A MINLP Model for Optimal Localization of Pumps as Turbines in Water Distribution Systems Considering Power Generation Constraints
, Dong Quoc Vu 3, Bui Manh Cuong 4, Vu Phi Tuyen 5 and Pu Li 6,*Round 1
Reviewer 1 Report
The paper describes a numerical method to optimize the instalaltion of energy recovering systems in water distribution networks, with validations and study cases.
The manuscript is in general clear. However, I think that it is more suitable to be published as a study case rather than a scientific paper, because there are not new scientific information that have been discovered and presented.
The introduction should be better organized, and literature references should be described in a more ordered way, for example subdividing them into subtopics. Results should be better generalized and practical suggestions for the implementation should be described.
Some sentences are not clear. Units after equations should be specified, as well as the numerical values should be justified and included.
See the attach for my comments.
Therefore, I suggest a major revision.
Comments for author File: 
Comments.pdf
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
The research ideea to use pumps as turbines and thus recover energy is interesting. A similar ideea was used with succes in storing energy lost during braking in a hydraulic system.
The structure of the paper is good, the red line of the paper is clear.
Line 160 +: the relation between the position of a PAT and the optimisation criteria is not enough detailed.
Line 189+: explain if between the constraints there is a relation and/or a priority
line 372+: explain how do you model the leakage; describe the causes of leakage; is it enough to introduce a PAT so that leakages stop?
Line 446+: describe the experimental setup for the second case study; are the data coming from real-time data aquisition or are they statistically computed data?
MINLP is not suited for a keyword
Please pay attention to the line spacing. Lines 40 - 159 and 257 - 269 have a different spacing than the rest of the document.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The Authors addressed most of my comments. My last revision suggestions/improvements are the followings.
1) I suggest to specify that the
Hazen-Williams equations are used for the head loss calculation.
2) A notation list is highly recommended, considering the large number of used variables.
3) In the Conclusions, quantitative values should be included. For example: by using your new method, how much energy can you gain with respect to other methods?
Author Response
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Author Response File: Author Response.pdf
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
The reviewer cannot see significant novelty of the article, but the authors have done application oriented study of the optimal localisation of PATs. In addition, it is hard to grasp the content because of the way it is presented. Some parts of the article are unnecessarily large. For instance, the introduction section can be significantly reduced by focusing more on relevant topics. In some parts, it is difficult to distinguish between the authors´ contribution and work of others, for example in case study 1.
The reviewer suggests to change heading of Section 2 from "
A New MINLP Model for Optimal PAT Localization
to "Problem Formulation for Optimal PAT Localization".
A couple of key questions:
- Why is it necessary to conduct two case studies? How do you compare the performance of your model in the case studies and why. For instance, your case study 1 gave similar results as what is reported in the literature, while case study to is different. Is it due to the type of the problem?
- Can you clearly state the considered scenarios at the beginning av Section 3? Inform why the scenarios are considered.
Please add a space between a value and its unit. For instance, 10l/s is difficult to see whether it is 10 l/s or 101/s. 0.5 kW, NOT 0.5kW.
Check also unnecessary expressions and sentences from the template (line 493 - 497).
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
This paper presents a MINLP model to determine the best location for Pumps Working as Turbines (PAT) for reducing the pressure in water distribution systems (WDS). The novelty of the model lies in the introduction of a minimum available power threshold for selecting the branches where the PAT should be installed.
Overall, the document is well written and easy to read. There are, however, some problems with the presentation of equations (2)-(5) and (10)-(11), which prevent their understanding.
Furthermore, the authors claim that the objective function is formulated to maximize the power generated by PATs AND decrease the system pressures. With the presented objective function, only the first claim is correct, being the second just an obvious consequence of using PAT in the system.
Finally, the formulation of the model would be easier if the indices and variables were clearly formulated at the beginning of section 2.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
- Introduction: The authors address "leakage". This is reasonable as long as pressure release valves (which open to the environment thus causing leakage) will be replaced. Only then the avoidance of "leakage" makes sense.
- Pressure reduction valves do NOT cause leakage, but only "destroy" energy, i.e dissipate energy. Authors must make this clear in the introduction.
- In both cases the limiting value is the permissible pressure in the WDS. This boundary value is crucial for any system design. Energy recovery is nice and reasonable and most valuable! But always with the absolutely predominant aim to achieve the practically relevant system pressure. The authors must adress this in the introduction and also in the case studies (see below).
- There is no need to cite a source for such a basic value as pressure drop over a PAT (p.4, line 188).
- In formulae 2,3,4,5 the format must be corrected.
- p.5, line 206: The authors mean "static pressure" and "total head". Otherwise the sentence does not make sense.
- p.6, line 229: skip "is a big M number, which"
- p.6, line 245: What do the authors want to say with: "...made an experiment method instead of proposing constraints...
- p.8 (and the following pages): What is the unit value of "demand pattern"? m3/s?
- p.8. line 304: head of reservoir: Is this the geodetic head? Above which reference level?
- p.14: line 438 - 444: ... excessive pressure is 1269.20 m,..., increasing 150.7. Which pressure does increase and why? Where do these enormous pressures come from if the "head" (see above) is only 55 m? Water hammer?
- p.15, table 5: the "excessive pressures" lie between 2604.3 m and 1259.5 m. These are 260 bar and 126 bar! What does the word "excessive" mean? What is the system pressure in the WDS? Is the piping designed for these enormous pressures?! This would be lost unpractical and unreasonable.
- p.16, figure 11: The average power is approx. 25 - 30 kW, the max. power 70 - 80 kW. But the system pressure (cf. tab.5) is enormous. Especially for such small pumps. The pressure level rather calls for Pelton turbines, but with only 30 kW? This would be most ridiculous and impractical. Must be clarified!
- p.17: Paragraphs Funding and Acknowledgements have not been changed but the template text has been kept.
- Due to practical weaknesses the theoretically fine paper looses its sense and value. The authors developed and described a highly complicated WDS network, that is not easily treated. With very very (!) accurate English proof reading and major improvements with respect to practical applicability the paper will be worth publishing.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have properly addressed my concerns of the first review. My remaining concern can be poor readability of text and numbers in some figures such as Fig. 10, 11, 12 and many others. In some cases, this can be improved by enlarging the figures and make max. use of the space to the right and left of the figures.
