Hydrogen-Enabled Microgrids for Railway Applications: A Seasonal Energy Storage Solution for Switch-Point Heating

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper focuses on the application of hydrogen-powered microgrids in railway turnout heating. A hydrogen energy storage system model incorporating photovoltaic, wind, and hybrid energy sources is constructed, and based on on-site climate and operational data, analyses are conducted on system energy flow, hydrogen production and storage, and economic performance. However, the paper presents deficiencies in theoretical innovation, model rationality, experimental validation, and practical applicability of the results. Specific comments are as follows:

1.The technical approach adopted in the paper is mainly the combination of a renewable energy microgrid based on photovoltaic and wind energy with hydrogen-based seasonal energy storage. This concept has been widely studied in existing literature, and the energy balance modeling and cost analysis methods used in the paper are general tools, without the proposal of new methods or key technologies. Although the study is combined with a railway scenario, conclusions are drawn merely through single-site simulation and static parameter comparison, which makes it difficult to reflect the uniqueness of the study or any methodological innovation.

2.Insufficient research significance, while the study mentions the role of hydrogen microgrids in railway turnout heating, it fails to address the specific demands of scenarios such as remote railway areas or non-electrified lines, including ensuring reliability under extreme climatic conditions. The paper lacks a clear discussion of existing research gaps related to fixed hydrogen microgrid applications in the railway sector, and does not articulate the core problem it aims to solve, resulting in inadequate justification and focus of the research.

3.The model construction lacks rigor and its applicability is questionable. In Sections 2.1 and 2.2, the rationality of the system energy balance method and the setting of renewable energy scenarios are not fully justified. For example, PV power generation simulation depends on regional climate data, but the error of this data for the study site is not discussed. The wind energy model is based on data from other test sites, without verification of how such approximation affects the results of this site. At the same time, the applicability boundary of the model under variable operating conditions (such as continuous extreme low temperature and long periods without sunlight) is not clearly defined, and the model's accuracy is not guaranteed.

4.The study mainly relies on simulation data and existing literature, lacking actual on-site data support. For example, the energy balance calculation of hydrogen production and storage is based on simulated renewable energy output and theoretical efficiency (electrolyzer 62%, fuel cell 43%), without comparison with operating data from actual installed microgrid systems. The data for the system economic analysis comes from supplier quotations, without verification based on long-term cost fluctuations (such as maintenance and hydrogen loss), making it difficult to fully prove its applicability in actual railway scenarios.

5.Disconnect between research results and practical implementation, chapters 3 and 4 present analyses on energy output, hydrogen balance, and cost composition under different energy scenarios, yet fail to connect these findings to the actual engineering needs of railway turnout heating systems. For instance, there is no discussion of emergency backup schemes for turnout heating. While the conclusion highlights the feasibility of hydrogen microgrids, it lacks a strong linkage to the core issue of "seasonal energy storage solutions" and does not adequately demonstrate how the proposed system addresses the seasonal demands of turnout heating. As such, the study does not offer effective guidance for real-world engineering implementation.

Author Response

Comments 1: The technical approach adopted in the paper is mainly the combination of a renewable energy microgrid based on photovoltaic and wind energy with hydrogen-based seasonal energy storage. This concept has been widely studied in existing literature, and the energy balance modeling and cost analysis methods used in the paper are general tools, without the proposal of new methods or key technologies. Although the study is combined with a railway scenario, conclusions are drawn merely through single-site simulation and static parameter comparison, which makes it difficult to reflect the uniqueness of the study or any methodological innovation.

