Expanding Electric and Vehicle-Based Solar Transit Options with Breakthrough Vehicular Efficiencies

Round 1

Reviewer 1 Report (New Reviewer)

Comments and Suggestions for Authors This paper evaluates the impact of a novel design based on ground effect on electric vehicles. The proposed design has been published recently in several journals and reports. The contribution of this paper is primarily the potential benefits of implementing EVs, supported by CFD simulation results. In general, this paper has an interesting subject within the journal's scope and presents publishable results. There are some issues in the figures presentation and redaction that need to be improved. Most of the references are recent and adequate, but need to be corrected in the format ([44]), and to replace one of them with published reports ([30]). In Table 1, for data presentation consistency with [21], replace <5% in Inertia/GEFT/Highway with 0-5%. Line 105: “his paper expands upon the January 2025 paper by going into detail of how a 50% reduction”. I recommend replacing “January 2025” with its reference number. Line 119. Remove “See Figure 10 for pressure scale” since it is well discussed in page 13.  Same for Figure 2. l. 147. I recommend not including paper titles and just including reference number [24]. l. 157. “L/D is a measurement of energy efficiency.” Should be relocated to the previous paragraph. l. 160. Figures and equation presentation need improving. For example, in l. 165-168: “Equation 1 provides the resistance force. Multiplying Equation 1 by the velocity (U) yields the power per planform area to sustain flight. Further multiplication by planform area, A, results in Equation 2, which relates Power, in units of watts, to L/D .” Can be expressed as: Multiplying (1) by the velocity (U)  yields the power per planform area (A) to sustain flight. Then,  Power is defined as 𝑃𝑜𝑤𝑒𝑟 =𝑈𝐴𝑤𝐴/ (𝐿/𝐷)” l. 169. “A series of papers have identified the”; I recommend including the papers' references. I recommend editing Figure 3 for better understanding of the dimensions. Also, in l.228-233 are described 2 dimensions for airfoils but Fig. 3 has 3 airfoils. l. 243; this sentence feels misplaced; it should be relocated at the end of the section, and the discussion needs to be extended. Figure 9. Pressure scale for this figure should be included (not referred to another figure). l. 534. “Sunny” there are several errors of unnecessary use of uppercase letters (“Digital” in l. 408, “Pressures” in l. 566). Does the “Source” term in l. 402 requires uppercase?. Some references are incomplete ([27]) or not in MDPI format ([2],[10],[23], without bold in year). I recommend including only published documents ([30]).

Author Response

Thank you for your review. Please see the attached letter for our response and revisions. 

Author Response File: Author Response.pdf

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

1. The abstract section could have more numerical results.
2. Key simulation parameters (mesh independence, turbulence model, convergence criteria) are insufficiently detailed.
3. The manuscript is excessively long (33+ pages) and repetitive, especially in the Introduction and Discussion sections.
4. It would be better to add a comparison table. Please see and cite this paper: https://doi.org/10.3390/electronics14132514.
5. The equations (1) and (2) for aerodynamic resistance and power are correct in form but lack numerical examples tied to experimental prototypes.
6. Define abbreviations upon first use (e.g., TR, CL, CD).

Author Response

Thank you for your review. Please see the attached letter for our response and revisions. Please note the final section which details general major revisions to the paper was well as the direct responses to your review. 

Author Response File: Author Response.pdf

Reviewer 3 Report (New Reviewer)

Comments and Suggestions for Authors

The authors of the paper titled Expanding Electric and Vehicle-Based Solar Transit Options  with Breakthrough Vehicular Efficiencies have contributed a comprehensive study that enhances the understanding of the characteristics of various vehicle types. The paper is thoroughly prepared, featuring detailed descriptions and numerous illustrations. Ground-effect flight transit (GEFT) represents a highly significant and contemporary topic warranting further investigation. However, notwithstanding these merits, the paper exhibits several notable shortcomings.

Major comments

1. A large part of the paper deals with numerical testing, yet there is not a single word about the model, domain, methods, boundary conditions, etc.
2. The three Principles of physics (line 146) may cause confusion with similar concepts that have long existed. To make it completely clear what the author intends to say, it should be explained better (ref [24]). Perhaps the explanation in lines 199–205 is sufficient, but it is placed incorrectly.
3. The GEFT is excellently addressed and the effects on different parameters are provided. This is the forte of this paper.
4. The paper is too extensive, with too many pages; it should be reread and reorganized.
5. There are too many self-citations. For example, the first reference is a paper by the same authors that has not yet completed the review process.
6. Is the class 8 tractor trailer an adequate vehicle to be used for comparison with the GEFT (Table 1)? Later, everything is compared to trains.
7. Lines 184–188: OK, no experiment, but why include explanations?
8. The outputs of the numerical testing must have completely clear legends. Pressure (m²/s²) — does this refer to pressure or specific energy?
9. The Discussion section is well written, and then suddenly the topic shifts to photovoltaics. Should that be part of the discussion? Again, frequent citation of own paper [1].

