Energy efficiency design index verification through actual power and speed correlation
Energy Efficiency Design Index Verification
through Actual Power and Speed Correlation
Quang Dao Vuong1, Professor Don Chool Lee2, Professor Ronald D. Barro*
1. Mokpo National Maritime University, quangdao.mtb@gmail.com
2. Mokpo National Maritime University, ldcvib@mmu.ac.kr
*. Corresponding Author: Mokpo National Maritime University, rbarro@mmu.ac.kr,
91Haeyangdaehak-ro, Mokpo-si, Jeonnam, South Korea
Abstract. The International Maritime Organization (IMO) mandatory requirement for Energy
Efficiency Design Index (EEDI) has been in place since 01 January 2015 to address emission and global
warming concerns. This regulation must be satisfied by newly-built ships with 400 gross tonnages and
above. In addition, the MEPC-approved 2013 guidance, ISO 15016 and ISO 19019 on EEDI serves the
purpose for calculation and verification of attained EEDI value. As such, verification should be carried-
out through an acceptable method during sea trial and this demands extensive planning during
propulsion power system design stage. Power and speed assessment plays the important factor in EEDI
verification. The shaft power can be determined by telemeter system using strain gage while the ship
speed can be verified and calibrated by differential ground positioning system (DGPS).
An actual measurement was carried-out on a newly-built ship during sea trial to assess the correlation
between speed and power. In this paper, the Energy-efficiency Design Index or Operational Indicator
Monitoring System (EDiMS) software developed by the Dynamics Laboratory-Mokpo National
Maritime University (DL-MMU) and Green Marine Equipment RIS Center (GMERC) of Mokpo
National Maritime University was utilized. Mainly, EDiMS software employs four channels – engine
speed, ship speed, shaft power and fuel consumption - for the verification process. In addition, the
software can continuously monitor air pollution and is a suitable tool for inventory and ship energy
management plan. Ships greenhouse gas inventory can likewise be obtained from the base of emission
result during the engine shop test trial and the actual monitoring of shaft power and ship speed. It is
suggested that an integrated equipment and compact software be used in EEDI verification. It is also
perceived that analog signals improve the measurement accuracy compared to digital signal. Other
results are presented herein.
Keywords: shaft power, ship speed, exhaust gas emissions, energy efficiency design index (or
operational indicator) (EEDI, EEOI), ship energy efficiency management plan (SEEMP).
1. Introduction
Shipping is the most efficient form of cargo transportation and with its increasing globalization have
lead to the continued growth of the maritime transport. Along with this development, ships’exhaust
emissions into the environment have become a big concerning issue. In addition, potential harmful
influence on human health, cause acid rain and contribute to global warming are seen to be some of the
negative effects of these emissions. In 2009, the shipping sector was estimated to have emitted around
3.3% of global CO₂ emissions of which the international shipping contributed roughly 2.7% or 870
million tonnes. If unabated, shipping’s contribution to greenhouse gases (GHG) emissions could reach
18% by 2050 [1].
To address this concern, the IMO’s pollution prevention treaty (MARPOL) under Annex VI has adopted
the mandatory energy-efficiency measures to reduce emissions of GHG from international shipping. In
July 2011, the ‘Energy Efficiency Design Index’ (EEDI) was adopted setting the minimum energy
efficiency requirements and must not be exceeded the given threshold by new ships built after 2013. It
is based on a complex formula, taking the ship’s emissions, capacity and speed into account. The target
requires most new ships with 400 gross tonnages and above to be 10%-, 20%-, and 30% more efficient
102
by the year 2015, 2020 and 2025 respectively. The required EEDI value for newly-built tanker vessels
with variation capacities is shown in Figure 1.
∑
×
×
.
=
=
(1)
×
Figure 1 Required EEDI newly-built tanker vessels with variation capacities
Power and speed assessment plays the important factor in EEDI verification in accordance with the ISO
regulations (Equation 1). The engine power can be measured by telemetric system using strain gage.
The ship speed is obtained by differential ground positioning system (DGPS). An actual measurement
was carried-out on a newly-built ship during sea trial to assess the correlation between speed and power.
During sea trial, the output power, sailed route and ship speed were measured simultaneously. All signals
were recorded and analyzed by EVAMOS (Engine / Rotor Vibration Analysis Monitoring System)
software with EDiMS developed by the DL-MMU and the GMERC of Mokpo National Maritime
University [2]. The software can continuously monitor air emission and is a suitable tool for inventory
and ship energy management plan. Ships GHG inventory can likewise be obtained from the base of
emission result during the engine shop test trial and the actual monitoring of shaft power and ship speed.
It is suggested that an integrated equipment and compact software be used in EEDI verification. It is
also perceived that analog signals improve the measurement accuracy compared to digital signal.