Response 1: We thank the reviewer for this comment and acknowledge that while the underlying methods (energy balance modeling and cost analysis) are established tools, the contribution of this study lies in its novel application to stationary, safety-critical railway infrastructure, which remains an underexplored area in the hydrogen and microgrid literature. To clarify this, we have revised the Introduction (last two paragraphs, page 3) to better emphasize the study’s distinct focus and contribution. While the integration of photovoltaic, wind and hydrogen-based seasonal storage has been studied in general microgrid contexts, our work uniquely applies this to switch point heating systems in remote, non-electrified railway locations, using real-world operational demand data from an Austrian railway station. This represents a practical and safety-critical case distinct from typical residential or community microgrid studies. The majority of hydrogen research in the rail sector focuses on rolling stock propulsion or large-scale grid-connected systems. In contrast, stationary hydrogen microgrids designed for small, localized railway assets (e.g., switch point heating) remain largely absent from current literature. The paper also provides a site-specific, techno-economic baseline grounded in measured switch point heating demand and local climatic conditions, which serves as a replicable template for similar rural railway locations. While based on a single site, this approach aligns with early feasibility studies in the field, demonstrating practical design constraints, cost composition and sizing logic before moving toward broader multi-site or generalized optimization studies. These clarifications have been added to the end of the Introduction (last two paragraphs, page 3) to more explicitly articulate the study’s novelty and relevance. While we acknowledge that methodological innovation is not the primary focus of this work, its unique context and applied findings provide new insights into the decarbonization of safety-critical railway infrastructure and form a foundation for future optimization and pilot validation studies.

 

Comments 2: Insufficient research significance, while the study mentions the role of hydrogen microgrids in railway turnout heating, it fails to address the specific demands of scenarios such as remote railway areas or non-electrified lines, including ensuring reliability under extreme climatic conditions. The paper lacks a clear discussion of existing research gaps related to fixed hydrogen microgrid applications in the railway sector, and does not articulate the core problem it aims to solve, resulting in inadequate justification and focus of the research.

Response 2: We thank the reviewer for highlighting the need to more clearly articulate the research significance, specific challenges of remote railway applications, and the associated research gap. In the revised manuscript, we have strengthened these aspects in both the Introduction and Results sections. We explicitly emphasize that the study focuses on rural, non-electrified locations where grid extension is infeasible or economically unjustifiable, and where autonomous, resilient operation under extreme winter conditions is essential (Introduction: last two paragraphs, page 3). The revised text also clarifies that prior research in railway hydrogen integration has primarily focused on rolling stock propulsion and refueling infrastructure, while stationary hydrogen microgrids for auxiliary rail systems remain largely unexplored (Introduction: paragraph 4, page 2). Our study directly addresses this gap by presenting a site-specific feasibility analysis of a hydrogen-enabled microgrid designed for switch point heating, integrating real-world operational demand data and climate-driven energy modeling. Additionally, we explicitly state that the core challenge is the reliable, year-round, off-grid energy supply of switch point heating systems, which must bridge pronounced seasonal mismatches between summer renewable energy availability and winter demand (Introduction: last two paragraphs, page 3 & Section 3.1, paragraph 1, page 10). Hydrogen’s unique ability as a seasonal energy buffer is framed as central to addressing this challenge, complementing prior studies on hydrogen’s role in cold-climate microgrids but focusing it on a safety-critical, railway-specific context.

 

Comments 3: The model construction lacks rigor and its applicability is questionable. In Sections 2.1 and 2.2, the rationality of the system energy balance method and the setting of renewable energy scenarios are not fully justified. For example, PV power generation simulation depends on regional climate data, but the error of this data for the study site is not discussed. The wind energy model is based on data from other test sites, without verification of how such approximation affects the results of this site. At the same time, the applicability boundary of the model under variable operating conditions (such as continuous extreme low temperature and long periods without sunlight) is not clearly defined, and the model's accuracy is not guaranteed.

