Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

n this manuscript, the authors reported on H₂ production at a Colombian oil-field CPF by running a PEM electrolyzer on excess power from two 20-MW gas turbines and employing treated generated water as feed. This study is interesting and well demonstrated, therefore I recommend its publication in Sci after the following minor revisions.

1. I suggest the authors should strengthen the introduction section and briefly explain the novelty of their study and compare with most recently reported PEM studies.
2. In page 13, It should be better if the authors could explain that how the 2-3% efficiency increase, mention the heat source /temperature used and demonstrate briefly how they measured the gain.
3. In page 17-18, what the authors means by electrical exergy/surplus exergy? Also mention whether the productivity of 345-350 kg H₂/MW. Day assumes to be a continuous operation of   24 h
4. The first paragraph of the introduction maybe polished in a more technical and precise way. Some useful related studies, such as Inorganic. Chem. Front., 2025, 12, 1329-1348, 1021/prechem.5c00082, Chem. Rec. 2024, 24, e202400127 may be cited.
5. The manuscript should be thoroughly check for any typos errors. For example, in the abstract (line 26), H₂should be written with subscript notation H₂.

 

Comments for author File: Comments.pdf

Author Response

Dear Reviewer:

Please see the enclosed file.

Kind regards,

The authors

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The comments are attached

Comments for author File: Comments.pdf

Author Response

Dear Reviewer:

Please see the enclosed file.

Kind regards,

The authors

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The authors address an interesting and topical topic, which falls within the issue of energy transition.

It is a complete study, justified by specific calculations for various scenarios, which leads to the usefulness of this study for this field.

The approach and solution to the problem analysed in this paper makes it possible to translate knowledge from the area of electrochemical processes for energy production to the area of its use.

Specify the bibliographic reference for Figure 2.

Write the indices of chemical substances correctly (NOx, SO2, etc.).

Use the separator for numbers correctly (the comma and the period have different meanings in English).

The conclusions must be better structured in the context of the paper's objectives and the results presented and discussed in the paper.

Respect the way of writing the bibliography according to the journal's instructions.

Author Response

Dear Reviewer:

Please see the enclosed file.

Kind regards,

The authors

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors

for authors

Although the manuscript is technically detailed, the authors should more clearly articulate their novel contributions in relation to existing studies. Several studies have addressed surplus power utilization and electrolysis integration. Therefore, the introduction should explicitly emphasize this.

 

1) the uniqueness of using field-measured gas turbine surplus data rather than modeled profiles,

 

- the produced-water reuse pathway validated to PEM specifications;

 

the identification of the combined technical, operational, and economic threshold (approximately 3 MW) under real oilfield conditions.

2. Justification of “Green” or “Low-Carbon” Hydrogen Classification

The electricity source is gas-fired turbines. Although surplus energy is used, the manuscript should clarify:

• Whether the produced hydrogen is better classified as low-carbon rather       than green hydrogen,
• The associated specific CO₂ emissions (kg CO₂/kg H₂), or at least a comparative emissions discussion versus grid-powered electrolysis or SMR.
  A simple emissions intensity estimate would significantly enhance the environmental credibility of the work.

3.Water Quality Requirements for PEM Electrolysis
The manuscript reports treated water conductivity <5 µS/cm, whereas several PEM manufacturers and standards indicate requirements closer to ≤1 µS/cm.
The authors should:

• Clarify whether the stated value is sufficient for the selected PEM systems,
• Cite manufacturer datasheets explicitly,
• Discuss potential long-term membrane degradation risks associated with operating at higher conductivity.

4.SWOT / EFE / IFE Methodology Transparency
The SWOT-based selection of PEM over alkaline electrolysis is interesting, but the methodology lacks transparency. The authors should:

• Clearly define weighting factors, scoring criteria, and normalization procedures,
• Explain how experimental data were quantitatively integrated into the matrices,
• Consider including a brief sensitivity check to reduce subjectivity concerns.

5-Units and Consistency

• Ensure consistent use of units (Nm³ vs Nm³/h, MW vs kW, MMCFD vs MMpcd).

• Clearly distinguish between instantaneous capacity and daily production rates.

 

Author Response

Dear Reviewer:

Please see the enclosed file.

Kind regards,

The authors

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors addressed my comments and the current manuscript is ready for publication.

Reviewer 4 Report

Comments and Suggestions for Authors

The authors addressed all reviewers’ comments point by point