Techno-Economic Analysis of Hydrogen Transport via Truck Using Liquid Organic Hydrogen Carriers

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Comments on ‘Techno-Economic Analysis of Hydrogen Transport via Truck Using Liquid

Organic Hydrogen Carriers’.

 

1. Literature review on relevant research subjects is missing or very little in Introduction. To justify the necessity of this submitted manuscript, and to identify information gaps in literature, a proper section/ paragraphs of literature review will strengthen the quality of the manuscript.

There are many papers dealing with hydrogen transport by ammonia, LOHC, etc., using trucks and ships, such as ‘Cho, H.H., Strezov, V. and Evans, T.J., 2024. Life cycle assessment of renewable hydrogen transport by liquid organic hydrogen carriers. Journal of Cleaner Production, 469, p.143130.’ and ‘Kim, A., Lee, H., Brigljević, B., Yoo, Y., Kim, S. and Lim, H., 2021. Thorough economic and carbon footprint analysis of overall hydrogen supply for different hydrogen carriers from overseas production to inland distribution. Journal of cleaner production, 316, p.128326’.

It would be great if the authors can add some literature review for comparing different hydrogen production and transport options using numeric values.

Because this manuscript lacks Discussion, comparison with other studies could be alternatively inserted in Discussion (if not Introduction)

 

2. Table 1-12 may need references and data sources below each table, or in the new column in each table.

Author Response

Question 1.

Literature review on relevant research subjects is missing or very little in Introduction. To justify the necessity of this submitted manuscript, and to identify information gaps in literature, a proper section/ paragraphs of literature review will strengthen the quality of the manuscript. There are many papers dealing with hydrogen transport by ammonia, LOHC, etc., using trucks and ships, such as ‘Cho, H.H., Strezov, V. and Evans, T.J., 2024. Life cycle assessment of renewable hydrogen transport by liquid organic hydrogen carriers. Journal of Cleaner Production, 469, p.143130.’ and ‘Kim, A., Lee, H., Brigljević, B., Yoo, Y., Kim, S. and Lim, H., 2021. Thorough economic and carbon footprint analysis of overall hydrogen supply for different hydrogen carriers from overseas production to inland distribution. Journal of cleaner production, 316, p.128326’. It would be great if the authors can add some literature review for comparing different hydrogen production and transport options using numeric values. Because this manuscript lacks Discussion, comparison with other studies could be alternatively inserted in Discussion (if not Introduction).

Answer 1. 

Thank you for your comment. We have revised the introduction by adding a dedicated section that provides a concise state-of-the-art review on hydrogen transport via LOHCs, covering both long-distance and short-distance applications, as per your suggestion.

Please refer to section “1.1 Hydrogen transport by LOHCs”, lines 93 - 147.

Furthermore, the discussion in Section 4 (“Results and Discussion”) has been expanded to include a comparative analysis between the findings of this study and those reported in the literature reviewed in the Introduction.

Please refer to lines 510-517; 578-586.

Question 2.

Table 1-12 may need references and data sources below each table, or in the new column in each table.

Answer 2.

Thank you for your comment. References have been added as a new column in each table.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

The authors provide a straightforward techno economic analysis of hydrogen transport over shorter distances comparing LOHCs with other transport options.