2. Engine power and ship speed measurement with EDiMS software
2.1 Power measurement
For power measurement, the MANNER telemetric system was
used. One full bridge strain gage (Wheatstone bridge) was installed
to measure the shear stress on the intermediate shaft when the
engine is running. The basic diagram of the Wheatstone bridge is
shown in Figure 2. It includes 4 gages having variable resistors
changing proportionally with the changing of the surface length of
the shaft. When stress exists, it results in shaft deformation and
changes the gage resistance and consequently change the ratio
between the output and input voltage (Vout/Vin) applied on the strain
gage. This ratio varies as a linear function of the stress on shaft. As
such, the torque generated on shaft by the diesel engine can be
measured after calibration. Together with the shaft speed measured
by tachometer, the shaft power can be obtained by the following
equations:
Figure 2 Wheatstone bridge
103
=
=
(2)
(3)
with:
= 2
=
(4)
Where: P is power (W); T is torque
(N); ω is angular velocity (rad/s); n is
shaft speed (r/min); G is modulus of
elasticity (N/m2); Zp is section
modulus (m3); d is shaft diameter
(m).
Figure 3 Telemetric system and strain gage installation
The engine power also can be measured via angular velocity signal. Two systems are recommended to
be installed to ensure continuous engine power measurement in the event one of them failed. The
principal method for measuring angular velocity is using equidistant pulses over a single shaft
revolution. Rotating motion sensors such as gap sensor, magnetic switch sensor, or an encoder can be
used to get the signal of pulses train which has frequency proportional to the angular velocity of rotating
body. The frequency can be measured and then converted to voltage by an F-V converter. From achieved
angular velocity, the angular acceleration can be calculated where torque and engine power is obtained.
The telemetric system and strain gage installation is shown in Figure 3 while the system used for
measuring engine power and ship speed is illustrated by schematic diagram in Figure 4.
Figure 4 Schematic diagram for power and speed measurement
2.2 Ship speed measurement
In order to measure the ship speed, the speed
system including one DGPS antenna and the
ship speed meter (CVC-100GD) was installed.
In this system, the antenna acquires the DGPS
signal in purpose to determine the ship’s
location (by longitude and latitude) in real time.
By the location signal, the ship speed and the
sailed route can be obtained.
Figure 5 Sailing route guidelines for speed trial
Figure 5 shows the sailing route guidelines for speed trials and should be carried out using double runs,
i.e. each run followed by a return run in the exact opposite direction performed with the same engine
settings. The number of such double runs shall not be less than three and should be performed in head
104
and following winds preferably. Each run shall be preceded by an approach run, which shall be of
sufficient length to attain steady running conditions [4].
2.3 EEDI monitoring by EDiMS
Full formula for EEDI calculation:
Main engine’s Emission
Auxiliary engine’s Emission Shaft generator / Motor’s Emission
Efficiency Technologies
EEDI
Transport work
(5)
neff
neff
n
nME
n
nPTI
AE
f j
P
ME(i).CFME(i).SCFME(i) P .CFAE .SCFAE
f j .
PPTI (i)
feff (i).P
C
FAE .SCF
feff (i).Peff (i).CFME .SCFME
AEff (i)
AE
j1
i1
j1
i1
i1
i1
fi.Capacity.Vref . fw
Engine Power (P) at 75% load
Specific Fuel Consumption (SFC)
Peff
main engine power reduction due to
individual technologies for mechanical
energy efficiency
auxiliary engine power reduction due
to individual technologies for electrical
energy efficiency
SFCME
SFCAE
SFCAE
Main engine (composite)
Auxiliary engine
Auxiliary engine (adjusted for shaft
generators)
*
PAEff
SFCME(i) Main engine (individual)
PPTI
PAE
power take in
combined installed power of auxiliary
engines
Correction and Adjustment Factors (F)
feff
Availability factor of individual energy
efficiency technologies (=1.0 if readily
available)
PME
main engine power
CO2 Emissions (C)
fj
f
Correction factor for ship specific design
elements
Coefficient indicating the decrease in
ship speeddue to weather and
environmental condition
CMFE
CFAE
CFME
Main engine composite fuel factor
Auxiliary engine fuel factor
Main engine individual fuel factors
Ship Design Parameters
fi
Capacity adjustment factor for any
technical /regulatory limitation on
capacity (=1.0 if none)
Vref
Ship speed
Capacity Deadweight Tonnage (DWT)
EDiMS software is included in
EVAMOS program developed by DL-
MMU. Figure 6 shows the design
concept display unit of EDiMS. For
monitoring EEDI on the simple
propulsion system, EDiMS software
simply requires signals from engine
speed, ship speed and shaft power. The
fuel consumption and NOx, SOx, PM
emission value measured from shop test
can be used by the curve fitting method
of the Equation 6. Likewise, the fuel
consumption of prime mover can be
applied alternatively by converting
voltage signal of fuel flowmeter. SOx
emission is calculated from sulphur
content and fuel consumption quantity.
