Hydrogen and Ammonia Production and Transportation from Offshore Wind Farms: A Techno-Economic Analysis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Please check the attached file for more information.

The authors should rewrite the paper to make it more readable, especially section 3, methodology.  Please support your statements, data, equations with suitable references. 

The results, charts (for example, figure 6) are not clear to me.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Please improve your English.

Author Response

Comment 1: Please check the attached file for more information

Response 1: Done

Comment 2: The authors should rewrite the paper to make it more readable, especially section 3, methodology.  Please support your statements, data, equations with suitable references. 

Response 2: 

We have revised Section 3 (now section 2) to enhance its clarity and readability and resolved some formatting issues. The improvements include a reorganized methodology for better logical flow. Also, we have thoroughly reviewed the manuscript and added relevant references to support key equations and statements. Some of the information are still included in the supplementary material.

Comment 3: 

The results, charts (for example, figure 6) are not clear to me.

Response 3: 

We have improved the figures and results section to improve clarity. For instance, Figure 6 now illustrates more clearly the Levelized Cost of Transport for Hydrogen (LCOTH₂) as a function of distance to shore, comparing pipeline and liquefied hydrogen (LH₂) tanker transport. It highlights the cost-effectiveness of pipelines for short distances (≤500 km) and the economic advantage of LH₂ tankers at longer distances (>1000 km), due to lower incremental costs per kilometer. We hope the clarity of the figures is now satisfying.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This paper provides valuable insights into the technical-economic analysis of hydrogen and ammonia production and transportation, but there is still room for improvement in cost analysis, formula calculations, and technical feasibility. In addition, the English level of papers and the format of references also need to be further optimized. It is suggested that the author address the above issues in the revised version to improve the academic quality and readability of the paper.

1. The paper mentions that the production cost of green hydrogen is €28-12.68/kg, while the cost of grey hydrogen is €1-2 /kg. However, the paper does not discuss in detail the composition of these costs, in particular whether the high cost of green hydrogen comes mainly from the capital expenditure (CAPEX) or operating expenditure (OPEX) of the electrolyzer. A further breakdown of costs is recommended to better understand the economics of green hydrogen production.
2. The paper mentions the high cost of ammonia production, but does not elaborate on how the cost of ammonia production compares to the cost of hydrogen production. In particular, the production of ammonia involves the Haber-Bosch process, which has high energy consumption and cost, and it is recommended to further analyze the difference between the production cost of ammonia and the production cost of hydrogen, especially the cost changes under different electrolytic cell capacities.
3. The paper compares the cost of pipeline and sea transport, but does not fully consider the cost change for different distances. While the paper mentions that pipelines are more cost-effective at short distances (<500 km), sea freight is more advantageous at long distances (>1000 km). Further analysis of cost changes at different distances is recommended, especially at the intersection of pipeline and sea transport (i.e. when sea transport becomes more cost-effective).
4. The paper mentions the high cost of transporting liquefied hydrogen (LH₂), but does not discuss in detail the energy consumption and costs involved in the liquefaction process. The transportation of liquefied hydrogen involves three links: liquefaction, storage and transportation. It is suggested to further decompose the cost of these links, especially the energy consumption and cost in the liquefaction process.
5. The LCOH₂ calculation in formula (1) takes into account CAPEX, OPEX, and DECEX, but does not specify the exact composition of these costs. Further breakdown of these costs is recommended, particularly for electrolyzers, desalination equipment and compressors.
6. The pipe cost calculation in formula (7) is based on the electrolytic cell capacity, but does not detail the effect of pipe diameter and flow rate on the cost. It is suggested to further analyze the influence of pipe diameter and flow rate on the cost, especially the cost variation under different cell capacity.
7. It is mentioned that the capacity factor of the electrolyzer has an important effect on the production cost, but how to optimize the capacity factor of the electrolyzer is not discussed in detail. Further analysis is recommended on how to improve the capacity factor by optimizing the operating time of the electrolyzer (e.g., taking advantage of the volatility of wind power), thereby reducing production costs.
8. The paper mentions the high energy consumption of the Haber-Bosch process, but does not discuss in detail how energy consumption can be reduced through technical improvements, such as the use of novel catalysts. It is suggested to further analyze the energy consumption optimization potential of Haber-Bosch process.
9. The format of the references in the paper is inconsistent. It is recommended that newer references be used whenever possible, especially in areas where technology is developing rapidly.
10. The chart in the paper (Figure 3 and Figure 4) is not clear enough, especially the label and annotation of the chart are not detailed enough. It is recommended to increase the clarity and annotations of the chart so that readers can better understand the content of the chart.

