2. Brief Details about the study
Study encompasses 493 LNG Carriers (>10,000 DWT –
EEDI Requirement). Includes vessels on order up to 2019.
Includes four major propulsion technologies considered.
o Steam Turbine Propulsion System
o Dual Fuel Diesel Electric
(4 stroke – operates on Otto cycle in Gas Mode)
o Slow Speed Diesel Propulsion with Re-liquefaction
o Main Engine Gas Injection (ME-GI)
(2 stroke – operates on Diesel cycle in Gas Mode)
5. Oldest vs Largest
1st Commercial LNG
Largest LNG Carrier
Name Methane Princess Mozah
Entered Service June 1964 September 2008
Gas Capacity 27,400 cubic meters 266,000 cubic meters
Number of tanks 9 5
Length 188 345
Width 24 54
Propulsion Type Steam Heavy Fuel Oil - Motor
6. How does it look ??
• View of a Q-Max ship -
266,000 cubic meters
• One cargo can light up
US homes for one year.
7. How does it look ??
• Inside an LNG tank –
Prismatic Membrane type
made of 1.2 mm thick
• Cargo capacity– 57,700
cubic meters (98.5% of
8. Challenges in carrying LNG
Liquefaction temperature of -161 °C – Cryogenic
Cargo. Special materials and insulations required to
contain the cargo in liquid form.
Due to such low temperature, there is continuous
generation of Boil-off Gas (BOG) which must be
controlled to maintain the tank pressure.
Is highly flammable and has extremely high energy.
16. Marine Engines Operating on Gas
o 2 Stroke Slow Speed Engines
o Operates on Diesel Cycle in Gas Mode
o 4 Stroke Medium Speed Engines
o Operates on Otto Cycle in Gas Mode
17. Diesel Cycle vs Otto Cycle
Diesel Cycle Otto Cycle
Combustion is a constant pressure process Combustion is a constant volume process
Fuel is injected before gas Gas is injected before fuel
No pre-ignition/no knocking Pre-ignition/Knocking
Less methane slip Significant methane slip
High pressure gas injection (300 bar) Low pressure gas injection (<10 bar)
Do not meet NOX Tier III standards Meet NOX Tier III standards
MEGI Propulsion (slow speed engines) DFDE Propulsion (medium speed engines
18. Methane Slip
Methane slip is the unburned methane in the
combustion chamber which escapes into the
atmosphere along with the engine exhaust.
Methane has a GWP of 25 for a 100 year period
Engine Type Methane Slip
% of SFC
DFDE (Otto Cycle – Gas) 5.000 162 3.09%
MEGI (Diesel Cycle – Gas) 0.693 140 0.49%
Diesel (HFO & MDO) 0.034 190 0.02%
20. Energy Efficiency Design Index (EEDI)
EEDI is a performance standard for new vessels, to
encourage more efficient ship design.
IMO’s main motive behind EEDI was to device an
index to represent marine GHG emissions from
Since marine GHG emissions consists primarily of
CO2, the EEDI is representative of only CO2
21. Energy Efficiency Design Index (EEDI)
Originally adopted in 2012 for merchant vessels at MEPC
Amended in 2014, with a special category of LNG
Tankers, apart from other Gas Carriers at MEPC 66.
24. SFC and CF Values Used
2-Stroke SFC claim to be 20% lesser than DFDE (4-stroke Otto Cycle)
These values are without considering the methane slip
Technology & Fuel ME SFC
Otto Cycle – Gas 140 162 2.75
Diesel Cycle - Gas 140 - 2.75
Boiler - Gas 285 - 2.75
Conventional HFO 190 215 3.114
MDO (Pilot Fuel) 6 6 3.206
25. CF Including Methane Slip
Cycle (gas) SFC
CF (gas) with
Otto – 4 stroke 162 2.75 5.0 3.437
Otto – 2 stroke 140 2.75 4.0 3.386
Diesel – 2 stroke 140 2.75 0.693 2.860
0 1 2 3 4
Otto Cycle - 4 stroke
Otto Cycle - 2 stroke
Diesel Cycle 2 - stroke
With Methane Slip Without Methane Slip
Attained EEDI in this report will be referred to as
EIV– Estimated Index Value
This is because, the attained EEDI calculated in
this project might differ from the actual attained
EEDI on board the ship during sea trial.
