A Monthly Hydropower Scheduling Model of Cascaded Reservoirs with the Zoutendijk Method

Round 1

Reviewer 1 Report

This work presents the application of the so-called Zoutendijk method to the optimization of cascade hydropower systems. This optimization scheme is not a population-based approach and is typically used for multiobjective optimization. The authors have shown that the Zoutendijk method in the contest of hydropower optimization is reliable. Despite the importance of the subject, this work has some important flaws. Firstly, the problem should be better described: multi-object optimization with hydropower versus firm power. Secondly, the literature review must be extended both regarding hydropower and optimization schemes. Thirdly, a discussion section should be included. Finally by adopting W1>>W2 the authors reduce the multiobjective optimization to a single-objective optimization. This should be underlined.

Other comments

It is not clear whether the reservoirs taken into account are connected or not. Could the author specify that? Do they belong to the same hydropower system? If not, is the author performing 6 interdependent optimization? If yes, could the authors provide a scheme of the system with rivers, hydropower connections, hydrower location. See as an illustrative example the Figure 7 in “A dual-layer MPI continuous large-scale hydrological model including Human Systems”, EMS 2021. In the latter case how the water is transferred from a reservoir to another.

Is the final volume of the reservoir fixed? Due to the fact that the aim of the optimization process is to maximize the energy production (or in many cases of the revenue), I expect the reservoir to be empty (or at its minimum volume) at the end of the optimization period if no limits are imposed. These limits could be seasonal regulation constraints. See Forecast-informed hydropower optimization at long and short-time scales for a multiple dam network, Renewable Sustainable Energy 2020. Could the author give some comments on this issue related to the optimization? It seems that the authors have imposed that the reservoir initial level has to coincide with the reservoir final level. If this is the case, this must be better elucidated in the present work.
Please add some references about hydropower at line 33: Hydropower for sustainable water and energy development, Renew Sustain Energy Rev 2010; Energy storage and its use with intermittent renewable energy. IEEE Trans. Energy Convers. 19 (2), 441–448; Detailed simulation of storage hydropower systems in large Alpine watersheds 2021 JOH.
What about revenue optimization? See ad refer for example to “Short-term hydropower optimization driven by innovative time-adapting econometric model” and “Optimizing profits from hydroelectricity production, Computers & Operations Research 2009”
Line 87: refer to “Forecast-informed hydropower optimization at long and short-time scales for a multiple dam network, Renewable Sustainable Energy 2020.” This, in my opinion, could support your statement about “ The method, however, has not been reported yet applied to a mid/long-term optimal scheduling of cascaded hydroplants”

Could the authors better specify the sentence “where, W1 and W2 are weights with W1>>W2 to prioritize the firm power output (F) over the energy production”. It is not clear the difference between “ firm power output” and “energy production”.
All the equations are not correctly inserted in the text. I think there is some problem with the indent.
How do the results change if W1 and W2 changes? What about adding some comments (and maybe results).

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

After reading the manuscript, I think it will need major revision before it is published in the Energies journal. The results of the research and the general methodology were correctly described, and the objectives of this research are interesting and can be applied in practice.

The big drawback is the lack of discussion of the results, as well as the slight reference to the current knowledge in the topic (12 literature items). I would like to refer to international research on a similar topic, as well as a broader interpretation and statistical analysis of the results. In the context of the Introduction, the Authors use a lot of abbreviations - I would ask for a list of them.

 The general description of the results is good, however it would need to be clarified, e.g .:
- Lines 284-287 - what is the exact measure of fit for the charts described? No values ​​were specified.
- Lines 296-300 - what does this curve shape result from? How can this be interpreted?
- Lines 303-309 - in which months is the dry and wet season? There is also no reference to the literature in the context of the described dependencies. I think it is worth considering the description of the research area in addition to the list of objects itself - in this context, it would be useful, among others hydrological and climatic characteristics, which is also important when interpreting the results.

I think that the presented equations and systems of equations need to be sorted out. Consider listing the symbols used with the units so that the reader can more easily analyze the formulas used and interpret the case studies described.

 It is also worth considering the issue of adding a map with the location of the described case studies, because in their current shape they are detached from the geographical space, which significantly hinders the reception of the presented content.

 In terms of language, I have doubts about the use of the term "hydroplants" - in English, we use the terms "hydropower plants" or "hydroelectric power plants" for this type of facility. I would ask you to consider changing this wording.

 In addition, the article has not been prepared in accordance with the requirements of the journal, i.e .:
- the method of citation is different from that adopted in the MDPI (numbers in square brackets should be used, not the names of the authors and the year),
- neither of the sections after the Conclusions has been supplemented, and this is extremely important in terms of the division of tasks between the Authors, co-financing of publications, potential conflicts of interest, data availability or ethical issues or obtaining consent for research,
- the reference description was prepared contrary to the one adopted in the MDPI; additionally, I would like to ask you to add DOI numbers to make it easier to identify articles and to correctly index them in scientific databases.

 Good luck in making the corrections and all the best for your further research.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

There are still some problem with the bibliography. Please check the correct order for name and surname. It is Avesani et al  not Diego et al.

Reviewer 2 Report

The Authors have complied with most of my comments, for which I am grateful. In my opinion, the cited literature could be even more, but in fact the issue has been expanded quite significantly (from 13 to 21 publications in the References). Certainly, the sections after the main text (from "Supplementary Materials" to "Conflict of Interest") should be completed - it still has not been done despite my previous recommendation. Please additionally verify the way of writing the bibliography, because it does not meet the requirements of the MDPI publishing house. In summary, the article can be published after the above minor corrections have been made. I wish the Authors all the best on their further scientific path.