• You consider a hydrogen transport in Italy. The hydrogen production case, however, does not reflect conditions in Italy. There is no electrolytic hydrogen production with grid electricity without aligning with sustainability regulations (EU RED and associated delegated act [RFNBO]). The way you assume hydrogen production leads to higher GHG emissions than hydrogen production from natural gas. Furthermore, the costs are higher. Thus, this is a very unlikely production scenario. If you change the production to RFNBO conformity, this would then lead to differences in the full load hours and maybe the transport plan.
• The methodology on the transport plan you use e.g. to derive the numbers of necessary trips and trucks is not clear to the reader. E.g. how do you integrate “truck availability”?
• You call one scenario “green LOHC”. Use a scientific wording to describe your case. This wording is misleading the reader (not only because you do not consider “green hydrogen”).
• 363ff. and l. 453 I am not convinced by your conclusions “This high number of trips 363 could pose a problem for the trucks' lifespan, leading to increased degradation and a 364 higher probability of truck breakdowns, which would result in higher costs and potential 365 penalties due to failure to deliver hydrogen. Additionally, this could increase traffic, caus- 366 ing delays and disruptions to other services. “. Up to my knowledge, trucks are designed for this purpose. The numbers of trucks and distances are not very high in contrast to other industries. You furthermore say that congestions are possible and might cause public opposition. You did not study that….
• 423ff. you draw a conclusion that LOHC become “most economical choice”. The uncertainty in your input data is too high to say it this way.
• A sensitivity analysis is missing. You conduct a study that is based on a high number which partly have a very high uncertainty. In order to be able to draw conclusions, a sensitivity analysis is crucial. Conducting a sensitivity analysis is necessary to be added to the work.
• You do compare three different hydrogen transport ways that provide a hydrogen at different purities. The purity of the hydrogen is an important cost factor! For a very high hydrogen purity, LOHCs would require additional hydrogen purification and thus additional costs that the other transport ways do not need.
• 134 up to my knowledge, liquid hydrogen transport containers are not fully emptied to keep the low temperature. So you cannot use the full transport capacity for hydrogen delivery. Furthermore, how do you consider evaporation?

 

The structure of the text is clear and allows for a good reading. Partly, the formulation is not sufficiently precise or wrong.

• 12 you mention “feasibility”, although you do not check for feasibility
• 30 hydrogen is less than 1/3 of natural gas density
• L 93 clarify the term viability
• 323 it is unclear what you mean with production costs.
• 328 holds provided….
• Table 13. What is “n”? Define all parameters!
• You introduce figure 4 before you introduced your LOHC cases “green” and “fossil”.

Author Response

Reviewer 2

 

Question 1.

You consider a hydrogen transport in Italy. The hydrogen production case, however, does not reflect conditions in Italy. There is no electrolytic hydrogen production with grid electricity without aligning with sustainability regulations (EU RED and associated delegated act [RFNBO]). The way you assume hydrogen production leads to higher GHG emissions than hydrogen production from natural gas. Furthermore, the costs are higher. Thus, this is a very unlikely production scenario. If you change the production to RFNBO conformity, this would then lead to differences in the full load hours and maybe the transport plan.

Answer 1.

Thank you for your suggestion. In the initial version, we assumed a high number of equivalent full-load hours (8500 h) by integrating national grid electricity with renewable sources to ensure continuous operation of the electrolyser. Following your feedback, we have revised our approach to align with the 2023 EU Delegated Acts on renewable hydrogen (https://ec.europa.eu/commission/presscorner/detail/en/ip_23_594). Based on data from the Confindustria report (https://www.confindustria.it/home/appuntamenti/eventi-confindustria/dettaglio-evento/modelli-di-business-per-l-utilizzo-dell-H2) and in compliance with the Delegated Act, we have now assumed 5500 equivalent full-load hours, considering a monthly correlation (before 2030) under a PPA contract. This assumption ensures a more realistic representation of green hydrogen production in Italy, in line with regulatory constraints and the availability of renewable resources, providing a stronger basis for our analysis.

Please refer to lines 285-298.

Question 2.

The methodology on the transport plan you use e.g. to derive the numbers of necessary trips and trucks is not clear to the reader. E.g. how do you integrate “truck availability”?

Answer 2.

Thank you for your comment. The methodology was initially described in the supplementary material; however, to avoid confusion, all the relevant information and formulations have now been integrated into Section 3 “Method”.

Please refer to lines 385-428.

Question 3.

You call one scenario “green LOHC”. Use a scientific wording to describe your case. This wording is misleading the reader (not only because you do not consider “green hydrogen”).

Answer 3.

Thank you for your comment. We have revised the terminology, replacing "Green LOHC" with "H₂-powered LOHC" and "Fossil LOHC" with "NG-powered LOHC" to clearly indicate the type of fuel used to power the dehydrogenation plant.

Question 4.

