Proposed Inland Oil Tanker Design in Bangladesh Focusing CO₂ Emission Reduction Based on Revised EEDI Parameters

Comments by Reviewer-1

Reply from authors

1.      

The structure of the manuscript should be divided into clearly separated parts. In the present form it is not easy to say where there is a literature review and where own research starts. The methodological section is missing. It should be clearly stated what is taken from other publications and what is the original contribution of the manuscript.

·       Methodology provided.

·       Literature review and own research part is more distinguishable

2.      

Is table 2 taken from the literature or is it authors’ own research. It is not clear.

Table is taken from author’s own research, published in previous journal. In the update of the current paper, it is made clear.

3.      

There is no research question or a hypothesis in the manuscript. The research gap should be shown.

Introduction part has been improved to explain the research gap and research question.

4.      

In sections 2,3, and 4 there are tables which are not described in the text in a detailed manner. More detailed descriptions and conclusions should be added.

Explained in more detailed manner.

5.      

It is not precisely explained how the sensitivity analysis was conducted.

Explained in detail now.

6.      

There are only 10 positions of the literature. The literature review should be expanded.

Literature review has been expanded.

7.      

I line 36-37 authors write “From Figure 1, it is evident that CO₂ emission from inland ships is more than double over other maritime transport”. But in fact, the figure says the opposite. Emission from inland ships is half that from maritime transport.

Figure 1 was a wrong representation and I am sceptic about the rightness of the figure. Let me explain.

Sea going ships are more energy efficient is most cases, because they do not face the shallow water effect and other restrictions. For unrestricted voyage of sea going ships, it is possible to continue the journey for long time at the most efficient RPM of the engine. However, for inland ship, this is not possible, primarily because of the shallow water effect and river traffic. As a result, generally the CO₂ emission/tonne-km is higher for the case of inland ships.

We have used the figure shown in the following link in our previous research paper.

https://www.eea.europa.eu/data-and-maps/figures/specific-co2-emissions-per-tonne-2. This figure reflects the above justification.

This time, we have used

https://www.eea.europa.eu/data-and-maps/daviz/specific-co2-emissions-per-tonne-2#tab-chart_1. While using, I thought this is the updated one, as this one is till 2014. It was my mistake, which I should not over look as a researcher. Actually, I could not think that similar updated figure reflects wrong assumption.

If you look into the both figures, it looks similar- only the latest one looked updated. However, updated data should be equal to previous data till 2011. Which does not match.

Therefore, I must say, I do not agree with the previous figure 1 now and corrected figure 1 is presented along with some supported literature review.  

8.      

In line 147 Group “1” is missing

In line 169 Group “3” is missing

Corrected accordingly.

9.      

English should be improved. For example in lines 162-163 a word “increasing” is used three times. It does not sounds good.

More effort is provided to improve the English language.

Comments from Reviewer-2

Reply from authors

1.      

The methodology of the research should be described in more detail.

Methodology section has been added.

2.      

There are no studies of other researchers, which would enrich the content of the article.

More literature review has been added.

3.      

However, there were missing some interesting items of literature on the EEDI

More literature review has been added.

Comments from Reviewer-3

Reply from Authors

1.       

Although the study is well documented and structured, the flow between chap 4 and chap 5 would need more clarity - to guide more the reader through the sensitivity analysis based on the revised EEDI applied to the inland waterway fleet.

Flow between chapters improved with new write up and attempts taken to guide the reader more through sensitivity analysis based on revised EEDI.

2.       

Add a methodology chapter before chapter 4 explaining the process: revised EEDI > sensitivity analysis > design improvements areas for increased energy efficiency > simulation and validation of new proposed design with CFD (through 1 specific ship case).

Methodology chapter added for more clarity of the paper accordingly.

3.       

Especially the sensitivity analysis needs clarification - the data are presented in ch4 but it is chap 5 that is entitled sensitivity analysis.

New chapter added before sensitivity analysis to explain more about the analysis.

4.       

Be very clear about which EEDI-figure/formula is used throughout the article. The keyword mentioned EEDI and EEDI, and it is important to specify which EEDI is referred to in the text and tables.

Updated according to your suggestion.

5.       

The introduction of chap 5 is presented as the results of sensitivity analysis (line 90 "following results); however, the bullet points presented are not systematically or clearly referring to the findings of table 3-5; and in that way, the results of the sensitivity analysis are not straightforward.

Recommendation: add an explanation of the sensitivity analysis, how the results are extracted, and for each point (parameter/potential improvement), refer to the findings from the fleet studied.

Sensitivity analysis chapter has been revised accordingly as per the recommendation.

6.       

