Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study compares the greenhouse gas (GHG) emissions and energy costs between a diesel-fueled catamaran and its fully electric counterpart operating on the same route. Here are some comments and suggestions on the abstract:

1.     Ensure the manuscript is free from grammatical errors and presented clearly, concisely, and professionally.

2.     The abstract mentions that shipping companies can use the study when evaluating options to reduce their emissions. It would be helpful to provide more detail about how this study can inform their decision-making. For instance, what specific decisions can be influenced by the findings?

3.     It's beneficial to provide references for the claims made in the introduction.

4.     In the introduction section, it's good to highlight the international and EU regulations related to carbon neutrality, but you could briefly explain why smaller ships are not subject to these regulations. A sentence or two providing context on why these regulations apply primarily to larger vessels could benefit readers unfamiliar with the topic.

5.     On page 2, lines 69-70: While you mention hydrogen and methanol as alternative fuels, it would be helpful to provide a brief overview of these options and their potential benefits and drawbacks. Also, discussing the state of development and adoption of these alternative fuels would add value.

6.     The authors have used diesel marine vessel in their research, but within your introduction and literature review, there was no mention of marine diesel vessels or engines. I recommend you also incorporate more relevant literature related to marine diesel vessels. Improve the texts and add more citations with the help of 10.1016/j.energy.2021.121837 and 10.1016/j.apr.2021.101258.

7.     On page 10, lines 331-334: The authors mentioned that no unique fuel alternative for all European countries and regions is essential. You could provide further insights into the importance of tailoring solutions to local conditions and how the EU's supportive measures (in the text) can facilitate this adaptation.

8.     What is the practical implication of this study for Japan? Discuss and explain the appropriate policies based on your research findings. Also, it would be valuable to briefly touch on the potential role of policy and regulations in encouraging the adoption of electric ferries. It is strongly recommended to add this as a sub-section before the conclusion.

Comments on the Quality of English Language

Ensure the manuscript is free from grammatical errors and presented clearly, concisely, and professionally.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

1. More result comparisons with references should be conducted for advantage discussion.

2. The whole structure should be improved. For this version, there is so much content expressing your experiments and basic principle, but not enough expression for your particular idea and methods.

3. The benefits and necessity of developing state estimation solution in such way should be described more clearly with more analysis.

4. Please explain more about the validation condition.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript compares GHG emissions of a diesel-fueled catamaran and its fully electric sister vessel that operates on the same line. The study shows that the GHG emissions of the electric vessel are only 25% of the diesel-powered sister vessel. The topic discussed in the submitted article is very interesting and valuable. However, I have found a few mistakes in the manuscript in English description and pointed out a few places for improvement. There are some obscure equations in the proposed control design process while the stability analysis should be proved in more detail. Besides, some statements in this study should be modified to match the suitable content with the other studies. They need to be checked and updated to make the content perfect.

Minor revision:

(1)        Some equations must be detailed for ease of checking.

(2)        What is “GHG” in Line 14 (Page 1) ? It should be defined before use.

(3)        The simulation study should be compared with previous results.

(4)        All figures must be revised to become professional and more clearly.

Major revision:

(5)        The introduction should be more detailed to show the advantages of this method with previous studies ?

(6)        The simulation study should be compared with previous results.

(7)        The methodology should be demonstrated more clearly ?

(8)        What will be solved with the results of this study ?

Comments on the Quality of English Language

Moderate editing of English language required

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Interesting paper, where a comparison of twin ferries but fitted with different propulsion systems, is done.

Introduction provides a brief legal scenario on emission rules for ships in EU and the world. IN literature review a wider scope can be done and some cited works are a little bit old.

In line 49, 67 and 264 an orthographic review is suggested.

Cite number 26 can be reviewed as published data for the year 2022, is not totally coincident with the comment on Belgium electricity costs.

Emission factors should be referenced and its election justified.

The discussion and final conclusions, only explain the results of  a payback time between the two propulsion options; no other mention is done.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have thoughtfully addressed all the reviewer's comments, so the manuscript is now deemed suitable for publication.

Author Response

The authors of the manuscript would like to give sincere thanks to the reviewer for his/her effort. We are grateful for the opportunity to publish.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript has been revised according to the comments of the reviewers. So it can be published in this journal.

Comments on the Quality of English Language

Minor editing of English language could be updated 

Author Response

The authors of the manuscript would like to give sincere thanks to the reviewer for his/her effort. We are grateful for the opportunity to publish.

Reviewer 4 Report

Comments and Suggestions for Authors

This time, the added text affords to explain better the context of the paper.

Only references 45 and 46 do not bring to the information. Maybe the addresses have been change. review please.

Author Response

The authors of the manuscript would like to give sincere thanks to the reviewer for his/her effort and also for the final remark.

We have reviewed the references and corrected them by the following:

45. Well-to-Wheels Analyses Available online: https://joint-research-centre.ec.europa.eu/welcome-jec-website/jec-activities/well-wheels-analyses_en (accessed on 26 October 2023).
46. Lo Vullo, E., Muntean, M., Duerr, M., Kona, A. and Bertoldi, P., Covenant of Mayors, European Commission, 2020, JRC119906.