Minor comments

1. SI units should be consistently used. The present form looks confusing at times (e.g., page 26: m/s²*kg/m²) — why the asterisk? Check all paper.
2. Lines 538–538: “Therefore, the thrust power required to support the towed platform is [9.8 m/s² * 2.25 538 kg/m² * 40 m/s / 20] = 44.1 W/m².” Is this an equation? Again, ensure SI consistency.
3. In the formula on lines 157–160, as previously mentioned, it is unclear whether “wa” are two variables or an index. All formulas need to be checked.
4. All figures must have legends fully describing everything shown (e.g., Figures 5 and 6 — description of lines and variables on the ordinate).
5. The same applies to graphs; they must have labeled abscissa and ordinate axes.
6. “Low carbon” and “low emission” are listed as keywords, but apart from general comments there are no other indicators of these in the paper.
7. The sentence in lines 43–45 is unclear (“safety and efficiency are enabled”).
8. If figures are taken from published papers (even from the authors’ own), they should be cited.
9. Line 170: typing error.
10. Why is bold text used in lines 165–168?
11. Line 167: in Equation (2), not “in equation 2…”.
12. Table 2 — some elements are centered, some are not; make alignment uniform.
13. Figure 6: “ducted fan power (m⁴/s²)” seems inconsistent.
14. Figure 7 has a, b, c, d labeling, while Figure 8 does not — ensure consistency throughout.
15. Why is Figure 9 not presented alongside Figure 4 to make the comparison clear?
16. Lines 331–333 — the figure caption should be on the same page as the figure itself.
17. Why does the author change the color scale between figures? Sometimes shades of blue, sometimes full RGB…

The paper is, for the most part, an excellent scientific work, but occasionally written as if the author intended to produce a review article. It is quite difficult to read and follow. Simplification and reduction of the paper’s scope are recommended.

The reviewer recommends re-reading and checking everything, reorganizing where needed for greater clarity. Major revision is suggested, after which the author may resubmit the paper for review if the raised issues are properly addressed.

Author Response

Thank you for your review. Please see the attached letter for our response and revisions. Please note the final section which details general major revisions to the paper was well as the direct responses to your review. 

Author Response File: Author Response.pdf

Reviewer 4 Report (New Reviewer)

Comments and Suggestions for Authors

In this paper, the authors performed a CFD analysis to investigate approaches to overcoming energy loss due to leading-edge stagnation point and rolling losses. The topic aligns with the scope of the journal. However, the paper requires substantial revisions before publication, particularly regarding experimental validation, clarity of presentation. 

1. This paper lacks experimental validation. A scaled wind tunnel experiment is suggested to validate CFD predictions.

2. The aerodynamic lift was considered as an approach to reducing drag. However, generating lift also requires energy. How do the authors optimize the design?

3. Current title, abstract, and keywords do not indicate the main body and findings of the paper. Those should be rewritten.

4. Please provide the details about the OpenFoam simulation, including the turbulence model used, the mesh resolution, and boundary condition specifics.

Author Response

Thank you for your review. Please see the attached letter for our response and revisions. Please note the final section which details general major revisions to the paper was well as the direct responses to your review. 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report (New Reviewer)

Comments and Suggestions for Authors

The authors readdressed all issues.

Reviewer 4 Report (New Reviewer)

Comments and Suggestions for Authors

The authors have addressed the reviewer's comments. 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

• Nomenclature must be added to the manuscript.
• Abbreviation list should be included.
• The introduction section must be supported with other recently studies of passive flow control techniques (external devices) in vehicle applications to illustrate the importance of this study (see https://doi.org/10.37934/cfdl.15.8.7394).
• Further validation of obtained results should be added to strength and support the findings of this research.
• The claims regarding efficiency improvements and energy savings should be presented with sufficient numerical evidence, modeling, or experimental validation.
• To proposed concepts, advanced beyond the current state-of-the-art, the comparison with existing electric and solar vehicle technologies needs to be discussed.
• The infrastructure requirements, cost implications, or large-scale implementation challenges should be considered.
• Real-world factors such as solar intermittency, weather variability, and grid integration issues should be analyzed in more detail.

Comments on the Quality of English Language

• The language of the paper needs to be written in a more technical form to clearly convey what has been done.

Author Response

Please See attachment.