363ff. and l. 453 I am not convinced by your conclusions “This high number of trips could pose a problem for the trucks' lifespan, leading to increased degradation and a higher probability of truck breakdowns, which would result in higher costs and potential penalties due to failure to deliver hydrogen. Additionally, this could increase traffic, causing delays and disruptions to other services”. Up to my knowledge, trucks are designed for this purpose. The numbers of trucks and distances are not very high in contrast to other industries. You furthermore say that congestions are possible and might cause public opposition. You did not study that….

Answer 4.

Thank you for your comment. We know that heavy-duty trucks are designed for continuous operation and long-distance transport. However, our statement aims to highlight the potential logistical challenges that could arise from the high number of required trips in a hydrogen distribution network. While it is true that truck fleets in other industries operate under similar conditions, hydrogen transport introduces additional constraints, such as regulatory considerations and safety protocols to hydrogen dandling. Regarding traffic congestion and public opposition, we recognize that a detailed study on these aspects was not conducted. Our intention was to focus on possible side effects that could emerge if a significant portion of hydrogen transport relies on frequent trucking operations, particularly in densely populated or industrially congested areas. To address your concern, we have refined our discussion to clarify that these aspects represent hypothetical challenges rather than definitive conclusions.

Please refer to lines 479-485 and lines 630-632.

Question 5.

423ff. you draw a conclusion that LOHC become “most economical choice”. The uncertainty in your input data is too high to say it this way. A sensitivity analysis is missing. You conduct a study that is based on a high number which partly have a very high uncertainty. In order to be able to draw conclusions, a sensitivity analysis is crucial. Conducting a sensitivity analysis is necessary to be added to the work.

Answer 5.

Thank you for your suggestions. In our work we investigated the effect of three different distances and three different loadings, for different hydrogen storage systems. We believe this work provides a strong foundation, especially since we’ve included the hydrogenation and dehydrogenation processes, which haven't been considered in other studies. Of course, there are other scenarios that could be explored in future research.

Question 6.

You do compare three different hydrogen transport ways that provide a hydrogen at different purities. The purity of the hydrogen is an important cost factor! For a very high hydrogen purity, LOHCs would require additional hydrogen purification and thus additional costs that the other transport ways do not need.

Answer 6.

Thank you for the comment. Compared to compressed and liquefied hydrogen, which naturally achieve high purity, hydrogen released from LOHCs may require additional purification to remove traces of the carrier or other by-products, depending on the application. However, according to Niermann et al. (https://doi.org/10.1016/j.ijhydene.2019.01.199), among the most studied LOHCs, DBT could not require purification steps after dehydrogenation. This is because DBT remains liquid in ambient conditions, and has negligible volatility, minimizing contamination risks. Furthermore, since this study focuses solely on hydrogen transportation rather than its end use, no specific post-delivery processing steps have been considered. In future studies, a more detailed assessment of hydrogen purity requirements for different end-use applications will be considered.

 

Question 7.

134 up to my knowledge, liquid hydrogen transport containers are not fully emptied to keep the low temperature. So you cannot use the full transport capacity for hydrogen delivery. Furthermore, how do you consider evaporation?

Answer 7.

Thank you for your comment. We have addressed this aspect by reporting the net hydrogen payload, which accounts for approximately 5% of the total H₂ payload. Specifically, we have considered a heel fraction of 5% of the transported volume, following Brouzas et al. (https://doi.org/10.1016/j.ijhydene.2024.12.253). Since this aspect was not clearly stated in the manuscript, we have added a footnote to Table 13 to clarify it.

Please refer to Table 13 and lines 389-391

Regarding evaporation, a boil-off rate of 0.03 wt%/day has been considered and accounted for as a variable expenditure, specifically the electricity consumption required for re-liquefaction.

Please refer to Table 12.

Question 8.

The structure of the text is clear and allows for a good reading. Partly, the formulation is not sufficiently precise or wrong.

Answer 8.

We have reviewed and corrected the formulation.

Question 9.

12 you mention “feasibility”, although you do not check for feasibility.

Answer 9.

Thank you for your suggestion. Our study is a techno-economic analysis. That term was erased.

Question 10.