Response 3: We appreciate the reviewer’s observations regarding the assumptions and limitations of the modelling approach. We added a detailed discussion of the data sources, boundary conditions and known uncertainties in the new “Limitations and Future Work” section (paragraph 2, page 16). The PV generation model is based on long-term regional irradiance data (PVGIS), and the wind model uses conservative estimates from a database (Global Wind Atlas) in combination with the accumulated expertise from previous small wind turbine projects carried out at our institute due to the absence of on-site wind measurements. We also acknowledge that the current model uses average-year profiles without accounting for stochastic extremes. The revised paragraph now clarifies that the present concept study serves as a feasibility baseline, and that future work will include high-resolution simulations, probabilistic weather scenarios and site-specific data validation to enhance the model’s applicability and accuracy.

 

Comments 4: The study mainly relies on simulation data and existing literature, lacking actual on-site data support. For example, the energy balance calculation of hydrogen production and storage is based on simulated renewable energy output and theoretical efficiency (electrolyzer 62%, fuel cell 43%), without comparison with operating data from actual installed microgrid systems. The data for the system economic analysis comes from supplier quotations, without verification based on long-term cost fluctuations (such as maintenance and hydrogen loss), making it difficult to fully prove its applicability in actual railway scenarios.

Response 4: We thank the reviewer for highlighting the reliance on simulation data and literature-based assumptions. We agree that incorporating empirical validation would significantly strengthen the study. As this work is intended as an early-stage concept study, it primarily combines site-specific demand data with climate-based renewable generation simulations. Electrolyser and fuel cell efficiencies were selected based on conservative manufacturer specifications and validated against findings from relevant literature (see Discussion, paragraph 1, page 14). While we acknowledge that actual performance may vary under field conditions, these standardized values provide a necessary baseline for feasibility assessment prior to pilot implementation. Regarding the economic analysis, cost inputs for electrolyser, fuel cell and hydrogen storage components were derived from supplier quotations. We acknowledge that this does not yet incorporate long-term operational cost fluctuations. To address all this, the new "Limitations and Future Work" section (page 16) discusses the need for empirical validation (through the planned pilot project), incorporation of empirical OPEX data and component degradation rates, and inclusion of cost metrics in future work. These clarifications have been added to better contextualize this study’s scope as a preparatory step toward field trials and real-world validation.

 

Comments 5: Disconnect between research results and practical implementation, chapters 3 and 4 present analyses on energy output, hydrogen balance, and cost composition under different energy scenarios, yet fail to connect these findings to the actual engineering needs of railway turnout heating systems. For instance, there is no discussion of emergency backup schemes for turnout heating. While the conclusion highlights the feasibility of hydrogen microgrids, it lacks a strong linkage to the core issue of "seasonal energy storage solutions" and does not adequately demonstrate how the proposed system addresses the seasonal demands of turnout heating. As such, the study does not offer effective guidance for real-world engineering implementation.

Response 5: We thank the reviewer for this valuable observation. We agree that the original manuscript lacked explicit discussion on engineering-level implementation and redundancy. We have now added this aspect to the discussion section (end of paragraph 2, page 14) addressing practical backup strategies and system redundancy measures. Additionally, we clarified how the hydrogen system is explicitly designed to cover the highly seasonal nature of switch point heating loads in Section 3.1 (paragraph 1, page 10) and the Conclusion (page 16). These revisions strengthen the linkage between modelling results and real-world deployment scenarios for critical railway infrastructure.

Reviewer 2 Report

Comments and Suggestions for Authors

This manuscript investigates the feasibility of using a hydrogen-enabled microgrid to power switch point heating systems at a rural Austrian railway station. By integrating renewable energy and hydrogen-based seasonal storage, the system aims to replace conventional grid electricity. The results show that a PV-only configuration with hydrogen storage offers the most technically and economically viable solution under current site conditions. However, there are some concerns and suggestions that might help to improve the work.