The attached letter has a general response to the major changes and added sections as well as slight reorganization, followed by a section of responses for each of the reviewers.

Thank you for your time and consideration with your reviews.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Aerodynamic resistance from Equation (1) is given as w/(L/D). Though dimensionally correct, the solution that it is "in the same units as weight" is too general. A more precise dimensional solution is required to provide uniformity.

Equation (2) for power per planform area Uw/(L/DA)) seems dimensionally ambiguous. Since said W is the weight, the final units are worth explaining. Describe the derivation in steps.

The values for drag coefficients given in Table 3 are then declared to be "corrected by a factor of about 10." This is inexact and destroys the confidence in the outcome. A precise mathematical description for the correction is required.

Table 5 combines units (kg/m/s² and lb/ft) in the "Load" row. The variation creates ambiguity in interpreting the values that should be removed in favor of use of a single consistent system of units.

The calculation to obtain the conversion from 2000 W/m² dynamic pressure to 100 W/m² drag given that L/D = 20 is partial. A more precise mathematical prescription is needed.

The part that goes with Figure 11 has the power calculation denominator as [20 / (9.8 m/s² × 2.25 kg/m² × 40 m/s)]. This is dimensionally inconsistent. Check this expression again to give it physical correctness.

The widely used Thickness Ratio (TR) values (0.05, 0.1) are employed widely, yet no equation that incorporates TR to lift and drag is depicted. Including direct ties or references will consolidate the mathematical basis.

It is discussed qualitatively (Figure 2), while analysis of pressure distribution is absent in the form of strict formulation as surface-integral. A quantitative demonstration is proposed.

It is listed in Table 4 that L/D ratios are as high as 85, which is extremely high in comparison to available aerodynamic references. There is suspicion about potential computational over-estimation or scaling.
In recent years, several studies have applied metaheuristic algorithms for optimization in related engineering domains (see for example: https://doi.org/10.1007/s00521-024-10346-4 ). A reference in the introduction to that type of work would give background enrichment as well as buttress the paper's novelty position.

The assertion that power from the Sun is "up to twice that required for direct solar powering of cars at 90 mph" is mathematically baseless. Provided with a clear numeric derivation. This is strengthened in this version through setting the study in the wider background of previous studies in optimization and efficiency in vehicular contexts. The motivation is again apparent but the connection to the wider literature is less developed.

 

Author Response

Please See attachment.

The attached letter has a general response to the major changes and added sections as well as slight reorganization, followed by a section of responses for each of the reviewers.

Thank you for your time and consideration with your reviews.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

In my opinion, the assumptions regarding the following are incorrect:

• solar radiation irradiance,
• the achievable conversion efficiency of PV panels,
• the speed of the vehicles analysed.

 

The article also contains imprecise wording, e.g. low pressure (no range or numerical value given – line 167).

 

The analysis cannot be based on average daily values of solar radiation irradiance. Firstly, the vehicles analysed, powered by energy obtained from PV, cannot move at night. The authors also do not take into account possible very rapid changes in irradiance related to weather conditions.

Secondly, PV panels mounted on vehicles will not be optimally oriented (angle of inclination and geographical directions) due to aerodynamic constraints.

Thirdly, during vehicle movement, the position of the PV panels relative to geographical directions will change. This is very important when estimating the potential amount of energy generated.

Fourth, it is impossible to achieve the energy efficiency of photovoltaic panels mounted on vehicles at the level indicated in Table 2.

Fifthly, trucks or golf carts do not travel at a speed of 40 m/s.

Sixthly, the authors ignore the problem of mechanical strength of lightweight structures with PV panels at a speed of 40 m/s.

 

In my opinion, the assumptions made by the authors are impossible to meet in real conditions due to physical, material and legal limitations (maximum permissible speed of vehicles on public roads).

 

The editorial quality of the article is also poor (size and placement of charts, lack of scale), as is the division of content between pages and the placement of chapter titles on the last line of the page.

Author Response

Please See attachment.

The attached letter has a general response to the major changes and added sections as well as slight reorganization, followed by a section of responses for each of the reviewers.

Thank you for your time and consideration with your reviews.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Good work this time after the revision.

Reviewer 3 Report

Comments and Suggestions for Authors

I recommend rejecting the article.

In my opinion, the changes are insufficient.

The article has serious flaws and is based on incorrect assumptions.

I reiterate that lorries do not travel at the assumed speed of 40 m/s. The maximum permissible speeds are significantly lower.

Furthermore, the designs described do not make sense in the case of trains due to their electric traction power supply.

It is therefore possible to install PV systems next to railway lines. This will be much cheaper, more efficient and will generate many times more energy.

The assumptions, content and conclusions are not consistent with each other.