37. Policy Alternatives
1. No Change in Current Baseline
o On paper EEDI Regulation would still seem to be
o However, would not encourage technological
development towards reduction of marine GHG
o Continue to ignore methane slip
38. Policy Alternatives
2. Maintain Present Reference Baseline with more
o IMO probably have underestimated the technological
development that has taken place
o Reduce 2020-2025 standards by 25% from the
o Reduce 2025 standards 40-50% from the baseline as
o MEPC can have a constant check on the emission
levels and decide future reductions accordingly.
39. Policy Alternatives
3. Change the current Reference Baseline
o Since last reference line based on 2000-2010.
Mostly represent steam vessels
o Since steam propulsion is getting obsolete, make
a new baseline representing current technologies
representing dual fuel engines.
40. Policy Alternatives
4. Include Methane Slip in EEDI Calculations
o EEDI calculation is not representative of the
marine GHG emissions for LNG carriers
o Inclusion of methane is important to correctly
represent the marine GHG emissions.
o This can be done without changing the current
reference baseline, or along with any of the
other policy alternatives suggested above.
41. Policy Alternatives
5. Correction Factor for methane slip
o Propulsion Methodology based correction factor
which can be directly multiplied with CF.
o SlipCH4 will depend upon the engine stroke and
Engine Cycle & Stroke Correction Factor
Otto Cycle – 4 Stroke 1.25
Otto Cycle – 2 Stroke 1.23
Diesel Cycle – 2 Stroke 1.04
CorrectionFactor = 1-
This presentation tries to find out whether the current EEDI regulation
is incentivizing the technological improvement, it aimed at doing.
We see that the EEDI regulation needs to be revamped to make it
more relevant and provide a regulatory push to reduce marine GHG
Inclusion of methane slip for LNG Carriers is necessary if IMO wishes
to use EEDI as an index for marine GHG emissions and just not CO2.
The policy alternatives suggested might provide some answers to
make the EEDI regulation more effective
Thank you Bryan for introducing me. It has been a privilege and fun working at ICCT with all the colleagues, and specially the marine team here at DC.
Over the last one month, I have worked upon this project of Energy Efficiency Regulations for LNG carriers. It mainly covers the efficacy of the energy efficiency regulation for gas carriers.
Some very brief details about my project. This study encompasses 493 vessels, of 10,000 DWT and above – according to IMO regulation. This includes vessels on order up to 2019.
The study is based on the four main LNG propulsion technologies:
Steam Turbine Propulsion System
Dual Fuel Diesel Electric Propulsion (DFDE)
Slow Speed Diesel Propulsion with Re-liquefaction plant.
Main Engine Gas Injection (ME-GI) Propulsion
Some background history on LNG Tankers
First purpose built LNG tanker was Methane Princess built in 1964
Then for almost half a century it was dominated by steam propulsion up to 2000.
Around 2004 DFDE technology came – which is dual fuel engine operating on otto cycle in gas mode.
Then 2007 came Re-liquefaction technology, and them conventional HFO propulsion was possible for LNG carrier
Finally, 2011 came Main Engine Gas Injection technology.
2014, EEDI for LNG carriers was adopted as an amendment to Marpol Annex VI.
This is a comparison between the first LNG ship methane princess and the largest LNG ship Mozah.
It has almost 10 times cargo carrying capacity, double the length and width.
That’s view of how an LNG cargo tank looks from inside. It is one of the modern LNG containment system – GTT Mark III (1.2 mm stainless steel) – primary barrier
Any guesses for capacity of this tank – 57,700 cubic meters
Triplex – aluminium foil 80 micros between glass cloth (0.7 mm thick) – secondary barrier
Re-enforced polyurethane foam as insulator (100 and 170 mm) and then finally plywood (12.5 mm).
