Energy Management Strategy of Hydrogen Fuel Cell/Battery/Ultracapacitor Hybrid Tractor Based on Efficiency Optimization
Round 1
Reviewer 1 Report
The literature review is not complete. There are many relevant papers which have not been included.
The work focuses above all on making the system work with maximum efficiency. Although it is an important objective, nowadays more complex and multi-objective objectives are being worked on.
How does working at maximum efficiency affect system degradation?
Author Response
Dear Reviewer:
On behalf of my co-authors, we are very grateful to you for giving us an opportunity to revise our manuscript. we appreciate you very much for your positive and constructive comments and suggestions on our manuscript entitled “Energy management strategy of hydrogen fuel cell/battery/ultracapacitor hybrid tractor based on efficiency optimization”(ID: applsci-2025792).
We have studied your comments carefully and tried our best to revise our manuscript according to the comments. The following are the responses and revisionsⅠhave made in response to the reviewers' questions and suggestions on an item-by-item basis. Thanks again for the hard work of the editor and reviewer!
Comment No.1:The literature review is not complete. There are many relevant papers which have not been included.
Response: Thanks to the Reviewer for the reminder, We have improved the literature review section of the article to cover more research and applications in this field.
Comment No.2:How does working at maximum efficiency affect system degradation?
Response: In this article, the characteristics of the hydrogen fuel cell, power cell, and ultracapacitor are analyzed and studied, and a simple model is established to verify that a single energy source cannot meet the characteristics of high and fast-changing demand power during tractor operation. The experimental results show that the EMS established in this paper can effectively reduce the fluctuation of the output power of the PEMFC system. However, this article simply uses some existing findings to show that smooth power output can extend the life of the PEMFC, without quantifying in detail how it affects the system degradation. Nowadays, more complex and multi-objective goals are being set, and more variable factors need to be considered in practical engineerings, such as temperature, humidity, emissions, and overload operation. To address these issues, we are using more complex operating conditions that include plowing and rototilling, considering more optimization and constraints that encompass the full life cycle of the PEMFC system. However, due to space and other reasons, these studies will be presented in subsequent research articles.
We appreciate Reviewers’warm work earnestly, thank you very much for your good comments and suggestions.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Overall, it is a good paper with adequate novelty for publication. I have comments that should be incorporated to improve the further quality of the work:
1. The introduction may contain the background information, motivation for the study, contributions, and the paper organization. A separate section for the review of literature is recommended to be expounded.
2. A more state-of-the-art literature review should be undertaken to cover various applications of the proposed approach.
3. All equations must be clearly referenced.
4. No conclusion section in the paper.
Author Response
Dear Reviewer:
On behalf of my co-authors, we are very grateful to you for giving us an opportunity to revise our manuscript. we appreciate you very much for your positive and constructive comments and suggestions on our manuscript entitled “Energy management strategy of hydrogen fuel cell/battery/ultracapacitor hybrid tractor based on efficiency optimization”(ID: applsci-2025792).
We have studied your comments carefully and tried our best to revise our manuscript according to the comments. The following are the responses and revisions Ⅰ have made in response to the reviewers' questions and suggestions on an item-by-item basis. Thanks again for the hard work of the editor and reviewer!
Comment No.1:The introduction may contain the background information, motivation for the study, contributions, and the paper organization. A separate section for the review of literature is recommended to be expounded.
Response: Thanks to the Reviewer for the reminder, we have improved the literature review section of the article to cover more research and applications in this field.
Comment No.2:A more state-of-the-art literature review should be undertaken to cover various applications of the proposed approach.
Response: Thanks to the Reviewer for the reminder, we have improved the literature review section of the article to cover more research and applications in this field.
Comment No.3:All equations must be clearly referenced.
Response: Thanks to the Reviewer for the reminder, we have added a citation note to the formula
Comment No.4:No conclusion section in the paper.
Response: The reviewers' suggestions are important, a good conclusion is important, and as shown in Chapter 5, we have revised the conclusion of the article to make it more convincing and to give it a more complete structure.
We appreciate the Reviewers’warm work earnestly, thank you very much for your good comments and suggestions.