Figure 6 EDiMS system and display unit configuration
105
=
+
+
+
(6)
Where c0, c1, c2, c3 are coefficients for each of fuel consumption, NOx, SOx, PM emission - y; x is the
part load ratio for maximum continuous rating.
Figure 7 EDiMS monitor display configuration
Figure 8 EDiMS raw signal and emission values display
106
Figure 7 shows the setup configuration of EDiMS
software. In the case of absence of ship speed signal
form DGPS, ship speed can be estimated by using the
shaft speed and propeller pitch data with assuming
there is no slip. The full equation of EEDI (Equation5)
used for EDiMS includes several adjustment and
tailoring factors to suit specific classes of vessels and
alternate configurations and operating conditions, but
in the case of simple propulsion system without driven
generator installed on shaft and ignoring the negligible
factors, the fundamental formula can be simplified to
Equation 7:
(
) (
+ 푃 ×퐶
) (7)
푃
푀퐸
×퐶
×푆퐹퐶
×푆퐹퐶
퐹퐴퐸 퐴퐸
퐹푀퐸
푀퐸
퐴퐸
퐸퐸퐷퐼 =
퐶푎푝푎푐푖푡푦 ×푉
푟푒푓
For ships with main engine power of 10,000 kW or
above:
푃
퐴퐸
= 0.025×푀퐶푅푀퐸 + 250 (8)
Figure 9 CO2 emission rate based on
fuel type emission values display [1]
For ships with main engine power below 10,000 kW:
= 0.05×푀퐶푅푀퐸 (9)
푃
퐴퐸
with MCRME is main engine power at MCR (kW).
2.4 EEDI monitoring by EDiMS on actual ship test
The EVAMOS program including EDiMS software was used for EEDI monitoring on a new built ship.
Table 1 lists the ship and main engine specifications. The measurement was carried out during the speed
test of sea trial in order to settle the relation between ship’s speed and engine load as well as the EEDI
calculation. The comparison of measured fuel consumption during sea trial and the builder shop test is
given in Table 2.
Table 1 Specification of experiment ship and main engine
Type
Tanker
Type
6G70ME-C9.2
16,590 kW
Capacity
Ship length
Breadth
Draft
158,863 tonnes
247.17 m
48.00 m
17.15 m
2016
Power at MCR
Max. continuous speed 77.1 r/min
Main
engine
Ship
Cylinder bore
Stroke
700 mm
3,256 mm
6
Year
No. of cylinder
Table 2 Fuel consumption of 6G70ME-C9.2 engine at sea trial and builder shop test
Load
M/E r/min
Round
25%
48.6
-
50%
61.2
-
70%
71.9
75%
73.6
100%
80.5
R-1
R-2
R-1
R-2
R-3
R-4
R-1
R-2
Mean value at
sea trial (g/kW-hr)
164.98 164.79 168.2 166.25 167.75 166.84 171.66 171.83
-
-
164.89
163.46
167.31
165.86
171.75
170.18
Shop test result
(g/kW-hr)
175.66 165.34
107
Based on the fuel consumption of builder shop test, the coefficients for fuel consumption were obtained
to be: c0 = 208.86; c1 = -1.896, c2 = 0.0253, c3 = -0.0001. By using these coefficients, EDiMS software
can estimate the engine fuel consumption for each power load ratio at any certain engine speed. The fuel
used for engine is heavy fuel oil (HFO), the CO2 emission rate CFME = CFAE = 3.144 ton CO2/ton fuel
(Figure 9); SFCAE= 190 g/kW-hr; PAE = 664.75 kW. In addition, with the signals of shaft power from
strain gage and ship speed from DGPS sensor, the EEDI was calculated and monitored online. Under
the IMO guidance for speed - power measurement, the measuring time for each round is at least 10
minutes at constant condition. All data were saved on computer and can be analysed again in laboratory.