Comments for author File: Comments.pdf

Author Response

Comment 1: This paper provides valuable insights into the technical-economic analysis of hydrogen and ammonia production and transportation, but there is still room for improvement in cost analysis, formula calculations, and technical feasibility. In addition, the English level of papers and the format of references also need to be further optimized. It is suggested that the author address the above issues in the revised version to improve the academic quality and readability of the paper.

1. The paper mentions that the production cost of green hydrogen is €8-12.68/kg, while the cost of grey hydrogen is €1-2 /kg. However, the paper does not discuss in detail the composition of these costs, in particular whether the high cost of green hydrogen comes mainly from the capital expenditure (CAPEX) or operating expenditure (OPEX) of the electrolyzer. A further breakdown of costs is recommended to better understand the economics of green hydrogen production.

Response 1: We have added information about the cost breakdown of green hydrogen, identifying the key drivers impacting the cost of production of green hydrogen. For instance, CAPEX of electrolyzer has significant impact in addition to the renewable electricity prices.

1. Comment 2: 2The paper mentions the high cost of ammonia production, but does not elaborate on how the cost of ammonia production compares to the cost of hydrogen production. In particular, the production of ammonia involves the Haber-Bosch process, which has high energy consumption and cost, and it is recommended to further analyze the difference between the production cost of ammonia and the production cost of hydrogen, especially the cost changes under different electrolytic cell capacities.

Response 2: We have compared the production costs of hydrogen and ammonia, analysing the key factors influencing their levelized costs. Figures 3 and 4 illustrate the differences between the Levelized Cost of Hydrogen (LCOH₂) and the Levelized Cost of Ammonia (LCOA), expressed in both mass and energy terms, while varying the electrolyser capacity in MW. The description of figure 4 is updated accordingly to better explain comparison of the production costs.

 

The distinction between LCOH₂ and LCOA primarily arises from the additional components in the ammonia production process, including the Air Separation Unit (ASU), the Haber-Bosch synthesis.

Moreover, the energy consumption of Haber-Bosch loop is not considered because it is considered negligible compared to the hydrogen production since it is around 0.7-0.8 kWh/kgNH₃ [M. Fasihi, R. Weiss, J. Savolainen, and C. Breyer, “Global potential of green ammonia based on hybrid PV-wind power plants,” Appl. Energy, vol. 294, p. 116170, Jul. 2021, doi: 10.1016/j.apenergy.2020.116170.].

1. Comment 3: The paper compares the cost of pipeline and sea transport, but does not fully consider the cost change for different distances. While the paper mentions that pipelines are more cost-effective at short distances (<500 km), sea freight is more advantageous at long distances (>1000 km). Further analysis of cost changes at different distances is recommended, especially at the intersection of pipeline and sea transport (i.e. when sea transport becomes more cost-effective).

Response 3: Figures 6 (now 11 after the sensitivity analysis) and 9 (now 14) analyze the Levelized Cost of Transport (LCOT) as a function of the distance to shore, considering different electrolyser capacities. These figures also highlight the trade-off points as the intersection points where pipeline and sea transport costs are equal for various electrolyser capacities. These points help identify the distance at which one transport method becomes more cost-effective than the other.

1. Comment 4: The paper mentions the high cost of transporting liquefied hydrogen (LH₂), but does not discuss in detail the energy consumption and costs involved in the liquefaction process. The transportation of liquefied hydrogen involves three links: liquefaction, storage and transportation. It is suggested to further decompose the cost of these links, especially the energy consumption and cost in the liquefaction process.

Response 4: In Equation 8, the ship CAPEX has been divided into three sub-CAPEX components: liquefaction, storage, and ship costs. The transportation CAPEX is included within the storage CAPEX, where the tanker capacity (T_cap) is defined as a function of the distance (Equation 10). In Equation 9, the CAPEX for the liquefaction process is presented.

