A Comparison of Well-to-Wheels Energy Use and Emissions of Hydrogen Fuel Cell, Electric, LNG, and Diesel-Powered Logistics Vehicles in China

Round 1

Reviewer 1 Report

This is a very interesting and relevant work. I just found some typos within the text.

For example, in table 1 in the greenhouse gases section, there is a typo in the formula for N2O.

There are some inconsistencies when authors include the citations in the text. Please, check through the text.

English is, in general good. This paper is easy to read.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Abstract

1. The authors mention the four vehicle types under study: FCV, electric, LNG-fueled, and diesel-fueled. It might be helpful to describe these vehicles for readers unfamiliar with them briefly.
2. The authors mention the use of GREET software for the analysis. The authors can briefly describe this software and why it is the most suitable tool for this research.
3. The authors note that "electric logistics vehicles (EV) have the lowest energy consumption, with slightly better performance than FCV." Yet, the authors also mention that "the emissions of FCV are significantly lower." This could lead to confusion. The authors should clarify the comparison and conclusion you are trying to make here.
4. The authors should define all acronyms before using them. For instance, when using FCV, SI ICEV, and CIDI ICEV, spell them out and put the acronyms in parentheses.
5. The terms 'spark ignition internal combustion engine logistics vehicles (SI ICEV),' 'compression ignition direct injection internal combustion engine logistics vehicle (CIDI ICEV),' and 'EV' appear abruptly. The authors should integrate them appropriately within the introduction or, even better, describe them while introducing the four types of vehicles.
6. For better flow, the authors can avoid breaking sentences across line numbers.
7. The authors should include a summary of the current literature on this topic. Are there gaps in existing knowledge that your research aims to fill?

Introduction

1. The introduction is very long. The authors should shorten the introduction. The authors can remove the well-known information from the introduction to make it shorter.
2. The authors should emphasize this work's importance (to fill a gap) and the novelty (not much similar study in the literature) in the introduction.

2. Materials and Methods

1. Although the authors mentioned four types of vehicles in the introduction (FCV, Electric, LNG, and Diesel), you initially stated that three types of vehicles (diesel, electric, and natural gas) were selected for comparison. The authors should clarify this discrepancy.
2. The authors should be careful with the use of terminology. For example, LNG stands for liquefied natural gas. Be sure to distinguish between LNG (a form of natural gas) and compressed natural gas (CNG), which are different.
3. The author's justification for using data from the United States is reasonable, but the authors should also address potential differences between the two countries that could impact the study's results.
4. The authors mention that loads of all vehicles are set at 2 tons, and the proportion of urban areas is set at 0.7. The authors should explain why these particular values were chosen.
5. I recommend clarifying what the authors mean by "load" in the context of your study. Are the authors referring to the carrying capacity of the vehicles?
6. In subsections 2.1, 2.2, 2.3, and 2.4, you explain the source and production of each fuel. It's helpful and informative, but please include more about how these processes relate to your study. For example, how do the production methods of hydrogen affect your results?
7. When mentioning the environmental benefits of nuclear hydrogen production, address potential drawbacks, such as safety concerns and waste management.
8. For subsection 2.3, mention the proportion of electricity generated from renewable sources, as this can significantly affect the environmental footprint of electric vehicles.
9. Please provide adequate references for claims, such as the claim that the emissions of natural gas vehicles are significantly reduced compared to diesel vehicles (line 321).
10. In subsection 2.4, you mention that diesel vehicles are limited by engine technology. I suggest elaborating on these limitations and how they affect the study's outcomes.
11. Throughout the section, maintain consistency in presenting units and terms. For instance, ensure consistent capitalization of "LNG" and "CNG."
12. Lastly, please add a conclusion to the Materials and Methods section summarizing the procedures and how they will help answer the research questions.

3. Results

1. Explicit Indication of Significance: The authors need to highlight the statistical significance of the findings explicitly. Any percentage differences, changes, or comparisons should be statistically backed up.
2. Clarification of Terminology: The authors should ensure all abbreviations and terms are appropriately defined the first time they appear in the text. Although most of your abbreviations are defined, you have not defined PTW, WTP, or WTW. Only some readers may be familiar with these terms.
3. Data Interpretation: While presenting the raw data is vital, it is equally essential to provide an interpretation of what this data means. For instance, the phrase "The total energy consumptions of various types of vehicles in WTW are: 2061.56 KJ/km for hydrogen fuel cell logistics vehicles, 3444.25 KJ/km for natural gas logistics vehicles, 3883.27 KJ/km for diesel logistics vehicles, and 2049.51 KJ/km for electric logistics vehicles." could be followed by a brief interpretation of these numbers.
4. Figures and Tables: Your text references multiple figures (4-13), but details about these figures need to be provided. 
5. Repetitive Phrasing: Several phrases, such as "WTW emissions according to GREET software are presented in Figure X," are repeated throughout the section. This repetition might lead to reader fatigue. The authors should consider rephrasing these similar sentences to enhance the section's readability.
6. Sentence Structure: Some sentences are overly long and complex, which could lead to confusion. The authors should break these down into smaller, more precise sentences. For example, the sentence "Hydrogen, electricity, and diesel all belong to secondary energy, as they need to go through a series of preparation processes to be generated, so their energy consumption during the WTP stage is higher than that of natural gas." could be separated into two sentences for clarity.
7. Clear Conclusions: Each paragraph ends with a comparison or a finding. It would be helpful to provide clear, concise conclusions at the end of each paragraph to help readers understand the key takeaways.
8. Contextual Information: Additional context might be beneficial to understand the relevance and impact of these findings. For instance, what does reducing lifecycle energy consumption or emissions mean in practical, real-world terms? How might this affect environmental sustainability, transportation costs, etc.?
9. Correctness: The authors should ensure the accuracy of their statements. For instance, "Although both hydrogen fuel cell and electric logistics vehicles can achieve zero carbon emissions during the PTW phase," contradicts the sentence "the carbon emissions of electric logistics vehicles during the WTP phase are significant." It would be essential to clarify this discrepancy.
10. Overall Structure: The authors should consider reorganizing the section to present all energy consumption results, followed by the different emission results. This would provide a logical flow of information and avoid switching between topics.

4. Conclusions

1. Clarity and Depth of Analysis: The authors' conclusions mostly restate the study's results. The authors should incorporate a more detailed analysis of the implications of the findings, like discussing the potential impacts on policy-making, industry development, and future research.
2. Generalizability of Findings: The manuscript focuses heavily on China, which is understandable given the study context. However, to broaden the implications of the authors` study, consider addressing how their results could be applied to other countries or regions.
3. Future Work: The authors mention the importance of clean energy integration and the development of clean hydrogen production technologies but don't address future research directions. The authors could consider suggesting areas of investigation, like exploring cost-effectiveness or societal acceptance of these technologies, which would strengthen the final part of your conclusions.
4. Structure and Flow: The authors should consider numbering or bullet-pointing each conclusion to make the section more readable and to emphasize each point separately.

The manuscript's language is acceptable; however, the authors should improve the language during the revision. Please see my specific comments above. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors appropriately replied my questions.