That’s the ship Mozah
One cargo of it provides energy for up to 70,000 US homes (2008 figure – when the ship was built).
Liquefaction temperature is -161. Such low temperature is a major challenge. Special materials required to contain the cargo in liquid form (Invar, plywood and stainless steel).
Such low temperatures lead to constant production of BOG, which must be taken out of the tank to maintain the tank pressure.
Also, it is highly inflammable and has extremely high energy (40 atom bombs supposedly).
Steam is the oldest form of propulsion.
Due to the system’s innate ability to handle BOG, this was prevalent over many years until DFDE technology came across.
The steam was generated in Boiler which burned the BOG in boiler.
The first motor propulsion alternative for the LNG Steam propulsion came as DFDE.
This dual fuel technology used four stroke medium speed engines operating on Otto Cycle.
These engines are used as auxiliary engines to generate electricity and then propeller is driven by an electric motor.
This system requires a GCU – Gas Combustion Chamber for maintain the tank pressure.
Finally, 2007 first ship with LNG re-liquefaction technology developed which could be propelled on conventional HFO.
These are the largest type of ships with cargo carrying capacity of 266,000 cubic meters.
The technology is not a big success, so there is no current order based on this technology.
Most recent technology. Based on 2 stroke slow speed dual fuel engines – working on diesel cycle while in gas mode.
Auxiliary engines are also dual fuel 4 stroke medium speed similar to DFDE engines.
So primarily as mentioned before there are currently two major dual fuel technologies
One DFDE based on Otto Cycle and the other is MEGI based on Diesel Cycle.
This graph a comparison between Otto Cycle and Diesel Cycle
As shown in the diagram, the primary operating difference is that the Otto cycle has a constant volume process during the combustion, whereas the Diesel Cycle follows a constant pressure process during the combustion.
Due to this operating principle the engines in Otto cycle has a higher methane slip (lower injection pressure) compared to the ones operating on Diesel cycle (higher injection pressure)
The MEGI technology is based on Diesel Cycle while the DFDE technology is based on Otto Cycle.
Since EEDI is an index to determine the GHG emission, the methane slip becomes important since methane is one of the major contributors in GHG emissions.
Methane slip is the unburned methane in the combustion chamber that escapes along with the engine exhaust.
The table shows the methane slip percentages for the different engine types. It is the highest for the Otto cycle and much lower for the Diesel cycle dual fuel engines. It is almost negligible for engines operating on HFO.
So EEDI can be simply described as the cost to the environment by the benefit to the society which in technical terms is grams of CO2 emitted per transport work.
IMO devised the EEDI as an index for marine GHG emission, which was primarily CO2, as marine vessels traditionally used HFO for propulsion.
However, the methane slip in modern dual fuel engines questions the efficacy of EEDI regulation for LNG carriers.
Originally EEDI was adopted at MEPC 63 in 2012 by IMO. MEPC is the Marine Environment Protection Committee which is an IMO sub-committee looking after policy regulation for marine environment and related emissions.
EEDI for LNG Carriers was adopted at MEPC 66 in 2014 as an amendment to Marpol Annex VI EEDI Regulation.
It was adopted as IMO recognized the LNG tankers did not represent conventional propulsion technologies.
This is taken from ICCT’s first policy update on EEDI around 2012.
The EEDI formula at the first glance very complicated.
However, in this report there are no cases concerning shaft generator and efficiency technologies.
So our formula gets reduced a bit simpler. Also, the capacity adjustment factor in the denominator is considered to be 1.
Table showing the values of SFC and CF assumed for calculation.
SFC for 2 stroke ME using both Otto and Diesel Cycle is assumed as low as 140 g/kWh because mentioned 20% lesser than DFDE engines (162). Since very recent technology, no sea trial SFC available.
CF values are as provided in MEPC reports and sample examples
Table provides CF corrected by including the methane slip.
The maximum change is for engines using Otto cycle - 23%. Medium speed Otto Cycle engines have CF values using 3.437
Diesel Cycle 2 stroke have lesser effect of 6% increase.