The energy consumption is included in the OPEX as mentioned in Table 9 of the supplementary materials.

The equations for calculation of CAPEX for storage and liquefactions is mentioned in section 3.2.2 of the manuscript.

1. Comment 5: The LCOH₂ calculation in formula (1) takes into account CAPEX, OPEX, and DECEX, but does not specify the exact composition of these costs. Further breakdown of these costs is recommended, particularly for electrolyzers, desalination equipment and compressors.

Response 5: The supplementary material has been revised to include the details of CAPEX, OPEX and DECEX used in the LCOH₂ and LCOA equation.  OPEX as a percent of CAPEX is given in Table 1 in the methodology section of the manuscript. For the clarity of readers, we have mentioned that this is detailed in the supplementary material in the methodology section.

However, the CAPEX of compressors are included in the pipeline costs calculation for both hydrogen (section 2.2.1) and ammonia (section 2.3.1).

1. Comment 6: The pipe cost calculation in formula (7) is based on the electrolytic cell capacity, but does not detail the effect of pipe diameter and flow rate on the cost. It is suggested to further analyze the influence of pipe diameter and flow rate on the cost, especially the cost variation under different cell capacity.

Response 6: In Equation 6, the flow rate is defined as the electrolyser capacity multiplied by the production rate of the electrolyser (0.0055 kg/s/MW), for various electrolyser capacities.

The diameter is then calculated using Equation 3, assuming a fixed density of 8 kg/m³ and a velocity of 15 m/s. As a result, the diameter varies with the electrolyser capacity, ranging from 0.0936 m (E_cap = 100 MW) to 0.53 m (E_cap = 5000 MW).

1. Comment 7: It is mentioned that the capacity factor of the electrolyzer has an important effect on the production cost, but how to optimize the capacity factor of the electrolyzer is not discussed in detail. Further analysis is recommended on how to improve the capacity factor by optimizing the operating time of the electrolyzer (e.g., taking advantage of the volatility of wind power), thereby reducing production costs.

Response 7: We conduct an optimization analysis for the electrolyser sizing, considering only the case where the wind farm is off grid. In addition to the case in which the electrolyzer is sized equal to the power of the wind farm, the cases in which the electrolyzer is sized equal to 90% and 80% of the power of the wind farm were considered. This led to an increase in the LCOH₂, since, as previously mentioned, the plant is disconnected from the grid and therefore the excess power coming from the farm is not sold or valorised in any other way. This is not shown in the manuscript, but it is mentioned in the method section. For the reviewer knowledge, here below a graph showing the obtained results.

 

1. Comment 8: The paper mentions the high energy consumption of the Haber-Bosch process, but does not discuss in detail how energy consumption can be reduced through technical improvements, such as the use of novel catalysts. It is suggested to further analyze the energy consumption optimization potential of Haber-Bosch process.

Response 8: Our study uses established Haber-Bosch process parameters from literature to calculate ammonia production costs. While energy optimization is an important topic, it represents significant work, i.e. separate research endeavors, which are beyond the scope of our study.

1. Comment 9: The format of the references in the paper is inconsistent. It is recommended that newer references be used whenever possible, especially in areas where technology is developing rapidly.

Response 9: We have standardized the reference format through the zotero tool and incorporated more recent studies where relevant.

1. Comment 10: The chart in the paper (Figure 3 and Figure 4) is not clear enough, especially the label and annotation of the chart are not detailed enough. It is recommended to increase the clarity and annotations of the chart so that readers can better understand the content of the chart.

Response 10: The figures are now updated to clearly show the content for better understanding of the readers.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