Author Response File: Author Response.pdf
Reviewer 3 Report
Dear Authors Thank you so much for submitting your article to the Journal. Although, I found some revisions which I feel for the improvement in the article
1) Authorrs can refer one of the given DOI and refer to that paper which will improve the effect of present article, and the DOI is: https://doi.org/10.1016/j.ijhydene.2022.09.015
2) Authors can compare the present work with other published, and also what are the improvement in the proposed in the study.
3) Please, I did not understand what authors highited in red color for Fig.12 and Fig.13. There is no background statement in the article reasons for highlighting. What authors exactly wants to convenience is questionable for me in fig.12 and fig.13
4) Fig.18., and 19. Authors your symbols for efficiency (%) is not visible, make it clearly visible. However, improve quality of all your figures.
5) Fig.2Ob, authors maintain all your legends as same as other figures because in legends boxes were missing
6) Authors results need to be further improvements
7) Finally, please state wellconclusion because it looks so tendious
Author Response
Dear Reviewer:
On behalf of my co-authors, we are very grateful to you for giving us an opportunity to revise our manuscript. we appreciate you very much for your positive and constructive comments and suggestions on our manuscript entitled “Energy management strategy of hydrogen fuel cell/battery/ultracapacitor hybrid tractor based on efficiency optimization”(ID: applsci-2025792).
We have studied your comments carefully and tried our best to revise our manuscript according to the comments. The following are the responses and revisionsⅠhave made in response to the reviewers' questions and suggestions on an item-by-item basis. Thanks again for the hard work of the editor and reviewer!
Comment No.1:Authorrs can refer one of the given DOI and refer to that paper which will improve the effect of present article, and the DOI is: https://doi.org/10.1016/j.ijhydene.2022.09.015.
Response: We have read this article, and there is no doubt that it is a good paper with adequate novelty for publication and to improve the effectiveness of our article. We have cited this article and quoted one other article by its author.
Comment No.2:Authors can compare the present work with other published, and also what are the improvement in the proposed in the study.
Response: Thanks to the Reviewer for the reminder, we have improved the literature review section of the article to cover more research and applications in this field.
Comment No.3:Please, I did not understand what authors highited in red color for Fig.12 and Fig.13. There is no background statement in the article reasons for highlighting. What authors exactly wants to convenience is questionable for me in fig.12 and fig.13
Response: The red points in the diagram represent the actual operating points of the PEMFC system, The red dot in the figure represents the actual operating point of the PEMFC system, and the output power of the PEMFC is correspondingly drawn to the power-efficiency diagram of the PEMFC to get the red dot, which can be a more intuitive way for us to see the overall output efficiency of the PEMFC system. We have also added its description in the article.
Comment No.4:Fig.18., and 19. Authors your symbols for efficiency (%) is not visible, make it clearly visible. However, improve quality of all your figures.
Response: Thanks to the Reviewer for the reminder, we have solved this problem and all the images in the article are vector images, which will ensure that all images remain clear when zoomed in.
Comment No.5:Fig.20b, authors maintain all your legends as same as other figures because in legends boxes were missing
Response: Thanks to the Reviewer for the reminder, we have solved this problem and all the images in the article are vector images, which will ensure that all images remain clear when zoomed in.
Comment No.6:Finally,please state well conclusion because it looks so tendious
Response: A good conclusion is important, and as shown in Chapter 5, we have revised the conclusion of the article to make it more convincing and to give it a more complete structure
We appreciate the Reviewers’warm work earnestly, thank you very much for your nice comments and suggestions.
Author Response File: Author Response.pdf
Reviewer 4 Report
The paper in question deals with the EMS of a hybrid power system for a tractor consisting of a supercapacitor, a battery, and a fuel cell. The paper deals with strategies for optimizing the distribution of energy based on a measured load demand for a tractor. Three different strategies are applied and compared, where the authors suggest a third adding both separation of high frequency and low frequency variation, and an optimization for high efficiency on the fuel cell system. The study is scientifically sound and of high interest to the readers, and I recommend publication with minor modifications.
Main issues:
- The authors use a load demand power curve of only 5 min. This ensures that some of the constraints in their EMS are not challenged, for example that the battery needs to be within 20 and 80%, or that the EMS would have effect on the practical sizing of the system. Could the authors comment on their choice of power demand, and why for example not a full working day or another representative curve be used instead?