Figure 10 Sailed route and ship speed measured by DGPS sensor at 75% load Round 1
Figure 11 Sailed route and ship speed measured by DGPS sensor at 75% load Round 2
Figure 12 Shaft power measured by strain gage at 75 % load Round 1
108
Table 4 Measuring results and EEDI calculation
70% 75%
Load
100%
R-1 R-2
11,314 11,076 12,058 11,866 11,862 11,970 15,673 15,648
Round
R-1
R-2
R-1
R-2
R-3
R-4
Engine power (kW)
Fuel consumption (g/kW-hr) 164.98 164.79 168.2 166.25 167.75 166.84 171.66 171.83
Ship speed (knots)
EEDI (g CO2/t nm)
EEDIaverage
13.52 14.53 15.37 13.80 15.60 14.72 15.36 17.79
2.89
2.63
2.75
2.98
2.66
2.83
3.59
3.10
2.76
2.80
3.35
The data measured during this sea trial using the EDiMS software confirms the correlation between
engine fuel consumption, shaft power, ship speed and CO2 emission. Based on these factors, EDDI value
was calculated and shown in Table 4. Officially, the correction speed should be used for calculation with
the concern of the wind, sea wave and the other sea conditions and is a complex calculation. The ship
speed used in this study (non – official test) is actual speed without correction. The measurement results
indicated that the EEDI value of subject vessel increases at higher load. The required EEDI is the limit
for the attained EEDI of a ship and depends on its type and size and its calculation involves use of
reference lines and reduction factors. Reference line represents the reference EEDI as a function of
ship size. Reduction factor represents the percentage points for EEDI reduction relative to the reference
line, as mandated by regulation for future years. This factor is used to tighten the EEDI regulations in
phases over time by increasing its value. The reduction factor at different phase implementation is shown
in Table 5.
Table 5 Reduction factor (%) for the EEDI relative to the EEDI reference line [5]
Phase 0
from Jan
2013
Phase 1
from Jan
2015
Phase 2
from Jan
2020
Phase 3
from Jan
2025
Capacity
(DWT)
Ship type
>15,000
3000-15,000
>20,000
0
10
0-10*
10
20
0-20*
15
30
0-30*
30
Tanker
n/a
0
General cargo
ship
4,000-20,000
n/a
0-10*
0-15*
0-30*
* Reduction factor to be linearly interpolated between the two values dependent upon vessel
capacity. The lower value of the reduction factor is to be applied to the small ship size.
n/a means that no required EEDI applies.
The reference line values can be calculated as (see Figure 1):
= ×
(10)
(11)
= (1 −
/100)×
For tanker: a = 1218.80, c = 0.488 [5]. Attained EEDI must always be less than or equal to required
EEDI.
109
The subject vessel was built in 2016 and thereby must adhere to Phase 1 of the EEDI reduction factor
equivalent to 10%. The shaft power ratio required by the IMO regulation is at 75% load only, however
at all the other load conditions, the EEDI value (Table 4) is lower than the required limit (about 3.53 g
CO2/t nm). As such, the subject vessel satisfies the IMO regulation for Energy Efficiency Design Index.
In addition, monitoring the SOx, NOx, PM emission are available in EDiMS software. All of these signals
can be measured, analysed and displayed online. File management of all data can be saved on hard drive
of PC storage or either be transmitted to onshore shipping company office through internet connection.
3. Conclusion
Owing to rapid development in the shipping industry and maritime transportation, air pollution
emissions from ocean-going ships are continuously increasing. Exhaust gases from ships contain CO2
and many other harmful pollutants. The increased volume of air pollutant results in serious negative
effects to environment, to human health and contributes to global warming. In order to control CO2
emission from shipping, the Energy Efficiency Design Index requirement was adopted by IMO for
newly-built ships. The EEDI expresses the amount of CO2 emission on transport ability, assesses the
energy consumption of a ship under normal seagoing conditions. The passage of EEDI regulation came
with one important compromise that could affect the magnitude of benefits in developing more efficient
ships to serve the demand.
The Energy-efficiency Design Index or Operational Indicator Monitoring System (EDiMS) was
developed by DL-MMU in order to analyse and monitor EEDI on the base of results during the engine
shop test trial and the actual monitoring of shaft power and ship speed. It is recommended for EEDI
verification to use a compact software capable of measuring the shaft power and ship speed
simultaneously. This software is a suitable tool for inventory and ship energy management plan. Not
only EEDI, EDiMS can estimate and help to control air pollution source in exhaust gases such as SOx,
NOx and PM. All of the energy-efficiency indexes can be displayed online continuously and transmitted
to other server via internet connection. The software capability should be continually improved
according to the expectations and participations from the ship owners and shipping companies with
accurate advices from specialists.
References
[1] IMO, Second IMO GHG Study 2009, International Maritime Organization, London, UK, 2009
[2] Donchool Lee, Kisee Joo, Takkun Nam, Eunseok Kim, Sanghwan Kim, Development of Integrated
Vibration Analysis and Monitoring System for Marine Diesel Engines and Ship Machineries,
©CIMAC Congress, Bergen, Norway, 2010.
[3] MAN Diesel & Turbo, EEDI - Energy Efficiency Design Index, Copyright ©MAN Diesel & Turbo,
D2366498EN-N2, printed in Germany GGKM-04152.
[4] IMO, Ships and Marine Technology – Guidelines for the Assessment of Speed and Power
Performance by Analysis of Speed Trial Data, International Maritime Organization, 2002.
[5] IMO, M2 Ship Energy Efficiency Regulations and Related Guidelines, International Maritime
Organization, 2016.
110
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19/04/2022
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