1. The authors should update the abstract, which should include well-documented information related to the topic. The authors should briefly highlight how their study is unique and its potential contribution. The abstract should also include a few quantitative results.
2. The authors can combine the introduction and literature review. Green hydrogen and ammonia are hot topics, and many papers have been published in recent years. Therefore, the research community (even non-experts) knows the information in the introduction. Thus, the authors shorted section introduction. Instead of mentioning the well-documented information, the authors should focus on the literature review. The literature review is not enough for this topic. The authors should first expand the literature review. Then, they should clearly explain the literature gap. After, the authors should explain the novelty and contributions of this study.
3. In section 1, the authors explain that the paper's novelty is integrating offshore wind power with hydrogen and ammonia production. However, there are already published papers about this topic. In addition, different studies have covered the levelized cost of hydrogen, the levelized cost of ammonia, and the cost of transportation for hydrogen and ammonia production based on offshore wind farms. Therefore, the authors should improve the methodology and study to make this work novel and potential contributions to the current literature.
4. The authors should improve the methodology section. Some terms are not explained clearly, and some parameters, such as the inflation rate and discount rate, are not available in the section. I also did not see any information about the replacement costs of the components. The techno-economic studies in the literature generally use the replacement costs for green hydrogen systems.
5. There is no comparison of the results of this study with those of other studies in the literature.
6. The authors should explain the limitations of their methodology clearly. For example, the study does not include any degradation rate. Also, the input parameters in the literature show a range of variability. Therefore, performing a sensitivity analysis by changing different parameters can be a good idea. In summary, I suggest the authors conduct a more robust economic analysis. This analysis should include sensitivity analyses to account for uncertainties and variations in key parameters such as costs, energy prices, and policy incentives.
7. The quality of the figures should be improved.

Comments on the Quality of English Language

The language of the manuscript is generally acceptable. However, the authors can check for minor grammatical errors and improve the language further.

Author Response

1. Comment 1: The authors should update the abstract, which should include well-documented information related to the topic. The authors should briefly highlight how their study is unique and its potential contribution. The abstract should also include a few quantitative results.

Response 1: Thank you for your suggestion to improve our manuscript. We have revised the abstract to highlight novelty and incorporated a few quantitative results as suggested.

1. Comment 2: The authors can combine the introduction and literature review. Green hydrogen and ammonia are hot topics, and many papers have been published in recent years. Therefore, the research community (even non-experts) knows the information in the introduction. Thus, the authors shorted section introduction. Instead of mentioning the well-documented information, the authors should focus on the literature review. The literature review is not enough for this topic. The authors should first expand the literature review. Then, they should clearly explain the literature gap. After, the authors should explain the novelty and contributions of this study

Response 2: We have streamlined the introduction by removing unnecessary information and combined it with the literature review for better structure. A new paragraph at the end of the introduction now explicitly highlights our study’s novelty and the research gap it addresses.

1. Comment 3: In section 1, the authors explain that the paper's novelty is integrating offshore wind power with hydrogen and ammonia production. However, there are already published papers about this topic. In addition, different studies have covered the levelized cost of hydrogen, the levelized cost of ammonia, and the cost of transportation for hydrogen and ammonia production based on offshore wind farms. Therefore, the authors should improve the methodology and study to make this work novel and potential contributions to the current literature.

Response 3: We added a sensitivity analysis to show how the major costs of components affect the LCOH₂ and LCOA. We conducted a sensitivity analysis to evaluate the LCOH₂ and LCOA by varying key parameters. The parameters considered include the capacity factor of the wind farm, the efficiency of the PEM electrolyser, the conversion efficiency of the Haber-Bosch process, and the variation of CAPEX by ±20% for both turbines and platforms, as well as for the electrolyser and its platform. As outputs, graphs were generated to visualize the variation in the levelized cost of hydrogen/ammonia. Furthermore, the novelty of our research lies also in the analysis of the overall cost of production plus transportation under different circumstances in terms of capacity, distance and transportation technology.

1. Comment 4 : The authors should improve the methodology section. Some terms are not explained clearly, and some parameters, such as the inflation rate and discount rate, are not available in the section. I also did not see any information about the replacement costs of the components. The techno-economic studies in the literature generally use the replacement costs for green hydrogen systems.

Response 4: The assumed values for the inflation rate and discount rate have been included in the supplementary material.

Regarding the replacement cost, we took the value from literature [1] that all the hydrogen plant had a lifetime equal to 25 years, an 80.000 h for the stack operating time and a 2.5% degradation rate of PEM electrolyser. This lead to have 2 cell stack replacements during lifetime and we considered the cell stack replacement costs equal to 55% of electrolyser CAPEX.

1. Comment 5: There is no comparison of the results of this study with those of other studies in the literature.

Response 5: We have added a new section entitled “Discussion and comparison of results” and included a table to compare our results with those of other studies in Table 3, Section 3.