- Related to the first point, the power demand fits well with an example fuel cell, and is averaged at around 17-18 kW. However, a real system would undergo start/stop, periods of idling/breaks, and even higher spikes due to especially tough loads, for example driving through muddy terrain or up a steep hill. This would push likely push the fuel cell outside of the maximum efficiency region between about 14-18 kW. In the authors opinion, would their suggested EMS still be able to deliver considerable fuel savings also over longer times and for a whole workday or similar representative power demand data?
Minor comments:
- line 91-92, the authors use the term Tesla voltage, which I am not familiar with, I would suggest rephrasing this as "reversible voltage" or "thermodynamic voltage".
- In Figure 4, the y axis is different in a) and b). This should be fixed, i.e., change scale on 4a).
Author Response
Dear Reviewer:
On behalf of my co-authors, we are very grateful to you for giving us an opportunity to revise our manuscript. we appreciate you very much for your positive and constructive comments and suggestions on our manuscript entitled “Energy management strategy of hydrogen fuel cell/battery/ultracapacitor hybrid tractor based on efficiency optimization”(ID: applsci-2025792).
We have studied your comments carefully and tried our best to revise our manuscript according to the comments. The following are the responses and revisionsⅠhave made in response to the reviewers' questions and suggestions on an item-by-item basis. Thanks again for the hard work of the editor and reviewer!
Comment No.1:he authors use a load demand power curve of only 5 min. This ensures that some of the constraints in their EMS are not challenged, for example that the battery needs to be within 20 and 80%, or that the EMS would have effect on the practical sizing of the system. Could the authors comment on their choice of power demand, and why for example not a full working day or another representative curve be used instead?
Response: To improve the efficiency of the simulation and shorten the simulation time, the power output case of 300s is used in this paper for the study, which also ensures that some constraints are not challenged. This paper focuses on an optimal design approach for hybrid tractor energy management considering efficiency optimization and output power smoothing. The operation of a PEMFC system is a complex process and in real engineering, more variable factors need to be considered, such as temperature, humidity, emissions, and overload operation. To address these issues, more complex operating conditions that include plowing and rototilling are used, and more optimization and constraints that encompass the full life cycle of the PEMFC system are considered. In addition, the battery SOC is maintained between 20% and 80%, which is a combination of some empirical values from the literature and experiments, too high or too low battery SOC will affect its performance, as mentioned in the study of battery performance in Chapter 2. We have also added a note in 3.1.
Comment No.2:Related to the first point, the power demand fits well with an example fuel cell, and is averaged at around 17-18 kW. However, a real system would undergo start/stop, periods of idling/breaks, and even higher spikes due to especially tough loads, for example driving through muddy terrain or up a steep hill. This would push likely push the fuel cell outside of the maximum efficiency region between about 14-18 kW. In the authors opinion, would their suggested EMS still be able to deliver considerable fuel savings also over longer times and for a whole workday or similar representative power demand data?
Response: Thanks to the Reviewer for the reminder. This article focuses on the optimal design of hybrid tractor energy management considering efficiency optimization and output power smoothing. Today, more complex and multi-objective goals are being developed for tractors that operate not only with large power fluctuations, but also with "particularly hard loads" as the reviewer calls them, which will indeed drive the fuel cell output power beyond the ideal, but it does not affect the optimization result of not exceeding the system's efficiency zone, which can still result in significant fuel savings. In response to the reviewer's suggestion, we will use more complex conditions that include plowing and rototilling, with higher load demand power, and consider more optimizations and constraints that include the full life cycle of the PEMFC system to study the effect of the PEMFC system when it has to work outside of the high-efficiency zone. The reviewers' suggestions are important, however, due to space and other reasons, these studies will be presented in subsequent research articles.
Comment No.3:line 91-92, the authors use the term Tesla voltage, which I am not familiar with, I would suggest rephrasing this as "reversible voltage" or "thermodynamic voltage".
Response: Thanks to the Reviewer for the reminder. We have modified it to "thermodynamic voltage".
Comment No.4:In Figure 4, the y axis is different in a) and b). This should be fixed, i.e., change scale on 4a).
Response: Thanks to the Reviewer for the reminder. We have solved this problem and all the images in the article are vector images, which will ensure that all images remain clear when zoomed in. Thank you for your correction.
We appreciate the Reviewers’warm work earnestly, thank you very much for your nice comments and suggestions.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Accept in present form
Author Response
Thank you very much for your work！