 

1. The manuscript does not include a discussion of the energy management and control strategies necessary for the optimal operation of the proposed hydrogen-enabled microgrid. Effective microgrid performance requires advanced control schemes to coordinate generation, storage, and load. The absence of this discussion limits the technical depth of the paper. The following related paper can be compared (not mine): a: Hydrogen as the nexus of future sustainable transport and energy systems b: Dynamic optimal energy flow of integrated electricity and gas systems in continuous space

 

 

2. The structure shown in Figure 4 appears misleading, as it omits microgrid loads, which are a fundamental component of any microgrid system. A revised diagram should accurately reflect typical microgrid architecture, including various load types, dispatchable and non-dispatchable resources, and control interfaces.

 

3. Lifecycle cost (LCOE) and operational expenditure (OPEX) analysis are crucial for assessing long-term economic viability. Including discounted cash flow or net present value (NPV) comparisons would strengthen the economic assessment.

 

4. While reliability is critical in railway infrastructure, the current system configuration lacks detailed planning for redundancy.

 

5. The 5 kW electrolyser and 20 kW fuel cell are adopted without clear sensitivity analysis or optimization. The paper would benefit from a discussion on sizing methodology on total cost.

 

6. Hydrogen technology is not mature enough, so why can you include hydrogen for railway applications? Any justification?

 

7. The limitations of this study and the future research plan should be discussed at the end of this manuscript.

 

 

Author Response

Comments 1: The manuscript does not include a discussion of the energy management and control strategies necessary for the optimal operation of the proposed hydrogen-enabled microgrid. Effective microgrid performance requires advanced control schemes to coordinate generation, storage, and load. The absence of this discussion limits the technical depth of the paper. The following related paper can be compared (not mine): a: Hydrogen as the nexus of future sustainable transport and energy systems b: Dynamic optimal energy flow of integrated electricity and gas systems in continuous space

Response 1: We thank the reviewer for highlighting the absence of a discussion on microgrid control and energy management, which are indeed critical to optimal system operation. While the current study focuses on technical feasibility and energy balance modelling, we have now extended section 2.1 (last paragraph page 5 and first paragraph page 6) and added a new “Limitations and Future Work” part (last paragraph page 15 and following page) outlining the conceptual control framework that would govern real-time coordination between renewable generation, electrolysis, storage, fuel cell reconversion and load. This provides clearer insight into the system’s operational logic and lays the groundwork for future research involving dynamic modelling and control optimization, as suggested.

 

Comments 2: The structure shown in Figure 4 appears misleading, as it omits microgrid loads, which are a fundamental component of any microgrid system. A revised diagram should accurately reflect typical microgrid architecture, including various load types, dispatchable and non-dispatchable resources, and control interfaces.

Response 2: We thank the reviewer for pointing out the lack of clarity in Figure 4. The original figure was intended to show a simplified representation of seasonal energy shifting and not explicitly the detailed version of the microgrid, including loads and other resources, which as correctly noted are critical components of any microgrid design. We have therefore revised Figure 4 to accurately reflect a more complete architecture.

 

Comments 3: Lifecycle cost (LCOE) and operational expenditure (OPEX) analysis are crucial for assessing long-term economic viability. Including discounted cash flow or net present value (NPV) comparisons would strengthen the economic assessment.

Response 3: We appreciate the reviewers’ suggestions regarding lifecycle cost metrics and OPEX. In response, we have expanded Sections: 3.2 (last paragraph, page 12), Discussion (paragraph 2, page 14) and Limitations and Future Work (paragraph 3, page 16) as well as Table 2 to address these concerns. While a full LCOE or NPV analysis is not yet feasible at this concept stage due to the absence of operational data, we provide a preliminary evaluation of OPEX expectations based on literature sources. We also discuss typical lifetimes and availabilities for electrolyser, storage and fuel cell components. Importantly, we have also clarified that the primary objective of this study is not cost minimization, but rather to assess technical feasibility and autonomous operation of switch heating in off-grid railway environments. In this context, self-sufficiency and grid independence are prioritized and moderate additional cost is considered acceptable. We also outline a future plan to incorporate full LCOE and NPV comparisons based on real-world operational data in follow-up implementation phases.