1. Comment 6: The authors should explain the limitations of their methodology clearly. For example, the study does not include any degradation rate. Also, the input parameters in the literature show a range of variability. Therefore, performing a sensitivity analysis by changing different parameters can be a good idea. In summary, I suggest the authors conduct a more robust economic analysis. This analysis should include sensitivity analyses to account for uncertainties and variations in key parameters such as costs, energy prices, and policy incentives.

Response 6: The limitations of this study include fixed efficiencies and production rate for both electrolyser and Haber-Bosch process (we did not include the dynamic behaviour of these systems).

We take the value of degradation rate of 2.5% for PEM electrolyser over plant lifetime from literature [1].

We conducted a sensitivity analysis to evaluate the LCOH₂ and LCOA by varying key parameters. The parameters considered include the capacity factor of the wind farm, the efficiency of the PEM electrolyser, the conversion efficiency of the Haber-Bosch process, and the variation of CAPEX by ±20% for both turbines and platforms, as well as for the electrolyser and its platform. As outputs, graphs were generated to visualize the variation in the levelized cost of hydrogen/ammonia.

1. Comment 7: The quality of the figures should be improved.

Response 7: The figures are now updated to clearly show the content for better understanding of the readers.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The main problems in the review comments have been partially resolved, but there is still room for improvement. Here's a breakdown:

1. On the CAPEX curve shown in Figure 10-13, note units (such as €/km or €/kg).
2. The vertical label *"LCOH2/A + LCOT" in Figure 17 should clearly read "Total Cost (€/kWh)"*.
3. Full text unified abbreviation: the full name is marked when it first appears (such as Proton Exchange Membrane (PEM) electrolysis).

Comments for author File: Comments.pdf

Author Response

Comments 1: The main problems in the review comments have been partially resolved, but there is still

room for improvement. Here's a breakdown:

a. On the CAPEX curve shown in Figure 10-13, note units (such as €/km or €/kg).

Response 1a: We are sorry for the misunderstanding, the axis of Figure 10 & 13 is not €/km or €/kg but it is actually total CAPEX expressed in € with varying distance and electrolysers capacity in the other axis. We improved the figure explanation in order to clarify what is shown in the figures. We hope it is now clearer for the reader.

b. The vertical label *"LCOH2/A + LCOT" in Figure 17 should clearly read "Total Cost (€/kWh)"*.

Response 1b: Thank you for your comment. The label on the vertical axis has been updated to "Total Cost (€/kWh)" in both Figure 16 and Figure 17.

c. Full text unified abbreviation: the full name is marked when it first appears (such as Proton Exchange Membrane (PEM) electrolysis).

Response 1c: We have carefully checked and updated the manuscript accordingly.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for the authors` effort and revisions. However, the paper should be improved more for a potential publication. Please see my specific comments below:

1. The authors should expand the literature review and more clearly explain their study's contributions to the literature. Because of its recent popularity, many papers about green hydrogen production have been published. Therefore, it should be beneficial to highlight more papers. For example, papers about liquefied hydrogen and different hydrogen carrier transports have also been published. I suggest the authors check all recent papers related to the topic.
2. The authors should better integrate figures and tables into the text. They are somewhat disconnected, making it hard to follow the narrative.
3. Please ensure all figures and tables are clearly labeled and referenced in the text. Please also improve the quality of the figures.
4. I appreciate that the authors added the comparative analysis with other studies. However, they should add more detailed comparisons and discussions of why certain results differ from other studies. In addition, the authors can highlight this study's unique contributions more explicitly in comparison to existing literature.
5. The authors should discuss the implications of the sensitivity analysis results in more detail, particularly how they might influence real-world decision-making.
6. The authors can more clearly justify some of the assumptions in the paper.

Author Response

Thank you for the authors` effort and revisions. However, the paper should be improved more for a potential publication. Please see my specific comments below:

Comment1: The authors should expand the literature review and more clearly explain their study's contributions to the literature. Because of its recent popularity, many papers about green hydrogen production have been published. Therefore, it should be beneficial to highlight more papers. For example, papers about liquefied hydrogen and different hydrogen carrier transports have also been published. I suggest the authors check all recent papers related to the topic.