Attained EEDI is the value calculated using the formula shown in the first few slides.
Attained EEDI must be less than or equal to than the required EEDI standards.
Here x is the % reduction from the reference baseline value. 10% every 5 years
This bar chart provides information about the ship delivery from 1990 onwards. This chart provides the first glimpse as to why EEDI for LNG carriers is questionable.
Blue is Steam. Red is HFO – was not much successful and no further orders. Green – Otto Cycle DFDE engines. Purple – Diesel Cycle MEGI engines (newest technology).
Shows how steam vessels suddenly has got out of favor from 2010 onwards.
Between 2001-2010 maximum number of steam vessels were delivered. And this is the period that ships delivered were considered for the EEDI reference baseline.
However, the current deliveries are dual fuel engines (motor propulsion) compared with EEDI baseline based on steam vessels.
Graph of steam vessels attained EEDI. As shown previously, these vessel types are fast getting obsolete.
Oldest propulsion type, most of them do not conform with future regulations. However, there are a few outliers.
Graph of HFO Propelled vessels with re-liquefaction plant attained EEDI. These vessels were built before 2010.
Some of them able to comply standards up to 2019. However, none of them can comply with future regulations.
Graph shows the attained EEDI for Dual Fuel Engines operating on Otto Cycle in gas mode.
Transparent triangles are the EEDI values including the methane slip, and blue circles are without the methane slip.
The increase is proportional to their EEDI i.e. 23% increase from their EEDI without methane slip.
Graph shows the attained EEDI for Dual Fuel Engines operating on Diesel Cycle in gas mode.
Transparent squares are the EEDI values including the methane slip, and purple circles are without the methane slip.
The increase is proportional to their EEDI i.e. 6% increase from their EEDI without methane slip.
This graph shows percentages of different vessel types complying with various EEDI standards – without the methane slip
Blue is 2025 onwards and more than 60% of dual fuel engines operating on Otto Cycle.
Purple is for reference baseline. Diesel Cycle DF engines – newest technology. However, most of them just are just able to comply with the current regulations.
HFO and Steam ships still manage to comply with some of the future regulations.
This is the same graph including the methane slip.
Percentage of DF Otto cycle engines change drastically – 2025 onwards less than 30%.
DF Diesel Cycle engines are not able to comply with current regulations – even though small increase.
No change in steam and HFO vessels.
Coming on to the policy alternatives part.
First is that we make no changes to the current EEDI Regulation for LNG Carriers.
On paper everything would still seem efficient, as lot of the vessels will be complying with future regulations.
Closer look and we will see that the EEDI levels are constant for more than a decade and there has not be much regulatory push to reduce marine GHG emissions.
Second option is that we maintain the current reference baseline but have more stringent future reduction.
This is because IMO might have under estimated the technological development that has taken place in the last few years.
Like 25% reduction from the reference baseline for 2020-2025 standards
Also 40-50% reduction from the reference baseline for 2025 onwards. This should be decided at future MEPC meetings depending upon the current emissions levels.
Third alternative is to change the current reference baseline, to represent the modern fleet of LNG tankers
Since 2001-2010 steam carriers was the predominant deliveries, and now they are almost obsolete. The current EEDI baseline is not a good reference point for new deliveries.
With the new reference line, we can continue with the same reduction of 10% every 5 years.
Include methane slip in the EEDI calculations.
The inclusion will make EEDI correctly reflect the marine GHG emissions
A way to do it probably is to provide a propulsion methodology based correction factor.
This will depend upon the engine operation type and stroke.
The correction factor is as shown in the formula
The table provides the correction factor values for the currently three possible dual fuel engine options.
Concluding … so we can see the EEDI regulations for the LNG Carriers is not representative of the current fleet and does not provide sufficient regulatory push to improve their current EEDI standards.
Also, Methane slip needs to be considered if IMO wishes to use EEDI as an index to measure marine GHG emissions.
Policy alternatives suggested might be a way forward to make the EEDI more representative of the current LNG fleet.