Hydrogen: Prospects and Criticalities for Future Development and Analysis of Present EU and National Regulation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper titled “Hydrogen: prospects and criticalities for future development and analysis of present EU and national regulation” offers a truly comprehensive account on recent and predicted future policy regarding regulation of hydrogen production, transport and utilization in the EU. It is written in clear English and is easy to read, despite the complexity of the subject. Each of the separate chapters is focused on a specific viewpoint regarding the technological considerations of hydrogen, and the presented facts are objective and critical, to the best of my knowledge. One drawback is that, perhaps the review is too comprehensive and would have benefitted from being trimmed down, but I could not recommend removing anything at this point. I think the paper should be published after minor formatting revisions.

Some of my comments and observations are mainly related to the formatting of the paper:

·         The references are not in order. Firstly, ref [29] is mentioned in l. 76 after only [1] and [2]. Ref [7] (l. 117) is followed by ref. [10] (l. 127), while s [8] and [9] are mentioned in l. 232 – 233. Then, in the discussion of chapter 1, l. 284 the reference is [28]. The next reference is in Table 1, and it is numbered [115]. [29] resumes only in l. 576. This should be checked and fixed.

·         Tables 1 and 2 are not mentioned in the discussion.

·         l. 540 – [44] is referenced twice. Also, I could not find refs [144] and [145].

·         l. 568 – 569 NH3 and H2 should be subscript.

·         Figure 2 is very low resolution, should be improved if possible.

·         l. 669 – 672 formatting is broken.

·         l. 692 – “Potentially interesting developments could occur in the maritime sector where, however, there are further problems tied to safety and energy density.” Unclear sentence, seems like there is surplus or missing text.

·         l. 711 – reference formatting.

·         l. 889 – reference [0] probably something missing.

·         Figure 13 is too far away (over two pages) from where it is first mentioned.

·         l. 1055 I believe CAPEX and OPEX are not explained.

·         l. 1194 “Aim of the following of the present section…”

Author Response

• The references are not in order. Firstly, ref [29] is mentioned in l. 76 after only [1] and [2]. Ref [7] (l. 117) is followed by ref. [10] (l. 127), while s [8] and [9] are mentioned in l. 232 – 233. Then, in the discussion of chapter 1, l. 284 the reference is [28]. The next reference is in Table 1, and it is numbered [115]. [29] resumes only in l. 576. This should be checked and fixed.

Done

• Tables 1 and 2 are not mentioned in the discussion.

Done

• l. 540 – [44] is referenced twice. Also, I could not find refs [144] and [145].

Problem on [44] was fixed. Reference [144] is quoted at I. 510. Reference [145] is a database: it is not explicitly referred in the text but, yet, it can be considered as an important reference on the subject.

• l. 568 – 569 NH3 and H2 should be subscript.

Done

• Figure 2 is very low resolution, should be improved if possible.

Done

• l. 669 – 672 formatting is broken.

The remark is not clear: the formatting seems ok.

• l. 692 – “Potentially interesting developments could occur in the maritime sector where, however, there are further problems tied to safety and energy density.” Unclear sentence, seems like there is surplus or missing text.

Fixed: now it should be clearer

• l. 711 – reference formatting.

Done

• l. 889 – reference [0] probably something missing.

Done

• Figure 13 is too far away (over two pages) from where it is first mentioned.

Fixed

• l. 1055 I believe CAPEX and OPEX are not explained.

The acronyms are now introduced

• l. 1194 “Aim of the following of the present section…”

Modified in “Aim of the following part of the present section…”, maybe clearer

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript provides a comprehensive overview of hydrogen-related technologies and their applications, contributing valuable insights to the field of sustainable energy. The paper is well-researched and offers significant potential to guide future research and industry practices. However, there are some areas where the manuscript could be improved to enhance its clarity and impact. The paper can be accepted for publication after minor revisions. Specific comments are given below:

1.        The manuscript contains several lengthy sections that could be divided into subsections. This would improve readability and help readers follow the paper's structure more easily.

2.        A high number of abbreviations are used in the manuscript, which can interrupt the reading flow. The authors should limit the use of abbreviations to the most essential terms and ensure that each abbreviation is clearly defined upon its first use.

3.        The paper includes a significant amount of popular science content, which, while interesting, sometimes deviates from the academic focus. As this is an academic paper, it would be beneficial to reduce or eliminate these sections to maintain the scientific rigor and focus of the manuscript.

4.        While the paper thoroughly covers hydrogen production technologies and usage scenarios, the discussion on relevant regulations is somewhat lacking. A more detailed examination of regulatory frameworks would strengthen the manuscript and provide a more comprehensive perspective on the challenges and opportunities in the field.

Author Response

1. The manuscript contains several lengthy sections that could be divided into subsections. This would improve readability and help readers follow the paper's structure more easily.

Subsections have been created in those long chapters where this was possible (regulation and hydrogen as an energy vector).

2. A high number of abbreviations are used in the manuscript, which can interrupt the reading flow. The authors should limit the use of abbreviations to the most essential terms and ensure that each abbreviation is clearly defined upon its first use.

The number of abbreviations is section 6, where a wide spectrum analysis of the hydrogen production technologies is carried out. Unfortunately, replacing the acronyms with full text would only make reading more complex and not add clarity. We are conscious that section 6 is dense, but we also hope it can serve as a synthetic reference for those who are interested in the subject.

3. The paper includes a significant amount of popular science content, which, while interesting, sometimes deviates from the academic focus. As this is an academic paper, it would be beneficial to reduce or eliminate these sections to maintain the scientific rigor and focus of the manuscript.

We disagree with this remark. The difference in tones (some chapters are more technical than others) is due to the subject: explaining hydrogen production technologies is not the same as describing problems related to the implementation of a hydrogen market. We are confident that in the diversity of the topics the reader can find an all-round picture of all the issues tide with hydrogen.

4. While the paper thoroughly covers hydrogen production technologies and usage scenarios, the discussion on relevant regulations is somewhat lacking. A more detailed examination of regulatory frameworks would strengthen the manuscript and provide a more comprehensive perspective on the challenges and opportunities in the field.

We agree that regulation could be treated much more in detail, but this would require, maybe, a dedicated book, which is not the aim of the present paper. The regulation section is already one of the longest in the paper and synthetically treats both the pan-European prospect and the national views. A more detailed explanation would require to enter into details of the differences between national regulations, interesting but complicated topic which would require much more space and maybe appeal only a few interested people.