10-13%: be more specific about what the range represent (if it is derived directly from the 7.54% - 13.65%, or if other observations are taken into account to conclude about 10-13%?)

Specified accordingly.

Chronological comments (line numbers cited with #):

7.       

#18: "forbid" - please consider mentioning its inadequacy for

inland ships instead of "forbid".

Updated accordingly

8.       

#25: "resistance reduction" is referred to energy efficiency on chap 5 and CO2 emissions reduction in conclusion. Although it is a logical consideration, please provide consistency (i.e. specifying CO2 reduction / fuel savings through hull optimization).

Updated accordingly

9.       

#26: EEDI_INLAND is not used in the text; instead EEDI_BD appears in tables 7-9.

Corrected the mistake

10.    

#38: " EEDI " - please use consistently in the rest of the

text.

Corrected accordingly

11.    

#36: referring to fig.1 about Inland vs Maritime. It is maritime transport which has emissions more than double of the ones of Inland waterway.

Figure 1 was a wrong representation and I am sceptic about the rightness of the figure. Let me explain.

Sea going ships are more energy efficient is most cases, because they do not face the shallow water effect and other restrictions. For unrestricted voyage of sea going ships, it is possible to continue the journey for long time at the most efficient RPM of the engine. However, for inland ship, this is not possible, primarily because of the shallow water effect and river traffic. As a result, generally the CO₂ emission/tonne-km is higher for the case of inland ships.

We have used the figure shown in the following link in our previous research paper.

https://www.eea.europa.eu/data-and-maps/figures/specific-co2-emissions-per-tonne-2. This figure reflects the above justification.

This time, we have used

https://www.eea.europa.eu/data-and-maps/daviz/specific-co2-emissions-per-tonne-2#tab-chart_1. While using, I thought this is the updated one, as this one is till 2014. It was my mistake, which I should not over look as a researcher. Actually, I could not think that similar updated figure reflects wrong assumption.

If you look into the both figures, it looks similar- only the latest one looked updated. However, updated data should be equal to previous data till 2011. Which does not match.

Therefore, I must say, I do not agree with the previous figure 1 now and corrected figure 1 is presented along with some supported literature review.

12.    

#48-51: this is the description of the approach. It should be extended in a methodology chapter.

Extended in the methodology chapter accordingly

13.    

#54: "fare" >> "fair"

Corrected accordingly

14.    

#56: "brief"

Corrected accordingly

15.    

#62/63: "knotical" >> "nautical "

Corrected accordingly

16.    

Table 1: P PT(i) >> shouldn't it be P PTI(i)?

Corrected accordingly

17.    

Table 2:

- "Sl" not explained

- In last column, specify " EEDI_INLAND"

Sl use as the short form of serial. Now it is serial as updated.

EEDI_INLAND Corrected accordingly

18.    

#75: says 102 oil tankers (which is well the sum of the three groups indicated in tables 3-5), but at line #48 it is mentioned 251 oil tankers.

The total number is 102. 251 is a mistake. Actually, my ongoing PhD thesis is inland on general cargo, oil tankers and passenger ships. The number of general cargo ships are 251 in my research. By it was a mistake. Corrected accordingly.

19.    

#77: add a short sentence justifying the 3 categories, i.e. the 51-61 limits for the 3 groups;

Updated accordingly

20.    

#81: suggest adding a sentence explaining how the well & poor performing vessel ranges were decided. Were the dataset cut in two, or at the median? Also specify that the well/poor performing is according to the revised EEDI only (no other parameters).

Corrected accordingly in the revised version.

21.    

#82: Table 3: Specify EEDI_INLAND in first column; maybe adding the EEDI_IMO would be interesting to see. Also, specify that min/ max is according to EEDI-value, not reflecting performance (i.e MIN is higher perf, Max is lowest).

Corrected accordingly in the revised version.

22.    

#85: I would suggest adding a sentence concluding on the application of the revised EEDI.

Updated accordingly in the revised version.

23.    

The introduction part needs more explanation and justification (see earlier comments). A short methodology description could be added before ch 4; but also an explanation of how the results from the sensitivity analysis were extracted.

Updated accordingly in the revised version.

24.    

Is the sensitivity analysis based on table 3-5 only or on the detailed data set of the 102 vessels? In the latest case, please explain brief how it was conducted; the steps followed to arrive at the results presented in line #87-103.

Based on 102 vessels data. All calculated results for 102 vessels are shown in appendix-A in brief.

25.    

#91-93: here EEDI is commented using references. Is that statement based on result from the sensitivity analysis or only the references [8] and [9]? Is it referring to EEDIIMO or EEDI_INLAND? The figure 10 and 15% are not supported by the results in tables 3-5.

This part of the manuscript has been revised.

26.    