 

Comments 4: While reliability is critical in railway infrastructure, the current system configuration lacks detailed planning for redundancy.

Response 4: We agree with the reviewer’s assessment that system reliability is a key concern for railway infrastructure. In response, we have added a paragraph in the Discussion section (end of paragraph 2, page 14) outlining redundancy measures to enhance system robustness.

 

Comments 5: The 5 kW electrolyser and 20 kW fuel cell are adopted without clear sensitivity analysis or optimization. The paper would benefit from a discussion on sizing methodology on total cost.

Response 5: Although this approach provides a feasible and technically justified setup, it is based on static conditions and lacks dynamic optimization. We expanded section 3.2 (last paragraph, page 10) to clarify our sizing methodology. The absence of a sensitivity analysis represents a limitation, particularly regarding how changes in component sizing might affect capital costs, storage duration and overall system efficiency. Future work (first paragraph, page 16) will include simulation-based optimization of the fuel cell and electrolyser dimensions across different weather years and load profiles. This will enable better understanding of cost-performance trade-offs and system flexibility under real-world uncertainty.

 

Comments 6: Hydrogen technology is not mature enough, so why can you include hydrogen for railway applications? Any justification?

Response 6: We thank the reviewer for pointing out the issue of hydrogen maturity. We have added a short justification in the Discussion (last paragraph page 14 and following), referencing typical lifetimes and availabilities for electrolyser and fuel cell components and emphasizing the relative simplicity of stationary applications as a lower-barrier starting point for hydrogen integration into the railway infrastructure.

 

Comments 7: The limitations of this study and the future research plan should be discussed at the end of this manuscript.

Response 7: Thank you for your constructive recommendation. We added a dedicated section titled “Limitations and Future Work” at the end of the discussion chapter. This section systematically addresses the key limitations raised throughout the review process. It also outlines future research directions such as optimization, validation, scalability studies, financial metrics and control strategies, to guide the continued development and deployment of hydrogen-based microgrids for railway infrastructure. This addition enhances the transparency, scope, and practical relevance of the manuscript.

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript addresses a timely and important topic related to the integration of renewable energy and hydrogen-based seasonal storage into railway infrastructure. The work is well aligned with the goals of sustainability and decarbonization, and the technical approach is generally solid. However, several key aspects require clarification, expansion, or correction. I recommend major revisions before this paper can be considered for publication.

1. Lack of empirical or experimental validation
   The study relies entirely on theoretical simulations and modeling. While this may be acceptable for a concept study, some degree of validation—either through laboratory-scale results, real-world data from similar systems, or benchmarking against field trials—would significantly strengthen the credibility of the conclusions. Please consider integrating some form of validation or comparative data.
2. Missing discussion of operational costs and system lifetime
   The manuscript thoroughly analyzes capital expenditure (CAPEX), but omits operational expenditure (OPEX), maintenance expectations, and system durability over time. This is a critical gap, especially given the long-term nature of seasonal storage. I suggest including at least a preliminary assessment of OPEX and a brief discussion on lifecycle sustainability (e.g., system lifespan, degradation, replacement intervals).
3. No treatment of redundancy or system reliability
   Given that the proposed system powers a safety-critical railway application (switch point heating), the absence of any discussion on fault tolerance, redundancy, or backup energy sources (e.g., grid fallback or emergency generators) is a significant oversight. Please add a paragraph outlining possible measures to ensure continuous operation under unexpected conditions or system failure.
4. Limited scalability and generalizability
   The study focuses on a single, very specific site. The general applicability of the findings to other railway stations or climate regions is not addressed. A brief sensitivity analysis (e.g., for energy demand, PV yield, wind speed) or discussion on how the design could be adapted to other locations would add significant value.
5. Lack of comparative economic performance metrics
   Although CAPEX is detailed, the manuscript does not include key performance indicators such as Levelized Cost of Energy (LCOE), payback period, or Net Present Value (NPV). Including at least one of these metrics would enable a clearer economic comparison between the proposed hydrogen solution and traditional alternatives (e.g., diesel or grid-based heating).
6. Environmental benefits not quantified
   The system is described as "sustainable", but no quantification of CO₂ emissions avoided is presented. I recommend estimating the greenhouse gas emissions saved by replacing conventional energy sources, to support claims related to decarbonization and sustainability.
7. Additional clarifications and improvements