Response 1: We have expanded the literature review in Section 1. In particular: studies [32], [35], [46], and [48]. These studies discuss liquefied hydrogen, ammonia, and alternative hydrogen carriers (LOHCs like toluene, dibenzyl toluene, and N-ethylcarbazole) comparing their techno-economic potential for offshore transport.

Comment 2: The authors should better integrate figures and tables into the text. They are somewhat disconnected, making it hard to follow the narrative.
Response 2: We have adjusted the layout so that the figures and tables are placed as close as possible to where they are referenced in the text. Additionally, we have worked on improving the text to better introduce the figures and, where appropriate, the accompanying analysis, in order to strengthen the connection between each figure and the next.

Comment 3: Please ensure all figures and tables are clearly labeled and referenced in the text. Please also improve the quality of the figures.

Response 3: All figures and tables have been updated to ensure they are clearly labeled and properly referenced in the text.

Comment 4: I appreciate that the authors added the comparative analysis with other studies. However, they should add more detailed comparisons and discussions of why certain results differ from other studies. In addition, the authors can highlight this study's unique contributions more explicitly in comparison to existing literature.

Response 4: We have updated the section to show comparison to prior studies such as [31], our analysis yields lower transport costs due to updated CAPEX figures and a dynamic sizing of pipeline diameter based on electrolyser capacity. Similarly, studies such as [20], [33], [39] focusing solely on one energy carrier, our work uniquely compares both hydrogen and ammonia across varying distances and capacities. Also, studies such as [44] only estimate transport costs (LCOTA) without integrating production costs (LCOH₂, LCOA). We also more explicitly highlight the novelty of our work being among the few studies to jointly evaluate hydrogen and ammonia transport cost models (LCOT) across varying electrolyser capacities and distances, with combined LCOH2/A + LCOT assessments. We further clarify that our study bridges the gap in the literature by analysing both energy carriers simultaneously, which helps decision-makers choose between hydrogen and ammonia based on techno-economic performance.

Comment 5: The authors should discuss the implications of the sensitivity analysis results in more detail, particularly how they might influence real-world decision-making.

Response 5: The sensitivity analysis has been improved and discussed in greater detail. Additionally, we have included a discussion on how the results might influence real-world decision-making.

Comment 6: The authors can more clearly justify some of the assumptions in the paper.

Response 6: We have revised the manuscript to provide clearer justifications for key assumptions, especially in the methodology section:

• The selection of PEM electrolysis was justified based on its rapid response to variable wind output and commercial maturity.
• The offshore pipeline cost multiplier (factor of two) is clarified with references to [48] and reinforced with recent literature estimates on deep-sea construction logistics.
• For hydrogen and ammonia flow rates, assumptions on density, pipeline velocity, and compression intervals were explained in Section 2.2.1 and 2.3.1 respectively, with equations expanded for clarity.
• The choice of 8% discount rate and 30-year project lifetime has been referenced and supported with literature [46].

Nevertheless, we followed our initial approach and kept a more detailed methodology description in the supplementary material in order not to overburden the reader in the main text.

Author Response File: Author Response.pdf

Round 3

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for the authors` effort. However, the authors can still improve a few points: 1. Some sections repeat similar points. The authors can streamline for better readability. 2. The authors can still improve visual presentation, such as improving the formatting of tables and figures for clarity and consistency. 3. The author can also consider expanding discussion of practical applications.

Author Response

Thank you for the authors` effort. However, the authors can still improve a few points:

Comment 1: Some sections repeat similar points. The authors can streamline for better readability.

Response 1: Repetition of sentences have been deleted. The similarities between sections have been reduced to avoid repetitions of the same concept. Nevertheless, confirmation of the same results from different point of views are underlined. In the end, we believe the text has been streamlined. Also, some sections have been moved and some have been created to better guide the readers.

Comment 2: The authors can still improve visual presentation, such as improving the formatting of tables and figures for clarity and consistency.

Response 2: Tables have been modified and follow the Energies template. This has been done both in the main text of the manuscript and in the supplementary material. Figures all use the same font and size. Figure 2 has been modified and improved.

Comment 3: The author can also consider expanding discussion of practical applications.

Response 3: The discussion about the impact and usefulness of our results are discussed in the “Discussion of Results” section as well as in the conclusion.

Author Response File: Author Response.pdf