#94: here specify that you refer to EEDIINLAND

This part of the manuscript has been revised.

27.    

#98: explain more the "proposed baseline".

‘Baseline’, as per EEDI IMO is a line that defines maximum achievable of CO₂ emission per tonne-mile. This part of the manuscript has been revised.

28.    

Generally, these results from the sensitivity analysis should be more explained – with direct reference to the dataset.

Corrected accordingly in the revised version.

29.    

Table 6: interesting and concise table. Specify EEDIIMO Vs Inland in the text. Also, if possible, add reference to dataset and results from sensitivity analysis supporting the "decision to be

taken". One minor thing: the title says "suggestion", while the table says "decision to be taken" – it should be more consistent.

Corrected accordingly in the revised version.

30.    

# Chap 5.1: there is no chap 5.2 or more, so adding this subchapter may be unnecessary.

Corrected accordingly in the revised version.

31.    

#107: the figure of 10% need more explanation. See comment above; adding a quantitative result from the sensitivity analysis to justify the improvement suggestion in table 6 would be useful;

This part of the manuscript has been revised.

32.    

#110-126: some repetition of arguments in Table 6, so one could expect that the justification of the 10% improvement could also come in this paragraph. However, the only quantitative element

is referring to a other study, not the sensitivity analysis of the 102 oil tankers.

This part of the manuscript has been revised.

33.    

#123: the reference has the wrong format (parsons, 2003) => [xx]

This part of the manuscript has been revised.

34.    

#127 "have individual impacts on EEDI. It means that changing…"

Corrected accordingly in the revised version.

35.    

#129: "the prime reason… at the 'Environmental cost' ": this sentence deserves more explanation.

Updated accordingly in the revised version

36.    

#132: specify which EEDI IMO or INLAND.

Corrected accordingly in the revised version

37.    

Table 7: EEDI is introduced and does not appears elsewhere in the manuscript. If it is EEDI_INLAND , it should be corrected.

Corrected accordingly in the revised version

38.    

Figure 2-10: specify (a) and (b) on fig 2 and add legend when necessary and make figures and numbers a bit more readable (larger typo).

Figures made clearer. However, these pictures are generated directly from Shipflow. Increasing the size of picture

39.    

#185: the range of 10-13% if refers to the 7,54%-12,12%-13,65% form tables 7-8-9, please say so and explain the 10-13% range if other criteria considered.

Corrected accordingly in the revised version

Comments from Reviewer-4

Reply from Authors

1.       

Line 36-37: We believe that authors must re-phrase because the conclusion is not correct. The comparison is CO₂ emission per transport unit between different freight transport modes. Inland ships CO₂ emission per transport unit is about half than other maritime transport.

Figure 1 was a wrong representation and I am sceptic about the rightness of the figure. Let me explain.

Sea going ships are more energy efficient is most cases, because they do not face the shallow water effect and other restrictions. For unrestricted voyage of sea going ships, it is possible to continue the journey for long time at the most efficient RPM of the engine. However, for inland ship, this is not possible, primarily because of the shallow water effect and river traffic. As a result, generally the CO₂ emission/tonne-km is higher for the case of inland ships.

We have used the figure shown in the following link in our previous research paper.

https://www.eea.europa.eu/data-and-maps/figures/specific-co2-emissions-per-tonne-2. This figure reflects the above justification.

This time, we have used

https://www.eea.europa.eu/data-and-maps/daviz/specific-co2-emissions-per-tonne-2#tab-chart_1. While using, I thought this is the updated one, as this one is till 2014. It was my mistake, which I should not overlook as a researcher. Actually, I could not think that similar updated figure reflects wrong assumption.

If you look into the both figures, it looks similar- only the latest one looked updated. However, updated data should be equal to previous data till 2011. Which does not match.

Therefore, I must say, I do not agree with the previous figure 1 now and corrected figure 1 is presented along with some supported literature review. 

2.       

Line 58-62: As from reference 7, EEDI formula described in MEPC Resolution 308 (73) may not be applicable to a ship having diesel-electric propulsion, turbine propulsion or hybrid propulsion system, except for cruise passenger ships and LNG carriers. Because the paper subject is for Inland Oil Tankers there is a need to explain why authors are describing this formula and if the inland ships propulsion method is known and take account in the research.

The main propulsion engine of inland oil tankers of Bangladesh is medium speed marine diesel engine. The EEDI formulation explained here to show the basic structure.

As you have mentioned, EEDI (by IMO) is not applicable for diesel-electric propulsion, turbine propulsion or hybrid propulsion system, except for cruise passenger ships and LNG carriers. The formulation is also not applicable for any inland ships. That’s why, necessary modification was necessary and it was explained in section 3.