• The abstract could be revised to emphasize more clearly the novelty of the work, particularly the use of hydrogen for stationary railway infrastructure.
• Some figures (e.g., Figure 9) are difficult to interpret at low resolution – consider improving their clarity or resolution.
• Ensure consistent terminology throughout the manuscript (e.g., “compressed hydrogen,” “CH₂,” “pressurized storage”).
• The detailed climate discussion in Section 2.3 is useful but could be moved to the Discussion section or condensed for better flow.

This paper has strong potential but requires major revisions to improve its scientific rigor and practical applicability. I encourage the authors to address the points above carefully in their revised version and to provide a point-by-point response upon resubmission.

Author Response

Comments 1: Lack of empirical or experimental validation: The study relies entirely on theoretical simulations and modeling. While this may be acceptable for a concept study, some degree of validation—either through laboratory-scale results, real-world data from similar systems, or benchmarking against field trials—would significantly strengthen the credibility of the conclusions. Please consider integrating some form of validation or comparative data.

Response 1: We fully agree with the reviewer’s observation that the study lacks experimental validation. We clarified our comparison to results from similar hydrogen microgrid studies in the literature (paragraph 1, page 14), thereby reinforcing the validity and relevance of the proposed design. Further, we have explicitly acknowledged this limitation in a new “Limitations and Future Work” section and clarified that future steps include validating the model with operational data and pilot testing (section 4.1, paragraph 2, page 15). While the current work is intended as a feasibility and design concept, we recognize the need to benchmark or compare against field data to increase practical credibility.

 

Comments 2: Missing discussion of operational costs and system lifetime: The manuscript thoroughly analyzes capital expenditure (CAPEX), but omits operational expenditure (OPEX), maintenance expectations, and system durability over time. This is a critical gap, especially given the long-term nature of seasonal storage. I suggest including at least a preliminary assessment of OPEX and a brief discussion on lifecycle sustainability (e.g., system lifespan, degradation, replacement intervals).

Response 2: We appreciate the reviewer’s important observation regarding the omission of operational expenditure (OPEX) and lifecycle considerations. In the revised manuscript, we have expanded Sections: 3.2 (last paragraph page 12), Discussion (paragraph 2 & 3, page 14) as well as Table 2 to address these concerns. We have also clarified that the primary objective of this study is not cost minimization, but rather to assess technical feasibility and autonomous operation of switch heating in off-grid railway environments.

 

Comments 3: No treatment of redundancy or system reliability: Given that the proposed system powers a safety-critical railway application (switch point heating), the absence of any discussion on fault tolerance, redundancy, or backup energy sources (e.g., grid fallback or emergency generators) is a significant oversight. Please add a paragraph outlining possible measures to ensure continuous operation under unexpected conditions or system failure.

Response 3: We thank the reviewer for this important observation. We agree that system reliability and fault tolerance are crucial, particularly for safety-relevant infrastructure like switch point heating. In response, we have added a paragraph to the discussion section (end of paragraph 2, page 14) outlining feasible redundancy strategies. These considerations will be essential in future pilot deployment stages to ensure continuous and resilient system operation.

 

Comments 4: Limited scalability and generalizability: The study focuses on a single, very specific site. The general applicability of the findings to other railway stations or climate regions is not addressed. A brief sensitivity analysis (e.g., for energy demand, PV yield, wind speed) or discussion on how the design could be adapted to other locations would add significant value.