30 hydrogen is less than 1/3 of natural gas density.

Answer 10.

Thank you for the comment. We fixed them.

Question 11.

L 93 clarify the term viability.

Answer 11.

We intended to refer to “feasibility”.

Question 12.

323 it is unclear what you mean with production costs.

Answer 12.

We refer to costs associated with hydrogen generation from an alkaline electrolyser.

Question 13.

328 holds provided….

Answer 13.

Thank you for the comment. We have revised the sentence to: “This assumption remains valid as long as there are no daily constraints imposed by a hypothetical hydrogen user and only an annual hydrogen delivery requirement needs to be met.”

Question 14.

Table 13. What is “n”? Define all parameters!

Answer 14.

Thank you for the comment, we have defined all parameters.

Question 15.

You introduce figure 4 before you introduced your LOHC cases “green” and “fossil”.

Answer 15.

Thank you for the comment. We fixed them. Please refer to 359-367.

 

 

 

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

The title is clear and directly communicates the study's focus: the techno-economic analysis of hydrogen transportation via liquid organic hydrogen carriers (LOHCs) by road.

The abstract effectively summarizes the study's purpose, methods, and key findings. It compares compressed and liquefied hydrogen and highlights the cost-effectiveness of different transportation methods over various distances and demand levels.

• The introduction provides a good background on the role of hydrogen in sustainable energy models and the challenges associated with hydrogen transportation.
• It clearly outlines the advantages of LOHCs and sets the stage for the techno-economic analysis.
• The introduction could be improved by briefly mentioning the current state of LOHC technology and its potential for scaling up.
• The methodology section is detailed, describing the simulation of hydrogenation and dehydrogenation reactors using ASPEN Plus and the cost assessment of various transportation methods.
• The section could benefit from a more explicit discussion on how the sensitivity analysis was conducted and how the parameters were chosen for the different daily demands and transport distances.
• The results are presented in a clear and structured manner, with tables and figures that effectively communicate the findings.
• The discussion effectively compares the different transportation methods and highlights the cost implications of each.
• It would be beneficial to include a more detailed analysis of the assumptions made in the model and how they might affect the results.

• The conclusions summarize the key findings and their implications for hydrogen transportation.
• It would be helpful to include recommendations for future research or potential improvements in LOHC technology based on the study's findings.
• The manuscript should clearly state any assumptions made during the analysis and discuss their potential impact on the results.
• The discussion could be enhanced by addressing the scalability of LOHC technology and its technological readiness level (TRL).
• While the study focuses on economic aspects, it might be beneficial to briefly discuss the environmental implications of each transportation method, especially considering the CO2 emissions associated with fossil-LOHC.
• The manuscript could include a more detailed comparison with other studies in the field to position its findings within the existing body of research.
• A long-term cost analysis, including maintenance and potential technological advancements, could provide a more comprehensive view of the economic viability of each method.
• It would be helpful to include recommendations for future research or potential improvements in LOHC technology based on the study's findings.

Overall, the manuscript presents a valuable analysis of hydrogen transportation via LOHCs and contributes to the understanding of the economic implications of different transportation methods. Addressing the potential issues and drawbacks mentioned above could further strengthen the study. I think when the authors address the suggestions accordingly, MS can be accepted for publication.

Author Response

Question 1.

The introduction could be improved by briefly mentioning the current state of LOHC technology and its potential for scaling up.

Answer 1.

Thank you for your comment. We have revised the introduction.

Please refer to section “1.1 Hydrogen transport by LOHCs”, lines 93-147.

Question 2.

It would be beneficial to include a more detailed analysis of the assumptions made in the model and how they might affect the results.

Answer 2.

Thank you for the comment. We have detailed the assumptions.

Please refer to lines 285-298; 302-306; 363-367.

Question 3.

The conclusions summarize the key findings and their implications for hydrogen transportation. It would be helpful to include recommendations for future research or potential improvements in LOHC technology based on the study's findings.

Answer 3.

Thank you for your suggestion. Future researches are implemented in the conclusions.

Please refer to lines 636-640.

Question 4.