3.       

Line 66 (table 1): Wrong description for parameter SFC_AE. AE means Auxiliary Engine

Corrected accordingly

4.       

Line 73 (table 2, row 1): What is the definition for shallow water? 5m, 10m, 20m? What is the distance that inland oil tankers are sailing in really shallow water? We strongly recommend to explain a little more why authors selected 60% for P_ME (empirical?)

Shallow water effect depends up on the ratio of river depth/ship draft. The higher the ratio is, the lower is the effect is.

This section updated accordingly.

5.       

Line 73 (table 2, row 2): Same like previous comment. Additionally, we strongly recommend authors to describe if shallow water effect is present at the inland ships of Bangladesh and why. If yes, in what percentage is present? In all voyages and for all vessels? Because no data is given, in our opinion this is not correct and probably it’s not truly correct to take account the shallow water effect.

Shallow water effect is a general fact for Bangladesh. Only 11.39% of total river channel of Bangladesh is over 3.66 meter. The effect has been explained in our previous research paper as reference in 12.

15 On board practical ship data taken were taken to find the average maximum continuous rating for inland ships of Bangladesh. Which is 60% for oil tanker. MCR and speed at the time of measurement is including the shallow water effect.

Yes, throughout the voyage, the shallow water effect was not same, it cannot be. However, since we have the practical ship operational data, we have calculated the open water speed at the same engine RPM. This has given us the unrestricted water ship speed. Thus, the shallow water effect on speed was found, which was on an average 20% on speed.

6.       

Line 73 (table 2, row 4, 5): Because oil refinery is not stable throughout years and it depends from the country, the oil refinery and the lots of oil, we strongly recommend the authors to explain a little more why they take account 0.76, because this Carbon content is very close to LNG, which is 0.75. Are there any specific chemical analyses of the fuel used? Diesel normally is from 0.8493 (HFO) to 0.8744 (MGO).

3 sample from different sources were collected and tested at Centre for Advanced Research in Science, University of Dhaka. This test procedure and results were presented in our previous paper as reference in 12.

7.       

Line 89-90: Please clarify the characterization well performed and poor performed vessels

This section has been revised

8.       

Line 90: “Sensitivity analysis has found the following results”. We strongly recommend authors to explain further the performed analysis. It is not well understood how the conclusions provided at bullets (line 91-101) were provided.

This section has been revised

9.       

Line 114-115: “for inland ships, Bangladesh has a restriction on length”. Please clarify this restriction.

This section has been revised

10.    

Line 138 (table 7): Is there a methodology used how and why authors proceed to these specific changes (improved design) or is it a result from the CFD software? Are the changes provided after an experimental method like continuously changes until best fit? For example, why “Water line length, LWL (meter)” changes to 55 and not 58 or 45?

Methodology and analysis explained in detailed in revised manuscript.

11.    

Line 149 (table 8): Same as above

Methodology and analysis explained in detailed in revised manuscript.

12.    

Line 161 (table 9): Same as above

Methodology and analysis explained in detailed in revised manuscript.

13.    

Line 179 (table 10): Please explain if this is an output from CFD software or how these numbers are found

These are the output of the CFD software.

14.    

Line 203: “a large quantity of fuel will be saved per trip”. Is it possible for authors to give an idea about the saved quantity of fuel per trip and from which data is provided the characterization “large quantity”?

The saving is proportional to the amount of the decrease in EEDI_INLAND value.

EEDI = . If new design, based on the suggestion reduces EEDI_INLAND value by 10% for same capacity and speed, it actually reduces the value of the product of . 10% reduction of this product actually implies more or less 10% fuel consumption. However, this analysis can be made more specific but is out of the scope of the paper.

15.    

For better understanding some more definitions must be provided. Please consider provide definition for inland oil tankers, shallow water, quantification of inland itineraries, comparison with no inland itineraries. In our point of view these are needed to document the conclusion “However, from the individual country’s perspective, the economic impact is considerably high” at line 201.

Requesting to allow me to work on this issue.

16.    

Finally, please consider to re-phrase the title “Possibility of CO2 emission reduction from Inland Oil Tankers Based on Revised EEDI Parameters” mainly due to the following two reasons:

Proposed Inland Oil Tanker Design of Bangladesh Focusing CO2 emission reduction Based on Revised EEDI parameters.

17.    

Currently there is no possibility for CO2 emission reduction because the inland oil fleet operating in Bangladesh is specific. So please use a different word for “Possibility”. Perhaps instead of “Possibility” use the phrase “Proposed scenario” or “Proposed policy”?

18.    

Because the research was specific for Bangladesh please enter this info in the title. Perhaps add the phrase “The case study of Bangladesh” at the end.