The Impact of Surrogate Models on the Multi-Objective Optimization of Pump-As-Turbine (PAT)

Round 1

Reviewer 1 Report

The authors are suggested to re-edit the manuscript and submit it again for the review. The manuscript is full of editing, typographical and simple grammatical mistakes that are really irritating.

Author Response

Thank you very much for your comments. It have help improve the manuscript. Find attached responds to your comments.

Thank you. 

Author Response File: Author Response.docx

Reviewer 2 Report

This article is about the study of the performance improvement of a PAT by performing numerical simulations and machine learning algorithms. It is an interesting study showing the value of the applied algorithms to find the best solution in multi-objectives and multi-variables problems. Furthermore, the achieved results are valuable for the improvement of the machine design to get better performances.

However, the article presents several issues that must be addressed and revised before publication.

1. The paper requires proof-reading. The whole text is globally understandable, but it presents several major flaws in the English grammar and in the structure of the sentences. Examples are in lines 15-22,52-56, 90-92, 209-210, etc. Same thing for typos and wording: Line 114: turbine pump? Line 154: number of grid number?, line 615, etc.
2. Line 286 has a formatting problem.
3. The article is redundant in defining the operating conditions: the three tested OP are defined many times and it is not necessary for the comprehension of the performed work.
4. There is a problem with the figures numbers after section 4.4 (repeated numbers).
5. Line 43: you cite the importance of pumped-storage HPP, but PATs don't have the major role in this kind of HPP. A reference to large scale machine should be included.
6. More examples of PAT studies should be added, for instance: Morabito et al. https://doi.org/10.1016/j.apenergy.2019.03.018 and Delgado et al. 10.5075/epfl-thesis-9036
7. Lines 77-78 this applies for all hydraulic machines, not only for PATs.
8. In Qd, d should be a subscript. Please, change it through all the article and define Qd (equation to compute it).
9. The mesh should be detailed and information on the meshing for each component should be provided, such as number of nodes, number of element, type of elements, etc.
10. You define the Objective Function as the sum of the efficiency for the 3 OP, have you actually use this function in your algorithm? As in Table 3, it seems you always referred to the optimization of each operating condition and not to the sum of the three.
11. Please, define all variables in the equations. For instance, in eq.2, eq.4 and eq.6.
12. From line 345: please consider putting the coding in an Annex.
13. Are the data training the algorithms validated by experimental results? This should be mentioned. If not, a sensitivity analysis should be performed to validate the CFD results.
14. In Fig. 10, it is clear that your optimization problem isn't convex. A clarification on how did you deal with this matter should be added.
15. Table 5, 6, 7: All acronyms should be defined.
16. Table 8 is hard to understand, please improve it.
17. In table 3, you listed the 50 training operating conditions, what about the testing operating condition?

Author Response

Thank you very much for your comments. Please find attached responds to your comments.

 

Thank You.

Author Response File: Author Response.docx

Reviewer 3 Report

The authors present a research in which a pump-as-turbine problem is considere, from the standpoint of geometrical design optimization. The problem is interesting, it has a reasonably high impact on day-to-day management of energy resources, and it fits the scope of the Journal...but, in opinion of this reviewer, it requires such a deep reconsideration. Please account for the following tips:

• A deep English editing. Starting from what I guess is a typo in the title, the  structure, sentences, paragraphs and general style should be reconsidered. Otherwise, the review process gets stopped because of the English editing/correction/suggestion and can hardly be focused in the scientific and technical content.
• Simplify unnecessarily long sentences and paragraphs.
• Remove unnecessary information and rationale, and focus in those points that might help potential readers to follow the research results.
• Set clearly the focus of the paper. Otherwise it might seem that it is out of focus with respect to the general scope of the Journal.
• Set clearly the objective of the paper, preferably towards the end of the Introduction.
• Set the whole context of the paper in its connection and importance with clean resources.

 

Author Response

Thank you very much for your comments. Please find attached responds documents to your comments.

 

Thank You.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors are greatly appreciated for their effort in re-editing the manuscript. The methods are well presented in the manuscript. However, in a new section, the authors are recommended to avoid the use of abbreviated terms only. Please use the full form rather than the abbreviated form when first use at a new section; it will improve the readability of the manuscript for the general readers. Moreover, some issues should be clarified before further proceed, and they are listed below. 

1. The authors argued that the present study focused on the investigation of the impact of surrogate models on multi-objective optimization of PAT. Moreover, they also mentioned that surrogate models have been successfully employed for pump performance optimization, however, its influence on the prediction of PAT has not been extensively studied (at line 157, 158). But the results presented here in this study are on the pump, so far. Please justify.      
2. The experimental results of the pump performance should be introduced. 
3. As this study involved in PAT optimization, the authors should present some results when the pump would use as a turbine, ie. turbine performance characteristics. 
          

Author Response

Hello.

The attached documents is a response to the reviewers comments

 

Thank You.

Author Response File: Author Response.docx

Reviewer 2 Report

Thanks for the modifications to your manuscript, it has been clearly improved.

However, here some further comments that should be addressed before publication:

1. Line 43, I would avoid to say that these technologies are undoubtedly the best solution for the ecological problems. This is not the key advantage of hydropower and you don't perform any ecological study in your manuscript.
2. Line 229-230: what are the boundary conditions for the flow rate? You mention it but you don't give any value. Did you set 1atm static pressure at both inlet and outlet section?
3. Line 440: nice the explanation with the Charles Darwin theory, but you should prove that your algorithm can mathematically solve this no-convex problem. For instance, have you done any effort in trying to convexify your problem? Did you try to minimize 1-eta instead maximizing eta?  
4. There is a problem with the caption of Table 7. Furthermore, in line 504 you call Table 7 the table that should be Table 9.
5. English can still be improved, there are sporadic errors and typos.  

Author Response

Hello

Find an attached documents which is response to the reviewers comments.

 

Thank You.

Author Response File: Author Response.docx

Reviewer 3 Report

The Authors have conducted a noticeable effort to enhance the paper. However, there still remain some flaws that, in opinion of this reviewer, should be improved:

. Why the Authors refuse to state clearly the Objective of the paper? The objective is stated (I shall say somewhat hidden) at line 115 in the revised version of the manuscript, while the introduction itself unfolds up to line 166. When the reader reaches that point, it is like the main objective is long forgotten. Why not use an Introduction structure in which the presentation of facts (background research, works previously conducted and gaps) leads to a simple exposition of the objective (or in other words, what Authors are coming up with) at the end of it?

-. The Conclusion is essentially the same as in the older version. In turn, regarding that he objective of the paper is "...to find a suitable computationally cost effective and less complex surrogate model to optimize the performance of PAT at design and off-design conditions", how do the Authors think the conclusion relates with that objective (thinking for example in terms of a researcher taking their conclusions as the starting point for a new research).

-. This reviewer considers that the answer to Comment 6 in the cover letter provided by the Authors, is not enough to set the importance of the research in the context of clean resources (even if they have modified the first sentence in the introduction to focus the research from a point of view other than the greenhouse effect. In fact, the focus remains the same, fortunately)

Author Response

Hello

Find attached documents which response to the reviewers comments.

Thank You.

Author Response File: Author Response.docx

Round 3

Reviewer 3 Report

Thanks for the answers. English style should be revised before proceeding to publication if any.