The manuscript should clearly state any assumptions made during the analysis and discuss their potential impact on the results. The discussion could be enhanced by addressing the scalability of LOHC technology and its technological readiness level (TRL).

Answer 4.

Thank you for your suggestion. Certainly, the aspect you mentioned is significant; however, it is beyond the core focus of the paper. This suggestion has been considered as a future development.

Question 5.

While the study focuses on economic aspects, it might be beneficial to briefly discuss the environmental implications of each transportation method, especially considering the CO2 emissions associated with fossil-LOHC.

Answer 5.

Thank you for your comment. We have added a dedicated section addressing CO₂ emissions for each hydrogen transport method.

Please refer to the “4.2 CO₂ Emissions Assessment” section, lines 493-540.

 

 

Question 6.

The manuscript could include a more detailed comparison with other studies in the field to position its findings within the existing body of research.

Answer 6.

Thank you for your comment. We have revised Section 4 (“Results and Discussion”) to include a comparative analysis between the findings of this study and those reported in the literature reviewed in the Introduction.

Please refer to lines 510-517; 578-586.

Question 7.

A long-term cost analysis, including maintenance and potential technological advancements, could provide a more comprehensive view of the economic viability of each method. It would be helpful to include recommendations for future research or potential improvements in LOHC technology based on the study's findings.

Answer 7.

Thank you for your suggestion. Future researches are implemented in the conclusions.

Please refer to lines 636-640.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors,

you answered well to many of my comments. However, I still see the necessity to conduct a sensitivity analysis. Your assumptions e.g. on investments show a high uncertainty. Assumptions e.g. on the hydration / dehydration unit have usually a uncertainty of +/- 50% due to the methodology you apply. Furthermore, the costs for the electricity supply show a high uncertainty (there is no reliable information on PPAs for hydrogen production delivering 5500h/a). This will cause a strong impact on hydrogen costs. I expect that a sensitivity analysis will highlight under which conditions LOHCs still provide a more economic solution.

Best regards

Author Response

Question.

you answered well to many of my comments. However, I still see the necessity to conduct a sensitivity analysis. Your assumptions e.g. on investments show a high uncertainty. Assumptions e.g. on the hydration / dehydration unit have usually a uncertainty of +/- 50% due to the methodology you apply. Furthermore, the costs for the electricity supply show a high uncertainty (there is no reliable information on PPAs for hydrogen production delivering 5500h/a). This will cause a strong impact on hydrogen costs. I expect that a sensitivity analysis will highlight under which conditions LOHCs still provide a more economic solution.

Answer.

Thank you for your comment. We appreciate your observation and have made our best effort to clarify these aspects.

Regarding the costs for the electricity supply, please refers to “3.1 Levelized cost of electricity” (lines 284-300).

Therefore, an average electricity cost of 0.14 €/kWh was assumed for the 1–2–4 t/d scenarios and for transport distances of 50, 150, and 300 km. Given the uncertainty in electricity prices, a sensitivity analysis on the Levelized Cost of Transported Hydrogen (LCOTH) and Levelized Cost of Hydrogen (LCOH) was then performed by varying the Levelized Cost of Electricity (LCOE) between the historical maximum (0.30 €/kWh) and minimum (0.03 €/kWh) values of the Italian PUN over the past two decades. To keep the analysis concise, the manuscript reports results for a small-scale case (1 t/d) and a large-scale case (4 t/d), both at an intermediate distance of 150 km, which is the distance at which the LOHC solution starts to compete with the compressed gaseous option.

To account for the uncertainty in the capital cost of hydrogenation and dehydrogenation plants, three cost ranges were assumed for the DBT–PDBT option. A minimum value (DBT_Min) was taken from the most optimistic scenario reported by Eypasch et al., a maximum value (DBT_Max) from the most pessimistic scenario proposed by Reuß et al., and an average value (that was used as the baseline case in the hydrogen transport by LOHC solution in the analysis).

Please refer to section “4.4 Sensitivity analysis” (lines 597-680).

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

Comments and Suggestions for Authors

No further comments. I wish you all the best and thank you for the professional interaction.