Response 4: We appreciate the reviewer’s comment on the need to address the generalizability of our findings. While our case study is site-specific, we have now included a dedicated paragraph in the new “Limitations and Future Work” section (paragraph 2, page 16) discussing how the proposed system could be adapted to other railway sites with different climatic and operational profiles. We also briefly highlight sensitivity to key variables like solar irradiation, wind speed and heating demand. These considerations enhance the study’s broader applicability and pave the way for future multi-site evaluations.

 

Comments 5: Lack of comparative economic performance metrics: Although CAPEX is detailed, the manuscript does not include key performance indicators such as Levelized Cost of Energy (LCOE), payback period, or Net Present Value (NPV). Including at least one of these metrics would enable a clearer economic comparison between the proposed hydrogen solution and traditional alternatives (e.g., diesel or grid-based heating).

Response 5: We appreciate the reviewers’ suggestions regarding lifecycle cost metrics. While a full LCOE or NPV analysis is not yet feasible at this concept stage due to the absence of operational data, we provide a preliminary evaluation of OPEX expectations and component durability and typical lifetimes based on literature sources (see Comments 2). Importantly, we have also clarified that the primary objective of this study is not cost minimization, but rather to assess technical feasibility and autonomous operation of switch heating in off-grid railway environments. In this context, self-sufficiency and grid independence are prioritized, and moderate additional cost is considered acceptable. We also outline a future plan to incorporate full LCOE and NPV comparisons (paragraph 3, page 16) based on real-world operational data in follow-up implementation phases.

 

Comments 6: Environmental benefits not quantified: The system is described as "sustainable", but no quantification of CO₂ emissions avoided is presented. I recommend estimating the greenhouse gas emissions saved by replacing conventional energy sources, to support claims related to decarbonization and sustainability.

Response 6: Thank you for this important comment. We have now added a preliminary environmental impact estimate that quantifies the CO₂ emissions avoided through the deployment of the hydrogen-enabled microgrid compared to a grid electricity scenario. The values have been included in the Discussion section (paragraph 2, page 15) to support our sustainability claims.

 

Comments 7: Additional clarifications and improvements: The abstract could be revised to emphasize more clearly the novelty of the work, particularly the use of hydrogen for stationary railway infrastructure. Some figures (e.g., Figure 9) are difficult to interpret at low resolution – consider improving their clarity or resolution. Ensure consistent terminology throughout the manuscript (e.g., “compressed hydrogen,” “CH₂,” “pressurized storage”). The detailed climate discussion in Section 2.3 is useful but could be moved to the Discussion section or condensed for better flow. This paper has strong potential but requires major revisions to improve its scientific rigor and practical applicability. I encourage the authors to address the points above carefully in their revised version and to provide a point-by-point response upon resubmission.

Response 7: Thank you for these valuable suggestions. We have revised the abstract to more clearly emphasize the novelty of applying hydrogen microgrids to stationary railway applications. The figures have been checked for clarity and resolution and updated if necessary and we have carried out a comprehensive check to ensure standardised terminology. Furthermore, we appreciate the reviewer’s suggestion and agree that the climate discussion is detailed. However, we have chosen to retain it in Section 2.3 because it provides essential context for understanding the site-specific boundary conditions that directly influence energy demand, renewable generation potential and system design. Presenting this information upfront allows readers to better interpret subsequent modelling assumptions and results. Moreover, since the climate section is structured as a standalone subchapter, it can be easily skipped by readers who are already familiar with regional climatic conditions, thereby preserving readability. We believe that keeping this section in its current position supports transparency regarding input data and enhances the reproducibility of the study, which is critical for similar applications in other regions.

 

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Upon reviewing the revised version of the manuscript, I am pleased to note that the authors have fully and appropriately addressed all the suggestions and comments made during the previous round of review. The revisions have significantly improved the clarity, coherence, and scientific rigor of the work. In light of these enhancements, I believe the manuscript is now suitable for publication in its current form, and I recommend its acceptance without further revisions