Estimating Aircraft Power Requirements: A Study of Electrical Power Demand Across Various Aircraft Models and Flight Phases
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsHere’s a revised version with more precision and clarity:
This paper presents a comprehensive, engineering-focused, and effective procedure for estimating the electric power requirements of aircraft systems powered by an onboard fuel cell system. While the methodology is thorough, some improvements are needed to clarify variable definitions and enhance usability.
For instance, variable "H" in Equation (1) appears undefined; although it may represent height, it should be explicitly introduced to align with engineering standards. Similarly, the variable m˙ram\dot{m}_{\text{ram}} appears in Equation (9) but lacks definition and application context. Improving descriptions for these and other variables will assist readers in applying the equations effectively.
While the authors focus on estimating power requirements, they omit crucial information on the duration of each power demand, which is essential for appropriately sizing the fuel cell. It is unclear if these durations are implied in Figure 3, which outlines a schematic of a typical flight mission.
Cooling requirements for the fuel cell also warrant attention. Although fuel cells are more efficient than turbo engines, a 700 kW electrical demand would generate 245 kW in thermal losses at 65% efficiency. This loss requires additional electric power for dissipation, yet it appears unaccounted for in the overall power estimate. Moreover, considerations like hydrogen storage, increased cabling weight, and adjustments to piping also impact power requirements but are not discussed.
The paper doesn't have a conclusion section, which does not align with the journal's formatting guidelines.
While this paper is a promising contribution to the journal, addressing these areas will enhance its clarity and applicability.
Author Response
Comment 1:
For instance, variable "H" in Equation (1) appears undefined; although it may represent height, it should be explicitly introduced to align with engineering standards. Similarly, the variable m˙ram\dot{m}_{\text{ram}} appears in Equation (9) but lacks definition and application context. Improving descriptions for these and other variables will assist readers in applying the equations effectively.
Response 1:
In response, we have now included explicit definitions for all variables in the manuscript, including "H" (see page 7 on line 232), p_0-11 (see page 7 on line 233), the heat capacity ratio kappa (page 14, line 527), the corrected mass flow m_cabin (page 15, line 557) and the density of ice (page 22, line 770). We reviewed the manuscript but could not locate the variable m˙ram\dot{m}_{\text{ram}} mentioned in your comment. Equation (9) actually describes the number of passengers on board rather than an airflow or mass rate parameter. If necessary, we are open to further clarifying this equation to ensure accuracy and alignment with engineering standards.
All improvements are marked in blue in the PDF.
Comment 2:
While the authors focus on estimating power requirements, they omit crucial information on the duration of each power demand, which is essential for appropriately sizing the fuel cell. It is unclear if these durations are implied in Figure 3, which outlines a schematic of a typical flight mission.
Response 2:
The duration of each flight phase is intentionally excluded from Figure 3 and from the calculations, as it varies by airline and route. To clarify this, we have added a subsection in the Scope section (see Section 3.3 on page 6). Here, we explain that our calculations focus on the required power per flight phase, specifically the maximum power needed by the aircraft system during each phase. We do not account for variable load profiles or multiple segments within a phase. Our results serve as a reference for required power.
Comment 4:
Cooling requirements for the fuel cell also warrant attention. Although fuel cells are more efficient than turbo engines, a 700 kW electrical demand would generate 245 kW in thermal losses at 65% efficiency. This loss requires additional electric power for dissipation, yet it appears unaccounted for in the overall power estimate. Moreover, considerations like hydrogen storage, increased cabling weight, and adjustments to piping also impact power requirements but are not discussed.
Response 4:
Thank you for emphasizing these additional considerations. In response, we have added a paragraph to the Summary and Conclusion sections, highlighting that calculating the electrical power requirement is only an initial step and that further work is needed to design a complete fuel cell system. Please refer to the explanation in the attached PDF on page 39, beginning at line 1268 (highlighted in yellow), for further details.
Comment 5:
The paper doesn't have a conclusion section, which does not align with the journal's formatting guidelines.
Response 5:
We apologize for this oversight. We have added a conclusion section to summarize the main findings, outline the applicability of the methodology. The conclusion can now be found on page 38.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsOverall an excellent and informative piece of work.
A bit too long but, on the other hand, a thorough analysis to provide the entire background to the interested audience. It could be a book chapter, rather than an article.
In this sense, I am missing the most notable finding in the summary section. For example, a quantified metric or an observation that was or was not expected before the analysis took place. I am sure that 'The results of this work contribute to a better understanding of the electrical power requirements of aircraft systems' but I'd prefer to see a concrete observation/metric.
Other than the above, I've noticed some typos here and there and some words that may have appeared due to internal paper revisions. Please check.
Author Response
Comment 1:
In this sense, I am missing the most notable finding in the summary section. For example, a quantified metric or an observation that was or was not expected before the analysis took place. I am sure that 'The results of this work contribute to a better understanding of the electrical power requirements of aircraft systems' but I'd prefer to see a concrete observation/metric.
Response 1:
Thank you for this suggestion. We have added a conclusion section on pages 38-39, where we summarize the key findings, including specific metrics and observations drawn from the analysis.
Comment 2:
Other than the above, I've noticed some typos here and there and some words that may have appeared due to internal paper revisions. Please check.
Response 2:
I have reviewed the manuscript and corrected several typographical errors. If there are additional issues that I may have overlooked, please feel free to point them out.
Author Response File: Author Response.pdf
