as they correct for a
variation that is caused to be able to provide essential services to the society and therefore create an
additional “benefit for society”, besides their capabilities to transport a certain Capacity. Not offering
52
these services would result in a modal shift to road transport or otherwise result in increased CO2
emissions, for example because of the need to operate with a larger number of vessels. Not including
these new correction factors could even lead to an impossibility to replace the existing tonnage with
vessels with equal capabilities, which is expected to be counter productive regarding the aim of the
EEDI regulations. Furthermore, the proposed correction factors follow the criteria for new correction
factors as stated by IMO. They are all based on verifiable characteristics, provide a ship specific
solution, are based on a comprehensive and transparent analysis, are clear and easy to use and do
not create perverse incentives.
By applying these factors, the (mutual) comparison of General cargo ships with a Capacity up to
20.000 dwt improves. For the vessels in the database of this study the R2 increases from about 0.4 to
about 0.55 and the scatter of attained EEDI values thus clearly decreases.
The resulting correlation between reference lines and EEDI values is however still considerably less
than the correlation as found, for example for bulk carriers or tankers. The diversity in mission profiles
and the resulting differences in the design of General cargo ships are so large, that many more
correction factors would be required to reach correlation values similar to those for bulkers and
tankers. The correlation for General cargo ships could further be improved by taking into account
aspects such as the effect of the large differences between design conditions and maximum load
conditions of some General cargo ships.
Implementation of the three proposed correction factors improve the inclusion of small general cargo
ships in the EEDI regime. In this way also General cargo ships specially designed for niche markets
with very specific operational profiles can be assessed in a fair manner. However, the inclusion of
correction factors for General cargo ships in the EEDI regime does not take away the need to take
measures to optimize the energy efficiency to fulfil future EEDI requirements, as a substantial number
of the existing designs do not meet the phase1 and phase 2 requirements with the new correction
factors applied.
Recommendations
This study indicated that there are many more differences between vessels in the same deadweight
range, as a consequence of the diversity in mission profiles, affecting the Attained EEDI value. It is
recommended to further investigate these aspects in order to be able to further reduce the scatter for
General cargo ships. Other differences that affect the attained EEDI include:
Differences in hold volume, which consequently results in large differences in gross tonnage
and lightweight;
Differences between the design conditions and the vessel's maximum capabilities. For
example some General cargo ships have a design draft which corresponds with the maximum
scantling draft, while others are optimized for a partially loaded draft which is considerably
smaller;
53
Sailing area for which the vessel is designed and optimized, which could result in large
differences in main dimensions (L, B, T), among others due to main dimension restrictions in
ports, canals, locks, etc..
It is further recommended to investigate whether it is possible to harmonize the correction factors
within the EEDI methodology for various ship types. It might for example be feasible to apply the
proposed methodology by Sweden, which is developed for the inclusion of RoRo vessels in the EEDI
regime, on General cargo ships to account for the variety in minimum operational speed, instead of
implementing a special correction factor fj for General cargo ships. A limitation of the various
correction factors per ship type would in our opinion improve the overall clarity of the methodology.
54
References
[1] Anink D., Krikke M., Analysis of the effect of the new EEDI requirements on Dutch build
and flagged ships, CMTI Report No. 3134, July 2011, Zoetermeer, The Netherlands
[2] Anink D., Krikke M., The IMO Energy Efficiency Design Index – A Netherlands Trend
Study, CMTI Report No. 3064, January 2009, Zoetermeer, The Netherlands
[3] Anink D., Krikke M., Energy efficiency of small ships and non conventional propeller
ships, CMTI Report No. 3075, January 2010, Zoetermeer, The Netherlands
[4] Bergholtz J., Wiström A., A Swedish Proposal For The Inclusion of the Ro-Ro Ship
Segment into the IMO Energy Efficiency Regulatory Framework.
[5] Deltamarin, Study on tests and trials of the Energy Efficiency Design Index as developed
by the IMO – Applicability and refinement of the EEDI for RoRo, RoPax Vessels and
Specialized ships, Deltamarin report 6543, May 2011, Raisio Finland
[6] Steamship Insurance Management Services Ltd. [http://www.simsl.com/Risk-
Alerts/RA12GeneralCargoCellularContainer.pdf Consulted May 20th 2012.
[7] Kristensen H.O., Historical Data Analysis of Tankers and Bulk Carriers. Technical
University of Denmark, 30 November 2011, Denmark.
[8] International Maritime Organization. Technical and operational measures to improve the
energy efficiency of international shipping and assessment of their effect on future
emissions. November 2011.